WO2020104270A1

WO2020104270A1 - Method and coating installation for producing coated optical components

Info

Publication number: WO2020104270A1
Application number: PCT/EP2019/081166
Authority: WO
Inventors: Konstantin Forcht; Matthias Reischle
Original assignee: Carl Zeiss Smt Gmbh
Priority date: 2018-11-20
Filing date: 2019-11-13
Publication date: 2020-05-28
Also published as: DE102018219881A1

Abstract

In the case of a method for producing an optical component, in particular a lens or a mirror, a substrate with at least one curved substrate surface is selected and an optical coating that is rotationally symmetrical with respect to a centre of symmetry is applied to the substrate surface. For coating the substrate, the following steps are performed: Arranging a material source (110), comprising a coating material, in a source position; arranging the substrate (140) on a substrate carrier (130), which is rotatable about a substrate carrier axis of rotation (132), in such a way that, when the substrate carrier rotates, the substrate rotates about a substrate axis of rotation coaxial to the substrate carrier axis of rotation, wherein regions of the substrate surface (142) to be coated that are facing the material source can be coated at locationally varying angles of incidence (Θ2) by coating material leaving the material source; arranging a shielding screen (150) between the material source (110) and the substrate carrier so that parts of the substrate surface (142) are shielded in a phased manner, during coating, from the coating material leaving the material source. The method is characterized in that the substrate carrier axis of rotation (132) is set at an inclination with respect to a reference direction (138) in such a way that the substrate carrier axis of rotation forms a tilting angle (ϰ) with the reference direction; a shielding screen (150) is used, having a screen cutout (158), which is delimited by screen borders (155-1, 155-2) and widens outwards from an inner apex region, and the shielding screen is arranged fixed in place with respect to the substrate carrier in such a way that the apex region lies on or near the substrate carrier axis of rotation (132) and the screen cutout (158) includes a region of minimal angle of incidence of the coating material on the substrate surface. Also described is a coating installation suitable for carrying out the method and optical components that can be produced thereby.

Description

Process and coating system for producing coated optical components

The following disclosure is based on the German patent application with the file number 10 2018 219 881.0, which was filed on November 20, 2018. The disclosure content of this patent application is made by reference to the content of the present application.

APPLICATION AREA AND PRIOR ART

The invention relates to a method for producing an optical component, in which a substrate with at least one curved substrate surface is selected and an optical coating which is rotationally symmetrical with respect to a center of symmetry is applied to the substrate surface. Furthermore, the invention relates to a coating system suitable for carrying out the method and to an optical component which can be produced therewith. The optical component can in particular be a lens or a mirror.

Projection exposure systems for the microlithographic production of semiconductor components use optical systems which have a large number of lenses, which have to be coated with rotationally symmetrical optical coatings in order to reduce their reflectivity or because of other requirements. Other optical components with partially strongly curved surfaces, for example imaging mirrors for catadioptric or catoptric projection objectives, are often also to be provided with an optical coating. The optical coatings should normally have an easily controllable optical effect over the entire optically used area, e.g. the most uniform possible optical effect.

The effect of coated surfaces in the optical beam path essentially depends on the local layer thickness distribution of the optical coatings applied to these surfaces. In the case of coatings which are rotationally symmetrical with respect to a center of symmetry, the layer thickness distribution can be characterized by the radial course of the layer thickness, which is also referred to below as the layer thickness course.

Especially in systems with strongly curved optical surfaces, layer thickness distribution errors can have negative properties such as B. cause an edge drop in the transmission of a lens or the reflectivity of a mirror. Especially at strongly curved optical surfaces, variations in the refractive index of coating materials between the middle and the edge of a coating have also been observed.

It has been assumed that the observed refractive index variations of the layer material and a loose and poorly adhering structure in the edge area can be attributed to high angles of incidence of the coating material in the edge area.

Coating processes and coating systems have already been described, which were developed with this problem in mind. DE 102 37 430 A1 (corresponding to US Pat. No. 6,863,398) describes a coating system for coating substrates for optical components, in particular for coating substrates with curved substrate surfaces, and a corresponding coating method. The coating system has a planetary system for moving the substrates during the coating. The planetary system has a main carrier rotatable about a main axis of rotation and a plurality of substrate carriers which are rotatable relative to the main carrier about substrate carrier axes and are each provided for carrying a substrate. The substrate carriers are arranged relative to a material source such that the areas of the substrate surfaces facing the material source can be coated by the material source with coating material at an angle of incidence. The coating system has a first control device for controlling a radial course of the layer thickness of the coating such that the amount of coating impinging on the substrate surface can be set as a function of the radial distance from coating locations from the substrate axis of rotation. The first control device has one or more stationary first screens arranged between the material source and the substrate for temporarily shading the coating surface against the material source during the movement of the substrate. Furthermore, a second control device for controlling the angle of impact of the coating material is provided in such a way that the angle of impact during the coating process is not greater than a predetermined limit of impact angle at any coating location on the coating surface. For each substrate carrier, the second control device has a second diaphragm which is rotatable with the substrate carrier about the main axis of rotation and is arranged between the material source and the substrate. The angle of incidence can be limited to acceptably low values via the second aperture. The combination of the two types of diaphragm (first diaphragm and second diaphragm) allows both the course of the layer thickness and the angle of incidence to be specified relatively precisely, so that coatings can be produced with a precisely specifiable effect and high quality. TASK AND SOLUTION

