Planarized trench and field oxide and poly isolation scheme

Details Planarized trench and field oxide and poly isolation scheme Planarized trench and field oxide and poly isolation scheme

1994-03-15

1995-01-31

Hearn, Brian E.

Fishing, trapping, and vermin destroying

437974, 437 64, 437924, 437984, 148DIG50, H01L 2176

Patent

active

053858611

ABSTRACT:
A novel device isolation scheme for separating active regions on a semiconductor substrate by combining field oxide formation with trench isolation is disclosed. According to this scheme, shallow and deep trenches are etched into the semiconductor substrate. A layer of nitride is deposited over the entire substrate followed by a layer of poly-silicon. Oxide spacers on the poly-silicon and a photoresist mask is aligned within the oxide spacers, thereby permitting the selective etching of the poly-silicon layer. The poly-silicon layer overlying the active regions of the semiconductor substrate are etched away. Then an oxidation step is performed such that the poly-silicon layer filling the shallow trenches is oxidized while the poly-silicon filling the deep trenches remains unoxidized. The alignment of the photoresist becomes highly non-critical because of the use of the oxide spacers and fully walled junctions are provided.

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