WO1999066301A1 - Method for determining optical aberrations in a photorepeater for photolithography - Google Patents

Method for determining optical aberrations in a photorepeater for photolithography Download PDF

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Publication number
WO1999066301A1
WO1999066301A1 PCT/FR1999/001388 FR9901388W WO9966301A1 WO 1999066301 A1 WO1999066301 A1 WO 1999066301A1 FR 9901388 W FR9901388 W FR 9901388W WO 9966301 A1 WO9966301 A1 WO 9966301A1
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WO
WIPO (PCT)
Prior art keywords
bands
wafer
strips
photorepeater
mask
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PCT/FR1999/001388
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French (fr)
Inventor
Patrick Schiavone
Original Assignee
France Telecom
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Publication date
Application filed by France Telecom filed Critical France Telecom
Publication of WO1999066301A1 publication Critical patent/WO1999066301A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/02—Testing optical properties
    • G01M11/0242—Testing optical properties by measuring geometrical properties or aberrations
    • G01M11/0257—Testing optical properties by measuring geometrical properties or aberrations by analyzing the image formed by the object to be tested
    • G01M11/0264—Testing optical properties by measuring geometrical properties or aberrations by analyzing the image formed by the object to be tested by using targets or reference patterns
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
    • G03F7/70591—Testing optical components
    • G03F7/706—Aberration measurement

Definitions

  • the present invention relates to the field of microelectronics and more particularly the field of exposure of integrated circuit wafers through a lens system of a photorepeater with a view to etching this wafer to form integrated electronic components.
  • a large part of the dispersion of the dimensions of the electronic components integrated in a chip coming from a wafer is due to the optical aberrations of the lens system of the photorepeater.
  • the dispersion of the dimensions of the components and in particular of the transistors becomes a parameter determining who can become a brake to further reduce the dimensions.
  • the tests currently used to qualify a photorepeater are based on simple criteria such as depth of field and resolution but are unable to account for certain behaviors of the lens system.
  • aberrations other than astigmatism or spherical aberration are difficult to assess simply and quickly.
  • the known measurement techniques for determining the coma consist in measuring the deformation undergone by a circular pattern of small dimension such as a hole OV motif by a pattern constituted by the edges of a square with thick sides placed in the center of a square pattern. with thin sides.
  • these techniques have the disadvantage of being little convenient to carry out and not very sensitive.
  • the object of the present invention is to propose a method for determining optical aberrations of a lens system, in particular of a photorepeater, in particular coma.
  • This method of determining optical aberrations of a photolithographic photorepeater comprising a lens system through which a light source transfers the image of a mask onto a wafer covered with a layer of resin to be insolated, consists, according to l invention, placing in said photorepeater a reference mask comprising at least one reference pattern consisting of less than a pair of adjacent, rectilinear and parallel bands; to insulate a wafer; removing from this insulated plate the exposed areas, respectively the non-exposed areas, so as to reveal parts in relief; measuring the width of the zones corresponding to said strips; and to compare these widths measured with one another and / or with the widths of the bands of the reference mask so as to determine an aberration coefficient of the lens system in the directions perpendicular to said bands of the reference mask or to said zones of the
  • said reference pattern further comprises, preferably at least one complementary strip, rectilinear and parallel to said pair of strips and placed on one side of this pair, the distance between this complementary strip and the adjacent strip of said the pair of bands being greater than the gap between the bands of said band coviple.
  • said difference between said complementary strip and said adjacent strip is of reference at least equal to twice the difference between said strips of said pair of strips.
  • the method consists, preferably in forming on the reference mask several reference patterns whose bands are arranged in parallel, these patterns being distributed between an axis of the field of the lens system and at least one edge parallel to this axis.
  • said strips and the characteristics of the resin layer of said wafer are preferably such that the areas of said wafer corresponding to said strips are projecting.
  • FIG. 1 schematically shows an insolation device
  • FIG. 2a to 2e show the different stages of a process for etching a substrate
  • FIG. 3 shows a top view of a reference mask having several reference patterns
  • FIG. 4 shows an enlarged view of a reference pattern of Figure 3
  • FIG. 5 shows an enlarged view of the pattern obtained SLI ⁇ a substrate from the reference pattern of Figure 4;
  • FIG. 6 shows a graph of an example of a coma resulting from the aforementioned reference pattern.
