Use of moire fringe patterns to map relaxation in SiGe on insulator structures fabricated on SIMOX substrates
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Strain Engineering has become extremely important in the semiconductor industry as a means of achieving device performance enhancement as device scaling runs out of steam. It is important to detect strain as a function of position in device sized areas in order to assess the viability of different process schemes. In the present work, Moire fringe patterns were used to measure and map the relaxation effects in SiGe and Si/SiGe structures fabricated on SIMOX substrates. Initially, measurements of the strain state using the Moire technique were correlated with those obtained by x-ray diffraction for blanket SiGe on insulator films over the range 0.2–0.8%. Using this correlation as a basis, several interesting relaxation characteristics were found on patterned structures. Evidence of a rhombohedral relaxation was seen for rectangular SiGe mesas fabricated by patterning and then homogenizing SiGe/Si bilayers on SIMOX substrates. The magnitude of the relaxation was found to depend of the size of the structure and the distance to the nearest edge. Elastic relaxation of Si lines was also seen. Lastly, evidence of non uniform relaxation was seen in the SiGe template in wide channel areas of silicide-contacted device structures.
KeywordsSiGe Layer Moire Fringe Elastic Relaxation Moire Pattern Gate Polysilicon
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