JPH1079499A - Photodetector and image sensor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain good detection performance of a photodetector for detecting lights at a plurality of wavelength bands and image sensor composed of an array of the photodetectors in various working environments or over wide wavelength bands. SOLUTION: A photodetector comprises on a semiconductor substrate 11 a first detecting unit 15 for detecting a light in a first wavelength band and a second detecting unit 22 for detecting a light in a second wavelength band. This unit 22 is supported with a space S above the first unit 15 and has a reflective film 24 at the side facing the first unit 15, for reflecting at least a part of the light passing through the first unit 15. The photodetectors are disposed in a line or on plane to form an image-pickup part, and an image reader is attached to it for constituting an image sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light receiving element for receiving a plurality of wavelength bands and an image sensor having a plurality of the light receiving elements arranged. In particular, the structural difference between the conventional light receiving element and the image sensor is that two light receiving sections are vertically arranged with a gap therebetween.

[0002]

2. Description of the Related Art In recent years, the development of optical sensor technology has been remarkable, and various light receiving elements have been developed.

For example, a bolometer or other thermal infrared sensor is generally known as a light receiving element for detecting infrared light. As one type of such thermal infrared sensor,
There is known a Schottky barrier thermistor in which a Schottky barrier diode is formed in a light receiving section and electrically detects a reverse saturation current that changes according to the temperature of the junction (Japanese Patent Application Laid-Open No. 5-40064).

As a light receiving element for detecting infrared rays in the 3 to 5 μm band by photoelectric conversion, a light receiving element in which a PtSi Schottky barrier diode is formed in a light receiving section is known (Television Society Journal Vol. 49, No. 2, No. 2). pp2
19-224, 1995). On the other hand, photodiodes and phototransistors are generally known as light receiving elements for detecting visible light of 1 μm or less.

There is also known an image sensor which arranges these light receiving elements in a linear or planar manner to capture an optical image.

[0006]

By the way, a light receiving element or an image sensor for detecting visible light of 1 μm or less clearly detects light from an object under sunlight, illumination light or other bright illumination. be able to.

However, in a completely dark environment without illumination light or spontaneous light emission, the light receiving element for visible light cannot detect an object at all. Further, a light receiving element or an image sensor that detects infrared rays in the 3 to 8 μm band can detect infrared rays emitted from an object near normal temperature even in a completely dark environment. However, when white light, such as sunlight or headlights, is irradiated near the object, strong near-infrared ambient light is generated, making it difficult to clearly detect the object near room temperature.

Further, a light receiving element or an image sensor that detects infrared rays in the 8 to 12 μm band can also detect infrared rays emitted from an object near normal temperature in a completely dark environment. However, when the amount of raindrops in the atmosphere increases, 8-12
Since the infrared rays in the μm band are attenuated, the S / N is reduced, and the object cannot be clearly detected. As described above, the conventional light receiving element and image sensor are suitable for use in detecting light in a specific wavelength band under a specific environment.

However, as described above, these light-receiving elements have a problem in that once the use environment or the wavelength band changes, sufficient detection performance cannot be obtained. Therefore, there is a demand for a light receiving element that can obtain sufficient detection performance over various use environments and a wide wavelength band. In view of the above, an object of the present invention is to provide a light receiving element capable of obtaining good detection performance over various use environments and a wide range of wavelength bands in order to solve the above problems. I do.

Another object of the present invention is to provide a light receiving element in which the degree of discrimination of a light receiving band in a second light receiving section (described later) is enhanced, in addition to the object of the first aspect.
According to the invention described in claim 3, in addition to the object of claim 2,
It is an object of the present invention to provide a light receiving element that can increase the light receiving efficiency of a first light receiving unit (described later). According to a fourth aspect of the present invention, in addition to the third aspect, it is an object of the present invention to provide a light receiving element capable of further improving the light receiving efficiency of the first light receiving section.

A fifth object of the present invention is to provide a light receiving element in which the degree of discrimination of a light receiving band in a first light receiving section is enhanced, in addition to the object of the first aspect. Claim 6
Another object of the present invention is to provide a light receiving element capable of improving the light receiving efficiency of the second light receiving section, in addition to the object of claim 5. An object of the present invention is to provide a light receiving element capable of further improving the light receiving efficiency of the second light receiving section.

According to the invention of claim 8, in addition to the object of claim 1, a light receiving device capable of accurately detecting a target object irrespective of the influence of strong near-infrared ambient light or raindrops in the atmosphere. It is intended to provide an element. According to a ninth aspect of the present invention, in addition to the object of the first aspect, it is an object of the present invention to provide a light receiving element capable of accurately detecting an object in either a bright environment or a dark environment. I do.

An object of the present invention is to provide a light receiving element capable of selectively taking out detection outputs of two light receiving portions, in addition to the object of the first aspect. According to an eleventh aspect of the present invention, in addition to the object of the first aspect, it is an object of the present invention to provide a light receiving element capable of mixing and outputting detection outputs of two light receiving units. According to a twelfth aspect of the invention, an object is to provide an image sensor using the light receiving element according to any one of the first to twelfth aspects.