  • an insolation device 1 of a substrate has been shown such as an integrated circuit board 2 which comprises a photorepeater 3.
  • This photorepeater 3 comprises a lens system 4 through which a light source 5 transfers to the wafer 2, by reducing it, the image of a transparent mask 6 on which an opaque pattern 7 is produced in order to form a pattern 8 on the plate 2.
  • the photorepeater 3 and the wafer 2 are carried by displacement means, not shown, which make it possible to place them relative to each other in different places in order to repeat this transfer and form a multiplicity of patterns 8.
  • FIG. 2a An example of a photolitography and etching process is shown in Figures 2a to 2e.
  • FIG. 2a shows that the wafer 2 is first of all covered with a layer of resin 9 above a layer 10 to be etched by metallic example.
  • FIG. 2b shows that zones 8a of the resin layer 9 have been insulated using a mask 6 comprising a desired pattern 7 using the photorepeater 3.
  • FIG. 2c shows that the resin has been chemically removed
  • FIG. 2d shows that the layer 10 has been chemically attacked or etched in the zones 8b which are no longer resin-coated.
  • FIG. 2e shows the last step which consists in chemically removing all of the resin layer remaining on the wafer so as to reveal only the protruding pattern 8 engraved in the metal layer and corresponding to the pattern 7 formed on the mask 6.
  • a reference mask 6R has been shown on which five identical patterns 7R have been formed, arranged along an axis x'x of the mask 6R corresponding to an optical axis of the lens system 4 , including a central pattern l ia, two intermediate patterns 11b and 11b 'located on either side and two patterns l ie and l ie' located near the edges of the mask parallel to the axis yy 'perpendicular to the axis x'x.
  • These identical reference patterns 7R comprise, as shown in FIG. 4, two pairs 12 and 13 respectively of opaque bands 12a, 12b and 13a, 13b, rectilinear and parallel to the axis y'y of the reference mask 6R.
  • the widths 1 of the strips 12a, 12b, 13a and 13b can advantageously be equal to approximately 0.25 microns.
  • the difference El between the bands 12a and 12b of the couple 12 and the difference between the bands 13a and 13b of the couple 13 can advantageously be equal to about 0.3 microns.
  • the difference E2 between the adjacent strips 12b and 13a of the pairs of strips 12 and 13 can advantageously be equal to approximately 1 micron.
  • the reference mask 6R being thus formed, it is installed in the photorepeater 3.
  • a 2R reference plate is also installed and its insolation and etching are carried out as described above with reference to FIGS. 2a to 2e to obtain an engraved 2R reference plate of which an 8R pattern obtained is shown in FIG. 5.
  • the widths 11 and 12 of the corresponding strips 12a and 12b of the reference torque 12 of each of the patterns l ia, 11b, 11b ', ie and ie are measured on the reference plate 2R.
  • This operation can be carried out in known manner by direct measurement using an electron microscope or by measuring the resistance of the strips by applying a determined voltage to their ends and by measuring the current flowing through them.
  • the optical aberration coefficient can then be determined. concerning the coma of the lens system 4 of the photorepeater 3.
  • the width 11 of the strip 12a is greater than the width 12 of the strip 12b.
  • the wide ir 11 of the strip 12a is less than the width 12 of the strip 12b and vice versa.
  • these differences or deviations in widths are proportional to the distance of the pattern from the axis y'y of the reference mask 6R. If we place the patterns l ia, 11b, 11b ', l ie and l ie' in positions offset along the axis y'y, we get the same width differences. Similarly, if we rotate the patterns 90 ° to place them along the y'y axis, we also get the same width differences. In the example of the statement of differences or deviations in FIG.
  • the characteristics of the reference plate 6R and the operating characteristics of the photorepeater 3 for the exposure of this plate are identical or as close as possible to the characteristics of those which will be used for the mass production of plates 2 so as to free themselves as much as possible from the effects linked to the conditions of sunshine.

Abstract

The invention concerns a method for determining optical aberrations in a photorepeater for photolithography comprising a lens system through which a light source transfers the image of a mask onto a wafer coated with a burning resin deposit, which consists in placing in said photorepeater a reference mask comprising at least one reference pattern (7R) consisting of at least a couple (12) of rectilinear parallel adjacent strips (12a, 12b); in burning a wafer; in eliminating from said burnt wafer the burnt zones, respectively the non-burnt zones, so as to produce raised parts; in measuring the length of the zones corresponding to said strips; and in comparing said measured lengths mutually and/or with the reference mask strip widths so as to determine a coefficient of aberration for the lens system along the directions perpendicular to said reference mask strips or to said burnt wafer zones.

