Method for producing a transparent, scratch-resistant component

Abstract

The invention relates to a method for producing a transparent, scratch-resistant component, comprising the following steps: providing a planar substrate transparent to visible light and made of glass, in particular silica glass, having a metal film on its upper face; growing a diamond layer on the upper face of the planar substrate by chemical vapour deposition, in particular a microwave plasma chemical vapour deposition (MPCVD) method, or a hot filament CVD (HFCVD) method.

Description

[0001] Process for producing a transparent, scratch-resistant component

[0002] Description

[0003] The invention relates to a method for producing a transparent, scratch-resistant component (embodiment variant 1) and a method for producing a diamond disc (embodiment variant 2).

[0004] The object of the invention is to provide methods that enable the efficient production of a transparent, scratch-resistant component and a diamond disk.

[0005] This object is achieved by the features of the independent claims. The dependent claims show preferred embodiments of the invention.

[0006] Thus, the invention shows a method for producing a transparent, scratch-resistant component (embodiment variant 1), comprising at least the following steps:

[0007] (i) Providing a carrier disk made of glass, in particular quartz glass, which is transparent to visible light and has a metal film on the upper side. The metal film can be described as catalytically functional. The carrier disk thus consists in particular mainly of silicon oxide, although further materials can be added, for example, to change the expansion coefficient - this will be described in more detail. Preferably, the method also comprises applying the metal film to the upper side of the carrier disk. The metal film can in particular be applied in crystalline form and / or applied amorphously and crystallized, in particular by an annealing process. The annealing process will be explained in more detail later with reference to copper and nickel.

[0008] (ii) Furthermore, the process involves growing a diamond layer on the upper side of the carrier disk by means of chemical vapor deposition, also known as a CVD process or chemical vapor deposition process. In particular, a microwave plasma chemical vapor deposition (MPCVD) process or a hot filament CVD (HFCVD) process is used. This process step is carried out in particular in a device for carrying out chemical vapor deposition. The finished component thus comprises the carrier disk and the diamond layer firmly bonded to it. Such a component can be used, for example, as a watch glass or as a screen for a smartphone.

[0009] The invention shows the ideal variant of a transparent, scratch-resistant component (e.g. a magnifying glass) as the direct combination of a carrier disc, which harmonizes with the diamond in terms of expansion coefficient, and a diamond layer made of synthetic diamond applied directly to it using the CVD process.

[0010] Within the scope of the invention, it was recognized that a polycrystalline diamond layer, which is usually based on an initiation process using DND (detonation nanodiamonds), has the disadvantage of exhibiting extremely high optical scattering on the nucleation side, i.e., at the point of the diamond layer where the first randomly scattered diamond grains of very small size (5 nm to 40 nm) initiate the growth process. With an average size of 20 nm, 2 billion, 500 million diamond particles fit into one square millimeter. When this layer of individual crystals begins to grow in all possible directions using the CVD process, a "seed layer" initially forms, which is highly fragmented and therefore not fully optically transparent.As the diamond layer grows, the number of nucleation cells decreases, as those diamond crystals growing perpendicular to the carrier wafer in a strong growth direction overtake and displace their sister cells. Thus, the situation improves with increasing layer thickness. The bottom layer, the nucleation side, would then have to be ground away to obtain a visually appealing product. However, when such a polycrystalline layer is grown directly onto a final substrate (carrier wafer according to the present invention), this nucleation layer cannot be removed, as it is grown directly on the carrier wafer, which is intended to remain a component of the component.

[0011] Within the scope of the invention, it was recognized that a metal film on the upper side of the carrier disk enables the growth of an optically perfectly transparent diamond disk. This will be discussed in more detail below using a metal film made of nickel; however, these considerations also apply to a metal film made of copper, for example.

[0012] For diamond to grow using the CVD process, a crystallization nucleus, a so-called "seed," is first required that is similar to or identical to the diamond crystal lattice. These nuclei are typically made of diamond themselves. Diamond would not grow on pure quartz glass using the CVD process. For this purpose, the metal film is preferably impregnated with diamond powder and / or diamond-like nuclei.

[0013] Diamond has a face-centered cubic crystal lattice. Other materials also possess such a crystal lattice, such as silicon or some metals such as nickel and copper. However, for such a material to have a positive influence on diamond film growth, the unit cell of the face-centered cubic crystal lattice would have to be approximately the same as that of diamond, not only in terms of structure but also in terms of size. For example, the unit cell of silicon has a size of 5.43 Å (angstroms), while that of diamond has a size of 3.57 Å.

[0014] Since both nickel and silicon have a cubic unit cell in their crystal lattice, certain nickel-silicon compounds also have a cubic unit cell. The unit cell of NisSi is also very similar in size to that of diamond (3.506 Å).

[0015] To grow synthetic diamond onto a non-diamond substrate, very fine diamond powder is often used, which still retains the diamond's original crystal structure. Typically, DND (Detonation Nano Diamond) powder with a grain size of approximately 5–40 nm is used; this powder is created during an explosion of a TNT / RDX mixture in a sealed pressure chamber. However, there are other processes for producing crystalline diamond powder. The method of producing diamond powder by grinding synthetic or natural diamond would not be particularly suitable for this application as a seed cell, as this primarily produces fragments rather than intact diamond crystals. The fine diamond powder is then applied to the substrate, which has previously been thoroughly cleaned with acetone and various alcohols, using a suitable solvent.There are various methods for this, such as the use of ultra-fine 3D printing systems, systems for applying lithographic layers to wafers for the semiconductor industry, etc. After the substrate is impregnated, it is placed in a CVD reactor. In the plasma process, the diamond crystals grow in their typical crystal lattice structure by depositing carbon from methane gas. However, such a process for the production of transparent components would not lead to effective results without modification, as the optical quality would not meet the requirements of, for example, a high-quality watch glass. The high light scattering in a polycrystalline quartz glass substrate grown with synthetic diamond would produce such a strong gray haze in the diamond layer that the product would be unsuitable for a watch glass.

[0016] The present invention now proposes a modification of this process in that at least one film is installed between the carrier disk and the diamond layer, which film brings the completely diffuse polycrystalline character of the growth layer of diamond into an ordered system with an orientation of the growth direction, which can ultimately be described as monocrystalline, or as "quasi-monocrystalline", which on the other hand bridge the problem of the different expansion coefficients of diamond and quartz glass and which, after fulfilling their task, optically disappear again or are / become invisible.