It is an object of the invention to provide a method and a coating system which, with a simplified configuration and process control, make it possible to produce coated optical components with high quality and a precisely specifiable optical effect. Another task is to provide high quality optical components manufactured in this way.

To achieve these objects, the invention provides a method with the features of claim 1 and a coating system with the features of claim 9. Advantageous further developments are specified in the dependent claims. The wording of all claims is incorporated by reference into the content of the description.

The method can be used in the production of optical components, in particular lenses or mirrors. A substrate with at least one curved substrate surface is selected, onto which an optical coating that is rotationally symmetrical with respect to a center of symmetry is applied. This can be, for example, a reflective coating that increases the reflectivity or a reflection-reducing anti-reflective coating. A material source that includes coating material is placed at a source position. The material source can be quasi punctiform (point source) or more or less extensive (area source). Examples of a point source are a thermal evaporator with a material container made of molybdenum or an electron beam evaporator. An example of a surface source is a magnetron sputter source.

A substrate to be coated is attached to a substrate carrier which is rotatable about an axis of rotation of the substrate carrier. The attachment takes place in such a way that when the substrate carrier rotates, the substrate rotates about a substrate axis of rotation coaxial with the substrate carrier axis. Areas of the substrate surface to be coated facing the material source are then coated by coating material originating from the material source at locally varying angles of incidence. Due to the rotation of the substrate, an optical coating can be applied to the substrate surface, which is rotationally symmetrical with respect to a center of symmetry lying on the substrate axis of rotation. A shading screen is arranged between the material source and the substrate carrier, which is suitable for shading parts of the substrate surface in phases (ie over certain time intervals) against coating material originating from the material source during the coating. The shading screen is arranged in a stationary manner with respect to the substrate carrier axis. they should preferably be located near the substrate surface and should not rotate about the substrate support axis. With the aid of the claimed invention, it is possible in principle to produce the optical coating with a predeterminable radial course of the layer thickness or to control the radial course of the layer thickness.

A special feature is that the substrate carrier axis is inclined or inclined relative to a reference direction, so that the substrate carrier axis includes a tilt angle with the reference direction. The reference direction corresponds to the location vector of the center of exchange of the coating material-emitting surface of the material source and the surface of the substrate hit by the coating material. A definition of the location vector of the focus of exchange is given below.

For the phased shading of the substrate surface with respect to the impact of coating material, a shading diaphragm is used which is fixed in relation to the substrate support axis and has a diaphragm cut-out delimited by diaphragm edges, which extends outwards from an inner apex region. The aperture cut-out defines the area of the substrate surface that is not shaded at a given point in time, so that coating material can strike the substrate surface. The shading diaphragm is arranged in such a way that the apex region lies on or near the axis of rotation of the substrate carrier and the diaphragm cut-out includes a region of minimal incidence angles of the coating material on the substrate surface. The vertex area can be a quasi-point-shaped vertex area (vertex) or a somewhat wider area.

Some advantages of this solution are explained below.

According to the inventors' knowledge, the procedure described in DE 102 37 430 A1 (corresponding to US Pat. No. 6,863,398) is suitable in principle for producing optical coatings with high quality and a relatively precisely specifiable optical effect, in particular also on strongly curved optical surfaces.

However, this conventional solution involves shadowing a relatively large proportion of the coating material originating from the material source. This limits the maximum coating rate that can be achieved. For some technically important coating materials, such as aluminum, it is desirable to achieve the highest possible coating rate. As a result, the total duration of a coating process can be restricted to relatively short times, so that for that from the material source to the substrate Coating material that arrives has little time left in the coating chamber to react with any residual impurities that may be present.

The solution proposed here can in principle be used to control the layer thickness and the angle of incidence with a single shading screen per substrate. Although several shading screens can be used per substrate, exactly one shading screen is preferably used for one substrate, in particular for each substrate.

By dispensing with the planetary movement and an arrangement with a tilted axis of rotation of the substrate, a higher proportion of the coating material originating from the material source can also strike the substrate surface of the substrate to be coated and thus, together with dispensing with the second set of diaphragms, the coating rate can be relatively high, in particular maximized.

