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Silicon Nitride Sidewall Recessed Oxide Isolation

IP.com Disclosure Number: IPCOM000048594D
Original Publication Date: 1982-Feb-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Magdo, IE: AUTHOR [+2]

Abstract

The recessed oxide isolation (ROI) process is the most common form of dielectric isolation at the present time. It is well known that the process forms a "bird's beak" and "bird's head" structure on the periphery of the SiO(2)/Si(3)N(4) masking layer. The "bird's beak" limits the density and the "bird's head" the planarity of the structure. Additionally , emitters cannot abut the ROI at least in part because of the "bird's beak" formation.

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Silicon Nitride Sidewall Recessed Oxide Isolation

The recessed oxide isolation (ROI) process is the most common form of dielectric isolation at the present time. It is well known that the process forms a "bird's beak" and "bird's head" structure on the periphery of the SiO(2)/Si(3)N(4) masking layer. The "bird's beak" limits the density and the "bird's head" the planarity of the structure. Additionally , emitters cannot abut the ROI at least in part because of the "bird's beak" formation.

The herein described method eliminates the "bird's beak" and the "bird's head", and thereby enables emitters to abut the ROI.

The process uses a silicon wafer 10 which is then,thermally oxidized to form a silicon dioxide (SiO(2)) 11 of about 200-1000 A in thickness. Silicon nitride (Si(3)N(4)) layer of 1000-2000 A in thickness is deposited thereover. Photolithography and etching techniques are used to form a pattern of openings in layers 11, 12 where the ROI structure is desired.

The dielectric layers 11 and 12 are used as a mask to etch silicon 10 in a very directional manner to produce a trench pattern 13 having substantially vertical sidewalls, as shown in Fig. 1.

The wafer is reoxidized to form a layer 14 of about 500-1000 (Angstrom) in thickness. Next, a layer 15 of Si(3)N(4) of about 1000-4000 A in thickness is deposited, as seen in Fig. 2. The Si(3)N(4) layer 15 is directionally etched by reactive ion etching (RIE) in a suitable ambient that substantially removes the hori...