LV15606B - Device for vacuum sputtering coating - Google Patents

Abstract

The invention relates to devices for spraying vacuum coatings. In the proposed magnetron sputtering device is adapted to be placed in a vacuum chamber and contains two magnetrons mounted on a magnetron holder, each on its own axis of rotation, which are inserted in a wire which is adapted to fix the magnetrons therein by means of fixing means, thus the device is adapted to magnetrons for moving and fixing, optionally changing the distances between the magnetrons and from the magnetrons to the surface to be coated and their angular position to each other or to the surface to be coated, thus adjusting the sputtering conditions of the manufactured coating.

Description

DESCRIPTION OF THE INVENTION

Technical sector

[001] The invention relates to devices for the production of vacuum coatings, namely to magnetron sputtering devices adapted to be placed in a vacuum chamber. Specifically, to a device that uses two magnetrons with a changeable positional geometric configuration, and which provides diagnostics of the optical properties of the coating during its fabrication.

Analysis of the prior art

[002] Magnetron sputtering is a widely used method for manufacturing vacuum coatings (Braun M. (2015) Magnetron Sputtering Technique. In: Nee A. (eds) Handbook of Manufacturing Engineering and Technology. Springer, London). Examples of coatings that can be produced can be metals of one or more elements, semiconductors, oxides, nitrides, carbides, hydrides, sulfides, and other compounds that are applied in one or more layers.

[003] A typical magnetron sputtering machine for the production of vacuum coatings consists of a vacuum chamber, which is equipped with vacuum pumps and in which a holder for one or more objects to be coated is inserted, a gas supply system and one or more magnetrons equipped with flat or cylindrical targets of the material to be sputtered. Applying a negative voltage to the sputtering target ignites the plasma. When the positive ions of the plasma bombard the target surface, atoms are knocked out (dusted) from the surface, which, when they reach the surface of the object to be coated, form the coating of this surface. The magnetron and the surface to be coated are in most cases placed opposite each other. Magnetrons can be operated in a variety of sputtering modes, including direct current, alternating current, radio frequency, pulsed, and high power pulsed modes, sputtering in an inert or reactive atmosphere.

[004] In order to control the sputtering process and the quality of the coatings, sensors for measuring the properties of the coatings (thickness, resistance, optical transmittance, etc.) and the characteristics of the magnetron discharge plasma during the production of the coating can also be placed in the chamber. It is known that the diagnosis of coating properties during their production helps to ensure the quality of coatings, including their thickness compliance with requirements (Zoller A. et al. In-situ Monitoring Boosts Yield of Thin-Film Deposition Processes. Photonics Spectra, July 2004).

[005] An important aspect of the design of sputtering equipment is the compactness of the units placed in the vacuum chamber, which allows optimal use of the volume of the vacuum chamber, giving the opportunity to place the necessary technological devices (magnetrons, sample holders and sensors) in the required configuration. Compact support structures and holders allow larger size magnetrons to be placed in the chamber and relatively large area coatings to be produced relative to the size of the vacuum chamber. It is also important to be able to change this configuration, making it possible to vary the properties of the coatings to be produced and allowing one sputtering machine to be used for the production of a wide range of coatings.

[006] It is generally known that the properties of coatings depend on their composition and microstructure.

[007] It is common knowledge that the distance from the magnetron to the surface to be coated affects the density of the coating to be produced. Without changing other process parameters, the coating density increases by reducing the distance between the sputtering target and the surface to be coated.

[008] There are a number of applications (eg gas sensors) that require low density coatings with a large internal surface area. Other applications (for example - electrically conductive coatings or gas-impermeable barrier layers) require high-density coatings.

[009] It is known that the properties of the coatings to be produced also depend on the angle between the surface of the sputtered target (magnetron) and the surface to be coated (LeBellac D., Azens A., Granqvist C.G. Angular selective transmittance through electrochromic tungsten oxide films made by oblique angle sputtering. Applied Physics Letters, 43, 4 (1995)).

[010] It is also known that the properties of coatings depend on whether or not the surface to be sprayed and the surface to be coated are on the same axis (opposite each other). If the surfaces are not on the same axis (pff-axes sputtering), atoms that have left the surface to be sputtered at an oblique angle and therefore have a lower energy than the atoms sputtered perpendicular to the surface (Pugel D.E, et al. Effects of target-to- substrate angle on off-axes sputter deposition and EPR studies of near-surface magnetic properties of YBCO thin films. Physica C: Superconductivity, Vol 341-348, Part 3, (2000), pp 2003-2004).

