JP2001094088A - Thermal semiconductor infrared imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high sensitivity thermal semiconductor infrared imaging device having excellent mechanical strength. SOLUTION: A cavity 11 is made in the cross-section of a supporting leg for thermally isolating a heat sensitive part 1 from a silicon substrate from the side face thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a thermal semiconductor infrared imaging device which does not require a cooling device and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, vanadium oxide bolometer type using micromachining technology and BST (Barium-St) have been used as thermal infrared sensors that do not require a cooling device.
(Rotium-Titanium) has been commercialized. These products are composed of a heat-sensitive part that absorbs infrared rays and raises the temperature, and support legs for thermally separating the heat-sensitive part from the silicon substrate. Of these, in order to reduce the temperature distribution of the heat-sensitive part, the whole or part of the heat-sensitive part may be covered with an aluminum thin film. However, when this aluminum thin film is laminated on the support legs, heat conduction increases, and the sensitivity of the sensor decreases. Therefore, instead of laminating the aluminum thin film on the support legs, an oxide film was laminated instead. However, even in this case, since the thickness of the oxide film was large, the thermal conductivity was large, and improvement in sensitivity could not be expected. Therefore, the effect of laminating the aluminum layer for reducing the temperature distribution in the heat-sensitive portion did not appear.

Further, the heat-sensitive material of the above-mentioned sensor is not completely compatible with a silicon LSI production line. Laminated patterning had to be done. Therefore, SOI (Silicon on Insulat) is used as a thermal infrared sensor that can be completely manufactured on a silicon LSI manufacturing line.
or) An object using a pn junction on single crystal silicon using a substrate was developed. As an example of a thermal infrared imaging device using this pn junction, PH09-166497 and Pr
oc. of SPIE 3563 (1999) p.
As shown at 556, 1
It has been considered that the signal voltage is increased by forming a plurality of pn junctions in series in one heat-sensitive portion so as to be sufficiently higher than noise generated in the heat-sensitive portion itself.
However, it is necessary to use aluminum to minimize the voltage drop in the wiring between the pn junctions. However, as described above, the use of aluminum increases the thickness of the insulating film, increases the cross-sectional area of the support legs, increases the thermal conductivity of the support legs, and decreases the sensor sensitivity. .

On the other hand, if the thickness of the support leg is reduced to reduce the heat conduction between the heat-sensitive portion and the silicon substrate, the strength becomes weak, and the support leg is bent or the support leg is bent and the heat-sensitive portion contacts the silicon substrate. There was also a problem.

[0005]

Conventionally, there has been no thermal infrared imaging apparatus having high sensitivity and sufficient mechanical strength.

[0006]

In the semiconductor infrared imaging device according to the present invention, a hollow structure is formed in a section of a support leg for thermally separating a heat-sensitive portion from a silicon substrate.

[0007]

Embodiments of the present invention will be described below.

FIG. 1 is a view showing a heat-sensitive portion 1 of a thermal semiconductor infrared imaging device according to a first embodiment of the present invention. Thickness 1
A bolometer layer 3 having a thickness of 400 nm and an insulating layer 4 are stacked on a 200 nm insulating layer 2 to have a thickness of 200 nm. On this insulating layer 4, an aluminum layer 5 for reducing the temperature distribution of the entire heat-sensitive portion is formed to a thickness of 60 nm, and an insulating layer 6 is formed thereon again to a thickness of 500 nm. 10 thickness on the support legs
100 nm thick titanium wiring layer 7 on 0 nm insulating layer 2
Are laminated, and a groove 9 having a thickness of 60 nm is formed on a side surface of the insulating layer 8 having a thickness of 700 nm. The width of the narrowest part of the insulating layer 8 is 100 nm. The thermal conductivity of this support leg was reduced by about 10% as compared to before the groove was opened from the side, and the sensitivity was improved by 10%. The mechanical strength can withstand an acceleration of 200 G in a direction perpendicular to the light receiving surface.

