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MOS Gate Construction Method

IP.com Disclosure Number: IPCOM000062090D
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 66K

Publishing Venue

IBM

Related People

Davari, B: AUTHOR

Abstract

This article relates generally to integrated circuit fabrication and, more particularly, to a technique for forming control gates of metal oxide semiconductors with greater reliability. By depositing and patterning gate material after the source and drain are formed, potential problems, such as channeling of the source/drain implant through the gate material, subjecting the gate material to the drive-in heat cycle for the source/drain, a reoxidation step for better gate insulator integrity, and salicide bridging, can be avoided. A process for forming control gates subsequent to source and drain formation in MOS fabrication is described below: In Fig. 1, a substrate 1 is formed with recessed oxide region 2 and a thin oxide layer 3, and subjected to ion implantation to adjust its threshold value.

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MOS Gate Construction Method

This article relates generally to integrated circuit fabrication and, more particularly, to a technique for forming control gates of metal oxide semiconductors with greater reliability. By depositing and patterning gate material after the source and drain are formed, potential problems, such as channeling of the source/drain implant through the gate material, subjecting the gate material to the drive-in heat cycle for the source/drain, a reoxidation step for better gate insulator integrity, and salicide bridging, can be avoided. A process for forming control gates subsequent to source and drain formation in MOS fabrication is described below: In Fig. 1, a substrate 1 is formed with recessed oxide region 2 and a thin oxide layer 3, and subjected to ion implantation to adjust its threshold value. A lift-off mask 4, such as metal or photoresist, is applied. If the metal is aluminum, it can be patterned by an isotropic wet etch to provide undercut for the lift-off pattern, and the source/drain insulator can be sputtered silicon dioxide or silicon nitride. If photoresist is used as the lift-off mask, the source/drain insulator may be evaporated silicon oxide. In Fig. 2, source 5 and drain 6 are implanted and oxide 3 is removed in the areas not covered by mask 4. Thereafter, a refractory metal 7, titanium or tungsten that will form a silicide, is deposited, followed by deposition of the source/drain insulator 8. Mask 4 is removed, and the s...