JPH11317510A - Infrared-ray solid-state image-pickup device and infrared-ray light receiving element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an element for the detection of wavelength distribution in an infrared-ray image-pickup device and an infrared-ray light receiving element. SOLUTION: An infrared-ray solid-state image-pickup device is provided with a plurality of photodetecting pixels arranged in a matrix from on a semiconductor substrate for detecting infrared rays for transmitting electric signals, a signal scanning part transfers and outputs the electric signals from the photodetecting pixels, a reflection part which reflects at least a part of the infrared rays from the photodetecting pixel side. With such a constitution, by setting at least exceeding two kinds of optical distances between the photodetecting pixels and the reflection part multiple kinds of optical cavity structures are on formed a semiconductor substrate, so that 'the peaks of the spectral sensitivity developed through the reinforcement of incident light and reflected light' are arranged shifted by several pixel numbers in the photodetectable wavelength region of the photodetecting pixels using the multiple kinds of optical cavity structures.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an infrared solid-state imaging device and an infrared light receiving element having a structure capable of controlling spectral sensitivity in an infrared region. In particular, the present invention relates to an infrared solid-state imaging device and an infrared light receiving element suitable for spectral analysis based on the principle of additive color mixing.

[0002]

2. Description of the Related Art Infrared rays are emitted from an object having a temperature. By imaging the infrared rays from the object using the infrared solid-state imaging device, it is possible to clearly capture the shape and appearance of the object even in dark night. A security system that enables monitoring in the dark by utilizing such features has been put to practical use.

[0003] The amount of infrared radiation emitted from an object increases as the temperature of the object increases. The amount of infrared light at this time is smaller than the amount of infrared light from a black body, which is an ideal heat radiator, and the ratio is generally called “emissivty”.
It is called. If the emissivity of the object to be observed is known, the true temperature of the object can be obtained from the amount of infrared light measured by the infrared solid-state imaging device or the infrared light receiving element. Based on such a principle, an infrared thermometer or the like that measures the temperature of an object in a non-contact manner has been put to practical use.

Further, the presence or absence of a burning substance can be detected by detecting strong infrared radiation from the burning substance using an infrared solid-state imaging device or an infrared light receiving element. By utilizing such features, fire detection systems and the like that detect a fire occurrence quickly over a wide monitoring area have been put to practical use. As described above, the infrared solid-state imaging device and the infrared light receiving element described above are important light receiving devices used for various purposes.

Hereinafter, an example of such an infrared solid-state imaging device will be described. FIG. 11A is a top view illustrating the structure of the infrared solid-state imaging device. FIG. 11 (b) shows A-
It is a figure which shows the cross-section structure of A 'position. In these figures, the main surface of the p-type silicon substrate 81 has P
The PtSi film 8 is deposited, and is subjected to a heat treatment.
2 are formed. By the Schottky junction between the silicide layer composed of the PtSi film 82 and the p-type silicon substrate 81, a photoelectric conversion unit having sensitivity in an infrared region is formed.

Above these PtSi films 82, an insulating film 83 made of silicon oxide (refractive index n = 1.4) is formed. A reflective film 84 made of aluminum or the like is provided on the insulating film 83 to form a kind of optical cavity structure. The geometric distance d between the PtSi film 82 and the reflection film 84 is set to a uniform value (for example, 0.75 μm) for all the light receiving pixels.

On the other hand, a guard ring 86 made of an n-type diffusion layer is provided around the PtSi film 82 in order to suppress a leak current. Such guard ring 86
Next to is a long BCC with a part of the separation area 85
The D diffusion layer 87 is embedded. This BCCD diffusion layer 87
Above this, a CCD transfer electrode 88 for applying a transfer pulse is formed via an insulating film.

In such an element structure, infrared rays are incident from the back side of the p-type silicon substrate 81. After the incident infrared rays pass through the p-type silicon substrate 81, the PtSi film 8
Reach around 2. The infrared light further transmitted through the PtSi film 82 is Fresnel-reflected by the reflection film 84 and becomes reflected infrared light. The reflected infrared rays return to the direction of the PtSi film 82 again. The coincidence of the optical paths of the incident infrared light and the reflected infrared light causes interference between the two infrared lights.

At this time, at the position of the PtSi film 82, a phase difference θ = π + (2nd / λ) × 2π (1) always occurs between the incident infrared ray and the reflected infrared ray. In the equation (1), λ is the wavelength of infrared light, and nd is the optical distance between the PtSi film 82 and the reflection film 84. By such a phase difference θ, Pt
The light intensity of the interference light at the position of the Si film 82 reinforces under the wavelength condition of λ = 4 nd / N [where N = 1, 3, 5,...] (2).

