GB2491685A

GB2491685A - Composite diamond bodies

Info

Publication number: GB2491685A
Application number: GB1207787.1A
Authority: GB
Inventors: Berdinus Christianus Maria Vrolijk; Gerrit Jan Pels
Original assignee: Element Six NV
Current assignee: Element Six NV
Priority date: 2011-05-10
Filing date: 2012-05-03
Publication date: 2012-12-12
Anticipated expiration: 2032-05-03
Also published as: GB201107736D0; GB201207787D0; GB2491685B; WO2012152661A1

Abstract

A composite diamond assembly comprising: a polycrystalline diamond wafer 4 and a crystalline diamond plate 2 mounted within a circular opening of the diamond wafer. The diamond wafer is bonded to the diamond plate by a brazed joint between the opposed diamond faces. The joint may comprise complementary tapered/wedge shaped side wall surfaces or a stepped side wall surfaces (see figure 2). The brazing joint may comprise Au/Sn, Cu/Ag, Cu/Ag/Ti, Au/Ge, Au/Si or Au/Ta. The composite diamond assembly body may be used as a large area diamond window or for a thermal substrate. Optical outcoupling structures such as microlenses, a diffraction grating, a Fresnel lens, a convex surface, a solid immersion lens and antireflective coating may be provided.

Description

COMPOSITE DIAMOND ASSEMBLIES

Field of Invention

The present invention relates to composite diamond assemblies in which different types of diamond material are bonded together. The composite diamond assemblies have uses such as in optical applications and as thermal substrates.

Background of Invention

Composite diamond assemblies in which different types of diamond material are bonded together are known in the art. Such assemblies are particularly useful when a high quality diamond material and/or single crystal diamond material is desirable for a particular application and where large areas of diamond material are also desirable. In such cases, ft may be difficult or impossible to form the high quality diamond material and/or single crystal diamond material to the surface areas which are desired.

Accordingly, ft has been proposed that a wafer of lower qualfty and/or polycrystalline diamond material may be formed to the desired surface area and that higher qualfty and/or single crystal diamond material can be mounted to the wafer such that a composfte diamond assembly is provided which comprises one or more high qualfty and/or single crystal diamond components mounted to a diamond wafer. Some prior art arrangements are described below.

EPO5 89464 discloses a method comprising: providing a pluralfty of closely spaced or touching single crystal diamond plates disposed on a silicon substrate; growth of a continuous layer of low qualfty single crystal diamond material over the pluralfty of single crystal diamond plates to adhere the single crystal diamond plates together; removal of the silicon substrate; processing of the single crystal diamond plates to obtain a highly flat surface; and growth of a continuous layer of higher qualfty single crystal diamond material over the processed surface of the plurality of single crystal plates. All layers are bonded together via diamond-diamond bonding One potential problem with this approach is that it is very difficult to grow a wafer of high quality single crystal diamond material over a pluralfty of single crystal diamond plates in a consistent and reproducible manner required for commercial production. A large number of crystal dislocation defects tend to extend from the plate boundaries through the overlying single crystal material. Such dislocation defects cause strain and birefringence within the single crystal material thus reducing optical performance.

Furthermore, such strain can lead to cracking of the single crystal layer. Further still, the dislocations reduce thermal conductivity and can also provide electrical conduction paths thus reducing electrical breakdown voltage.

In light of the above, it is considered by the present inventors that it would be advantageous to provide single crystal diamond material which is not so strained and which does not inevitably include a large number of dislocation defects to maintain very good thermal, optical, and/or electronic properties. However, it is very difficult to manufacture such material over large areas.

JP 08-208387 discloses a method comprising: providing a single crystal diamond substrate on a silicon support substrate; growing diamond over the composite substrate to grow single crystal diamond over the single crystal diamond substrate and polyciystalline diamond over the silicon support substrate; and removal of the silicon below the diamond substrate to form a diamond window. The single crystal diamond window is disposed within a polycrystalline layer and bonded thereto by diamond-to-diamond bonding around an edge of the single crystal diamond window. It is also described that more than one single crystal diamond window can be provided within the polycrystalline diamond layer.