Description

"Procédé de détermination d'aberrations "Method for determining aberrations
optiques d'un photorépéteur de photolithographie. "optics of a photolithography photorepeater. "
La présente invention concerne le domaine de la microélectronique et plus particulièrement le domaine de l'insolation de plaquettes de circuits intégrés au travers d'un système de lentilles d'un photorépéteur en vue de la gravure de cette plaquette pour former des composants électroniques intégrés.The present invention relates to the field of microelectronics and more particularly the field of exposure of integrated circuit wafers through a lens system of a photorepeater with a view to etching this wafer to form integrated electronic components.
Une partie importante de la dispersion des dimensions des composants électroniques intégrés dans une puce issue d'une plaquette est due aux aberrations optiques du système de lentilles du photorépéteur.A large part of the dispersion of the dimensions of the electronic components integrated in a chip coming from a wafer is due to the optical aberrations of the lens system of the photorepeater.
Compte tenu du fait que l'on tend à la réalisation de composants électroniques de plus en plus petits et rapprochés, de l'ordre de 0,18 ou 0,25 microns, la dispersion des dimensions des composants et notamment des transistors devient un paramètre déterminant qui peut devenir un frein pour réduire encore plus les dimensions.In view of the fact that there is a tendency to produce electronic components that are smaller and closer together, of the order of 0.18 or 0.25 microns, the dispersion of the dimensions of the components and in particular of the transistors becomes a parameter determining who can become a brake to further reduce the dimensions.
Il est donc particulièrement important pour un utilisateur de pouvoir déterminer la qualité optique du système de lentille d' in photorépéteur. Les tests actuellement utilisés de qualification d'un photorépéteur sont basés sur des critères simples tels que profondeur de champ et résolution mais sont incapables de rendre compte de certains comportements du système de lentilles.It is therefore particularly important for a user to be able to determine the optical quality of the photorepeater lens system. The tests currently used to qualify a photorepeater are based on simple criteria such as depth of field and resolution but are unable to account for certain behaviors of the lens system.
En particulier, les aberrations autres que l'astigmatisme ou l'aberration sphérique sont difficiles à évaluer de manière simple et rapide. C'est le cas en particulier de la détermination d'une aberration dénommée la coma pour laquelle l'image d'un point devient une tache allongée en direction d'un axe du système de lentilles, d'autant plus que ce point est éloigné de cet axe. Les techniques de mesure connues pour déterminer la coma consistent à mesurer la déformation subie par un motif circulaire de petite dimension tel qu'un trou OVΛ par un motif constitué par les bords d'un carré à côtés épais disposé au centre d'un motif carré à côtés fins. Ces techniques présentent cependant l'inconvénient d'être peu commodes à réaliser et peu sensibles.In particular, aberrations other than astigmatism or spherical aberration are difficult to assess simply and quickly. This is the case in particular of the determination of an aberration called the coma for which the image of a point becomes an elongated spot in the direction of an axis of the lens system, the more so as this point is distant of this axis. The known measurement techniques for determining the coma consist in measuring the deformation undergone by a circular pattern of small dimension such as a hole OV motif by a pattern constituted by the edges of a square with thick sides placed in the center of a square pattern. with thin sides. However, these techniques have the disadvantage of being little convenient to carry out and not very sensitive.