[011] It is known that several magnetrons can be placed in one vacuum chamber (EP0328257A2, WO2013023173A2). Magnetrons can be equipped with sputtering targets of one material, thereby increasing the speed of coating production, or with different targets, which allow the production of coatings containing several elements.

[012] US2016/0362812 Al describes a magnetron sputtering method that uses a single magnetron, the distance from the target to the surface to be coated can be varied from 2" to 5", and the angle between the normal to the target surface and the line connecting the target and the surface to be coated (pff-axes angle), can be changed between 45 and 70 degrees. The ability to change the angle and distance allows obtaining coatings with different compositions and properties. The drawback of the method is that in a single magnetron configuration, a corresponding sputtering target with exactly the same composition must be fabricated for each coating chemistry, which is a labor-intensive and expensive process.

Outline of the invention

[013] The invention relates to a magnetron sputtering device placed in a vacuum chamber, which contains two magnetrons with a variable distance from each other and from the surface to be coated, and with a variable angular orientation of the magnetrons to each other and to the surface to be coated. The invention also provides diagnostics of the optical properties of the coating during its manufacture.

[014] This invention provides an opportunity to choose an optimal distance between the target to be sputtered and the surface to be coated, allowing a wide range of coatings with different composition and microstructure to be made in one vacuum chamber.

[015] A significant advantage of the invention compared to US2016/0362812 AI is the use of two magnetrons in the system, as well as the possible configuration of the system not only in off-axes geometry. The use of two magnetrons makes it possible to fabricate coatings of two or more elements and independently vary the amount of these elements in the coating over a wide range using the same sputtering targets. Variation of the composition is ensured by the fact that the sputtering power supplied to each magnetron can be changed independently of the power of the other magnetron.

[016] The ability to change the distance from the target surface to the surface to be coated allows the production of coatings with different microstructures in one sputtering machine. At a smaller distance, the coatings are denser, at a greater distance - less dense.

[017] The ability to change the angular orientation of the magnetrons allows:

maintaining the focus of the sputtered material flow on the surface to be coated at a changed distance between the sputtered target and the surface to be coated;

make coatings at different angles;

to make overlays in off-axes configuration.

[018] The ability to diagnose the optical properties of the coating during its production allows to determine the correct thickness of the coating at which to stop the sputtering process. This invention suggests an optimal position of the optical channel in relation to the magnetrons and the surface to be coated, ensuring an accurate optical measurement.

[019] An essential aspect of the invention is the compactness and conceptual simplicity of the design of the magnetron holder, which allows easy and precise change of the position of the magnetrons in relation to the surface to be coated, without taking up a lot of space in the vacuum chamber and leaving the necessary space for inserting process and coating property diagnostic sensors.

[020] The magnetron sputtering device is adapted to be placed in a vacuum chamber. The device comprises two magnetrons mounted on a magnetron holder, each on its own axis of rotation, which are inserted in a wire adapted to fix the magnetrons therein by means of fixing means, thus the device is adapted to move and fix the magnetrons, optionally changing the distances between the magnetrons and distance from the magnetrons to the surface to be coated, as well as optionally independently changing the angular orientation of the magnetrons to each other and to the surface to be coated, thus changing the growth conditions of the manufactured coating. According to a preferred embodiment, the magnetron holder is provided with the ability to vary the distance from the magnetrons to the surface to be coated between 3 cm and 15 cm by placing spacers between the magnetron holder and the base plate of the camera. The device may contain an optical probe and an optical channel for measuring the optical properties of the coating to be produced, and the optical probe is adapted to be optically connected through the optical channel to a light source and a spectrophotometer located outside the vacuum chamber; the optical probe is placed between the magnetrons and is oriented perpendicular to the surface to be coated.

List of drawings

[021] Fig. 1 shows a vacuum chamber device containing two magnetrons mounted in a common holder;

Fig. 2 - two magnetron sputtering scheme;

Fig. 3 - dependence of iridium (Ir) atomic concentration and deposition rate on the sputtering power of the Ir target;

Fig. 4 - the reflection spectrum of the glass base before the coating application process;

Fig. 5 - The reflection spectrum of the ZnO coating on the glass substrate at the 14th minute of the process.

[022] A magnetron holder (2) is placed on the base plate (1) of the vacuum chamber, in which magnetrons (3 and 4) are fixed - fig. l. By releasing the fixing means, such as the nuts (5 and 6), the magnetrons can be moved along the wire (7), as well as rotate each one around its own axis. By tightening the fixing means, for example nuts (5 and 6), each of the magnetrons (3, 4) is fixed in a specific place and in a specific angular orientation. The distance between the magnetrons (3 and 4) and the surface to be coated (10) can be changed by inserting spacers between the magnetron holder (2) and the camera base plate (1).