[0014]

According to a first aspect of the present invention, there is provided a first light receiving portion formed on a semiconductor substrate for detecting light in a first wavelength band, and a first light receiving portion provided above the first light receiving portion. A second light receiving unit that is supported with a gap therebetween and detects light in the second wavelength band. According to a second aspect of the present invention, in the light receiving element according to the first aspect, the first light receiving portion partially or partially emits light of the first wavelength band out of light incident from the back surface side of the semiconductor substrate. The second light receiving section detects the light in the second wavelength band out of the light transmitted through the first light receiving section. Note that the second light receiving unit is
The light of the first wavelength band transmitted through the first light receiving unit may be absorbed together with the light of the second wavelength band.

According to a third aspect of the present invention, in the light receiving element according to the second aspect, the second light receiving section is provided on a side opposed to the first light receiving section with a light transmitted through the first light receiving section. It comprises a reflective film that reflects at least a part thereof.

According to a fourth aspect of the present invention, in the light receiving element according to the third aspect, the distance between the reflection film and the first light receiving portion is set to n / 4 times the wavelength in the first wavelength band (where n is Odd number)
And According to a fifth aspect of the present invention, in the light receiving element according to the first aspect, the second light receiving unit partially or partially emits light of the second wavelength band out of light incident from the front surface side of the semiconductor substrate. The first light receiving unit detects the light of the first wavelength band out of the light transmitted through the second light receiving unit, by absorbing all the light. Note that the first light receiving unit may absorb the light of the second wavelength band transmitted through the second light receiving unit together with the light of the first wavelength band.

According to a sixth aspect of the present invention, in the light receiving element according to the fifth aspect, the first light receiving portion is provided on a side opposed to the second light receiving portion with a light transmitted through the second light receiving portion. It comprises a reflective film that reflects at least a part thereof. According to a seventh aspect of the present invention, in the light receiving element according to the sixth aspect, an interval between the reflection film and the second light receiving unit is set to n / 4 times (n is an odd number) of a wavelength in the second wavelength band. I do.

According to an eighth aspect of the present invention, in the light receiving element according to any one of the first to seventh aspects, the first
Is constituted by a Schottky barrier diode that photoelectrically converts infrared light of less than 8 μm, and the second light receiving unit is a thermal infrared sensor that detects infrared light by converting it to thermal energy. The invention according to claim 9 is
The light receiving element according to any one of claims 5 to 7, wherein the first light receiving section is a photoelectric conversion element for performing photoelectric conversion of visible light, and the second light receiving section is configured to convert infrared rays into heat energy. It is characterized by being a thermal infrared sensor that converts and detects.

According to a tenth aspect of the present invention, there is provided a light-receiving element according to any one of the first to ninth aspects, wherein the charge readout diffusion is formed on a semiconductor substrate and electrically connected to an output side. A first transfer gate disposed between the layer, a diffusion layer electrically connected to the first light receiving unit, and a charge readout diffusion layer, and controlling a channel;
A second transfer gate is provided between the diffusion layer electrically connected to the second light receiving section and the charge readout diffusion layer and controls a channel.

According to an eleventh aspect of the present invention, in the light receiving element according to any one of the first to ninth aspects, the charge readout diffusion formed on the semiconductor substrate and electrically connected to the output side. A layer, a charge mixing diffusion layer electrically connected to the first light receiving unit and the second light receiving unit, and mixing the charges accumulated from both layers; and a charge reading diffusion layer and a charge mixing diffusion layer. And a transfer gate for controlling a channel.

According to a twelfth aspect of the present invention, there is provided an image pickup unit having a plurality of light receiving elements according to any one of the first to eleventh arrangements linearly or in a plane, and a plurality of light receiving elements. The image sensor includes an image reading unit that sequentially reads out the detected charges in pixel units by a charge transfer method or an XY address method.

(Function) The light receiving element according to claim 1 is
Two light receiving portions are formed vertically above and below the gap.

Generally, a light receiving portion formed on a semiconductor substrate has a small thickness, and thus partially transmits light. Therefore,
Light transmitted through one of the light receiving sections can be detected by the other light receiving section. In addition, the two light receiving units do not completely match the wavelength band of the light to be detected. Therefore, as compared with a light receiving element having only one light receiving portion, it can cover various use environments and a wide wavelength band, and can obtain good detection performance.

Further, since two light receiving sections are stacked,
The degree of integration can be significantly increased as compared with the case where two light receiving sections are juxtaposed. The light receiving element according to the second aspect receives light incident from the back side of the semiconductor substrate.

First, the light incident from the back reaches the first light receiving section. The first light receiving unit converts light in the first wavelength band into energy such as electric energy or heat energy and detects the energy. Therefore, at least a part of the light in the first wavelength band undergoes energy conversion and is absorbed by the first light receiving unit.

The second light receiving section receives the light transmitted through the first light receiving section. Therefore, the first light receiving unit functions as an optical filter that partially absorbs the light of the first wavelength band with respect to the second light receiving unit. Therefore, in the second light receiving unit,
The arriving light is discriminated to some extent, and the discrimination degree of the light receiving band is increased.

