Patent ID: 8859058

Claim:
A method of manufacturing synthetic diamond material via chemical vapour deposition, the method comprising: providing a microwave plasma reactor comprising: a microwave generator configured to generate microwaves at a frequency f; a plasma chamber comprising a base, a top plate, and a side wall extending from said base to said top plate defining a resonance cavity for supporting a microwave resonance mode between the base and the top plate; a microwave coupling configuration for feeding microwaves from the microwave generator into the plasma chamber; a gas flow system for feeding process gases into the plasma chamber and removing them therefrom; and a substrate holder disposed in the plasma chamber and comprising a supporting surface for supporting a substrate; locating a substrate over the supporting surface of the substrate holder, the substrate having a growth surface on which the synthetic diamond material is to be deposited, feeding process gases into the plasma chamber; and feeding microwaves into the plasma chamber to form a plasma over the growth surface of the substrate and grow synthetic diamond material on the growth surface of the substrate, wherein the substrate dimensions and location within the resonance cavity are selected to generate a localized axisymmetric E z electric field profile across the growth surface in use, the localized axisymmetric E z electric field profile comprising a substantially flat central portion bound by a ring of higher electric field, the substantially flat central portion extending over at least 60% of an area of the growth surface of the substrate and having an E z electric field variation of no more than ±10% of a central E z electric field strength, the ring of higher electric field being disposed around the central portion and having a peak E z electric field strength in a range 10% to 50% higher than the central E z electric field strength.