A pyroelectric detector array and the method for using it are described. A series of holes formed through a silicon dioxide layer on the surface of a silicon substrate forms the mounting fixture for the pyroelectric detector array. A series of nontouching strips of indium are formed around the holes to make contact with the backside electrodes and form the output terminals for individual detectors. A pyroelectric detector strip with front and back electrodes, respectively, is mounted over the strips. Biasing resistors are formed on the surface of the silicon dioxide layer and connected to the strips. A metallized pad formed on the surface of layer is connected to each of the biasing resistors and to the film to provide the ground for the pyroelectric detector array

Breckenridge, R.

Fripp, A. L.

Robertson, J. B.

English

NASA Technical Reports Server

States Patent 
PYROELECTRIC DETEnOR ARRAYS 4,218,620 8/1980 Oettel .................................. 250/338 
4,224,520 9/1980 Greene et al. ...................... 250/338 
Archibald L. Fripp, Williamsburg; 4.284.888 8/1981 Amleby .............................. 250/338 Inventors: 
Assignee: 
Appl. No.: 
Filed: 
James B. Robertson; Roger A. 
Breckenridge, both of Yorktown, all 
of Va. 
The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
377,892 
May 13,1982 
Related U.S. Application Data 
Division of Ser. No. 191,748, Sep. 29, 1980, Pat. No. 
4,341,012. 
Int. C l . 3  ................................................ GOlJ 1/00 
U.S. Cl. .................................................... 250/338 
Field of Search ............... 250/330, 332, 336, 338, 
250/342, 370; 357/29, 30 
References Cited 
U.S. PATENT DOCUMENTS 
4;293;768 10/1981 Adachi-et al. ...................... 250/338 
Primary Examiner-Alfred E. Smith 
Assistant Examiner-Janice A. Howell 
Attorney, Agent, or Firm-Howard J. Osborn; John R. 
Manning; William H. King 
1571 ABSTRACT 
A pyroelectric detector array and the method for using 
it. A series of holes 13 formed through a silicon dioxide 
layer 12 on the surface of a silicon substrate 11 forms the 
mounting fixture for the pyroelectric detector array. A 
series of nontouching strips of indium 14 are formed 
around the holes 13 to make contact with the backside 
electrodes 16 and form the output terminals for individ- 
ual detectors. A pyroelectric detector strip 15 with 
front and back electrodes 17 and 16, respectively, is 
mounted over the strips 14. Biasing resistors 18 are 
formed on the surface of the silicon dioxide layer and 
connected to the strips 14. A metallized pad 19 formed 
on the surface of layer 12 is connected to each of the 
biasing resistors 18 and to the film 17 to provide the 
ground for the pyroelectric detector array. 
4,198,564 4/1980 Baker et al. ......................... 250/338 
4,214,165 7/1980 Asawa ................................. 250/338 5 Claims, 3 Drawing Figures 
15 
https://ntrs.nasa.gov/search.jsp?R=19830016492 2020-03-22T00:52:55+00:00Z
US.  Patent Apr. 12, 1983 
15 
4,379,970 
12 
II 
IS 
FI 
4,379,970 
1 A 
the thin film to a metallized pad on the silicon dioxide 
surface. Biasing resistors are formed by the pyrolytic 
decomposition of silane gas to deposit polycrystalline 
silicon on the surface of the silicon dioxide. 
PYROELECXRIC DETECTOR ARRAYS 
ORIGIN OF THE INVENTION 
5 The invention described herein was made by employ- 
ees of the United States Government and mav be manu- BRIEF DESCRIPTION OF THE DRAWINGS 
factured and used by or for the Government flor govern- 
mental purposes without the payment of any royalties 
thereon or therefor. 
FIG. 1 is a perspective drawing of the invention; 
FIG. 2 is a top view of FIG. 1; and 
FIG. 3 is an end view of FIG. I. _ _  
DETAILED DESCRIPTION OF THE 
INVENTION 
This is a division of application Ser. No. 191,748, filed 
Sept. 29, 1980, now U.S. Pat. No. 4,341,012. 
~~ ~ 
Turning now to the embodiment of the invention 
selected for illustration in the drawings, the number 111 
designates a silicon substrate. A silicon dioxide layer 12 
i s  formed on substrate 11 by any conventional 
such as for example, thermally grown and/or pyrolyth- 
silicon dioxide layer B2 by etching through a photoly- 
BACKGROUND OF THE INVENTION 
The invention relates generally to Pyroelectric detec- 
tors and more specifically COncemS Pyroelectric detec- 
tor arrays fabricated in a manner compatible with si& 
con device technology. 
substrate it is desirable to mount the pyroelectric detec- 
When constructing a pyroelectric detector array On a ically deposited. A series of holes 83 are formed in the 
tor 
as possible’ This minimizes 
so that they are as ‘lose to “free hanging” 2o thographically formed mask. The substrate 11, layer 12, 
and the series of holes 13 form the mounting fixture for conductance be- tween the elements and the substrate thereby improving 
responsivity. Previously, pyroelectric detector arrays 
have been produced by cementing a pyroelectric chip 
to a ceramic substrate and wire bonding the individual 25 
a pyroelectric detector array. 
A series of nontouching strips 14 of a sift metal such 
as indium is formed around the holes 13 by coating and 
detector elements to the load resistors and to FET’s 
which are also cemented to the ceramic substrate. This 
