Etch of silicon nitride selective to silicon and silicon...

Details Etch of silicon nitride selective to silicon and silicon... Etch of silicon nitride selective to silicon and silicon...

2001-05-11

2004-04-06

Norton, Nadine G. (Department: 1765)

Semiconductor device manufacturing: process

Chemical etching

Vapor phase etching

C438S710000, C438S714000, C438S723000, C438S724000, C438S744000

Reexamination Certificate

active

06716759

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the field of semiconductor manufacture and, more particularly, to an etch useful for removing silicon nitride selective to silicon and silicon dioxide.
BACKGROUND OF THE INVENTION
During the manufacture of semiconductor devices such as a memory devices, logic devices, and microprocessors, various processes are commonly performed. Etching silicon nitride selective to silicon (such as polysilicon) and to silicon dioxide with various etch ratios is often required. For example, hot phosphoric acid isotropically etches silicon nitride selective to silicon dioxide and silicon. Other processes for etching Si
3
N
4
selective to SiO
2
and Si are discussed in “
Highly Selective Etching of Silicon Nitride Over Silicon and Silicon Dioxide,” J. Vac. Sci. Technol
. A 17(6), November/December 1999, which describes the use of oxygen (O
2
) and nitrogen (N
2
) in combination with CF
4
or NF
3
. The processes discussed achieve Si
3
N
4
to Si and to SiO
2
etch rate ratios of up to 100 and 70 respectively using nitrogen trifluoride. The processes uses high flow rates of 800 standard cubic centimeters (sccm) O
2
and 110 sccm N
2
for most experiments. Further, using carbon tetrafluoride, a Si
3
N
4
to polysilicon etch ratio of 40 was achieved while SiO
2
was not etched at all. Etch rates of silicon nitride are below about 50 angstroms (Å) per minute.
As semiconductor manufacture typically requires high volume processing to lower costs, any decrease in temporal processing requirements can result in a large increase in product throughput. Further, having options available to accomplish a task such as etching silicon nitride is advantageous, as one process may function better for certain manufacturing flows. Additional methods for etching silicon nitride selective to silicon and silicon nitride at an accelerated rate would be desirable.
SUMMARY OF THE INVENTION
The present invention provides a new etch method that, among other advantages, reduces problems associated with the manufacture of semiconductor devices, particularly problems in etching silicon nitride selective to silicon and silicon dioxide. In accordance with one embodiment of the invention a semiconductor wafer substrate assembly having a layer of silicon nitride and a layer of at least one of silicon and silicon dioxide is placed into an etch chamber. Oxygen and either CHF
3
or CH
2
F
2
are introduced into an etch chamber under controlled flow rates, power, and pressure. At the parameters detailed herein, the etch removes silicon nitride selective to silicon dioxide and silicon.
Additional advantages will become apparent to those skilled in the art from the following detailed description read in conjunction with the appended claims and the drawings attached hereto.


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patent: 0 945 896 (1999-09-01), None
“Highly Selective Etching of Silicon Nitride Over Silicon and Silicon Dioxide,” J. Vac. Sci. Technol. A 17(6), Nov./Dec. 1999.

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