CA1252579A - Method for dicing a semiconductor wafer - Google Patents

Abstract

Abstract of the Disclosure A method for dicing a semiconductor wafer to dices which comprises:
(a) placing and fixing the wafer on a dicing film which comprises a base film permeable to ultraviolet light and a layer of a pressure sensitive adhesive formed on one side of the base film to fix thereon the wafer, the adhesive comprising:
(i) at least one elastic Polymer selected from the group con-sisting of polyacrylic acid ester copolymers and saturated copolyesters;
(ii) an ultraviolet light polymerizable acrylic acid ester having not less than two acryloyl or methacryloyl groups in the molecule and having a molecular weight of not more than about 1000, in amounts of about 15-200 parts by weight in relation to 100 parts by weight of the elastic polymer; and (iii) a photopolymerization initiator in a sufficient amount to induce the photopolymerization of the ultraviolet light polyme-rizable acrylic acid ester;
(b) dicing the wafer;
(c) applying the ultraviolet light to the other side of the dicing film to substantially reduce the adhesive force of the dicing film; and then (d) removing the resultant dices from the dicing film.

Description

7~

This application is closely related to Application Serial No. 501,750 filed February 13, 1986.
The present invention relates to a method for dicing a semiconductor wafer to dices wherein the wafer is at first fixed on a pressuresensitive adhesive film for dicing, and ater ~ha dicing the adhesive force is reduced by the application tllerato of ultraviolet light so that the dice is readily removable from the dicing film.
As is well known a dicing process is included in the production of integrated circuits. In the process, a semi-condu~tor wafer is placed and fixed on a pressure sensitive adllesive film called a dicing film, cut to small pieces or dices of a predetermined size, and then the dice is removed or picked up from the film. Therefore, it is desirable that the semiconductor wafer, for instrance, a silicon wafer, is initially adhered onto the dicing film with a relatively st~ong adhesive force so as to be precisely diced to dices of ~ predetermined size, whereas after the dicing the resultant dica is loosely adhered onto the film so as to be readily removable therefrom.
For exemplification only, it is desired that the dicing film initially has an adhesive force of about 100-800 g/25 mm so that the wafer is precisely diced to dices, but after the dicing the film has a reduced adhesive force of several tens grams/25 mm or less for the readily removal of the resultant dices. However, no such a pressure sensitive adhesive which ~s ~

has a sub3tantially reducible adhesive force so as to be suitably and practically usable for dicing a semiconductor wafer has been known up to today.
On the other hand, a photocurable adhesive is already S knOlYn IYhiCh i3 curable by the application thereto of the ultra violet light to develop the adhesive force designed. The photo-cllrable aAhesive is usually composed of a photopolymerizable oligomer, a photopolymerizable monomer, a photopolYmerization initiator and other additives, and is rapidly cured by the application thereto of the ultraviolet light. It must be noted, however, that the ultraviolet light is applied to the adhesive to Gomplete the adhesion.
rhe present inventors have made an intensive investiga-tion of a pressure sensitive adhesive for use in dicing a semi-1~ eonductor wafer, and found out unexpectsdly that a photosensi-tive adhesive mainly composed of a certain elastic polymer as a base resin, a photopolymerizable acrylic acid ester and a photopolymerization initiator is substantially reducible in the adhesive force by the application thereto of the ultraviolet light. After a further investigation based on the above finding, the inventors have found out that a pressure sensitive adhesive film composed of a photopermeable base film having on one side thereof such a layer of the pressure sensitive adhesive as above mentioned is capable of fixing thereon a semiconductor wafer with a sufficient adhesive force to make i-t possible for the wafer to be precisely diced, but loses its adhesive force by the irradiation of the ultraviolel light to the other side of the film so that the dice may be readily removed therefrom.
It is, therefore, an object of the invention to provide a method for dicing a semiconductor wafer in which the wafer is initially fixed on a pressure sensitive dicing film so that the wafer is precisely diced to small pieces or dices, and after the dicing, the film is substantially reduced in the adhesive force by the application thereto of the ultraviolet light so tllat the resultant dice is readily removed therefrom.
The method for dicing a semiconductor wafer according to the invention comprises:
(a) placing and fixing the wafer on a dicing film which comprises a base film permeable to ultraviolet light and a layer ~f a pressure sensitive adhesive formed on one side of the base film to fix thereon the wafer, the adhesive comprising :
(i) at least one elastic polymer selected from the group consisting of a polymer mainly composed of acrylic acid ester copolymers and a saturated copolyester mainly composed of a dibasic carboxylic acid and a dihydroxy alcohol, (ii) an ultraviolet light polymerizable acrylic acid ester having not less than two acryloyl or methacryloyl groups in the molecule and having

2~ a molecular weight of not more than about 1000, 7~

- ~ - 27571-6 in amounts of about 15-200 parts by weight in relation to 100 parts by weight of the elastic polymer;
~iii) a tackifier in amounts of about 10-200 parts by weight in relation to 100 parts by weight of the elastic polymer;
~iv) anhydrous silica powder in amounts of about 1-30 parts by weight in relation to 100 parts by weight of the elastic polymer; and ~v) a photopolymerization initiator in sufficient amounts 1~ to induce the photopolymerization of the ultraviolet light polymerizable acrylic acid ester;
~b) dicing the wafer;
~ c~ applying ultraviolet light to the other side of the ~i~ing ~ilm to substantially reduce the adhesive force of the dicing film; and ~d~ removing the resultant dice from the dicing film.
The dicing film used in the invention is composed o~ a base film which is permeable to the ultraviolet light ~n~ a layer of a pressure sensitive adhesive formed on one sid~ o~ the base film to fix thereon a semiconductor wafer.
~h~ pressure sensitive adhesive includes an elastic polymer as a main component, a photopolymerizable acrylic acid ester polymerizable by the application of ultraviolet light, a tackifier, anhydrous silica powder and a photopolymerization initiator.
A variety of pressure sensitive adhesive is already known, as described, for instance, in "Adhesive ~andhook", ~n~ ~d., editied by Japan AdhesivesAssociation, pp.398-414 (1980), . .