patterning with photolythography and etching. 
These strips l 4  are the Output terminals for pyroelectric 
method requires a minimum of three wire bonds per 
element. 
detectors in the array. A pyroelectric detector strip I§ 
has a series of strips 16 of a soft metal such as indium 
The disadvantages of previous pyroelectric detector 30 deposited on one of its sides to correspond to the strips 
element, and they are cemented to the substrate creating 17 Such as gold Or chromium is formed by depositing, 
thermal contact over one entire side thereby decreasing patterning and etching on the upper surface of the P r o -  
responsivity. electric detector strip 15. The detector strip 45 is then 
It is therefore the primary object of this invention to 35 mounted over the holes 13 by cold welding the strips I4 
make the pyroelectric detector elements in an array as and 16 together. 
close to “free hanging” as possible in order to minimize A series of biasing resistors 18 are formed on the 
thermal conductance thereby, improving the responsiv- surface of silicon dioxide layer 12 by the pyrolythic 
ity of the detector elements. decomposition of silane gas to deposit polycrystalline 
It is another object of this invention to provide pyro- 40 silicon on the surface. Undoped polycrystalline silicon 
electric detector arrays which do not require several has a resistivity of approximately 2x 105 ohms per centi- 
wire bonds per element. meter. Hence, by using standard silicon device dimen- 
Other objects and advantages of this invention will sions, a biasing resistor as large as 1 x 1012 ohms can be 
become apparent hereinafter in the specification and integrated on a chip. A metallized pad such as alumi- 
drawings. 45 num is formed on the surface of layer 1% by conven- 
SUMMARY OF THE INVENTION 
The invention is pyroelectric detector arrays fabri- 
cated by forming the mounting fixture for the pyroelec- 
tric detector elements and then attaching the detector 
elements to and depositing the biasing resistors for these 
detector elements on the mounting fixture. These tech- 
niques are within standard silicon integrated circuit 
technology. 
The mounting fixture is fabricated by thermally 
growing and/or pyrolytically depositing a layer of sili- 
con dioxide on a silicon substrate. Then a series of holes 
are etched in the silicon dioxide layer through a 
photolythographically formed mask. 
A pyroelectric detector strip is mounted over the 
series of holes by coating and patterning, with photoly- 
thography and metal etching, a soft metal such as in- 
dium on both the silicon dioxide layer and the pyroelec- 
tric detector strip. These two materials are then cold 
welded together. The ground connection for the detec- 
tors is formed by depositing, patterning, and etching a 
thin f h  such as gold or chromium on the upper surface 
of the pyroelectric detector strip and then wire bonding 
arrays are that they require several wire bonds per 14 deposited on the silicon dioxide layer 1%. A thin film 
tional means. The biasing resistors i 8  are each formed 
on the surface of layer 12 in contact with a correspond- 
ing strip 14 and in contact with metallized pad 19. Film 
17 is wire bonded to metallized pad 19 by means of a 
wire 20 to form a common ground for the pyroelectric 
detector array. 
In the pyroelectric detector array described above 
the only thermal conductance from the different detec- 
tor elements to the substrate is through strips I4 sur- 
rounding the the holes to the silicon dioxide layers. 
The advantages of this invention over prior art de- 
vices are numerous: it provides pyrodetector arrays at 
lower cost, better image registration, improved device 
reliability, and quasi-free mounting for improved re- 
sponsivity. 
What is claimed as new and desired to be secured by 
Letters Patent of the United States is: 
1. A pyroelectric detector array comprising: 
a semiconductor substrate; 
an insulator layer on one side of said semiconductor 
a series of holes in said insulator layer; 
substrate; 
50 
55 
60 
65 
4.3 79,970 
a 
I -  
3 
series of nontouching strips of soft. metal on said 
insulator layer with each strip being around a cor- 
responding one of said series of holes wherein each 
strip is the output terminal for a pyroelectric detec- 
tor: 
a pyroelectric detector strip mounted over said series 
of holes in contact with said series of strips; and 
a metal layer on said pyroelectric detector strip to 
provide a ground connection for the pyroelectric 
detectors. 
2. A pyroelectric detector array according to claim 1 
including a series of biasing resistors on said insulator 
layer with each having electrical contact with a corre- 
4 
sponding one of said series of nontouching strips of soft 
metal and a metallized pad on the insulator layer in 
electrical contact with the other side of each of said 
biasing resistors. 
3. A pyroelectric detector array according to claim 2 
wherein said metal layer is wire bonded to said metal- 
lized pad. 
4. A pyroelectrid detector array according to claim 1 
wherein said semiconductor is silicon. 
5. A pyroelectric detector array according to claim 4 
wherein said insulator layer is a silicon dioxide layer. 
* * * * e  
20 
25 
30 
35 
40 
45 
50 
55 
65 