One potential problem with this approach is that the bonding between the single crystal diamond plates and the polycrystalline CVD diamond support layer can be poor, both in terms of mechanical strength and in terms of thermal conductivity.

Furthermore, it can be difficuh to grow high quality single crystal CVD diamond material and high qualfty polycrystalline CVD diamond material using the same growth chemistry.

US 6562127 discloses bonding of single crystal plates to a polycrystalline carrier substrate to form composite substrates for growth of semiconductor components.

Various possible materials and methods of bonding are suggested. The described arrangement are suitable for use as a thermally conductive substrate. However, they do not appear to be suitable for optical applications as the single crystal plates are not mounted within the polycrystalline layer to provide an optical path through the polycrystalline layer.

US20050 160968 discloses a composite structure comprising a layer of single crystal diamond plates mounted to a polycrystalline diamond layer. The mounting is achieved by CVD deposition of the polycrystalline layer onto a plurality of single crystal diamond plates. This arrangement is suitable for use as a thermally conductive substrate. However, it is not suitable for optical applications as the single crystals are not mounted within the polycrystalline layer to provide an optical path through the polycrystalline layer.

US 4260397 discloses the mounting of single crystal diamonds within a polycrystalline diamond matrix. Various possible applications for such a composite structure are suggested. One example is a wire drawing die. The die comprises a single crystal diamond embedded in polycrystalline diamond matrix which is sintered within and bonded to cobalt cemented tungsten carbide annulus. A double tapered wire drawing hole is made through the centre of the die using a laser. US 4260397 also suggest that a composite structure as described therein may be used as an optical window. It is stated that if large single crystals are ground, an optical path can be provided through them. Laser windows are mentioned as a possible application. It is further stated that if an optical path is unnecessary, the single crystal diamond need not extend completely through the composite and may be surrounded by polycrystalline matrix.

In light of the above, it would appear that the general idea of mounting a single crystal diamond within a polycrystalline diamond matrix for use as an optical window is known. However, US 4260397 discloses a method of forming a single crystal-polycrystalline composite using a HPHT process. A single crystal diamond is embedded in the centre of a mass of diamond grains in a HPHT capsule which may also contain graphite and/or a metal catalyst. The capsule is subjected to HPHT conditions to form the composite. This method would appear to be not well designed to form large polycrystalline disks.

US 3895313 discloses the use of diamond windows for laser applications and suggests a number of mounting configurations. A single diamond is employed as a window while several other diamonds having a similar high thermal conductivity are located in intimate heat transfer relation with the window diamond and serve as a heat transfer means. The window and heat transfer diamonds are interfaced either directly or by the use of very thin metal foils or layers of thermally conductive metal such as gold or silver sputtered onto adjacent diamond surfaces. Adjacent diamond surfaces are mechanically lapped to tolerances of less than ten thousandths of an inch, followed by sputtering of the metal films onto the diamond surfaces in thicknesses of less than 50 microns, and preferably in the order of microns. The diamonds are maintained at as high a temperature as possible during sputtering, after which the surfaces are directly compressed, preferably in a vacuum. It is described that gold, silver, and platinum films in very good vacuum will weld to each other by purely diffusive means.

Subsequent melting of the metallic layers is prevented by the high thermal conductivity of the diamond on each side of the layer. The heat transfer diamonds may themselves be contacted by a metallic heat sink, which may contain interior channels for the flow of a coolant fluid.

W02005/010245 discloses a composite structure comprising a plurality of single crystal diamond plates adhered together by growing a layer of polycrystalline CVD diamond over an array of the single crystal diamond plates in a similar manner to US200SO 160968. It is also disclosed that the polyciystalline diamond grows between the plurality of single crystal diamond plates and the polycrystalline material disposed over the single crystal plates can be removed to form a structure in which a polycrystalline diamond layer is provided with embedded single crystal diamond plates exposed on both surfaces. As such the polyciystalline diamond forms a frame for the single crystal diamond plates. Window applications are suggested and it is disclosed that the polycrystalline frame provides a means of mounting and cooling a single crystal diamond windo\v. Altematives to direct adhesion of the single crystal diamond plates and the polycrystalline diamond material are suggested including gluing and brazing.

