RU1812243C - Device for application of coatings in vacuum - Google Patents

Abstract

Usage: electronic technology, manufacturing of optics, optoelectronics, microelectronics, information display devices. Purpose: increasing the uniformity of the applied coatings. SUMMARY OF THE INVENTION: the device comprises an ion flux generator that forms an extended-shape ion beam from a discharge plasma. Opposite the ion generator there is an extended target, over which are placed substrates mounted with the possibility of linear movement. A gas distribution system is connected to the discharge chamber, including two gas distributors located at the ends of the ion generator and a gas distributor forming a uniform linear gas flow located in the center of the extended section. All gas distributors are connected to independent gas controllers, the inputs of which are connected through a common controller to the central gas main. 5 ill., 1 tab. ate with

Description

The invention relates to techniques for applying thin-film coatings in a vacuum and can be used in the manufacture of optics, microelectronics, optoelectronics, information display devices.

The purpose of the invention is to increase the uniformity of the coating.

Comparative analysis shows that the proposed device differs from the prototype in that the gas supply system has three independent gas supply channels connected to three gas distributors. One of them is a linear type gas distributor and is located symmetrically and parallel to the extended part of the discharge zone. Its length is determined by the length of the extended part of the discharge zone LH by the distance of the target substrate D using the ratio A L - k -D, where k is 0.5-3. Two other channels are connected to the gas distributors adjacent to the edge regions of the discharge.

The use of a three-channel gas supply system creates the conditions for compensating the edge effect when spraying a target with a tape beam by possibly adjusting the intensity of the edge parts of the ion beam by means of an adjustable gas supply to the corresponding places of the discharge. In this case, by selecting the intensities of the gas flows directed to the central and edge parts of the discharge, it is easy to achieve such a situation when, upon linear movement in the transverse direction, it is formed on the substrate

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film uniform in thickness along the length of the spray zone. By varying the distance between the target and the substrate, it is easy to achieve renewed uniformity of the coating.

The introduction of a three-channel gas supply system into the device allows achieving the final goal only if the following necessary requirement is met. The channel, which supplies the central part of the extended discharge zone with gas flow, must be connected to the gas distributor, which ensures uniform gas flow only in the section occupying the length A :. -: A L-k -D, (1) where: is the length of the extended part of the discharge zone, D is the distance between the target and the substrate, k

 0.5-3, .. /: ... . ;:

The need for such a condition is reduced by the fact that with an increase in the intensity of the gas flow at the edges of the discharge with uniform gas supply to the entire extended region of the discharge during the sputtering of the extended target due to the superposition of the flows from the central and edge sections on the substrate, zones of increased thickness are formed located between the edges and the center, In order to eliminate this phenomenon, the gas stream should be supplied only to the edge sections and to the center of the extended part of the discharge zone, guided by expression (1). Confirmation of the foregoing is the results of calculations, which are carried out on the basis of well-known laws, atomization and condensation of a material on a substrate. In this case, it was assumed that the sputtering of the material obeys the cosine law of the distribution of the sputtered particles, and the law of the distribution of the ion current on the targets is approximated by a rectangular profile,; . ; ..-.

The physical meaning of expression (1) is that the ribbon ion beam, when sprayed with an extended target, should have zones with negligible current density in the near-edge regions. The size of this zone is determined by half the subtracted value. Based on theoretical calculations and practical studies, it was determined that the optimal size of the zone into which the working gas is limited (gas enters into it only due to diffusion of atoms in the volume of the working chamber) depends on the ratio of the distance of the target substrate and the length of the spray zone, the location of the gas distributor, the design of the discharge and ion-optical systems. therefore

for each specific design of the device should choose its optimal value of the coefficient in the expression (1) from the specified range. The established range of variation of the coefficient k is limited, on the one hand, by the occurrence of heterogeneity due to near-edge thickness growth, similar to that described above (at, 5), and, on the other hand, by the occurrence of dips in the distribution function of the film thickness for excessively large sizes of the zone with a low current density ().

In FIG. Figure 1 shows the calculation results characterizing the distribution of the film thickness on the substrate during sputtering of an extended target by an ion beam of various shapes, determined by the type of gas system: a - uniform blowing of gas, and therefore, constant ion current density j over the entire extended section; b — increased intensity of the gas flow at the edges of the extended section; c - use of a three-channel gas system. The calculations were carried out for the case of the lengths of the extended spray zone 200 mm and the distance of the target substrate 50 mm.

