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REDUCTION OF VARIATION IN REFLECTIVITY OF A1 AND AlSi TOP METAL ON SEMICONDUCTOR DEVICES

IP.com Disclosure Number: IPCOM000007817D
Original Publication Date: 1996-Aug-01
Included in the Prior Art Database: 2002-Apr-25
Document File: 1 page(s) / 65K

Publishing Venue

Motorola

Related People

Jina Shumate: AUTHOR [+4]

Abstract

Wafers having non-uniform bond pad reflectivity have caused poor pattern recognition during the wire bond qperation at assembly. The top metal used on discrete semiconductor devices (transistors, Diodes, MOS) is Al or AlSi. Where this top metal is directly over boron doped contact areas, its reflectivity has unpredictable, non-uniform variation. In order to improve non-uniform metal reflectivity in boron doped contact areas, a mild silicon etch is used to remove a thin boron doped film prior to top metal disposition. The thin boron doped film imparts a smooth, shiny appearance to the top metal. Elevated top metal deposition temperature also plays a role in producing uniform metal reflectivity across the semiconductor wafer.

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8 Mo7vRoLA Technical Developments

REDUCTION OF VARIATION IN REFLECTIVITY OF Al AND AlSi TOP METAL ON SEMICONDUCTOR DEVICES

by Jina Shumate, Carlos Garcia, Terry Weaver and Jim Mello

  Wafers having non-uniform bond pad reflectivity have caused poor pattern recognition during the wire bond qperation at assembly. The top metal used on discrete semiconductor devices (transistors, Diodes, MOS) is Al or AlSi. Where this top metal is directly over boron doped contact areas, its reflectivity has unpredictable, non-uniform variation. In order to improve non-uniform metal reflectivity in boron doped contact areas, a mild silicon etch is used to remove a thin boron doped film prior to top metal disposition. The thin boron doped film imparts a smooth, shiny appearance to the top metal. Elevated top metal deposition temperature also plays a role in producing uniform metal reflectivity across the semiconductor wafer.

  Several designed experiments were carried out in order to reduce variation in front metal reflectivity. From these designed experiments, it was discovered that a mild silicon etch prior to metal disposition, along with elevated front metal deposition tempera- ture, consistently reduced non-uniform metal reflec- tance problems.

A new front metal process comprises:

1) Wafers are processed through pre metal clean to remove organics.

2) The wafers are then dipped in Super Q or 11:l to remove native oxide before metal deposition.

3) The wafers are immersed in a mild sil...