In light of the above, it is evident that the use of diamond as an optical component is known. Diamond material is useful as an optical component as it has low absorption.

Diamond material has the additional advantage over other possible window materials in that it is mechanically strong, inert, and biocompatible. For example, the inertness of diamond material makes ft an excellent choice for use in reactive chemical environments where other optical window materials would not be suitable. Further still, diamond material has very high thermal conductivity and a low thermal expansion coefficient. As such, diamond material is useful for use as an optical component in high energy beam applications where the component will tend to be heated. The diamond material will rapidly conduct away heat to cool areas where heating occurs so as to prevent heat build-up at a particular point, e.g. where a high energy beam passes through the material. To the extent that the material is heated, the low thermal expansion coefficient of diamond material ensures that the component does not unduly deform which may cause optical and/or mechanical problems in use.

One problem with using diamond as a window material is that the diamond window has a tendency to dc-bond from the optical tool to which ft is attached, for example due to chemical and/or thermal condftions. Another related problem when faced wfth designing an optical component for use in reactive chemical environments is how to improve diamond window bonding whilst also ensuring that the optical tool is chemically inert to the reactive chemical environments in which it is to be used. Yet another problem is that the best thermal and optical properties are achieved by using a single crystal diamond material. However, it is difficult to synthesize large area single crystal diamond layers, particularly layers which are sufficiently thick so as to form free standing optical components such as to form a free standing sheet of diamond material for use as a window. Accordingly, one solution is to use a composfte structure in which single crystal diamond material is bonded to a polycrystalline diamond wafer.

The present inventors have found that the vast majorfty of known bonding techniques are unsuftable for reliably bonding diamond material. This is largely due to the extreme rigidity of diamond material and the very low thermal expansion coefficient of diamond material which causes thermal expansion mismatch between the diamond material and adhesive material used to bond the diamond material. During use, changes in temperature cause strain build up in the adhesive material due to thermal expansion or contraction and failure of the adhesive material results. As such, the inventors have recognized that bonding diamond material is a somewhat unique problem due to the extreme properties of diamond material and much effort has been put into the identification of bonding techniques which can reliably bond diamond components without failure in use due to changes in temperature. This is particularly problematic as diamond material is often selected for a particular use when thermal management is a problem. This is due to diamonds extremely high thermal conductivity, low electrical conductivity, and low thermal expansion coefficient allowing the material to effectively remove heat from electronic components while not conducting away any charge and while retaining dimensional stability. However, diamonds apparent advantages in this regard have also been found to be problematic in that adhesive material which is adhered to the diamond material does not share diamonds extreme thermal properties and thus can fail due to a thermal mismatch between the adhesive material and the diamond material.

In light of the above problems, the obvious solution is to try to avoid the use of any adhesive material altogether and form a direct diamond-to-diamond bond. However, it has proved difficult to form such a reliable bond between single crystal diamond substrates and a polycrystalline diamond carrier layer. Indeed one problem with the method as described in JP 08-2083 87 is that a poor diamond-to-diamond bond tends to fonn between the polycrystalline diamond material and the single crystal diamond material. Another possible solution is to use an adhesive which is flexible so that the adhesive doesn't fracture due to strain imparted on the adhesive due to a thermal mismatch between the adhesive material and the diamond material. However, flexible adhesives tend to have a relatively low melting point and do not generally have good thermal conductivity leading to heat build up and melting in use.

Accordingly, it is an aim of certain embodiments of the present invention to at least partially solve one or more of the aforementioned problems. In particular, certain embodiments of the present invention seek to provide a diamond composite assembly which is stable, reliable, and has improved lifetime.

