Ion source grid mesh for sputter coating

Abstract

The invention belongs to the technical field of optics, and particularly relates to an ion source grid mesh for sputter coating, the ion source grid mesh is a three-piece grid mesh and is composed of a screen grid mesh, an acceleration grid mesh and a grounding grid mesh; the ion beam leading-out areas of the three grid meshes have the same hole distribution characteristic, the ion beam leading-out area of each grid mesh is divided into an outer ring belt and a central area, and the diameters of ion beam leading-out holes in the outer ring belt and the central area are different; an isolating ring belt with the width being 2-3 times of the diameter of a screen grid ion beam leading-out hole exists between the outer ring belt and the central area, the outer ring belt and the central area are different in shape when the grid is formed, and the isolating ring belt serves as the joint and the bending position of the outer ring belt and the central area.

Description

Technical Field

[0001] The invention belongs to the field of optical technology, and in particular relates to an ion source grid for sputtering coating. Background Art

[0002] Ion beam sputtering coating technology is the preferred technology for preparing high-end optical thin films today. Compared with other coating methods, the optical thin films prepared by it have the advantages of dense structure, low absorption, stable performance, etc. The grid is the core component of the ion beam sputtering coating machine. Its function is to generate high-energy directional ion beams, sputter the target material through atomic cascade collisions and deposit it on a specific workpiece to form an optical thin film.

[0003] Ion beam sputtering coating usually adopts a three-piece grid assembly, which consists of a screen grid, an accelerating grid and a grounding grid. The screen grid, the accelerating grid and the grounding grid are all circular plates made of pure molybdenum plates or pure titanium plates. There is an ion beam working area 1 with a circular contour in the middle of the circular plate, and ion passage holes 5 are evenly distributed in the working area 1. The corresponding ion passage holes 3 on the screen grid, the accelerating grid and the grounding grid have different apertures. The three grids are positioned by positioning holes during installation, and the centers of the ion extraction holes at the same position of the three grids are required to be on the same axis. Different voltages are applied to the screen grid, the accelerating grid and the grounding grid to form a specific electric field. The ion extraction holes on the screen grid extract positive ions from the plasma in the discharge chamber, and a directional high-energy ion beam is generated under the joint action of the accelerating grid and the grounding grid.

[0004] Compared with other coating methods, ion beam sputtering coating technology also has problems such as difficulty in uniformity correction when coating large-sized optical parts, high-purity target materials used are expensive and have low utilization rate, and the service life of ion source grid is short. In order to solve the problem of uniformity of large-sized optical parts, the industry generally adopts increasing the width of the coating shielding plate to solve it, but the disadvantage is that the deposition rate of the coating is reduced as a whole. In terms of improving the utilization rate of the target material, the method usually adopted is to make the target material rotate around the center during the coating process or to adjust the position of the target material so that the ion beam acts on different areas of the target surface, but because the target material is located in a vacuum system and needs to be cooled by circulating water, these measures will increase the difficulty and reliability of the control system. In terms of improving the service life of the grid, the method of reducing the aperture of the ion extraction hole 3 in the grounding grid 7 or increasing the thickness of the grid is usually adopted, but both methods will aggravate the etching effect of the ion beam on the grid itself, and will ultimately affect the absorption loss of the optical film. Summary of the invention

[0005] The technical problem solved by the present invention is as follows: an ion source grid for sputtering coating is proposed to improve the problems of difficulty in correcting the uniformity of coating of large-sized workpieces, low target material utilization and short grid service life.

[0006] The technical solution of the present invention:

[0007] An ion source grid for sputtering coating, the ion source grid is a three-piece grid, consisting of a screen grid 6, an acceleration grid 7 and a grounding grid 8;

[0008] The ion beam extraction areas of the three grids have the same hole distribution characteristics, and the ion beam extraction area of ​​each grid is divided into an outer ring band 2 and a central area 4. The diameters of the ion beam extraction holes in the outer ring band 2 and the central area 4 are different; there is an isolation ring band 3 between the outer ring band 2 and the central area 4, and the width is 2 to 3 times the diameter of the ion beam extraction hole of the screen grid, and the shapes of the outer ring band 2 and the central area 4 are different when the grid is formed, and the isolation ring band 3 serves as the intersection and bending point of the outer ring band 2 and the central area 4.

