Growth strategies for large and high quality single crystal diamond substrates

Abstract

The high pressure (130–240Torr) and high power density microwave plasma assisted chemical vapor deposition (MPACVD) of single crystal diamond (SCD) substrates is investigated. Locally controlled growth strategies that enable the synthesis of large (~5mm) and thick (200μm–1.3mm) CVD free standing SCD substrates are presented. Two process control methods, i.e. control of the input power level versus time, and the precise control of the substrate holder geometry when combined play an important role in obtaining high quality free standing single crystal diamond (SCD) substrates. The performance of one distinct substrate holder design, the “pocket holder”, is presented in detail and is compared to the performance of the more commonly used open holder. A comparison of these two holder designs operating in the high pressure SCD synthesis process environment reveals the advantages of the pocket holder. The pocket holder design not only aids in the growth of thick SCD substrates when operating within the reactor's safe and efficient operating regime, but also enhances their in situ lateral growth. Processes are described which enhance the growth of the SCD surface area while simultaneously reducing the growth of the polycrystalline diamond rim that typically surrounds the synthesized SCD. Using such methods at 240Torr MPACVD SCD plates and SCD cubes are synthesized at high growth rates.