Fabrication of 50%-50% Germanium Silicon Layers by Ion Implantation

With the increasing need for devices such as optoelectronics, which require different materials properties than silicon, new compatible materials and fabrication processes must be developed. A germanium silicon layer embedded in a silicon wafer provides new materials properties while keeping the silicon substrate. Molecular Beam Epitaxy has been used to make prototypes, but a manufacturing technique compatible with production lines is still to be found. Ion implantation to alloy thin germanium silicon layers in masked patterns would seem to be an ideal solution, but residual implantation defects have so far prevented the manufacturing of such devices with satisfactory electrical properties . The goal is to obtain a 0.20eV bandgap decrease for optoelectronics applications, and this is obtained with an unstrained layer of 50 at% germanium. Such a high implant concentration can normally not be achieved because of sputtering limits and severe surface erosion. These problems can be solved by a recently developed novel "zero" sputtering technique combined with high temperature implantation. GeSi layers can be manufactured by conventional process equipment that are 0.5 micrometers thick and should exhibit acceptably low defect densities. The need for semiconductor materials with different properties then silicon but are still compatible with conventional processing lines will keep on increasing for optoelectronics, high speed devices or other applications. Patterned silicon germanium layers imbedded in silicon wafers provide such advantages. Developing a satisfactory manufacturing process based on ion implantation would allow the design and production of many such devices.