JPH08222716A - Solid-state infrared image sensing device - Google Patents

Abstract

PURPOSE: To make uniform the characteristics of photoelectric conversion parts and to contrive to prevent the generation of a white damage due to cleaning or the like by a method wherein a metal reflective film is formed on an insulating film so that respective lights face a plurality of the photoelectric conversion parts at regions wider than the peripheral edges of the conversion parts and a DC voltage is applied to the metal reflective film from the outside so that the reflective film is held in a previously set potential. CONSTITUTION: The upper part of a region including a plurality of photoelectric conversion parts 101 formed on a first main surface of a semiconductor substrate 102 is covered with an insulating film 107 and in order to make respective lights, which are incident on those parts 101 from the side of a second main surface on the opposite side to the first main surface of the substrate 102 and are made to pass through the parts 101, reflect in the directions incident again on the respective former parts 101, a metal reflective film 108A is formed on the film 107 so that the lights face the parts 101 at regions wider than the peripheral edges of the parts 101. A DC voltage is applied to the film 108A from the outside by a voltage applying means 109 so that the film 108A is held in a previously set potential to be able to make a white damage quench.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared solid-state image pickup device provided with a metal reflection film formed facing a plurality of photoelectric conversion parts on a semiconductor substrate.

[0002]

2. Description of the Related Art The structure of a conventional infrared solid-state image pickup device will be described below with reference to FIGS. First, FIG.
FIG. 3 is a diagram schematically showing a planar configuration of an infrared imaging device. In FIG. 8, the light receiving cells 81 including the photoelectric conversion units that perform photoelectric conversion are arranged in a two-dimensional matrix on the semiconductor substrate 82. The vertical charge transfer units 83 from which the signal charges generated in the respective photoelectric conversion units are read are provided along the columns of the light receiving cells 81 in each interval region between the columns of the light receiving cells 81. Further, the plurality of vertical charge transfer portions 83 are commonly connected to the horizontal charge transfer portion 84 at one end thereof.

In actual reading and transfer of signal charges, transfer electrodes and the like (not shown) provided on the charge transfer section are required. That is, by applying a clock pulse to this transfer electrode, the charge is read out. The clock pulse to the transfer electrode (not shown) is applied to the bonding pad 86 provided around the semiconductor substrate 82.
And from the outside of the substrate through the metal wiring 87 and the like.

The signal charge obtained as a result of photoelectric conversion of the light incident on the photoelectric conversion section is first transferred to the vertical charge transfer section 83, then to the horizontal charge transfer section 84, and finally in the charge read circuit. It is output to the outside of the device via a certain output circuit 85 and a bonding pad 86.

FIG. 9a is an enlarged view of the light receiving area (area where light receiving cells are two-dimensionally arranged) of the infrared solid-state image pickup device having such a schematic plane structure (FIG. 8). here,
For simplification of description, the case where the photoelectric conversion units are arranged in a two-dimensional matrix of three rows and columns (a total of nine) is shown. In FIG. 9 a, the light receiving cell indicates a region surrounded by the element isolation region 4 and the guard ring region 3, and the photoelectric conversion section is formed under the metal reflection film 8. On the other hand, in this figure, the transfer electrode 6 of the vertical charge transfer portion is shown.

FIG. 9b shows a part of the structure near the surface of the substrate in the cross section AB of FIG. 9a. In FIG. 9B, the photoelectric conversion part 1 formed on the first main surface side of the semiconductor substrate 2 is surrounded by a guard ring region 3 and further surrounded by an element isolation region 4 (photoelectric conversion). A region including the portion 1, the guard ring region 3, and the element isolation region 4 is called a light receiving cell). On the other hand, the vertical charge transfer section is composed of a vertical charge transfer path 5 formed in a region between the light receiving cells and a transfer electrode 6 formed thereon.

Further, an insulating film 7 for covering the light receiving cells and the vertical charge transfer portion is provided, and a metal reflection film 8 is provided on the photoelectric conversion portion 1 via the insulating film 7. It should be noted that FIG. 9A shows a first imaging device having the above layer structure.
It is the figure seen from the main surface side. The metal reflection film 8 is individually provided for each light receiving cell, and usually has an area similar to that of the photoelectric conversion portion existing therebelow.

Incident light, which is the light to be imaged, enters the photoelectric conversion portion 1 from the second main surface side of the substrate 2 (below the drawing) and is photoelectrically converted to generate signal charges. However, at this time, only a part of the incident light is photoelectrically converted, and the remaining passing light is reflected by the metal reflection film 8 and again enters the photoelectric conversion unit 1 and is photoelectrically converted.

In general, a Schottky junction is used as the photoelectric conversion section 1 in this type of solid-state image pickup device. The Schottky junction is formed at the contact portion between the semiconductor substrate 2 and the metal silicide layer as the Schottky electrode. Specifically, p-type silicon is used as the semiconductor substrate 2, and platinum silicide (PtSi) layer is used as the metal silicide layer.

