Patterned SOI by formation and annihilation of buried oxide regions during processing

#The present invention relates to silicon-on-insulator (SOI) substrates for semiconductor integrated circuits (ICs), and more particularly to a method of fabricating an SOI substrate which includes an ultra-thin top Si-containing layer (on the order of about 2000 Å or less) and at least one patterned buried semi-insulating or insulating region such as a buried oxide (BOX) region which has well defined edges that are suitable for sub-micron geometries.

#Separation by implantation of oxygen (SIMOX) is a technique employed in the semiconductor industry in fabricating SOI substrates that can be used in the manufacturing of ICs. SIMOX typically involves using high-energy ions to implant a large dose of oxygen ions beneath the surface of a bulk Si-containing wafer. Upon high-temperature annealing, the implanted oxygen ions form a continuous BOX region which electrically isolates the Si at the surface (i.e., top or-superfacial Si layer). Typically, prior art SIMOX processes have been used to fabricate SOIs with a top Si layer and a BOX thickness of several thousand angstroms.

#In some applications, it is desirable to form discrete and isolated BOX regions within a Si-containing substrate while not forming BOX regions in other portions of the same Si-containing substrate. Hence, there is a growing need for providing patterned SOI regions. Patterned SOI regions formed within a Si-containing substrate are especially needed for future high performance Si-containing ICs, optical communication devices and three-dimensional device and circuit integration.

#FIGS. 1A-1F are pictorial representations (through cross-sectional views) showing the various processing steps employed in one embodiment of the present invention which is used in forming an SOI substrate having at least one patterned buried semi-insulating or insulating region that has well defined edges associated therewith.

#FIGS. 2A-2F are pictorial representations (through cross-sectional views) showing the various processing steps employed in another embodiment of the present invention which is used in forming an SOI substrate having at least one patterned buried semi-insulating or insulating region that has well defined edges associated therewith.

#The present invention, which provides a method of fabricating an SOI substrate having an ultra-thin top Si-containing layer and at least one patterned buried semi-insulating or insulating region, will now be described in greater detail by referring to the drawings that accompany the present application.

#Reference is first made to FIGS. 1A-1F which show the various processing steps that are employed in one embodiment of the present invention wherein an SOI substrate having an ultra-thin top Si-containing layer and at least one patterned buried semi-insulating or insulating region that has well defined edges is fabricated. Specifically, FIG. 1A illustrates the first processing step of the present invention wherein first ions 12 are implanted into a surface of Si-containing substrate 10 under conditions wherein an implant region of first ions (labeled as 14) is formed within the Si-containing substrate. The first ions may be implanted using a continuous or pulse ion implantation process wherein various doses of first ions 12 can be employed.

#The term “Si-containing substrate” as used herein denotes any Si-containing material including, but not limited to: Si, SiGe, SiC, SiCGe, nitrogen doped Si, Si/Si and Si/SiGe. A preferred Si-containing substrate employed in the present invention is a Si wafer. The Si-containing substrate may be undoped or doped (n or p-type) depending on the future use of the SOI wafer.