In the light receiving element according to the third aspect, the light transmitted through the first light receiving section reaches the reflection film of the second light receiving section. The reflective film reflects at least a part of the light and returns the light to the first light receiving unit side. Therefore, the light receiving efficiency of the first light receiving section is improved. In the light receiving element according to the fourth aspect, the distance between the reflection film and the first light receiving section is set to n / 4 times (n is an odd number) of the wavelength in the first wavelength band.

When the interval length is set in this manner, the first light receiving section efficiently receives light in the first wavelength band due to an optical resonance effect generated between the reflection film and the first light receiving section. be able to. In the light receiving element according to the fifth aspect, light is incident from the front side of the semiconductor substrate. Such light first reaches the second light receiving unit. The second light receiving unit converts the light of the second wavelength band into energy such as electric energy or heat energy and detects the energy.

Therefore, at least part of the light in the second wavelength band is converted into energy and absorbed by the second light receiving portion. The first light receiving unit receives the light transmitted through the second light receiving unit. Therefore, the second light receiving unit functions as an optical filter that partially absorbs light in the second wavelength band with respect to the first light receiving unit.

Therefore, the first light receiving portion discriminates the light reaching to some extent, and increases the discrimination degree of the light receiving band. In the light receiving element according to the sixth aspect, the light transmitted through the second light receiving section reaches the reflection film of the first light receiving section. The reflection film reflects at least a part of the light and returns the light to the second light receiving unit side. Therefore, the light receiving efficiency of the second light receiving section is improved.

In the light receiving element according to the seventh aspect, the interval between the reflection film and the second light receiving section is set to n / 4 times (n is an odd number) of the wavelength in the second wavelength band. When the interval length is set in this manner, the second light receiving unit can efficiently receive light in the second wavelength band due to an optical resonance effect generated between the reflection film and the second light receiving unit. .

The light receiving element according to the eighth aspect can clearly detect an object as described below, regardless of the influence of strong near-infrared ambient light or raindrops in the atmosphere. That is, in an environment in which sunlight, white light, or the like is radiated near an object, near-infrared ambient light is strongly generated. Such near-infrared ambient light enters from the back side of the semiconductor substrate together with light from the object, and first reaches the first light receiving unit.

The first light receiving section is a Schottky barrier diode (for example, a P-type) for photoelectrically converting infrared light of less than 8 μm.
tSi Schottky barrier diode). Such a first light receiving section is a near infrared ray (wavelength 8 μm
) Is absorbed exclusively through photoelectric conversion. On the other hand, far-infrared rays (wavelength 8 μm or more) generated from an object near normal temperature
Since the light has low light energy, the excited electrons cannot pass through the Schottky barrier and pass through the first light receiving portion as it is.

For this reason, the second light receiving section mainly receives light of far-infrared rays (wavelength of 8 μm or more) generated from an object near normal temperature. Therefore, the second light receiving unit is not strongly affected by the near-infrared peripheral light, and can clearly detect far-infrared rays from the target object. On the other hand, as the amount of raindrops in the atmosphere increases, the infrared rays transmitted through the atmosphere attenuate. For example,
Assuming that the equivalent moisture thickness per 1 km of the atmosphere is 200 mm, the transmittance of infrared rays is as shown in the table below (Haruyoshi Kuno, "Infrared Engineering" (1994) pp. 58-61).

[0035] As shown in the above data, the wavelength band around 4 μm detected by the first light receiving unit has a particularly high transmittance in the atmosphere under the condition of rain or fog.

Therefore, regardless of the influence of raindrops in the atmosphere, the first light receiving section can detect infrared rays having a wavelength of about 4 μm emitted from an object near normal temperature at a high S / N. In the light receiving element according to the ninth aspect, the object can be accurately detected in a bright environment or a dark environment as described below.

That is, in a bright environment, visible light and infrared light first reach the second light receiving section. Since the second light receiving section is constituted by a thermal infrared sensor, the second light receiving section converts infrared rays into thermal energy and absorbs the thermal energy.

As described above, the second light receiving section functions as an infrared cut filter, and reduces infrared rays reaching the first light receiving section. Therefore, the photoelectric conversion element, which is the first light receiving section, receives mainly the visible light projected from the object and can clearly detect the object. On the other hand, in a dark environment, the second light receiving unit can detect infrared rays emitted from an object near normal temperature and accurately detect the object.

In the light receiving element according to the tenth aspect, the first
Opening the channel through the transfer gate of
And the charge readout diffusion layer are electrically connected.
In this state, the output of the first light receiving unit can be read from the charge read diffusion layer. When the channel is opened via the second transfer gate, the second light receiving portion and the charge readout diffusion layer are electrically connected. In this state, the output of the second light receiving section can be read from the charge read diffusion layer.

Further, when both channels are opened via the first and second transfer gates, the first and second transfer gates are opened.
And the charge readout diffusion layer are electrically connected. In this state, the outputs of the first and second light receiving units can be mixed and read by the charge readout diffusion layer. Claim 1
In the light receiving element according to 1, the charge accumulated from the first and second light receiving portions is mixed in the charge mixing diffusion layer.