Summary of Invention

A first aspect of the present invention provides a composite diamond assembly comprising: a wafer of diamond material; and a diamond component mounted within an opening formed within the wafer of diamond material, the diamond component being formed of a different type of diamond material to that of the wafer, wherein the opening comprising a wedge-shaped or step-shaped side wall, wherein the diamond component is in the form of a plate having a front face and a rear face bounded by a wedge-shaped or step-shaped side wall which is complimentary to the wedge-shaped or step-shaped side wall of the opening, said front face having a larger surface area than said rear surface, and wherein the diamond component is mounted within the opening by a braze join disposed between the wedge-shaped or step-shaped side wall of the opening and the complimentary wedge-shaped or step-shaped side wall of the diamond component.

A second aspect of the present invention provides a method of manufacturing a diamond component as described above, the method comprising: forming an opening in a wafer of diamond material, the opening comprising a wedge-shaped or step-shaped side wall, and mounting a diamond component within the opening formed within the wafer of diamond material, wherein the diamond component being in the form of a plate having a front face and a rear face bounded by a wedge-shaped or step-shaped side wall which is complimentary to the wedge-shaped or step-shaped side wall of the opening, said front face having a larger surface area than said rear surface, wherein the diamond component is mounted within the opening by brazing together the wedge-shaped or step-shaped side wall of the opening and the complimentary wedge-shaped or step-shaped side wall of the diamond component to form a braze jo in.

A third aspect of the present invention provides an apparatus comprising the composite diamond assembly as described above, wherein the composite diamond assembly is mounted within the apparatus such that in normal usc a pressure at the rear face of the diamond component is tower than a pressure at the front face of the diamond component.

Brief Description of the Drawings

For a better understanding of the present invention and to show how the same may be carried into effect, embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 illustrates a plan view of a diamond window component according to an embodiment of the present invention; Figure 2 illustrates a cross-sectional view of a diamond window component according to an embodiment of the present invention; and Figure 3 illustrates a cross-sectional view of a diamond window component according to an altemative embodiment of the present invention.

Detailed Description of Certain Embodiments

Figures 1 and 2 itlustrate an embodiment of the present invention which comprises a single crystal diamond part 2 mounted in a potycrystalline diamond disc 4 using a braze join 6 in combination with a wedge-shaped mounting configuration. This arrangement has the following advantages: (1) The optical property benefits of single crystal diamond can be used for the best performance.

(2) The Polycrystalline material can be used for cooling and/or handling purposes.

(3) Due to wedged sides the window is self-aligning.

(4) The configuration is over-or under-pressure compatible as the pressure will press the window in its seat.

(5) The brazing material can be made thin so that the impact on the thermal conductivity is very limited and the thermal advantages of using diamond material are retained.

As such, the arrangement combines the advantages of single crystal and polycrystalline diamond material to obtain large area diamond windows with a region of high quality optical grade single crystal material. Furthermore, it has been found that the use of a braze join in combination with a wedge-shaped mounting configuration results in bond which is more stable that prior art configurations.

As an alternative to a wedge-shaped mounting configuration as illustrated in Figures 1 and 2, it is also envisaged that a step-shaped mounting configuration could be utilized and provide many of the same advantageous features. Such an alternative configuration is illustrated in Figure 3. In relation to Figures 2 and 3 it should be noted that the components have been expanded and illustrated as being separate so as to illustrate the individual components clearly. In practice, during brazing the components are in intimate contact with a portion of the single crystal diamond part 2 overlapping with a portion of the polycrystalline diamond disc 4 such that the largest diameter of the single crystal diamond part is larger than the smallest diameter of the opening within the polycrystalline diamond disc. This arrangement will prevent the possibility of the single crystal diamond part being pushed through the opening within the polyciystalline diamond disc.

Further still, it is envisaged that the mounting configuration may also be useful for non-single crystal diamond components. For example, a polycrystalline diamond plate may be mounted within a polycrystalline diamond carrier wafer, the diamond material used for the plate and the carrier wafer having different optical, thermal, and/or electronic characteristics. Such a configuration may be useful when it is difficult to form large areas of very high quality polycrystalline diamond material in which case a smaller area of high quality polyciystalline diamond material may be fabricated and mounted within a larger area of lower quality polycrystalline diamond material.