[0017] For example, nickel - but also copper - are ideal materials for this purpose, for the following reasons:

[0018] (1 ) The crystal lattice structure of nickel, copper and iridium is also face-centered cubic like silicon and diamond.

[0019] (2) The size of the unit cell, i.e., the basic atomic cell, corresponds to that of the diamond unit cell for nickel and copper, with a deviation of only slightly more than 1%. The nickel unit cell has a size of 3.52 Å, that of diamond has a size of 3.57 Å, and that of copper 3.615 Å. Due to surface tension, the diamond crystals are deposited very densely and with a better-ordered crystal lattice orientation on the nickel or copper layer during the impregnation process (application of the diamond powder). It is advantageous for this to occur if the nickel or copper film has already been deposited in an orderly manner with the correct orientation on the carrier disk.

[0020] When nickel and copper layers are applied as thin films to substrates that do not match the structure of pure nickel or copper, layers of these two materials tend to become structured during a subsequent "annealing" process. Various types of structures occur depending on the temperature, duration of the annealing process, and the substrate to which the layers are applied. Face-centered cubic unit cells in an ordered orientation are the ideal structure for the subsequent growth of monocrystalline diamond. However, fiber structures also occur in which individual groups of unit cells can reach up to 500 times the size of a single unit cell. Such structures are not suitable for our application.

[0021] In addition to the annealing process, there are other methods to induce the face-centered cubic structure of copper or nickel films in an ordered orientation, such as ion bombardment, BEN (Bias Enhanced Nucleation) methods, and others.

[0022] The first step is therefore the application of a metal film (especially made of Ni or Cu), particularly using a sputtering process, e-beam, vapor deposition, or another suitable method. As a second step, an annealing process is advantageous, for example, heating under a protective gas such as argon, usually under reduced pressure, or another suitable process for crystallographic structuring of the metal layer.

[0023] In particular, these two steps can also be combined into one by applying the metal film at a sufficiently high substrate temperature.

[0024] An ordered crystal structure of the metal film is a preferred prerequisite for the orientation of the growth direction of the diamonds during seeding with diamond crystals, for example, preferably in the (1 10) direction, which then corresponds to the (220) or the (1 10) orientation in nickel.

[0025] Diamond not only has exceptional hardness, but also a very high surface energy. A high surface energy means that a material has a strong tendency to attract other molecules. The surface energy varies depending on the crystallographic orientation of the surface of the diamond crystal lattice.

[0026] The varying surface energies according to the different orientation planes result in different cohesion values ​​for diamond. Nickel also has a high surface energy value. In nickel, this value also varies depending on the crystallographic orientation in the face-centered cubic crystal lattice.

[0027] If diamond nanocrystals are applied in the correct manner to a nickel substrate (metal film) which is crystallographically clearly oriented, then the diamond nanocrystals arrange themselves in such a way that certain orientation planes of the diamond crystals coincide with the corresponding orientation planes of the cubic nickel structure.

[0028] Nickel is a metal that, during the diamond growth process in the CVD chamber, bonds with the substrate (quartz glass) beneath the nickel under the influence of the plasma above the nickel layer and at temperatures between 700°C and 1150°C (preferably between 900°C and 1000°C). This means that at these high temperatures, nickel diffuses into the substrate, partially replacing silicon atoms and partially forming NiSi or NiSi2 compounds, which in turn are ultimately absorbed and dissolved in the quartz glass.

[0029] This absorption of the nickel layer has several advantages. First, the nickel layer disappears and is not visually disturbing. While a very thin nickel layer would be barely visible to the naked eye, the opaque nickel would further enhance the component's gray haze. Second, the diffusion of nickel atoms into the quartz glass creates a kind of "nickel glass" at the interface between the quartz glass and the diamond layer. The coefficient of thermal expansion of this layer is no longer 0.45 x 10 -6 K -1 like pure quartz glass, but a little more.

[0030] A direct coating of quartz glass (or other glass) carries the risk of stress cracking not only due to the difference in the expansion coefficient at normal temperature, but especially during cooling from the operating temperature in the CVD process (approximately 950°C). Diamond has an expansion coefficient of 4 x 10-6 K -1 at a temperature of 1000°C and an expansion coefficient of 1 x 10 -6 K -1 at room temperature, especially 25°C. In contrast, the expansion coefficient of quartz glass hardly changes at different temperatures.

[0031] This means that the diamond layer will normally flake off the quartz glass during cooling after the CVD process. However, even if the tension between the diamond layer and the quartz glass does not cause the diamond layer to flake off immediately after the CVD process, the risk of glass breakage is by no means eliminated.

[0032] The reason for this is the extreme susceptibility of glass, and even quartz glass, to microcracks. At some point, a microscopically small crack may develop in a stress zone. If the area surrounding this crack is under stress, the crack will grow over time, eventually merging with neighboring cracks and, in the long term (possibly even after years), leading to the flaking of the diamond layer.

[0033] From the above considerations and various experiments, the following features of the process have proven to be advantageous:

[0034] Preferably, the metal film comprises nickel and / or copper. Preferably, more than half, in particular entirely, of the metal film consists of at least one of these metals. An alloy of two of these metals, in particular copper and nickel, has also proven advantageous for the metal film.

[0035] Nickel and copper are better suited for the metal film for the following reasons:

[0036] 1) The edge length of a unit cell of nickel and copper differs slightly, in particular less than 2.5%, from the edge length of a unit cell of diamond. Since the diamond powder on the oriented metal film is supposed to align itself according to the crystal lattice of the metal film via its surface tension, it has been found that the unit cell size should be more or less the same. This is the case with copper and nickel. 2) The transparency of the coated substrate depends largely on the diffusion of the metal film into the glass (quartz glass). The diffusion of the metal layer into the quartz glass is a process in which the metal oxidizes due to the silicon-oxygen compound (quartz glass SiO2). In this way, the nickel, for example, tears one or two oxygen atom(s) from the glass and deposits itself in the quartz glass in a type of oxidation process, or replaces a silicon atom in the long Si-O2 chains, or squeezes itself in somewhere.Nickel or copper oxidize better than platinum or iridium and therefore diffuse better into quartz glass than platinum or iridium because the bond between Si and O2 is stronger than the bond between platinum and oxygen or iridium and oxygen.