FIG. 12 is a diagram showing the light intensity (calculated value) of the interference light at the position of the PtSi film 82. The light intensity peaks at a wavelength of 4.2 μm corresponding to “N = 1”,
It shows a gradual change. Due to the energy of such interference light, electron-hole pairs are generated in the PtSi film 82. Most of the free holes generated at this time flow over the Schottky barrier and flow into the p-type silicon substrate 81. On the other hand, the same number of free electrons as the free holes advance according to the potential in the depletion region of the guard ring 86 and are accumulated as signal charges. At this time, the remaining carriers that could not cross the Schottky barrier recombine and disappear during the diffusion movement.

In such a photoelectric conversion process, the spectral sensitivity of the infrared solid-state imaging device has the characteristics shown in FIG. In this spectral sensitivity, the original spectral sensitivity characteristic of the PtSi film 82 appears strongly. Therefore, the peak characteristic (peak wavelength 4.2 μm) in FIG. 12 disappears from the spectral sensitivity characteristic shown in FIG. The signal charge thus photoelectrically converted is drawn out to the BCCD diffusion layer 87 by the voltage applied to the CCD transfer electrode 88 also serving as a transfer gate. The BCCD diffusion layer 87 transfers and outputs signal charges to the outside according to a multi-phase transfer pulse applied to the CCD transfer electrode 88.

[0012]

When the temperature is measured using the infrared solid-state imaging device as described above, the numerical value of the emissivity is not always provided for the substance to be observed. If the emissivity is unknown, the user must determine the emissivity experimentally beforehand, which is very troublesome. Therefore, in practice, the emissivity is assumed to be the same value as the emissivity of the black body, such as "1", and the number of measurement cases is extremely large. In such a state of use, accurate measurement of the temperature could not be expected.

On the other hand, in the field of analytical chemistry, it is known that a wavelength distribution of infrared rays changes according to a change in temperature of an object (Planck's distribution law). FIG. 14 is a diagram showing such a wavelength distribution (calculated value) of infrared rays for each temperature of an object. In general, as the temperature of an object increases, the energy ratio of a component having a short wavelength increases. Such a tendency of the wavelength distribution can be regarded as substantially constant regardless of the emissivity of each individual object. Therefore, if the wavelength distribution of infrared rays emitted from an object can be detected, it is possible to accurately determine the temperature of the object even if the emissivity is unknown. Vol. 24, No. 4, "Temperature Estimation Method Based on Extended Power Law of Thermal Radiation").

In addition to such temperature measurement, various and useful analysis operations such as object identification and composition detection can be performed by observing the emission and absorption spectrum of infrared rays. However, in the conventional infrared solid-state imaging device and infrared light receiving element, in order to detect the wavelength distribution as described above, a filter for an infrared region corresponding to a color filter in a visible region is indispensable.

Generally, a filter for the visible region can be easily formed by using a pigment or the like. On the other hand, a filter for the infrared region cannot be formed unless a complicated method such as vapor deposition of several to several tens of special inorganic substances is used. Furthermore, it is very difficult to form such a filter for the infrared region on a light receiving pixel as small as about 250 μm ² .

In particular, in the case of a back-illuminated type element as described in the conventional example, a thick silicon wafer is interposed between the light receiving pixel and the filter. Therefore, individual light receiving pixels and filters are far apart, and it is very difficult to properly arrange filters in accordance with the positions of the light receiving pixels. In order to solve such a problem, the present inventor has disclosed an infrared solid-state imaging device disclosed in Japanese Patent Application Laid-Open No. 8-88340. This infrared solid-state imaging device is one in which light receiving pixels composed of a plurality of types of optical cavity structures are arranged on a semiconductor substrate, and "a wavelength region in which incident light and reflected light weaken each other" generated by one or more types of optical cavity structures. Are arranged in a wavelength range in which other types of light receiving pixels can detect light.

The infrared solid-state imaging device having such a configuration has a spectral sensitivity in a "wavelength region where incident light and reflected light weaken" by calculating a difference between detection outputs obtained from a plurality of types of light receiving pixels. Light receiving pixels can be equivalently realized. However, such an infrared solid-state imaging device requires an additional configuration such as a deviation detecting unit when calculating a difference between detection outputs. Therefore, in order to further simplify the configuration of the device, an infrared solid-state imaging device that does not require a deviation detecting unit has been desired.

Therefore, according to the first to third aspects of the present invention,
In order to solve the above-mentioned problems, an object of the present invention is to provide an infrared solid-state imaging device that is suitable for detecting a wavelength distribution and does not require a deviation detecting unit. In order to solve the above-mentioned problems, it is an object of the present invention to provide an infrared light receiving element suitable for detecting a wavelength distribution.