In FIG. Figure 2 shows a diagram of a coating apparatus constructed on the basis of ion sources with a volume discharge chamber; Fig. 3 is a schematic diagram of a device based on a Holloy accelerator with a closed electron drift.

Fig. 4 shows the experimental dependences characterizing the distribution of the film thickness on the substrate, obtained by uniformly blowing into the discharge region for different target-substrate distances. Figure 5 shows similar dependences obtained for the case of a three-channel gas supply system. The device comprises an ion flux generator 1, which forms an ion beam 3 of extended geometry from a different plasma, which can be either parallel-directed ( FIG. 2), EITHER CONCERNING (FIG. 3).

Opposite the ion generator there is an extended target 4, over which are placed substrates 5, mounted with the possibility of lateral linear movement. In the ion generator, gas distributors 6 and 7 are connected to the discharge chamber, which supply the plasma with working gas. Gas distributors 6 are located at the ends of the ion generator, and gas distributor 7. forming a uniform linear gas flow, is located near the center of the extended section

and has the length defined by expression (1), the gas distributors 6 are connected to the independent gas regulators 8 and 9, and 7 to the regulator 10. The inputs of the regulators are connected to the central gas main 11 through a common regulator 12.

The device operates as follows. Using the supply voltages supplied to the electrodes of the discharge chamber, the plasma discharge is ignited in the ion generator, having previously set the required working pressure in the chamber using the regulator 12. The formed ion beam enters the target 4, and the atomized stream enters the moving substrates b. After the operating conditions of the spraying process are established, the gas flows through the channels are adjusted using regulators 8,9 and 10 until a uniform coating is formed on the substrates 5. In this case, uniformity control can be carried out both with the aid of flow rate sensors and by the thickness of the applied film on the substrate. When changing the distance of the target substrate, the length of the gas distributor 7 must be adjusted in accordance with formula (1). In order to maintain the selected gas flow ratios through the various channels, appropriate automatic stabilization systems can be used.

The effectiveness of this technical solution was tested using an ion source built on the basis of accelerators with a closed electron drift. The inhomogeneity of the applied coating on glass, obtained under conditions of uniform gas blowing into the discharge gap, was compared with the heterogeneity of films obtained using a three-channel gas supply system. In this case, the device was characterized by the following geometric parameters: the shape of the discharge gap is closed 0-shaped, the length of the linear extended part is 300 mm, the radius of curvature of the end section is 50 mm, the target size is 80 380 mm, the angle of convergence of the ion beam is 120 °, target material - copper, working gas - Ag. Ion source operating mode: discharge voltage - 5 kV, current

discharge 200 mA. target current 180 mA. the working pressure in the chamber is 6.5 10 Pa, the residual gas pressure is no worse than 1.3 Pa.

The experimental data presented in Figs. 4 and 5 were obtained using an optical density meter. The thickness of the films was 50.0-70.0 mm. The table shows the measurement data of the degree of heterogeneity of the thickness

coatings T (percent) obtained at various k values. The measurement area was limited to 300 mm.

The table also gives the lengths A of the linear valve used in practice.

The research results indicate that the proposed technical solution allows to obtain a higher uniformity of the coating on the same areas, as well as to practically increase 1.3-1.6 times the area of the applied coating without compromising its uniformity. In addition, it was found that due to the possibility of controlling the intensities of flows in

The device according to the invention provides controlled reproducibility of the coating deposition, irrespective of the device operating conditions, the degree of target production, the distance between the target and the substrate.

Claims (1)

The claims A vacuum coating apparatus comprising an ion flux generator having a discharge zone and an extended-geometry ion-optical system. a gas supply system, an extended target located parallel to the discharge zone, a movable substrate holder, characterized in that, in order to increase the uniformity of the applied coating, the gas supply system contains three independent gas supply channels, one of which is connected to a linear gas distributor located along the central parts of the extended discharge zone and having a length A selected from the expression A L-k D, where L is the length of the extended part of the discharge zone, D is the distance from the target to the substrate, kr 0.5-3, and the other two channels are connected to gas distributors, located in the edge regions of the discharge.  TOO 200. & GL Em-p -50 mn ------- .p - f00Hfi 300 2mm , .p - f00Hfi youtoo FIG. 5. MO, „„