Due to practically unavoidable mechanical tolerances, the “tip” or the apex or a somewhat wider apex area of the aperture section will not be located or not permanently exactly over the axis of symmetry of the substrate. A defined and homogeneous coating is therefore not or not systematically possible in a central area around the axis of symmetry. This can be seen as a theoretical disadvantage of the proposed solution. In many relevant applications, however, this theoretical disadvantage in practice has no adverse effects on the usability of the optical components coated according to the invention, because in many technically important applications the center of optical components or a central area around the center of symmetry of a rotationally symmetrical coating is not used optically. Examples of this are systems with a central obscuration, e.g. Mirror systems of the type Gregory or Cassegrain. Optical components for these systems can be produced according to the invention or coated in a coating system according to the invention. Another example are optical components which are used in catoptical or catadioptric optical imaging systems with an off-axis object field and image field and are arranged in the vicinity of a field plane of these systems. Here the area optically used by the projection radiation can lie completely outside the optical axis of the system or outside the central area around the center of symmetry.

According to a further development, the method is used to coat an optical component in which, when used as intended, a central area around the center of symmetry of a rotationally symmetrical coating is not optically used. For example such an optical component or its substrate surface have a hole or an opening in the central region.

The material distribution on the substrate surface to be coated can be favorably influenced by a specific setting of the tilt angle. The tilt angle k is preferably set such that the condition

άq ₂ (K)

= 0 (1)

CLK

is at least approximately fulfilled. This clearly means that a tilt angle is set or selected favorably if slight changes in the tilt angle have no or only a very minor effect on the size of the mean angle of incidence.

Clearly or approximately there is a favorable tilt angle if the coating material hits the substrate surface perpendicularly in the middle of the respective coated area.

The shading screen is preferably designed and arranged in such a way that it covers more than half of the substrate surface at all times. This is particularly important for a source that is small compared to the substrate surface. In such a case, the aperture section is designed so that its azimuthal width is less than 180 °. The azimuthal latitude can e.g. 150 ° or less or 120 ° or less. On the other hand, it is generally advantageous not to choose the azimuthal width of the aperture section too small, so that a relatively quick coating can be achieved. The azimuthal width of the aperture section is therefore preferably 90 ° or more. However, narrower aperture sections (less than 90 ° azimuthal width) can be useful in certain cases and should therefore not be excluded

The diaphragm edges can run in such a way that a predeterminable relationship between the radial distance from the substrate axis of rotation and the azimuthal width or angular width in the circumferential direction of the diaphragm segment results for the diaphragm section. The azimuthal width in the circumferential direction can, for example, continuously increase or decrease continuously or increase or remain the same with increasing radial distance from the substrate axis of rotation. The radial course of the layer thickness can be precisely controlled by specifying the functional relationship between the radial distance from the substrate axis of rotation and the azimuthal width of the aperture section. The diaphragm edges can, for example, run in a straight line in a radial direction between the apex or apex region and the outer edge of the shading diaphragm, so that an essentially V-shaped or sector-shaped diaphragm cut-out results. In the case of a V-shaped aperture section with an apex on the substrate axis of rotation, the azimuthal width of the aperture section is the same for all radial distances. With such aperture cutouts, layer thickness profiles can be set in which the layer thickness remains essentially constant in the radial direction.

The diaphragm edges can, for example, also be convexly curved towards one another, so that the azimuthal width increases with increasing radial distance from the substrate carrier axis and possibly increases more than linearly. In this way, for example, layer thickness profiles can be set which have a continuously increasing layer thickness between the center of symmetry and the outer edge. It is also possible to design the bezel edges so that they are concavely curved away from each other. The relationship between the radial distance from the substrate axis of rotation and the azimuthal width then becomes degressive, so that, for example, layer thickness curves with radially continuously decreasing layer thickness can be achieved.

A panel cutout can be designed mirror-symmetrical to a radial plane. However, asymmetrical aperture cutouts are also possible. For example, one of the diaphragm edges can be straight (in the radial direction) and the other curved according to the desired course of the layer thickness.

A shading panel can be essentially flat, e.g. in the form of a flat sheet. The shading diaphragm preferably has a convex or concave curvature, the curvature being adapted to a curvature of the substrate surface. The adaptation should preferably be such that a clear distance between the diaphragm edges that delimit the diaphragm cutout and the substrate surface along the diaphragm edges is approximately constant. This enables a particularly precise control of the course of the layer thickness over the course of the diaphragm edges.

