Hybrid Grid

Abstract

The device for extracting ions and / or electrons from a plasma comprises a grid (1) and a grid holder (2) around which the grid (1) is fixed. According to the invention, the grid (1) is configured as an expanded metal grid. The invention also provides a plasma source, a plasma coating device, and a method for manufacturing an interference layer or an interference layer system.

Description

Technical Field

[0001] The present invention relates generally to, for example, a plasma jet source used in a vacuum coating method, and more specifically to an extraction device for extracting ions and / or electrons from a plasma.

[0002] In many methods for treating surfaces, such as coating, structuring or etching, a plasma is used to generate ions of a specific material, specifically a gas, and the method is carried out using these ions. Thus, for example, in a vacuum coating method, a plasma source can be used, from which charged particles are extracted and which can then be used to vaporize onto the surface to remove the surface or, for example, to apply an oxide layer. In this case, the plasma can be generated, for example, capacitively, i.e. in an alternating electric field, inductively or by microwaves. Charged particles, specifically ions or electrons, can be extracted from the plasma using electrodes.

[0003] It is known to use a metal grid or a metal mesh to extract ions or electrons from a plasma. [[ID=1 + 1]]

[0004] [[ID=1 + 2]] In this context, European Patent No. 0349556 (B1) describes a device for removing a surface layer by particle impact from a plasma, in which the surface of the electrode is selected such that almost the entire high-frequency voltage drops in one extraction electrode designed as a fine grid in order to achieve a uniform impact over the largest possible area of the surface by a highly parallel atomic or molecular ion beam. This electrode is designed as a properly configured wire mesh in the form of parallel wires.

[0005] Furthermore, German Patent No. 10 / 2004011118 (A1) describes an extraction electrode for a plasma beam source, the extraction electrode being designed as a circular carrier plate having a pinhole pattern.

[0006] To maintain the homogeneity of the extracted ion and / or electron beam, it is essential to keep the shape of the extraction grid constant for as long as possible, as the shape of the grid significantly affects the ion and electron beam extracted from the plasma. In particular, in grids used in prior art, the lifespan of the electrodes is compromised by the thermal expansion of various materials and systems caused during irradiation, thus posing a problem for lifespan and therefore process stability. Thermal expansion specifically causes mechanical deformation of the grid, and therefore has a very negative impact on the ion / electron distribution and thus the coating properties.

[0007] Therefore, the object of the present invention is to provide an extraction apparatus that can ensure a stable and uniform distribution of ions / electrons over a long period of time.

[0008] This objective is achieved by the extraction apparatus, plasma source, plasma coating apparatus and method described in the appended claims. Dependent claims define embodiments of the present invention.

[0009] The present invention provides an extraction apparatus for extracting ions and / or electrons from a plasma. The apparatus comprises a grid and a grid holder, the grid being fixed around the grid holder. According to the present invention, the grid is designed as an expanded metal grid. In a plan view, the apparatus preferably has a substantially circular shape.

[0010] The grid holder may have a main body and a clamping ring for securing the expanded metal grid to the main body. Furthermore, a spacer may be placed between the main body and the clamping ring.

[0011] The expanded metal grid attached to the grid holder preferably forms a three-dimensional curved surface that substantially constitutes a cylindrical surface. The radius of curvature may be symmetrical around the vertices. According to one embodiment, the two radii of curvature may differ on either side of a vertex so that an asymmetrical shape of the grid is formed around the vertex.

[0012] In particular, in the case of an asymmetric cylindrical surface, the vertices may be offset or inclined from the center of the grid. Additionally or alternatively, the radii of curvature in the principal direction and / or within the principal direction may be different.

[0013] Conductive metals, specifically those whose oxides are optically transparent and / or similarly used in depositional layers, can be used as grid materials. Examples include titanium, tantalum, hafnium, aluminum, zirconium, niobium, their alloys, and stainless steel. The grid can further be coated with an oxide, specifically aluminum oxide, which is optically transparent and significantly increases the grid's lifespan by reducing the rate of erosion of the grid by plasma ion bombardment.