Since the metal silicide layer has a very small thickness of about several tens of angstroms, an electric field is concentrated on the periphery of the photoelectric conversion section 1. As a result, the junction breakdown voltage between the metal silicide layer and the semiconductor substrate has an extremely low value.
If the junction breakdown voltage is low, it is not possible to suppress an increase in dark current in the photoelectric conversion section. Therefore, in order to increase the junction breakdown voltage, surround the semiconductor Schottky junction (slightly overlap with the metal silicide layer).
The guard ring region 3 is formed.

The guard ring region 3 is formed by diffusing impurities having a conductivity type opposite to that of the semiconductor substrate 2 into the substrate (depth,
(Thousands of Angstroms). The peripheral edge of the diffusion region has a relatively gentle curvature, and the concentration of the electric field can be prevented. As described above, in the infrared solid-state imaging device employing the guard ring, the electric field concentration in the photoelectric conversion unit can be prevented, so that the junction breakdown voltage of the Schottky junction is increased and the increase in dark current can be suppressed. .

[0012]

However, even in the conventional infrared solid-state image pickup device having such a guard ring structure and having a dark current suppressing effect, the characteristics of a plurality of light receiving cells (especially photoelectric conversion portions) are not uniform. Sometimes,
In particular, it often occurs after the imaging device is washed or dried.

That is, a pseudo signal in the form of white dots or white lines is generated on an image obtained by imaging with this device, as if a high-temperature part exists in the object to be imaged. Was frequent (hereinafter, these pseudo signals are called white flaws). When this white flaw occurs, it is very difficult to see as an image.

This white defect, once generated, does not disappear even if the infrared solid-state image pickup device is turned off, and remains on the image for several months. Further, it may occur or disappear while using the imaging device. In other words, white scratches are not fixed temporally or spatially.

If this white defect is a pixel defect that is fixed temporally and spatially, it is possible to electrically perform a process such as correction. However, there is a fatal problem that the problem of white damage here is such that it cannot be corrected and the infrared solid-state imaging device in which the white defect occurs cannot be put to practical use.

The cause of these white scratches is considered as follows by the study of the present inventors. In other words, if a negative charge is charged by static electricity somewhere on the insulating film on the photoelectric conversion part such as a semiconductor Schottky junction or on the metal reflection film facing the photoelectric conversion part through the insulating film, this charge potential causes photoelectric conversion. The dark current of the conversion unit is subject to increase / decrease, and due to the increase of the dark current, a pseudo signal is added to the original signal charge photoelectrically converted by the photoelectric conversion unit, which causes a white defect in the captured image.

For example, at the final stage of a semiconductor manufacturing process for manufacturing an infrared solid-state image pickup device, a silicon wafer, which is a semiconductor substrate, is sprayed with a high-pressure jet stream of pure water (specific resistance is 18 MΩ or more) from which various ions are removed. To be washed. When the jet of cleaning water having a high specific resistance is sprayed onto the wafer, static electricity is generated, and as a result, the metal reflection film and the like formed on the wafer via the insulating film are charged with negative charges. .

Alternatively, during the cleaning process of the infrared solid-state image pickup device after completion, the drying process in a high-temperature dry atmosphere, and the attachment to the camera, static electricity is generated, and a metal reflection film formed on the wafer via an insulating film is removed. It is charged with a negative charge.

An object of the present invention is to solve the above-mentioned problems of the conventional infrared solid-state image pickup device, in which the characteristics of a plurality of photoelectric conversion parts are kept uniform, and the manufacturing process of the device or after completion of the device is completed. It is an object of the present invention to obtain an infrared solid-state imaging device that not only prevents the occurrence of white scratches due to washing and drying steps but also has good durability against white scratches.

[0020]

In order to achieve the above object, in an infrared solid-state image pickup device according to the invention described in claim 1 of the present application, a plurality of photoelectric conversion portions formed on a first main surface of a semiconductor substrate, An insulating film covering a region including a plurality of photoelectric conversion units, the first photoelectric conversion unit having a semiconductor substrate
The surface of the insulating film in order to reflect each light that has entered from the second main surface side opposite to the main surface and has passed through each photoelectric conversion section in the direction in which it again enters the original photoelectric conversion section. A metal reflective film formed so as to face the plurality of photoelectric conversion units in a region wider than the peripheral edge thereof, and the metal reflective film so as to hold the metal reflective film at a predetermined potential. On the other hand, a voltage applying means for applying a DC voltage from the outside is provided.

An infrared solid-state image pickup device according to a second aspect of the present invention is the infrared solid-state image pickup device according to the first aspect, wherein the semiconductor substrate is a p-type semiconductor substrate, and the voltage applying means is the DC voltage. As the above, a direct current voltage having a polarity for maintaining the potential of the metal reflection film at a positive potential relative to the potential of the semiconductor substrate is applied.