[0019]

According to a first aspect of the present invention, a plurality of light receiving pixels arranged on a semiconductor substrate in a matrix and detecting an infrared ray to generate an electric signal; A signal scanning unit that transfers and outputs an electric signal from the light receiving pixel, and an infrared solid-state imaging device including a reflection unit that is disposed to face the light receiving pixel and reflects at least a part of infrared light from the light receiving pixel side. By setting at least two types of optical distances with respect to the reflecting portion, a plurality of types of optical cavity structures are formed in the semiconductor substrate, and incident light and reflected light are generated by the optical cavity structures strengthening each other. It is characterized in that a plurality of "spectral sensitivity peaks" are shifted from each other within a wavelength range in which a light-receiving pixel can detect light.

In such a configuration, a plurality of types of optical cavity structures are provided on the semiconductor substrate. In each of these optical cavity structures, the incident light and the reflected light reinforce each other, so that the light intensity of the interference light has a peak characteristic. By generating this peak characteristic in the wavelength range where the light receiving pixel can detect light, it is possible to give a desired peak characteristic to the spectral sensitivity of the light receiving pixel.

Since such peak characteristics differ for each type of optical cavity structure, a plurality of light receiving pixels having different spectral sensitivity peak wavelengths are formed on a semiconductor substrate. By using these light receiving pixels, it is possible to detect infrared rays by dividing them into several wavelength bands. The wavelength distribution of infrared rays can be easily obtained based on the detection result for each wavelength band.

Incidentally, Japanese Patent Application Laid-Open No. Hei 8-
FIG. 3, FIG. 5, and FIG. 9 of JP 88340 disclose a case in which a plurality of spectral sensitivity peaks exist within a wavelength range in which a light receiving pixel can detect light. However, each of the spectral sensitivity peaks disclosed in the prior application is a pseudo peak generated by combining a valley portion of light intensity due to the optical cavity structure with a spectral sensitivity characteristic inherent in the light receiving pixel. Therefore, the value of the peak wavelength disclosed in the prior application is clearly different from the value of the wavelength at which the incident light and the reflected light in the present invention strengthen.

Since the peak is generated as described above, in the prior application, the right shoulder portion of the peak substantially coincides with the original spectral sensitivity characteristic of the light receiving pixel. Therefore, the detection output of each light receiving pixel in the prior application commonly includes the output of the right shoulder portion of the peak. As described above, it is difficult to directly determine the infrared wavelength distribution from the values of the respective detection outputs including many common portions. For such a reason, in the prior application, a configuration for obtaining a difference between detection outputs and excluding a common portion of spectral sensitivity was separately provided.

However, in the present invention, a new peak characteristic in which the incident light and the reflected light are strengthened by the optical cavity structure is newly provided. Therefore, the common part of the spectral sensitivity characteristics included in the detection output of each light receiving pixel is reduced, and the wavelength distribution of infrared rays can be directly obtained from the value of each detection output. In addition, in the prior application, since peaks are secondarily generated from both the valley portion of the light intensity and the original spectral sensitivity characteristic of the light receiving pixel, the position of the peak wavelength is sensitively affected by both characteristics. Change. Therefore, it is difficult to use the peak characteristic of such an element as it is for a highly accurate measurement application. However, the peak wavelength in the present invention is almost uniquely determined from the optical cavity structure. Therefore, the value of the peak wavelength does not change so much, and stable characteristics can be easily obtained. Therefore, the peak characteristics in the present invention are particularly suitable for high-accuracy measurement applications.

According to a second aspect of the present invention, in the infrared solid-state imaging device according to the first aspect, a wavelength range in which light can be detected by the light receiving pixel is limited on an infrared ray incident path to the light receiving pixel. A wavelength limiting filter is disposed. Normally, as shown by the wavelength condition of the above-described formula (2), several optical peak wavelengths are generated from one optical cavity structure. Therefore, depending on the setting of the optical distance nd, an unnecessary peak characteristic may be included in the wavelength range in which the light receiving pixels can detect light.

However, according to the second aspect of the present invention, the wavelength range in which light can be detected is limited by the wavelength limiting filter. Therefore, by using this wavelength limiting filter, it is possible to set unnecessary peak characteristics outside the wavelength range in which light can be detected. As a result, it is possible to remove unnecessary noise components resulting from unnecessary peak characteristics from the output of the infrared solid-state imaging device.

(Claim 3) According to a third aspect of the present invention, in the infrared solid-state imaging device according to the first or second aspect, at least two types of optical distances are determined by a light detectable wavelength of a light receiving pixel. "Light intensity peak wavelength" located in the region
(N is an odd number of 3 or more).

