System and method for substrate wafer back side and edge cross section seals
View Patent ↗Systems and methods for substrate wafer back side and edge cross section seals. In accordance with a first method embodiment, a silicon wafer of a first conductivity type is accessed. An epitaxial layer of the first conductivity type is grown on a front surface of the silicon wafer. The epitaxial layer is implanted to form a region of an opposite conductivity type. The growing and implanting are repeated to form a vertical column of the opposite conductivity type. The wafer may also be implanted to form a region of the opposite conductivity type vertically aligned with the vertical column.
1. A method of growing epitaxial silicon on a silicon wafer, said method comprising:
depositing a layer of silicon oxide on all entire surfaces and edges of said silicon wafer;
removing said silicon oxide from a front surface of said silicon wafer;
depositing a layer of poly silicon only on a back surface of said silicon wafer, over said silicon oxide;
growing a layer of epitaxial silicon on said front surface of said silicon wafer;
depositing another layer of silicon oxide on all exposed surfaces and edges of said layer of epitaxial silicon and said silicon wafer;
removing said another layer of silicon oxide from a front surface of said layer of epitaxial silicon;
depositing another layer of poly silicon on the back surface of said silicon wafer, over said another layer of silicon oxide; and
growing another layer of epitaxial silicon on said layer of epitaxial silicon.
2. The method of claim 1 wherein said depositing a layer of silicon oxide is configured to reduce auto doping during said growing.
3. The method of claim 1 further comprising doping a region of said layer of epitaxial silicon prior to said growing another layer of epitaxial silicon.
4. The method of claim 1 wherein said another layer of epitaxial silicon comprises a gap characterized by an absence of epitaxial silicon.
5. The method of claim 1 wherein no epitaxial silicon is in contact with silicon of a back side of said wafer.