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Self Aligned ROI To SAM Structure

IP.com Disclosure Number: IPCOM000048774D
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 74K

Publishing Venue

IBM

Related People

Magdo, IE: AUTHOR [+2]

Abstract

A simple method of producing a self-aligned recessed oxide isolation (ROI) to self-aligned metal (SAM) structure is described. The structure has no "bird's beak" or "bird's head", and requires one additional Si(3)N(4) deposition and one reactive ion etching (RIE) step. The use of high pressure oxidation or plasma oxidation is necessary. The process will be described to one particular structure, but it is obvious that it can also be used for I/2/L, Schottky barrier diodes, resistors, etc.

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Self Aligned ROI To SAM Structure

A simple method of producing a self-aligned recessed oxide isolation (ROI) to self-aligned metal (SAM) structure is described. The structure has no "bird's beak" or "bird's head", and requires one additional Si(3)N(4) deposition and one reactive ion etching (RIE) step. The use of high pressure oxidation or plasma oxidation is necessary. The process will be described to one particular structure, but it is obvious that it can also be used for I/2/L, Schottky barrier diodes, resistors, etc.

A bipolar device fabrication would proceed as follows:
1. Start with p- wafer 10, followed by subcollector 11 and

isolation 12 diffusions. Grow epitaxial layer 13, and

perform reach-through diffusion or implant 14.
2. After oxidation, use an oversized base mask and diffuse or

ion-implant base 15. Deposit a thin layer of Si(3)N(4).

Use the SAM, all contact mask 16, and open the emitter-base

area and collector contact as shown in Fig. 1. The mask 16

includes an SiO(2) layer and an Si(3)N(4) layer thereover.

Grow about 400 angstrom SiO(2) layer 18.
3. Next, a layer 19 polysilicon of about 1.1 Mum thick is

deposited, followed by the deposition of a layer 20 of

Si(3)N(4). Photolithography and etching

etching techniques are used to form openings in layer 20

down to polysilicon layer 19 in the

desired pattern of ROI. The structure is put in an RIE

environment and the ROI pattern is etched through

the polysilicon layer 19, Si(3)N(4) and SiO(2), mask

16 and the singlecyrstal silicon epitaxial

layer 13 to a depth of about 3800 A, if a 1

Mum silicon dioxide is subsequently desired. If

thicker silicon dioxide isolation is required, the etched

trench 22 is made deeper. A cross-sectional view of the

resulting structure is shown in Fig. 2.
4. Next, a thin layer of thermal silicon dioxide

(200-500 Angstrom) isgrown and a lyaer 25 of

of Si(3)N(4) is deposited. A directional RIE

of the Si(3)N(4) layer 25 is performed to form Si(3)N(4)

vertical sidewalls 25, as shown in Fig. 3.
5. The Si(3)N(4) layer 25 thickness is typically about

2000 Angstr...