~ 7 ~

Nikkall Kogyo Shinbunsha. A typical pressure sensitive adhesive is composed of an elastic polymer as a ma;n compon~nt, a tacki-fier and a plasticizer soluble to the elastic polymer, and when desired, additional components such as an antioxidant, a filler and a colorant. According to the invention, however, lhe pressllre sensitive adhesive includes at least one specified polyMer as the elastic polymer selected from the group consist-in~ of a polymer mainly composed of acrylic acid esters and A
saturated copolyester mainly composed of dibasic carboxylic acids and dihydroxy alcohols.
The acrylic acid ester polymer as the elastic polymer in the pressure sensitive adhesive usable in the invention is already well known in the art, and is normally a copolymer of a~rylic acid ester components as main monomer components such 1~ as ethyl acrylate, butyl acrylate or 2-ethYlhexYI acrylate to form adhesive soft segments of a low glass transitlon tempera-ture in the polymer chain, and comonomer components such as vinyl acetate, acrylonitrile, styrene, methyl acrylate or methyl methacrylate to form cohesive hard segments of a hlgh glass transition temperature in the polymer chain. The elastic polymer may further include a third comonomer component having a functional group therein such as a carboxyl, a hydroxyl, an amide, a glycidyl or a hydroxyalkyl to improve the curability and/or the adhesion of the resultant polymer~ Examples of the '~S third comonomer are acrylic acid, methacrylic acid, itaconic acid, hydroxymethyl methacrylate, hydroxypropyl methacrylate, acryl amide or glycidyl methacrylate.
The saturated copolyester preferably usable as the elastic ~lolymer in the invention is per se also known, as described, for S installce, in ~Kogyo ~airyo (Industrial Materials)," Yol. 25, No 11, pp. 101-106 (197-7), and is a copolyester composed of a saturated dibasic carboxylic acid component and a saturated dihydroxy alcohol component, i.e., a glycol component. Hence, the copolyester has a low glass transition temperature. A mix-ture of an aromatic dibasic carboxylic acid and an aliphaticiiibssic carboxylic acid is, for example, preferably used as the dihasic. carboxylic acid component, while an aliphatic and/or an ~licyclic glycol is prefeably used as the glycol component.
In the invention, a copolyester is preferred which is 1~ composed of a dibasic carboxylic acid component of an aromatic ~iibasic eArboxylic acid and an aliphatic dibasic carboxylic acid in a ~olar ratio of the former to the latter of about 80/20 to ~0~80~ more preferably of àbout 70/30 to 50/SO, and a glycol oomponent, substantially in an equimolar ratio. In particular, '2~ terephthalic acid is preferred as the aromatic dibasic carboxy-lic acid, whereas sebacic acid and adipic acid are preferred as the aliphatic dibasic carboxylic acid, meanwhile ethylene glycol, 1,4-butanediol and propylene glycol are, for instance, preferred as the elYcol component, For the copolyester suitable '~ for use in the invention. Ilowever, the dibasic carboxylic acid ~ $7 ~

component may be in part displaced by a lribasic carboxylic acid, and the glycol may be replace(l by a Irihydroxy alcohol.
The pressure sensitive adhesive used in the invention includes a tackifier in the amounts of r~ 200 part~ by weight in relation to 100 parts by weight of Ihe elastic polymer, The tackifier usable in the adhesive in Ille invention is not restricted to a specified one, but any lackifier is usable which is known in the production of a con-ventional pressure sensitive adhesive.
la ~s examples only, there are mentioned as such a tackifier, for instance, xylene resins, rosins, polymeri2ed rosins, hydro-genaled rosins, rosin esters, terpene resins, terpene-phenol resins, petroleum resins, coumarone resins, styrene resins, alkylphenol resins and the like. The tackifier is preferably 1~ included in the adhesive in amounts of about ~a-lSa parts by wei~ht, in relation to 100 parts by weigt of the elastic polymer~

Ihe use of the tackifier is specially useFul when the copolyester is used as the elastic polymer in the adhesive~
'2~ hen the amount of the tackifier is less than aboul 10 parts by weight in relation to 100 parts by weigt of the etastic polymer, lhe resultant adhesive tends to have an insufficient adhesive force to fix a wafer for the precise dicing, whereas when Ihe amount of the Lackifier is more Ihan aboul 200 parls hy weighl, '2~r~ ltle result;lnt adtlesive is reducible in ~he adtlesive force only to an insufficient extent so that the resultant dice is nol readily removable from the dicing film after the dicing by the application of the ultraviolet light, but also the tackifier undesirably tends to migrate onto the dice.
In connection with the tackiness of the dicing film, it i~ preferable to corporate both the acrylic acid ester copolymer nnd the saturated copolyester into an adhesive composition as elast;c polymer copmponents, since such an adhesive has a pronouncedly large tackiness, but has substantially no tendency to migrate to dices. This dicing fiIm is especially suitable for industrial use in dicing.
The ultraviolet light polymerizable acrylic acid ester usable in the invention has two or more acryloyl or methacrYloYI
~roups in the molecule and a molecular weight of not more than 1~ about lOOO. Therefore, the acrylic acid ester usable in the invent;on includes, for instance, acrylates of polyhydroxy alr.ohols, such as ethylene glycol diacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate and dipentaerythritol hexaacrYIate, and methacry-lates of polyhydroxy alcohols, such as ethylene glycol dimetha-Grylate, 1,6-hexanediol dimethacrylate, trimethylolpropane trimethacrylate, tetramethylolmethane tetramethacrylate and dipentaerythritol pentamethacrylate~
The ultraviolet light photopolymerizable acrylic acid 2~ ester is included in the pressure sensitive adhesive in amounts ~5~

of about 15-200 parts by weight in relation to 100 parts by weight of the elastic polymer. When the photopolymerizable aGrylic acid ester is included in amounts less than about 15 p~rts by weight in relation to 100 parts by weight of the flStie polymer, the resultant adhesive is not substantiallY
reAIloible in the adhesive force by the application of the ltraviolet light thereto, thereby failing to provide a dicing film to permit the readily removal of dices after dicing of a wafer. Meanwhile when the photopolymerizable acrylic acid ester 1~ is included in amounts more than about 200 parts by weight, the adhesive undesirably tends to remain on the dice after the Ai~in~ of a IYafer, although the resultant adhesive is substan-tially reducible in the adhesive force by the application of the ultraviolet light~
1~ rhe pressure sensitive adhesive used in the invention further includes a photopolymerization initiator or photo-sellsitiæ.er, and in addition, may include, when desired, a polyMerization inhibitor. The initiator is included in the sdhesive to accerelate the polymerization of the photopoly-'2~ Merizable acrylic acid ester as stated hereinvefore, as is well known in the field of the photopolymerization~ Any known initiator is usable in the invention, for instance, benzoin ~Ikylethers such as benzoin methylether and benzoin isopropyl-etller, aromatic ketones and aromatic hydroxy ketones such as hen~oin, benzil and benzophenone.