[0009] Furthermore,

[0010] The surface of the outer ring belt 2 of the ion beam extraction area is an inwardly inclined surface or a slightly curved surface. The outer ring belt 2 is concave inwardly so that the ion beam in this area has a converging effect.

[0011] Furthermore,

[0012] The surface shape of the central region 4 of the ion beam extraction region is a convex spherical surface.

[0013] Furthermore,

[0014] The diameters of the ion beam extraction holes in the outer ring zone of the ion beam extraction zone are all smaller than the diameters of the ion beam extraction holes in the central zone.

[0015] Furthermore,

[0016] The diameter of the ion beam extraction hole in the central area of ​​the screen grid is a, then the diameter of the ion beam extraction hole in the outer ring belt of the screen grid is 0.9a, and the width of the isolation ring belt is 2a~3a.

[0017] Furthermore,

[0018] The diameter of the ion beam extraction hole in the outer ring belt of the accelerating grid is 0.54a, and the diameter of the ion beam extraction hole in the central area of ​​the accelerating grid is 0.6a.

[0019] Furthermore,

[0020] The diameter of the ion beam extraction hole in the outer ring belt of the ground grid is 0.675a, and the diameter of the ion beam extraction hole in the central area of ​​the ground grid is 0.75a.

[0021] Furthermore,

[0022] The outer ring band 2 of each of the three grids is an inclined ring band facing the discharge chamber, the distance d1 between the highest point of the outer ring band 2 and the edge installation plane, the central area of ​​the grid is an outward convex spherical surface, and the arch height d2 of the spherical surface is higher than the edge installation area of ​​the grid; the values ​​of d1 and d2 are jointly determined by the working area diameter D1 of the grid, the diameter D2 of the target material and the distance D3 between the grid and the target material, ensuring that the area acting on the target material is maximized under the condition that the ion beam does not overflow the target material.

[0023] The beneficial effects of the present invention are as follows: while ensuring the low absorption characteristics of the optical film, the uniformity correction problem of coating of large-size workpieces can be improved, and the utilization rate of the coating target material and the service life of the grid itself can be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of a three-piece grid of an ion beam sputtering coating machine;

[0025] 6-screen grid, 7-acceleration grid, 8-grounding grid;

[0026] Figure 2 It is a plan view of a single grid;

[0027] 1-grid edge mounting area, 2-outer ring belt of ion beam extraction area, 3-isolation ring belt in ion beam extraction area, 4-central area of ​​ion beam extraction area, 5-ion beam extraction hole;

[0028] Figure 3 It is a schematic diagram of the surface of a single-piece grid;

[0029] 2- the outer ring zone of the ion beam extraction zone, 4- the central zone of the ion beam extraction zone. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] The features and exemplary embodiments of various aspects of the invention are described in detail below.

[0032] The embodiment of the present invention provides an ion source grid for sputtering coating, which is composed of a screen grid 6, an acceleration grid 7 and a grounding grid 8; the ion beam extraction areas of the three grids have the same hole distribution characteristics, and the ion beam working area of ​​each grid is divided into two parts, an outer ring belt 2 and a central area 4, and the diameters of the ion beam extraction holes in the outer ring belt 2 and the central area 4 are different. There is an isolation ring belt 3 between the two parts, the width of which is about twice the diameter of the ion beam extraction hole of the screen grid, and the shapes of the two areas are different when the grid is formed, and the isolation ring belt is also the intersection and bending place of the two different forming areas.

[0033] There is an isolation ring 3 in the middle of the ion beam extraction area of ​​the grid, which separates two ion beam extraction areas of different shapes. It has two main functions: on the one hand, it improves the rigidity of the grid, and on the other hand, it avoids the extraction of ion beams from this area, because the extraction of ion beams requires the surface shape of the three pieces to be consistent, that is, to ensure that the spacing between the two pieces is uniform, and different grid pieces are prone to molding consistency deviations at the bends where the areas intersect, and it can also avoid mutual interference and sparking of ion beams at the bends.

