Improvement of alignment tolerance against contact hole etching by growing of underlying silicon-selective epitaxial layer
We demonstrated that the influences of a contact hole overlapping a local oxidation of silicon (LOCOS) isolation can be reduced by using selective epitaxial growth, which is improved the alignment margin of the contact hole in the LOCOS region. The experimental results indicated that the epitaxial layer underlying the contact bottoms prevented the TiSi2 layer from penetrating into the Si substrate. Therefore, the leakage current at the overlapping region was drastically suppressed for a configuration where the contact hole and the LOCOS region overlapped. The breakdown voltage was improved compared with a case without an epitaxial layer.
contact isolation selective epitaxial growth alignment margin ulsi