DEVICE AND METHOD FOR COATING SUBSTRATES HAVING PLANAR OR SHAPED SURFACES BY MEANS OF MAGNETRON SPUTTERING

Abstract

According to the invention, a device is provided for coating substrates having planar or shaped surfaces by means of magnetron sputtering, by means of which device surfaces having any shape, for examples lenses, aspheres or freeform surfaces which have an adjustable layer-thickness profile, can be coated such that a layer function is maintained on the substantially complete surface. A method for coating substrates having planar or shaped surfaces by means of magnetron sputtering is also provided.

Claims

1-17. (canceled)

18. A device for coating substrates having planar or shaped surfaces by magnetron sputtering comprising a) a vacuum chamber; b) at least one magnetron source having at least one magnetron electrode as coating source; c) a turntable having at least one substrate holder, with the turntable enabling a first rotational movement of the substrate and the at least one substrate holder enabling a second rotational movement; d) at least one controllable motor that is coupled to the at least one substrate holder and that effects the second rotational movement of the substrate; and e) a gradient mask having a first region that has a geometry for the inhomogeneous coating of the substrate, with the gradient mask having at least one local elevated portion or at least one local depression in profile, with the layer thickness gradient on the substrate being settable via the pitch at the flank of the elevated portion or depression; and a second region having a geometry that effects a homogeneous coating of a reference substrate.

19. The device in accordance with claim 18, wherein the gradient mask has at least one local elevated portion in profile for the coating of convexly shaped substrates and the film gradient on the substrate is settable via the pitch of the flank of the elevated portion.

20. The device in accordance with claim 18, wherein the gradient mask has at least one local depression in profile for the coating of concavely shaped substrates and the film gradient on the substrate is settable via the pitch of the flank of the depression.

21. The device in accordance with claim 18, wherein the gradient mask has a plurality of regions having different geometries that enable a coating of the substrate with different gradients.

22. The device in accordance with claim 18, wherein the controllable motor is reversibly or irreversibly fixed to the substrate holder, with the controllable motor being able to be arranged inside or outside the vacuum chamber.

23. The device in accordance with claim 18, wherein the coating source is a linear, annular, or tubular magnetron source.

24. The device in accordance with claim 18, wherein the substrate consists of a glass or a plastic.

25. The device in accordance with claim 18, wherein the substrate is an optical component.

26. The device in accordance with claim 25, wherein the optical component is selected from the group consisting of lenses, aspheres, and freeform optics.

27. The device in accordance with claim 26, wherein the lens is planar, convex, or concave.

28. A method of coating substrates having planar or shaped surfaces by magnetron sputtering, in which a) at least one substrate is arranged in an associated substrate holder on a turntable in a vacuum chamber, with the turntable enabling a first rotational movement of the substrate and the at least one substrate holder enabling a second rotational movement, with the second rotational movement taking place via a controllable motor coupled to the substrate holder; b) at least one film is deposited on the at least one substrate in a coating cycle by utilizing at least one magnetron source having at least one magnetron electrode, with the layers of source material of the magnetron electrodes being formed by sputter gas and optionally reactive gas, with a gradient mask having a first region that has a geometry for the inhomogeneous coating of the substrate, with the gradient mask having at least one local elevated portion or at least one local depression in profile, with the layer thickness gradient on the substrate being settable via the pitch at the flank of the elevated portion or depression; and a second region having a geometry that effects a homogeneous coating of a reference substrate, being used; and c) the first rotational movement being coordinated with the second rotational movement such that the second rotational movement only takes place outside the coating cycle.

29. The method in accordance with claim 28, wherein the first rotational movement of takes place at a speed of 30 to 300 r.p.m.

30. The method in accordance with claim 28, wherein the deposited film thickness per film is in the range from 1 to 1000 nm, and the number of layers is in the range from 1 to 1000.

31. The method in accordance with claim 28, wherein a continuous first rotational movement takes place for every deposited film at a speed of 10 to 300 r.p.m, and a step-wise second rotational movement takes place with n steps and a movement by an angle of 360°/n, where n=3, 6, 9, or 12.

32. The method in accordance with claim 28, wherein the gradient mask has at least one local elevated portion in profile for the coating of convexly shaped substrates and the film thickness gradient on the substrate is set via the pitch of the flank of the elevated portion.

33. The method in accordance with claim 28, wherein the gradient mask has at least one local depression in profile for the coating of concavely shaped substrates and the film thickness gradient on the substrate is set via the pitch of the flank of the depression.

34. The method in accordance with claim 28, wherein the shape of the gradient mask is detected via the local distribution of the coating rate, with the coating rate being determined via the shape of the lens in dependence on the mask shape.

Description

[0084] The subject matter in accordance with the invention will be explained in more detail with reference to the following Figures and examples without intending to restrict it to the specific embodiments shown here.

