Laser scribing eliminates microcracking at scribe line intersections, minimizes or eliminates preparation of scribe channels, and increases yield during the breaking process. Rapid overlapping of spots in the form of a line permits scribing speeds of 1.5 to 2.5 in./sec at 50 pulses/sec

Calihan, C.

English

NASA Technical Reports Server

October 1970	 Brief 70-10437 
NASA TECH BRIEF 
NASA Tech B riefs announce new technology derived from the U .S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the Clearinghouse for Federal Scientific and Technical 
Information, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Laser Scribing of Silicon Wafers 
A laser has been used as a scribing tool to improve 
silicon wafer dicing. Results show that laser scribing 
can eliminate microcracking at scribe line inter-
sections, minimize or eliminate preparation of the 
scribe channels, and increase yield during the break-
ing process. For this experiment, silicon wafers .006-in. 
to .007-in, thick, with various circuitry on one side 
and gold plate on the back, were used. A focused 
yttrium aluminum garnet (YAG) laser was employed 
•
to partially penetrate a silicon wafer on the back side. 
The wafers were then broken in the standard manner. 
The first method involving a series of distinct spots 
separated by intervals of unlased silicon did not prove 
feasible because the scribe was not defined well enough 
for the break to follow. 
A second, successful, method utilized overlapping 
spots. Back side cutting with a continuous line scribe 
resulted in a well defined break. Since only a small 
fraction of a watt impinges on the wafer, no heating 
problems were anticipated with epitaxial circuits. 
Microcracking, normally found at the junctions of 
conventionally scribed wafers, was not prevalent with 
this method. 
Sufficiently rapid overlapping of spots in the form 
of a line may permit the attainment of high scribing 
speeds. Laser pulse rates of 50 pulses per second re-
sulted in scribing speeds of 1.5 to 2.5 in./sec. With 
200 pulses per second, the cutting speed should ap-
proach 6 to 10 in./sec. 
The sample quantity of wafers scribed did not permit 
defining a yield factor. However, cleanliness of the
break, complete elimination of chipped scribe lines, 
and relatively large penetration through the wafer 
promised a considerable increase in yield over present 
scribing methods. Additionally, this technique elimi-
nated any preparation of the scribed channel. Further 
experiments using pure silicon (without gold plate) 
yielded even better results. 
Notes: 
1. This YAG laser system should successfully compete 
with existing techniques as a high-speed production 
tool for scribing silicon wafers and should interest 
semiconductor manufacturers. 
2. Requests for further information may be directed 
to:
Technology Utilization Officer 
Headquarters 
National Aeronautics 
and Space Administration 
Washington, D.C. 20546 
Reference: B70-10437 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546.
Source: C. Calihan of 
Spacerays, Inc.
under contract to

Electronics Research Center
(ERC- 10386) 
Category .01 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned.rights.
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Laser scribing of silicon wafers

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