Browse Prior Art Database

LASER SCRIBE EXHAUST

IP.com Disclosure Number: IPCOM000007205D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2002-Mar-05
Document File: 3 page(s) / 89K

Publishing Venue

Motorola

Related People

Brad Schulze: AUTHOR [+3]

Abstract

The standard way to serialize waters in the fab- rication process is to laser scribe the characters directly onto the wafer surface. The laser scribe' proc- ess produces "slag" as a byproduct. The slag is gen- erated when the laser strikes the surface of the wafer with sufficient energy to displace the silicon and leave a trench behind. These trenches form the scribed characters. The displaced silicon is boiled off the surface and redeposited as contamination across the wafer. The redeposited silicon is still hot enough to fuse to the surface of the wafer and becomes very difficult to remove with subsequent cleans. A method to reduce the redeposited slag was needed to improve SOLUTION: It was discovered that the orientation of the water inside the scribe chamber had a large effect on the number of slag particles deposited on the wafer. A hole existed on the back of the scriber near an in air intake from the factory. This hole created a ventury effect inside the scriber pulling air in only one direc- tion across the surface of the wafers being scribed. Particles generated from the scribe would get caught in the airflow and be pulled across the wafer as shown below.

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MO-LA Technical Developments Volume22 June 1994

LASER SCRIBE EXHAUST

by Brad Schulre, Kerry Deslatte and Ben Huff

PROBLEM:

defect levels.

  The standard way to serialize waters in the fab- rication process is to laser scribe the characters directly onto the wafer surface. The laser scribe' proc- ess produces "slag" as a byproduct. The slag is gen- erated when the laser strikes the surface of the wafer with sufficient energy to displace the silicon and leave a trench behind. These trenches form the scribed characters. The displaced silicon is boiled off the surface and redeposited as contamination across the wafer. The redeposited silicon is still hot enough to fuse to the surface of the wafer and becomes very difficult to remove with subsequent cleans. A method to reduce the redeposited slag was needed to improve

SOLUTION:

  It was discovered that the orientation of the water inside the scribe chamber had a large effect on the number of slag particles deposited on the wafer. A hole existed on the back of the scriber near an in air intake from the factory. This hole created a ventury effect inside the scriber pulling air in only one direc- tion across the surface of the wafers being scribed. Particles generated from the scribe would get caught in the airflow and be pulled across the wafer as shown below.

Laser Scribe here would generate only 60 particles >0.5 microns

WAFER

Constant Airflow of 24 Linear Feet/Minute

of 2000 particles >O.S microns

0 MmrOl~, Inc. 1994 61...