HK1127789B - Single crystal diamond - Google Patents

Description

Single crystal diamond

The application is a divisional application of Chinese patent application with the name of 'single crystal diamond', the application date of which is 9/19/2003 and the application number of 03822264.7(PCT/IB 03/04057).

Background

The present invention relates to single crystal diamond.

Diamond provides a range of unique properties including optical transmission, thermal conductivity, rigidity, abrasion resistance and its electronic properties. Although many of the mechanical properties of diamond can be achieved in more than one type of diamond, other properties are very sensitive to the type of diamond used. For example, CVD single crystal diamond is important to obtain the best electronic performance, often superior to polycrystalline CVD diamond, HPHT diamond and natural diamond.

In many diamond applications, the limited lateral dimensions of the diamond that can be obtained is a significant limitation. Polycrystalline CVD diamond layers substantially solve this problem for applications where polycrystalline structures are desirable, but polycrystalline diamond is not suitable in many applications.

While natural and HPHT diamonds may not be suitable for certain applications, they are used as substrates on which to grow CVD diamonds. While the substrate may have a variety of crystallographic orientations, the maximum and optimum substrate orientation that can be produced for high quality CVD diamond growth is typically (001). In the present specification, the Miller indices { hk1} defining a plane based on the axes x, y, z are described assuming that the z direction is a direction perpendicular to the substrate surface and parallel to the growth direction. Thus, the axes x, y are within the plane of the substrate and are generally equivalent due to symmetry, but differ from z due to the growth direction.

Large natural single crystal diamonds are extremely rare and expensive and large natural diamond substrate plates suitable for CVD diamond growth have not been seen because of the very high economic risks associated with their manufacture and use. Natural diamond is often strained and defective, especially in larger substrate plates, and this can cause twinning and other problems in CVD overgrowth, or fracture during synthesis. In addition, dislocations that are ubiquitous in natural diamond substrates are replicated in the CVD layer, also reducing its electronic properties.

HPHT synthetic diamonds are also limited in size and are generally of poor quality in larger stones, with inclusions being a major problem. Larger plates made from synthetic diamond often exhibit missing corners such that edge facets (e.g., 110) that differ from 100 are present, or they may contain inclusions or be strained. During synthesis, additional facets such as 111 are formed, which lie between the (001) top surface and the 110 side surface (see FIG. 1 of the drawings). In recent years, great efforts have been directed to the synthesis of high quality HPHT diamond for applications such as monochromators, and some progress has been reported, but the size of HPHT plates suitable for use as substrates remains limited.

In thick layer CVD synthesis, it is generally known that especially the 111 planes will form twins, limiting the area of perfect single crystal growth during synthesis and often leading to degradation and even breakage and further deterioration due to thermal stress caused by growth temperature. Twinning on 111 interferes particularly with the increase in the size of the largest plate that can be made from the (001) major face and is bounded by 100 side faces.

When bounded by a 100 side, a (001) substrate of up to about 7mm can be obtained in general²And when bounded by the 100 and 110 sides, the major face width may be up to about 8.5 mm.

CVD homoepitaxial synthesis of diamond involves epitaxial growth of CVD on existing diamond plates and the process is described in detail in the literature. This is of course still limited by the availability of existing diamond plates. To obtain a larger area, attention is also focused on lateral growth to increase the total area of the overgrown plate. Such a process is described in EP 0879904.

An alternative to homoepitaxial growth is heteroepitaxial growth, in which the growth is carried out on a non-diamond substrate using an epitaxial method. However, in all reported cases, the products of this method are clearly different from those of homoepitaxial growth, which has low-angle boundaries between highly oriented but not precisely oriented regions. These boundaries seriously degrade the performance of the diamond.

Homoepitaxial diamond growth to enlarge the area of the CVD plate presents a number of difficulties.

If ideal homoepitaxial growth can be achieved on a diamond plate, the growth that can be achieved is substantially illustrated by figures 1 and 2 of the accompanying drawings. The illustrated growth morphology assumes that there is no competing polycrystalline diamond growth. In practice, however, there is often competition from polycrystalline growth, i.e., growth from the surface on which the diamond substrate plate is secured. This is illustrated by figure 3 of the accompanying drawings.

