Browse Prior Art Database

Method for Reducing the Diffusion Contact Borders

IP.com Disclosure Number: IPCOM000036202D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Stanasolovich, D: AUTHOR [+2]

Abstract

Conventional process technologies require that a border be placed around all diffusion contacts to prevent shorting between polysilicon and interconnecting metallurgy. The use of borders around the diffusion contacts consumes a great deal of chip area and prevents further increases in circuit density. This problem with the existing process technology is shown in Fig. 1.

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Method for Reducing the Diffusion Contact Borders

Conventional process technologies require that a border be placed around all diffusion contacts to prevent shorting between polysilicon and interconnecting metallurgy. The use of borders around the diffusion contacts consumes a great deal of chip area and prevents further increases in circuit density. This problem with the existing process technology is shown in Fig. 1.

This article describes a process which allows the use of Borderless Diffusion Contacts.

(Image Omitted)

First, polysilicon is oxidized to form a 230 angstrom oxide cap on the polysilicon. The polysilicon is then implanted which lowers sheet resistance. A silicon nitride cap is deposited approximately 1000 angstroms in thickness, and annealed to reduce stress. A layer of resist is applied, exposed, and developed to define the gate electrodes and polysilicon interconnects. The sidewalls are then oxidized to form the sidewall spacers (used for implantation of the diffusion regions).

Silicon nitride spacers (about 1000 angstroms in width) are formed on the sidewalls of polysilicon/oxide. An etch process with a very high nitride to oxide etch rate ratio is used. The diffusions regions (N+ and P+) are implanted. The implant conditions, nitride spacer width, and sidewall oxide thickness are optimized to produce the de sired electrical characteristics (Fig. 2). The BPSG (passivation oxide) is deposited and reflowed to produce a smooth surface. The contacts...