An infrared solid-state image pickup device according to a third aspect of the present invention is the infrared solid-state image pickup device according to the first or second aspect, in which the photoelectric conversion portion is formed on the semiconductor substrate and in contact with the semiconductor substrate. And a Schottky junction formed by the metal silicide layer and the Schottky electrode.

An infrared solid-state image pickup device according to a fourth aspect of the present invention is the infrared solid-state image pickup device according to the third aspect, wherein the metal reflection film is located at least at a peripheral edge of the metal silicide layer of the photoelectric conversion section. It is characterized by extending to the outside.

In the infrared solid-state imaging device according to the invention described in claim 5, a plurality of photoelectric conversion portions formed on the first main surface of the semiconductor substrate and a region covering the plurality of photoelectric conversion portions are covered. One insulating film, each light incident on the plurality of photoelectric conversion units from the second main surface side opposite to the first main surface of the semiconductor substrate and passing through each photoelectric conversion unit is converted into the original photoelectric conversion. A plurality of metals formed on the surface of the first insulating film so as to face each of the plurality of photoelectric conversion portions in a region wider than the peripheral edge thereof in order to reflect the light in the direction in which the light is incident again on the portion. A reflective film, having a surface that is flattened and covers the area including the plurality of metal reflective films;
And a second insulating film including a plurality of through holes reaching the plurality of metal reflecting films, formed on the flattened surface of the second insulating film so as to face the plurality of metal reflecting films,
A metal thin film electrically connected to the plurality of metal reflection films via the plurality of through holes, and a DC voltage from the outside to the metal thin film so as to hold the metal reflection film at a predetermined potential. And a voltage applying means for applying.

An infrared solid-state image pickup device according to a sixth aspect of the present invention is the infrared solid-state image pickup device according to the fifth aspect, wherein the semiconductor substrate is a p-type semiconductor substrate, and the voltage applying means is the DC voltage. As the above, a direct current voltage having a polarity for maintaining the potential of the metal reflection film at a positive potential relative to the potential of the semiconductor substrate is applied.

An infrared solid-state image pickup device according to a seventh aspect of the present invention is the infrared solid-state image pickup device according to the fifth or sixth aspect, wherein the photoelectric conversion portion is formed on the semiconductor substrate and in contact with the semiconductor substrate. And a Schottky junction formed by the metal silicide layer and the Schottky electrode.

An infrared solid-state image pickup device according to an eighth aspect of the present invention is the infrared solid-state image pickup device according to the seventh aspect, wherein the metal reflection film is formed at least from the peripheral edge of the metal silicide layer of the photoelectric conversion section. It is characterized by extending to the outside.

An infrared solid-state image pickup device according to a ninth aspect of the present invention is the infrared solid-state image pickup device according to the seventh aspect, wherein the metal thin film is outside the peripheral edge of at least the metal silicide layer of the photoelectric conversion section. It is characterized by extending to the direction.

According to a tenth aspect of the present invention, there is provided an infrared solid-state image pickup device, wherein a plurality of photoelectric conversion portions formed on a first main surface of a semiconductor substrate and a region including the plurality of photoelectric conversion portions are covered. One insulating film, each light incident on the plurality of photoelectric conversion units from the second main surface side opposite to the first main surface of the semiconductor substrate and passing through each photoelectric conversion unit is converted into the original photoelectric conversion. A plurality of metals formed on the surface of the first insulating film so as to face each of the plurality of photoelectric conversion portions in a region wider than the peripheral edge thereof in order to reflect the light in the direction in which the light is incident again on the portion. A reflective film, a second insulating film covering a region including the plurality of metal reflective films and having a planarized surface, and the plurality of metal reflections on the planarized surface of the second insulating film A plurality of metal reflections formed so as to face the film. With respect to the second insulating film, the metal thin film is galvanically insulated by the second insulating film, and is capacitively coupled AC alternating current, and the metal thin film so as to hold the metal thin film at a predetermined potential. And a voltage applying means for externally applying a DC voltage.

The infrared solid-state image pickup device according to the invention described in claim 11 is the infrared solid-state image pickup device according to claim 10, wherein the semiconductor substrate is a p-type semiconductor substrate, and the voltage applying means is the DC voltage. As the above, a direct current voltage having a polarity for maintaining the potential of the metal reflection film at a positive potential relative to the potential of the semiconductor substrate is applied.

An infrared solid-state image pickup device according to a twelfth aspect of the present invention is the infrared solid-state image pickup device according to the tenth or eleventh aspect, wherein the photoelectric conversion section is a semiconductor substrate.
A Schottky junction formed by a Schottky electrode made of a metal silicide layer formed in contact with the semiconductor substrate is included.

According to a thirteenth aspect of the present invention, there is provided an infrared solid-state imaging device according to the twelfth aspect, wherein at least one of the metal reflection film and the metal thin film is at least the photoelectric conversion unit. It is characterized in that it extends outward from the peripheral edge of the metal silicide layer.