[0037] In addition to experiments, the following considerations also played a role in the selection of metals:

[0038] Diamond: unit cell with 3.57 angstroms;

[0039] Nickel: Unit cell with 3.52 Å and a difference to diamond of 0.05 angstroms; melting point: 1455 °C.

[0040] Copper: unit cell with 3.615 Å and a difference to diamond of 0.045 Å; melting point: 1083 °C.

[0041] Iridium: Unit cell with 3.833 Å and a difference to diamond of 0.26 Å; melting point: 2446 °C.

[0042] The high melting point of iridium means that annealing a thin iridium film on the surface of quartz glass in the same way as is possible with copper or nickel is difficult because the melting point of quartz glass is significantly lower.

[0043] Iridium is also not really excellent in terms of unit cell size compared to diamond (3.833 Å).

[0044] A metal film made of nickel or copper is particularly well suited for growth on quartz glass, since the size of the unit cell of the face-centered cubic crystal structure is very similar to that of diamond.

[0045] A Cu-Ni alloy is also preferably used as the metal film; in particular, with a deviation of the size of the cubic unit cell of only 0.025 Angstroms compared to the size of the cubic unit cell of diamond.

[0046] Since the metal film is intended to diffuse into the quartz glass after the initial crystallization of diamond and thus dissolve, pure copper is particularly preferred, as it has the highest diffusion coefficient in quartz glass of all the materials mentioned. Preferably, the metal film has a thickness of no more than 30 nm, preferably no more than 20 nm, and more preferably no more than 10 nm, prior to diamond growth; preferably, the metal film has a thickness of at least 2 nm. During growth, the metal film can then partially or completely diffuse into the carrier disk and thus disappear.

[0047] Preferably, the metal film has a thickness between 5 nm and 20 nm before diamond growth, more preferably between 5 nm and 10 nm, especially 5 nm. A thin metal film orients better in an annealing process than a thick metal film, and a thin metal film also diffuses away more quickly than a thick metal film. Due to its low thickness, the metal film can diffuse substantially completely or entirely into the carrier wafer. "Substantially completely" means in particular a diffusion of at least 80%, preferably of at least 90%, and less than 100%, which of course denotes complete diffusion. As the metal film diffuses into the carrier wafer, the metal film disappears.

[0048] Preferably, the diamond layer after growth has a thickness of at least 30 pm and / or a maximum of 2 mm.

[0049] It is particularly preferred that the diamond layer as a cover disk has a thickness of at least 10 pm and / or a maximum of 0.5 mm after growth.

[0050] Preferably, the carrier disc has an expansion coefficient of 0.45 x 10 -6 K -1 up to 1.2 x 10 -6 K -1 , preferably 0.8 x 10 -6 K -1 up to 1.2 x 10 -6 K 1 , has.

[0051] With regard to the different expansion coefficients, a certain buffer between the two layers, or at least a modification of the quartz glass, is advantageous.

[0052] Nowadays, many parameters of the glass can be changed by adding additives to it, especially the coefficient of expansion, the softening temperature, the melting point, etc.

[0053] Quartz is the basic material for glass. In the extremely numerous varieties of glass, a portion of the silicon atoms is usually replaced by atoms of one or more other elements. For example, a good lead crystal glass consists of up to 75% lead oxide, a good silver crystal glass of up to 50% silver oxide, etc. Glass can absorb many metals by replacing silicon atoms with foreign atoms. In this case, the coefficient of expansion changes and, in most cases, becomes larger. Most types of glass have a coefficient of expansion of between 6 x 10 -6 K -1 up to 9 x 10 -6 K -1 , which is 12 to 20 times the coefficient of expansion of quartz glass. There are various approaches to solving the problem of diamond's temperature-dependent, extremely different coefficient of expansion at different temperatures:

[0054] The carrier disk (or carrier glass) can be adjusted so that it also has a significantly higher coefficient of expansion at higher temperatures and a coefficient of expansion like diamond at room temperature. The carrier disk would then exhibit a temperature-dependent expansion profile similar to diamond, and no stresses would arise during cooling after the CVD process.

[0055] Another method would be a carrier disc (or a carrier glass) which also has an expansion coefficient of 4 x 10 -6 K -1 but then crystallizes in a very specific way upon cooling, so that at room temperature it resembles quartz glass and thus also diamond in its coefficient of expansion. In particular, the carrier disc can be made of a glass which:

[0056] • has a softening temperature between 500 °C and 650 °C, in particular 550 °C, and / or

[0057] • has a temperature-dependent, variable expansion coefficient, which is 3.9 x 10 -6 K -1 up to 4.1 x 10 -6 K -1 , especially 4 x 10 -6 K -1 , and from 0 °C to 100 °C, especially at 25 °C, 0.9 x 10 -6 K -1 up to 1.1 x 10 -6 K- 1 , especially 1 x 10 -6 K -1 , and / or

[0058] • has a chemical composition which has an expansion coefficient of 3.9 x 10 -6 K -1 up to 4.1 x 10 -6 K -1 , especially 4 x 10 -6 K' 1, and when cooling from the operating temperature of the CVD process, undergoes a crystallization process, which causes the expansion coefficient to be 0.9 x 10 -6 K -1 up to 1.1 x IO 6 K- 1 , especially 1 x 10 -6 K 1 , and / or

[0059] • Contains alkalis and / or metals.

[0060] Another method would be a type of "solder glass." Solder glass is used to bridge the different expansion coefficients of metals and glass. Solder glass is so "permanently soft" that it can bond to metal and any type of glass simultaneously without cracking. Such a glass could therefore bind the diamond layer on one side and the carrier glass on the other like an elastic adhesive. Such a glass would therefore be an adhesion promoter that could be placed between a carrier glass on the one hand and a diamond layer on the other. Additional film While a glass with a similar expansion profile to diamond would have to be developed first, solder glass already exists in all possible variants. An advantageous solution to the problem is to melt an additional film made of a suitable solder glass as an overlay onto the quartz glass and to apply the metal film to the overlay made of glass with a variable expansion coefficient.