[0085] FIG. 1 shows a device without a turntable in a plan view;

[0086] FIG. 2 shows a device with a turntable in a plan view;

[0087] FIG. 3 shows a device with a turntable in a sectional view;

[0088] FIG. 4 shows a first substrate holder in accordance with the invention in a sectional view;

[0089] FIG. 5 shows a second substrate holder in accordance with the invention in a sectional view;

[0090] FIG. 6a shows a first variant of a gradient mask in accordance with the invention;

[0091] FIG. 6b shows a second variant of a gradient mask in accordance with the invention;

[0092] FIG. 6c shows a third variant of a gradient mask in accordance with the invention;

[0093] FIG. 7 shows the coating rate in dependence on the radial position of the lens with reference to a diagram;

[0094] FIG. 8 shows a lens coated in accordance with the invention; and

[0095] FIG. 9 shows a spectrum of a lens coated in accordance with the invention.

[0096] FIG. 1 schematically shows a preferred device in accordance with the invention without a turntable in a plan view. The device has three magnetron sputtering devices 2, 3, 4, of which one is designed in the single magnetron arrangement 2 and two in the dual magnetron arrangement 3, 4. The magnetron sputtering device 2 comprises a magnetron electrode 5, sputtering gas 11 and optionally reactive gas 8 and is in a vacuum 1. The magnetron sputtering devices 3, 4 each comprise two magnetron electrodes 6, 7, sputtering gas 11, and optionally reactive gas 8 and are in a vacuum 1. A plasma source 12 and a photometer 16 and/or an ellipsometry flange 17 are located in the vicinity of the magnetron sputtering devices 2, 3, 4.

[0097] FIG. 2 schematically shows a preferred embodiment of the turntable in a plan view. The turntable 10 is located in the device and in this example has ten identical substrate holders 9.

[0098] FIG. 3 schematically shows a preferred embodiment of the device with a turntable 10 in a side view. The cross-section of a magnetron sputtering device is visible which comprises two cylinders of source material 6, 7 (dual magnetron arrangement). The magnetron sputtering device is delineated in a gas-tight manner from the rest of the device at the sides of boundary walls 14, 15 and at the top by the turntable 10; it comprises sputtering gas 11, optionally reactive gas 8 and is in a vacuum 1. Two substrate holders 9 of the turntable 10 are shown or visible in the cross-section. A cover 13 is located above the turntable 10 and has boundary walls which are located to the side of the turntable 10 that closes the device in a gas-tight manner.

[0099] FIG. 4 shows the design of a substrate holder 9 in accordance with the invention. A lens 18 is here rotatingly coupled to the axle of a motor 20. The motor 20 is fixedly mounted on the substrate holder 9 and can be controlled from external. A monitor region is not provided here. The direction of coating 21 takes place from bottom to top and the movement 22 of the substrate holder from left to right.

[0100] FIG. 5 shows a design of a lens 18 to be coated in a further substrate holder 9 in accordance with the invention. The lens 18 is located in a region 24 in which the coating rate has a lateral gradient, while a coating region 23 without a gradient is provided for the reference measurement. The monitor glass provided for this purpose can run along on the substrate holder 9 shown or can be located on one of the other substrate holders 9.

[0101] FIG. 6a shows a first arrangement in accordance with the invention with the dual magnetron 36, the lens 37, and the reference glass 38. The gradient mask 31 is shaped such that it enables a homogeneous coating region 35 on a planar substrate and a region 34 with a lateral film thickness gradient. The region 34 having a lateral film thickness gradient lies on the circular path 33 and has a local elevated portion in the form of a peak. The pitch of the flanks of this local elevated portion here determines the film thickness gradient on the substrate. In the region of the circular path 33 on which the reference glass 38 is arranged, the latter is homogeneously coated, which is implemented by the sloping down profile of the gradient mask in the homogeneous region 35. This embodiment of the gradient mask enables the coating of convex substrates.

[0102] FIG. 6b shows a second arrangement in accordance with the invention with the dual magnetron 36, the lens 37, and the reference glass 38. The gradient mask 31 is shaped such that it enables a homogeneous coating region 35 on a planar substrate and a region 34 with a lateral film thickness gradient. The region 34 having a lateral film thickness gradient lies on the circular path 33 and has a local depression in the form of a valley. The pitch of the flanks of this local depression here determines the film thickness gradient on the substrate. In the region of the circular path 33 on which the reference glass 38 is arranged, the latter is homogeneously coated, which is implemented by the sloping down profile of the gradient mask in the homogeneous region 35. This embodiment of the gradient mask enables the coating of concave substrates.

[0103] FIG. 6c shows a third arrangement in accordance with the invention with the dual magnetron 36, the lenses 37 and 41, and the reference glass 38. The gradient mask 31 is shaped such that it enables a homogeneous coating region 35 and two regions 34 and 39 with lateral film thickness gradients on a planar substrate. The regions 34 and 39 having lateral film thickness gradients lie on the circular paths 33 and 40 and each have a local elevated portion in the form of a peak. The pitch of the flanks of this local elevated portion here determines the film thickness gradient on the substrate. In the region of the circular path 33 on which the reference glass 38 is arranged, the latter is homogeneously coated, which is implemented by the sloping down profile of the gradient mask in the homogeneous region 35. This embodiment of the gradient mask enables the coating of two convex substrates.