[0033]

The infrared solid-state image pickup device according to the invention described in claim 1 is mainly composed of a plurality of photoelectric conversion parts, an insulating film, a metal reflection film, and a voltage applying means. The plurality of photoelectric conversion units are formed on the first main surface of the semiconductor substrate, and an insulating film that covers the region including the plurality of photoelectric conversion units,
On the surface of the insulating film, a metal reflection film facing each photoelectric conversion portion is formed. The voltage applying means applies a DC voltage from the outside to the metal reflection film.

That is, the metal reflection film provided in the infrared solid-state image pickup device of the present invention has a size to face a plurality of photoelectric conversion units in a region wider than the peripheral edge thereof, and at the same time, is preliminarily set by the voltage applying means. It is held at the specified potential.

Generally, in an image pickup device, the semiconductor substrate is cleaned at the final stage of its manufacturing process. As a cleaning method at this time, a method of spraying a jet flow of pure water having a high specific resistance is often used. According to this method
Electrostatic charges are generated in the metal reflection film facing the photoelectric conversion unit or the insulating film ordinarily provided between the photoelectric conversion unit and the metal reflection film, so that the film is negatively charged. In addition, during the cleaning of the image pickup device after completion and the drying process in the atmosphere where high temperature and dry air are forced to convection, static electricity is generated on the metal reflection film, etc. formed on the surface of the substrate, resulting in negative charge. Resulting in.

Even so, in the device of the present invention, the metal reflection film facing the photoelectric conversion portion is held at a predetermined potential, for example, preferably a positive potential when the conductivity type of the semiconductor substrate is p-type. , The effect of static electricity can be eliminated. Therefore, since the dark current does not increase in the photoelectric conversion unit, a pseudo signal due to the dark current does not occur. As a result, the occurrence of white scratches on the image can be prevented, the image is formed only by the signal charges corresponding to the incident light, and the characteristics of the plurality of photoelectric conversion units are kept uniform.

Further, even while the infrared solid-state image pickup device is being used, since the metal reflection film is kept at a predetermined electric potential, white scratches are not similarly generated on the screen.
The photoelectric conversion unit can be kept in a state where the characteristics are uniform.

Furthermore, the effect of preventing the occurrence of white scratches described above extends to the same extent as the size of the metal reflection film facing the photoelectric conversion portion, and therefore the effect of the metal reflection film provided in the device of the present invention is the same. In addition, when the photoelectric conversion unit faces the photoelectric conversion unit with an area extending to a region wider than the peripheral edge of the photoelectric conversion unit, the effect of preventing white scratches can be exerted on the region wider than the peripheral edge of the photoelectric conversion unit. As a result, the device has good durability against white scratches.

For example, as a result of a durability test against white scratches by leaving the device of the present invention in an environment where static electricity is generated at a constant rate, the size of the metal reflection film is photoelectrically converted as in the conventional device. It was obtained that the white scratches increased remarkably with the passage of time as long as it was about the same as the parts, whereas the device of the present invention could effectively prevent the increase of white scratches.

An infrared solid-state image pickup device according to a second aspect of the present invention is the infrared solid-state image pickup device according to the first aspect, wherein a p-type semiconductor is used as a semiconductor substrate, and metal reflection from the outside is caused by voltage application means. The DC voltage applied to the film has such a polarity that the potential of the metal reflection film is kept relatively positive with respect to the potential of the substrate. At this time, the potential of the metal reflection film facing the photoelectric conversion unit is kept at a positive potential relatively to the potential of the photoelectric conversion unit.

Therefore, the negative charges due to static electricity do not accumulate in the metal reflection film facing the photoelectric conversion portion or the insulating film provided between the photoelectric conversion portion and the metal reflection film, and the static electricity to the photoelectric conversion portion is not accumulated. It is possible to eliminate the influence of the charging potential due to. As a result, the occurrence of white scratches on the image can be prevented, the image is formed only by the signal charges corresponding to the incident light, and the characteristics of the plurality of photoelectric conversion units are kept uniform.

In the infrared solid-state image pickup device according to the invention described in claim 3, the photoelectric conversion portion is formed by the Schottky junction. That is, the metal silicide layer is formed in contact with the semiconductor substrate, and the junction between the Schottky electrode and the semiconductor substrate forms a Schottky junction.

Generally, in a Schottky junction, since the substantial thickness of the junction is extremely thin, for example, 100 angstroms or less, electric field concentration is strong at the periphery of the junction, and the junction breakdown voltage is extremely low only by the Schottky junction. Become. Therefore, in order to increase the junction breakdown voltage, a guard ring is formed around the Schottky junction by diffusion of impurities. However, if there is a facing metal film (such as a metal reflection film in the present invention) that capacitively couples to the Schottky junction, the junction breakdown voltage changes under the influence of the potential of the facing metal film.

