Memory, with limited number of programming cycles, is achieved by using verticle, fusible links in series with oxide breakthrough elements. Memory elements are fabricated with integrated circuit technology and are ideal for low power digital computer application

Cricchi, J. R.

Lytle, W. J.

English

NASA Technical Reports Server

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(B) Expanded Cross-Section A-A (A) Top View
Diffusion Boundary 
,.Aluminum 
Thin Oxide 
in Windows
Aluminum
000 A 
September 1971
	 Brief 71-10346 
NASA TECH BRIEF 
Goddard Space Flight Center 
NASA Tech Briefs 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 National Technical Information 
Service, Springfield; Virginia 22151. Requests for individual copies or questions relating to the. Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.. 20546. 
Nonvolatile Read/Write Memory Element: A Concept 
A nonvolatile read/write memory with a limited 
number of programming cycles may be achieved 
through the use of verticle, fusible links in series 
with oxide-breakthrough elements. The memory
of the oxide windows. An extremely thin aluminum 
layer is needed in order to obtain the high current 
density required for fusing at low input-power 
levels. 
elements can be fabricated with integrated circuit 
technology and are ideal for low-power digital 
computer applications. 
A cross-section view of a representative element 
(see fig.) shows the fusable link, which consists of 
a thin' aluminum film evaporated on a silicon 
dioxide layer, and the oxide breakthrough element. 
Initially, the memory element is an open circuit. 
If a high voltage pulse is applied, the oxide break-
through element changes into a conductive path and 
the element appears to have low resistance. A sub-
sequent high current pulse will open the fusible 
link, and the memory element again appears to have 
a high resistance. The high and low resistance values 
determine the appropriate logic state. 
The fabrication process consists of etching small 
windows, one to five micrometers in diam., in 
a thick oxide. An oxide approximately 200 A is 
grown or deposited for the breakthrough device. 
A thin aluminum layer is then deposited over all
In operation, each memory element is programmed 
to be either an open circuit (OC) or a short circuit 
(SC). The initial OC state is achieved by opening 
the fuse with a large current; the SC state is achieved 
by breaking down the oxide with a large voltage. 
These operations limit the number of times that 
the memory can be programmed. However, since 
the element density exceeds 2 x 10 6 elements per 
CM 2"
 a sufficient number of elements are available 
for reprogramming; e.g., in a 256 bit memory array 
occupying an area of 100 x 100 mils, nearly 100 
memory element pairs per bit can be obtained. This 
means that the memory could be reprogrammed 
100 times. If a larger number of bits is required, 
such as 1024 bits, then the memory could be pro-
grammed more than 25 times. 
Notes: 
1. Related work on low current fusible links and 
oxide breakthrough structures is reported in 
(continued overleaf( 
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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 ownedrights.
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NASA CR-106493 (N69-41187), "Read Only 
Memories," available through the National Tech-
nical Information Service, Springfield, Virginia 
22151. 
2. Requests for further information may be directed 
to:
Technology Utilization Officer 
Goddard Space Flight Center 
Greenbelt, Maryland 20771 
Reference: B71-10346
Patent status: 
No patent action is contemplated by NASA. 
Source: J. R. Cricchi and W. J. Lytle of 
Westinghouse Electric Corp.
under contract to
Goddard Space Flight Center
(GSC- 10993)
fl 
is 
Brief 71-10346	 Category 01


Nonvolatile read/write memory element - A concept

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