Le but de la présente invention est de proposer un procédé de détermination d'aberrations optiques d'un système de lentilles en particulier d'un photorépéteur, notamment de la coma. Ce procédé de détermination d'aberrations optiques d'un photorépéteur de photolithographie comprenant un système de lentilles au travers duquel une source lumineuse transfère l'image d'un masque sur une plaquette recouverte d'une couche de résine à insoler, consiste, selon l'invention, à placer dans ledit photorépéteur un masque de référence comprenant au moins un motif de référence constitué a moins d'un couple de bandes adjacentes, rectilignes et parallèles ; à insoler une plaquette ; à supprimer de cette plaquette insolée les zones insolées, respectivement les zones non insolées, de manière à faire apparaître des parties en relief ; à mesurer la largeur des zones correspondant auxdites bandes ; et à comparer ces largeurs mesurées entre elles et/ou aux largeurs des bandes du masque du référence de manière à déterminer un coefficient d'aberration du système de lentilles selon les directions perpendiculaires auxdites bandes du masque de référence ou auxdites zones de la plaquette insolée. Selon l'invention, la largeur de chacune desdites bandes et l'écart les séparant sont de préférence compris entre 0,8 et 1,2 fois la longueur d'onde de la source lumineuse.The object of the present invention is to propose a method for determining optical aberrations of a lens system, in particular of a photorepeater, in particular coma. This method of determining optical aberrations of a photolithographic photorepeater comprising a lens system through which a light source transfers the image of a mask onto a wafer covered with a layer of resin to be insolated, consists, according to l invention, placing in said photorepeater a reference mask comprising at least one reference pattern consisting of less than a pair of adjacent, rectilinear and parallel bands; to insulate a wafer; removing from this insulated plate the exposed areas, respectively the non-exposed areas, so as to reveal parts in relief; measuring the width of the zones corresponding to said strips; and to compare these widths measured with one another and / or with the widths of the bands of the reference mask so as to determine an aberration coefficient of the lens system in the directions perpendicular to said bands of the reference mask or to said zones of the insulated plate. According to the invention, the width of each of said bands and the distance separating them is preferably between 0.8 and 1.2 times the wavelength of the light source.
Selon l'invention, ledit motif de référence comprend en outre, de préférence au moins une bande complémentaire, rectiligne et parallèle audit couple de bandes et placée d'un côté de ce couple, l'écart entre cette bande complémentaire et la bande adjacente dudit couple de bandes étant supérieure à l'écart entre les bandes dudit coviple de bande.According to the invention, said reference pattern further comprises, preferably at least one complementary strip, rectilinear and parallel to said pair of strips and placed on one side of this pair, the distance between this complementary strip and the adjacent strip of said the pair of bands being greater than the gap between the bands of said band coviple.
Selon l'invention, ledit écart entre ladite bande complémentaire et ladite bande adjacente est de référence au moins égal à deux fois l'écart entre lesdites bandes dudit couple de bandes.According to the invention, said difference between said complementary strip and said adjacent strip is of reference at least equal to twice the difference between said strips of said pair of strips.
Selon l'invention, le procédé consiste, de préférence à former sur le masque de référence plusieurs motifs de référence dont les bandes sont disposées parallèlement, ces motifs étant répartis entre un axe du champ du système de lentilles et au moins un bord parallèle à cet axe. Selon l'invention, lesdites bandes et les caractéristiques de la couche de résine de ladite plaquette sont de préférence telles qLie les zones de ladite plaquette correspondant auxdites bandes sont en saillie. La présente invention sera mieux comprise à l'étude d'un procédé de détermination d'aberrations optiques, en particulier de la coma, d'un photorépéteur de photolitographie, décrit à titre d'exemple non limitatif et illustré par le dessin sur lequel :According to the invention, the method consists, preferably in forming on the reference mask several reference patterns whose bands are arranged in parallel, these patterns being distributed between an axis of the field of the lens system and at least one edge parallel to this axis. According to the invention, said strips and the characteristics of the resin layer of said wafer are preferably such that the areas of said wafer corresponding to said strips are projecting. The present invention will be better understood from the study of a method for determining optical aberrations, in particular coma, of a photolitic photorepeater, described by way of nonlimiting example and illustrated by the drawing in which:
- la figure 1 représente schématiquement un dispositif d'insolation ; - les figures 2a à 2e représentent les différentes étapes d'un procédé de gravure d'un substrat ;- Figure 1 schematically shows an insolation device; - Figures 2a to 2e show the different stages of a process for etching a substrate;
- la figure 3 représente une vue de dessus d'un masque de référence présentant plusieurs motifs de référence ;- Figure 3 shows a top view of a reference mask having several reference patterns;
- la figure 4 représente une vue agrandie d'un motif de référence de la figure 3 ;- Figure 4 shows an enlarged view of a reference pattern of Figure 3;
- la figure 5 représente une vue agrandie du motif obtenu SLIΓ un substrat à partir du motif de référence de la figure 4 ;- Figure 5 shows an enlarged view of the pattern obtained SLIΓ a substrate from the reference pattern of Figure 4;
- et la figure 6 représente un graphique d'un exemple de la coma résultant du motif de référence précité. En se reportant à la figure 1, on voit qu'on a représenté un dispositif d'insolation 1 d'un substrat tel qu'une plaquette de circuits intégrés 2 qui comprend un photorépéteur 3.- And Figure 6 shows a graph of an example of a coma resulting from the aforementioned reference pattern. Referring to FIG. 1, it can be seen that an insolation device 1 of a substrate has been shown such as an integrated circuit board 2 which comprises a photorepeater 3.