[0061] Preferably, the metal film is applied by vapor deposition, cathodic sputtering, electron beam evaporation, or an electrolytic process. The metal film should be applied to the carrier wafer with as uniform a thickness as possible.

[0062] Preferably, the metal film is brought into a defined crystallographic orientation by annealing during or after application.

[0063] Preferably, prior to growth, a diamond powder is applied to the metal film, in particular with a grain size of 5 nm to 40 nm. In particular, this is carried out by the following steps: applying a mixture of a liquid with diamond powder to the metal film and removing the liquid, in particular by centrifugation and / or evaporation.

[0064] Preferably, the metal film is almost completely, particularly completely, diffused into the carrier wafer by thermal action during chemical vapor deposition. At a temperature of between 900 °C and 1000 °C, approximately 950 °C, and a residence time of 19 to 30 hours, the metal film, particularly the nickel film, disappears more or less completely, especially if it was only 5 nm thick.

[0065] It is preferably provided that an additional film of mineral material, preferably with silicon or synthetic material, is located between the metal film and the carrier disk before growth.

[0066] It is preferably provided that an additional film made of mineral material, preferably with silicon or synthetic material, is located between the metal film and the carrier disc.

[0067] It is particularly preferred that the additional film has a thickness of at most 0.5 mm, preferably at most 0.4 mm, more preferably at most 0.3 mm.

[0068] In particular, the additional film is melted onto the carrier wafer. This can preferably be done before the metal film is applied to the carrier wafer or the additional film.

[0069] Preferably, the additional film may comprise alkalis or other metals in such quantities that the probability of the diamond layer grown on the additional film not chipping off upon cooling from the softening temperature of the additional film to room temperature by withstanding the tensile stress on the diamond side that arises during cooling in the long term.

[0070] According to an advantageous embodiment, the additional film

[0071] • an expansion coefficient between 1.8 x 10 -6 K -1 and 2.2 x 10 -6 K1 , especially 2 x 10 -6 K -1 or have a temperature-dependent, variable expansion coefficient which is 3.9 x 10 -6 K -1 up to 4, 1 x 10 -6 K -1 , especially 4 x 10 -6 K' 1 , and from 0 °C to 100 °C, especially at 25 °C, 0.9 x 10 -6 K -1 up to 1.1 x IO 6 K- 1 , especially 1 x 10 -6 K 1 , amounts,

[0072] • and / or

[0073] • have a softening temperature between 500 °C and 650 °C, in particular 550 °C,

[0074] • and / or

[0075] • have a chemical composition which has an expansion coefficient of 3.9 x 10 -6 K -1 up to 4.1 x 10 -6 K' 1 , especially 4 x 10 -6 K 1, and when cooling from the operating temperature of the CVD process, undergoes a crystallization process, which causes the expansion coefficient to be 0.9 x 10 -6 K -1 up to 1.1 x 10 -6 K' 1 , especially 1 x 10 -6 K 1 , and / or

[0076] • Contain alkalis and / or metals.

[0077] It should be understood that the additional film and the carrier disc are made of different materials.

[0078] As described above, the method comprises providing a carrier disk made of glass, in particular quartz glass, which is transparent to visible light and has a metal film on the upper side, preferably also applying the metal film to the upper side of the carrier disk, and growing a diamond layer as a cover disk on the upper side of the metal layer by means of chemical vapor deposition.

[0079] In the case of providing an additional film between the carrier disk and the metal film, the step of providing a carrier disk made of glass, in particular quartz glass, which is transparent to visible light and has a metal film on the upper side means that the metal film is arranged indirectly on the upper side. Accordingly, the application of the metal film to the upper side of the carrier disk is to be understood as an application of the metal film indirectly to the upper side of the carrier disk. The method preferably comprises the application of the additional film to the carrier disk, wherein the metal film is applied to the additional film. Accordingly, the growth of a diamond layer as a cover disk on the upper side of the carrier disk by means of chemical vapor deposition in the case of an additional film between the metal film and the carrier disk is to be understood as growing a diamond layer as a cover disk indirectly on the upper side by means of chemical vapor deposition.

[0080] The metal film can diffuse into the additional film and in particular also into the carrier disc.

[0081] The resulting watch glass advantageously comprises the carrier disc, the additional film and the diamond layer as a cover disc, wherein the additional film is arranged between the carrier disc and the cover disc and the diamond layer is firmly connected to the arrangement of the carrier disc and the additional film.

[0082] The invention preferably comprises the use of the component, produced according to one of the methods described above, as a watch glass or as a screen for a smartphone.

[0083] Furthermore, the invention shows a method for producing a diamond disc (embodiment variant 2), comprising the following steps, whereby the above considerations also apply to this method:

[0084] (i) Providing a substrate of preferably pure, crystalline silicon with a metal film on top. Preferably, the method also includes applying the metal film to the top of the substrate. Since silicon already has a face-centered cubic crystal structure, the crystallographic alignment of a metal film on the silicon wafer preferably does not follow the same process as the annealing of a metal film on quartz glass. Here, the nickel or copper is preferably deposited in the appropriate cubic structure during the application of the metal film to the silicon.

[0085] If the deposition of the additional metal layer of Ni or Cu is insufficiently crystallographically aligned, the alignment can be perfected by additional annealing.

[0086] (ii) Furthermore, the process involves growing a diamond layer as a diamond disk by means of chemical vapor deposition, also known as a CVD process or chemical vapor deposition process. In particular, a microwave plasma chemical vapor deposition (MPCVD) process or a hot filament CVD (HFCVD) process is used. This process step is carried out, in particular, in a device for carrying out chemical vapor deposition.

[0087] (iii) After growth, the substrate is removed from the diamond disk. The process for producing the diamond disk preferably involves using the disk as a substrate for a semiconductor wafer.

[0088] The process for producing the diamond disk preferably involves using a metal film made of nickel and / or copper. Preferably, the metal film consists of more than half, or in particular entirely, of at least one of these metals. An alloy of copper and nickel has proven advantageous for the metal film.

[0089] Preferably, the method for producing the diamond disk provides that the metal film before growth has a thickness of a maximum of 30 nm, preferably a maximum of 20 nm, more preferably a maximum of 10 nm, preferably a maximum of 5 nm; preferably wherein the metal film has a thickness of at least 2 nm. During the process, the metal reacts with the silicon substrate and diffuses partially or completely into the substrate, thus disappearing at least partially. This process has certain advantages in that, for example, silicon-nickel compounds are formed, which push back the polycrystalline carbon formations during the diamond growth process or can assist in the dissolution of unwanted non-diamond deposits with the aid of hydrogen gas.