When the channel is opened via the transfer gate, charges in the charge mixed diffusion layer are read from the charge read diffusion layer. In the image sensor according to the twelfth aspect, each light receiving element accumulates electric charge in pixel units according to the luminance distribution of the imaging unit. The image readout unit sequentially reads out the charges in pixel units by a charge transfer method or an XY address method, and outputs them as image signals.

[0042]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 shows a first embodiment (Claim 1).
FIG. 4 is a diagram showing a light receiving cell of an image sensor corresponding to 〜4, 8, 10, and 12).

In FIG. 1, a 3-5 μm band and 8-12
Antireflection film 12 for increasing the transmittance of infrared rays in the μm band
Is formed, and the image sensor is connected to the light receiving cell 1 on the front side.
A P ⁺ separation layer 13 for patterning every 0 is patterned. A guard ring 14, which is an N diffusion layer, is formed in a ring shape within the section of the P ⁺ separation layer 13, and a PtSi Schottky barrier diode (hereinafter, referred to as “PtSi-SBD”) 15 is formed in the ring. It is formed.

A transfer gate 16a is arranged adjacent to the guard ring 14, and an electrode X1 for selecting a light receiving band is electrically connected to the transfer gate 16a. Note that the PtSi-SBD is provided at a portion adjacent to the guard ring 14 and the transfer gate 16a.
An N ⁺ diffusion layer 14a for reducing the contact resistance between the gate ring 15 and the guard ring 14 is embedded.

On the other side of the transfer gate 16a, a charge readout diffusion layer 17 made of an N ⁺ diffusion layer is arranged, and the charge readout electrode 17 is electrically connected to the charge readout diffusion layer 17. . Charge read diffusion layer 17
The transfer gate 16b and the diffusion layer 1
8 are arranged in order, and an electrode X2 for selecting a light receiving band is electrically connected to the transfer gate 16b.

On the other hand, above the PtSi-SBD 15,
The bridge structure 20 is formed with the gap S interposed therebetween. The bridge structure 20 is supported by a bridge-like support (not shown) made of a silicon nitride film or the like.

On this support, a Schottky barrier thermistor 22 which is a thermal infrared sensor and a heat absorbing film 2
3 are formed in layers. One terminal of the Schottky barrier thermistor 22 is connected to a bias power supply 25 for applying a reverse bias via wiring on the pier 21 of the support. The other terminal is connected to the diffusion layer 18 via a wiring on the pier 21 of the support.

On the back side of the Schottky barrier thermistor 22, a reflection film 24 made of a metal thin film is formed. The distance between the reflection film 24 and the PtSi-SBD 15 is 3/4.
It is set to about 程度 μm. Here, such a crosslinked structure 20 is formed, for example, as follows. First,
A sacrificial layer is formed on the PtSi-SBD 15, and a crosslinked structure 20 is sequentially formed on the sacrificial layer. Finally, by removing the sacrificial layer, the bridge structure 20 is lifted from above the semiconductor substrate 11.

FIG. 2 is a diagram showing the configuration of an XY address type image sensor. In FIG. 2, the imaging unit 31
, A plurality of the light receiving cells 10 (FIG. 1) described above are arranged in a plane. The electrodes X1, X of the light receiving cells 10 arranged in the vertical direction
2 are collectively connected to each terminal of the horizontal scanning signal generator 32, and the horizontal scanning signal generator 32 is connected to the light receiving band selector 33.

On the other hand, the electrodes Y of the light receiving cells 10 arranged in the horizontal direction are collectively connected to each drain terminal of the output switch group 35. The gate terminals of the output switch group 35 are connected to the respective terminals of the vertical scanning signal generator 34, and the source terminals of the output switch group 35 are collectively connected to become output terminals for image signals. In addition, regarding the correspondence relationship between the first and second aspects of the invention and the first embodiment, the first light receiving unit is a PtS
The second light receiving section corresponds to the Schottky barrier thermistor 22 corresponding to the i-SBD 15.

Regarding the correspondence between the third and fourth aspects of the present invention and the first embodiment, the reflection film corresponds to the reflection film 24. Regarding the correspondence between the invention described in claim 8 and the first embodiment, the Schottky barrier diode is Pt
The thermal infrared sensor corresponds to the Schottky barrier thermistor 22 corresponding to the Si-SBD 15.

As to the correspondence between the invention described in claim 10 and the first embodiment, the charge readout diffusion layer corresponds to the charge readout diffusion layer 17, the first transfer gate corresponds to the transfer gate 16a, The second transfer gate corresponds to the transfer gate 16b. Regarding the correspondence between the invention described in claim 12 and the first embodiment, the imaging unit corresponds to the imaging unit 31, and the image reading unit is the horizontal scanning signal generation unit 32 and the vertical scanning signal generation unit 3.
4, corresponding to the output switch group 35.