Ce photorépéteur 3 comprend un système de lentilles 4 au travers duquel une source lumineuse 5 transfère sur la plaquette 2, en la réduisant, l'image d'un masque transparent 6 sur lequel est réalisé un motif opaque 7 en vue de former un motif 8 sur la plaquette 2.This photorepeater 3 comprises a lens system 4 through which a light source 5 transfers to the wafer 2, by reducing it, the image of a transparent mask 6 on which an opaque pattern 7 is produced in order to form a pattern 8 on the plate 2.
Le photorépéteur 3 et la plaquette 2 sont portés par des moyens de déplacement non représentés qui permettent de les placer l'un par rapport à l'autre en différents endroits afin de répéter ce transfert et former une multiplicité de motifs 8.The photorepeater 3 and the wafer 2 are carried by displacement means, not shown, which make it possible to place them relative to each other in different places in order to repeat this transfer and form a multiplicity of patterns 8.
Un exemple d'un procédé de photolitographie et de gravure est représenté sur les figures 2a à 2e.An example of a photolitography and etching process is shown in Figures 2a to 2e.
La figure 2a montre que l'on recouvre tout d'abord la plaquette 2 d'une couche de résine 9 au-dessus d'une couche 10 à graver par exemple métallique.FIG. 2a shows that the wafer 2 is first of all covered with a layer of resin 9 above a layer 10 to be etched by metallic example.
La figure 2b montre que l'on a insolé des zones 8a de la couche de résine 9 en utilisant un masque 6 comportant un motif 7 souhaité en utilisant le photorépéteur 3. La figure 2c montre que l'on a enlevé chimiquement la résineFIG. 2b shows that zones 8a of the resin layer 9 have been insulated using a mask 6 comprising a desired pattern 7 using the photorepeater 3. FIG. 2c shows that the resin has been chemically removed
9 dans ses zones 8b non insolées.9 in its non-exposed zones 8b.
La figure 2d montre que l'on a attaqué chimiquement ou gravé la couche 10 dans les zones 8b qui ne sont plus recoLivertes de résine.FIG. 2d shows that the layer 10 has been chemically attacked or etched in the zones 8b which are no longer resin-coated.
La figure 2e montre la dernière étape qui consiste à enlever chimiquement toute la couche de résine restant sur la plaquette de manière à ne laisser apparaître que le motif en saillie 8 gravé dans la coLiche métallique et correspondant au motif 7 formé sur le masque 6.FIG. 2e shows the last step which consists in chemically removing all of the resin layer remaining on the wafer so as to reveal only the protruding pattern 8 engraved in the metal layer and corresponding to the pattern 7 formed on the mask 6.
En se reportant à la figure 3, on voit qu'on a représenté un masque de référence 6R sur lequel on a formé cinq motifs identiques 7R, disposés selon un axe x'x du masque 6R correspondant à un axe optique du système de lentilles 4, dont un motif central l ia, deux motifs intermédiaires 11b et 11b' situés de part et d'autre et deux motifs l ie et l ie' situés à proximité des bords du masque parallèles à l'axe yy' perpendiculaire à l'axe x'x. Ces motifs de référence 7R identiques comprennent, comme le montre la figure 4, deux couples 12 et 13 respectivement de bandes opaques 12a, 12b et 13a, 13b, rectilignes et parallèles à l'axe y'y du masque de référence 6R.Referring to FIG. 3, it can be seen that a reference mask 6R has been shown on which five identical patterns 7R have been formed, arranged along an axis x'x of the mask 6R corresponding to an optical axis of the lens system 4 , including a central pattern l ia, two intermediate patterns 11b and 11b 'located on either side and two patterns l ie and l ie' located near the edges of the mask parallel to the axis yy 'perpendicular to the axis x'x. These identical reference patterns 7R comprise, as shown in FIG. 4, two pairs 12 and 13 respectively of opaque bands 12a, 12b and 13a, 13b, rectilinear and parallel to the axis y'y of the reference mask 6R.