[0090] Preferably, the method for producing the diamond disk provides that the diamond disk has a thickness of at least 30 pm and / or a maximum of 2 mm after growth.

[0091] Preferably, the method for producing the diamond disc provides that the metal film is applied by vapor deposition or cathode sputtering or electron beam evaporation or an electrolytic process.

[0092] Preferably, the method for producing the diamond disk includes applying diamond powder to the metal film prior to growth. In particular, this is done by applying a mixture of a liquid with diamond powder to the metal film, and removing the liquid, in particular by centrifugation and / or evaporation.

[0093] The invention preferably comprises the use of the diamond disc, produced according to one of the methods described above, as a watch glass or as a disc for a smartphone.

[0094] Furthermore, the invention relates to a method for producing a watch glass, in particular a watch glass as described above, which comprises the following steps: • Producing a, in particular monocrystalline or quasi-monocrystalline, diamond disc as a cover disc by means of hetero-epitaxy using the method described above, in particular with the steps:

[0095] ■ Providing a substrate of preferably pure, crystalline silicon,

[0096] ■ Applying a metal film on top of the silicon substrate, in particular made of copper and / or nickel, and / or with a thickness between 5 nm and 20 nm,

[0097] ■ preferably conditioning the metal film by annealing,

[0098] ■ Applying diamond powder, in particular a layer of DND (detonation nano-diamonds), to the, in particular conditioned, metal film,

[0099] ■ Growing a diamond disc by means of chemical vapor deposition, in particular by means of a microwave plasma chemical vapor deposition (MPCVD) process or a hot filament CVD (HFCVD) process, on said metal film,

[0100] ■ Removing the silicon substrate with the metal film from the diamond disk, and

[0101] • Connecting the cover plate (4) to a layer formed as a carrier plate with a lower refractive index than the cover plate and a thickness greater than the wavelengths of visible light, in particular by means of a connecting intermediate layer.

[0102] In this case, where the diamond layer is a separate disc and the substrate on which it was formed has been separated, the connecting intermediate layer is primarily a purely adhesive bond, which is positioned subsequently, rather than before, between the carrier disc (or carrier glass) and the cover disc. This is preferably a laminate layer used to laminate the carrier glass and the cover glass together.

[0103] The watch glass advantageously comprises the intermediate layer (connecting intermediate layer) between the cover plate and the carrier plate. The intermediate layer firmly connects the cover plate to the carrier plate. The intermediate layer can in particular consist of one or more sub-layers. The multiple sub-layers can be made of the same material or different materials. The production of the watch glass with the intermediate layer between the cover plate and the carrier plate, in other words the production of the watch glass as laminated composite glass, enables a particularly shatter-resistant watch glass because in the event of an impact on the watch glass, the impact energy can be absorbed by the cover plate via the intermediate layer from the carrier plate. In addition, laminating the cover plate to the carrier plate is a cost-effective process because it allows the thickness of the cost-intensive cover plate to be significantly reduced.In addition to the two advantages of shatter resistance and cost-effectiveness, laminating the cover plate to the carrier plate has another advantage. The high refractive index of the cover plate means that at the four transitions of the incoming and outgoing light at the boundary between diamond and another optical medium, a portion of the light is lost through reflection. Because the difference in refractive index between these two optical media (diamond intermediate layer) at the interface between the diamond of the cover plate and the intermediate layer is smaller than the difference in refractive index between diamond and air, the light balance of the laminated watch glass is improved. In particular, a gray haze that can occur with a non-laminated watch glass can be reduced and - depending on the color of the watch dial - is no longer as pronounced or is no longer disturbing at all.In one embodiment of the invention, with a laminated watch glass, the aforementioned at least one coating on the inside of the cover plate can be omitted. This simplifies the manufacture of the watch glass. A further advantage of the laminated watch glass is that when light passes through the watch glass, the beam offset is lower than when passing through a non-laminated watch glass due to the lower refractive index of the intermediate layer and the carrier plate compared to diamond (cover plate) with the same overall thickness.

[0104] In particular, the intermediate layer between the cover plate and the carrier plate can be thinner than the cover plate and / or the carrier plate.

[0105] However, it is also possible for the intermediate layer to be thicker than the cover plate. For example, the intermediate layer can have a thickness of 0.78 mm, while the cover plate has a thickness of 0.5 mm or 0.3 mm. For this purpose, a laminating film, in particular an EVA film, with a thickness of 0.1 mm to 0.8 mm can be used. According to another example, the intermediate layer can have a thickness of 0.58 mm. To produce the intermediate layer, for example, a first laminating film, in particular a first EVA film, with a thickness of 0.38 mm, and a second laminating film, in particular a second EVA film, with a thickness of 0.2 mm can be used. The cover plate can be 0.5 mm thick and thus thinner than the intermediate layer.

[0106] In particular, the intermediate layer between the cover pane and the carrier pane can each consist of at least one cured adhesive layer, preferably of a cured UV adhesive, or of at least one laminating layer made of / with EVA, PVB, Sentry Glass or another laminating film.

[0107] In particular, the intermediate layer between the cover plate and the carrier plate can have a refractive index equal to the refractive index of the carrier plate, up to + / - An = 0.4, preferably up to + / - An = 0.2. "An" represents the difference between the refractive index of the intermediate layer and the refractive index of the carrier plate. Preferably, the refractive index of the intermediate layer can be equal to the refractive index of the carrier plate.

[0108] In particular, the intermediate layer between the cover plate and the carrier plate can have a refractive index between 1.4 and 1.6, in particular 1.48.

[0109] In particular, the intermediate layer between the cover plate and the carrier plate can have a thickness of at least 0.05 mm, preferably at least 0.1 mm. Furthermore, the intermediate layer between the cover plate and the carrier plate, individually or in total, can have a thickness of at most 0.8 mm, preferably at most 0.4 mm.

[0110] Furthermore, the invention relates to a watch, in particular a wristwatch, comprising a case and a watch glass arranged on the case according to the previous description of the watch glass and / or manufactured according to one of the previously described methods.