Hereinafter, as an example, the peak wavelength λ of the light intensity will be described.
Is set to 3.8 μm. From the wavelength condition of the above equation (2), the optical distance n in this case is obtained.
When the value of d is N = 1, nd = 3.8 × (１ ／) = 0.9
5 μm When N = 3: nd = 3.8 × (3/4) = 2.8
5 μm When N = 5: nd = 3.8 × (5/4) = 4.7
5 μm When N = 7: nd = 3.8 × (7/4) = 6.6
It can be selected from 5 μm.

FIG. 1 is a diagram showing peak characteristics of light intensity obtained from these optical distances nd. As shown in FIG. 1, when N = 1, a relatively gentle peak characteristic is exhibited. On the other hand, when N ≧ 3, a steep peak characteristic is exhibited. FIG. 2 is a diagram showing spectral sensitivity characteristics (calculated values) obtained by multiplying these light intensities by the intrinsic sensitivity of the PtSi film. As shown in FIG. 2, when N = 1, no peak occurs in the spectral sensitivity. On the other hand, when N ≧ 3, a clear peak occurs in the spectral sensitivity. As described above, under the condition of N ≧ 3, it is possible to generate a clear peak characteristic even for a light-receiving pixel whose original spectral sensitivity is not uniform, such as a PtSi film. Therefore, by designing two or more kinds of optical distances under the condition of N ≧ 3, two or more kinds of light receiving pixels having clear peak characteristics can be surely formed. Becomes possible.

(Claim 4) The invention according to claim 4 is a light-receiving section which is disposed on a semiconductor substrate and detects an infrared ray to generate an electric signal, and which is disposed opposite to the light-receiving section and has at least one of the infrared rays. In the infrared light receiving element provided with a reflecting portion for reflecting a portion, an optical distance between the light receiving portion and the reflecting portion is set to at least two or more types to form a region having a plurality of types of optical cavity structures on the semiconductor substrate. In addition, a plurality of "peaks of spectral sensitivity", which are generated when the incident light and the reflected light are strengthened by each of the optical cavity structures, are shifted in a wavelength range in which the light receiving unit can detect light. In the infrared light receiving element having such a configuration, by providing a plurality of types of optical cavity structures, the peak wavelength of the spectral sensitivity generated by strengthening the incident light and the reflected light is shifted for each region of the light receiving unit. By performing infrared detection using such regions of the light receiving section, it is possible to easily obtain the wavelength distribution of infrared light.

According to a fifth aspect of the present invention, in the infrared light receiving element according to the fourth aspect, a wavelength range in which light can be detected by the light receiving section is limited on an infrared ray incident path to the light receiving section. A wavelength limiting filter is provided. In the infrared light receiving element having such a configuration, since the wavelength range in which light can be detected by the wavelength limiting filter is limited in advance, unnecessary peak characteristics resulting from the optical cavity structure are reduced.
It is possible to keep the wavelength outside the wavelength range where light can be detected. Therefore, it is possible to remove unnecessary noise components caused by unnecessary peak characteristics.

According to a sixth aspect of the present invention, in the infrared solid-state imaging device according to the fourth or fifth aspect, at least two types of optical distances are determined by a light-detectable wavelength of the light receiving section. It is set to be N / 4 times (where N is an odd number of 3 or more) the "peak wavelength of light intensity" located in the range.

In such a configuration, since two or more types of optical distances are designed under the condition of N ≧ 3, two or more types of regions having distinct peak characteristics can be reliably formed. Therefore, even when a light receiving unit having a non-uniform original spectral sensitivity, such as a PtSi film, is used, it is possible to reliably obtain the wavelength distribution of infrared rays using a clear peak characteristic.

[0034]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) A first embodiment is an embodiment of an infrared solid-state imaging device according to the first to third aspects of the present invention. FIG. 3 is a diagram illustrating a schematic configuration of the first embodiment. In FIG. 3, a wavelength limiting filter 2 that removes a wavelength less than 3 μm is disposed on the optical axis of the imaging optical system 1 that transmits infrared light. This wavelength limiting filter 2
Behind, an infrared solid-state imaging device 3 is arranged.

On the back side of the infrared solid-state imaging device 3,
As shown in FIG. 4, three types of light receiving pixels 4 to 6 are arranged in a mixed manner. These three types of light receiving pixels 4 to 6 have different values of the optical distance nd of the optical cavity structure. FIG. 5A is a diagram illustrating a cross-sectional structure of the light receiving pixel 4. In FIG. 5A, a PtSi film 12 is formed on a main surface of a p-type silicon substrate 11. This PtSi film 12
Is formed above the insulating film 13 made of silicon oxide (refractive index n = 1.4). On this insulating film 13,
A reflection film 14 made of aluminum or the like is provided. The geometric distance d between the PtSi film 12 and the reflection film 14 is:
In the case of the light receiving pixel 4, it is set to 1.9 μm. On the reflective film 14, insulating films 19 and 29 are formed.

