JP2000353799A - Infrared detector and infrared detector array - Google Patents

Abstract

(57) [Problem] To provide an infrared detector capable of controlling a saturated charge amount of a detection unit without deteriorating detection sensitivity. The infrared light includes a semiconductor substrate on which a light absorbing film is formed and through which infrared light can pass, and a conductive reflective film formed on the light absorbing film with an insulating film interposed therebetween. The detector 21 has a second insulating film 1 on the reflective film 10.
6, a conductive film 15 is formed, and a second insulating film 16 sandwiched between the reflective film 10 and the conductive film 15 is formed separately from the insulating film 9 sandwiched between the light absorbing film 8 and the reflective film 10. By forming a new capacitance section, the saturation charge amount of the detection section can be controlled as a whole without deteriorating the detection sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an infrared detector for photoelectrically converting and detecting infrared light and an infrared detector array having a plurality of such infrared detectors.

[0002]

2. Description of the Related Art Infrared detectors of this type are arranged in, for example, an array, and are used as detectors of infrared solid-state imaging devices for detecting infrared rays emitted from objects. Used in

As shown in FIG. 6, a conventional infrared detector 30 includes a detection unit 30a including a p-type silicon semiconductor substrate 7, a light absorbing film 8, an insulating film 9, and a reflecting film 10 capable of transmitting infrared light. , Transfer gate 2, vertical shift register 3, guard ring 11, element isolation oxide film 1,
2, a charge transfer section 30b including a P ⁺ stop layer 13 and an interlayer insulating film 14.

In the infrared detector 30, infrared light incident from the back surface of the semiconductor substrate 7 passes through the semiconductor substrate 7, reaches the light absorbing film 8, and is photoelectrically converted. The photoelectrically converted infrared light is stored as signal charges in the detection unit 30a of the infrared detector 30. The signal charges stored in the detection unit 30a are transferred to the vertical shift register 3, sequentially transferred in the vertical direction, further transferred in the horizontal direction, and output via a horizontal shift register (not shown) to an output amplifier (not shown). Output from

As described above, since the signal charges are transferred from the detection unit 30a to the vertical shift register 3, the horizontal shift register, and the output amplifier, the maximum amount that the vertical shift register 3, the horizontal shift register, and the output amplifier can transfer. The charge amount (saturated charge amount) is preferably larger than the maximum charge amount that can be extracted from the detection unit 30a, and takes into account each saturated charge amount of the detection unit 30a, the vertical shift register, the horizontal shift register, and the output amplifier. Therefore, it is necessary to design the infrared detector 30.

The amount of saturation charge of the detecting section 30a is
The capacitance of the detection unit 30a is controlled by adjusting the capacitance of the detection unit 30a because the capacitance of the detection unit 30a is adjusted. 8, the capacitance C _c between the guard ring 11 and the P ⁺ channel stop layer 13, the capacitance C _g between the semiconductor substrate 7 and the guard ring 11, and the semiconductor substrate. 7 is the sum of the capacitance C _s of an infrared detector 3
0, only the capacitance C ′ can be changed in the design. Therefore, to control the saturation charge of the detection unit 30a, the saturation charge accumulated in the insulating film 9, that is, the capacitance C
'Must be changed. Means for changing the capacitance include the area of the reflective film and the thickness of the insulating film.

[0007]

However, the reflection film plays the role of an electrode of the capacitance C '.
Originally, the infrared ray transmitted through the light absorbing film 8 is reflected and made incident on the light absorbing film 8 again. Therefore, in order to improve the detection sensitivity of the infrared detector 30, it is necessary to form the reflective film 10 so as to cover directly above the light absorbing film 8. If the area where the reflective film 10 is formed is changed, the infrared detector 3
There is a problem that the detection sensitivity of 0 is reduced.

