System monitors fabrication of high-quality optical filters and other precise film deposition operations. System generates output signal of an element that changes rapidly when deposition process changes or stops, and eliminates defects of single-wavelength systems. Five additional advantages of dual-wavelength system are listed

Zurasky, J. L.

English

NASA Technical Reports Server

December 1970
	 Brief 70-10658 
NASA TECH BRIEF 
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, 
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nology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Dual-Wavelength System Monitors Deposition of Films: A Concept 
Tuned	 Monochromatic 
nd. Difference 74T}hotOdetector
	 Evaporation Amplifier 
Digital Readout	 _________________ Chamber 
Tuned 
Amplifier
Monochromatic  S  Filter	 Filter 
 Tuned	 I
 One-Way 
Amplifier Mirror
 Sum-and-Difference qLtt Amplifier: L Digital Readout	 Photodetector
Dual-Color 
Tuned Filter 
Amplifier
Monochromatic Filter	 i Beam 
I I	 Chopper 
Light Source; I I Focusing Lens
An improved dual-wavelength system (see fig.) 
monitors the fabrication of high-quality optical filters 
and other highly precise film deposition operations. 
Single-wavelength monitoring systems lack the re-
quired degree of accuracy. Dual wavelength systems 
were designed to generate the output signal of an ele-
ment that would change rapidly at the point when the 
deposition process should change or stop. 
A problemofea'iilier dual-wavelength systems was 
that multiple paths were needed for filterin g
 and re-
combining the light beams for the various colors. 
Many of the components required critical optical 
alignment, and there was little assurance that both 
colors were monitoring the same area of the sample. 
The new system eliminates these defects, and has 
the following advantages: (1) A stable light source is 
not necessary; minor variations are cancelled using 
a ratio test. This test between signals permits the deter- 
mination of any point along the monitor curve. Exact 
1/4- A positions can be noted from the difference (continued overleaf) 
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Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
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signal, but extremely accurate filters are not needed. 
(2) Both transmitted and reflected light can be meas-
ured. (3) Incorporated filters must be measured exactly 
for peak transmission but need not be manufactured 
for a predetermined wavelength. (4) All monitoring 
light travels the same path simultaneously. (5) The 
requirements for the optical components are not 
restrictive. 
The concept should be of interest to semiconductor 
products manufacturers and manufacturers of pig-
ments used in spectrum-selective dyes for the pharma-
ceutical and chemical industries. 
Notes: 
1. This innovation is in the conceptual stage only; 
at the time of this publication no model or proto-
type exists. 
2. No further documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Code A&TS-TU 
Huntsville, Alabama 35812 
Reference: B70-10658
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to: 
Patent Counsel 
Mail Code A&TS-PAT 
George C. Marshall Space Flight Center 
Marshall Space Flight Center, Alabama 35812 
Source: J. L. Zurasky
Marshall Space Flight Center 
(MFS-20675)
^j 
^j 
. 
Brief 70-10658	 Category 03


Dual-wavelength system monitors deposition of films - A concept

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