WO2003091469A2

WO2003091469A2 - Method for joining a diamond layer to a substrate, and diamond-coated substrate

Info

Publication number: WO2003091469A2
Application number: PCT/EP2003/004211
Authority: WO
Inventors: Stefan Rosiwal
Original assignee: Friedrich-Alexander- Universität Erlangen-Nürnberg
Priority date: 2002-04-24
Filing date: 2003-04-23
Publication date: 2003-11-06
Also published as: AU2003226824A8; WO2003091469A3; AU2003226824A1

Abstract

The invention relates to a method for producing a substrate (1) coated with a diamond layer (2). According to the inventive method, a substrate (1) is prepared, said substrate having a layer (3) which extends from the surface (O) of the substrate towards the inside, comprises recesses (4) extending from the surface (O) towards the inside, and is elastically and/or plastically deformable in an xy-plane which is parallel to the surface (O), and a diamond layer (2) engaging in the recesses is then produced by means of a CVD method. Cooling stresses occurring in the diamond layer (2) during cooling are essentially compensated by an elastic and/or plastic deformation of the layer (3) in the xy-plane.

Description

Method for connecting a diamond layer to a substrate and diamond-coated substrate

The invention relates to a method for producing a substrate coated with a diamond layer and a diamond coated substrate. It relates in particular to the area of improving the adhesion of diamond layers to substrates.

Diamond-coated substrates are used in the area of wear and overheating protection of surfaces subject to wear or heat. You will e.g. B. used as heat sinks, which quickly dissipate heat from a heat source. Furthermore, such substrates are used in the form of slide rings, which run against a counter body with particularly low friction and wear.

The deposition of a diamond layer on a substrate made, for example, of metal, glass, ceramic or graphite is usually carried out according to the prior art by means of CVD processes. The problem arises that when the coated substrate cools, stresses arise in the diamond layer. These so-called "cooling tensions" in the diamond layer contribute to reduced adhesion to the substrate.

From US Pat. No. 6,189,766 B1 it is known to bond a diamond layer to a substrate at a predetermined temperature by means of isostatic pressing in order to reduce cooling stresses. WO 01/26153 AI discloses a method in which a diamond layer is connected to a copper substrate by means of a solder. The procedures are complex and expensive.

iSTÄTIGUNGSKOPIE Fan et al. , Diamond and Related Materials 6 (1997), 422-425 describes a method in which a copper layer is provided with a diamond layer at low substrate temperatures. Due to the low substrate temperatures, lower cooling stresses occur in the diamond layer. However, the diamond quality and the diamond growth rate are reduced by lowering the substrate temperature. The proposed method is particularly unsuitable for the production of heat sinks. This requires a diamond layer with high diamond quality.

Vedawyas, M. et al. , Materials Science and Engineering B78

(2000) 16-21 describes the production of a heat sink using a copper substrate, to which a diamond layer is applied with the interposition of a titanium nitride (TiN) layer. The provision of the interposed TiN layer improves the adhesion of the diamond layer. However, the cooling tensions in the diamond layer are not significantly reduced.

A method for producing substrate-free diamond fibers is known from US Pat. No. 6,051,152. It is based on a z. B. fiber made of copper deposited by means of a CVD process a diamond layer. The copper fiber is then removed by etching.

A composite material is known from US Pat. No. 6,110,594, which is made from diamond-coated fibers. The randomly existing fibers consisting of SiN, SiC or Al ₂ 0 ₃ are connected to one another by means of polycrystalline diamond.

A diamond-coated substrate is known from EP 0 780 489 A1, in which the substrate is pretensioned before the coating in order to reduce the cooling voltages. The object of the invention is to eliminate the disadvantages of the prior art. In particular, a method is to be specified with which a reduction in cooling stresses in a diamond layer applied to a substrate can be achieved in the simplest and cheapest possible way. In particular, the method should also make it possible to bind a diamond layer to metals, for example copper, which do not form stable carbides. Finally, a substrate with a diamond coating should be specified, the durability of which is improved.

This object is solved by the features of claims 1 and 22. Expedient configurations result from the features of claims 2 to 21 and 23 to 40.