The thickness of the insulating film 9 is set so as to optically resonate the incident infrared light between the reflecting film 10 and the Si substrate 7. When the capacitance C ′ is controlled, there is a problem that the detection sensitivity of the infrared detector 30 is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an infrared detector capable of controlling the amount of saturated charges in a detection section without deteriorating the detection sensitivity.

Another object of the present invention is to provide an infrared detector array comprising an infrared detector capable of controlling the saturation charge.

[0011]

An infrared detector according to the present invention is formed on a semiconductor substrate through which infrared light is transmitted, and on a surface of the semiconductor substrate opposite to the infrared light incident side, and absorbs infrared light to perform photoelectric conversion. A light-absorbing film, a reflecting film that reflects infrared light transmitted through the light-absorbing film and makes the light incident on the light-absorbing film again, and a signal charge that is formed between the light-absorbing film and the reflective film and photoelectrically converted. An infrared detector configured to include an insulating film that accumulates the light, and an infrared detector that photoelectrically converts infrared light incident from the back surface of the semiconductor substrate with the light absorbing film and detects the infrared light. A second charge storage means comprising a formed second insulating film and a conductive film covering the second insulating film is provided. As described above, the second insulating film and the conductive film are provided over the reflective film, and the region sandwiched between the second insulating film and the conductive film is used as the second capacitor portion. The capacitance can be changed without changing the area, and the saturation charge amount can be controlled. That is, it is possible to control the saturated charge amount of the detection unit of the infrared detector without lowering the detection sensitivity.

In the infrared detector according to the present invention, the capacitance of the capacitance portion is controlled by adjusting the thickness of the second insulating film and / or the area of the conductive film without lowering the detection sensitivity. In addition, the saturated charge amount of the detection unit of the infrared detector can be set to an optimum value.

In the infrared detector according to the present invention, the conductive film can be provided with a function as a reflective film. This is caused when the wiring portion for transferring signal charges and the reflective film are formed on the insulating film using the same material. It can be configured to reflect infrared light passing through the margin. In conventional infrared detectors, if the wiring part and the reflection film are formed on the same insulating film, a margin is required between the wiring part and the reflection film, and the area of the reflection film is limited. It is not possible to cover the entire upper part of the film, and it is not possible to reflect all the infrared light transmitted through the light absorbing film, resulting in a decrease in detection sensitivity. However, by forming the conductive film using a material that reflects infrared light as in the present invention, infrared light that cannot be reflected by the reflective film is reflected by the conductive film and enters the light absorbing film, so that the detection sensitivity is reduced. In addition, the wiring portion and the reflection film can be formed on the same insulating film. Such a structure
Since the wiring portion and the reflection film can be formed in the same process, the manufacture of the infrared detector can be facilitated.

The infrared detectors of the present invention may be arranged one-dimensionally or two-dimensionally and used as an infrared detector array.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a plan view when the infrared detector 21 of the present invention is used as a detection unit of an infrared solid-state imaging device. Each infrared detector 21 has a detection area 23 for detecting infrared rays, a transfer gate 2, and a vertical shift register 3. And a wiring section 4. In the detection area 23, the infrared rays are converted into signal charges, transferred to the vertical shift register 3 via the transfer gate 2, and the signal charges are transferred to the horizontal shift register 5 and output from the output amplifier 6. Has become.

As shown in FIG. 2 which is a sectional view taken along the line II-II of FIG. 2 and FIG. 3 which is a sectional view taken along the line III-III of FIG. A detector 23 including a light absorbing film 8, a first insulating film 9, and a light reflecting film 10, a transfer gate 2, a vertical shift register 3, a guard ring 11, and an element isolation oxide film 1
2, a charge transfer section 24 having a P ⁺ stop layer 13 and an interlayer insulating film 14. The charge transfer section 24 is, for example, two-dimensionally arranged on the semiconductor substrate 7 and used as an infrared detector array. In the present invention, in the detection unit 23, a second insulating film 16 is formed on the light reflecting film 10 and a conductive film 15 is formed on the second insulating film 16 corresponding to the light reflecting film 10. Are grounded to form second charge storage means.