[0014] Exemplary grid dimensions include a thickness of 0.05 mm to 3 mm, a diameter of approximately 10 cm to 50 cm, specifically 30 cm, a mesh length of 0.5 mm to 10 mm, a mesh width of 0.5 mm to 10 mm, a strand width of 0.1 mm to 10 mm, and / or a strand thickness of 0.1 mm to 10 mm.

[0015] The present invention further provides a plasma source comprising a plasma chamber, a gas supply unit for supplying gas into the plasma chamber, an apparatus for generating plasma in the plasma chamber, and an apparatus according to the present invention for extracting ions and / or electrons from the plasma. The holder of the extraction apparatus should be closed to prevent leakage of source RF radiation. The grid should be mounted electrically in contact and simultaneously slidably.

[0016] The plasma source can be used specifically in a coating apparatus, along with methods such as electron beam deposition, thermal deposition, sputtering, or plasma chemical vapor deposition, and a substrate holder for holding the substrate to be coated is positioned opposite the plasma source. The substrate holder preferably has a surface that is substantially concavely curved with respect to the plasma source, or it may be flat. The substrate holder may also have a planetary arrangement with flat or concavely curved surfaces, and one or more substrates to be coated are positioned on the surface.

[0017] The grid of the extraction apparatus is preferably shaped such that the plasma distribution on the surface of the substrate holder is substantially uniform.

[0018] The substrate holder can be positioned approximately 50 cm to 200 cm, preferably 80 cm, away from the plasma source. The radius of curvature of the substrate holder can be approximately 80 cm to 150 cm, preferably 130 cm.

[0019] The present invention further provides a method for manufacturing an interference layer or interference layer system using an apparatus according to the present invention for extracting ions and / or electrons from a plasma. The method enables the manufacture of a layer having a very uniform distribution of layer properties across the entire substrate holder, such that the deviation from the mean value of the plasma distribution, measured as, for example, the etching rate of SiO2, is 10% or less.

[0020] The present invention will be further described below with reference to the drawings. [Brief explanation of the drawing]

[0021] [Figure 1] A photograph of an apparatus according to one embodiment of the present invention, having a grid holder and an expanded metal grid attached thereto, is shown. [Figure 2a] A technical diagram of a grid holder according to one embodiment of the present invention is shown. [Figure 2b] A schematic representation of variations in grid curvature is shown. [Figure 3] Figure showing the etching rate across the position of the extraction electrode of the prior art having a grid. [Figure 4] Figure showing the distribution of the etching rate of the device according to an embodiment of the present invention on a calotte having a radius of curvature of 107 cm. [Figure 5a] Figure showing a comparison of the etching rate across the position of the extraction electrode of the prior art having a grid, for the etching rate of the device according to an embodiment of the present invention on a calotte having a radius of curvature of 130 cm. [Figure 5b] Figure showing the refractive index distribution of TiO2 that can be achieved on a calotte using the present invention described herein. [Figure 6] Figure showing the spectral curve achieved using the device according to an embodiment of the present invention, for a single layer of TiO2 on a substrate, positioned along the calotte radius and corresponding to a desired uniform distribution. [Figure 7] Figure showing the spectral curve of an interference layer system achieved using the device according to an embodiment of the present invention on a substrate, positioned along the calotte radius and corresponding to a desired uniform distribution. [Figure 8] Figure showing an example of an undesirable distribution based on a single layer of TiO2, as achieved with a prior art mesh holder. [Figure 9] Figure showing the transmittance of a SiO2 layer in the UV range for an uncoated substrate, zirconium grid, titanium site, and titanium mesh. [Figure 10] Figure showing a summary of the reflection and transmittance of the SiO2 layer shown in Figure 9.

[0022] As shown in FIG. 1, the extraction device has a grid holder 2 that substantially determines the shape of the extraction device. A circular or elliptical grid 1 is fixed to the grid holder 2. Specifically, the grid holder 2 is shaped such that the grid 1 fixed thereon has a circular shape in a plan view and preferably forms a three-dimensional curved surface that substantially represents a cylindrical surface. The cylindrical surface can be curved symmetrically around the apex. However, it can also be advantageous for the cylindrical surface to have different radii of curvature around the apex, i.e., to be curved asymmetrically. In the embodiment shown in FIG. 1, the grid 1 designed as an expanded metal grid is fixed to the grid holder by four screws 21. According to one embodiment, the grid holder can have a body and a clamping ring (not shown in FIG. 1). Optionally, a spacer can be arranged between the body and the clamping ring. The spacer ensures that the expanded metal is slidably placed on the RF seal of the body, and thermal expansion can be compensated without the shape of the grid, and thus the plasma distribution, being changed by deformation.

