Patent ID: 11873224
Assignee: ELEMENT SIX TECHNOLOGIES LIMITED
Field: Surface technology, coating (Chemistry)
Classification: CPC C | IPC C

Claim 0:
1. A method of fabricating a polycrystalline CVD synthetic diamond wafer, the method comprising:
loading a refractory metal substrate into a CVD reactor;
introducing microwaves into the CVD reactor at a known power density in terms of power per unit area of the refractory metal substrate;
introducing process gas into the CVD reactor, wherein the process gas within the CVD reactor comprises nitrogen, a carbon containing gas, and hydrogen;
controlling an average temperature of the refractory metal substrate to lie in a range 750° C. to 950° C. and to maintain a temperature difference between an edge and a centre point on the refractory metal substrate of no more than 80° C.;
growing a polycrystalline CVD synthetic diamond wafer to a thickness of at least 2.5 mm on the refractory metal substrate;
during the growing stage, increasing the pressure of the process gas and reducing the average power per unit area of the refractory metal substrate; and
subsequently cooling the polycrystalline CVD synthetic diamond wafer to yield a polycrystalline CVD synthetic diamond wafer having a thickness of at least 2.5 mm, an average thermal conductivity at room temperature through the thickness of the polycrystalline CVD synthetic diamond wafer of between 1700 and 2400 Wm−1K−1 over at least a central area of the polycrystalline CVD synthetic diamond wafer, wherein the central area is at least 70% of a total area of the polycrystalline CVD synthetic diamond wafer, and wherein the polycrystalline CVD synthetic diamond wafer 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 wafer and extend greater than 2 mm in length.