On the other hand, around the PtSi film 12, a guard ring 16 made of an n-type diffusion layer is provided. A long BCCD diffusion layer 17 is buried next to the guard ring 16 with a part of the isolation region 15 interposed therebetween. This BCC
Above the D diffusion layer 17, a CCD transfer electrode 18 is formed via an insulating film. FIG. 5B is a diagram illustrating a cross-sectional structure of the light receiving pixel 5. In FIG. 5B, a PtSi film 12 is formed on a main surface of a p-type silicon substrate 11. Above the PtSi film 12, silicon oxide (refractive index n
= 1.4) is formed. On this insulating film 23, a reflective film 24 made of aluminum or the like is formed.
Is provided. The geometric distance d between the PtSi film 12 and the reflection film 24 is set to 2.05 μm in the case of the light receiving pixel 5. An insulating film 29 is formed on the reflection film 24. On the other hand, a guard ring 26 made of an n-type diffusion layer is provided around the PtSi film 12. A long BCCD diffusion layer 27 is buried next to the guard ring 26 with a part of the separation region 25 interposed therebetween. Above the BCCD diffusion layer 27, the CCD transfer electrode 2 is interposed via an insulating film.
8 are formed. The light receiving pixel 6 has the same structure as described above, and the geometric distance d between the PtSi film 12 and the reflection film is set to 2.2 μm. Next, a method for manufacturing such an infrared solid-state imaging device 3 will be described.

(Manufacturing method of infrared solid-state imaging device 3) First, a relatively thick thermal oxide film and an impurity diffusion region are formed on a p-type silicon substrate 11 by using a known LOCOS separation method (selective oxidation separation method). Are formed. Next, BCCD diffusion layers 17 and 27 are formed, and a CC made of polysilicon is formed above the diffusion layers 17 and 27.
D transfer electrodes 18 and 28 are formed. In parallel with such a forming process, a guard ring 1 composed of an N-type impurity diffusion layer is formed.
6, 26, etc. are also formed.

Next, after the area other than the light receiving area is protected by a resist, wet etching is performed to make a hole in the light receiving area, thereby exposing the surface of the p-type silicon substrate 11. This p
Pt is deposited on the exposed surface of the mold silicon substrate 11 and then heat-treated to form a PtSi film 12. Next, 50
An insulating film 13 having a thickness of 1.9 μm obtained at a relatively low temperature of about 0 ° C. or less is formed on the entire surface. The insulating film 13 can be appropriately selected from various materials such as an oxide film, an oxynitride film, or a nitride film formed by a normal pressure CVD method, a plasma CVD method, a low pressure CVD method, a sputtering method, or the like. However, the insulating film 13
Since the refractive index n differs depending on the type, the film thickness d is appropriately selected so that the optical cavity structure has a desired optical distance nd.

After the formation of the insulating film 13, a reflection film 14 is selectively formed on a region corresponding to the light receiving pixel 4 by using, for example, aluminum or an aluminum alloy. Through such steps, the first optical cavity structure shown in FIG. 5A is formed. Subsequently, an insulating film 19 having a thickness of 0.15 μm obtained at a relatively low temperature of about 500 ° C. or less is additionally formed on the entire surface. At this time, on the region corresponding to the light receiving pixel 5, a thickness of 2.05 .mu.
m of the insulating film 23 is formed.

Thereafter, a reflection film 24 is selectively formed in a region corresponding to the light receiving pixel 5 by using, for example, aluminum or an aluminum alloy. Through these steps, the second optical cavity structure shown in FIG. 5B is formed. Next, an insulating film 29 having a thickness of 0.15 μm obtained at a relatively low temperature of about 500 ° C. or less is additionally formed on the entire surface. At this time, an insulating film having a thickness of 2.2 μm is formed on the region corresponding to the light receiving pixels 6 together with the insulating film 23.

Thereafter, a reflection film is selectively formed on a region corresponding to the light receiving pixel 6 by using, for example, aluminum or an aluminum alloy. Through these steps, a third optical cavity structure is formed.
As described above, in order to form a plurality of types of optical cavity structures, the formation of the insulating film, the reflective film thereon, and the formation of the additional insulating film may be sequentially repeated in ascending order of the set film thickness.