FIG. 3 is an exploded perspective view for explaining the operation of the first embodiment. Hereinafter, the operation of the first embodiment will be described with reference to these drawings. First, when light is applied to the back side of the semiconductor substrate 11, the light passes through the anti-reflection film 12,
Light reaches the PtSi-SBD 15. PtSi-SB
D15 absorbs infrared rays (A in FIG. 1) in the 3 to 5 μm band and performs photoelectric conversion. However, the thickness of the PtSi film is 50
Since it is very thin, ie, less than Å, a part of the infrared ray in the 3 to 5 μm band (B in FIG. 1) is transmitted without being absorbed by the PtSi-SBD 15 and reflected by the ultra-thin reflective film 24, and is reflected by the PtSi-S
It is led to BD15 again.

Here, the reflection film 24 and the PtSi-SBD1
5 is set to about 3/4 to 5/4 [mu] m, so that the infrared radiation in the 3 to 5 [mu] m band becomes P due to the optical resonance effect.
It is efficiently absorbed by tSi-SBD15. Note that Pt
Guard ring 14 arranged on the periphery of Si-SBD 15
Reduces the electric field concentration at the edge of the PtSi-SBD 15 and accumulates charges generated by photoelectric conversion.

On the other hand, infrared rays (C in FIG. 1) in the band of 8 to 12 μm incident from the back side of the semiconductor substrate 11 are PtS
Instead of being absorbed by the i-SBD 15, it is mainly absorbed by the heat absorbing film 23 and is converted into thermal energy. Here, since the crosslinked structure 20 is formed, the heat absorption film 23 and the semiconductor substrate 11 are effectively insulated. Therefore, the heat capacity of the crosslinked structure 20 is small, and a temperature change sensitive to weak infrared rays occurs.

Due to such a temperature change, the value of the reverse saturation current of the Schottky barrier thermistor 22 changes, and the amount of charge stored in the diffusion layer 18 changes. When a voltage is applied to either of the electrodes X1 and X2 in this state, PtSi
-SBD15 or Schottky barrier thermistor 2
2 can be read out to the electrode Y side.

When a voltage is applied to both the electrodes X1 and X2, the signal charges of both the PtSi-SBD 15 and the Schottky barrier thermistor 22 can be mixed and read out from the electrode Y side. Actually, as shown in FIG. 2, the scanning pulses are sequentially applied via the horizontal scanning signal generator 32 and the vertical scanning signal generator. By applying such a scanning pulse, signal charges are read out by the XY address method.

According to the operation described above, in the first embodiment, since two types of light receiving sections are provided, it is possible to reliably cover various use environments and a wide wavelength band, and obtain good detection performance. . That is, when the near-infrared (less than 8 μm) ambient light is strongly generated by sunlight, white light, or the like, the PtSi-SBD 15 absorbs such ambient light. Therefore, the Schottky barrier thermistor 22
Can clearly detect light of far infrared rays (wavelength of 8 μm or more) generated from an object near normal temperature without being disturbed by ambient light.

On the other hand, when the amount of raindrops in the atmosphere increases, 8 to 12
Far infrared rays of about μm are greatly attenuated. However, 4 μm
Near-infrared rays in the vicinity do not attenuate much, and PtSi-SBD
Reach 15 Therefore, irrespective of the influence of raindrops in the atmosphere, the PtSi-SBD 15 can detect infrared rays with a wavelength of around 4 μm emitted from an object near normal temperature at a high S / N.

Further, since the two imaging planes are arranged in an overlapping manner, there is no need to arrange an imaging optical system for each imaging plane.
The size of the entire device can be reduced. Further, since the light receiving portions are stacked in the upper and lower two layers, the degree of integration of the light receiving cells 10 can be remarkably increased as compared with the case where two light receiving portions are arranged in the same plane. Therefore, an image sensor having excellent spatial resolution can be realized.

The reflection film 24 and the PtSi-SBD 15
Is set to 3/4 to 5/4 [mu] m, the PtSi-SBD 15 is 3 to 5 due to the optical resonance effect.
Infrared light in the μm band can be efficiently received. Further, by performing the voltage operation of the electrodes X1 and X2, the outputs of the two light receiving units can be appropriately read.

Next, another embodiment will be described. (Second Embodiment) FIG. 4 is a diagram showing a light receiving cell of an image sensor according to a second embodiment (corresponding to claims 1, 5 to 7, 9, 10, and 12). The structural features of the second embodiment are as follows: (1) Guard ring 14 and P
A photodiode 44 is arranged instead of the tSi-SBD 15, and (2) the light absorption film 4 is used instead of the antireflection film 12.
2 and (3) the reflection film 45 is disposed on the upper surface of the photodiode 44 instead of the reflection film 24, and the interval between the reflection film 45 and the heat absorption film 23 is set to 8/4 to 12/4 μm. Is a point.

The same components as those shown in FIG. 1 are denoted by the same reference numerals and are shown in FIG. 4, and the description thereof will not be repeated. The correspondence between the inventions described in claims 1 and 2 and the second embodiment is described in the first embodiment.
The light receiving portion corresponds to the photodiode 44, and the second light receiving portion corresponds to the Schottky barrier thermistor 22.

