Technique that makes the metal leads integral to the transistor wafer and reduces capacitance in the device, thereby increasing its efficiency is outlined

Carley, D. R.

Casterline, E. T.

English

NASA Technical Reports Server

November 1968
	 Brief 68-10518 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information Springfield, Virginia 22151. 
Integrated Metal Transistor Leads 
Base Contact 
.
Si Wafer	 Contac-i
Metal Lead 
Si02	 Si Wafer 
The problem: 
In the conventional manufacture of transistors, 
large pellet bonding terminals are required as targets 
for the bonded lead wires and contribute to device 
capacitance. Additionally, the incidence of bonding 
lead wires having different lengths is a factor that 
results in an increased inductance to those emitters 
being fed by the longer wires and subsequent degen-
eration in their injection. 
The solution: 
A technique that makes the metal leads integral to 
the transistor wafer. This appreciably reduces capaci-
tance in the device, thereby increasing its efficiency. 
How it's done: 
After defining the base contacts in the oxide and de'-
positing Au in the openings, the wafer is again coated 
with a photoresist and an opening is made in the resist. 
A layer (60,000-100,000 A) of Al is then evaporated over 
the surface .of the wafer, forming the composite struc-
ture shown in the left figure. The metal is next coated 
with photoresist and defined by electrolytic etching to 
produce a pattern on each pellet in the form shown in 
the center figure. 
The wafer is next scribed on each side by standard 
scribing techniques to assist separation of the indivi-
dual pellets, accomplished by placing the wafer in hot 
benzene sulphuric acid which dissolves all the photo-
resist, leaving pellets like that shown in the right 
figure. 
Notes: 
1. Measurements made on TA2675 devices fabricated 
with integral leads and fabricated with wire-bonded 
leads showed a 26% capacitance reduction in the 
integral lead device. 
2. In using integral leads, length of the bond wires 
is controlled by photolithographic techniques, as-
suring equal inductance to the pellet. 
3. No additional documentation is available. In-
quiries may be directed to: 
Technology Utilization Officer 
Goddard Space Flight Center 
Greenbelt, Maryland 20771 
Reference: B68-10518 
Patent status: 
No patent action is contemplated by NASA. 
Source: E. T. Casterline and D. R. Carley 
of Radio Corporation of America 
under contract to 
Goddard Space Flight Center 
(GSC790536) 
Category 01 
This document was prepared under the sponsorship of the National 
AerOnautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19680000474 2020-03-12T06:02:44+00:00Z


Integrated metal transistor leads

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