Browse Prior Art Database

Subtractive Process for Improving FET Gate Oxide Formations

IP.com Disclosure Number: IPCOM000083384D
Original Publication Date: 1975-May-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Carballo, RA: AUTHOR [+2]

Abstract

Using a subtractive process for field-effect transistor (FET) gate oxide formations has at least five advantages: (1) the gate area is not exposed to post source-drain autodoping; (2) it eliminates the process steps for gate oxide and phospho silicate glass formation; (3) less etch undercutting results in precision gate dimensions; (4) the gate silicon/oxide interface is not exposed to photoresist and etching chemicals; and (5) gate leakage current is reduced.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 73% of the total text.

Page 1 of 2

Subtractive Process for Improving FET Gate Oxide Formations

Using a subtractive process for field-effect transistor (FET) gate oxide formations has at least five advantages: (1) the gate area is not exposed to post source-drain autodoping; (2) it eliminates the process steps for gate oxide and phospho silicate glass formation; (3) less etch undercutting results in precision gate dimensions; (4) the gate silicon/oxide interface is not exposed to photoresist and etching chemicals; and (5) gate leakage current is reduced.

This process features the simultaneous formation of phospho silicate glass for gate oxide over SiO(2), and source and drain in one diffusion step. Another process feature is the precision subtractive etch of the gate area. The process is performed in the following manner: 1. Initial oxidation of the body 4 produces SiO(2) layer 2.

2. A precision thickness gate oxide 10 is formed by a

controlled subtractive etch, as shown in Fig. 1.

3. The source and drain diffusion windows 3 and 5 are etched

in layer 2, as shown In Fig. 2.

4. A phosphorous diffusion produces source and drain regions 7

and 9, and also forms a surface layer 6 of phospho silicate

glass.

5. The source and drain regions 7 and 9 are thermally oxidized

forming a 100 angstrom layer 8 of SiO(2), as shown in

Fig. 3.

6. A blanket layer of Si(3)N(4), not shown, of a thickness of

approximately 1000 angstroms is formed by cold wall vapor

deposition.

7. The Si(3)N(4) layer is etched away everywhe...