DE3810312C2 - - Google Patents

Description

The invention relates to a method for indirect detection of agglomerate formation in agglomerate vapor deposition process according to the preamble of the patent claims 1 and an apparatus for performing the method.

The so-called ionized-cluster beam deposition process is suitable for producing a dense, high-quality film that shows good adhesion and minimizes the formation of an interface with a granular structure. The above-mentioned agglomerate vapor deposition process is described in Japanese Patent Publication 54-9,592 B2. In the agglomerate vapor deposition process, the material to be separated is placed in a closed crucible, which is placed in a vacuum container and heated to form a vapor of the material in question in the crucible with a vapor pressure of the order of 10 ^-2 to a few torr. Thereupon, the steam flows from an injection nozzle of the crucible into a vacuum region with approximately 10 ^-7 to 10 ^-4 torr, so that the steam is strongly cooled by adiabatic expansion in order to add agglomerates with 1000 to 2000 weakly interconnected atoms of the material to be deposited form. The agglomerates are then irradiated with electron beams to ionize at least some of the atoms forming the agglomerates to produce ionized agglomerates, the ionized agglomerates being imparted an additional kinetic energy by biasing the ionized agglomerates on a substrate together with neutral agglomerates as well as atoms of the material that have not formed agglomerates.

The agglomerate vapor deposition process can also be carried out with several tie gels are carried out, each with different Ma materials are loaded to make a connection film len, as described in Japanese Patent Publication 56- 41 165 B2 is disclosed. The agglomerate evaporation process can also be used to form an oxide film or a nitride film using a reactive gas that is in a vacuum vessel is used to be used, as in the japani patent publication 56-6 333 B2.

For agglomerate formation, several requirements must be met, such as a ratio of the vapor pressure P ₀ in a crucible and the pressure P in a vacuum range (P ₀ / P) of 10 ² or more, and a repeated collision between particles during the passage an injection nozzle for exchanging energy between the particles in such a way that an adiabatic expansion is brought about to produce the strongly cooled state. In the agglomerate evaporation process, the temperature of the crucible, the vapor pressure of the material in the crucible and the selection of the configuration of the injection nozzle are selected so that the above requirements are met.

In the agglomerate vapor deposition process, it is desirable that all atoms of the material that come out of the injection nozzle of the Flush out the crucible, form agglomerates. In fact will but not necessarily all of the atoms to agglomerates ten, and the formation of agglomerates depends on Be drive conditions, the structure of the mate to be vaporized riales and similar parameters. The formation of agglomerates influences the quality of the on the Deposited film. As a result, it is a confirmation generation, monitoring and determination of the formation of agglomerates  important for the practical implementation of the agglomerate steam process.

It is known that agglomerates are loosely coupled together atoms are formed as described in the article "The Formation and Kinetics of Ionized Cluster Beams "by I. Ya mada et al, which is published in Z. Phys. D. Atoms, Molecules and Clusters, Vol. 3, p. 134- 142 (1986). Therefore, the spectra of agglomerates are similar those of molecules. It is theoretically difficult to ver stand that particles flowing out of the nozzle only as Molecules are bound but not to an aggregate grow together like this in the article "Structure of Vaporized-Metal Clusters" by I. Yamada et al, in Proceedings of the Sixth Symposium on Ion Sources and Ion As sisted Technology, pp. 47-52 (1982). Through an investigation the agglomerates using an electron diffraction microscope it has been found that a typical diffraction pattern ei nes amorphous material is observed, which is only one Short-distance order and no long-distance order shows. This is an indication that large agglo merate primarily due to molecular aggregation be formed.

Therefore, the spectral analysis of the fluorescence gives through Irradiation of vapor deposition jets by means of an excitation light is obtained, an indication of the fluorescence nes material in its molecular state, whereby the Ag glomerate formation of the material can be confirmed.

DE 25 20 911 A1 describes a method for determining the Known particle flow in a vacuum coating system, in which titanium is evaporated, which is an impurity May contain titanium oxide. The result of the measurement is the Size of the contamination or the ratio of titanium to Titanium oxide. Influencing the titanium to ratio  Titanium oxide due to the test conditions is neither intended still possible.