[0111] Further details, advantages and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0112] Fig. 1 to 8 show a schematic view of the process according to the invention for producing a diamond disk by growth on a silicon substrate, in particular for embodiment variant 2.

[0113] First, the CVD reactor 1, which serves as a device for conducting chemical vapor deposition, is equipped with the silicon substrate 2 and the applied metal film 3; e.g., a nickel layer of either 5 nm or 10 nm thickness, onto which a layer of diamond crystals 4 with a grain size of 5 nm to 40 nm is applied. The diamond crystals are preferably DND (Detonation Nano Diamond) crystals, but can also be produced using a process other than detonation. The high surface energy of the nickel and diamonds creates a uniform and dense distribution of the diamond crystals on the nickel film. The same applies to copper. For the sake of clarity, the CVD reactor 1 is only shown in Fig. 1.

[0114] For example, a standard MPCVD reactor (microwave plasma chemical vapor deposition reactor) can be used as CVD reactor 1. An HFCVD reactor (hot filament chemical vapor deposition reactor) is also suitable. Advanced reactors that use additional means (such as laser or ion bombardment) to deliver energy to the diamond growth plane are also suitable.

[0115] Fig. 1: First, we evacuate the reactor chamber of the CVD reactor 1 to remove all atmospheric gases. Then, while slowly increasing the temperature, we flood the chamber first with hydrogen, the process gas, and then with methane, the carrier of the carbon that we want to deposit as diamond on the substrate. The ratio of hydrogen to methane is approximately 10 / 1. The flow rate of the hydrogen is approximately 400 sccm and that of the methane approximately 40 sccm, but you can also choose a different flow rate and a different ratio of H2 to CPU. We initially keep the pressure in the reactor chamber at a very low level of approximately 25 Torr. As the process progresses, we increase the pressure to up to 135 Torr.

[0116] Fig. 2: When we reach 200 °C during the temperature ramp-up, the diamond crystals do not yet grow, but the nickel slowly begins to diffuse into the silicon of the substrate 2 and starts to form an intermediate layer 5 of nickel-silicon.

[0117] During the next operating time of the first hour, polycrystalline non-diamond carbon (carbon 6) forms between the individual seed cells (diamond crystals 4) at 400°C (Fig. 3). However, this carbon is broken down by the process hydrogen and converted by the plasma into methane or other hydrogen-carbon gases. In the process (Fig. 4), carbon 6 also diffuses into the intermediate layer 5 (nickel-silicon layer) and then diffuses out again. The diamond crystals 4, which were initially arranged randomly, slowly begin to grow. They grow preferentially in the (110) orientation or in the (100) orientation. Since the (110) oriented crystals 4 grow somewhat faster than those in other directions, an almost uniform growth orientation soon forms.

[0118] Fig. 5: At a temperature of 750 °C, a polycrystalline layer 7 of non-diamond carbon (carbon 6) initially forms on the diamond crystals 4, but this layer regresses at an even higher temperature.

[0119] Fig. 6: By absorbing carbon from the methane gas, we obtain a growth structure in which the rapidly growing crystals take energy and methane gas away from the slower-growing crystals, overgrowing them. Fig. 7 and 8: With further growth, a more or less uniform layer of rapidly growing diamond crystals 4 forms, all growing upward in the same orientation.

[0120] Small silicon-nickel particles 8 or polycrystalline black carbon may be deposited in the boundary layer, but these particles are so small that they are below the limit of visibility to the naked eye. The nickel layer has now almost or completely disappeared, and all the nickel has diffused into the silicon substrate.

[0121] While after 2 to 3.5 hours we still have about 10 to 15% of the diamond in the orientation (11 1 ), after about 10 hours the ratio of diamond in the orientation (1 10) to diamond in the orientation (11 1 ) is already almost 95% to 5%.

[0122] We can now speak of a monocrystalline or “quasi-monocrystalline” diamond layer or diamond disc.

[0123] Chemically speaking, the following happens, which applies to both variant 1) and variant 2):

[0124] A hydrogen molecule from the process gas (or catalyst gas) H2 decomposes and the two hydrogen atoms attach themselves to two carbon atoms of the diamond disc or diamond seed, which in turn release their bond to each other.

[0125] Then a hydrogen atom splits off from the methane gas, forms an H2 molecule with the hydrogen atom that had temporarily bonded to a carbon atom of the diamond lattice, and thus releases the carbon atom, which can now bond with the free valence of the carbon atom of the methane.

[0126] The same process also occurs with the second carbon atom, which has a free valence once a hydrogen atom has been removed.

[0127] Finally, the H2 gas plasma tears one H atom from each of the partially bound methane gas molecules, whereupon the two free valences of the two carbon atoms of the diamond can bond with each other.

[0128] Thus, two new carbon atoms are docked to the diamond, and the diamond has grown a little bit.

[0129] Depending on the temperature and gas mixture, the growth rate is up to 8 pm / h, sometimes up to 10 pm / h.

[0130] Subsequent annealing of the diamond disc, as is common in the production of synthetic diamonds—that is, the "crystallization" of the diamond structure and color enhancement in the HPHT reactor—is not possible. The double-structured quartz-diamond glass might not survive this procedure unscathed. Therefore, the growth rate in this process is kept relatively low, resulting in a better color and purer structure of the diamond part, making subsequent crystallization in the annealing process using the HPHT process unnecessary.

[0131] After growth, the finished diamond disc is mechanically polished, preferably on the accessible surfaces, in order to have an absolutely smooth surface

[0132] If, in the process for embodiment 1), we incorporate an additional film, for example a thin layer of silicon, e.g. between 5 nm and 10 nm, between the layer of carrier disk 2 and metal film 3, then this additional film causes the polycrystalline "non-diamond carbon" (NDC) to be incorporated into the silicon (SiC), before being dissolved again in the plasma process. Therefore, the additional film can improve the optical quality of the component. Furthermore, due to its minimal thickness, the additional film represents a film that has a certain degree of elasticity and therefore reduces the mechanical stress due to the different expansion coefficients of quartz glass and diamond.