~ he polymerization inhibitor is included in the adhesive, ~hen desired, to prevent the polymerization of the photopoly-merizable acrylic acid ester induced by an energy other than the ultraviolet light, for instance, thermal polymerization. ~Iso the inhibitor usable in the invention is not speGifically limited, and as an exemplification, picric acid, phenol, hydro-~uinone, hydroquinone monomethylether and the like are usable.
~ he amount of the initiator and the inhibitor used may be in ac.cordance with the amount in the conventional photopolyme-l(~ rization technology, respecitively, and hence the initiator isincorporated in the adhesive in amounts of about 0.1-30 parts by weight, and the inhibitor in amounts of about 0.1-1 parts by ei~ht, respectively, in relation to lQO parts by weight of the photopolymerizable acrylic acid ester, although aot limited to 1~ these exemplified ranges.
The pressure sensitive adhesive used in the invention may further contain therein a plasticizer such as a polybutene polymer and a mineral oil.
The dicing film used in the invention is composed of a ba~e film and a layer of the pressure sensitive adhesive as set forth above in solid. In the production of the dicing film, the pressure sensitive adhesive is aPplied preferably in a form of a liquid composition including an organic solvent on to one side of a base film, followed by drying the liquid composition `2~ to form a solid layer of the pressure sensitive adhesive on the hase film.
The liquid composition as above may be prepared, in prin-Giple, by dissolving in an organic solvent such as an aromatic lIydrocarbon~ an aliphatic ketone or a mixture of these, the ~bove mentioned elastic polymer, photopolymerizable acrylic acid e3ter~ a photopolymerization initiator, and when needed, further a~Aitives such as a tackifier, an inhibitor, a filler, an anti-oxidant and a colorant, each in amounts as stated hereinbefore, respectively, ~s the organic solvent is preferred in particular 1~ a mixture of toluene and methyl ethyl ketone, although not limited thereto. The liquid composition contains the elastic palymer preferably in amounts of about 10-50 % by weight based on the liquid adhesive so as to be easy in coating on a base fiIm and drYing to form a solid layer of the adhesive on the l~ hasc fiIm.
rhe Iiquid composition may be prepared in any conventional manner known in the field of adhesives. The elastic polymer and thc tackifier are usually available in the form of solution in ~rganic solvents. Therefore, it is convenient to PrePare the 7~ liquid composition, for example, by admixing the solutions of the elastic polymer and the tackifier together, adding to the solution the photopolymerizable acrylic acid ester and the ini-tiator, and when neccessary, other additives such as an inhibi-tor~ an antioxidant, a filler or an additional amount of an orgallic solvent.

As apparent, a liquid compposition on the market which includes polyacrylic acid esters as the elastic polymer is also usable for preparing a pressure sensitive adhesive used in the invention, since such a liquid resin composition is in many S r,ases a MixtUre of the elastic polymer with other additives such as a tackifier and a plasticizer dissolved in an organic s~lvent, although some of the liquid acrylic acid ester polymer ~omposition are found not to contain a tackifier and a plasti-cizer.
L~ When the liquid resin composition on the market is used for forming on a base film a solid layer of the preparation of the photopolymerizable pressure sensitive adhesive, the liquid ~a~pasition is mixed with the photopolymerizable acrylic acid ester and the initiator, and when desired, together with other lS additional components such as a polymerization inhibitor and an ar~anic solvent, in amounts as stated hereinbefore. depending upon the amount of the elastic polymer in the composition.
Nol~ever, it is preferred that the photopolymerizable acrylic acid ester is ~dmixed in amounts of about ~-60 parts by weight.
preferably about 5-20 parts by weight, with 100 parts by weight o~ the liquid resin composition.
~ he dicing film used in the invention may be prepared by forming a layer of the pressure sensitive adhesive as set forth hereinbefore on a base film permeable to the ultraviolet light, 2S which will now be described.

r~

Any resin film may be usable as the base film provided that the film is permeable or transparent to the ultraviolet light 3S well as the film has a strength sufficient to support a se~iconductor ~afer fixed thereon. The base film usable in the invention, therefore, includes films of polyvinyl chloride.
vinyl chloride-vinylidene Ghloride copolymer, vinyl chloride-vinYI acetate copolymer, vinyl chloride-acrylic acid copolymer.
polyvinylidene chloride, polyolefin such as polyethyleoe or polypropylene, polymethyl methacrylate, polyvinyl alcohol, 1~ polyamide, polyimide, polyamideimide, polyester such as poly-ethylene terephthalate, poly-carbonate and cellulose acetate.
Among the above base films, however, fiIms of homopolymers and copolymers of vinyl chloride and vinylidene chloride, resPectively, are specifically preferred in the method of the 1~ invention, since these films are soft and less expensive than the others. These films, in particular, a polyvinyl chloride film, however, contain therein a plasticizer. although greatly advantageous in pricesover the other fiIms.
A variety of plasticizers are known, among which are, for ~0 instance, diphthalates such as dibutyl phthalate, dioctyl phtha-late, didecyl phthalate, di(tricresyl) phthalate and butyl benzyl phthalate; phosphates such as tricresyl phosphate, trioctyl phos-phate, triphenyl phosphate, 2-ethYlhexYI diphenyl phosphate and cresyl diphenyl phosphate: aliphatic dicarboxylic acid diesters such as dioctyl adipate. dioctyl sebacate, dioctyl azelate and tris~2-ethylhe~yl) acetyl citrate; polyester plasticizers such as polypropylene adipate and polypropylene sebacate; epoxidized plasticizers such as epoxidized soybean oils; and chlorinated plasticizers such as chlorinated paraffins and chlorinated fatty acid esters.
It has been found out by the inventors that when a layer o~ the pressure sensitive adhesive is formed directly on a base ~ilm which contains the plasticizer therein, the plasticizer migrates into the adhesive, but also the photopolymerizable l~ acrylic acid ester migrates into the base film since the plasticizer has usually a good miscibility with or solubility to the low molecular weight photopolymerizable acrylic acid ester used in the invention.
It has been found that this bidirectional migration of the plasticizer and the photopolymerizable acrylic acid e~ter in the dicing film is not only responsible for the ~emarkable decrease of the reducibility of the adhesive force ~ the pressure sensitive adhesive by the application of the ultraviolet li~ht, but also causes a gradual decrease of the a~hasive force of the adhesive itself.
Therefore, when a resin film which contains a plasticizer is used as the base film of the dicing film, it is desired that a barrier layer is interposed between the base film and the layer o~ the pressure sensitive adhesive. The barrier layer may be composed of a resin, either in the form of a film or a coating, which is impermeable both to the plasticizer and to the photopolymerizable acrylic acid ester but permeable to the ultraviolet light, so that the barrier layer prevents the migxation of the plasticizer in the base film into the layer of the adhesive and the migration of the photopolymerizable acrylic a~i~ ester in the adhesive into the base film. Thus, the barrier layer retains the photopolymerizable acrylic acid ester in the layer of the adhesive as well as the plasticizer in the base ~Eilm. As a result, the barrier layer retains the function of the ld dicing film, namely reducibility of the adhesive force by the application of the ultraviolet light after an extended period o~ storage and prevents the reduction of the adhesive force of ~ha adhesive with time before the application of the ultraviolet light.
As the barrier layer mentioned above, a film or a coatin~ of a resin such as polyolefin, e.g., polyethylene or polypropylene, polyalkylene terephthalate, e.g., polyethylene tal-aphtllalate, or polymethyl methacrylate, is pre:Eerred. The ~ar~ier layer is formed, for example, by laminating a film of a tha rasin as specified above on the base film, or by coating a melt or a solution of the barrier resin on the film. Many of the alkyd modified acrylic resin and thermosettin~ acrylic resins including an acid, a hydroxyl, an epoxy or an amide type thermosetting acrylic resin are also suitable for the barrier r~7~