From this, it can be understood that if the metal reflection film or the like is charged with negative charges, the guard ring around the Schottky junction does not function sufficiently due to the influence thereof, and the junction breakdown voltage decreases. One possible solution to this is to prevent the function of the guard ring from being affected by the potential of the facing metal film that capacitively couples to the Schottky junction. However, in this case, since the impurity concentration of the guard ring must be increased, the result is that the effective area of the photoelectric conversion portion of the light receiving cell is narrowed,
It is only against the improvement of the sensitivity and the resolution of the image pickup device.

On the other hand, in the infrared solid-state image pickup device according to the present invention, the metal reflection film has a predetermined potential,
For example, for a p-type substrate, not only is it maintained at a positive potential, but it also extends over a region wider than the periphery of the Schottky junction, so the effective area of the photoelectric conversion portion of the light receiving cell is narrowed. It is possible to effectively reduce white scratches caused by static electricity. Therefore, it is possible to maintain uniform light receiving characteristics among the light receiving cells.

In the infrared solid-state image pickup device according to the invention described in claim 4, the metal reflection film described in claim 3 extends at least outside the peripheral edge of the metal silicide layer of the photoelectric conversion section. .

The metal silicide layer functions as the Schottky electrode as described above, and the photoelectric conversion portion by the Schottky junction is provided at the junction between the metal silicide layer and the semiconductor substrate. Also,
As described above, the metal silicide layer has a very small thickness of about several tens of angstroms. The strongest concentration of the electric field that contributes to the increase of dark current is at the junction with the semiconductor substrate at the peripheral edge of the metal silicide layer.

On the other hand, in the infrared solid-state imaging device according to the present invention, the metal reflection film kept at a predetermined potential, for example, preferably a positive potential with respect to the potential of the p-type substrate is at least the metal silicide layer. Extends to the outside of the perimeter edge of. Therefore, it is possible to effectively suppress an increase in dark current in the photoelectric conversion unit, it is possible to prevent the occurrence of white scratches due to static electricity, at the same time, it is possible to achieve good durability against white scratches, The characteristics of the plurality of photoelectric conversion units can be kept uniform.

An infrared solid-state image pickup device according to a fifth aspect of the present invention includes a plurality of photoelectric conversion units, a first insulating film, a plurality of metal reflecting films, a second insulating film, a metal thin film, and a voltage. It is mainly composed of an application means. The plurality of photoelectric conversion units are formed on the first main surface of the semiconductor substrate, and the first insulating film that covers the region including the plurality of photoelectric conversion units is further formed on the surface of the first insulating film. A plurality of metal reflection films facing the photoelectric conversion unit are formed.

A second insulating film is formed on a region including a plurality of metal reflection films, and a metal thin film is formed on the flattened surface so as to face each metal reflection film. . The second insulating film includes a plurality of through holes reaching from the metal thin film to each metal reflection film, and the plurality of metal reflection films are electrically connected to the metal thin film through the plurality of through holes. There is. The voltage applying means applies a DC voltage from the outside to the metal thin film.

That is, each metal reflection film provided in the infrared solid-state image pickup device of the present invention has a size that faces each photoelectric conversion portion in a region wider than the periphery thereof, and at the same time,
It is held at a predetermined potential by the voltage applying means through the metal thin film and the through hole.

Therefore, it is possible to prevent the generation of white scratches due to static electricity generated during cleaning of the semiconductor substrate at the final stage of manufacturing the image pickup device, or cleaning and drying after the device is completed, and the characteristics of the plurality of photoelectric conversion units are uniform. Kept in. In addition, since the metal reflection film is kept at a predetermined potential even when the device is in operation, white scratches are not similarly generated on the screen, and the characteristics of the plurality of photoelectric conversion units are kept uniform. .

Furthermore, the effect of preventing the occurrence of the above-mentioned white scratches extends to the same extent as the size of the metal reflection film (or the metal thin film) facing the photoelectric conversion portion, and therefore is provided in the device of the present invention. When facing the photoelectric conversion part with an area extending to a region wider than the periphery of the photoelectric conversion part like a metal reflection film, the effect of preventing the occurrence of white scratches can be achieved in a region wider than the periphery of the photoelectric conversion part. Can be exerted. As a result, the device has good durability against white scratches.

An infrared solid-state image pickup device according to a sixth aspect of the present invention is the infrared solid-state image pickup device according to the fifth aspect, wherein a p-type semiconductor is used as a semiconductor substrate, and a metal thin film is externally applied by voltage application means. The direct current voltage applied to has a polarity such that the potential of the metal reflection film is kept at a positive potential relative to the potential of the substrate.
At this time, the potential of the metal reflection film facing the photoelectric conversion unit is kept at a positive potential relatively to the potential of the photoelectric conversion unit.

