Electric heating – Metal heating – By arc
Reexamination Certificate
2001-10-31
2003-09-23
Elve, M. Alexandra (Department: 1728)
Electric heating
Metal heating
By arc
C219S121850
Reexamination Certificate
active
06624384
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention broadly relates to a non-cooling type infrared ray sensor of a bolometer type. More specifically, this invention is directed to an infrared ray sensor in which a temperature is varied by absorbing an incident light ray of an infrared ray and a signal of a radiation intensity of the infrared ray is read-out by varying an electrical resistance value in dependency upon the temperature variation.
The bolometer utilizes temperature variation of an electrical resistance value of metal or a semiconductor thin-film, which is thermally insulated from a substrate material.
In general, when temperature coefficient of the electrical resistance (TCR) of the material for the bolometer becomes high, temperature resolution (NETD) of the infrared ray sensor becomes low, thus improving sensitivity.
An alloy thin-film such as a nickel iron alloy has low TCR of about 0.5%. In consequence, it is considered that a conductive oxide thin-film such as a vanadium oxide thin-film, a perovskite type Mn oxide film, and a YBa
2
Cu
3
Ox thin-film is advantageous as a resistive film for the bolometer for use in the infrared ray sensor with high sensitivity.
This reason will be explained as follows.
These conductive oxide thin-films represents excessively high TCR of about 2%/K in the vanadium oxide thin-film, about 2~5%/K in the YBa
2
Cu
3
Ox thin-film. Further, the conductive oxide thin film represents extremely high TCR of 5%/K or higher, particularly exceeding 10%/K in the perovskite type Mn oxide by utilizing phase transition between an insulator and a metal caused by magnetic phase transition inherent to such material.
Referring now to
FIG. 1
, description will be hereinafter made about the structure of the infrared ray sensor in which the oxide thin-film is used as the resistive element for the bolometer in the related art.
In
FIG. 1
, the reference numeral
1
represents a Si substrate, the reference numeral
2
represents a bridge structure body, a reference numeral
3
represents a space, the reference numeral
4
represents a resistive element for the bolometer, the reference numeral
5
represents a wiring pattern, and a reference numeral represents an infrared ray reflection film.
As illustrated in
FIG. 1
, the infrared sensor of the bolometer type generally has such a micro-bridge structure that the resistive element
4
for the bolometer is insulated from the Si substrate
1
via the space
3
.
To this end, the resistive element
4
for the bolometer can be thermally insulated from the silicon substrate
1
. Under such a circumstance, the oxide thin-film selected from the above films is used as the resistive elements for the bolometer.
With this structure, when the infrared ray is entered to a cell, a part thereof is initially absorbed by the infrared ray absorption film
7
, and the infrared ray, which is partially transmitted, is reflected by the infrared ray reflection film
8
. A resultant infrared ray is completely absorbed by the infrared ray absorption film
7
. The absorbed infrared ray generates heat, and heats a diaphragm to thereby vary the electrical resistance of the resistive element
4
for the bolometer.
Then, a signal is detected by a read-out circuit formed in the Si substrate
1
via the wiring pattern
5
connected to the Si substrate
1
through a supporting portion of the bridge structure body
2
from the both ends of the resistive element
4
for the bolometer.
Subsequently, a process for manufacturing the aforementioned infrared ray sensor will be explained as follows.
Initially, metal with infrared reflection rate such as WSi is deposited on the Si substrate
1
with the read-out circuit by the sputtering method to thereby form the infrared reflection film
8
.
Then, a sacrifice layer is formed at the position of the space, which will be formed later, on the infrared ray reflection film
8
by the use of a polysilicon film or the like. Herein, it should be noted that the polysilicon film may be deposited by CVD method.
An insulating film such as SIN and SiO
2
is deposited on the sacrifice layer by the plasma CVD method, thereby forming the bridge structure body
2
. Next, the metal with low thermal conductivity such as Ti is formed on the bridge structure body
2
by the sputtering method, is exposed, is developed and is etched to thereby form the wiring pattern
5
.
Successively, the oxide thin-film serving as the resistive element
4
for the bolometer such as a vanadium oxide thin-film, a perovskite type Mn oxide film, and a YBa
2
Cu
3
Ox thin film is deposited by the sputtering method. The resistive element for the bolometer is also formed by the development and etching process like the above wiring pattern.
The insulating film such as SiO
2
is deposited on the bridge structure body
2
including the resistive element by the plasma CVD method in order to protect the resistive element
4
for the bolometer, thus forming the protection film
6
.
Further, the infrared ray absorption film
7
such as TiN is deposited on the protection film
6
by the use of the reactive sputtering method.
Finally, the sacrifice layer is wet-etched by hydrazine to form the space
3
. Through aforementioned multiple steps, such a diaphragm that the portion including the resistive element
4
for the bolometer is floated is completed.
By adopting such a structure, it is difficult that heat of the infrared ray absorbed by the infrared ray absorption film
7
is escaped to an external portion. Thereby the heat is efficiently utilized to raise up the temperature of the resistive element
4
for the bolometer
As discussed above, the non-cooling type infrared ray sensor of the bolometer type can effectively detect the infrared ray by forming the diaphragm of such a structure that the portion including the resistive element
4
for the bolometer is floating.
The non-cooling type infrared sensor is advantageous in low price in addition to operability with respect to a shape and a weight in comparison with the cooling type infrared sensor. However, the conventional non-cooling type infrared ray sensor is produced by using an excessively complex production process.
For example, paying attention for a deposition process, the infrared ray reflection film
8
, the resistive element
4
for the bolometer, the wiring pattern
5
, and the infrared ray absorption layer
7
are deposited by the sputtering method. Further, the sacrifice layer such as the polysilicon film, the bridge structure body
2
, and the protection film
6
are formed by the use of the CVD method.
Moreover, many production steps such as a resist applying step, a drying step, an exposing step, a developing step, a resist removing step, and a washing step are required for formation of each layer such as the wiring pattern
5
and the resistive element
4
for the bolometer.
In the conventional production process, a vapor deposition process with high cost is carried out many times, and a plurality of steps are necessary in the patterning, thus increasing the production cost.
Accordingly, if the vapor deposition process or the patterning step can be reduced, the production cost will be lowered, thereby providing the non-cooling type infrared ray sensor with lower cost.
In addition, the deposition temperature of the resistive element
4
for the bolometer occurs problems during manufacturing the non-cooling type infrared ray sensor of the bolometer type. This is because the resistive element
4
for the bolometer is formed on the Si substrate
1
with the signal read-out circuit via the space
3
for thermally insulating, as discussed above.
Further, it is required that the deposition temperature is low at 400~500° C. not to destroy the signal read-out circuit formed in the Si substrate. Moreover, it is also impossible to utilize a physical etching method such as ion milling during forming the pattern of the resistive element
4
for the bolometer. This is because the Si signal read-out circuit formed on an under layer is damaged by the physical etching.
Thus, it is particularly required th
Kubo Yoshimi
Kumagai Toshiya
Mizuta Susumu
Shimakawa Yuichi
Tsuchiya Tetsuo
Elve M. Alexandra
Sughrue & Mion, PLLC
LandOfFree
Method for manufacturing infrared ray sensor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for manufacturing infrared ray sensor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for manufacturing infrared ray sensor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3030214