1~

coating. Ilowever, depending upon the photopolymerizable acrylic acid ester and the plasticizer used, some of the acrylic resins are often found to be soluble therein or swellable therewith, and therefore, when an acrylic resin is used as a barrier resin, it is neccessary to choose such an acrylic resin which is neiter soluble in nor swell3ble with the photopolymerizable acrylic acid ester and the plasticizer used.
llowever, it will be understood that the barrier layer is not li~ited to the exemplified above, since any layer of a resin ~ay function as the barrier layer if it is impermeable both to the plasticizer and the photopolymerizable acrylic acid ester, but permeable to the u~traviolet light.
Purther according to the method of the invention, the pressure sensitive adhesive includes anhydrous silica powder ~ither a1one or in combination with a po1yisocyanate. The a~hesive force of the adhesive containing such further ~itive is reduced by the application of ultraviolet light to a greater exten-t than the adhesive which contains no silica but otherwise the same as above.
2~ ~he silica powdcr is incorporated into the adhesive in amounts of about 1-30 parts by weight in relation to 100 parts by weight of the elastic polymer. The use of the silica powder in amounts of less than about 1 part by weight in relation to 100 parts by weight of the elastic polymer is insufficient to ~5 cause a further extended reduction in the adhesive force by the ~ r~ 7~

applicaLion thereto of tlle ultraviolet light, compared wi~h the same adhesive except that it contains no silica powder. How-ever, the use of the silica powder in amounts of more than about ~0 parts by weight makes the resultant liquid adhesive composi-S tion for forming a layer of the pressure sensitive adhesivelayer In solid excessively viscous to a gel-like substance, and 3S a result, for instance, the application of the liquid compo-sition onto the basefilm difficult, A preferred amoun~ of the ~ilica i~ about 3-15 parts by weight in relation to 100 parts by ~i~ht of the el~stic polymer. The silica powder used in the in-v~ntion is preferably a finely divided powder, and for example, "~r~ tr~demark) by Degussa, West Germany, is suitable for use.
A polvisocyanate is also usable for causing a further extended reduction in the adhesive ~orce of the pressure sen-IS sitive adhesive by the aPplication of ultravioletllght when the polyisocyanate is included in the adhesive in amounts of about 1-100 parts by weight in relation to lOO parts by welght of the elastic polymer in the adhesive. ~hen the amount of the polyisocyanate used is less than about l part by ~0 wei~ht in relation to ~00 parts by weight of the elastic poly-mer, the resultant adhesive is not substantially reduced to an increased extent, whereas when the amount of the polyisocYanate is more than about lOO parts by weight, the resultant adhesive is gradually reduced in the adhesive force with time without the application thereto of the ultraviolet light~ A preferred t~'`J~

amount of the polyisocyanate is about 3-4~ parts by weight in relation to 100 partsby weight of She elastic polymer in the adhesive.
rhe polyisocyanate usable in the invention is not speci-fically limited, but a diisocyanate and a triisocyanate are praferably used. The diisocyanate usable includes, for instance, ~,4-toluene diisocyanate, m-phenylene diisocyanate. m-xylylene diisocyanate, 4,4'-diphenyl diisocyanate, 4,4'-diphenylmethane diisoGyanate, 1,5-naPhthalene diisocyanate, isophorone diiso-cyanate, dianisidine diisocyanate and hexamethylene diisocYanate,and the triisocyanate usable includes, for instance, trimethylol-propane-toluene diisocyanate adduct.
A urethane prepolymer prepared by the reaction of a diiso-cyanate in an excess amount with a dihydroxy alcohol so as to have isocyanate groups at the terminals of the polymer is also usable as a polyisocyanate in the invention.
The combined incorporation of the silica and the polyiso-r,yan~te results in a synergetic reduction in the adhesive force ~f the adhesive by the aPPlication thereto of the ultraviolet light, As stated hereinbefore, the combined use of the silica and the polyisocyanate in amounts of about 1-30 parts by weight and about 1-100 parts by weight, respectively, in relation to 100 parts by weight of the elastic polymer in the adhesive is allowed in the invention. However, smaller amounts of both of the two are sufficient to bring about the substantial reduction in the adhesive force to an increased extent due to the synergY
of the combined use of the two additives. When the two are used in combination, the silica and the polyisocyanate are incorpo-rated usllally in amounts of about 1-20 parts by weight, prefe-rflbly abollt 1-15 parts by weight, and 1-5G parts by weight, pr~ferably abollt 1-20 parts by weight, respectively. in relation to ~0 parts by weight of the elastic polymer in the adhesive.
According to the method of the invention, a semiconductor wafer is first placed and fixed on the pressure sensitive 1~ adhesive on one side of the dicing film. ~he dicing film has ;nitially an adhesive force, e.g,, several hundred grams/25 mm, sufficient to fix the wafer thereon so that the wafer may be diced to dices of a precise siæe predetermined. Then when the dicing film is irradiated by the ultraviolet light from the 1~ other side thereof after the dicing of the wafer, the substantial r~duction in the adhesive force of the dicing film takes place, th~t is, the adhesive force is reduced to several grams/25 mm to several tens grams/25 mm, and as a result, the dice on the dicing film is readily picked up therefrom.
A means and a method for applying the ultraviolet light to the dicing film after the dicing is not specifically limited, but any means and method are applicable to the method of the invention. As an exemplification only, a xenon lamp, a low pressure, a medium pressure or a high pressure mercury lamp is used as a source of the ultraviolet light, and the ultraviolet light is applied to the dicing film after the dicing for a few seconds to a few minutes from the exposed back side of the dicing film to bring about the substantial reduction in the adhesive force of the dicing film.
Further according to the invention. a dicing film may be also usable which has a pressure sensitive adhesive on one side thereof including no photopolymerization initiator. As ill be apparent, when this dicing fiIm is used in dicing, an ~lectromagnetic wave which causes polymerization of the before-said photopolymerizable acrylic acid ester other than theultraviolet light is applied to the back side of the dicing film after dicing. For example, the electron beam is preferred as tha electromagnetic wave. In this process, the dicing film is irradiated by the electron beam from the back of the film after the dicing of a semiconductor wafer so that the pressure sensi-tive adhes;ve is substantially reduced in the adhesive force.
~hen tha dice is readily removed from the dicing film.
~ he invention will be more fully understood with reference to the following examples; however these examples are intended ~0 to illustrate the invention only, and are not to be construed as limits to the scope of the invention.

