LARGER AREA SINGLE CRYSTAL DIAMOND SUBSTRATE FORMATION WITH A MOSAIC TILING PROCESS

Diamond is a material known for its extraordinary optical, mechanical, thermal, and electricalproperties. The ultra-low carrier density in intrinsic diamond makes it an extreme insulator, but it can be doped to achieve relatively high electrical conductivity. A wide band gap, high carrier saturation velocity, high dielectric strength, as well as the highest thermal conductivity of all materials, translate to figures of merit several orders of magnitude greater than silicon, making diamond stand out as the ultimate material for a new generation of electronic devices. The technology developed so far has not been able to take full advantage of this extreme potential because unlike Silicon, a straightforward method for producing large wafers of high-quality single crystal diamond has not yet been perfected. This investigation explores the production of large area diamond substrates based on Microwave Plasma-Assisted Chemical Vapor Deposition to grow a continuous layer of single crystal diamond across an array of individual diamond plates in a process known as the mosaic technique. The project addressed a set of challenges related to this mosaic tiling technique, including developing high precision lattice orientation measurements; establishing the process of modifying individual orientations by laser cutting and polishing adjustments; developing a new tile assembly structure and fabrication process; and establishing the growth conditions necessary for uniform single layer diamond homoepitaxy as an extension on previous work optimizing crystal quality and area enlargement by enhanced lateral growth. Several analysis techniques were developed as part of the investigation, such as RegionalEtch Pit Density Analysis and two independent relative misorientation measurements based on X-Ray Topography and X-Ray Rocking Curve scans. Definitions for characterizing the observations have been settled, coining new terms and concepts such as three types of relative misorientation: Tilt, Torsion and Twist, and new metrics such as Aggregate Mosaicity and a formal definition of what constitutes a Mosaic Boundary. The necessary conditions to evaluate when mosaic boundaries are indistinguishable from single crystal regions have been determined. New software was developed in MATLAB to analyze these new types of measurement metrics and measurement methods. Thick samples were grown and produced with a total grown diamond thickness up to 4mm. The grown diamond of the mosaic plate was characterized at different thicknesses and how the mosaic boundary spread and position behaved and could be controlled throughout the process was studied. A clear set of substrate preparation and growth parameters were identified and listed as necessary conditions for successful mosaic growth serving as a roadmap leading to large area single crystal diamond substrates. A process for the plate lift-off of diamond substrates via an ion implantation process followed by diamond growth and then electrochemical separation was investigated. Deposition parameters were refined to overcome known difficulties related to shallow implantations from low energy ion implantation of commercial providers. This lift-off process is a necessary final step in large area diamond plate fabrication, as the procedure is the only known reasonable way to produce large area plates with minimal material loss. Successful plate lift-off from low energy implantations performed by easily accessible commercial providers was demonstrated and this process will facilitate diamond plate production at industrial scales. Progress established throughout this study resulted in plates composed of 4 tiles grown up to 10mm x 10mm using this mosaic tiling technique.