Therefore, negative charges due to static electricity do not accumulate in the metal reflection film facing the photoelectric conversion unit or the insulating film provided between the photoelectric conversion unit and the metal reflection film, and the static electricity to the photoelectric conversion unit is not accumulated. It is possible to eliminate the influence of the charging potential due to. As a result, the occurrence of white scratches on the image can be prevented, the image is formed only by the signal charges corresponding to the incident light, and the characteristics of the plurality of photoelectric conversion units are kept uniform.

In the infrared solid-state image pickup device according to the invention described in claim 7, the photoelectric conversion portion is formed by a Schottky junction. That is, the metal silicide layer is formed in contact with the semiconductor substrate, and the junction between the Schottky electrode and the semiconductor substrate forms a Schottky junction.

A direct current voltage is applied to the metal thin film from the outside, and this is applied to all the metal reflective films facing the Schottky junction via a plurality of through holes, and the metal reflective film is predetermined. The potential, for example the potential of the p-type substrate, is preferably kept relatively positive. In addition, the metal reflection film extends in a region wider than the peripheral edge of the Schottky junction. Therefore, the junction breakdown voltage in the Schottky junction is improved and the dark current is reduced. As a result, the characteristics among the plurality of Schottky junctions become uniform.

In the infrared solid-state image pickup device according to the eighth aspect of the present invention, each metal reflection film held at a predetermined potential, for example, a positive potential preferably relative to the potential of the p-type substrate, It extends at least outward from the peripheral edge of the metal silicide layer. Therefore, it is possible to effectively suppress an increase in dark current in the photoelectric conversion unit, prevent the occurrence of white scratches due to static electricity, and at the same time have good durability against white scratches. The characteristics of the photoelectric conversion part can be kept uniform.

In the infrared solid-state image pickup device according to the ninth aspect of the present invention, a DC voltage is applied from the outside and, for example, p
The metal thin film, which is preferably held at a positive potential relatively to the potential of the mold substrate, extends at least outside the peripheral edge of the metal silicide layer. Therefore, it is possible to effectively suppress an increase in dark current in the photoelectric conversion unit, prevent the occurrence of white scratches due to static electricity, and at the same time have good durability against white scratches. The characteristics of the photoelectric conversion part can be kept uniform.

An infrared solid-state image pickup device according to a tenth aspect of the present invention is a plurality of photoelectric conversion units, a first insulating film, a plurality of metal reflection films, a second insulating film, a metal thin film, and a voltage. It is mainly composed of an application means. The plurality of photoelectric conversion units are formed on the first main surface of the semiconductor substrate, and the first insulating film that covers the region including the plurality of photoelectric conversion units is further formed on the surface of the first insulating film. A plurality of metal reflection films facing the photoelectric conversion unit are formed.

A second insulating film is formed on a region including a plurality of metal reflection films, and a metal thin film is formed on the flattened surface so as to face each metal reflection film. ing. The metal thin film is galvanically isolated from the plurality of metal reflective films by the second insulating film, and is capacitively coupled AC electrically. The voltage applying means applies a DC voltage from the outside to the metal thin film.

That is, each metal reflection film provided in the infrared solid-state image pickup device of the present invention has a size to face each photoelectric conversion portion in a region wider than the peripheral edge thereof, and at the same time, is preliminarily set by the voltage applying means. It is capacitively coupled with a metal thin film held at a specified potential.

Assuming that the capacitance between the metal reflection film and the semiconductor substrate is C ₁ and the capacitance between the metal thin film and the metal reflection film is C ₂ , these capacitances are equivalent. They are connected in series. Therefore, assuming that a predetermined potential applied to the metal thin film from the outside is V _a and a potential of the semiconductor substrate (photoelectric conversion portion) is V _c , the potential V _{b of the} metal reflection film given by capacitive coupling with the metal thin film is given. Becomes like the following formula (1).

V _b = (C ₁ × V _c + C ₂ × V _a ) / (C ₁ + C ₂ ) ·· Equation (1)

Therefore, a direct current voltage (bias voltage) V _a applied to the metal thin film and _a certain potential V _b determined by the potential V _{c of the} semiconductor substrate are applied to the metal reflection film. Here, if the potential V _c of the semiconductor substrate is kept at a predetermined constant value, the potential V _b of the metal reflection film is also kept constant.

As described above, since the metal reflection film facing the plurality of photoelectric conversion parts is substantially electrostatically shielded by the metal thin film and the semiconductor substrate, it is caused by static electricity generated during the manufacturing process and after completion. The influence of the charging potential can be removed, the occurrence of white scratches can be prevented, and the characteristics of the plurality of photoelectric conversion units can be kept uniform. Further, even when the device is operated, a DC voltage is applied to the metal thin film, and the metal reflection film is held at a predetermined potential by capacitive coupling with the metal thin film. This also eliminates the influence of the charging potential caused by static electricity, similarly, white scratches do not occur on the screen, and the characteristics of the plurality of photoelectric conversion units are kept uniform.