Another possibly important variable is the width of the distribution of the impact angle qz. In the case of technically important vapor deposition materials, such as magnesium fluoride, it is not only the mean impact angle that influences the material properties. In addition, very large angles of impact can have a negative impact on the material properties, which are less likely to occur within a coating cycle. This width of the distribution can be determined by the azimuthal extension of the aperture Affect aperture cutout. An azimuthal extension (width) of 90 ° in typical system geometries means that the maximum angle of incidence is halved compared to an azimuthal extension of the aperture of 180 °.

According to a further development, the substrate carrier axis of rotation remains stationary with respect to the material source during the coating, while the substrate carrier rotates about the substrate carrier axis of rotation. The construction and the kinematics are thus much simpler than in planetary gears, where in addition to the self-rotation of the substrate, there is also a rotation of the substrate carrier with respect to the material source.

In a coating system, this functionality can e.g. can be achieved in that the main carrier, which carries the at least one substrate carrier, is installed stationary in the housing of the recipient. This results in a simple, robust construction, a simple drive system can be used for the substrate rotation and no planetary gear is necessary.

In other embodiments, it is provided that the main carrier, which carries the at least one substrate carrier, is rotatably mounted about an axis of rotation and can be locked in predetermined rotational positions. This makes it possible to bring the next desired substrate carrier into the desired coating position between coating processes by rotating the main carrier, which is then maintained while the coating is being carried out.

Different relative arrangements of material source and substrate carrier (s) are possible. According to a development, at least two substrate carriers are arranged symmetrically with respect to an axis of symmetry and the material source is arranged on the axis of symmetry in such a way that the axis of symmetry runs through the material source. The “symmetrical arrangement” is to be understood here in such a way that the same distances from the material source and the same tilt angle are provided for the substrate carriers. For example, substrate carriers can be arranged in pairs diametrically opposite one another symmetrically to the axis of symmetry. On a main carrier, more than two substrate carriers can also be arranged on a common circle concentrically about an axis of symmetry. The arrangement allows several substrates to be coated at the same time under identical conditions, as a result of which the productivity of the coating process can be increased.

It is also possible that at least two substrate carriers are arranged symmetrically (same distances and tilt angles) with respect to an axis of symmetry that the material source is arranged eccentrically to the axis of symmetry and that the substrates are brought one after the other into a coating position with respect to the material source, a substrate then remaining at the coating position during the coating. In this way, a sequential coating can be implemented, the relative arrangement between the eccentrically arranged material source and the coating position being able to be optimized for exactly one substrate in each case.

The invention also relates to a coating system for coating substrates for optical components, in particular lenses and / or mirrors. The coating system is particularly suitable for coating substrates with curved substrate surfaces. The coating system comprises a recipient with a housing which contains an evacuable coating chamber. In the coating chamber there is a source device for receiving coating material to form a material source in a source position. Furthermore, a main carrier is provided which carries at least one substrate carrier for carrying a substrate. The substrate carrier can be rotated relative to the main carrier about a substrate carrier axis of rotation by means of a drive system.

The invention also relates to an optical component, in particular a lens or a mirror, with a substrate which has at least one curved substrate surface and with an optical coating which is applied to the substrate surface and is rotationally symmetrical with respect to a center of symmetry, the optical component using a method is manufactured or can be produced according to the claimed invention.

In particular, the optical component can have an annular optical useful area which encloses a circular central area containing the center of symmetry of the coating, the rotationally symmetrical optical coating with radially symmetrical optical properties being present in the useful area and the central area having no coating or a coating with non-radially symmetrical optical properties . In the central area, e.g. there is a central opening in the substrate surface or a hole. The diameter of the central area is usually small compared to the outer diameter of the useful area.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and aspects of the invention result from the claims and from the following description of preferred exemplary embodiments of the invention, which are explained below with reference to the figures. 1 schematically shows components of an embodiment of a coating system for coating concave substrates for optical components;

2 shows a shading screen arranged in front of a substrate from the direction of the substrate carrier axis of rotation;

FIGS. 3A, 3B, 3C show an example of some possible configurations of shading shutters together with the radial layer thickness profiles that can be achieved thereby;

FIG. 4 schematically shows components of an embodiment of a coating system, set up for coating convex substrate surfaces;

5 schematically shows components of an embodiment of a coating system with an eccentric material source;

6 shows a graphic to explain some parameters; and

7A, 7B illustrate geometric relationships for determining the reference direction and the tilt angle.