By changing the position and angular orientation of each magnetron (3, 4), the growth conditions of the manufactured coating change.

[023] The optical probe (8) is connected to the light source and the spectrophotometer (camera base plate (1)) via the optical channel (9) (i.e. light wire) which are located outside the vacuum chamber. The probe (8) is placed between the magnetrons (3 and 4) and oriented perpendicularly to the surface to be covered (10), which is placed on the supporting structure plate (11). By sending the incoming light beam towards the surface to be coated (10) and recording the reflected light beam during the production of the coating, the reflection spectrum is measured.

Examples of implementation of the invention

[024] Example 1.

Control of layer chemistry illustrating the advantages of a two-magnetron system over a single-magnetron system. Zinc-iridium oxide (Zn-Ir-O) coatings ~500 nm thick were deposited on glass substrates by reactive magnetron sputtering from metallic Zn and Ir targets (145 mm x 92 mm x 3 mm) in an Ar + O2 atmosphere (2 Fig.). Before the deposition process, the vacuum chamber was evacuated to a pressure < 1 χ 10' ⁵ Torr. The Ar and O2 gas flows for all samples were kept constant during the process at 20 sccm and 10 sccm, respectively. Sputtering was carried out at a pressure of 10 mTorr, which was provided by a throttle valve. The distance from the target surfaces to the substrate and the angular orientation of the magnetrons (3, 4) are shown in Figure 2. The Zn target was sputtered at 200 W in constant DC mode. To vary the ratio of Zn to Ir concentrations in the films, the Ir target was sputtered with a power that was varied from 0 to 25 W. In this way, Ir concentrations ranging from 0.0 to 6.5 at.% and deposition rates from about 5, 0 to 8.5 nm/min (Fig. 3). The chemical composition of the layers was analyzed by X-ray fluorescence, and the thickness of the layers was measured by a surface profilometer.

[025] Example 2.

Example of layer thickness control using reflectance spectrum measurement during application. The optical probe (8) was placed between the magnetrons (3 and 4) according to drawing 1. Both magnetrons (3, 4) were equipped with Zn targets. The relative position of the magnetrons (3, 4) and the surface to be coated (10) was as shown in Figure 2. A ZnO coating was fabricated by sputtering the targets in an Ar + 02 atmosphere.

The incoming light from the light source was guided through the optical channel (9) and the probe (8), which focuses the light on the sample surface. The reflected light was collected in this same probe (8) and passed through an optical channel (9) to a spectrophotometer outside the vacuum chamber. The path of both reflected and incident light is parallel to the surface normal of the sample. In order to obtain an accurate measurement of the optical properties of the film, the following steps were taken during deposition:

(i) taken the reflected spectrum without the base to obtain a zero-level signal by removing the dark spectrum and the contribution from internal reflection at the junctions;

(ii) captured reflected spectrum with the substrate and the mirror placed on it to obtain a 100% reflectance light signal;

(iii) the reflection signal for the glass substrate was captured (Fig. 4);

(iv) the application of the coating was started and the reflection spectrum was continuously measured (Fig. 5), in which minima and maxima (interference effect) begin to form, the position and number of which directly depends on the thickness of the coating.

[02 6] Using this spectrum, it is possible to calibrate equipment for thickness control or to calculate thickness knowing the optical constants of the material. The application process is stopped when the reflectance spectrum (and coating thickness) exactly matches what is required.

Claims (3)

1. A magnetron sputtering device adapted to be placed in a vacuum chamber and comprising two magnetrons (3) and (4) mounted on a magnetron holder (2), each on its own axis of rotation, inserted in a wire (7) which is adapted to fix the magnetrons (3) and (4) therein by means of fixing means (5) and (6), thus the device is adapted to move and fix the magnetrons (3) and (4) by optionally changing the distances between the magnetrons (3) and (4) and from the magnetrons (3) and (4) to the surface to be coated (10), as well as independently optionally changing the angular orientation of the magnetrons (3) and (4) to each other and to the surface to be coated (10), thus changing the coating growth conditions. 2. The device according to claim 1, which differs in that the magnetron holder (2) is made with the possibility of changing the distance between the magnetrons (3) and (4) to the surface to be coated within the range of 3 cm to 15 cm, between the magnetron holder ( 2) and the camera base plate (1) by inserting the spacers. 3. A device according to any of the above claims, comprising an optical probe (8) and an optical channel (9) for measuring the optical properties of the coating to be produced, and the optical probe (8) is adapted to be optically connected through the optical channel (9) to a light source and spectrophotometer, which are located outside the vacuum chamber; the optical probe is placed between the magnetrons (3) and (4) and is oriented perpendicular to the surface to be coated (10).