Method of preventing asymmetric etching of lines in sub-micrometer range sidewall images transfer
US4648937A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 30, 1985 |
| Grant date | Mar 10, 1987 |
| Priority date | — |
| Expiry date | Oct 30, 2005 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S438/951
- WIPO fieldSemiconductors
- WIPO sectorElectrical engineering
Abstract
In the process of sidewall image transfer, a vertical step is etched in some material and then a conformal layer of some other material is deposited over the step. By reactive ion etching the conformal material can be anisotropically etched which results in a sidewall spacer of the second material on the vertical surfaces of the step material. By removing the step material, the free standing spacer can then be used as a mask. One area in which improvement is desired is in the selectivity of the etch of the spacer to the material immediately below it. Because of the limited number of materials and reactive ion etching gases it is difficult to avoid an etch in the underlying layer as the sidewall spacer is formed. A suitable etch stop is employed beneath the step material to avoid the problem. Because of the usual technology, the spacer material is plasma deposited silicon nitride and the step material is photoresist. Polysilicon, aluminum or similar metal is employed as an etch stop, since it is not by a CF.sub.4 based gas which is used to form the spacer.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.