DETAILED DESCRIPTION OF THE EMBODIMENTS

1 schematically shows components of an embodiment of a coating system 100 for coating substrates for optical components. The coating system is an evaporation system with which, among other things, optical components for microlithographic projection exposure systems, in particular also lenses and / or mirrors with strongly curved surfaces, can be coated using the electron beam evaporation process or with other PVD processes, including sputtering. The coating system has a recipient with a housing 102 which encloses an evacuable coating chamber 105. In the lower area there is a source device for receiving coating material, which forms a material source 110, which is arranged in a source position. The expansion of the material source is relatively small compared to the dimensions of the plant. In the case shown schematically, the material source 1 10 is a quasi-point source at the source position 1 12. The source position lies on a vertical axis of symmetry 115 of the coating system. During the coating, the coating material is released essentially symmetrically to this axis of symmetry from the material source upwards in the direction of the arrows shown. At a distance above the material source 1 10, a plate-shaped main support 120 with a horizontal orientation is fixedly mounted in the housing 102 in the example. In the example, the main carrier 120 carries a plurality of substrate carriers 130-1, 130-2, which are each designed to carry a substrate 140 to be coated. In the example, there is a symmetrical arrangement of substrate carriers with respect to the axis of symmetry 115, the schematic sectional illustration showing a pair of substrate carriers 130-1, 130-2 diametrically opposite the axis of symmetry. More than two substrate carriers arranged symmetrically to the axis of symmetry 115 can be provided, for example three, four, five or six.

Each of the substrate carriers can be rotated relative to the main carrier 120 about a substrate carrier axis of rotation 132 with the aid of a drive system 160 which is only shown schematically. The drive system comprises for each substrate carrier a drive shaft 162 which is rotatably mounted in the main carrier 120 and which is rotated on the drive side via a gearwheel and is coupled on the output side to a deflection device 164 which on the output side rotates an output shaft 165 fixedly connected to the substrate carrier about the substrate carrier axis 132. With the aid of the adjustable deflection device, different angles between the orientation of the drive shaft 162 and the output shaft 165 can be set.

The substrate 140 is fastened to the substrate carrier 130 using fastening means (not shown) such that the desired center of symmetry of the coating to be produced lies on the substrate carrier axis 132. In the example, it is a substrate for a concave mirror which has an opening or a hole 145 in the region of its center of symmetry. This results in a ring-shaped optical useful area on this optical component, which surrounds a circular central area containing the center of symmetry, in which no coating has to or cannot be applied. The rotationally symmetrical substrate 140 is therefore characterized by an unused part in the center of the optically used area. As shown in the example, this area can be an opening or an opening in the substrate. However, it is also possible that this area is not used in the intended use of the optical component by the beam path of the optical system for which the optical component is intended, as is the case, for example, with a catadioptric projection objective with central obscuration of the pupil.

A rotationally symmetrical optical coating with radially symmetrical optical properties is to be applied in the useful area. The substrate is attached in such a way that areas of the material to be coated facing the material source Substrate surface 142 can be coated by coating material starting from the material source 110. The coating material strikes the substrate surface at locally varying angles of incidence. The angle of incidence 0 ₂ of the coating material coming from the material source at an impact point P is defined as the angle between the surface normal N at the impact point P and the direction B of the material beam that impinges at the location P (see detail in FIG. 1) 1 immediately recognizable that the angles of incidence vary locally due to the geometry of the system and the geometry of the substrate surfaces to be coated.

For each substrate or each substrate holder, a single shading screen 150 is provided which is assigned to the substrate carrier and, in the example, is mounted in a stationary manner on the main carrier 120.

The substrate carrier axis of rotation 132 is not aligned parallel or perpendicular to the axis of symmetry 115, but rather is inclined. The extent of the inclination can be optimized specifically for the type of substrate or for the curvature of the substrate surface to be coated and can be set on the deflection device 164. For this purpose, a reference direction 138 is determined. In the procedure explained in more detail below, this corresponds to the location vector of the so-called exchange center of gravity of the emitting surface of the material source 110 and the surface hit by the coating material on the substrate surface 142 (cf. FIGS. 6 and 7). The area hit by the coating material at a given time corresponds to the area that is not shaded by the shading screen 150 at the time. The substrate carrier axis of rotation 132 is not aligned parallel to this reference direction 138, but rather at an angle to it, so that the substrate carrier axis of rotation is inclined at a tilt angle k with respect to the reference direction.

2 shows a shading screen arranged in front of a substrate from the direction of the substrate carrier axis of rotation. To determine the area that can be hit by the coating material at a given time, the shading diaphragm 150 is designed such that it has a diaphragm cutout 158 which is delimited in the circumferential direction by diaphragm edges 155-1, 155-2 and extends from an inner apex 152 in Radial direction extended and extends outwards. The shading screen is stationary with respect to the substrate support axis of rotation 132 and is arranged such that the apex 152 lies on or near the substrate support axis of rotation 132 and the screen cutout 158 includes a region of minimal angles of incidence of the coating material on the substrate surface. By combining these measures, the control or specification of the layer thickness or the radial layer thickness profile and the angle of incidence is achieved with a single shading screen 150 per substrate. By dispensing with the planetary movement provided in some conventional systems and an arrangement with a tilted axis of rotation of the substrate, a higher proportion of the coating material originating from the material source 110 can also hit the substrate, so that high coating rates can be achieved. There is no need for additional screens to limit the angle of incidence.