For certain applications, a synthetic single crystal CYD diamond material may be used as the central component although natural or synthetic HPHT diamond material may alternatively be used. A synthetic polycrystalline CYD diamond material may be used as the carrier wafer. However, it is also envisaged that other diamond materials may be used for the carrier wafer including, for example, composite materials such as PCD and ScD.

Accordingly, certain embodiments will include the following common features: a wafer of diamond material; and a diamond component mounted within an opening formed within the wafer of diamond material, the diamond component being formed of a different type of diamond material to that of the wafer, wherein the opening comprising a wedge-shaped or step-shaped side wall, wherein the diamond component is in the form of a plate having a front face and a rear face bounded by a wedge-shaped or step-shaped side wall which is complimentary to the wedge-shaped or step-shaped side wall of the opening, said front face having a larger surface area than said rear surface, and wherein the diamond component is mounted within the opening by a braze join disposed between the wedge-shaped or step-shaped side wall of the opening and the complimentary wedge-shaped or step-shaped side wall of the diamond component.

Preferred braze materials for forming the braze join including the following: Au/Sn (for example in a mass ratio of 80/20); Au/Ge (for example in a mass ratio of 88/12); Cu/Ag (for example in a mass ratio of 72/28); Cu/Ag/Ti (for example in a mass ratio of 72/27/1); AuSi; or Au/Ta. A Cu/Ag/Ti braze is preferred for many applications.

The braze join may have a thickness in a range: 0.5 to 10.0 jim; 1.0 to 8.0 jim; 2.0 to 6.0 jim; or 3.0 to 6.0 jim. The thickness may be selected such that the braze join is sufficiently thick to form a reliable bond while being sufficiently thin that it doesn't unduly reduce the thermal conductivity of the composite diamond assembly.

The side wall of the opening and the side wall of the diamond component are complementary to an extent that a difference in angle between the respective side walls is no more than 30°, 20°, 10°, 5°, 2°, or 1°. Although it can be preferable to have completely complementary surfaces for mounting the component into the wafer, it is envisaged that some variation from complete complimentary surfaces may be allowable.

The opening is preferably substantially circular and the diamond component is preferably a circular disk as illustrated in Figure 2. It has been found that the most reliable bonding can be achieved using a substantially circular arrangement to provide more uniform stresses and avoid stress-peaks leading to bonding failure. However, it is also envisaged that other shapes could be used according to the required application.

The front and rear faces of the diamond component may be parallel to within 300, 200, 50, 2°, or 1°. For example, the diamond component may form a simple window type structure. Alternatively, more complex diamond component structures may be provided. For example, the front and/or rear faces of the single crystal diamond component may comprise an optical outcoupling structure such as one or more of: an angled surface; a convex surface; a microlens array; a solid immersion lens (SIL); a plurality of surface indentations or nano-structures; a diffraction grating; a fresnel lens; and a coating such as an antircflcctive coating.

The diamond component may be formed of a diamond material having one or more of the following characteristics: an absorption coefficient in a range 0.01 to 0.05 cni1 at a wavelength of 10.6 jim; an absorption coefficient in a range 0.0001 to 0.03 cm', 0.0003 to 0.01 cm1, or 0.0003 to 0.005 crri1 at a wavelength of 1.064 jim; and a birefringence (ne-no) in a range 5 x io4 to 1 x 108, 1 x l0 to 5 x 10, or S x io5 to 1 xlO The wafer of diamond material may be formed of a diamond material having one or more of the following characteristics: a thermal conductivity in a range 1500 to 2200 Wnt'K1 at a temperature of 300 K; and a Young's modulus in a range 1000 to 1100 GPa.

The diamond component may be formed and mounted such that the rear face of the diamond component (i.e. the smaller area face) is more resistant to tensile stress than the front face of the diamond component. For example, polycrystalline diamond material having a smaller average grain size tends to be more resistant to tensile stress. Furthermore, as synthetic polycrystalline OlD diamond material grows, the grain size of the as-grown layer increases. Thus, a nucleation surface will have a smaller grain size than a growth surface. Accordingly, a diamond component may be formed and mounted with the rear face having a smaller average grain size than the front face. The composite diamond assembly can then be mounted within an apparatus such that in normal use a pressure at the rear face of the diamond component is lower than a pressure at the front face of the diamond component. This will result in the diamond component being pressed into the wedge-shaped or step-shaped seat. Furthermore, the rear face will be placed in tension. Accordingly, it is desirable for this face to be more resistant to tensile stress.