According to the invention, a method for producing a substrate coated with a diamond layer is provided with the following steps:

a) providing a substrate with a layer extending from the surface thereof to the interior, which has recesses extending from the surface to the interior and is elastically and / or plastically deformable in an xy plane parallel to the surface, and

b) Production of a polycrystalline diamond layer engaging in the recesses by means of a CVD process, cooling voltages occurring in the diamond layer during cooling by means of an elastic and / or plastic

Deformation of the layer in the xy plane can be essentially compensated.

With the proposed method, polycrystalline diamond layers of any thickness can be applied to any substrates. to be brought. The provision of the layer according to the invention prevents chipping of the diamond layer caused by cooling stresses or undesired bending of the substrate. The proposed method makes it possible, in particular, to deposit diamond layers on metals with high thermal expansion coefficients, for example copper.

When cooling, the layer is advantageously deformed such that in the Raman spectrum the diamond peak is at a wave number of less than 1342, preferably less than 1337. The diamond peak is particularly preferably only slightly shifted to higher values compared to the peak of natural diamond of 1332 l / cm. For the connection of the peak shift of the diamond peak in the Raman spectrum, reference is made, for example, to Fan Q.H. et al. , Journal of Material Science 34 (1999), 1353-1365.

According to one embodiment, the surface is flat. A depth of the recesses is expediently twice as large as their diameter. The depth of the recesses can be at least 1 μm, preferably more than 50 μm. The diameter of the recesses is advantageously so large that diamond growth is possible therein. It is expediently 0.5 to 100 μm. According to a further embodiment, the recesses extend essentially perpendicularly from the surface. With the aforementioned features, it is possible to produce a flat diamond layer on a substrate. The diamond layer engages in the recesses. The diamond layer is held in a form-fitting manner in the recesses.

According to one embodiment, the shape of the recesses is changed lung voltages in compensating for cool down ^¬. This applies in particular to recesses that are not or are only partially filled with diamond. In particular, the diamond layer is mechanically anchored in the recesses due to the change in shape of the layer caused by the cooling. The recesses can be made mechanically, by means of LASER or by etching.

According to a particularly advantageous embodiment, the layer is formed from compressed fibers lying against one another and oriented essentially perpendicular to the surface. The fibers can be made of metal, glass, graphite or ceramic. In this case, the elongate recesses, which run essentially perpendicular to the surface, can be produced by etching fiber interspaces. It is also possible for the substrate as a whole to be produced by compacting fibers. With the aforementioned features, it is possible in a particularly simple and cost-effective manner to produce a substrate with a layer which ensures compensation of the cooling voltages in the xy direction.

Furthermore, it is also possible for the layer to be produced from a metal foam or a sintered body. Such bodies can also have suitable recesses which, on the one hand, enable the diamond layer to engage and, on the other hand, ensure compensation of the cooling voltages.

According to a further embodiment, the density of the substrate is measured before, during or after the production of the diamond layer in the area from the bottom to the inside of the

Substrate extending further layer increased. The density can be increased by means of forming, infiltration or sintering. According to an advantageous embodiment, the layer is produced from a metal or an alloy that does not form stable carbides. The metal can be formed from copper, gold, platinum or silver or the alloy can contain copper, gold, platinum or silver. According to the prior art, such metals or alloys are not suitable for applying a diamond layer because they cannot form a chemical bond with the diamond due to the lack of carbide formation.

According to a further embodiment, the layer and the substrate are formed in one piece. However, it may also be the case that the layer is connected to the substrate. Such a connection can be made, for example, by means of a solder.

According to a further provision of the invention, a diamond-coated substrate is provided, a polycrystalline diamond layer being provided on a surface of the substrate and the substrate having a layer which extends from the surface to the inside and has recesses which extend from the surface to the inside, into which the diamond layer engages.

Because of the advantageous configurations of the diamond layer, reference is made to the features explained in the method, which also apply analogously to the diamond-coated substrate.

An exemplary embodiment of the invention is explained in more detail below with reference to the drawings. Show it:

Fig. 1 is a schematic representation of a substrate _. tensile and compressive stresses occurring, 2 shows a schematic illustration of a diamond-coated substrate,

3 shows a scanning electron microscope (SEM) image of a surface formed from copper fibers,

4 shows an SEM photograph of a 2 μm thick CVD diamond layer on the surface according to FIG. 3,

5 an SEM image of a 20 μm thick CVD diamond layer on the surface according to FIG. 3,

6 shows an SEM image of a 50 μm thick CVD diamond layer on the surface according to FIG. 3,

7 CVD diamond deposited in fiber interstices,

8 is a cross-sectional view of FIG. 7,

9 is a schematic top view of a possible fiber arrangement,

10 is a perspective view of FIG. 9,

11 shows the fiber arrangement according to FIG. 10 with diamond nuclei,

Fig. 12 is a schematic view of a fiber arrangement with CVD diamond in fiber gaps and

13 shows a Raman spectrum on a layer of a

CVD diamond layer deposited on the substrate.

1 schematically shows the distribution of compressive and tensile stresses in the case of a substrate 1 which has been coated with a diamond layer 2 by means of a CVD process. Substrates 1 made in particular from metals have a significantly higher coefficient of thermal expansion than diamond. As a result, when cooling from a coating temperature, e.g. B. from 600 to 1000 ° C, for a stronger contraction of the substrate 1 than the diamond layer 2. In the diamond layer 2 compressive stresses and tensile stresses build up in the substrate 1, in particular in the vicinity of a surface 0. Such cooling voltages can cause the diamond layer 2 to flake off.

2 schematically shows a substrate 1 according to the invention provided with a diamond layer 2. The substrate 1 is formed from a layer 3 which extends from the surface 0 to the interior and has recesses 4 which extend from the surface 0 to the interior. The surface 0 extends in an xy direction. The direction of growth of the diamond layer 2 is the z direction.

Layer 3 and a further layer 5 underneath it are produced here from compressed copper fibers 6. The fibers 6 can also be made of other metals, glass or ceramics. The diamond layer 2 has grown into the recesses 4 in the layer 3. Layer 3 thus forms a diamond fiber penetration structure. The diamond layer 2 can have a thickness of 5 to 50 μm and the layer 3 a thickness of 10 to 200 μm. The thickness of the further layer 5 is arbitrary. The recesses 4 provided therein can be infiltrated with a metal.

FIG. 3 shows an SEM image of a surface O. The surface O is produced by compressed copper fibers 6. The recesses 4 have been exposed by etching. They extend essentially perpendicularly from the surface 0. The copper fibers 6 here have a diameter of approximately 50 μm. FIG. 4 shows an SEM image of a surface O according to FIG. 3, which has been coated with a 2 μm thick diamond layer 2 by means of a CVD method. The recesses 4 are z. T. not yet filled with diamond.

5 and 6, the further formation of the diamond layer 2 is shown on the basis of SEM images. In FIG. 5, the thickness of the diamond layer 2 deposited by means of the CVD method is 20 μm, in FIG. 6 50 μm. 6, the diamond surface is already flat and homogeneous. The surface O formed from the ends of the copper fibers 6 is completely overgrown.

7 shows an SEM image of the surface 0 after the removal of the diamond layer 2. The ends of the copper fibers 6 and the recesses 4 filled with diamond can be seen.

FIG. 8 shows a cross-sectional view according to FIG. 7. From this it can be seen that the recesses 4 are filled with diamond to a depth of at least 100 μm. The result is an excellent mechanical anchoring of the diamond layer 2.

FIGS. 9 to 12 again schematically show the formation of layer 3. FIGS. 9 and 10 show a top view and a perspective view of a possible arrangement of the copper fibers 6. FIG. 11 shows schematically the beginning of the filling of the recesses 4 with diamond. 12, the recesses 4 are completely filled with diamond. The diamond layer 2 is anchored in the recesses 4.

The _production, of the substrate 1 according to the invention can be carried out at ^¬ play, as follows: First, a bundle consisting of parallel copper fibers 6 with a diameter of approximately 50 μm is produced. The copper fibers 6 are compacted in a copper jacket by round hammering. Subsequently, the fiber intermediate spaces or recesses 4 are exposed or enlarged by etching. ^'

The surface is germinated in the ultrasonic bath with diamond nuclei in such a way that 4 diamond nuclei with a diameter of 4 nm, for example, are deposited in the recesses.

After diamond seeding (see FIG. 11), the substrate 1 is used in a conventional microwave CVD diamond coating system. An approximately 50 μm thick diamond layer 2 is then deposited on the substrate 1 in the CVD process. The coating time is 5.5 hours at a pressure of 60 torr and an output of 2500 W. The atmosphere contains 4% menthan and 96% hydrogen.

During the CVD process, the diamond initially grows in the recesses 4 and on the surface 0 formed by the fiber ends 6. Finally, a diamond-fiber penetration structure which almost completely fulfills the recesses 4 is formed. A flat diamond layer 2 then grows on the surface O. The diamond layer 2 is mechanically anchored in the recesses 4. After the deposition of the diamond layer 2, the coating temperature is cooled to room temperature. The compressive stresses that occur in particular in the diamond layer 2 are now compensated for by an elastic and / or plastic deformation of the copper fibers 6. The copper fibers 6 can be bent and / or stretched. Furthermore, not present or not fully ^¬ ever-filled with diamond recesses 4 be changed in shape. Such recesses 4 can be almost completely be closed constantly. 3, the described compensation of the compressive stresses is shown schematically in that the fibers 6 in the edge region of the substrate 1 show an inward-pointing bend.

13 shows Raman spectra which have been recorded at three different locations of the diamond layer 2. The diamond peak is at a wave number of 1336 1 / cm. It is only slightly shifted from the wave number of natural diamond from 1332. This shows that the compressive stresses in the diamond layer 2 have essentially been compensated for by a deformation of the layer 3 in the xy direction. Bending of the substrate 1 and / or the layer 3 in the z direction does not occur.

With the present invention it is possible for the first time to deposit diamond layers 2 on substrates 1 which do not form stable carbides. Diamond heat spreading layers in particular can be produced on copper substrates as heat sinks.

This makes it possible to combine the advantages of a diamond layer 2, namely its hardness and thermal conductivity, with the. Advantages of inexpensive metals which also have a high thermal conductivity, such as copper.

Reference character list

1 substrate

2 diamond layer

3 layer

4 recess

5 more layers

6 copper fiber

0 0 surface

Claims

claims

1. A method for producing a substrate (1) coated with a diamond layer (2), comprising the following steps:

Providing a substrate (1) with a layer (3) extending from its surface (0) towards the inside, which has recesses (4) extending from the surface (0) towards the inside and in one towards the surface (O ) parallel xy plane is elastically and / or plastically deformable and

Manufacture of a polycrystalline diamond layer (2) engaging in the recesses (4) by means of a CVD process, cooling voltages occurring during cooling in the diamond layer (2) being caused by an elastic and / or plastic deformation of the layer (3) in the xy plane in the Be compensated for essentially.

2. The method according to claim 1, wherein the layer (3) is deformed on cooling such that the diamond peak in the Raman spectrum is at a wave number of less than 1342, preferably less than 1337.

3. The method according to any one of the preceding claims, wherein the surface (0) is flat.

4. The method according to any one of the preceding claims, wherein a depth of the recesses (4) is at least twice as large as their diameter.

5. The method according to any one of the preceding claims, wherein the depth of the recesses (4) is at least 1 micron, preferably more than 50 microns.

6. The method according to any one of the preceding claims, wherein the diameter of the recesses (4) is so large that diamond growth is possible therein.

7. The method according to any one of the preceding claims, wherein the recesses (4) extend substantially perpendicularly from the surface (0).

8. The method according to any one of the preceding claims, wherein in the compensation of cooling voltages the shape of the

Recesses (4) is changed.

9. The method according to any one of the preceding claims, wherein the diamond layer (2) is mechanically anchored in the recesses (4).

10. The method according to any one of the preceding claims, wherein the recesses (4) are produced mechanically, by means of LASER or by etching.

11. The method according to any one of the preceding claims, wherein the layer (3) from substantially perpendicular to the surface

(0) aligned, adjacent, compressed fibers (6) is formed.

12. The method according to any one of the preceding claims, wherein the fibers (6) are made of metal, glass, graphite or ceramic.

13. The method according to any one of the preceding claims, wherein the substrate (1) is produced by compressing the fibers (6).

14. The method according to any one of the preceding claims, wherein substantially perpendicular to the surface (0) extending out recesses (4) are produced by etching fiber interstices.

15. The method according to any one of the preceding claims, wherein the layer (3) is produced from a metal foam or a sintered body.

16. The method according to any one of the preceding claims, wherein the density of the substrate (1) before, during or after the production of the diamond layer (2) in the region of a further layer (from an underside to the inside of the substrate (1)) 5) is increased.

17. The method according to any one of the preceding claims, wherein the increase in density by means of forming, infiltration or

Sintering takes place.

18. The method according to any one of the preceding claims, wherein the layer (3) is produced from a metal or an alloy which / which does not form stable carbides.

19. The method according to any one of the preceding claims, wherein the metal is formed from copper, gold, platinum or silver or the alloy contains copper, gold, platinum or silver.

20. The method according to any one of the preceding claims, wherein the layer (3) and the substrate (1) are integrally formed.

21. The method according to any one of the preceding claims, wherein the layer (3) is connected to the substrate (1).

22. Diamond-coated substrate, a polycrystalline diamond layer (2) being provided on a surface (O) of a substrate (1), the substrate (1) being one of the surface (O) extending towards the inside

(3) with recesses (4) extending from the surface (0) towards the inside, into which the diamond layer (2) engages.

23. Diamond-coated substrate according to claim 22, wherein the surface (O) is flat.

24. Diamond-coated substrate according to one of claims 22 or 23, wherein a depth of the recesses (4) is at least twice as large as their diameter.

25. Diamond-coated substrate according to one of claims 22 to 24, wherein the depth of the recesses (4) is at least 1 μm, preferably more than 50 μm.

26. Diamond-coated substrate according to one of claims 22 to 25, wherein the diameter is so large that diamond growth is possible in the recesses (4).

27. Diamond-coated substrate according to one of claims 22 to 26, wherein the recesses (4) extend substantially perpendicularly from the surface (O).

28. Diamond coated substrate according to one of the claims

22 to 27, the recesses (4) being deformed as a result of the compensation of cooling voltages.

29. Diamond-coated substrate according to one of claims 22 to 28, wherein the diamond layer (2) in the recesses

(4) is mechanically anchored.

30. Diamond-coated substrate according to one of claims 22 to 29, wherein the recesses (4) are made mechanically, by means of LA-SER or by etching.

31. Diamond-coated substrate according to one of claims 22 to 30, wherein the layer (3) is formed from compressed fibers (6) lying against one another and oriented essentially perpendicular to the surface (0).

32. Diamond-coated substrate according to one of claims 22 to 31, wherein the fibers (6) are made of metal, glass, graphite or ceramic.

33. Diamond-coated substrate according to one of claims 22 to 32, wherein the substrate (1) is formed from compressed fibers (6).

34. Diamond coated substrate according to one of the claims

22 to 33, wherein recesses (4) running essentially perpendicular to the surface (0) are produced by etching fiber interstices.

35. Diamond-coated substrate according to one of claims 22 to 34, wherein the layer (3) is formed from a metal foam or a sintered body.

36. Diamond-coated substrate according to one of claims 22 to 35, wherein a further layer (5), which extends from a lower side toward the inside of the substrate (1), is compressed by means of shaping, infiltration or sintering.

37. Diamond-coated substrate according to one of claims 22 to 36, wherein the layer (3) made of a metal or

Alloy is produced that does not form stable carbides.

38. Diamond-coated substrate according to one of claims 22 to 37, wherein the metal made of copper, gold, platinum or Silver is formed or the alloy contains copper, gold, platinum or silver.

39. Diamond-coated substrate according to one of claims 22 to 38, wherein the layer (3) and the substrate (1) are integrally formed.

40. Diamond-coated substrate according to one of claims 22 to 39, wherein the layer (3) with the substrate (1) is connected.