The light absorbing film 8 is, for example, a PtSi film formed so as to form a Schottky junction with the semiconductor layer 7. At an end of the light absorbing film 8, a guard ring 11 for relaxing an electric field around the light absorbing film 8 is formed. Furthermore, the semiconductor substrate 7 is electrically separated from the periphery of the light absorbing film 8.
An element isolation oxide film 12 is formed thereon, and an interlayer insulating film 1 is formed on the element oxide isolation film 12 via a P ⁺ stop layer 13.
4 are formed.

The transfer gate 2 and the vertical shift register 3 are formed on the element isolation oxide film 12. Further, the transfer gate 2 and the vertical shift register 3 are both covered with an interlayer insulating film 14. The wiring section 4 is buried in the interlayer insulating film 14.

On the insulating film 9, a metallic reflecting film 10 for reflecting infrared rays is formed. For example, the reflection film 10 made of aluminum reflects infrared light that has entered from the back surface of the semiconductor substrate 7 and has passed through the light absorption film 8 to be incident on the light absorption film 8 again. It is arranged to cover. The thickness of the insulating film 9 is set to (wavelength of infrared light to be detected by the infrared detector 21) × (refractive index of a material forming the insulating film) × １ ／. By setting the thickness of the insulating film 9 sandwiched between the light absorbing film 8 and the reflecting film 10 in this manner, infrared light is optically resonated between the light absorbing film 8 and the reflecting film 10, and the infrared detector 21 can be improved in detection sensitivity.

An upper insulating film 16 is formed on the insulating film 9 so as to cover the reflection film 10, and a conductive film 15 is formed on the upper insulating film 16 so as to face the light absorbing film 8. . As described above, the upper insulating film 16 and the conductive film 15 are provided on the reflective film 10, and the second charge storage means is formed by sandwiching the insulating film 9 and the upper insulating film 16 between the light absorbing film 8 and the conductive film 15. The formation of the capacitance portion is a feature of the infrared detector 21 according to the first embodiment. The conductive film 15 serving as an electrode in this capacitance portion is grounded to GND.

Next, the operation of the infrared detector 21 will be described. Infrared rays incident from the back surface of the semiconductor substrate 7 pass through the semiconductor substrate 7 and reach the light absorbing film 8. In addition, the infrared light transmitted through the semiconductor substrate 7 and further transmitted through the light absorbing film 8 is reflected by the reflecting film 10 and reenters the light absorbing film 8. In the light absorbing film 8, infrared light is photoelectrically converted into signal charges,
It is accumulated in the detection region 23 of the infrared detector 21 and lowers the potential of the light absorbing film 8. The signal charges accumulated in the detection region 23 are transferred to the vertical shift register 3 by opening the transfer gate 2, and are sequentially transferred in the vertical direction.
The signal charges transferred in the vertical direction are further output from an output amplifier via a horizontal shift register (not shown). Opening the transfer gate 2 resets the lowered potential of the light absorbing film 8.

The amount of saturation charge in the detection region 23 of the infrared detector 21 depends on the capacitance of the detection region 23. Therefore,
By adjusting the capacitance of the detection area 23, the detection area 2
3 can be controlled. The capacitance of the infrared detector 23 is the capacitance C between the conductive film 15 and the semiconductor substrate 7, the capacitance C _c between the guard ring 11 and the P ⁺ channel stop layer 13, and the capacitance of the semiconductor substrate 7. This is the sum of the capacitance C _g between the P ⁺ channel stop layer 13 and the capacitance C _s of the semiconductor substrate 7. Since most of the capacitance of the detection region 23 is the capacitance C, Detection area 2
In order to control the saturated charge amount of No. 3, the capacitance C may be adjusted.

When the reflecting film 10 is floating, the capacitance C can be adjusted by changing the thickness of the second upper insulating film 16 while keeping the first insulating film as it is.
It does not affect the detection sensitivity.