After forming a plurality of types of optical cavity structures in this manner, an insulating film for protecting the surface, metal wiring and the like are formed as required, and the infrared solid-state imaging device 3 is completed. Next, the spectral sensitivity characteristics of the infrared solid-state imaging device 3 thus formed will be described.

(Spectral sensitivity characteristics of infrared solid-state imaging device 3)
According to the manufacturing method described above, each of the light receiving pixels 4 to 6 has an optical cavity structure as shown in the following table. Refractive index n Geometric distance d Optical distance nd Light receiving pixel 4: 1.4 1.9 μm 2.66 μm Light receiving pixel 5: 1.4 2.05 μm 2.87 μm Light receiving pixel 6: 1.4 2.20 μm 3 FIG. 6 is a diagram showing wavelength characteristics of light intensity generated at the position of the PtSi film 12 by such three types of optical cavity structures.

FIG. 7 shows the PtSi film 12 in this state.
FIG. 4 is a diagram showing spectral sensitivity characteristics of FIG. As shown in FIG. 7, the spectral sensitivity characteristics of the light receiving pixels 4 to 6 each have a peak wavelength as shown in the table below. Each of these peak wavelengths substantially corresponds to the peak wavelength λ obtained as N = 3 under the wavelength condition of the above-described equation (2). Since the design was performed under the condition of N = 3,
The steepness of the peak characteristic is large, and is not canceled out by the original spectral sensitivity characteristic of the PtSi film 12. Note that unnecessary peak characteristics of 3 μm or less caused by these optical cavity structures are suppressed by the function of the wavelength limiting filter 2.

FIG. 8A is a diagram showing a change in the ratio of the detection output of the light receiving pixels 4 to 6 for each object temperature. As the object temperature increases, the detection output of the light receiving pixel 4 on the short wavelength side increases, and the detection output of the light receiving pixel 6 on the long wavelength side decreases. FIG. 8B is a diagram showing the ratio between the “detection output of the light receiving pixel 4” and the “detection output of the light receiving pixel 6” for each object temperature.

In general, the emissivity of an object can be regarded as a constant value in a narrow wavelength range. Therefore, by calculating the ratio for the detection output within a narrow wavelength range, it becomes possible to remove the influence of the emissivity that differs for each object. Therefore, it is considered that the temperature change of the detection output ratio as shown in FIGS. 8A and 8B shows the same tendency regardless of the type of the object. Therefore, based on the result of such a detection output ratio, it is possible to know the object temperature of an object whose emissivity is unknown. Next, another embodiment will be described.

(Second Embodiment) The second embodiment is an embodiment of an infrared light receiving element corresponding to the inventions of claims 4 to 6. FIG. 9 is a conceptual diagram illustrating the structure of the infrared light receiving element TD according to the second embodiment.

In FIG. 9, an anti-reflection film 33 is formed on the back surface of the p-type silicon substrate 31. On the other hand, on the surface side of the p-type silicon substrate 31, three PtSi films 32a to 32c are formed with the isolation region 34 interposed therebetween. Reflection films 37a to 37c are formed above the three PtSi films 32a to 32c via insulating layers 36 having different thicknesses (refractive index: 1.4). In this case, three types of optical cavity structures shown in the following table are formed.

Refractive index n Geometric distance d Optical distance nd PtSi film 32a: 1.4 3.07 μm 4.3 μm PtSi film 32b: 1.4 3.21 μm 4.5 μm PtSi film 32c: 1.4 3.34 μm 4.68 μm A common anode terminal 38 is electrically connected to the p-type silicon substrate 31 side. PtSi films 32a to 32c
On the side, cathode terminals 39a to 39c are electrically connected respectively. Further, a wavelength limiting filter 40 for removing a wavelength of less than 3 μm is disposed on the infrared ray incident path.

FIG. 10 is a diagram showing the spectral sensitivity characteristics in the second embodiment. As shown in FIG.
The spectral sensitivity characteristics of the Si films 32a to 32c each show a peak wavelength as shown in the table below. Each of these peak wavelengths substantially corresponds to the peak wavelength λ obtained as N = 5 under the wavelength condition of the above-described equation (2). Note that other unnecessary peak characteristics are suppressed by the function of the wavelength limiting filter 40.

As described above, in the second embodiment, by providing a plurality of types of optical cavity structures on the semiconductor substrate, a plurality of types of light receiving regions having different spectral sensitivity peak positions can be provided on the semiconductor substrate. By using such a plurality of types of light receiving regions and detecting infrared rays by dividing them into several wavelength bands, it is possible to easily detect the wavelength distribution of infrared rays. By detecting the characteristics of the wavelength distribution using such an infrared light receiving element, it is possible to realize, for example, a fire detection device capable of discriminating between burning infrared rays and sunlight.

(Regarding Another Embodiment) In the first and second embodiments described above, the optical distance nd of the optical cavity structure is controlled by the geometric distance d. It is not limited.
Generally, the optical distance nd can be controlled by the refractive index n or a combination of the refractive index n and the geometric distance d.

For example, when a silicon nitride film (refractive index: 2) is used for some of the light receiving pixels instead of the silicon oxide film having a refractive index of 1.4, the geometric distance d between the photoelectric conversion unit and the reflective film is increased.
Without increasing the optical distance nd, it is possible to increase the optical distance nd to about 1.43 times. In the first and second embodiments described above, the silicon semiconductor as the light transmitting substrate and the Pt generated by reacting Pt with the silicon semiconductor are used.
Although the Schottky junction between the Si silicides is used as the light receiving pixel, the present invention is not limited to this. In general,
The present invention can be applied to any quantum-type light receiving pixel (light receiving unit) having an optical cavity structure. For example, as such a quantum-type light receiving pixel, P
In addition to tSi, Pd ₂ Si, IrSi or the like, or palladium silicide or the like can of course be used.

Further, in the first and second embodiments described above, the light receiving pixels (light receiving portions) each composed of the quantum infrared sensor are used, but the present invention is not limited to this. For example, a thermal infrared sensor may be used as the light receiving pixel (light receiving unit) of the present invention. As an example of such a thermal-type infrared sensor, there is known a thermal-type infrared sensor in which a heat sensor portion is formed to have a cross-linking structure and a thermal change due to infrared rays is largely captured. In such an element structure, a plurality of types of optical cavities can be formed on the light receiving surface by providing a plurality of types of optical distances to the reflecting portion under the bridge.

In the first and second embodiments described above, the interlayer material having the optical cavity structure is formed of one kind of insulating film, but the present invention is not limited to this. For example, a plurality of types of materials may be combined as the interlayer material. In this case, assuming that the refractive index of the interlayer material is n1, n2... And the geometric distance of the interlayer material is d1, d2..., The entire optical distance is replaced by (n1d1 + n2d2 +. Just think about it.

Further, in the first and second embodiments described above, three types of optical cavity structures are formed on the semiconductor substrate, but the present invention is not limited to this. For example, two types of optical cavity structures may be formed on a semiconductor substrate. In such a configuration, the number of effective pixels on the semiconductor substrate increases, so that the spatial resolution of the infrared solid-state imaging device can be further increased.

It is needless to say that four or more types of optical cavity structures may be formed on a semiconductor substrate. In such a configuration, the detection band can be further subdivided, so that the characteristics of the wavelength distribution of infrared rays can be obtained more precisely. Such a light receiving device is a device that is particularly suitable for applications such as identification and composition analysis of an object based on characteristics of light emission or absorption spectrum of the object.

Further, in the first and second embodiments described above, 3 or 5 is uniformly used as the value of N, but the present invention is not limited to this. For example,
The value of N may be appropriately changed on one semiconductor substrate. By changing the value of N in this manner, the detection bandwidth can be freely controlled. In the first embodiment described above, the case where the light receiving pixels are arranged in a two-dimensional matrix has been described, but the present invention is not limited to this. For example, a line sensor may be formed by arranging light receiving pixels in a one-dimensional matrix.

[0060]

According to the first and fourth aspects of the present invention, a plurality of types of optical cavity structures are provided on a semiconductor substrate, and a plurality of types of light-receiving pixels having different spectral sensitivity peak wavelengths are provided. (Light receiving area). By using such a plurality of types of light-receiving pixels (light-receiving regions) to detect infrared rays by dividing them into several wavelength bands, it is possible to easily detect the wavelength distribution of infrared rays.

The plurality of types of optical cavity structures can be formed by adding some steps at the time of manufacturing a semiconductor. Therefore, the manufacturing process can be greatly simplified as compared with the case where a color filter for the infrared region is formed. Further, a detection output for each wavelength band can be directly obtained from a plurality of types of light receiving pixels (light receiving regions). Therefore, a conventional configuration such as taking a difference between detection outputs when detecting a wavelength distribution is not required, and the device configuration can be further simplified. As described above, according to the present invention, it is possible to realize a light receiving device for an infrared region having a function similar to the color detection function based on the principle of additive color mixture in the visible region.

(Second and fifth aspects) In the second and fifth aspects of the present invention, since the wavelength limiting filter is provided, it is possible to reduce in advance the wavelength band which is originally unnecessary for detecting the wavelength distribution. In particular, by arranging such a wavelength limiting filter, it is possible to suppress unnecessary peak characteristics secondary to the optical cavity structure.

