MPACVD growth of single crystalline diamond substrates with PCD rimless and expanding surfaces

摘要

Single crystal diamond (SCD) growth was performed in optimized pocket substrate holders at a high pressure (240Torr) and a high power density (～1000W/cm~3). In an effort to overcome the challenges of growing large area SCD substrates without a corresponding polycrystalline diamond (PCD) rim, a growth recipe using these pocket holders was developed. This growth recipe controls the substrate temperature (T_s) and the incident microwave power (P_(inc)) in a prescribed function of growth time. Through this process, the feasibility to enlarge the SCD substrate in situ, i.e., during the growth itself is shown. By allowing the temperature to increase from ～980℃ to 1040 ℃, then reducing the temperature, and then allowing it to drift up again, the deposition process alternates between the fast growth of the different crystal directions (i.e., <110>, <111>, and <100>) and a slow growth to smoothen the top surface. This leads to an increased lateral SCD growth. The slow growth of the crystal faces in turn leads to a smooth and enlarged top surface. Certain strategies such as the termination of the growth process at the appropriate time are critical in obtaining flat and smooth SCD surfaces without the formation of any PCD rim. The SCD substrates grown via this method have been analyzed by optical and scanning electron microscopies. The lateral SCD surface area increased between 1.7 and 2 times greater than the initial seed surface area during one continuous run. The deposited SCDs have high growth rates of ～30 μm/h resulting in smooth, flat and rimless substrates, hence indicating the improvement in the quality and morphology of the deposited substrates.