The capacitance C can be controlled by changing the area of the conductive film 15 without deteriorating the detection sensitivity of the infrared detector 21.

As described above, by changing the thickness of the insulating film 16 or the area of the conductive film 15, the capacitance C is changed to control the capacitance of the detection region 23, and to control the saturation charge of the detection region 23. can do. Therefore, it is not necessary to set the saturation charge amount of the vertical shift register, the horizontal shift register, and the output amplifier so as to correspond to the saturation charge amount of the detection region as in the related art. The saturated charge amounts of the register and the output amplifier can be set in a well-balanced manner.

Although FIG. 1 shows an infrared detector array in which the infrared detectors 21 are arranged two-dimensionally, the present invention is not limited to a two-dimensional array, and the infrared detector 2
It may be an infrared detector array in which ones are arranged one-dimensionally.

Embodiment 2 FIG. Next, with reference to FIGS. 4 and 5, the infrared detector 22 according to the second embodiment of the present invention will be described.
Will be described.

The infrared detector 22 is a modification of the infrared detector 21 described in the first embodiment.
(1) The wiring portion 4a buried between the insulating films 9 is formed on the insulating film using the same material as the light reflecting film 9, and (2) the resulting wiring portion 4a passes between the wiring portion 4a and the light reflecting film 9. Infrared light is applied to the conductive film 15b so that the conductive film 15b has the function of a reflective film.
This is different from the infrared detector 21 in that the infrared detector 21 is disposed so as to cover the entire area immediately above the light absorbing film 6. The semiconductor substrate 7, the light absorbing film 8, the insulating film 9, the guard ring 11, the P ⁺ stop layer 13, and the interlayer insulating film 14 used in the infrared detector 22 are used.
Is the same as in the first embodiment.

Forming the reflection film 10a and the wiring portion 4a on the insulating film 9 with the same material makes the process of manufacturing the reflection film 10a and the process of manufacturing the wiring portion common, and the manufacturing of the infrared detector 22 On the other hand, a margin is required between the reflection film 10a and the wiring portion 4a, and the area where the reflection film 10a can be formed is limited.
Can not be formed so as to cover the entire area immediately above the light-absorbing film 8.
And cannot enter the light absorbing film 8. However, as in the second embodiment, the conductive film 15 b is provided directly above the light absorbing film 8 not covered by the reflective film 10.
Is formed, the infrared rays that have not been reflected by the reflective film 10a are reflected by the conductive film 15a and enter the light absorbing film 8, so that the detection sensitivity of the infrared detector 22 does not decrease.

The thickness of the second insulator film 16a located immediately above the portion of the light absorbing film 8 sandwiched by the guard ring 11 is (wavelength of infrared light to be detected) .times. (Material of the insulating film) (Refraction index) × 1/2. As described above, the detection sensitivity of the infrared detector 22 can be improved by optically resonating the infrared light reflected by the conductive film 15a between the light absorbing film 8 and the conductive film 15a.

As in the first embodiment, the infrared detector 22 controls the capacity of the detection unit 23 of the infrared detector 22 by changing the area of the conductive film 15a.
Can be controlled. As described above, by controlling the saturated charge amount of the detection unit 23 of the infrared detector 22, the vertical shift register, the horizontal shift register, and the output amplifier are controlled so as to correspond to the saturated charge amount of the detection unit 23 as in the related art. Since it is unnecessary to set the saturated charge amount, when designing the infrared detector 22, the saturated charge amounts of the detection unit 23, the vertical shift register 3, the horizontal shift register, and the output amplifier can be set in a well-balanced manner. .

[0032]

According to the infrared detector of the present invention, a second insulating film and a conductive film are provided on a reflective film, and a region sandwiched between the second insulating film and the conductive film is newly formed as a capacitance portion. Thus, the capacitance of the detection unit of the infrared detector can be changed and the saturation charge amount can be controlled without changing the thickness of the first insulating film and the design of the light reflection film. That is, it is possible to control the saturated charge amount of the detection unit of the infrared detector without lowering the detection sensitivity.