(Claims 3 and 6) In the invention according to claims 3 and 6, at least two kinds of optical distances are designed under the condition of N ≧ 3, so that light receiving pixels having non-uniform spectral sensitivity can be obtained. It is possible to reliably obtain two or more types of peak characteristics.

[Brief description of the drawings]

FIG. 1 is a diagram showing a peak characteristic of light intensity due to an optical cavity structure.

FIG. 2 is a diagram showing spectral sensitivity characteristics (calculated values) obtained by multiplying light intensity by the intrinsic sensitivity of a PtSi film.

FIG. 3 is a diagram illustrating a schematic configuration of the first embodiment.

FIG. 4 is a diagram illustrating a pixel array of the infrared solid-state imaging device 3;

FIG. 5 is a conceptual diagram illustrating a cross-sectional configuration of a light receiving pixel.

FIG. 6 is a diagram illustrating light intensity characteristics in the first embodiment.

FIG. 7 is a diagram illustrating spectral sensitivity characteristics in the first embodiment.

FIG. 8 is a diagram illustrating a relationship between an object temperature and a detection output ratio.

FIG. 9 is a diagram illustrating a schematic configuration of a second embodiment.

FIG. 10 is a diagram illustrating spectral sensitivity characteristics according to the second embodiment.

FIG. 11 is a diagram showing a configuration of a conventional infrared solid-state imaging device.

FIG. 12 is a diagram showing the light intensity (calculated value) of the interference light at the position of the PtSi film 82.

FIG. 13 is a diagram showing spectral sensitivity characteristics of a PtSi film 82.

FIG. 14 is a diagram showing a wavelength distribution of blackbody radiation.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 imaging optical system 2 wavelength limiting filter 3 infrared solid-state imaging device 4 to 6 light receiving pixels 11 p-type silicon substrate 12 PtSi film 13 insulating film 14 reflection film 15 separation region 16 guard ring 17 BCCD diffusion layer 23 insulation film 24 reflection film 25 separation Region 26 guard ring 27 BCCD diffusion layer 28 CCD transfer electrode 29 insulating film 31 p-type silicon substrate 32 a to 32 c PtSi film 33 antireflection film 36 insulating layer 38 common anode 81 p-type silicon substrate 82 PtSi film 83 insulating film 84 reflective film 85 Separation area 86 Guard ring 87 BCCD diffusion layer

Claims (6)

[Claims] 1. A plurality of light receiving pixels arranged on a semiconductor substrate in a matrix and detecting an infrared ray to generate an electric signal; a signal scanning unit for transferring and outputting an electric signal from the light receiving pixel; An infrared solid-state imaging device comprising: a reflection unit that is disposed to face and reflects at least a part of infrared light that enters from the light receiving pixel side; wherein at least two types of optical distances are provided between the light receiving pixel and the reflection unit. By setting as described above, a plurality of types of optical cavity structures are formed on the semiconductor substrate, and a `` spectral sensitivity characteristic peak '' generated when the incident light and the reflected light are strengthened by each of the optical cavity structures,
An infrared solid-state imaging device, wherein a plurality of light-receiving pixels are arranged so as to be shifted from each other within a wavelength range where light can be detected. 2. The infrared solid-state imaging device according to claim 1, wherein a wavelength limiting filter that limits a wavelength range in which the light receiving pixel can detect light is disposed on an infrared light incident path to the light receiving pixel. Infrared solid-state imaging device. 3. The infrared solid-state imaging device according to claim 1, wherein at least two types of the optical distances are located within a wavelength range in which the light receiving pixels can detect light. N = 4 (where N is an odd number of 3 or more). 4. An infrared light, comprising: a light-receiving portion disposed on a semiconductor substrate and detecting an infrared ray to generate an electric signal; and a reflecting portion disposed to face the light-receiving portion and reflecting at least a part of the infrared ray. In the light receiving element, an optical distance between the light receiving unit and the reflection unit is at least 2
By setting the number of types or more, a region composed of a plurality of types of optical cavity structures is formed on the semiconductor substrate, and the peaks of the spectral sensitivity characteristics are generated when the incident light and the reflected light are strengthened by each of the optical cavity structures. Are shifted in a wavelength range in which the light receiving unit can detect light. 5. The infrared light receiving element according to claim 4, wherein a wavelength limiting filter that limits a wavelength range in which the light receiving unit can detect light is disposed on an infrared light incident path to the light receiving unit. Infrared light receiving element. 6. The infrared solid-state imaging device according to claim 4, wherein at least two types of the optical distances are set such that a “peak wavelength of light intensity” is located within a wavelength range where the light receiving unit can detect light. "
(N is an odd number of 3 or more).