As for the correspondence between the invention described in claims 6 and 7 and the second embodiment, the reflection film corresponds to the reflection film 45. Regarding the correspondence between the invention described in claim 9 and the second embodiment, the photoelectric conversion element corresponds to the photodiode 44, and the thermal infrared sensor corresponds to the Schottky barrier thermistor 22.

As for the correspondence between the invention described in claim 10 and the second embodiment, the charge readout diffusion layer corresponds to the charge readout diffusion layer 17, the first transfer gate corresponds to the transfer gate 16a, The second transfer gate corresponds to the transfer gate 16b. Hereinafter, the operation of the second embodiment will be described.

First, when light is irradiated from the front side of the semiconductor substrate 11, infrared rays in the 8 to 12 μm band (A in FIG. 4) reach the heat absorbing film 23 and are converted into thermal energy.
However, since the thickness of the Schottky barrier thermistor 22 and the like is very thin, about 1000 °, a part of the infrared rays in the 8 to 12 μm band (B in FIG. 4) is transmitted as it is, reflected by the reflective film 45, and It is led to the absorbing film 23 again.

Here, the distance d between the heat absorption film 23 and the reflection film 45 is set to about 8/4 to 12/4 μm.
The infrared rays in the band of 8 to 12 μm are efficiently absorbed by the heat absorbing film 23 due to the optical resonance effect.

The change in the temperature of the heat absorbing film 23 changes the value of the reverse saturation current of the Schottky barrier thermistor 22,
The amount of charge stored in the diffusion layer 18 changes. On the other hand, most of the visible light (C in FIG. 4) incident from the front side of the semiconductor substrate 11 passes through the heat absorption film 23 and the reflection film 45 and reaches the photodiode 44. Photodiode 4
Numeral 4 photoelectrically converts visible light and accumulates electric charges.

Since the light transmitted through the photodiode 44 is absorbed by the light absorbing film 42, the generation of stray light is prevented, and there is no fear that the image quality is degraded. In this state, the electrode X
By appropriately applying a voltage to 1 and X2, the signal charges of the two light receiving units can be read out to the electrode Y side. According to the operation described above, in the second embodiment, since two types of light receiving units are provided, it is possible to cover various use environments and a wide range of wavelength bands, and obtain good detection performance.

That is, in a bright environment, the heat absorbing film 23
Functions as an infrared cut filter and reduces infrared rays reaching the photodiode 44. For this reason, the first light receiving unit can capture a clear image of the target object without being disturbed by the infrared light. On the other hand, in a dark environment, the Schottky barrier thermistor 22 detects infrared rays emitted from an object near normal temperature and can clearly image the object.

Further, since the two imaging planes are arranged in an overlapping manner, there is no need to arrange an imaging optical system for each imaging plane.
The size of the entire device can be reduced. Further, since the light receiving portions are stacked in the upper and lower two layers, the degree of integration of the light receiving cells 10 can be remarkably increased as compared with the case where two light receiving portions are arranged in the same plane. Therefore, an image sensor having excellent spatial resolution can be realized.

Since the distance between the reflection film 45 and the heat absorption film 23 is set to 8/4 to 12/4 μm, the heat absorption film 23 emits infrared rays in the 8 to 12 μm band due to the optical resonance effect. Light can be received efficiently. In the above-described embodiment, the case where the signal charges are selectively read from the two light receiving units has been described. However, the present invention is not limited to this configuration. For example, as shown in FIG. 5, the signal charges from the two light receiving sections may be mixed in advance in the charge mixing diffusion layer 54a, and the mixed signal charges may be read. With such a configuration, an image sensor having a wide light receiving band can be easily realized.

In the above-described embodiment, the signal charges are read out in pixel units by the XY address method, but the present invention is not limited to this configuration. For example, a CCD may be configured by providing a transfer electrode on the charge readout diffusion layer 17. In such a configuration, signal charges can be read by a charge transfer method. Furthermore, in the above-described embodiment, the Schottky barrier thermistor 22 is employed as the thermal infrared sensor, but the present invention is not limited to this configuration. For example, a PN junction diode, bolometer, pyroelectric sensor, thermocouple, or other thermal infrared sensor may be used.

In the first embodiment, PtSi—S
Although the BD 15 is employed as the first light receiving unit, the configuration is not limited to this. For example, other metals,
A Schottky barrier diode combined with a metal silicide may be employed. By thus changing the combination of the bonding portions, infrared light having a wavelength of about 8 μm can be detected.

Further, in the above-described embodiment, the first light receiving section is constituted by the photoelectric conversion element, but the invention is not limited to this constitution. For example, it may be constituted by a thermal infrared sensor. In this configuration, it is particularly preferable to adopt a heat insulating structure such as providing a gap in a substrate below the first light receiving unit in order to thermally isolate the first light receiving unit from the semiconductor substrate. As described above, by using the thermal infrared sensor for the first and second light receiving units, it is possible to eliminate the need for a cooling device required for the photoelectric conversion infrared sensor.