Referring to fig. 3, a diamond substrate plate 10 is provided that is secured to a surface 12. Examples of materials for surface 12 include molybdenum, tungsten, silicon, and silicon carbide. During CVD diamond growth, single crystal diamond growth will occur on the (001) plane 14 and on the side planes, two of which 16 are shown. The side surface 16 is a 010 plane. Growth also occurs at the corners and vertices 18 of the plate and extends outward therefrom. All such growth will be homoepitaxial single crystal growth. The growth on each face present on the substrate and on any new surface created during the growth process constitutes a growth zone. For example, in FIG. 3, diamond growth 24 originates from the 101 plane and is therefore the 101 growth zone.

Competing with homoepitaxial single crystal growth would be polycrystalline diamond growth 20 occurring on the surface 12. Depending on the thickness of the layer of single crystal diamond produced on the surface 14, the polycrystalline diamond growth 20 may be in good contact with the homoepitaxial single crystal diamond growth along the line 22 as shown in figure 3.

Based on fig. 2, one may expect that pure lateral growth on the substrate sides may be used to make larger substrates including the original substrate material. However, as is clear from fig. 3, such plates actually contain competing polycrystalline growth. Plates fabricated parallel to the original substrate, but higher up on the growth layer, are likely to contain twins, particularly material from the 111 growth regions.

Under growth conditions where polycrystalline diamond does not compete with single crystal diamond, there may still be problems with the generally poor quality of lateral single crystal growth due to the different geometries and processing conditions present at the edge of the diamond substrate, which is exacerbated by the method used to inhibit polycrystalline growth.

Defects in the substrate used for CVD diamond growth replicate into the layer grown thereon. Obviously, since the method is homoepitaxial, the regions such as twins are continued in the new growth. Furthermore, structures such as dislocations are continued because, due to their basic nature, threading dislocations cannot simply self-terminate, but the probability of two opposing dislocations annihilating is small. Each time the growth process begins, other dislocations will form, mainly on the surface non-uniformities, which may be etch pits, dust particles, growth zone boundaries, etc. Dislocations are therefore a particular problem in single crystal CVD diamond substrates and in a series of growths in which overgrowth from one process is used as the substrate for the next growth, the dislocation density tends to increase significantly.

Summary of The Invention

According to the present invention, a method of producing a plate of single crystal diamond comprises the steps of: providing a diamond substrate having a surface substantially free of surface defects, homoepitaxially growing diamond on said surface by Chemical Vapour Deposition (CVD), and cutting said homoepitaxially CVD grown diamond and said substrate, typically perpendicularly (i.e. at 90 ° or close to 90 °) across the surface of the substrate on which diamond growth is carried out, to produce a single crystal CVD diamond plate.

Homoepitaxial CVD diamond growth on the surface of the substrate is preferably carried out according to the method described in WO 01/96634. In particular, using this method, thick, high purity single crystal diamond can be grown on a substrate. A growth thickness of homoepitaxially grown CVD diamond of greater than 10mm, preferably greater than 12mm, more preferably greater than 15mm may be achieved. Thus, by the method of the invention, it is possible to produce a single crystal CVD diamond plate having at least one linear dimension in excess of 10mm, preferably in excess of 12mm, more preferably in excess of 15 mm. "linear dimension" refers to any linearly measured dimension taken between two points on or adjacent to a major surface. For example, such a linear dimension may be the length of an edge of the substrate, a measured dimension from one edge or point on an edge to the other edge or another point on the edge, an axis, or other similar measured dimension.

In particular, rectangular (001) single crystal diamond plates, bounded by {100} side faces, or by faces having at least one linear dimension, such as a linear <100> edge dimension, exceeding 10mm, preferably exceeding 12mm, more preferably exceeding 15mm, may be produced by the method of the invention.

The single crystal CVD diamond plate produced by the present method may then itself be used as a substrate in the method of the present invention. Thick single crystal CVD diamond can be homoepitaxially grown on the major surfaces of the plate.

According to another aspect, the invention provides a plate of (001) single crystal CVD diamond having major surfaces with opposite sides bounded by 100 side surfaces, i.e. a plate in which the major surfaces are 001 surfaces, each major surface having at least one linear dimension exceeding 10 mm. In one form of the invention, the plate is rectangular, square, parallelogram or the like in shape, with at least one side, preferably both sides, having a dimension of more than 10mm, preferably more than 12mm, more preferably more than 15 mm. Most preferably, these side surfaces are 100 surfaces or faces, such that the edge dimension (or edge dimensions) of the plate exceeding 10mm is in the <100> direction. Also, the method of the present invention provides a larger diamond plate or block from which such plates defined by 100 side faces and 001 major faces can be manufactured.

In homoepitaxial diamond growth on the surface of a diamond substrate, any dislocations or defects in the surface, or generated at the interface with the substrate, or originating from the edges of the substrate, generally propagate vertically in the diamond growth. Thus, if the cut is made substantially perpendicular to the surface on which diamond growth is to occur, the cut surface will be substantially free of dislocations in the material across the surface, as the dislocations generally propagate parallel to the surface. Thus, by repeating the method using this new plate as a substrate, a reduction in dislocation density in the body of material can be achieved, and by cutting the major surface of any plate cut perpendicular to the substrate, a further reduction in dislocation density can be achieved. Furthermore, there are applications that benefit from plates in which the dislocations present run generally parallel to the major faces rather than generally perpendicular to the major faces.

Typically, the highest quality CVD growth is the growth contained within the vertical (001) growth zone. Moreover, because the edges of the substrate can form dislocations and these dislocations generally propagate vertically upward, the highest quality CVD growth volume is the volume defined by the vertical planes rising upward from the substrate edges. The method of the invention enables one or more new large area plates to be manufactured completely from this volume, thereby minimising defects in the plates and optimising their crystal quality.

By combining the various features of the invention, a product can be produced having a higher degree of consistency than the originalThe lower dislocation density of the matrix material, diamond, the lower limit of which is determined only by the number of times the method is repeated. In particular, the large area plates of the invention and any layers subsequently synthesized thereon, typically in the surface perpendicular to the growth direction (such surface generally exhibiting the highest dislocation density in CVD diamond), may have a dislocation density of less than 50/mm²Preferably less than 20/mm²More preferably less than 10/mm²More preferably less than 5/mm²The dislocation density of (a). The defect density can be most easily characterized by optical evaluation after optimized plasma or chemical etching using exposed defects (referred to as exposed plasma etching), for example using a short plasma etch of the type described in WO 01/96634. Furthermore, for applications where dislocation density within the major face of the plate is a major concern, the plate made by the method of the present invention may exhibit less than 50/mm on its major face²Preferably less than 20/mm²More preferably less than 10/mm²More preferably less than 5/mm²The dislocation density of (a).

Where the substrate is a natural substrate or a HPHT synthetic substrate, it is generally not advantageous for the vertically cut plate to include material from the original substrate, although this may be done. When the substrate itself is a CVD diamond plate that can be produced by the present method, it may be advantageous to include material from the substrate in this plate.

Brief Description of Drawings

FIG. 1 is a schematic perspective view of a diamond plate on which ideal homoepitaxial diamond growth has been performed;

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a cross-sectional view through a diamond plate illustrating single crystal diamond growth and polycrystalline diamond growth;

FIG. 4 is a cross-sectional view through a diamond plate on which homoepitaxial diamond growth has been performed according to an embodiment of the present invention;

FIG. 5 is a schematic view of a diamond plate showing the angle α of the dislocation direction relative to the major surfaces of the diamond plate; and

fig. 6 is a schematic view of a diamond plate showing the angle β of the dislocation direction relative to the normal to the major surfaces of the diamond plate.

Description of the embodiments

Embodiments of the present invention will now be described with reference to the accompanying drawings. Referring to fig. 4, a diamond plate 30 is provided. The diamond plate 30 is a single crystal diamond plate. The upper surface 32 is a (001) surface, and the side surfaces 34 are {010} surfaces. Surface 32 is substantially free of surface defects, in particular it is substantially free of crystal defects as described in WO 01/96634.

Diamond growth 36 is performed on the diamond substrate 30 according to the method described in WO 01/96634. This diamond growth occurs vertically on the upper surface 32, outward from the corners 38 and outward from the sides 34 of the substrate 30. This diamond growth is generally homoepitaxial, single crystalline and of high quality, although dislocations and twins may be present on the 111 as previously described.

Inevitably, some polycrystalline diamond growth will occur on the surface on which the substrate is placed. Depending on the thickness of the diamond growth region 36, this polycrystalline diamond growth may contact the lower surface 40 of this region.

Once the desired thickness of diamond growth 36 has been performed, the diamond growth region 36 and substrate 30 are cut perpendicular (approximately 90 °) to the surface 32, as illustrated by dashed line 44. This produces a high quality single crystal diamond plate 46. For practical purposes, the interface between the original substrate and the diamond growth is indistinguishable from the bulk of the sample. The original matrix material may form a portion of the plate 46 or may be removed from the plate 46. More than one plate may be produced, each parallel to the next and perpendicular to the substrate.