A method of manufacturing a diamond component as previously described may comprise: forming an opening in a wafer of diamond material, the opening comprising a wedge-shaped or step-shaped side wall, and mounting a diamond component within the opening formed within the wafer of diamond material, wherein the diamond component being in the form of a plate having a front face and a rear face bounded by a wedge-shaped or step-shaped side wall which is complimentary to the wedge-shaped or step-shaped side wall of the opening, said front face having a larger surface area than said rear surface, wherein the diamond component is mounted within the opening by brazing together the wedge-shaped or step-shaped side wall of the opening and the complimentary wedge-shaped or step-shaped side wall of the diamond component to form a braze join.

The opening may be formed by cutting, for example, using a laser.

The brazing may be performed at a temperature in a range 200 to 1500°C or 250 to 1250°C. The preferred temperature will depend on the type of material used for the braze. For example, the brazing may be performed at a temperature in a range 250 to 300°C for an Au/Sn braze material, a temperature in a range 750 to 850°C for a Cu/Ag braze material, a temperature in a range 900 to 1000°C for a Cu/Ag/Ti braze material, or a temperature in a range 1200 to 1250°C for an Au/Ta braze material. The braze may be performed under vacuum or a protective atmosphere. Protective atmospheres include, but are not limited to, argon, argonlhydrogen, nitrogen, or nitrogcnlhydrogen.

The diamond component may be formed by growing synthetic CYD diamond material and slicing the as grown synthetic CVD diamond material in a direction within 45°, 30°, 20°, 10°, or 5° of the growth direction to form a plate in which the font and rear faces have a larger surface area than a side wall bounding the front and rear faces, the font and rear faces being formed of surfaces lying in a plane within 45°, 30°, 20°, 10°, or 5° of the growth direction, the plate being further processed to form a wedge-shaped or step-shaped side wall. Such a method can be advantageous as dislocation defects tend to form in the CVD growth direction. By slicing the as grown material in a direction approximately parallel to the growth direction then a plate can be formed in which dislocation defects extend approximately parallel to front and rear surfaces. This results in a low birefringencc of light passing through the plate in a direction approximately perpendicular to the front and rear surfaces of the plate. A plate of synthetic single crystal CYD diamond can be formed in this manner.

The diamond component may ahematively be formed by growing synthetic polycrystalline CVD diamond material and slicing the as grown synthetic CVD diamond material in a direction within 45°, 30°, 20°, 10°, or 5° to a normal of the growth direction to form a plate in which the font and rear faces have a larger surface area than a side wall bounding the front and rear faces, the font and rear faces being formed of surfaces lying in a plane within 45°, 30°, 20°, 10°, or 5° of the normal to the growth direction, the plate being further processed to form a wedge-shaped or step-shaped side wall with the rear face being formed by a plane closer to a nucleation surface of the as grown synthetic polycrystalline CYD diamond material relative to the front surface whereby the rear surface has a smaller average grain size than the front face. This method can be used to form polycrystalline diamond components which can be oriented such that the rear surface (i.e. the one which will be in tensile stress in normal use) is more resistant to tensile stress and cracking.

An apparatus comprising the composite diamond assembly may be provided wherein the composite diamond assembly is mounted within the apparatus such that in normal use a pressure at the rear face of the diamond component is lower than a pressure at the front face of the diamond component. For example, the rear surface of the diamond component may be disposed on the inside of a low pressure chamber.

Alternatively, the rear surface of the diamond component may be disposed on the outside of a high pressure chamber. For certain applications, the wafer may comprise more than one opening in which a diamond component is mounted such that a composite diamond assembly is provided with a plurality of diamond components.