In the above-described embodiment, the air gap is provided to form the heat insulating structure. For example, a light transmissive material having excellent heat insulating properties may be disposed in part or all of the air gap. Good (this is one in which a light transmitting material is added as a component to the present invention). Such a configuration has the effect of increasing the mechanical strength of the heat insulating structure.

[0077]

As described above, the light-receiving element according to the first aspect has two types of light-receiving sections, so that it can cover various use environments and a wide wavelength band without fail, and has good detection performance. Obtainable. Therefore, the conventional problem that even the presence of an object cannot be detected depending on a change in environment is solved.

Further, since the second light receiving section is arranged above the semiconductor substrate with a gap therebetween, the heat receiving property is high and the heat capacity is small. Therefore, the rate of temperature change due to infrared rays increases, and weak infrared rays can be detected with high sensitivity. Further, since the two light receiving sections are vertically stacked,
The degree of integration of the semiconductor element can be increased as compared with the case where two light receiving sections are juxtaposed in the same plane.

In general, when two light receiving units are juxtaposed, it is necessary to arrange a condensing optical system for each of the light receiving units, or separately provide a dedicated prism for branching the optical path. However, the light receiving element according to the first aspect of the present invention has the light receiving section stacked vertically, so that only one optical system needs to be provided, and the mounting space occupied by the optical system can be significantly reduced.

In the light receiving element according to the second aspect, the first light receiving portion functions as an optical filter that absorbs light in the first wavelength band, so that light reaching the second light receiving portion is discriminated in advance. The degree of discrimination of the light receiving band in the second light receiving unit can be increased. In the light receiving element according to the third aspect, since the reflection film returns the light to the first light receiving unit side, the light receiving efficiency in the first light receiving unit can be increased.

In the light receiving element according to the fourth aspect, the interval between the reflection film and the first light receiving portion is set to n / 4 times (n is an odd number) of the wavelength in the first wavelength band, so that the optical Due to the mechanical resonance effect, the first light receiving unit can efficiently receive light in the first wavelength band. In the light receiving element according to the fifth aspect, since the second light receiving section functions as an optical filter that absorbs light in the second wavelength band, the light reaching the first light receiving section is discriminated, and the first light receiving section is separated from the first light receiving section. The degree of discrimination of the light receiving band in the light receiving section can be increased.

In the light receiving element according to the sixth aspect, since the reflection film returns the light to the second light receiving section side, the light receiving efficiency in the second light receiving section can be improved. In the light receiving element according to the seventh aspect, the distance between the reflective film and the second light receiving unit is equal to or less than the second distance.
Is set to n / 4 times (n is an odd number) of the wavelength in the wavelength band of, and the second light receiving unit can efficiently receive the light of the second wavelength band by the optical resonance effect.

In the light receiving element according to the eighth aspect, since the first light receiving portion absorbs near-infrared peripheral light (wavelength less than 8 μm) contained in sunlight or the like, the second light receiving portion receives the peripheral light. It is possible to clearly detect light of far-infrared rays (wavelength of 8 μm or more) generated from an object near normal temperature without being hindered by light. On the other hand, when the amount of raindrops in the atmosphere increases, 8-12
Far infrared rays of about μm are attenuated. However, near-infrared rays near 4 μm do not attenuate and strongly reach the first light receiving unit. Therefore, regardless of the influence of raindrops in the atmosphere, the first light receiving unit can detect, with a high S / N ratio, infrared rays having a wavelength of about 4 μm emitted from an object near normal temperature.

Therefore, in any of the above-mentioned bad environments, infrared rays from the object can be clearly detected. In the light receiving element according to the ninth aspect, in a bright environment, the second light receiving section functions as an infrared cut filter, and reduces infrared rays reaching the first light receiving section. Therefore, the first light receiving unit including the photoelectric conversion element can clearly detect the visible light from the object without being disturbed by the infrared light.

On the other hand, in a dark environment, the second light receiving section
By detecting infrared rays emitted from an object near normal temperature, the object can be accurately detected. Therefore, it is possible to accurately detect the light from the object regardless of the surrounding brightness and the like. In the light receiving element according to claim 10, the first
By operating the second transfer gate and the second transfer gate, the output of the first light receiving unit and the output of the second light receiving unit can be selectively read.

Therefore, it is possible to easily select a light receiving section suitable for a use environment and an object. In the light receiving element according to the eleventh aspect, by operating the transfer gate, the output of the first light receiving unit and the output of the second light receiving unit can be mixed and read. Therefore, a light receiving element having a wide light receiving band can be easily realized by appropriately combining different light receiving units to form a light receiving element.

In the image sensor according to the twelfth aspect,
An image pickup unit is configured by arranging a plurality of light receiving elements according to any one of claims 1 to 11. Therefore, 2
Since an optical image can be captured for one wavelength band, it is possible to reliably cover various use environments and a wide range of wavelength bands, and obtain good imaging performance.

