Application of aluminum nitrides as electrical insulator for electric capacitors is discussed. Electrical properties of aluminum nitrides are analyzed and specific use with field effect transistors is defined. Operational limits of field effect transistors are developed

Lewicki, G. W.

Maserjian, J.

English

NASA Technical Reports Server

August 1972	 B72-10425 
NASA TECH BRIEF 
NASA Pasadena Office	 -4r 
NASA Tech Briefs announce now technology derived from the U.S. space program. They are issued to encourage 
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be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Aluminum Nitride Insulating Films for MOSFET Devices 
40
The results of an investigation of the electrical 
properties of metal—insulator—metal (MIM) capacitor 
structures indicate that insulating films of aluminum 
nitride (A1N), having thicknesses of the order of 10 
mm, could be useful in charge-storage devices, pos-
sibly of the configuration MIMOS-FET. The films 
are sufficiently conductive at high fields to permit 
charging and discharging of a buried metal gate with 
relatively low short-voltage pulses (about 10 V across 
the MN film for 10 sec or less). Of great interest is 
the fact that the films are also sufficiently insulating 
at lower values of electric field to store charges for 
periods of at least three weeks to possibly one year. 
Au—AIN—Al structures were prepared by nitriding 
freshly-deposited aluminum films in a nitrogen glow 
discharge with a spatial gradient intensity, and then 
evaporating a large number of gold counter-electrodes 
to form structures having insulator thicknesses over a 
wide range of values. 
Currents in Au—AJN—Al structures were found to 
be a function of applied voltage and insulator thick-
ness separately, rather than of electric field alone (as 
for a bulk-limited process). Currents are relatively 
independent of temperature and, for insulator thick-
nesses greater than about 40 x 10 mm, relatively 
symmetrical with respect to the polarity of applied 
voltage. Over the whole range of applicable voltage, 
three different dependences of current on applied 
voltage can be observed: For low voltages, the cur-
rent is linearly dependent on voltage; for intermediate 
voltages, the current increases more rapidly with
voltage, and for higher voltages, the current increases 
even more rapidly. 
In the operation of a MIMOS-FET, the MIM 
capacitor structure would be charged in as short a 
time as possible. The results of a series of experi-
ments in which the capacitor structures were charged 
in a time period of 10-7 second showed that the dis-
charge currents responsible for decays were markedly 
different than those expected from steady-state cur-
rent—voltage relationships. It became evident that 
traps exist in'AlN and that their degree of occupancy 
strongly affects the conductivity of the insulator. 
Since trap-filling is a relatively slow process, steady-
state current—voltage characteristics would be ex-
pected to differ from instantaneous characteristics. 
The nonlinear characteristics suggest the use of AIN 
films in MIM capacitors. 
Reference: 
Lewicki, C. and Maserjian, J.: Electrical Charac-
teristics of MN Insulating Films in the Thickness 
Range 40 to 150 A. Metallurgical Transactions, vol. 2, 
March 1971, p. 678. 
Patent status: 
No patent action is contemplated by NASA. 
Source: George W. Lewicki and 
Joseph Maserjian of
Caltech/JPL
under contract to

NASA Pasadena Office

(NPO-11859) 
Category 01, 04 
40
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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Aluminum nitride insulating films for MOSFET devices

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