Planarized trench and field oxide and poly isolation scheme
US5385861A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 15, 1994 |
| Grant date | Jan 31, 1995 |
| Priority date | — |
| Expiry date | Mar 15, 2014 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S148/05
- WIPO fieldSemiconductors
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.