3A, 3B and 3C, examples of some possible configurations of shading shutters are shown together with the radial layer thickness profiles that can be achieved thereby. The figures each show a shading aperture geometry on the left and a diagram of the (normalized) layer thickness SD between center Z and edge D of the substrate surface on the right.

The shading aperture in FIG. 3A has an aperture cutout in the form of a V-shaped circular sector, so that a corresponding sector-like cutout of the substrate surface is exposed for the coating at all times. The diaphragm edges 155-1, 155-2 run in a straight line along corresponding radial directions. This results in a specific relationship between the radial distance from the substrate axis of rotation and the azimuthal width or the angular width in the circumferential direction of the aperture section for the aperture section. In the case of the diaphragm edges running straight in the radial direction from FIG. 3A, the azimuthal width B is constant irrespective of the radial distance. This enables an almost constant course of the layer thickness in the radial direction to be achieved (see diagram on the right). There may be slightly larger deviations in the percentage range near the center of the substrate and at the edge of the substrate. These can be compensated for by appropriate deviations from the straight course of the diaphragm edges.

If, for example, a parabolically increasing layer thickness is required between the center of the substrate and the edge of the substrate, this can be achieved by adapting the radial contour of the aperture section of the shading aperture. 3B shows an example of a shading diaphragm, in which the diaphragm edges are convexly curved toward one another, so that the angular width (azimuthal width) in the circumferential direction of the diaphragm section initially increases slowly and then disproportionately more strongly. It is immediately understandable that, by appropriately designing the diaphragm edges, a correction of remaining deviations from uniform layer thickness distributions in the vicinity of the center and at the edge of the substrate is possible. In the apex area, the aperture cutout is not tapered to a point, so that (as in FIG. 3A) a punctiform apex area (apex) results, but rather widens. The maximum diameter of the apex region is preferably less than or equal to the diameter of that central region of the substrate in which no rotationally symmetrical coating is required. This area is given here by the circular opening 145 in the substrate.

If a decreasing layer thickness between the center and the edge of the substrate is required, this can be achieved by correspondingly adapting the radial contour of the aperture cutout in the shading aperture, for example by means of aperture edges of the type shown in FIG. 3C, which are concavely curved away from one another. The width of the aperture section measured in the azimuthal direction gradually decreases from the center (substrate axis of rotation) in the direction of the edge.

Numerous variants of the system structure and the panel geometries are possible. 1 shows a configuration for coating concave substrates, for example. Similarly, the geometry can also be adapted for the coating of convex substrates. 4 shows an example of a coating system 400. Components with the same or similar function or the same or similar structure as in FIG. 1 are shown with the same reference numerals. The tilting of the substrates is directed outwards.

It can be technically advantageous to position the material source decentrally in the coating system. FIG. 5 shows an exemplary embodiment of a coating system 500, which can be viewed as a modification of FIG. 1. The same or corresponding features have the same reference numerals as in FIG. 1. The material source 1 10 is not on the axis of symmetry 1 15, but laterally offset from it at a distance from it. A coating of several substrates with identical coating conditions is then no longer possible as long as the substrates only rotate about their own axis of symmetry (substrate axis of rotation). A continuous rotation of the substrate on a pitch circle, which lies above the material source (as in conventional planetary systems) is considered disadvantageous because of the coating rate that can be achieved as a result. FIG. 5 illustrates an advantageous solution, in which the substrate carriers are carried by a main carrier 120, which is rotatably mounted, wherein the rotation about the axis of symmetry 115 can take place. However, the rotatable main beam is not rotated continuously. Rather, the rotatability serves only to switch from one substrate to the next substrate to be coated between two coating processes. With the help of the rotatable main carrier 120, substrates can thus be successively brought into a coating position above the material source 110, where they remain stationary during the coating. In the example of FIG. 5, the drive of the substrate rotation about the respective axis of symmetry (substrate rotation axis) via gearwheels 166, 168 is independent of the rotation of the main carrier 120. For this purpose, the gearwheel 166 is not fixed in the coating chamber, but can be driven independently of the main carrier . If a simple shading screen 150 only ever permits coating of the one substrate located directly above the material source, the substrates can be coated in succession at a high coating rate.

Some parameters that are important for understanding the concept presented here are explained below.

The average angle of incidence q ₂ (see definition in Eq. 5) influences the properties of the material of the coating applied to the optics or to the substrate surface 142. For most materials, high mean angles of incidence lead to layer growth with a low density of the material up to low mechanical stability. By changing the tilt angle (see definition in Eq. 4) the average impact angle can be changed. By choosing a tilt angle with

(1 )

the mean angle of incidence is advantageously determined.