[0023] The grid holder is schematically shown again in FIG. 2a. Here, the body 20, the screw 21, and the clamping ring 22 are shown. The shape of the grid holder 2 is such that the grid arranged thereon curves around the apex line 25 and thus essentially forms a cylindrical surface. This apex line 25, and thus the apex 24, can be placed at the center of the grid holder forming a ring, or can be offset or tilted from the center. The radius of curvature to the sides of the apex 24 can be the same or different, as shown in FIG. 2b. Here, a symmetric arrangement, an asymmetric arrangement with different radii of curvature to the left and right of the apex 24, and an asymmetric and additionally tilted arrangement where the apex 24 is offset from the center are schematically shown.

[0024] The optional spacer provided between the main body 20 and the clamp ring 22 can prevent the grid from being tightly clamped to the main body 20. Therefore, the grid can be expanded flat between the main body 20 and the clamp ring 22 without adversely affecting the plasma distribution.

[0025] The formation of a grid in the form of an expanded metal grid ensures a stable and uniform distribution of ions over a long period of time on a substrate holder positioned opposite the plasma source. In principle, the substrate is positioned opposite the plasma source on a substrate holder, for example, in the form of a spherical crown that is concave relative to the plasma source. The substrate holder may also have a planar shape. For optimal distribution, the curvature of the grid must be matched to the shape of the spherical crown that functions as the substrate holder.

[0026] The fit of the grid to the spherical cap used is reflected, for example, in the figures showing the etching rate of SiO2 across the surface of the spherical cap, as shown in Figures 3 and 4. The optimal, i.e., uniform distribution of the ion current is represented in these figures as a horizontal line across the entire surface of the spherical cap.

[0027] Figure 3 shows the etching rates over a spherical crown (radius of curvature: 107 cm) for different usage periods, indicated as operating time, when using a previously known mesh, i.e., a wire grid from the prior art. The distribution initially still appears acceptable (reference numeral 31, 30 minutes after operation), but the distribution changes dramatically even after several hours, and deteriorates considerably after 154.6 hours of operation (reference numeral 39). Specifically, the etching rate at the center of the spherical crown is 3 to 10 times higher than at the edges of the spherical crown, which results in a non-uniform distribution on the substrate depending on the arrangement of the substrate on the spherical crown.

[0028] For comparison, Figure 4 shows the service life of a grid holder according to one embodiment of the present invention. Here, it is shown that the distribution is very similar initially (reference numeral 41, 30 minutes after operation) and approximately 210 hours later (reference numeral 42). Specifically, the distribution over the range of the spherical crown (radius of curvature: 107 cm) is very uniform. Only the absolute etching rate is not identical, which can be explained by the change in the cleaning state of the system.

[0029] Figure 5 shows the etching rate distribution over a substrate holder with a radius of curvature of 130 cm, i.e., a smaller curvature than the carrot used in Figures 3 and 4. Here, a better distribution is evident with the grid holder shown herein, which has an expanded metal mesh (reference numeral 51) according to the present invention, compared with the use of a conventional grid holder (reference numeral 52). The refractive index distribution at 500 nm shown in Figure 5b over a position on the spherical crown results from the etching rate shown in Figure 5a using the grid holder with the expanded metal mesh. The etching rate shown in Figure 5a averages 26.9 nm / h, with a minimum of 25.6 nm / h (-4.6% deviation) and a maximum of 29.3 nm / h (9.2% deviation). Generally, the etching rate distribution is within ±10%. Therefore, the refractive index distribution of TiO2 shown in Figure 5b can be achieved with a minimum of 2.4575 and a maximum of 2.4609, i.e., an average value of 2.4592, which is a deviation of approximately ±0.1%.

