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CF4 RIE Pre-Etch During Etchback of Sidewall Formation

IP.com Disclosure Number: IPCOM000060961D
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Markle, AJ: AUTHOR [+2]

Abstract

In the manufacture of semiconductor devices sidewall uniformity is desirable. During the RIE (reactive ion etch) step, polymer formation can produce non-uniformities. This article suggests the use of a RIE pre-etch to improve etchback uniformity. In sidewall formation processing, a RIE etchback in CHF3/Ar takes place with etch uniformity varying as much as 13%. Even though CHF3/Ar is valued for a high etch ratio of oxide to nitride during RIE, a prolonged etch is undesirable. This is because the prolonged etch may produce non-uniformities within a wafer and within a wafer batch. Sidewall uniformity is essential to control and to insure reproducibility of electrical parameters BVebo and BVces . There is also a lengthening of turnaround time since the tool must be cleaned of polymer formed when processing each run in CHF3/Ar.

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CF4 RIE Pre-Etch During Etchback of Sidewall Formation

In the manufacture of semiconductor devices sidewall uniformity is desirable. During the RIE (reactive ion etch) step, polymer formation can produce non- uniformities. This article suggests the use of a RIE pre-etch to improve etchback uniformity. In sidewall formation processing, a RIE etchback in CHF3/Ar takes place with etch uniformity varying as much as 13%. Even though CHF3/Ar is valued for a high etch ratio of oxide to nitride during RIE, a prolonged etch is undesirable. This is because the prolonged etch may produce non-uniformities within a wafer and within a wafer batch. Sidewall uniformity is essential to control and to insure reproducibility of electrical parameters BVebo and BVces . There is also a lengthening of turnaround time since the tool must be cleaned of polymer formed when processing each run in CHF3/Ar. This invention takes advantage of the etch uniformity of the oxide in CF4 RIE, which is 6% compared to 13% in CHF3/Ar RIE in an oxide environment and 30% in a nitride environment. The CF4 is used to pre- etch ~2/3 of the CVD (chemical vapor deposition) oxide film and the remaining oxide is etched in the CHF3/Ar as before so that the etch selective to the Si is maintained. Fig. 1 shows the device before etchback and Fig. 2 as it appears after etchback, and as seen with a scanning electron microscope (SEM). The layers are identifiable as follows: layer for SEM delineation 1, SiO2 layer 2, S...