[0133] For the process for producing the diamond wafer without a carrier wafer (version 2), we prefer to use a standard semiconductor wafer made of pure silicon. Silicon already has a perfect crystallographic structure, similar to that of diamond—a face-centered cubic crystal structure. Furthermore, the semiconductor wafer made of pure silicon has a coefficient of thermal expansion of only 2.5 x 10 -6 K -1 . This is still two and a half times the expansion coefficient of synthetic diamond (1 .0 x 10 -6 K -1 ). However, apart from special glasses such as pure quartz glass, this is a coefficient of expansion that is very close to that of diamond. For comparison: sapphire has 6.0 x 10 6 K- 1 , Float glass has 9.2 x 10 6 K 1 .

[0134] We apply a metal film, such as nickel, to the wafer. The layer thickness should be approximately 5 nm or 10 nm. Not only does nickel have the same crystallographic structure as diamond (a face-centered cube), but the size of the nickel unit cell corresponds to the size of the diamond unit cell, with only a 1.5% deviation (nickel 3.52 Å, diamond 3.57 Å). We then coat the silicon / metal film substrate with DND diamond powder. We then grow synthetic diamond onto the substrate using a CVD process, preferably in the crystallographic orientation (1 10) or (100). The growth rate is approximately 8 pm / h. Therefore, if we want to produce a diamond glass approximately 1 mm thick, we need approximately 150 hours. We remove the substrate coated with the diamond film from the reactor after 6 days. We first use a laser to remove the polycrystalline carbon from the edges of the diamond glass.We then laser cut the glass to the exact desired size and shape.

[0135] We then sand it on both sides until it reaches exactly the desired thickness.

[0136] Afterwards, a coating or multiple coatings are preferably applied to the inside.

[0137] The aspect of installing an additional film between the carrier disk 6 and the metal film 3 in the method for embodiment 1), as described above, is explained in more detail with reference to Figures 9 to 12.

[0138] In particular, with reference to Figures 9 to 12, a method for producing a glass 1 is described, which comprises the steps of providing a carrier disk 6 made of glass, in particular quartz glass, which is transparent to visible light and has a metal film 3 on the upper side, and growing a diamond layer 9, in particular a monocrystalline or quasi-monocrystalline layer, as a cover disk on the upper side of the carrier disk 6 by means of heteroepitaxy by chemical vapor deposition, in particular by means of a microwave plasma chemical vapor deposition (MPCVD) method or a hot filament CVD (HFCVD) method.

[0139] It is provided that, prior to growth, an additional film 1009 made of mineral material is located between the metal film 3 and the carrier disk 6. The additional film 1009, which is made of glass, has a thickness of a maximum of 1 mm, preferably a maximum of 0.5 mm, more preferably a maximum of 0.4 mm, more preferably a maximum of 0.3 mm. Furthermore, the additional film 1009 has an expansion coefficient between 1.8 x 10 -6 K -1 and 2.2 x 10 -6 K' 1 , especially 2 x 10 -6 K 1 , and a softening temperature between 500 °C and 650 °C, in particular 550 °C. This means that the additional film 1009 has a low melting point and can bridge the expansion coefficient between the quartz glass carrier disk 6 and the cover disk 9 (diamond layer). The additional film 1009 can also be referred to as overlay or bridge glass.

[0140] Fig. 9 shows the carrier disk 6, which is formed of quartz glass, with the additional film 1009 and the metal film 3. The additional film 1009 is applied, in particular melted, to the carrier disk 6.

[0141] The metal film 3, in particular made of nickel and / or copper, is applied to the additional film 1009. For this purpose, the metal film 3 can be vapor-deposited onto the additional film 1009. Other processes such as cathode sputtering, electron beam evaporation, or an electrolytic method for applying the metal film 3 to the additional film 1009 can also be used. The metal film 3 preferably has a defined crystallographic orientation. For this purpose, the metal film 3 can be conditioned by annealing during or after application. Annealing causes the initially amorphous metal film 3 to crystallize.

[0142] Diamond powder 4, in particular a layer of DND (detonation nano-diamonds), in particular with a grain size of 5 nm to 40 nm, is applied to the metal film 3. This is achieved, in particular, by the following steps: applying a mixture of a liquid (carrier liquid) with the diamond powder 4 to the metal film 3 and removing the liquid, in particular by centrifugation and / or evaporation. During growth, the diamond grains of the diamond powder 4 align themselves via surface tension according to the crystal lattice of the oriented metal film 3.

[0143] To achieve the arrangement shown in Figure 9, the following steps can be carried out:

[0144] • Providing the carrier disc 6 (the quartz glass)

[0145] • Applying, in particular melting, the additional film 1009 on the carrier disc 6

[0146] • Applying, in particular by vapor deposition, the metal film 3 onto the additional film 1009

[0147] • preferably conditioning the metal film 3 by annealing,

[0148] • Applying diamond powder 4, in particular a layer of DND (detonation nano-diamonds), to the, in particular conditioned, metal film 3,

[0149] Figure 10 shows the state in which the growth or CVD process has started and a diamond film 1010 has been deposited on the metal film 3.

[0150] According to Figure 11, the metal film 3 simultaneously diffuses into the additional film 1009 and further into the carrier disk 6, whereby the diamond film 1010 continues to grow.

[0151] Figure 12 shows the finished watch glass 1. The watch glass 1 comprises the carrier disc 6, the additional film 1009, and the diamond layer 9 as a cover disc. The additional film 1009 is arranged between the carrier disc 6 and the diamond layer 9, and the diamond layer 9 is firmly bonded to the arrangement of the carrier disc 6 and the additional film 1009. The diamond layer 9 integrates the grains of the diamond powder 4, in particular the detonation nano-diamonds, so that a uniform disc is created. As can be seen from Figure 12, the metal film 3 has disappeared. The watch glass 1 corresponds to the transparent, scratch-resistant component.

[0152] List of reference symbols

[0153] 1 CVD reactor

[0154] 2 Silicon substrate (substrate) 3 Metal film

[0155] 4 diamond crystals / diamond powder

[0156] 6 carrier disc

[0157] 5 Nickel-silicon interlayer

[0158] 6 Carbon

[0159] 7 polycrystalline layer

[0160] 8 silicon-nickel particles

[0161] 9 diamond layer

[0162] 1009 Additional film

[0163] 1010 Diamond Film

Claims

Claims 1 . A method for producing a transparent, scratch-resistant component, comprising the following steps: • Providing a carrier plate (6) made of glass, in particular quartz glass, which is transparent to visible light and has a metal film (3) on the upper side, • Growing a, in particular monocrystalline or quasi-monocrystalline, diamond layer (9) on the upper side of the carrier disk (6) by means of hetero-epitaxy by chemical vapor deposition, in particular by means of a microwave plasma chemical vapor deposition (MPCVD) process or a hot filament CVD (HFCVD) process.