In the infrared detector of the present invention, the method for adjusting the thickness of the second insulating film and / or the area of the conductive film is as follows.
The capacitance of the capacitance unit can be controlled as a whole.
Therefore, it is easy to set the saturation charge amount of the detection unit of the infrared detector to an optimum value without lowering the detection sensitivity.

In the infrared detector of the present invention,
The wiring part for transferring signal charges was formed on the insulating film using the same material as the reflective film, and the conductive film was formed using a material that reflects infrared light.Therefore, a margin was required between the wiring part and the reflective film. Although it is not possible to cover the entire area above the light absorbing film with the film, it is possible to reflect infrared light that could not be reflected by the conductive film and make the infrared light incident on the light absorbing film. Therefore, by forming the wiring portion and the reflective film on the same insulating film in the same step, the infrared detector can be easily manufactured and the detection sensitivity of infrared light is not deteriorated.

By arranging the infrared detector of the present invention one-dimensionally or two-dimensionally, an infrared detector array having excellent detection sensitivity can be obtained.

[Brief description of the drawings]

FIG. 1 shows an infrared detector array according to a first embodiment of the present invention.

FIG. 2 shows the infrared detector according to the first embodiment of the present invention, and is a cross-sectional view along the line II-II in FIG.

FIG. 3 is a cross-sectional view of the infrared detector according to the first embodiment of the present invention, taken along line III-III of FIG. 1;

FIG. 4 shows an infrared detector according to a second embodiment of the present invention, and is a cross-sectional view taken along the line II-II of FIG.

FIG. 5 is a cross-sectional view of the infrared detector according to the second embodiment of the present invention, taken along line III-III of FIG. 1;

FIG. 6 shows a cross-sectional view of a conventional infrared detector.

[Explanation of symbols]

2 transfer gate, 4,4a wiring section, 7
Semiconductor substrate, 8 light absorbing film, 9 insulating film, 10
Light reflection film, 15, 15a conductive film, 16 upper insulating film, 21, 22 infrared detector.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4M104 AA01 BB22 CC03 EE05 EE08 FF35 GG05 4M118 AA01 AA02 AB01 BA10 CA06 CA17 CB14 FA06 FA26 FA28 FA33 GA02 GA08 GB03 GB06 GB11 GB15 GB17 5F038 AC02 CA05 CD04 CD14 5F049 MA05 MB05 Q05 RA03 RA06 SS03 SZ16 SZ20 WA01

Claims (4)

[Claims] 1. A semiconductor substrate through which infrared light is transmitted, and a semiconductor substrate formed on a surface of the semiconductor substrate opposite to the infrared incident side,
A light absorbing film that absorbs infrared light and performs photoelectric conversion, a reflecting film that reflects infrared light transmitted through the light absorbing film and makes the light incident on the light absorbing film again, and is formed between the light absorbing film and the reflecting film; And an infrared detecting unit configured to include an insulating film for storing photoelectrically converted signal charges, and an infrared detecting unit that photoelectrically converts and detects infrared light incident from the back surface of the semiconductor substrate with the light absorbing film. An infrared detector, comprising: a second charge storage means including a second insulating film formed on the reflective film and a conductive film covering the second insulating film. 2. The infrared detector according to claim 1, wherein the capacitance of the second charge storage means is adjusted by the thickness of the second insulating film and / or the area of the conductive film. 3. A wiring portion for transferring signal charges is formed on the insulating film with a certain margin using the same material as the reflective film, and the conductive film enters from a back surface of the semiconductor substrate, and The infrared ray detection device according to any one of claims 1 and 2, wherein the infrared ray detection device is configured to reflect infrared light that is not reflected by the reflection film but passes through the margin and enters the light absorption film. vessel. 4. An infrared detector array, wherein the infrared detectors according to claim 1 are arranged one-dimensionally or two-dimensionally.