From Spectrochimica Acta, Vol. 28 B, 1973, p. 197-210 is the application of cathode sputtering position of atomic vapors in atomic fluorescence Spectroscopy known. The fluorescence signals of various elements measured by sputtering be removed. The goal here is to determine the Composition of the sputtered material.

The invention has for its object a method and a device for indirect detection of agglomerate bil stating which is suitable, qualitatively Detect agglomerate formation, so that the agglomerate evaporation proceed in an advantageous and effective manner can be performed, so that in particular a thin film with high quality can be formed.

This problem is solved in the method according to the generic term of claim 1 by the in its characterizing Part specified features and in the device by the Features of claim 2.

In the invention, it is advantageously possible to Formation of agglomerates in the vapor deposition quantitatively determine so that the evaporation parameters, in particular the Particle temperature can be set so that the Evaporation optimal agglomerate formation occurs. There by the quality of the evaporated films can be essential Lich improve.

An embodiment of the invention is described below Reference to the drawings explained in more detail. It shows  

Figure 1 is a schematic representation of an apparatus for detecting agglomerate formation.

Fig. 2A, 2B and 2C are spectrum diagrams of the distribution of the fluorescence spectrum of a material to be evaporated; and

Fig. 3A and 3B an example of the Spectral distri development of a fluorescence spectrum of another element to be evaporated.

Fig. 1 shows a schematic representation of an embodiment of a device for detecting agglomerate formation. In Fig. 1, a vacuum container 21 is shown, which is used for the practical implementation of the agglomerate vapor deposition process, a vapor stream of a material flowing out of an injection nozzle of a closed crucible (not shown) forming an evaporation jet 22 . The vacuum container 21 has a first window 25 for the radiated from a light source 23 through an optical system 24 in the container 21 Vakuumbe excitation light 26th The vacuum container 21 has a second window 28 , through which fluorescent light 27 is detected by the vapor deposition beam 22 . The excitation light 26 is set so that it is focused on the center of the Aufdampfstrahl les 22 by means of the optical system.

The fluorescent light 27 , which passes through the window 28 of the vacuum container 21 , is fed through an optical system 29 to a spectroscope 30 and subjected to a spectral analysis, the results of which are recorded on a recorder 31 .

The excitation light 26 is introduced into the vacuum container 21 in a direction perpendicular to the direction of detection of fluorescence, whereby it is possible to minimize the interference between the excitation light 26 and the spectroscope 30 . The device shown in Fig. 1 can also be constructed such that an output signal of the spectroscope 30 is amplified by means of a photomultiplier, thereby amplifying a signal portion of the output signal together with a signal by means of an amplifier, the signal being emitted by a light Chopper is obtained, which is arranged in front of the light source 23 .

Furthermore, the windows 25 and 28 can be provided with a chicane to block stray light from the crucible and / or to prevent the light from being contaminated with a vapor of the material flowing out of the injection nozzle. A high pressure mercury lamp can be used as the light source 23 . A laser beam source can also serve as a light source.

An example of the detection of agglomerate formation with a device as shown in Fig. 1 is described below.

Silver (Ag) is selected as the material to be evaporated and loaded into the crucible to put the agglomerate evaporation process into practice. The crucible has a diameter of 1 mm. The spectral distribution of the fluorescence emanating from the vapor deposition behavior depends on the heating temperature of the crucible and thus the vapor pressure of Ag in the crucible, as shown in FIGS. 2A to 2C.

Figure 2A shows the results obtained at a crucible temperature of 1305 ° C with spectral peaks at 328 nm and 338 nm. It is obvious to those skilled in the art that these wavelengths correspond to the fluorescence spectra of mono-atomic silver. It follows from this that the jet flowing out of the nozzle is formed from atoms.

