Ge on insulator (GOI) is desired to obtain metal-oxide-semiconductor transistors with high performance and low leakage current. We have developed a method to make GOI based on liquid-phase epitaxial (LPE) growth on Si substrates and a defect necking technique in which defects are confined to a very short distance. Self-aligned microcrucibles were used to hold the Ge liquid. High-quality single-crystal (100) as well as (111) oriented GOI structures were obtained with a process compatible with Si-based fabrication. No dislocations or stacking faults were found in the LPE Ge films on insulator. The orientation of the Ge crystals was controlled by the seeding Si substrate. This method opens up the possibility of integrating Ge device structures in a baseline Si integrated circuit process.
The monolithic integration of germanium-on-insulator (GeOI) p-MOSFETs with silicon n-MOSFETs on a silicon substrate is demonstrated. The GeOI p-MOSFETs are fabricated on the oxide for silicon device isolation based on the newly developed rapid-melt-growth method. CMOS inverters consisting of the silicon n-MOSFET and GeOI p-MOSFET were obtained, and the measured results show that the processing of high-performance GeOI devices is compatible with bulk-silicon technology.
A rapid melt growth method was developed to produce Ge crystals including Ge pillars, nanowires, and Ge-on-insulator. Amorphous Ge was deposited and patterned, then crystallized by melting and solidifying using Si substrates for seeding. Self-aligned SiO 2 microcrucibles were used to contain the Ge liquid during the crystallization anneal. The misfit defects were terminated within small regions around the seeding windows by a necking mechanism. Crystallization calculations showed that very high epitaxial growth velocity can be achieved when the temperature of Ge liquid is lower than but close to its melting point, while the random unseeded nucleation rate is very low in the same temperature range. High-quality Ge nanowires and Ge-on-insulator structures are produced with a simple and robust process. The rapid melt growth technique works very well with a variety of film thickness, including that of nanometer ultrathin structures. The surface smoothness obtained by Ge deposition is retained during crystallization and the film thickness is also controlled by deposition.
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