Silicon power device material problems

The limitations imposed on the performance of large-area p-n junction devices by the size and quality of the silicon material are reviewed. It is shown that material quality problems--such as nouniform resistivity, foreign particulate matter, microdefects, dissolved oxygen, and various crystallographic defects--represent real limitations on device performance and yields; however, the effects of process-induced defects--such as diffusion- or stress-induced dislocations, diffusant precipitation, heavy metal precipitation, and interface degradation--often obscure, or even overwhelm, the effects of the grown-in defects. The importance of the interaction of process-induced defects with grown-in defects, and particularly the interaction of heavy metals with defects, foreign particulate matter and dissolved oxygen, has been emphasized by the results of recent investigations. The need for defect-free processing techniques in obtaining information on the effects of grown-in defects is discussed. Representative studies of the effects of defects on device performance are listed. New techniques for studying defects are reviewed with reference to results of interest to silicon device technology. Some growth techniques which may be helpful in eliminating certain material quality problems are discussed briefly.