Pyroelectric detector arrays

A pryoelectric detector array and the method for making it are described. A series of holes formed through a silicon dioxide layer on the surface of a silicon substrate forms the mounting fixture for the pyroelectric detector array. A series of nontouching strips of indium are formed around the holes to make contact with the backside electrodes and form the output terminals for individual detectors. A pyroelectric detector strip with front and back electrodes, respectively, is mounted over the strip. Biasing resistors are formed on the surface of the silicon dioxide layer and connected to the strips. A metallized pad formed on the surface of the layer is connected to each of the biasing resistors and to the film to provide the ground for the pyroelectric detector array

Breckenridge, R. A.

[54] PYROELECTRIC DETECTOR ARRAYS 4,039,833 8/1977 Thom .................................. 250/332 
[75] Inventors: 
E731 Assignee: 
[21] Appl. No.: 
[22] Filed: 
Archibald L. Fripp, Williamsburg; 
James B. Robertson; Roger A. 
Breckenridge, both of Yorktown, all 
of Va. 
The United States of America as 
represented by the Administrator, 
National Aeronautics and Space 
Administration, Washington, D.C. 
191,748 
Sep. 29, 1980 
Int. ( 3 . 3  ............................................. HOlC 17/06 
US. Cl. ..................................... 29/620; 29/576 J; 
29/576 S; 250/332; 250/370 
Field of Search ................... 29/620, 576 J, 576 S, 
29/610 R, 884, 876; 250/21 J, 332, 334, 338, 
370 
References Cited 
U.S. PATENT DOCUMENTS 
3,480,777 11/1969 Astheimer ............................. 73/355 
3,961,998 6/1976 Scharnhorst ..................... 250/211 J 
3,989,946 11/1976 Chapman et al. ................... 250/332 
4,011,916 12/1977 King .................................... 250/332 
4,039,116 8/1977 Choffin ............................... 228/123 
4,063,268 12/1977 King .................................... 250/332 
4,079,507 3/1978 King .................................... 250/332 
4,262,198 4/1981 Gupta .................................. 250/332 
4,286,278 8/1981 Lorenze et al. ..................... 250/332 
Primary Examiner-Leon Gilden 
Attorney, Agent, or Firm-William H. King; John R. 
Manning; Howard J. Osborn 
1571 ABSTRACT 
A pyroelectric detector array and the method for mak- 
ing it. A series of holes 13 formed through a silicon 
dioxide layer 12 on the surface of a silicon substrate 11 
forms the mounting fixture for the pyroelectric detector 
array. A series of nontouching strips of indium 14 are 
formed around the holes 13 to make contact with the 
backside electrodes 16 and form the output terminals 
for individual detectors. A pyroelectric detector strip 
15 with front and back electrodes 17 and 16, respec- 
tively, is mounted over the strips 14. Biasing resistors 18 
are formed on the surface of the silicon dioxide layer 
and connected to the strips 14. A metallized pad 19 
formed on the surface of layer 12 is connected to each 
of the biasing resistors 18 and to the film 17 to provide 
the ground for the pyroelectric detector array. 
7 Claims, 3 Drawing Figures 
https://ntrs.nasa.gov/search.jsp?R=19820023783 2020-03-21T17:27:56+00:00Z
Jul. 27, 1982 
19 13 
13 
12 
II 
13 
1 
4,341,012 
PYROELECXRIC DETECTOR ARRAYS 
ORIGIN OF THE INVENTION 
The invention described herein was made by employ- 
ees of the United States Government and may be manu- 
factured and used by or for the Government for govern- 
mental purposes without the payment of any royalties 
thereon or therefor. 
BACKGROUND OF THE INVENTION 
The invention relates generally to pyroelectric detec- 
tors and more specifically concerns pyroelectric detec- 
tor arrays fabricated in a manner compatible with sili- 
con device technology. 
When constructing a pyroelectric detector array on a 
substrate it is desirable to mount the pyroelectric detec- 
tor elements so that they are as close to “free hanging” 
as possible. This minimizes thermal conductance be- 