For surface sources, the average angle of incidence depends not only on the tilt angle, but also on the size of the material source, i.e. the area Ai, and the average distance \ r _H \ of the source from the optics. By choosing

(1 .1)

given the area of the material sources, the mean angle of incidence is also advantageously determined. Conditions (1) and (1.1) can advantageously also be used in combination.

Definition of the tilt angle in the case of a homogeneous surface source

The sizes listed below are shown graphically in FIGS. 6 and 7A, 7B. The area A2 (cf. FIG. 6) is the partial area of the optically used area of the optics or the substrate that is not covered by the shading screen 150 or the holder.

\ r (dA _{1, d} A ₂₎ \ is the length of the connecting line between the surface element dAi in the material source 110 with the emitting surface Ai and surface element dA2 in the surface A2, that is to say the surface hit by the coating material on the substrate surface of the optics. n (dAi) and n (dA2) are the vectors of the surface normals in the surface element dAi and C / A2.

The view factor F _I ^ 2 between the areas Ai and A2 known from the description of the radiation exchange is defined as:

G _H is the location vector of the exchange center of the emitting surface Ai. and the area hit by the coating material on the optics / and described by:

T _D is the direction vector of the substrate carrier axis of rotation 132. The tilt angle k is the angle between G _H and ro according to Eq. 4:

Definition of the average impact angle q ₂ in the case of a homogeneous surface source

Analogous to the definition of the exchange focus, an average impact angle can be defined:

Definition of tilt angle and mean angle of impact in the case of a point source The concept of a point source is an idealization that cannot really be implemented. Therefore, it makes sense to treat the point source as an area source with a correspondingly smaller emitting area Ai.

Definition of the tilt angle in the case of a homogeneous surface source with any source characteristic and any condensation characteristic

In technically important applications, such as an electron beam evaporator, the radiation characteristics of the source can differ from the behavior described by (2). This deviation of the source characteristic can be described by a dimensionless distribution function Pi (ft) standardized to one. Likewise, the condensation characteristic, ie the probability that coating material is deposited on the substrate surface, can differ from the behavior from (2). This deviation in the condensation characteristic can also be described by a distribution function P2 {fc). The visual factor is then changed accordingly (6).

The definitions of the exchange focus (3) and the mean impact angle (5) change in the same way.

It can be seen that the exchange center of gravity is not identical to the direction which corresponds to a minimum mean angle of incidence. Mathematically, both the center of exchange and the mean angle of impact are expected values with regard to a distribution function from Eq. (2). The minimum average impact angle is established when the variation of the tilt angle leads to a minimum in the average impact angle.

Claims

1. A method for producing an optical component, in particular a lens or a mirror, in which a substrate with at least one curved substrate surface is selected and an optical coating which is rotationally symmetrical with respect to a center of symmetry is applied to the substrate surface, wherein the following steps are carried out for coating the substrate will:

Arranging a material source (1 10) comprising coating material in a source position;

Arranging the substrate (140) on a substrate carrier (130) rotatable about a substrate carrier axis of rotation (132) such that the substrate rotates about a substrate axis of rotation coaxial with the substrate carrier axis of rotation when the substrate carrier is rotated, areas of the substrate surface (142) to be coated passing through the material source coating material originating from the material source can be coated at locally varying angles of impact (Gh);

Arranging a shading diaphragm (150) between the material source (110) and the substrate carrier for phased shading of parts of the substrate surface (142) against coating material originating from the material source during the coating;

characterized in that

the substrate carrier axis of rotation (132) is inclined relative to a reference direction (138) such that the substrate carrier axis of rotation includes a tilt angle (K) with the reference direction;

a shading diaphragm (150) is used, which has a diaphragm cutout (158) delimited by diaphragm edges (155-1, 155-2) and extends outwards from an inner apex region, and

the shading screen is arranged in a stationary manner with respect to the substrate carrier such that the apex region lies on or near the substrate carrier axis of rotation (132) and the panel cutout (158) includes a region of minimal incidence angles of the coating material on the substrate surface.

2. The method according to claim 1, characterized in that exactly one shading diaphragm (150) is used for a substrate.

3. The method according to claim 1 or 2, characterized in that an optical component is coated, in which a central region around the center of symmetry of the rotationally symmetrical coating is not optically used in the intended use.

4. The method according to any one of the preceding claims, characterized in that the tilt angle (K) is set such that the condition

is approximately fulfilled.

5. The method according to any one of the preceding claims, characterized in that the substrate carrier axis of rotation (132) remains stationary during the coating with respect to the material source (1 10), while the substrate carrier (130) rotates about the substrate carrier axis of rotation (132).