2. The method according to claim 1, wherein the metal film (3) comprises nickel and / or copper; preferably consists of one of these metals, or of an alloy of these two metals.

3. Method according to one of the preceding claims, wherein the metal film (3) has a thickness of at most 30 nm, preferably at most 20 nm, more preferably at most 10 nm, more preferably at most 5 nm, before growth; preferably wherein the metal film (3) has a thickness of at least 2 nm.

4. Method according to one of the preceding claims, wherein the diamond layer (9) after growth has a thickness of at least 10 pm and / or a maximum of 0.5 mm.

5. Method according to one of the preceding claims, wherein the carrier disc (6) has an expansion coefficient of 0.45 x 10 -6 K -1 up to 1.2 x 10 -6 K -1 , preferably 0.8 x 10 -6 K -1 up to 1.2 x 10 -6 K' 1 , has.

6. Method according to one of the preceding claims, wherein the metal film (3) is applied by vapor deposition or cathode sputtering or electron beam evaporation or an electrolytic process.

7. Method according to one of the preceding claims, wherein the metal film (3) is brought into a non-amorphous crystalline structure by annealing.

8. Method according to one of the preceding claims, wherein a diamond powder (4) is applied to the metal film (3) before growth.

9. The method according to claim 8, comprising the following steps: applying a mixture of a liquid and diamond powder (4) to the metal film (3) and removing the liquid, in particular by centrifugation and / or evaporation.

10. Method according to one of the preceding claims, wherein the metal film (3) is at least partially, in particular completely, diffused into the carrier disc (6) by thermal action during the chemical vapor deposition.

11. Method according to one of the preceding claims, wherein, before growth, an additional film (1009) of mineral material, preferably with silicon, or synthetic material is located between the metal film (3) and the carrier disc (6).

12. The method according to claim 11, wherein the additional film (1009) has a thickness of at most 0.5 mm, preferably at most 0.4 mm, more preferably at most 0.3 mm.

13. The method according to claim 11 or 12, wherein the additional film (1009) • an expansion coefficient between 1.8 x 10 -6 K -1 and 2.2 x 10 -6 K 1 , especially of 2 x 10 -6 K -1or has a temperature-dependent, variable expansion coefficient which is 3.9 x 10 -6 K -1 up to 4.1 x 10 -6 K -1 , especially 4 x 10 -6 K 1 , and from 0°C to 100 °C, especially at 25 °C, 0.9 x 10 -6 K -1 up to 1.1 x 10 -6 K 1 , especially 1 x IO 6 K' 1 , and / or • has a softening temperature between 500 °C and 650 °C, in particular 550 °C, and / or • has a chemical composition which has an expansion coefficient of 3.9 x 10 -6 K -1 up to 4.1 x 10 -6 K' 1 , especially 4 x 10 -6 K -1, and when cooling from the operating temperature of the CVD process, undergoes a crystallization process, which causes the expansion coefficient to be 0.9 x 10 -6 K -1 up to 1.1 x 10 -6 K 1 , especially 1 x 10 -6 K 1 , and / or • Contains alkalis and / or metals.

14. Method according to one of the preceding claims, wherein the carrier disc (6) is formed from a glass which: • has a softening temperature between 500 °C and 650 °C, in particular 550 °C, and / or • has a temperature-dependent, variable expansion coefficient, which is 3.9 x 10 -6 K -1 up to 4.1 x 10 -6 K -1 , especially 4 x 10 -6 K -1, and from 0 °C to 100 °C, especially at 25 °C, 0.9 x 10 -6 K -1 up to 1.1 x 10 -6 K -1 , especially 1 x 10 -6 K -1 , and / or • has a chemical composition which has an expansion coefficient of 3.9 x 10 -6 K -1 up to 4.1 x 10 -6 K' 1 , especially 4 x 10 -6 K -1 , and when cooling from the operating temperature of the CVD process, undergoes a crystallization process, which causes the expansion coefficient to be 0.9 x 10 -6 K -1 up to 1.1 x 10 -6 K' 1 , especially 1 x 10 -6 K -1 , and / or • Contains alkalis and / or metals.

15. A method for producing a diamond disc, in particular a monocrystalline or quasi-monocrystalline one, by means of heteroepitaxy, comprising the following steps: • Providing a substrate (2) made of preferably pure, crystalline silicon, • Applying a metal film (3) on top of the silicon substrate (2), • preferably conditioning the metal film (3) by annealing, • Applying diamond powder (4), in particular a layer of DND (detonation nano-diamonds), to the, in particular conditioned, metal film (3), • Growing a diamond disc by means of chemical vapor deposition, in particular by means of a microwave plasma chemical vapor deposition (MPCVD) process or a hot filament CVD (HFCVD) process, on said metal film (3), • Removing the silicon substrate (2) with the metal film (3) from the diamond disc.

16. The method according to claim 15, wherein a semiconductor wafer is used as the substrate (2).

17. The method according to any one of claims 15 to 16, wherein the metal film (3) comprises nickel and / or copper; preferably consists of one of these metals, or of an alloy of these two metals.

18. The method according to any one of claims 15 to 17, wherein the metal film (3) has a thickness of at most 30 nm, preferably at most 20 nm, more preferably at most 10 nm, more preferably at most 5 nm, prior to growth; preferably wherein the metal film (3) has a thickness of at least 2 nm.

19. The method according to any one of claims 15 to 18, wherein the diamond disc after growth has a thickness of at least 10 pm and / or a maximum of 0.5 mm.

20. The method according to any one of claims 15 to 19, wherein the metal film (3) is applied by vapor deposition or cathode sputtering or electron beam evaporation or an electrolytic process.

21. Method according to one of claims 15 to 20, comprising the following steps: applying a mixture of a liquid and diamond powder (4) to the metal film (3) and removing the liquid, in particular by centrifugation and / or evaporation.

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