[0030] Figure 6 shows, as an example, the distribution across a spherical crown with a radius of curvature of 130 cm for a single interference layer of TiO2 on a glass substrate. Here, it is shown that the spectral curves for substrate positions along the spherical crown radius almost overlap, meaning that a very good and uniform distribution can be achieved. The correspondence between the minimum and maximum transmittance values ​​reflects a good refractive index distribution.

[0031] Figure 7 shows the distribution of the TiO2 and SiO2 interference layer system across a spherical cap with a radius of curvature of 130 cm. Here, a very good distribution can be similarly shown by the overlap of the curves.

[0032] Figure 8 shows an example of an insufficient refractive index distribution. The minimum transmittance values ​​are very different. This difference may be due to an insufficient plasma distribution on the spherical cap as a result of using prior art wire grid holders / mesh holders.

[0033] Therefore, a grid according to one embodiment of the present invention can be used in a plasma-assisted processing system, such as a coating system, to achieve a uniform distribution of extracted ions / electrons. The uniform distribution is maintained over more than 200 hours of operation, whereas the distribution when using a prior art grid holder is not maintained consistently (see Figure 3).

[0034] This lifespan is, on the one hand, due to the holder structure that allows the expanded metal grid to expand uniformly. In contrast, the wires used in prior art extraction grids lose tension due to thermal expansion and cannot uniformly maintain the initially formed saddle shape. This has a serious negative impact on the resulting layer characteristics, particularly on the outer position of the spherical crown where the majority of the substrate is located due to the concave curved shape. The dimensional stability of the grid holder according to the present invention is achieved in that the grid holder is designed so that the grid fixed on it can expand but maintains its shape and does not deform in an uncontrolled manner. Here, the shape of the grid, i.e., the radius of curvature, is adapted to the optimal distribution of the plasma. A uniform distribution can be influenced by the shape of the grid holder used according to the present invention. This shape, and therefore the plasma distribution, remains the same over many operating times, while simultaneously ensuring the containment of RF radiation. Thus, the device seals the source RF radiation.

[0035] On the other hand, the use of expanded metal for the grid represents an important factor for dimensional stability. Expanded metal is manufactured by stretching a metal sheet that is generally cut in a staggered pattern. In the use of the present invention, conductive metals, specifically titanium, tantalum, hafnium, aluminum, zirconium, niobium, their alloys, and stainless steel, are preferably used for the expanded metal. The grid can further be coated with an oxide, specifically aluminum oxide. However, in this case, the edges of the grid must be uncoated to ensure electrical contact.

[0036] The resulting expanded metal grid provides conductivity, dimensional stability, and uniform thermal expansion induced through the holder. The shape of the expanded metal also minimizes the support surface on the holder, thus minimizing heat dissipation to the holder. Consequently, the temperature gradient across the grid is minimized.

[0037] The grid sources used typically consist of grids or meshes made of tungsten, molybdenum, or titanium. Since the grid material is also removed and incorporated into the coating, these materials and their oxides generate impurities in the range of less than 300 nm, resulting in undesirable absorption or loss in the layer properties. The inventors were able to solve this problem with an expanded metal grid made of zirconium on a novel grid holder. Figure 9 shows a comparison between the zirconium grid, a standard titanium grid, and a titanium mesh. Specifically, Figure 9 shows the transmittance of SiO2 layers in the UV range for an uncoated substrate (Suprasil_uncoated as a solid line), a zirconium grid, a titanium grid, and a titanium mesh (each with different types of dashed lines). It is clear that the layer fabricated using the zirconium grid has the highest transmittance. The thickness of the deposited SiO2 layer was approximately 600 nm (7.1λ / 4 at 500 nm).

[0038] Figure 10 again summarizes the reflectance and transmittance of the SiO2 layer shown in Figure 9. Here again, it is shown that the layer manufactured using the zirconium grid has higher values ​​than the comparison layer using the titanium grid or titanium mesh at wavelengths less than 290 nm.

[0039] Therefore, by using a zirconium grid, a significant improvement in the transparency of the layer in the UV range can be achieved.