In order to mount the composite diamond assembly within an apparatus it can be advantageous to bond the composite diamond assembly to a mounting ring which is made of a material having a coefficient of linear thermal expansion a of 14 x 106 IC1 or less at 20°C and a thermal conductivity of 60 Wnt1IC' or more at 20°C. For example, the mounting ring may have a coefficient of linear thermal expansion a which is 12 x 106 IC1or less, 10 x 106 j1 or less, 8 x 106 IC1 or less, 6 x 106 IC' or less, or 4 x 1 06 K1 or less and/or a thermal conductivity of 60 Wm1 IC' or more, 80 or more, 100 or more, 120 or more, or 140 or more. Such a mounting ring aids in preventing heat build-up and thermal expansion mismatch at the mounting between the composite diamond assembly and the surrounding apparatus. Examples of suitable materials for the mounting ring include one or more of molybdenum, chromium, tungsten, nickel, rhodium, ruthenium, silicon carbide (SiC), tungsten carbide (WC), aluminium nitride (A1N), molybdenum alloys such as titanium zirconium molybdenium (TZM), and tungsten alloys such as tungsten nickel iron (WNiFe) and tungsten nickel copper (WNiCu). Molybdenum has been found to be particularly useful as it can readily be manufactured into a mounting ring, has a low thermal expansion coefficient of 5 x 1 06 IC', and has a relatively high thermal conductivity of 144 Wnf'IC'. The composite diamond assembly may be bonded to such a mounting ring by brazing.

While this invention has been particularly shown and described with reference to preferred embodiments, it will be understood to those skilled in the art that various changes in form and detail may be made without departing from the scope of the invention as defined by the appendant claims.

