Browse Prior Art Database

Method for Enhancing Yield and Breakdown Field of Aluminum Gate Devices

IP.com Disclosure Number: IPCOM000039099D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 70K

Publishing Venue

IBM

Related People

Nguyen, TN: AUTHOR

Abstract

The yield and breakdown field of thin oxide Al gate MOS devices are improved by adding 4 wt% copper to the aluminum before deposition to minimize the reactivity of Al to SiO2 . Aluminum is known to be reactive to SiO2 at temperatures as low as 400oC. It can react with the oxide and decrease its thickness by as much as 15 angstroms during metal evaporation at room temperature. After a standard post-metal anneal to reduce interface-trap density, aluminum can penetrate locally into the oxide and cause low-field breakdown and even short circuits in MOS capacitors. The cumulative distributions of breakdown field of Al gate capacitors before and after post-metal anneal in Fig. 1 demonstrate this effect. The breakdown field decreases from 11 to 3.5 MV/cm and the yield drops from 93.3% to 0% after a 400oC 20-minute anneal.

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 79% of the total text.

Page 1 of 2

Method for Enhancing Yield and Breakdown Field of Aluminum Gate Devices

The yield and breakdown field of thin oxide Al gate MOS devices are improved by adding 4 wt% copper to the aluminum before deposition to minimize the reactivity of Al to SiO2 . Aluminum is known to be reactive to SiO2 at temperatures as low as 400oC. It can react with the oxide and decrease its thickness by as much as 15 angstroms during metal evaporation at room temperature. After a standard post-metal anneal to reduce interface-trap density, aluminum can penetrate locally into the oxide and cause low-field breakdown and even short circuits in MOS capacitors. The cumulative distributions of breakdown field of Al gate capacitors before and after post-metal anneal in Fig. 1 demonstrate this effect. The breakdown field decreases from 11 to 3.5 MV/cm and the yield drops from 93.3% to 0% after a 400oC 20-minute anneal. As a result, aluminum is not widely used as a gate material for thin-oxide MOS capacitors and transistors, although it is an excellent material from the resistivity and work function points of view.

(Image Omitted)

It has been found experimentally that the reactivity of aluminum to oxide could be greatly reduced by adding about 4 wt% copper to the aluminum before evaporation. Furthermore, a substantial increase in the breakdown field of Al-Cu gate capacitors could be obtained after a post-metal anneal. The average penetration depth of Al-Cu in oxide during deposition, determined by...