tween the elements and the substrate thereby improving 
responsivity. Previously, pyroelectric detector arrays 
have been produced by cementing a pyroelectric chip 
to a ceramic substrate and wire bonding the individual 
detector elements to the load resistors and to FET’s 
which are also cemented to the ceramic substrate. This 
method requires a minimum of three wire bonds per 
element. 
The disadvantages of previous pyroelectric detector 
arrays are that they require several wire bonds per 
element, and they are cemented to the substrate creating 
thermal contact over one entire side thereby decreasing 
respnsivity. 
It is therefore the primary object of this invention to 
make the pyroelectric detector elements in any array as 
close to “free hanging” as possible in order to minimize 
thermal conductance thereby, improving the responsiv- 
ity of the detector elements. 
It is another object of this invention to provide pyro- 
electric detector arrays which do not require several 
wire bonds per element. 
Other objects and advantages of this invention will 
become apparent hereinafter in the specification and 
drawings. 
SUMMARY OF THE INVENTION 
The invention is pyroelectric detector arrays fabri- 
cated by forming the mounting fmture for the pyroelec- 
tric detector elements and then attaching the detector 
elements to and depositing the biasing resistors for these 
detector elements on the mounting fixture. These tech- 
niques are within standard silicon integrated circuit 
technology. 
The mounting fmture is ’fabricated by thermally 
growing and/or pyrolytically depositing a layer of sili- 
con dioxide on a silicon substrate. Then a series of holes 
are etched in the silicon dioxide layer through a photo- 
lithographically formed mask. 
A pyroelectric detector strip is mounted over the 
series of holes by coating and patterning, with photoly- 
thography and metal etching, a soft metal such as in- 
dium on both the silicon dioxide layer and the pyroelec- 
tric detector strip. These two materials are then cold 
welded together. The ground connection for the detec- 
tors is formed by depositing, patterning, and etching a 
thin film such as gold or chromium on the upper surface 
of the pyroelectric detector strip and then wire bonding 
the thin film to a metallized pad on the silicon dioxide 
surface. Biasing resistors are formed by the pyrolytic 
5 
10 
15 
20 
25 
30 
35 
40 
45 
50 
55 
60 
65 
2 
decomposition of silane gas to deposit polycrystalline 
silicon on the surface of the silicon dioxide. 
BRIEF DESCRIPTION OF THE DRAWINGS 
FIG. 1 is a perspective drawing of the invention; 
FIG. 2 is a top view of FIG. 1; and 
FIG. 3 is an end view of FIG. 1. 
DETAILED DESCRIPTION OF THE 
INVENTION 
Turning now to the embodiment of the invention 
selected for illustration in the drawings, the number 11 
designates a silicon substrate. A silicon dioxide layer 12 
is formed on substrate 11 by any conventional means 
such as for example, thermally grown and/or pyrolyth- 
ically deposited. A series of holes 13 are formed in the 
silicon dioxide layer 12 by etching through a photoly- 
thographically formed mask. The substrate 11, layer 12, 
and the series of holes 13 form the mounting fixture for 
a pyroelectric detector array. 
A series of nontouching strips 14 of a soft metal such 
as indium is formed around the holes 13 by coating and 
patternhg with photolythography and metal etching. 
These strips 14 are the output terminals for pyroelectric 
detectors in the array. A pyroelectric detector strip 15 
has a series of strips 16 of a soft metal such as indium 
deposited on one of its sides to correspond to the strips 
14 deposited on the silicon dioxide layer 12. A thin film 
17 such as gold or chromium is formed by depositing, 
patterning and etching on the upper surface of the pyro- 
electric detector strip 15. The detector strip 15 is then 
mounted over the holes 13 by cold welding the strips 14 
and 16 together. 
A series of biasing resistors 18 are formed on the 