Claims

Claims 1. A composite diamond assembly comprising: a wafer of diamond material; and a diamond component mounted within an opening formed within the wafer of diamond material, the diamond component being formed of a different type of diamond material to that of the wafer, wherein the opening comprising a wedge-shaped or step-shaped side wall, wherein the diamond component is in the form of a plate having a front face and a rear face bounded by a wedge-shaped or step-shaped side wall which is complimentary to the wedge-shaped or step-shaped side wall of the opening, said front face having a larger surface area than said rear surface, and wherein the diamond component is mounted within the opening by a braze join disposed between the wedge-shaped or step-shaped side wall of the opening and the complimentary wedge-shaped or step-shaped side wall of the diamond component.
2. A composite diamond assembly according to claim 1, wherein the diamond component is formed of a single crystal diamond plate or a polycrystalline diamond plate having different optical, thermal, and/or electronic characteristics to that of the diamond material of the wafer.
3. A composite diamond assembly according to claim 1 or 2, wherein the diamond component is formed of synthetic single crystal CVD diamond material.
4. A composite diamond assembly according to any preceding claim, wherein the wafer is formed of a synthetic polycrystalline CVD diamond material.
5. A composite diamond assembly according to any preceding claim, wherein the braze join comprises: Au/Sn; Cu/Ag; Cu/Ag/Ti; Au/Ge; Au/Si; or Au/Ta.
6. A composite diamond assembly according to any preceding claim, wherein the braze join has a thickness in a range: 0.5 to 10.0 xm; 1.0 to 8.0 lIm; 2.0 to 6.0 rim; or 3.0 to 6.0 tm.
7. A composite diamond assembly according to any preceding claim, wherein the side wall of the opening and the side wall of the diamond component are complementary to an extent that a difference in angle between the respective side walls is no more than 300, 20°, 10°, 5°, 2°, or 1°.
8. A composite diamond assembly according to any preceding claim, wherein the opening is substantially circular and the diamond component is a circular disk.
9. A composite diamond assembly according to any preceding claim, wherein the front and rear faces of the diamond component are parallel to within 30°, 20°, 10°, 5°, 2°, or 1°.
10. A composite diamond assembly according to any preceding claim, wherein the diamond component is formed of a diamond material having one or more of the following charactersistic: an absorption coefficient in a range 0.01 to 0.05 cm1 at a wavelength of 10.6 lIm; an absorption coefficient in a range 0.000 1 to 0.03 cm' at a wavelength of 1.064 Mm; and a birefringence (ne-no) in a range S x i04 to 1 x io8.
11. A composite diamond assembly according to any preceding claim, wherein the wafer of diamond material is formed of a diamond material having one or more of the following characteristics: a thermal conductivity in a range 1500 to 2200 Wn11K1 at a temperature of 300 K; and a Young's modulus in a range 1000 to 1100 GPa.
12. A composite diamond assembly according to any preceding claim, wherein the rear face of the diamond component is more resistant to tensile stress than the front face of the diamond component.
13. A composite diamond assembly according to any preceding claim, wherein the diamond component is formed of polycrystalline diamond material, the rear face having a smaller average grain size than the front face.
14. A composite diamond assembly according to any preceding claim, wherein the front and/or rear faces of the single crystal diamond component comprise an optical outcoupling structure.
15. A composite diamond assembly according to claim 14, wherein the optical outcoupling structure comprises one or more of: an angled surface; a convex surface; a micro lens array; a solid immersion lens (SIL); a plurality of surface indentations or nano-structures; a diffraction grating; a fresnel lens; and a coating such as an antireflective coating.
16. A composite diamond assembly according to any preceding claim, wherein the wafer comprises more than one opening in which a diamond component is mounted.
17. A method of manufacturing a diamond component according to any preceding claim, the method comprising: forming an opening in a wafer of diamond material, the opening comprising a wedge-shaped or step-shaped side wall, and mounting a diamond component within the opening formed within the wafer of diamond material, wherein the diamond component being in the form of a plate having a front face and a rear face bounded by a wedge-shaped or step-shaped side wall which is complimentary to the wedge-shaped or step-shaped side wall of the opening, said front face having a larger surface area than said rear surface, wherein the diamond component is mounted within the opening by brazing together the wedge-shaped or step-shaped side wall of the opening and the complimentary wedge-shaped or step-shaped side wall of the diamond component to form a braze Jo in.
18. A method according to claim 17, wherein the diamond component is formed by growing synthetic CYD diamond material and slicing the as grown synthetic CVD diamond material in a direction within 45°, 300, 20°, 100, or 50 of the growth direction to form a plate in which the font and rear faces have a larger surface area than a side wall bounding the front and rear faces, the font and rear faces being formed of surfaces lying in a plane within 45°, 30°, 200, 10°, or 5° of the growth direction, the plate being further processed to form a wedge-shaped or step-shaped side wall.
19. A method according to claim 18, wherein the synthetic CYD diamond material is synthetic single crystal CVD diamond material.
20. A method according to claim 19, wherein the diamond component is formed by growing synthetic polyerystalline CVD diamond material and slicing the as grown synthetic CVD diamond material in a direction within 45°, 30°, 20°, 10°, or 5° to a normal of the growth direction to form a plate in which the font and rear faces have a larger surface area than a side wall bounding the front and rear faces, the font and rear faces being formed of surfaces lying in a plane within 45°, 30°, 20°, 10°, or 5° of the normal to the growth direction, the plate being further processed to form a wedge-shaped or step-shaped side wall with the rear face being formed by a plane closer to a nucleation surface of the as grown synthetic polycrystalline CYD diamond material relative to the front surface whereby the rear surface has a smaller average grain size than the front face.
21. A method according to any one of claims 18 to 21, wherein the brazing is performed at a temperature in a range: 200 to 1500°C; 250 to 1250°C; 250 to 300°C for an Au/Sn braze material; 750 to 850°C for a Cu/Ag braze material; 900 to 1000°C for a Cu/Ag/Ti braze material; or 1200 to 1250°C for an Au/Ta braze material.
22. A method according to any one of claims 18 to 21, wherein the brazing is performed under vacuum or a protective atmosphere.
23. An apparatus comprising the composite diamond assembly according to any one of claims 1 to 16, wherein the composite diamond assembly is mounted within the apparatus such that in normal use a pressure at the rear face of the diamond component is lower than a pressure at the front face of the diamond component.