Fig. 2B shows results which are obtained at a crucible temperature of 1510 ° C. The results according to FIG. 2B show that the fluorescence of mono-atomic silver with spectra close to 328 nm and 338 nm is reduced at this temperature and that fluorescence of silver with spectral lines distributed between 430 nm and 450 nm is observed .

Ag ₂ has a peak value in the fluorescence spectrum close to 447 nm and spectral peak values in an adjacent wavelength range. Accordingly, these results show that a higher proportion of molecular silver particles or agglomerates are generated in the beam at a crucible temperature of 1510 ° C.

A comparison of FIGS. 2A and 2B shows that when the crucible rises in temperature, the intensity of the fluorescence of the molecular silver increases, as a result of which the agglomerate formation is confirmed. In this case, the pressure difference between the inside of the crucible and the outside thereof is 10⁴ or more (P ₀ / P = 10 ⁴ ). This is apparently sufficient for agglomerate formation.

Fig. 2C shows the spectral distribution of silver at a heating temperature of the crucible to 1770 ° C. The results shown in Fig. 2C show that the intensity of the fluorescence of the molecular silver is above that of the mono-atomic silver.

Fig. 3 shows the results obtained with gold (Au) and copper (Cu) as the deposition material, where in Fig. 3A the fluorescence spectrum of mono-atomic gold and molecular gold and Fig. 3B that of mono-atomic copper and molecular copper shows. As shown in FIG. 3A, gold in its mono-atomic state has fluorescence spectra close to 242 nm and 267 nm, while gold in a molecular state shows fluorescence spectra between 500 nm and 535 nm. Accordingly, copper in a mono-atomic state has fluorescence spectra close to 325 nm and 327 nm, while copper in a molecular state has fluorescence spectra between 485 nm and 522 nm.

In the embodiment shown in Fig. 1, a spectroscope is used to analyze the fluorescence of the evaporation beam. In deviation from this, a sensor can replace the spectroscope, which is suitable for detecting both the fluorescence of a material in the atomic state and the fluorescence of the material in the molecular state. The sensor can, for example, be a sensor that combines the combination of a filter that lets light with a certain wavelength pass through with a photoelectric transmitter. Furthermore, the vapor deposition beam can be irradiated with a large number of excitation light with different wavelengths, so that the wavelength of the fluorescence is changed over time, in order to detect the formation of agglomerates on the basis of a time-differentiated signal (d / dt signal).

Claims (6)

1. A method for indirect detection of agglomerate formation in the agglomerate evaporation method, in which an evaporation jet is injected from a closed crucible into a vacuum container in order to form agglomerates by adiabatic expansion of the evaporation jet, characterized in that the evaporation jet is irradiated with excitation light in order to to excite both the fluorescence spectrum of the mono-atomic evaporation material and the fluorescence spectrum of the molecularly present evaporation material, and that the intensities of the fluorescence spectra of the mono-atomic and the molecular portion of the evaporation beam are measured and compared, the ratio of the intensities being a Measure of agglomerate formation. 2. Apparatus for carrying out the method according to claim 1, characterized by a light source ( 23 ) for irradiating the evaporation beam ( 22 ) with excitation light, a device ( 30 ) for detecting the spectra len intensities of the fluorescent light emitted by the evaporation beam, and by means ( 31 ) for recording the spectral intensities of the fluorescent light. 3. Apparatus according to claim 2, characterized by a first optical system ( 24 ) for focusing the excitation light of the light source ( 23 ) in the center of the evaporation beam ( 22 ). 4. The device according to claim 3, characterized by a second optical system ( 29 ) for transmitting the fluorescent light emitted by the vapor deposition beam ( 22 ) into the device ( 30 ) for detecting the spectral intensities of the fluorescent light emitted by the vapor deposition beam ( 22 ). 5. Device according to one of claims 2 to 4, characterized in that the light source ( 23 ) and the device ( 30 ) for detecting the spectral intensities of the fluorescent light emitted by the vapor deposition ( 22 ) are arranged perpendicular to one another with respect to the vacuum container ( 21 ) . 6. Device according to one of claims 2 to 5, characterized in that the light source ( 23 ) is a high-pressure mercury lamp.