Furthermore, the effect of preventing the occurrence of the above-mentioned white scratches extends to the same extent as the size of the metal reflection film (or metal thin film) facing the photoelectric conversion portion, and therefore the metal reflection film as in the present invention. Is facing the photoelectric conversion unit with an area extending to a region wider than the periphery of the photoelectric conversion unit,
The effect of preventing the occurrence of white scratches can be exerted on a region wider than the peripheral edge of the photoelectric conversion unit. As a result, the device has good durability against white scratches.

The infrared solid-state image pickup device according to the invention of claim 11 is the infrared solid-state image pickup device of claim 10 in which a p-type semiconductor is used as a semiconductor substrate, and a metal thin film is externally applied by a voltage applying means. The direct current voltage applied to has a polarity such that the potential of the metal reflection film is kept at a positive potential relative to the potential of the substrate.

That is, if a positive potential relative to the potential V _c of the semiconductor substrate is given as the DC voltage (bias voltage) V _a externally applied to the metal thin film by the voltage applying means, the above formula ( From 1), the potential V _{b of the} metal reflection film
Is held at a positive potential relatively to the potential of the substrate by capacitive coupling with the metal thin film. At this time, the potential of the metal reflection film facing the photoelectric conversion unit is kept at a positive potential relatively to the potential of the photoelectric conversion unit.

Therefore, negative charges due to static electricity do not accumulate in the metal reflection film facing the photoelectric conversion portion or the insulating film provided between the photoelectric conversion portion and the metal reflection film, and the static electricity to the photoelectric conversion portion is not accumulated. It is possible to eliminate the influence of the charging potential due to. As a result, the occurrence of white scratches on the image can be prevented, the image is formed only by the signal charges corresponding to the incident light, and the characteristics of the plurality of photoelectric conversion units are kept uniform.

In the infrared solid-state image pickup device according to the twelfth aspect of the present invention, the photoelectric conversion portion is formed by the Schottky junction. That is, the metal silicide layer is formed in contact with the semiconductor substrate, and the junction between the Schottky electrode and the semiconductor substrate forms a Schottky junction.

A direct current voltage is applied to the metal thin film from the outside, and this potential is applied to all metal reflective films facing the Schottky junction by capacitive coupling. As a result, the metal reflective film is also a p-type substrate, for example. The potential is preferably kept relatively positive with respect to the potential. In addition, the metal reflection film extends in a region wider than the peripheral edge of the Schottky junction. Therefore, the junction breakdown voltage in the Schottky junction is improved and the dark current is reduced. As a result, the characteristics among the plurality of Schottky junctions become uniform.

In the infrared solid-state image pickup device according to the thirteenth aspect of the present invention, for example, at least one of the metal thin film and the metal reflective film held at a positive potential, which is preferably relatively positive to the potential of the p-type substrate, is The photoelectric conversion portion extends at least outside the peripheral edge of the metal silicide layer. Therefore, it is possible to effectively suppress an increase in dark current in the photoelectric conversion unit, prevent the occurrence of white scratches due to static electricity, and at the same time have good durability against white scratches. The characteristics of the photoelectric conversion part can be kept uniform.

[0074]

【Example】

(First Embodiment) The present invention will be described in more detail through the following embodiments. First, a first embodiment of the infrared solid-state imaging device according to the present invention will be described below with reference to FIG. FIG. 1A is a diagram schematically showing a part of a plane configuration (viewed from the first main surface side) of an apparatus including a light receiving region in which light receiving cells are two-dimensionally arranged. Here, in order to simplify the description, a case is shown in which only the light receiving region is enlarged and a total of nine light receiving cells, which are three vertically and horizontally, are two-dimensionally arranged.

The hatched portion 108 shown in FIG. 1a.
A represents a metal reflection film. The metal reflective film 108A is
It is formed continuously over three light receiving cells arranged in the vertical direction. This may of course be formed continuously in the horizontal direction. As can be seen from the figure, unlike the conventional device (FIG. 9), the metal reflection film 108A of the present embodiment has the peripheral edge extending to the element isolation region 104, and the photoelectric conversion portion and its periphery are surrounded. It covers the area including the surrounding guard ring area. Here, the region 10 representing the photoelectric conversion unit
No. 1 is shown in the figure, this is the metal reflection film 108.
Since it is formed under A, it cannot be seen from the first main surface side.

FIG. 1b shows a part of the structure near the surface of the substrate in the section AB of FIG. 1a. In FIG. 1B, the photoelectric conversion unit 101 formed on the first main surface side of the semiconductor substrate 102.
Are surrounded by the guard ring region 103, and further surrounded by the element isolation region 104 (the photoelectric conversion unit 101, the guard ring region 103, and the element isolation region 1).
A region including 04 is called a light receiving cell). On the other hand, the vertical charge transfer section is composed of a vertical charge transfer path 105 formed in the interval region of the light receiving cells, a transfer electrode 106 formed thereon, and the like.