[0034] The surface of the outer ring zone 2 of the ion beam extraction area is an inwardly inclined surface or a slightly curved surface. The outer ring zone is concave inwardly so that the ion beam in this area has a converging effect, which can prevent the ion beam from overflowing the target material. At the same time, the ion beam generated by it has a certain overlap with the edge of the divergent ion beam in the central area, thereby achieving the improvement of the utilization rate of the target material while reducing the absorption loss;

[0035] The surface of the central area 4 is a convex spherical surface, which has the following functions: 1. It expands the area of ​​the ion beam extraction zone as much as possible to improve the deposition rate of the coating; 2. The convex spherical surface of the central area can generate a divergent ion beam in this area, which can expand the sputtering area of ​​the target material and improve the uniformity of the coating. However, there is a problem that the density of the ion beam acting on the target surface gradually decreases from the center to the edge.

[0036] The diameters of the ion beam extraction holes in the outer rings of the ion beam extraction areas of the three grids are all smaller than the diameters of the ion beam extraction holes in the central area. Since the divergence angle of the ion beam generated by the outer ring of the grid is larger than that of the central area, the outer ring is more severely etched by the ion beam and directly affects the service life of the grid. Reducing the aperture of the outer ring is conducive to extending the service life of the grid.

[0037] Figure 1 It is a schematic structural diagram of a grid according to an embodiment of the present invention.

[0038] like Figure 1As shown, the three-piece grid includes a screen grid 6, an accelerating grid 7 and a grounding grid 8. The screen grid 6 is close to the discharge chamber and is applied with a positive bias voltage, such as 1250V; the accelerating grid 7 is located in the middle and is applied with a negative bias voltage, such as -200V; and the grounding grid 8 is located at the outermost side of the three-piece grid and is grounded at zero potential.

[0039] Figure 2 Schematic diagram of a single grid according to an embodiment of the present invention.

[0040] like Figure 2 As shown, the edge installation areas of the three grids are basically the same, mainly used for installation and positioning. The ion beam working area on the surface of the screen grid 6, the acceleration grid 7 and the grounding grid 8 is divided into three parts, which are the outer ring belt 2, the isolation ring belt 3 and the central area 4 from the outside to the inside. The ion beam extraction holes 5 are evenly distributed in the outer ring belt 2 and the central area 4. The width of the isolation ring belt is generally 2 to 3 times the diameter of the ion beam extraction hole of the screen grid.

[0041] The diameter of the ion beam extraction hole in the central area of ​​the screen grid is a, then the diameter of the ion beam extraction hole in the outer ring belt of the screen grid is 0.9a, and the width of the isolation ring belt is 2a~3a.

[0042] The diameter of the ion beam extraction hole in the outer ring belt of the accelerating grid is 0.54a, and the diameter of the ion beam extraction hole in the central area of ​​the accelerating grid is 0.6a.

[0043] The diameter of the ion beam extraction hole in the outer ring belt of the ground grid is 0.675a, and the diameter of the ion beam extraction hole in the central area of ​​the ground grid is 0.75a.

[0044] Typically, when the diameter of the ion beam extraction hole in the central area of ​​the screen grid is 2 mm, the diameter of the ion beam extraction hole in the outer ring zone of the screen grid is 1.8 mm. The width of the isolation ring zone is 4 mm to 6 mm.

[0045] The diameter of the ion beam extraction hole in the outer ring belt of the accelerating grid is 1.08 mm, and the diameter of the ion beam extraction hole in the central area of ​​the accelerating grid is 1.2 mm.

[0046] The diameter of the ion beam extraction hole in the outer ring belt of the ground grid is 1.35 mm, and the diameter of the ion beam extraction hole in the central area of ​​the ground grid is 1.5 mm.

[0047] Figure 3 FIG. 1 is a schematic diagram of a surface of a single grid according to an embodiment of the present invention.