E~AMPLE
A liquid acrylic resin composition on the market which mainly includes polyacrylic acid esters as the elastic polymer ~. r r dr' ~ ~ It--7 ~3 and a tackifier ~as mixed with a photopolymerizable acrylic acid ester and a photopolymerization initiator. to provide a a liquid composition having the formation as shown in Tabla 1.
The liquid composition was coated on a mold-releasing p~per and dried at 120^C for 1 minute to form a layer of pre-ssure sensitive adhesive in solid of 10 ~ m in thickness. A
base film of 0.1 mm in thickness and composed of 100 parts by weight of polyvinyl chloride of an average polymerization de~ree of about 1300. 35 parts by weight of dioctylphthalate l~ and a small amount of an stabilizer was placed on and adhered to the layer of the adhesive, and then the mold-releasing paper was removed, to provide a dicing film which had on one side th~reof a pressure sensitive adhesive including the photopoly-merizable acrylic acid ester and the photopolymerization initi-1~ ator according to the invention.
~ he adhesive force of the dicing film was measured in amanner AS follows. The dicing fiIm was cut to a test piece of ~5 mm in width and 100 mm in length, and the test piece was placed on a stainless steel plate. The test piece was then '23 pressed against the stainless steel plate by having a 3 kg roll go and return on the dicing film five times, and the 180- adhe-sive force was measured at a pulling rate of 300 mm/min. with a Schopper's tester.
The adhesive force of the dicing film before the applica-tion thereto of the ultraviolet light is presented in Table 1.

~s~-~ ~9 ~ oo-O O O _ O I O

co o c`l- u~o r- O c~ ~ u~D
o a~ _ o c~
- o -._ E Ir~ O ~ _ O _ . ~ ~r _ ~r _ y ._ _ ~r O o . ~
U~ ~ Y, s o ~o o o U~ O O Y o C~ _ ~ C~ ._ -- ~ O
o ~ _ oo Yyy _ _ o o o o C
o o o ~ E
o C~l u~ O v~ V ) ~ C~
O O O O ._ ._ :~ ~ x c c~ _ _ n o s s V~ s O
~ o ~ ~ , O _ ~
G O e --- -- 2) ~ s C~
C~ c~ ._O 3 1_ s O ~. -._ ~ ~ _ c~ ~ _ .a s ~ -s ._ v~ o ~ ~ -~ - - ._ ~ cn~
'o o -- ~ ~ ~ ~ G~I) e o o ~ ~ ~ crcrcr -a.
O ~. .. o~ O :~
O c - ~ ._ ._ V V _ c~
._ _ _ _ e e O O

~ c r~ ~ ~ _ G O O ~ V V V ~ V
~ el: O

~ g7~

Then the ultraviolet light (365 m~, 120 W/cm) is applied to the dicing film from the other side thereof for 7 seconds, and the adhesive force was measured, which is presented in Table 1.
rhe dicing film according to the invention was found to be substantially reduced in the adhesive force by the applica-tion thereto of the ultraviolet light.
As a reference, a dicing film was prePared which contained no photopolymerizable acrylic acid ester, but otherwise the same as above. The dicing film was found to be reduced only slightly in the adhesive force by the application thereto of the ultra-violet light, as presented in Reference Examples 1 and 2 in ~able ~.
Por a further reference, a dicing film was prepared in the sa~e manner as above except the use of a liquid pressure sen-1~ sitive adhesive compotion on the market including rubbers as theala~tic polymer in place of polyacrylic acid ester coplymers.
~his dicing film, including the photopolymeriÆable acrylic acid ester and the initiator, was found to increase in the adhesive farce bY the application thereto of the ultraviolet light, as ~2~ presented in Reference Examples ~ and 5.
The dicing film of Reference Example 3 contained the photopolymeriÆable acrylic acid ester in an excess amount, so that the adhesive was found to remain on the stainless steel plate after the irradiation of the ultraviolet light.

3 ~

EX~lMPLE 2 A mixture of a saturated copolyester, a tackifier. a photopolymeri~able acrylic acid ester and an initiator was prepared in a mixed solvent composed of 80 % by weight of 5 toluene and 20 % by weight of methyl ethyl ketone (the same in the following when a solvent is used), each in amounts speci-fied in Table 2, to provide a liquid composition for forming a pressure sensitive adhesive.
The saturated copolyester used was a condensation product of A sa turated dibasic carboxylic acid component consisting of terephthalic acid and sebacic acid in a molar ratio of the former to the latter of 70/30 and ethylene glycol component, in an eQuimolar ratio, and had a glass transition temperature of about lO'C.
The liquid composition was coated on a mold-releasing paper, and was then dried at 120~C for one minute to form a layer of a pressure sensitive adhesive in solid of 10~ m in thickness~ The same polyvinyl chloride film as used in Example ~ was placed on the layer of the adhesive on the base film, and 2~ then the mold-releasing paper was separated therefrom to provide a dicing film according to the invention.
~ s the adhesive force of the dicing film before and after the appication thereto of the ultraviolet light is presented in Table 2. the substantial reduction in the adhesive force took place by the app i ca tion of the ultraviolet light.

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As a reference, a dicing film was prepared in the same manner as above which contained no photopolymerizable acrylic acid ester, bu~ was otherwise the same as above. The dicing fiIwas found to be reduced only slightly in the adhesive force by the appIication thereto of the ultraviolet light, as illust-rated in Reference Examples 1 to 3 in Table 2.

~XAMP~E 3 By the use of the same saturated copolyester as used in E~ample 2, a liquid copolyester composition was prepared which had the formation shown in Table 3. The liquid composition was ~oated on a mold-releasing paper, and then dried at 1~0 C for one minute to form a layer of a pressure sesitive adhesive in solid of 10 ~ m in thickness.
A synthetic resin film of 0.1 mm in thickness as a base film other than polyvinyl chloride film was placed on the layer of the adhesive, and then the mold-releasing paper was separated therefrom to provide a dicing film according to the invention.
ns the adhesive force of the dicing film before and after the appication thereto of the ultraviolet light is presented in rable 3, the substantial reduction in the adhesive force was found to take place by the appication of the ultraviolet light.

EXnMPLE 4 '2~ n mixture of the same saturated copolyester as used in Example 2, a tackifier, a photopolyme~izable acrylic acid ester, an initiator and the same solvent as used in Example 2, each in amounts specified in Table 4, was prepared to provide a liquid copolyester composition for forming on the base film a layer of the pressure sensitive adhesive. The formation of the liquid composition used is presented in Table 4. The liqùid composi-tion was coated on a mold-releasing paper, and was then dried at 12Q~ for one minute to form a layer of a pressure sensitive adhesive in solid of 10~ m in thickness.
IQ A polyvinyl chloride film of 0.1 mm in thickness was prepared by a calendering process by the use of a composition oomposed of 100 parts by weight of polyvinyl chloride of an average polymerization degree of about 130Q, 35 parts by welght of a plasticizer, either dioctyl phthalate or a polyester pla-1~ sticizer, and a small amount of a stabilizer.
A barrier layer was then formed which was composed of a resin as shown in Table 4 on the polyvinyl chloride film. The p~lyvinyl chloride fiIm was placed on the layer of the adhesive 30 that the barrier layer was in contact with the adhesive, to provide a dicing film having the barrier layer interposed between the base film and the layer of the adhesive according to the invention.
After standing at a predetermined temperature for a pre-determined period of time, the mold-releasing paper was removed, a~d the adhesive force of the film was measured. Then the r " ,~ ' Examples _ _ _ Pormation of Adhesive"
Saturated copolyester 30 30 30 30 ~ylene res i n 30 20 30 20 Solvent 70 70 70 70 TMPTA 2~ 30 DPEHA3' 30 30 30 Benzoin isopropylether 4 4 6 6 Base Pilm4' PET PP PA PMMA
.
A~ses ive Porce ~g/25mm) Before U~ Irradiation450 400 300 250 After UV Irradiation 45 40 33 48 Notes: I) Parts by weight 2) ~rimethylolpropane triacrylate 3) Dipentaerythritol hexaacrylate

4) PET: Polyethylene terephthalate PP: Polypropylene PA: Polyamide PMMA: Polymethyl methacrylate ~5 V~ o o o C~
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film was irradiated by the ultraviolet light from the back side thereof in the same manner as in Example 1, and the adhesive force was measured. The change in the adhesive force before and after the irradiation of the ultraviolet light is presented S in rable ~.
Ttle dicing film according to the invention was found to be substantially reduced in the adhesive force by the applica-tion thereto of the ultraviolet light even after a long standing.
As a reference, a dicing film was prepared which contained no barrier layer, but was otherwise the same as above, As presented in Reference Example 1 in Table 4, the dicing film of reference, immediately after the preparation, was found to be substantially reduced in the adhesive force by the application thereto of the ultravi Q let light, but after a long standing the 1~ dicing film was found to have a tendency of being reduced irre-larly in the adhesive force with time without the application thereto of the ultraviolet light.
~ urther, the dicing fiIm of reference was often found to increase in the adhesive force by the application thereto of 2~ the ultraviolet light after a long standing, contrary to the dicing film according to the invention.
As a further reference, a dicing fiIm was prepared which contained no photopolymerizable acrylic acid ester, but other-wise the same as above. This dicing film was found to be sub-~5 stantially unchanged in the adhesive force by the application ~ ~ ~ 5 ~

thereto of the ultraviolet light even immediately after the preparation~

~XAMPLE 5 S A liquid acrylic resin composition on the market (Polythick ~ A, 3anyo Kasei Kogyo K.U.) including polyacrylic acid ester coplymers in amounts of about 40 ~ by weight based on the compo-sition as the elastic polymer was mixed with a photopolymeri2a-ble acrylic acid ester and an initiator, each in amounts speci-fied in Table 5, and then the resulting liquid composition was Goated on a mold-releasing paper, and was then dried at 120~
for one minute to form a layer of a pressure sensitive adhesive in solid of 10~ m in thickness.
In the same manner as in Example 4, a barrier layer was 1~ formed on the same polyvinyl chloride film as used in Example 4, and a dicing film having the barrier layer between the base film and the layer of the adhesive was prepared.
~ he dicing film according to the invention was found to ba substantially reduced in the adhesive force by the applica-~20 tion thereto of the ultraviolet light even a~ter a long standing,as illustrated in Table S.
As a reference, a dicing film was prepared which contained no photopolymerizable acrylic acid ester, but was otherwise the same as above. The dicing film was found to be substantially ~5 unchal)ged in the adhesive force by the application thereto of ~f~ '7~

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m z the ultraviolet light even immediately after the preparation, as illustrated in Reference Example 1 in Table 5.

EXA~lPI.~ 6 _ A mixture of the same saturated copolyester as used in ~ample ~, a tackifier, a photopolymerizable acrylic acid ester.
an initiator, th0 same solvent as used in Example 2 and snhydrQus silica powder ("Aerosil" (Trademark). Degussa, West Germany, the same in the following). each in amounts specified 1~ in ~able 6. was prepared to provide a liquid composition which had the formation as shown in Table 6. The composition was coated on a mold-releasing paper, and then was dried at 120C
for one minute to form a layer of a pressure sensitive adhesive i~ 301 id of 10~ m in thickness.
I~ A harrier layer was formed on the same polyvinyl chloride film as used in Exanlple d by coating a solution of modified ;lcry lic resin on the market followed by drying, and the poly-vinyl chloride film was then placed on the layer of the adhesive so that the barrier layer was in contact with the adhesive. to '20 provide a dicing film having the barrier layer interposed between the base film and the layer of the adhesive according to the invention~
After standing at a predetermined temperature for a pre-determined period of time, the mold-releasing paper was removed, and the adhes;ve force of the dicing fiIm was measured. Then 3~

the dicing film was irradiated by the ultraviolet light from the back side thereof in the same manner as in Example 1, follo~ed by the measurement of the adhesive force. The change in the adhesi~e force is presented in Table 6~
As a reference, a dicing film was prepared which contained no silica powder but was otherwise the same as above~
Eirst the dicing film containing the silica powder was found to be substantially reduced in the adhesive force by the application thereto of the ultraviolet light even after a long 1~ standing. ~econd the dicing film containing the silica powder WAS found to be reduced in the adhesive force to a greater extent than the dicing fiIm containing no silica powder therein, but otherwise the same, as apparent from the comparison with Reference Examples 1 and 2 in Table 6~
1~ However. it is to be noted that the dicing fiIm of Refe-renGe Examples 1 and 2 are still within the scope of the present invention.

E~AMPLE 7 ~ . . _ .
~a The same liquid acrylic resin composition as used in Example 5 was mixed with a photopolymeri~able acrylic acid ester, an initiator and the same anhydrous silica powder used in Example 6, each in amounts specified in Table 7, to provide a liquid composition having the formation as shown in Table 7~
~he composition was coated on a mold-releasing paper, and then U~ I O Lr~ O O ~D O O O
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Examples _ 1 2 ~ormation of Adhesive"
Uiqllid acrylic adhesive 100 100 DPEHA2~ 30 30 Ben~oin isopropylether 6 6 Si 1 iC93~ 5 10 ,,, . ., _ Adsesive Porce (g/25mm) Initial Before UY Irradiation 700 800 After UY Irradiation 30 28 After standing at 80 c for 1 day Before UV Irradiation 720 780 After UV Irradiation 25 25 After standing at 80c for 3 days Before UV Irradiation 700 750 After UY Irradiation 28 25 After standing at 80~C for 5 days Before UV Irradiation 690 700 After UV Irradiation 30 20 After standing at normal temperature for 1 month Before UY Irradiation 685 725 After UY Irradiation 30 25 After standing at normal temperature for 3 months Before UV Irradiation 654 700 After UV Irradiation 26 24 _ _ . , . _ . , .
Notes: 1) Parts by weight 2) Dipentaerythritol hexaacrylate 3) "Aerosil," ~egussa, West Germany was dried at 120C for one minute to form a !ayer of a pressurs sensitive adhesive in solid of 10 ~ m in thickness.
A barrier layer was then formed in the same manner as in E~ample 6 on the same polyvinyl chloride film as used in Example ~, and the polyvinyl chloride fiIm was then placed on the layer the adhesive, to provide a dicing film having the barrier layer between the base film and the layer of the adhesive accor-ding t~ the invention.
~ he dicing film containing the silica powder was found to be substantially reduced in the adhesive force by the applica-tion thereto of the ultraviolet light even after a long standing.

~XAM~ 8 In the same manner as in Example 6 except the use of a polyisocyanate in place of the silica powder, a dicing film h~vin~ the same barrier coating of modified acrylic resin as the b~forementioned was prepared. The formation of the liquid coplyester composition used for the pressure sensitive adhesive i3 showIl in ~able 8~
As a reference, a dicing fiIm was prepared in the same manner as in Example 6 except that the film contained no poly-isocyanate.
The dicing film containing the polyisocyanate was found to be substantially reduced in the adhesive force by the applir.ation thereto of the ultraviolet light even after a long standing, but also was found to be reduced in the adhesive force to a greater extent than the dicing film containin~ no polyi so -cyanate therein, as illustrated in comparison with Reference ~xl~mples I and 2 in Table 8.

EXAMPIE_ 9 The same liquid acrylic resin composition as used in Example 5 was mixed with a photopolymerizable acrylic acid ester, an initiator and a polyisocyanate, each in amounts specified in Table 9, to provide a liquid composition having the formation as shown in Table 9.
By the use of the liquid composition thus prepared, a Aicing film was prepared in the same manner as in Example 6 having the saMe barrier coating of modified acrylic resin as lS beforementioned between the base film and the pressure sensi-tive aAhesive.
The dicing film containing the polyisocyanate was found to be suhstantially reduced in the adhesive force by the application thereto of the ultraviolet light even after a long standing, as illustrated in Table 9.

EXAMPI.E 10 In the same manner as in Example 6 except the combined use of silica powder and the polyisocyanate, a dicing film having the same barrier coating of modified acrylic resin as ~ ~5 ~ t7~9 u~ o ~n o o ~r o ~n Ln o c~
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be~oremenLioned was prepared. The formation of the liquid composition is shown in Table 10.
As a reference, a dicing film was prepared which contained only one of silica powder and the polyisocyanate.
The dicing film containing both the polyisocyanate and the silica was found to be reduced in the adhesive force to a greater extent by the application thereto of the ultraviolet light than the dicing film containing only one of the polyiso-cyanate and the silica, as illustrated in comparison with Refe-t~ rence E~amples 1 and 2 in Table 10.
Ilowever, the dicing films of Reference Examples l and 2 ~re still greater in the degree of reduction in the adhesive force by the application thereto of the ultraviolet light than the dicing films of Reference Examples 3 and 4 which 1s ~.ontained neither the silica nor the polyisocyanate. It is also to be noted that these dicing films of Reference Examples 1 to 4 are all substantially reducible in the adhesive by the ultraviolet irradiation and are within the scope of the present invention.
~0 EX~MPLE 11 The same acrylic liquid composition for a pressure sensi-tive adhesive as used in Exaple 5 was mixed with a photopolyme-ri%able acrylic acid ester, an initiator, the polyisocyanate 2~ and the silica powder, each in amounts specified in ~able 11, ~5~

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~4 to provide a liquid composition for the pressure sensitive adhesive. The formation of the liquid composition is shown in Table ll.
By the use of the liquid composition thus prepared, a dicing film was prepared in the same manner as in Example 6 having the same harrier coating of modified acrylic resin.
The dicing film containing the polyisocyanate and the silica powder was found to be reduced in the adhesive force to a greater extent than the dicing film containing only one of the polyisocyanate and the silica powder, as illustrated in comparison with Reference Examples 1 and 2 in Table 11.
The dicing film of Examples 1 and 2 are, however, still greater in the degree of reduction in the adhesive force when being irradiated by the ultraviolet light than the dicing fiIm of Reference Example 3, and are in accordance with the invention.
The dicing fiIm of Example 3 is also a fiIm usable in the invention, EXAMPbE_12 The same liquid acrylic acid ester copolymer composition as used in Example 5 and the same saturated copolyester as used in example 2 were both incorporated into a liquid composition together with a solvent, a tackifier, dipentaerythritol hexa-acrylate, benzoin isopropylether, silica and a polyisocyanate.
The formation of the resultant liquid composition is presented in Table 12.
Ry the use of the liquid composition, a dicing film was prepared in the same manner as in Example 6 having the same b~rrier coating of modified acrylic resin as beforesaid between the polyvinyl Ghloride base film and the pressure sensitive adhesi~e.
The tackiness and adhesive migration were measured as foll~)ws.
Tackiness:
A dicing film was fixed on a horizontal plane at 21C
with the layer of adhesive exposed, and a stainless steel plate was supported on the plane so that the plate intersected at the lower end with the plane at an angle of 30. A stainless steel ball of 8.0 mm in diameter and 2.0 g in weight was placed 1~ on the steel plate at a position 50 mm apart from the lower en~ of the plate. and then was allowed to roll down on the slcpe, ~lle tackiness was estimated in terms of the distance between the lower end of the steel plate and the position at which the ball stopped.
~a Adhesive migration:
A dicing film of 25 mm in width and 100 mm in length was adhered onto a stainless steel plate and was left standing at a predetermined period of time at 21C. Thereafter the film was separated from the plate at a pullin~ rate of 300 mm/
min. by a Schopper's tester, and the plate was examined

5 ~

~6 whether the adhesive was migrated thereonlo.
The above dicing film was found to have a pronouncedly large tackiness, but substantially no adhesive was found on the plate even after a long standing of seven days, as shown in Tahle l2.
~ ls a reference example, a dicing film was prepared which included only the saturated copolyester as an elastic polymer, The formation of the liquid composition used is presented in Table 12.
The reference dicing fiIm was found to have a smaller tackiness, and at the same time the adhesive was found to migrate onto the plate. However, it is to be noted that the dieing fiIms of Reference Examples 1 and 2 are in accordance with the invention and are also usable in the process of the l~ invention.

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Claims (15)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for dicing a semiconductor wafer to dices which comprises:
(a) placing and fixing the wafer on a dicing film which comprises a base film permeable to ultraviolet light and a layer of a pressure sensitive adhesive formed on one side of the base film to fix thereon the wafer, the adhesive comprising:
(i) at least one elastic polymer selected from the group consisting of a polymer mainly composed of acrylic acid ester copolymers, and a saturated copolyester mainly composed of a dibasic carboxylic acid and a dihydroxy alcohol;
(ii) an ultraviolet light polymerizable acrylic acid ester having not less than two acryloyl or methacryloyl groups in the molecule and having a molecular weight of not more than about 1000, in amounts of about 15-200 parts by weight in relation to 100 parts by weight of the elastic polymer;
(iii) a tackifier in amounts of about 10-200 parts by weight in relation to 100 parts by weight of the elastic polymer;
(iv) anhydrous silica powder in amounts of about 1-30 parts by weight in relation to 100 parts by weight of the elastic polymer; and (v) a photopolymerization initiator in sufficient amounts to induce the photopolymerization of the ultraviolet light polymerizable acrylic acid ester;
(b) dicing the wafer;
(c) applying the ultraviolet light to the other side of the dicing film to substantially reduce the adhesive force of the dicing film; and (d) removing the resultant dice from the dicing film.

2. The method as claimed in claim 1, wherein the pressure sensitive adhesive further includes a polyisocyanate in amounts of about 1-100 parts by weight in relation to 100 parts by weight of the elastic polymer.

3. The method as claimed in claim 1, wherein the base film contains a plasticizer and has a barrier layer between the base film and the layer of the adhesive, said barrier layer being composed of a resin permeable to the ultraviolet light but impermeable to both the ultraviolet light polymerizable acrylic acid ester and to the plasticizer.

4. The method as claimed in claim 3, wherein the base film is a polyvinyl chloride film.

5. The method as claimed in claim 3, wherein the barrier layer is composed of a resin selected from the group consisting of polyethylene, polypropylene, polymethyl methacrylate and polyethylene terephthalate.

6. The method as claimed in claim 3, wherein the barrier layer is composed of a coating of a modified acrylic resin selected from the group consisting of alkyd modified acrylic resin and a thermosetting acrylic resin.

7. A method for dicing a semiconductor wafer to dices which comprises:
(a) placing and fixing the wafer on a dicing film which comprises a base film permeable to an electromagnetic wave and a layer of a pressure sensitive adhesive formed on one side of the base film to fix thereon the wafer, the adhesive comprising:
(i) at least one elastic polymer selected from the group consisting of a polymer mainly composed of acrylic acid ester copolymers and a saturated copolyester mainly composed of a dibasic carboxylic acid and a dihydroxy alcohol; and (ii) an electromagnetic wave polymerizable acrylic acid ester having not less than two acryloyl or methacryloyl groups in the molecule and having a molecular weight of not more than about 1000, in amounts of about 15-200 parts by weight in relation to 100 parts by weight of the elastic polymer;
(iii) a tackifier in amounts of about 10-200 parts by weight in relation to 100 parts by weight of the elastic polymer; and (iv) anhydrous silica powder in amounts of about 1-30 parts by weight in relation to 100 parts by weight of the elastic polymer (b) dicing the wafer;
(c) applying the electromagnetic wave to the other side of the dicing film to substantially reduce the adhesive force of the dicing film; and (d) removing the resultant dice from the dicing film.

8. The method as claimed in claim 7, wherein the electro-magnetic wave is an electron beam.

9. The method as claimed in claim 8, wherein the base film contains a plasticizer and has a barrier layer between the base film and the layer of the adhesive, said barrier layer being composed of a resin permeable to the ultraviolet light but impermeable to both the ultraviolet light polymerizable acrylic acid ester and to the plasticizer.

10. The method as claimed in claim 9, wherein the base film is a polyvinyl chloride film.

11. The method as claimed in claim 9, wherein the barrier layer is composed of a resin selected from the group consisting of polyethylene, polypropylene, polymethyl methacrylate and polyethylene terephthalate.

12. The method as claimed in claim 9, wherein the barrier layer is composed of a coating of a modified acrylic resin selected from the group consisting of alkyd modified acrylic resin and a thermosetting acrylic resin.

13. The method as claimed in claim 1, 3 or 7, wherein the elastic copolymer (i) is a copolymer comprising [1] an adhesive soft segment of a low glass transition temperature in the polymer chain, said soft segment being composed of an alkyl acrylate hav-ing 2 to 8 carbon atoms in the alkyl moiety and [2] a cohesive hard segment of a high glass transition temperature in the polymer chain, said hard segment being composed of a comonomer selected from the group consisting of vinyl acetate, acrylonitrile, styrene, methyl acrylate and methyl methacrylate.

14. The method as claimed in claim 1, 3 or 7, wherein the elastic polymer (i) is the saturated copolyester alone or in com-bination with the acrylic acid ester polymer, wherein the poly-ester is composed of substantially equimolar amounts of a dibasic carboxylic acid component and a glycol, and the dibasic carboxylic acid component is a mixture of 20 to 80 molar percent of an aromatic dibasic carboxylic acid and 80 to 20 percent of an aliphatic dicarboxylic acid.

15. The method as claimed in claim 1, 2 or 3, wherein the ultraviolet light-polymerizable acrylic acid ester is an ester of acrylic acid or methacrylic acid and a polyhydroxy alcohol selected from the group consisting of ethylene glycol, 1,6-hexanediol, trimethylolpropane, tetramethylolmethane and dipentaerythritol.