Method of generating multiple oxide thicknesses by one oxidation step using NH3 nitridation followed by re-oxidation
US6225167A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 13, 2000 |
| Grant date | May 1, 2001 |
| Priority date | — |
| Expiry date | Mar 13, 2020 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S438/911
- WIPO fieldSemiconductors
- WIPO sectorElectrical engineering
Abstract
A method is disclosed to form a plurality of oxides of different thicknesses with one step oxidation. In a first embodiment, a substrate is provided having a high-voltage cell area and a peripheral low-voltage logic area separated by a trench isolation region. The substrate is first nitrided. Then the nitride layer over the high-voltage area is removed, and the substrate is wet cleaned with HF solution. The substrate surface is next oxidized to form a tunnel oxide of desired thickness over the high-voltage. In a second embodiment, a sacrificial oxide is used over the substrate for patterning the high voltage cell area and the low-voltage logic area. The sacrificial oxide is removed from the low-voltage area and the substrate is nitrided after cleaning with a solution not containing HF, thus forming a nitride layer over the low-voltage area. Then, the sacrificial oxide is removed from the high-voltage area with an HF dip, and tunnel oxide of desired thickness is formed over the same area. In this manner, oxides of multiple thicknesses are provided for the high-voltage cell area and the low-voltage peripheral logic area with one oxidation step. At the same time, with a judicious use …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.