6. The method according to any one of the preceding claims, characterized in that at least two substrate carriers (130-1, 130-2) are arranged symmetrically with respect to an axis of symmetry (1 15) and that the material source (1 10) on the axis of symmetry (1 15) is arranged such that several substrates are coated simultaneously under identical conditions.

7. The method according to any one of the preceding claims, characterized in that at least two substrate carriers (130-1, 130-2) are arranged symmetrically with respect to an axis of symmetry (1 15), that the material source (110) eccentric to the axis of symmetry (1 15 ) and that the substrates (140) are successively brought into a coating position with respect to the material source, a substrate remaining at the coating position during the coating.

8. The method according to any one of the preceding claims, characterized in that on the substrate surface (142) a rotationally symmetrical to the substrate axis of rotation coating is generated, starting from the substrate axis of rotation a substantially constant layer thickness, a continuously increasing in the radial direction or a continuously decreasing in the radial direction layer thickness having.

9. Coating system (100, 400, 500) for coating substrates for optical components, in particular for coating substrates with curved substrate surfaces, the coating system with:

a recipient with a housing (102) which contains an evacuable chamber (105) which comprises: source means for receiving coating material to form a material source (1 10) in a source position;

a main carrier (120) which carries at least substrate carrier (130) for carrying a substrate (140),

wherein the substrate carrier is rotatable about a substrate carrier axis of rotation (132) relative to the main carrier by means of a drive system (160) and is arranged in such a way that regions of the substrate surface (142) to be coated, facing the material source (142), of a substrate carried by the substrate carrier are emitted by the material source Coating material can be coated at locally varying angles of impact (Q2);

a shading screen (150) assigned to the substrate carrier between the material source (110) and the substrate carrier (132) for phased shading of parts of the substrate surface (142) against coating material emitted by the material source during the coating; in which

the substrate carrier axis of rotation (132) is inclined relative to a reference direction (138) in such a way that the substrate carrier axis of rotation includes a tilt angle (K) with the reference direction;

the shading diaphragm (150) has a diaphragm cutout (158) delimited by diaphragm edges (155-1, 155-2), which widens outwards from an inner apex region and

the shading diaphragm (150) is arranged in a fixed manner with respect to the substrate carrier axis of rotation such that the apex region lies on or near the substrate carrier axis of rotation (132) and the diaphragm cutout (158) includes a region of minimal angles of incidence of the coating material on the substrate surface.

10. Coating system according to claim 9, characterized in that the diaphragm edges (155-1, 155-2) run symmetrically with respect to a radial direction.

1 1. Coating system according to claim 9 or 10, characterized in that the diaphragm edges (155-1, 155-2) run such that there is a predetermined relationship between a radial distance to the substrate axis of rotation (132) and the for the aperture cutout (155) azimuthal width (B) of the aperture section (155) results, with at least one of the following conditions:

the azimuthal width (B) in the circumferential direction increases or decreases continuously with increasing radial distance or remains constant;

the azimuthal latitude (B) is less than 180 °;

the azimuthal latitude (B) is 150 ° or less and / or 90 ° or more.

12. Coating system according to one of claims 9 to 11, characterized in that the diaphragm edges (155-1, 155-2) between the apex region and an outer edge of the shading diaphragm each extend in a radial direction, curved convexly towards one another or concavely away from one another are.

13. Coating system according to one of claims 9 to 12, characterized in that the shading diaphragm (150) has a convex or concave curvature, the curvature being adapted to a curvature of the substrate surface, preferably in such a way that a clear distance between the diaphragm edges (155- 1, 155-2) and the substrate surface (142) is approximately constant.

14. Coating system according to one of claims 9 to 13, characterized in that the substrate carrier is mounted on a stationary or stationary lockable main carrier (120), so that the position of the substrate carrier axis remains constant in space during the coating.

15. Coating system according to claim 14, characterized in that the main carrier (120), which carries the at least one substrate carrier, is installed in the housing (102) of the recipient in a stationary manner or that the main carrier, which carries the at least one substrate carrier, is rotatable about an axis of rotation is stored and can be locked in predetermined rotational positions.

16. Coating plant according to one of claims 9 to 15, characterized in that the source of the coating material is an approximately point source or a surface source.

17. Optical component, in particular lens or mirror, with a substrate which has at least one curved substrate surface and with an optical coating which is applied to the substrate surface and is rotationally symmetrical with respect to a center of symmetry,

characterized in that

the optical component is produced or can be produced by means of a method according to one of claims 1 to 8.

18. Optical component according to claim 17, characterized in that the optical component has an annular optical useful area which encloses a circular central area containing the center of symmetry, the rotationally symmetrical optical coating with radially symmetrical optical properties being present in the useful area and the central area having no coating or Has coating with non-radially symmetrical optical properties.