[0040] Such an extraction apparatus is particularly used in a plasma source that is known to have a plasma chamber on which plasma is generated by applying an RF voltage, a gas supply unit for supplying gas into the plasma chamber, and the extraction apparatus according to the present invention. By applying a voltage to the grid of the extraction apparatus, charged ions or electrons are extracted from the plasma and accelerated toward a substrate placed on a substrate holder opposite the plasma source.

[0041] To manufacture the extraction apparatus according to the present invention, an expanded metal grid is provided, which is appropriately fixed on a grid holder. Here, the shape of the grid holder determines the shape of the grid, and the grid is preferably curved as described above.

[0042] The extraction apparatus, and therefore the plasma source, of the present invention can be used in the coating of a substrate, specifically in the manufacture of an interference layer or interference layer system. For the manufacture of an interference layer or interference layer system, a uniform distribution of refractive index of the material deposited across the substrate holder is advantageous. This uniform distribution requires a uniform plasma jet across the entire substrate holder provided by the present invention.

[0043] Therefore, the present invention specifically provides a grid holder for a plasma source, the grid holder being shaped to distribute the extracted plasma onto a rotating spherical crown, thereby ensuring that the plasma impact on the spherical crown is uniform over time across all substrates. This is illustrated in the measured etching rate distribution and the provided coating examples.

[0044] The grid holder is configured to allow the grid used, which is expanded metal, to perform counteracting movements when heated by the plasma without losing its shape relative to the plasma distribution. For this purpose, the grid slides on a metal RF seal, which also ensures the necessary electrical contact of the grid. A clamping ring is screwed into the holder across defined spacers to form and hold the grille. The spacers ensure that the grid can slide on the RF seal.

Claims

1. A coating apparatus, Plasma source and It has a substrate holder positioned opposite the plasma source for holding the substrate to be coated, The aforementioned plasma source is Plasma chamber and A gas supply unit for supplying gas to the plasma chamber, A device for generating plasma in the aforementioned plasma chamber, It has a device for extracting ions and / or electrons from plasma, The apparatus for extracting ions and / or electrons from the plasma is: Grid (1) and, The grid (1) has a grid holder (2) fixed around it, The grid (1) is designed as an expanded metal grid, The expanded metal grid mounted on the grid holder (2) has a curved surface and a circular shape in plan view. The substrate holder has a concave curved surface or a flat surface, and one or more substrates to be coated are arranged on the concave curved surface or flat surface. The curvature of the grid is adapted to the shape of the substrate holder. The shape of the grid is adapted to the shape of the grid holder. Coating equipment.

2. The coating apparatus according to claim 1, wherein the apparatus has a circular shape in a plan view.

3. The coating apparatus according to claim 2, wherein the grid holder (2) comprises a main body (20) and a clamp ring (22) for fixing the expanded metal grid (1) to the main body (20).

4. The coating apparatus according to claim 3, wherein a spacer is disposed between the main body (20) and the clamp ring (22).

5. The expanded metal grid (1) is asymmetrical with respect to the vertex lines, and the vertices (24) of the cylindrical three-dimensional curved surface are offset from the center of the grid. The coating apparatus according to claim 1.

6. The coating apparatus according to any one of claims 1 to 5, wherein the grid (1) has a conductive metal.

7. The coating apparatus according to any one of claims 1 to 6, wherein the grid (1) is coated with an oxide.

8. The grid (1) has a thickness of 0.05 mm to 3 mm, a diameter of 10 cm to 50 cm, a mesh length of 0.5 mm to 10 mm, a mesh width of 0.5 mm to 10 mm, a strand width of 0.1 mm to 10 mm, and / or a strand thickness of 0.1 mm to 10 mm. A coating apparatus according to any one of claims 1 to 7.

9. The coating apparatus according to claim 1, wherein the substrate holder is positioned 50 to 200 cm away from the plasma source and / or has a radius of curvature of 80 to 150 cm.

10. A coating method using the coating apparatus described in claim 1.

11. A method for manufacturing an interference layer using a coating apparatus according to any one of claims 1 to 9, wherein the coated layer has a uniform distribution and the deviation from the mean value of the plasma distribution is 10% or less.

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