surface of silicon dioxide layer 12 by the pyrolythic 
decomposition of silane gas to deposit polycrystalline 
silicon on the surface. Undoped polycrystalline silicon 
has a resistivity of approximately 2X lO5ohms per centi- 
meter. Hence, by using standard silicon device dimen- 
sions, a biasing resistor as large as 1 x 1012 ohms can be 
integrated on a chip. A metallized pad such as alumi- 
num is formed on the surface of layer 12 by conven- 
tional means. The biasing resistors 18 are each formed 
on the surface of layer 12 in contact with a correspond- 
ing strip 14 and in contact with metallized pad 19. Film 
17 is wire bonded to metallized pad 19 by means of a 
wire 20 to form a common ground for the pyroelectric 
detector array. 
In the pyroelectric detector array described above 
the only thermal conductance from the different detec- 
tor elements to the substrate is through strips 14 sur- 
rounding the the holes to the silicon dioxide layers. 
The advantages of this invention over prior art de- 
vices are numerous: it provides pyrodetector arrays at 
lower cost, better image registration, improved device 
reliability, and quasi-free mounting for improved re- 
sponsivity. 
What is claimed as new and desired to be secured by 
Letters Patent of the United States is: 
1. A method for mounting a pyroelectric detector 
array on silicon integrated circuits comprising the steps 
Of: 
forming a silicon dioxide layer on a silicon substrate; 
forming a series of holes in said silicon dioxide layer; 
coating said silicon dioxide layer with a series of 
nontouching strips of soft metal with each strip 
being over and around one of said holes, wherein 
4,341 ,O 12 
3 4 
each strip is the output terminal for a pyroelectric 
detector; formed mask. 
coating one side of a pyroelectric detector strip with 
a series of strips of soft metal; 
mounting said pyroelectric detector strip over said 
series of holes such that said series of strips of soft 
metal on said detector strips are in contact with 
said series of strips on said silicon dioxide layers; 
and 
forming a metal layer on the side opposite said one 
side of said pyroelectric detector strip to provide a 
ground connection for the pyroelectric detector 
array. 
2. A method for mounting a pyroelectric detector 15 
formed by etching through a photolythographically 
4. A method for mounting a pyroelectric detector 
array according to claim 1 wherein said soft metal is 
5. A method for mounting a pyroelectric detector 
array according to claim including the steps of form- 
ing a series of biasing resistors on the surface of said 
silicon dioxide layer with each having one side in elec- 
10 trical contact with a corresponding one of said series of 
non-touching strips of soft metal on the surface of said 
silicon dioxide layer and a metallized pad on the silicon 
dioxide surface in electrical contact with the other side 
of each of said biasing resistors. 
6. A method for mounting a pyroelectric detector 
array according to claim 5 wherein said biasing resistors 
are formed by the pyrolytic decomposition of silane gas 
to deposit polycrystalline silicon on the surface of the 
silicon dioxide. 
7. A method for mounting a pyroelectric detector 
array according to claim 5 including the step'of wire 
bonding said metal layer on one side of said pyroelectric 
detector strip to said metallized pad. 
5 indium. 
array according to wherein said step of mount- 
ing said pyroelectric detector strip over said series of 
holes comprises the step of cold welding said series of 
strips of soft metal on said detector strip to said series of 20 
strips on said silicon dioxide layer. 
3. A method for mounting a Pyroelectric detector 
array according to claim 1 wherein said step of forming 
a series of holes in said silicon dioxide layer is per- * * * * *  
25 
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45 
50 
55 
60 
65 


Pyroelectric detector arrays

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