Further, since the two types of light receiving portions are stacked in the vertical direction, the degree of integration of the light receiving cells can be remarkably increased as compared with the case where the two types of light receiving portions are juxtaposed in the same plane. Therefore, an image sensor having excellent spatial resolution can be realized. Generally, when two imaging planes are juxtaposed, it is necessary to arrange an imaging optical system for each imaging plane, or to separately arrange a dedicated prism or the like for splitting an optical path. However, since the image sensor according to the twelfth aspect has an imaging surface stacked vertically, it is sufficient to provide one imaging optical system, and the mounting space occupied by the optical system can be significantly reduced.

[Brief description of the drawings]

FIG. 1 shows a first embodiment (claims 1 to 4, 8, 10, 1).
2 is a diagram showing a light receiving cell of the image sensor (corresponding to 2).

FIG. 2 is a diagram illustrating a configuration of an XY address type image sensor.

FIG. 3 is an exploded perspective view illustrating the operation of the first embodiment.

FIG. 4 shows a second embodiment (claims 1, 5, 7, 9, 1);
FIG. 11 is a diagram showing a light receiving cell of the image sensor corresponding to (0, 12).

FIG. 5 is a view showing a light receiving cell according to claim 11;

[Explanation of symbols]

Reference Signs List 10 light receiving cell 11 semiconductor substrate 12 antireflection film 13 P ⁺ separation layer 14 guard ring 14 a N ⁺ diffusion layer 15 PtSi-SBD 16 a transfer gate 16 b transfer gate 17 charge read diffusion layer 18 diffusion layer 20 bridge structure 21 bridge pier 22 Schottky Barrier thermistor 23 Heat absorption film 24 Reflection film 25 Bias power supply 31 Imaging unit 32 Horizontal scanning signal generation unit 33 Light receiving band selection unit 34 Vertical scanning signal generation unit 35 Output switch group 42 Light absorption film 44 Photodiode 45 Reflection film

Claims (12)

[Claims] A first light receiving portion formed on a semiconductor substrate for detecting light in a first wavelength band; and a second light receiving portion for detecting light in a second wavelength band. 2. The light receiving element according to claim 2, wherein the light receiving section is supported above the first light receiving section with a gap. 2. The light-receiving element according to claim 1, wherein the first light-receiving unit partially or entirely converts the light of the first wavelength band out of the light incident from the back surface side of the semiconductor substrate. A light receiving element, wherein the light is absorbed and detected, and the second light receiving unit detects light in the second wavelength band out of light transmitted through the first light receiving unit. 3. The light receiving element according to claim 2, wherein the second light receiving unit is configured to transmit at least a part of the light transmitted through the first light receiving unit to a side facing the first light receiving unit. A light receiving element comprising a reflection film for reflecting light. 4. The light receiving element according to claim 3, wherein a distance between the reflection film and the first light receiving unit is n / 4 times a wavelength in the first wavelength band (n is an odd number).
A light receiving element characterized by the following. 5. The light-receiving element according to claim 1, wherein the second light-receiving unit partially or entirely converts the light of the second wavelength band out of the light incident from the front surface side of the semiconductor substrate. A light receiving element, wherein the light is absorbed and detected, and the first light receiving unit detects light in the first wavelength band among light transmitted through the second light receiving unit. 6. The light receiving element according to claim 5, wherein the first light receiving unit is configured to transmit at least a part of the light transmitted through the second light receiving unit to a side facing the second light receiving unit. A light receiving element comprising a reflection film for reflecting light. 7. The light receiving element according to claim 6, wherein a distance between the reflection film and the second light receiving unit is n / 4 times a wavelength in the second wavelength band (n is an odd number).
A light receiving element characterized by the following. 8. The light-receiving element according to claim 1, wherein the first light-receiving unit is a Schottky barrier diode that photoelectrically converts infrared light having a wavelength of less than 8 μm. The light-receiving element, wherein the second light-receiving unit is a thermal infrared sensor that converts infrared light into heat energy and detects the heat energy. 9. The light-receiving element according to claim 5, wherein the first light-receiving section is a photoelectric conversion element that performs photoelectric conversion of visible light, and the second light-receiving section. Is a thermal type infrared sensor which detects infrared light by converting it into thermal energy. 10. The light-receiving element according to claim 1, wherein the charge-reading diffusion layer is formed on the semiconductor substrate and is electrically connected to an output side. A diffusion layer electrically connected to the light receiving portion of
A first transfer gate disposed between the charge readout diffusion layer and controlling a channel; a diffusion layer electrically connected to the second light receiving unit;
A second transfer gate disposed between the charge readout diffusion layer and the channel to control a channel; 11. The light-receiving element according to claim 1, wherein the charge-reading diffusion layer is formed on the semiconductor substrate and is electrically connected to an output side. A charge mixing / diffusion layer electrically connected to the light receiving portion and the second light receiving portion, and mixing the charges accumulated from both; a charge mixing / diffusion layer disposed between the charge readout diffusion layer and the charge mixing / diffusion layer And a transfer gate for controlling a channel. 12. The method according to claim 1, wherein
An image pickup unit in which a plurality of light receiving elements are linearly or planarly arranged in an item, and an image reading unit that sequentially reads out charges in pixel units detected by the plurality of light receiving elements by a charge transfer method or an XY address method. An image sensor comprising: