Element Six Technologies Limited

Gruffudd Trefor Williams

Joseph Michael Dodson

Richard Stuart Balmer

Paul Nicolas Inglis

Christopher John Kelly

A method of fabricating a polycrystalline CVD synthetic diamond wafer is disclosed. A first polycrystalline CVD synthetic diamond wafer is grown using a CVD process to a first thickness on a substrate. A second smaller wafer is cut from the polycrystalline CVD synthetic diamond wafer. The second smaller wafer is located on a carrier, and further polycrystalline CVD synthetic diamond material is grown on the second smaller wafer to a second thickness to give a polycrystalline CVD synthetic diamond material having a total thickness of the combined first and second thicknesses.

Polycrystalline synthetic diamond material

A polycrystalline CVD synthetic diamond material is provided that has an average thermal conductivity at room temperature through a thickness of the polycrystalline CVD synthetic diamond material of between 1700 and 2400 WmK, a thickness of at least 2.5 mm and a visible transmittance through the thickness of the polycrystalline CVD synthetic diamond of at least 25%. A wafer comprising the material is also provided, wherein at least 70% of a total area of the wafer has the properties of the polycrystalline CVD synthetic diamond material. A method for fabricating the wafer is also disclosed.

Polycrystalline chemical vapour deposition synthetic diamond material

A method of fabricating a polycrystalline CVD synthetic diamond material having an average thermal conductivity at room temperature through a thickness of the polycrystalline CVD synthetic diamond material of at least 2000 WmK, the method comprising: loading a refractory metal substrate into a CVD reactor; locating a refractory metal guard ring around a peripheral region of the refractory metal substrate, the refractory metal guard ring defining a gap between an edge of the refractory metal substrate and the refractory metal guard ring having a width 1.5 mm to 5.0 mm; introducing microwaves into the CVD reactor at a power such that the power density in terms of power per unit area of the refractory metal substrate is in a range 2.5 to 4.5 W mm; introducing process gas into the CVD reactor wherein the process gas within the CVD reactor comprises a nitrogen concentration in a range 600 ppb to 1500 ppb calculated as molecular nitrogen N2, a carbon containing gas concentration in a range 0.5% to 3.0% by volume, and a hydrogen concentration in a range 92% to 98.5% by volume; controlling an average temperature of the refractory metal substrate to lie in a range 750&#xb0; C. to 950&#xb0; C. and to maintain a temperature difference between an edge and a centre point on the refractory metal substrate of no more than 80&#xb0; C. growing polycrystalline CVD synthetic diamond material to a thickness of at least 1.3 mm on the refractory metal substrate; and cooling the polycrystalline CVD synthetic diamond material to yield a polycrystalline CVD synthetic diamond material having a thickness of at least 1.3 mm, an average thermal conductivity at room temperature through the thickness of the polycrystalline CVD synthetic diamond material of at least 2000 WmKover at least a central area of the polycrystalline CVD synthetic diamond material, wherein the central area is at least 70% of a total area of the polycrystalline CVD synthetic diamond material, a single substitutional nitrogen concentration no more than 0.80 ppm over at least the central area of the polycrystalline CVD synthetic diamond material, and wherein the polycrystalline CVD synthetic diamond material is substantially crack free over at least the central area thereof such that the central area has no cracks which intersect both external major faces of the polycrystalline CVD synthetic diamond material and extend greater than 2 mm in length.

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Oxfordshire, United Kingdom

Gruffudd Trefor Williams