[0104] FIG. 7 represents the relative coating rate on the flat reference glass 19 or on the rotating lens 18. An increasing rate from the center to the outside (from the x axis 0 up to 10 mm to the right) results on the lens 9. The data points 1) in FIG. 8 are mirror symmetrical to the position 0 of the x axis.

[0105] FIG. 8 shows a lens 18 such as can typically be coated. It has a diameter of 20 mm and a radius of curvature of 25.8 mm. A light ray 28 incident on the lens 18 as perpendicular and a light ray 27 obliquely incident on the lens 18 are shown. The angle of incidence 29 increases at the focal point from 0° at the center to 16° at a point 5 mm remote from the center. This lens was coated with a bandpass filter on the convex side 25. A coating with broadband, anti-reflection, or blocker can take place on the planar side 26.

[0106] FIG. 9 shows measured spectra of the coated lenses at different positions. The coating consists of a bandpass having a central wavelength of approximately 665 nm. SiO.sub.2 and Ta.sub.2O.sub.5 were used as low refractive index and high refractive index materials respectively.

EXAMPLE 1

[0107] An SiO.sub.2 film having a thickness of 100 m is applied in a layer stack. The dynamic rate amounts to 0.4 nm/sec with a rotating table having a rotation frequency of 240 r.p.m., i.e., 0.1 mm per revolution. 1000 runs are then required for the 100 nm film. In this example, a rotation by 90° is carried after 250, after 500, and after 750 revolutions.

EXAMPLE 2

[0108] In a second example a rotation is carried out by 9° after every 25 revolutions to achieve a finer division.

EXAMPLE 3

Determining the Geometry of the Gradient Mask

[0109] The aim of the coating of lenses with optical filters is that the filter works the same over the total lens surface, i.e., e.g., the same transmission spectrum and reflection spectrum should result over the total lens surface for every light ray through different points of the lens. Two effects are taken into account here: [0110] The lens surface has a different surface inclination at different radii depending on the lens shape. [0111] Depending on the design of the optics, the light rays are incident on the different radial positions at a different angle, e.g., it makes a difference whether the lens is impinged by collimated or divergent light.

[0112] An “angular spectrum” is corresponding typically specified for a lens, i.e., the mean angle of incidence of the light as a function of the radial distance from the lens center. Depending on the angle of incidence, more or less pronounced spectral shifts result for an optical filter and this has to be compensated by a variation of the film thickness.

[0113] Due to an optical modeling of the filter for different angles of incidence of light, the relative film thickness as a function of the radial position from the lens center (fixed at 100% film thickness at the lens center) is ultimately obtained as the target function.

[0114] The mask form ensures an implementation of this target function that is as good as possible. The mask shape can be different depending on the lens shape, the geometry of the coating process, and also on the optical filter design.

[0115] The determination of the mask shape takes place in the following manner on the basis of this knowledge:

[0116] There is no simple, intuitive relationship between the mask shape and the resulting film thickness profile on the lens. A “digital twin” of the process was developed by which the effect of the mask shape on the film thickness distribution can be simulated. A mask shape adapted to the target function can also be determined while using an optimization algorithm. This has the advantage that the mask shape does not have to be determined in a large number of iterative experiments. The mask shape for the example of a bandpass filter on a spherical lens was determined with the aid of the digital twin and then no longer had to be reworked for the experiments.

[0117] The mask shape is implemented by consecutive arcs in this concept. Coordinate points {x.sub.k, y.sub.k}.sub.k=1 . . . N and circle radii {r.sub.k}.sub.k=1 . . . N−1 were considered by means of software. The X coordinate here faces outward from the turntable center in the radial direction; the Y coordinate faces transversely thereto, i.e., in the direction of movement of the lens. The circle radii are positive for a concave arc and negative for a convex arc.

[0118] The circle center (xm.sub.k, ym.sub.k) of the respective arc is first calculated with reference to the radius r.sub.k between two consecutive points (x.sub.k, y.sub.k), y.sub.k+1). The shape of the mask is subsequently shown as the function y(x):

y(x)=ym.sub.k±√{square root over (r.sub.k.sup.2−(x−xm.sub.k).sup.2)};x∈[xm.sub.k,xm.sub.k+1]

[0119] The positive sign is selected if r.sub.k<0, otherwise the negative sign is selected.

[0120] The digital twin calculates the resulting film thickness distribution on a lens moving through the coating compartment using this parameterization. A fit algorithm is used for the determination of the mask shape in which some of the variables of both the coordinate points {x.sub.k, y.sub.k} and the circle radii {r.sub.k} are deallocated and varied until the calculated film thickness profile corresponds as exactly as possible to the target function.

[0121] With a convex lens, the film thickness should increase toward the margin; this then produces a characteristic mask shape in which a locally serrated thickened portion of the mask impinges on the center of the lens rotating past.