Using the method of WO01/96634, diamond growth regions 36 having a depth in excess of 10mm can be produced. Thus, the diamond plate 46 produced will have sides 48 that are more than 10mm in length.

The plate 46 may be used as a substrate for the method of the invention. Thus, if plate 46 has sides 48 greater than 10mm in length and diamond growth of greater than 10mm thickness is produced on major surface 50 of the plate, a square, rectangular or similar shaped plate can be produced with all four sides of the plate being greater than 10mm in length.

The cut in fig. 4 is shown as being made perpendicular to surface 32. The cut may be made at an angle that is not perpendicular to the face 32, except for a plate that is parallel to the substrate. When the substrate has a (001) major face, cutting the produced plate at an angle that is not perpendicular to the substrate will have a major face other than 100, for example 110, 113, 111, or higher order planes.

Also, the cut may be made along a plane at right angles to the cut plane 44 of FIG. 4, which would also result in a plate having a {100} major face, or at any other angle relative to the cut plane 44, which would result in a plate having a { hk0} type major face. To achieve a single crystal diamond plate, some trimming of polycrystalline or defective growth at the edges may be necessary.

Those skilled in the art will recognize that the conventional method need not be limited to substrates having a (001) major face, but may be equally applicable to other substrates having, for example, a 110, 113 or even 111 major face, but in general the preferred method is to use a substrate having a (001) major face, since the highest quality CVD diamond growth can be grown on this face most easily, and the arrangement of facets formed by CVD grown on such a face is generally most suitable for the production of large plates cut from the grown material.

For this reason, in a substrate plate having a (001) main surface, the critical dimension is the largest rectangular plate that can be manufactured, defined only by the {100} side surfaces. Growth on this plate can produce a plate defined by 110 side surfaces or by surfaces rotated 45 deg., as shown in fig. 1, relatively easily because this makes limited or no use of material from the 111 growth zone. This new plate defined by 110 side surfaces is at least twice as large as the plate defined by 100, but the original plate defined by 100 is still typically the largest inscribed (100) plate that can be produced from it. Thus, reference in this specification to the size of a single crystal diamond plate having a (001) major face generally refers explicitly to the size of the largest area inscribed rectangular plate bounded by 100 edges, if the plate already has no 100 edges.

The use of the method of the invention makes it possible to manufacture products which were not possible before. For example, large area windows, where it is not possible to achieve with small window sub-assemblies due to clear aperture (clear aperture), support, mechanical integrity, vacuum integrity, etc., can now be achieved. High voltage devices are also possible where a large area provides protection against electrical arcs around the active area of the device. The low dislocation density material of the present invention also enables applications such as electronic devices in which dislocations act as carrier traps or electronic shorts.

The growth direction of the CVD diamond layer may generally be determined by the dislocation structure therein. There are a range of possible structures:

1) the simplest case is one in which the dislocations are all substantially parallel and grow in the direction of growth, so that the direction of growth is clear.

2) Another common situation is where dislocations are slowly evolving around the growth direction, usually exhibiting some form of symmetry around the growth direction, and the angle on either side of this axis is typically less than 20 °, more typically less than 15 °, more typically less than 10 °, and most typically less than 5 °. Again, from the small area of the CVD diamond layer, the growth direction can be easily determined by dislocations.

3) Sometimes the growth plane itself is not at right angles to the local growth direction, but deviates from this by some small angle. In this case, the dislocations may be biased toward a direction perpendicular to the substrate surface of the growth region in which the dislocations are found. Especially near the edges, the growth direction may deviate significantly from the bulk of the layer, for example at 101 edges at an oblique angle to the substrate with 001 major growth planes. In both cases, looking at the entire matrix, the general growth direction is clearly seen from the dislocation structure, but it is also clear that the material is formed from more than one growth region. In applications where the direction of dislocations is important, it is often desirable to use material from only one growth region.

In the present specification, the direction of dislocation is a direction that is shown to be the growth direction of the layer based on the dislocation distribution analysis of the above model. Typically and preferably, the direction of the dislocations within a particular growth region will be the average direction of the dislocations using vector averaging, and wherein at least 70%, more typically 80%, more typically 90% of the dislocations lie in directions within 20 °, more preferably within 15 °, still more preferably within 10 °, and most preferably within 5 ° of the average direction.

The direction of the dislocations can be determined by, for example, an X-ray topography. This method does not require resolution of individual dislocations, but can resolve dislocation bundles, typically with an intensity that is partially proportional to the number of dislocations in the bundle. Simply or preferably, the intensity weighted vector average can then be derived from a topological plot drawn in cross section of the plane along the dislocation direction, where the topological plot taken perpendicular to that direction is unique in that it has a pattern of dots rather than a line pattern. In case the original growth direction of the plate is known, then this is a sensible starting point from which the direction of the dislocations can be determined.

After the dislocation direction has been determined according to the above method, its orientation may be classified with respect to the major faces of the single crystal CVD diamond plate. Referring to fig. 5, a diamond plate 60 has opposite major surfaces 62 and 64. A dislocation direction generally indicated by line 66 is considered to be generally oriented parallel to the major faces 62, 64 of the diamond plate 60 if the dislocation direction 66 is at an angle a of less than 30, preferably less than 20, more preferably less than 10, and most preferably less than 5 to the plane 68, 70 of at least one major face 62, 64 of the plate 60. This dislocation orientation is typically achieved when the single crystal CVD diamond plate is cut substantially perpendicular to the substrate on which it is grown, particularly when the single crystal CVD diamond plate is cut from the highest quality CVD growth contained within the vertical (001) growth zone.

Applications benefiting from dislocation directions generally parallel to the major faces include optical applications in which the effect on the refractive index change observed along a beam of light passing through the plate will significantly reduce propagation compared to that observed when the same dislocation distribution is substantially perpendicular to the major surfaces. Such applications benefit from the possibility of producing panels with transverse dimensions all exceeding 2mm, more preferably 3mm, still more preferably 4mm, more preferably 5mm and even more preferably 7mm, as is now made possible by the method of the invention.

Other applications that benefit from selecting the direction of the dislocations that is generally parallel to the major faces of the plates are applications using high voltages, where the dislocations may cause shorts in the direction of the applied voltage.

Another application is the application of laser windows (laser windows), where the influence of a light beam propagating parallel to the dislocations may increase the local electric field and cause failure. This can be controlled by deviating the dislocation direction from the beam direction or, preferably, by setting the dislocation direction parallel to the main surface of the laser window, thereby making it at right angles to the incident laser beam. Thus, a maximum laser damage threshold can be achieved by implementing the method of the present invention.

Another way to classify the dislocation direction is its orientation relative to the normal to the major faces of the plate. Referring to fig. 6, diamond plate 80 has opposite major surfaces 82 and 84. If the angle β between the dislocation direction 86 and the normal 88, as determined by the above method, exceeds 20 °, more preferably 30 °, still more preferably 40 °, and most preferably 50 °, the dislocation direction 86 is considered to be offset from the normal 88 to at least one of the major surfaces 82, 84 of the plate. This dislocation orientation is typically achieved when cutting a single crystal CVD diamond plate at an angle to the surface of the substrate on which it is grown. Alternatively, such dislocation orientation may occur where the plate is cut substantially perpendicular to the substrate on which growth is occurring, but in regions where the growth plane itself is not parallel to the original substrate surface, such as in the 101 growth region of a layer grown on a (001) substrate.

By ensuring that the dislocation direction is only offset from the normal to at least one major face of the plate, significant benefits may be realized in certain applications. There is a need in the application of diamond to etalons.

The invention will be further understood by reference to the following non-limiting examples.

Example 1

Two 001 synthetic diamond substrates for CVD diamond growth were prepared according to the method described in WO 01/96633. Layers were then grown on top of these diamond substrates to a thickness of 6.7 mm. The dislocation direction of the layer was characterized and it was found that 90% or more of the dislocations visible by X-ray topography were within 20 ° of the growth direction and 80% or more of the dislocations were within 10 ° of the growth direction.

One plate is cut out of each of these layers, with the major face of each plate having a dimension > 6 x 5mm and the growth direction being in the plane of the major face.

One plate was then used for a second stage of CVD diamond growth, prepared according to the method in WO01/96633, thereby producing a second layer with a thickness of over 4mm suitable for the preparation of a 4 x 4mm cutting plate to include the growth direction in the major surface. The layer is then characterized for dislocation density in the growth direction by methods of creating facets and using exposed plasma etchingAs a result, it was found that the dislocation density was very low at 10/mm²Within the region of (a). This makes the material particularly suitable for etalon applications.

Example 2

In optical applications, one key parameter is the uniformity and spread of property values such as birefringence and refractive index. These properties are affected by the strain field around the dislocation beam.

Two 001 synthetic diamond substrates for CVD diamond growth were prepared according to the method described in WO 01/96633. A layer was then grown on top of the diamond to a thickness of 4 mm. The dislocation direction of the layer was characterized and found to be within 15 ° of the growth direction on average. Two plates were cut out of these layers so that the major faces of the plates had dimensions > 4 x 4mm and the growth direction was in the plane of the major faces.

These layers are then used as substrates in a second growth process. The X-ray topography shows that the resulting growth (to a thickness of 3.5 mm) has a very low dislocation content, and the dislocations in the new overgrowth are perpendicular to those in the original CVD layer used as the substrate. After this second growth, the sample can be used in optical applications requiring very low scattering and birefringence.

Example 3

A synthetic diamond substrate for CVD diamond growth was prepared according to the method described in WO 01/96633. A layer was then grown on top of the diamond to a thickness of 7.4 mm. The conditions of the synthesis are such that the layer is doped with boron to a boron concentration measured in the solid of 7X 10¹⁶[ boron ]]Atom/cm³. The dislocation direction of the layer was characterized and the mean dislocation direction was found to be within 25 ° of the growth direction. Two plates are cut out of the laminate so that the main faces of the plates have a size > 4X 4mm, andthe growth direction is in the plane of the major face.

These plates have particular utility as substrates for electronic devices such as diamond metal semiconductor field effect transistors (MESFETs) due to low dislocation density in the major surface and boron doping.

Example 4

A piece of 6X 6mm synthetic substrate lb was prepared by the method described in WO 01/96633. Growth is then carried out on this substrate in stages, typically with about 3mm growth added in each stage. After each stage, the layer was retained in the polycrystalline diamond layer grown around it, the polycrystalline layer was trimmed by laser trimming to a disc of about 25mm diameter and then the disc was mounted in a recessed tungsten or other metal disc such that the point where the single crystal was exposed above the polycrystalline diamond layer was substantially horizontal (within 0.3 mm) to the upper surface of the tungsten disc.

Using the above technique, layers can be grown with final thicknesses in the range of 10-18mm, from which plates with 100 edges can be cut perpendicularly. The produced plate has a first <100> dimension in the plane of the plate of 10-16mm and a second orthogonal dimension of 3-8 mm.

These plates were then prepared as a substrate and used for a second stage of growth, again using the above techniques, to produce layers 10-18mm thick. From these layers, sheets can be cut perpendicularly with a <100> second dimension in the main face greater than 10-18mm and a first <100> dimension remaining in the range of 10-18 mm. For example, a plate having dimensions greater than 15mm by 12mm measured in orthogonal <100> directions is produced.

Claims (13)

1. A single crystal chemical vapour deposition diamond plate having a major surface which is a {001} face, opposite edges of the major surface being bounded by {100} side faces, each major surface having at least one linear dimension exceeding 10 mm.

2. A diamond plate according to claim 1, wherein at least one linear dimension exceeds 12 mm.

3. A diamond plate according to claim 2, wherein at least one linear dimension exceeds 15 mm.

4. A diamond plate according to claim 1, having first and second linear dimensions exceeding 10 mm.

5. A diamond plate according to claim 4, wherein the first and/or second linear dimension exceeds 12 mm.

6. A diamond plate according to claim 5, wherein the first and/or second linear dimension exceeds 15 mm.

7. A diamond plate according to any one of claims 1 to 6, which is a rectangular single crystal diamond plate bounded by {100} side faces, wherein the at least one linear dimension is an axial or lateral dimension.

8. A diamond plate according to claim 7, wherein the lateral dimension is a lateral edge dimension.

9. A diamond plate according to any one of claims 1 to 6, wherein the at least one linear dimension is a <100> edge formed by the intersection of a {100} side surface with a major surface.

10. A diamond plate according to any one of claims 4 to 6, wherein the first and second linear dimensions are orthogonal <100> edges formed by the intersection of the respective {100} side surfaces with the major surface.

11. A diamond plate according to any one of claims 1 to 6, having a rectangular shape.

12. A diamond plate according to any one of claims 1 to 6, having a square shape.

13. A diamond plate according to any one of claims 1 to 6, having the shape of a parallelogram.