[0048] The outer ring belt 2 of each of the three grids is an inclined ring belt facing the discharge chamber. The distance d1 between the highest point of the outer ring belt 2 and the edge installation plane is such that the ion beam generated in the area where the outer ring belt 2 is located has a converging effect, which can prevent the ion beam from overflowing the target. The center area of ​​the grid is an outward convex spherical surface, and the arch height d2 of the spherical surface can be higher than the edge installation area of ​​the grid. The values ​​of d1 and d2 are jointly determined by the working area diameter D1 of the grid, the diameter D2 of the target, and the distance D3 between the grid and the target.

[0049] Typically, when the working area diameter D1 of the grid is 160 mm, the diameter D2 of the target is 350 mm, and the distance D3 between the grid and the target is 330 mm, the distance d1 between the highest point of the outer ring belt 2 of the grid and the edge mounting plane is 2 mm, and the center area of ​​the grid is an outward convex spherical surface with an arch height of 3 mm.

[0050] After adopting the structure of the present invention, in terms of the low absorption characteristics of the coated optical film, the absorption loss of the 633nm high-reflective film at an incidence of 45 degrees can be achieved to be less than 10ppm, and in terms of the utilization rate of the coating target material, the life of the typical high-purity Ta target and SiO2 target can be increased by more than 3 times; in terms of improving the uniformity of the coating, taking the diameter of the workpiece disk of 350mm as an example, the maximum width difference of the coating shielding plate is reduced from the original 45mm to 12mm, an improvement of 73%.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the field can easily think of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. An ion source grid for sputtering coating, characterized in that: The ion source grid is a three-piece grid, consisting of a screen grid (6), an acceleration grid (7) and a grounding grid (8); The ion beam extraction zones of the three grids have the same hole distribution characteristics. The ion beam extraction zone of each grid is divided into two parts, an outer ring band (2) and a central zone (4). The diameters of the ion beam extraction holes in the outer ring band (2) and the central zone (4) are different. There is an isolation ring band (3) between the outer ring band (2) and the central zone (4), the width of which is 2 to 3 times the diameter of the ion beam extraction holes of the screen grid. When the grid is formed, the shapes of the outer ring band (2) and the central zone (4) are different. The isolation ring band (3) serves as the intersection and bending point of the outer ring band (2) and the central zone (4).

2. The ion source grid for sputtering coating according to claim 1, characterized in that: The surface of the outer ring belt (2) in the ion beam extraction area is an inwardly inclined surface or a slightly curved surface. The outer ring belt (2) is concave inwardly so that the ion beam in this area has a converging effect.

3. The ion source grid for sputtering coating according to claim 1, characterized in that: The surface shape of the central area (4) of the ion beam extraction area is a convex spherical surface.

4. The ion source grid for sputtering coating according to claim 1, characterized in that: The diameters of the ion beam extraction holes in the outer ring zone of the ion beam extraction zone are all smaller than the diameters of the ion beam extraction holes in the central zone.

5. The ion source grid for sputtering coating according to claim 4, characterized in that: The diameter of the ion beam extraction hole in the central area of ​​the screen grid is a, then the diameter of the ion beam extraction hole in the outer ring belt of the screen grid is 0.9a, and the width of the isolation ring belt is 2a~3a.

6. The ion source grid for sputtering coating according to claim 5, characterized in that: The diameter of the ion beam extraction hole in the outer ring belt of the accelerating grid is 0.54a, and the diameter of the ion beam extraction hole in the central area of ​​the accelerating grid is 0.6a.

7. The ion source grid for sputtering coating according to claim 5, characterized in that: The diameter of the ion beam extraction hole in the outer ring belt of the ground grid is 0.675a, and the diameter of the ion beam extraction hole in the central area of ​​the ground grid is 0.75a.

8. The ion source grid for sputtering coating according to claim 1, characterized in that: The outer ring belt (2) of each of the three grids is an inclined ring belt facing the discharge chamber, the distance d1 between the highest point of the outer ring belt (2) and the edge installation plane, the central area of ​​the grid is an outward convex spherical surface, and the arch height d2 of the spherical surface is higher than the grid edge installation area; the values ​​of d1 and d2 are jointly determined by the working area diameter D1 of the grid, the diameter D2 of the target material and the distance D3 between the grid and the target material, so as to ensure that the area acting on the target material is maximized under the condition that the ion beam does not overflow the target material.

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