FIG. 3 is a view showing a heat sensitive portion 31 according to another embodiment of the present invention. A plurality of pn junctions 34 are formed by diffusing impurities into the single-crystal silicon layer 33 having a thickness of 400 nm on the oxide film layer 32 having a thickness of 400 nm by ion implantation or the like. An insulating layer 35 having a thickness of 200 nm for protecting the silicon layer 33 is formed. The plurality of pn junctions are separated from each other, and are interconnected by two layers of aluminum 36 and 37 having a thickness of 400 nm so as to join the respective pn junctions in series. At this time, the thickness of the insulating film 38 on aluminum is 50
It is set to 0 nm. 400 nm thick insulating layer 3 on the support legs
4 formed by etching a single crystal silicon layer on 2
There is an insulating layer 40 having a thickness of 2500 nm sandwiching the hollow 39 of 00 nm. A groove 41 and a groove 42 having a thickness of 400 nm are formed on the side surface of the insulating layer 40.

The thickness of the narrowest part of the insulating layer 40 is 100 nm. The thermal conductivity of this support leg was reduced by about 40% and the sensitivity was improved by 40% as compared to before the groove was opened from the side. The mechanical strength can withstand an acceleration of 300 G in a direction perpendicular to the light receiving surface.

In the above-mentioned two embodiments, the grooves are formed by etching the aluminum layer which has been laminated once.
When the pattern misalignment is set to 100 nm or less, the narrowest portion of the insulating layer is also etched off in an etching process for forming a hollow structure below the heat-sensitive portion, and the pattern is formed in parallel. A plurality of thin film layers are formed. In this case, the thermal conductivity of the support leg is further reduced and the sensitivity is increased. The strength is about 10 times as compared with the case of FIG.
% Improvement in strength was observed.

[0012]

As described above, according to the present invention, it is possible to manufacture a thermal semiconductor infrared imaging device having high sensitivity and sufficient mechanical strength, which cannot be obtained by the prior art.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing a conventional thermal infrared imaging device.

FIG. 3 is a diagram showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Thermal part 2 ... Insulating layer 3 ... Bolometer layer 4 ... Insulating layer 5 ... Aluminum layer 6 ... Insulating layer 7 ... Titanium wiring layer 8 ... Insulating layer 9 ... Groove 10 ... Address line 11 ... Hollow 21 ... Heat sensitive part 22 ... Insulation Layer 23 Bolometer layer 24 Insulating layer 25 Aluminum layer 26 Insulating layer 27 Titanium wiring layer 28 Insulating layer 29 Address line 30 Hollow 31 Heat sensitive part 32 Insulating layer 33 Single crystal silicon layer 34 pn Bonding 35 ... Insulating layer 36 ... Aluminum wiring layer 37 ... Aluminum wiring layer 38 ... Insulating layer 39 ... Hollow 40 ... Insulating layer 41 ... Groove 42 ... Groove 43 ... Insulating layer 44 ... Titanium wiring 45 ... Address wiring 46 ... Hollow

Continued on the front page F term (reference) 2G065 AB02 BA02 CA13 CA27 4M118 AA01 AA08 AB01 BA06 CA15 CA35 CB12 CB13 GA10 5C024 AA06 CA12 FA01 FA09 FA11

Claims (4)

[Claims] 1. A thermal semiconductor infrared imaging device, wherein a groove is formed from a side surface of a supporting leg for thermally separating a silicon substrate from a heat-sensitive portion on which a temperature sensor is formed. 2. The thermal semiconductor infrared imaging device according to claim 1, wherein the distance between the grooves formed from the side surfaces of the support leg is set to 700 nm or less. 3. A thermal semiconductor infrared imaging apparatus, wherein a support leg for thermally separating a silicon substrate from a heat-sensitive portion on which a temperature sensor is formed is formed by a plurality of thin film layers parallel to each other. element. 4. The thermal semiconductor infrared imaging device according to claim 1, wherein the thickness of each of the plurality of parallel thin film layers is 700 nm or less per layer.