Dans vm exemple de réalisation, dans la mesure où la longueur d'onde de la source lumineuse 5 est égale à 248 nanomètres, les motifsIn an exemplary embodiment, insofar as the wavelength of the light source 5 is equal to 248 nanometers, the patterns
7R peuvent être constitués de la manière suivante.7R can be set up as follows.
Les largeurs 1 des bandes 12a, 12b, 13a et 13b peuvent avantageusement être égales à environ 0,25 microns. L'écart El entre les bandes 12a et 12b du couple 12 et l'écart entre les bandes 13a et 13b du couple 13 peuvent avantageusement être égaux à environ 0,3 microns. L'écart E2 entre les bandes adjacentes 12b et 13a des couples de bandes 12 et 13 peut avantageusement être égal à environ 1 micron.The widths 1 of the strips 12a, 12b, 13a and 13b can advantageously be equal to approximately 0.25 microns. The difference El between the bands 12a and 12b of the couple 12 and the difference between the bands 13a and 13b of the couple 13 can advantageously be equal to about 0.3 microns. The difference E2 between the adjacent strips 12b and 13a of the pairs of strips 12 and 13 can advantageously be equal to approximately 1 micron.
Le masque de référence 6R étant ainsi constitué, on l'installe dans le photorépéteur 3. On installe également une plaquette de référence 2R et on procède à son insolation et à sa gravure comme décrit précédemment en référence aux figures 2a à 2e pour obtenir une plaquette de référence 2R gravée dont un motif 8R obtenu est représenté sur la figure 5. Après quoi, on mesure sur la plaquette de référence 2R les largeurs 11 et 12 des bandes correspondantes 12a et 12b du couple de référence 12 de chacun des motifs l ia, 11 b, 11b', l ie et l ie'.The reference mask 6R being thus formed, it is installed in the photorepeater 3. A 2R reference plate is also installed and its insolation and etching are carried out as described above with reference to FIGS. 2a to 2e to obtain an engraved 2R reference plate of which an 8R pattern obtained is shown in FIG. 5. , the widths 11 and 12 of the corresponding strips 12a and 12b of the reference torque 12 of each of the patterns l ia, 11b, 11b ', ie and ie are measured on the reference plate 2R.
Cette opération peut être effectuée de façon connue grâce à une mesure directe à l'aide d'un microscope électronique ou par mesure de la résistance des bandes en appliquant à leurs extrémités une tension déterminée et en mesurant le courant qui les traverse.This operation can be carried out in known manner by direct measurement using an electron microscope or by measuring the resistance of the strips by applying a determined voltage to their ends and by measuring the current flowing through them.
En comparant entre elles les largeurs des bandes 12a et 12b du couple 12 de chacun des motifs correspondants formés sur la plaquette de référence 8R et en les comparant aux largeurs des bandes dvi masque de référence 6R, on peut alors déterminer le coefficient d'aberration optique concernant la coma du système de lentilles 4 du photorépéteur 3.By comparing the widths of the bands 12a and 12b of the couple 12 of each of the corresponding patterns formed on the reference plate 8R and by comparing them with the widths of the bands of the reference mask 6R, the optical aberration coefficient can then be determined. concerning the coma of the lens system 4 of the photorepeater 3.
C'est ainsi que l'on a p i constater les aberrations suivantes. Pour le motif correspondant central l ia, les largeurs 11 et 12 des bandes 12a et 12b sont égales.This is how we observed the following aberrations. For the corresponding central motif l ia, the widths 11 and 12 of the strips 12a and 12b are equal.
Pour le motif correspondant de bord l ie', la largeur 11 de la bande 12a est plus grande que la largeur 12 de la bande 12b.For the corresponding edge pattern l ie ', the width 11 of the strip 12a is greater than the width 12 of the strip 12b.
Pour le motif correspondant de bord l ie, la large ir 11 de la bande 12a est moins grande que la largeur 12 de la bande 12b et de façon inverse.For the corresponding edge pattern l ie, the wide ir 11 of the strip 12a is less than the width 12 of the strip 12b and vice versa.
Il en va de même en ce qui concerne les motifs intermédiaires 11b' et 11b.The same applies to the intermediate patterns 11b 'and 11b.
De plus, ces différences ou écarts de largeurs sont proportionnelles à la distance du motif par rapport à l'axe y'y du masque de référence 6R. Si l'on place les motifs l ia, 11 b, 11b', l ie et l ie' dans des positions décalées selon l'axe y'y, on obtient les mêmes différences de largeurs. De même, si l'on fait pivoter les motifs de 90° pour les placer selon l'axe y'y, on obtient également les mêmes différences de largeur. Dans l'exemple du relevé de différences ou d'écarts de la figure 6, de telles différences proportionnelles et antisymétriques correspondent à un photorépéteur dont la longueur d'onde est égale à 248 nanomètres, l'ouverture numérique égale à 0,54 et la cohérence égale à 0,52, le coefficient d'aberration coma étant égal à environ 0,2 en unité de longueur d'onde.In addition, these differences or deviations in widths are proportional to the distance of the pattern from the axis y'y of the reference mask 6R. If we place the patterns l ia, 11b, 11b ', l ie and l ie' in positions offset along the axis y'y, we get the same width differences. Similarly, if we rotate the patterns 90 ° to place them along the y'y axis, we also get the same width differences. In the example of the statement of differences or deviations in FIG. 6, such proportional and asymmetric differences correspond to a photorepeater whose wavelength is equal to 248 nanometers, the numerical aperture equal to 0.54 and the coherence equal to 0.52, the aberration coefficient coma being equal to approximately 0.2 in wavelength units.
Ayant déterminé le coefficient d'aberration de la coma du photorépéteur 3, par exemple le coefficient de la décomposition en série de puissances, on peut alors prendre en compte cette aberration pour la réalisation d'un masque 6 corrigé correspondant à un motif à insoler sur des plaquettes 2 à produire en série.Having determined the aberration coefficient of the coma of the photorepeater 3, for example the coefficient of the decomposition in series of powers, we can then take this aberration into account for the production of a corrected mask 6 corresponding to a pattern to be exposed on platelets 2 to be produced in series.
Il est particulièrement avantageux que les caractéristiques de la plaquette de référence 6R et les caractéristiques de mise en oeuvre du photorépéteur 3 pour l'insolation de cette plaquette soient identiques ou les plus proches possibles des caractéristiques de celles qui seront utilisées pour la production en série de plaquettes 2 de manière à s'affranchir le plus possible des effets liés aux conditions d'insolation. On utilisera notamment les même substrats, la même résine, la même dose d'insolation. It is particularly advantageous that the characteristics of the reference plate 6R and the operating characteristics of the photorepeater 3 for the exposure of this plate are identical or as close as possible to the characteristics of those which will be used for the mass production of plates 2 so as to free themselves as much as possible from the effects linked to the conditions of sunshine. We will use in particular the same substrates, the same resin, the same dose of sunshine.

Claims

REVENDICATIONS
1. Procédé de détermination d'aberrations optiques d'un photorépéteur de photolithographie comprenant un système de lentilles au travers duquel une source lumineuse transfère l'image d'un masqLie sur une plaquette recouverte d'une couche de résine à insoler, caractérisé par le fait qLi'il consiste :1. Method for determining optical aberrations of a photolithographic photorepeater comprising a lens system through which a light source transfers the image of a mask onto a wafer covered with a layer of resin to be exposed, characterized by does it consist:
- à placer dans ledit photorépéteur un masque de référence (6R) comprenant au moins un motif de référence (7R) constitué a i moins d'un couple (12) de bandes adjacentes, rectilignes et parallèles (12a, 12b),- placing in said photorepeater a reference mask (6R) comprising at least one reference pattern (7R) made up of at least one pair (12) of adjacent, rectilinear and parallel strips (12a, 12b),
- à insoler une plaquette (2),- to insulate a plate (2),
- à supprimer de cette plaquette insolée les zones insolées, respectivement les zones non insolées, de manière à faire apparaître des parties en relief, - à mesurer la largeur (11 , 12) des zones correspondant aLixdites bandes,- to remove from this insulated plate the insulated areas, respectively the non-insulated areas, so as to reveal parts in relief, - to measure the width (11, 12) of the areas corresponding to said bands,
- à comparer ces largeurs mesurées entre elles et/ou aux largeurs des bandes du masque du référence de manière à déterminer un coefficient d'aberration du système de lentilles selon les directions perpendiculaires auxdites bandes du masque de référence ou auxdites zones de la plaquette insolée.to compare these widths measured with each other and / or with the widths of the bands of the reference mask so as to determine an aberration coefficient of the lens system in the directions perpendicular to said bands of the reference mask or to said zones of the insulated wafer.
2. Procédé selon la revendication 1, caractérisé par le fait que la largeur (1) de chacune desdites bandes et l'écart (El) les séparant sont compris entre 0,8 et 1,2 fois la longuevir d'onde de la source lumineuse.2. Method according to claim 1, characterized in that the width (1) of each of said bands and the difference (El) separating them are between 0.8 and 1.2 times the wavelength of the source bright.
3. Procédé selon l'une des revendications 1 et 2, caractérisé par le fait que ledit motif de référence comprend en outre au moins une bande complémentaire (13a), rectiligne et parallèle audit couple (12) de bandes et placée d'un côté de ce couple, l'écart (E2) entre cette bande complémentaire et la bande adjacente dudit couple de bandes étant supérieure à l'écart (El) entre les bandes dudit couple de bande.3. Method according to one of claims 1 and 2, characterized in that said reference pattern further comprises at least one complementary strip (13a), straight and parallel to said pair (12) of strips and placed on one side of this couple, the difference (E2) between this complementary band and the adjacent band of said pair of bands being greater than the difference (El) between the bands of said pair of bands.
4. Procédé selon la revendication 3, caractérisé par le fait que ledit écart (E2) entre ladite bande complémentaire (13a) et ladite bande adjacente (12b) est au moins égal à deux fois l'écart (El) entre lesdites bandes dudit couple de bandes.4. Method according to claim 3, characterized in that said gap (E2) between said complementary strip (13a) and said adjacent strip (12b) is at least equal to twice the gap (El) between said bands of said pair of bands.
5. Procédé selon l'une quelconque des revendications précédentes, caractérisé par le fait qu'il consiste à former SLIΓ le masque de référence (6R) plusieurs motifs de référence (l la-c, l la'-c') dont les bandes sont disposées parallèlement, ces motis étant répartis entre un axe du champ du système de lentilles et au moins un bord parallèle à cet axe.5. Method according to any one of the preceding claims, characterized in that it consists in forming SLIΓ the reference mask (6R) several reference patterns (l la-c, l la'-c ') whose bands are arranged in parallel, these motis being distributed between an axis of the field of the lens system and at least one edge parallel to this axis.
6. Procédé selon l'une des revendications précédentes, caractérisé par le fait que lesdites bandes (12, 13) et les caractéristiques de la couche de résine (9) de ladite plaquette sont telles que les zones de ladite plaquette correspondant auxdites bandes sont en saillie. 6. Method according to one of the preceding claims, characterized in that said strips (12, 13) and the characteristics of the resin layer (9) of said wafer are such that the areas of said wafer corresponding to said strips are in protrusion.
PCT/FR1999/001388 1998-06-16 1999-06-11 Method for determining optical aberrations in a photorepeater for photolithography WO1999066301A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9807582A FR2779820B1 (en) 1998-06-16 1998-06-16 METHOD FOR DETERMINING OPTICAL ABERRATIONS OF A PHOTOLITHOGRAPHIC PHOTOREPECTOR.
FR98/07582 1998-06-16

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4759626A (en) * 1986-11-10 1988-07-26 Hewlett-Packard Company Determination of best focus for step and repeat projection aligners
US5402224A (en) * 1992-09-25 1995-03-28 Nikon Corporation Distortion inspecting method for projection optical system
US5615006A (en) * 1992-10-02 1997-03-25 Nikon Corporation Imaging characteristic and asymetric abrerration measurement of projection optical system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4759626A (en) * 1986-11-10 1988-07-26 Hewlett-Packard Company Determination of best focus for step and repeat projection aligners
US5402224A (en) * 1992-09-25 1995-03-28 Nikon Corporation Distortion inspecting method for projection optical system
US5615006A (en) * 1992-10-02 1997-03-25 Nikon Corporation Imaging characteristic and asymetric abrerration measurement of projection optical system

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FR2779820B1 (en) 2000-09-01

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