Further, an insulating film 107 is provided so as to cover the light receiving cells and the vertical charge transfer portion, and a metal reflection film 108A is provided on the photoelectric conversion portion 101 via the insulating film 107. There is. This metal reflection film 108A
As described above, covers the guard ring region 103 surrounding the photoelectric conversion unit 101 and extends to the element isolation region 104.

A voltage is externally applied to the metal reflective film 108A by the voltage applying means 109,
When the conductivity type of the semiconductor substrate 102 is p-type, it is fixed so as to have a positive potential relative to the potential of the substrate. Here, since the metal reflection film 108A is formed continuously in the vertical or horizontal direction on the plane, the above-described power feeding is facilitated.

Experimental results have shown that the positive potential is preferably in the range of 5 V to 30 V with respect to the semiconductor substrate 102. Further, if the positive potential is in the range of 10 V to 15 V, it can be used in common with the power supply voltage (not shown) of the circuit used to drive the charge transfer unit (105 etc.), which is advantageous in terms of cost. More preferable.

As described above, fixing the metal reflection film 108A to a positive potential with respect to the p-type substrate reduces white scratches on the image of the device.
If the potential of is fixed to a negative potential with respect to the p-type substrate 102, an increase in white defects is naturally observed on the image of the device. From the above, the present inventors consider the cause of the increase in white scratches as follows.

Static electricity, which is a negative charge, is accumulated in the insulating film 107 on the photoelectric conversion unit 101 or somewhere in the metal reflection film 108A facing the photoelectric conversion unit 101 through the insulating film 107 and charged to a negative potential. For example, the majority carriers of the substrate are gathered on the surface of the p-type semiconductor substrate on which the photoelectric conversion unit 101 is formed, so that the impurity concentration of the guard ring 103 is effectively reduced.

At the same time, the electric field distribution of the guard ring 103 itself, the substrate 102 and the charging film (107 or 108).
The concentration of the electric field proceeds due to the combination with the electric field distribution generated between A). Due to the synergistic effect of the two, the guard ring effect becomes insufficient and the dark current increases. Therefore, a pseudo signal due to a dark current is added to the signal charge corresponding to the imaged light, and a white defect occurs on the captured image.

In the present embodiment, since the metal reflection film 108A is fixed at a positive potential with respect to the p-type substrate, white scratches on the image of the device are reduced, which is disadvantageous in strengthening the guard ring effect itself ( It is possible to avoid a decrease in the effective area of the photoelectric conversion unit.

Furthermore, the infrared solid-state image pickup device of this embodiment is
As described above, not only is the metal reflection film 108A provided on the photoelectric conversion unit 101 fixed to a positive potential, but its size is limited. That is, the metal reflection film 108A
A peripheral edge of the element extends to the element isolation region 104, and a region including the photoelectric conversion unit 101 and the guard ring region 103 surrounding the photoelectric conversion unit 101 is covered with the metal reflection film 108A. On the other hand, the metal reflection film 8 in the conventional device (FIG. 9) had an area similar to that of the photoelectric conversion section 1.

Here, the apparatus of this embodiment and the conventional apparatus were each subjected to a high temperature storage test in which an environment in which static electricity was generated at a constant rate was provided and the apparatus was left in the environment. The result is that due to the size of the metal reflective film formed on the photoelectric conversion unit, the durability against white scratches that occur on the image is different, and the metal reflective film extends to the element isolation region as in this example. It has been clarified that the extended device can effectively prevent the increase of white scratches. Next, a description will be given.

The high-temperature storage test conducted here was performed by keeping the environment temperature at 150 ° C. and leaving the completed device in an atmosphere in which dry air (or nitrogen) was forced to convection. Generate static electricity at a certain rate,
The change in white scratches on the image of the device was examined.

The apparatus (6 pieces) of the present example and the conventional apparatus (5 pieces) were left in this atmosphere, and the images of the respective apparatuses were observed 100 hours and 250 hours after being left, and white scratches were observed. The results of counting the increased number of devices are shown in Table 1. In the conventional device, white scratches did not occur on all five devices after 100 hours, but white scratches on the image increased with the passage of time, and after 250 hours, all five devices had white scratches. Was increasing. However, in the device of the present invention, white defects did not occur in all 6 devices even after 250 hours had passed.

[0088]

[Table 1]

From the above results, it can be seen that the conventional apparatus can prevent white scratches to some extent, but after 250 hours, the white scratches increased remarkably, so that the effect of preventing white scratches was not sufficient. It was On the other hand, in the device of the present embodiment, the durability against white scratches is good, and by extending the metal reflective film to a region wider than the peripheral edge of the photoelectric conversion unit, white scratches are generated more effectively. It became clear that it could be prevented. That is, in order to effectively prevent the occurrence of white scratches, it is necessary to extend the metal reflection film to a region wider than the peripheral edge of the photoelectric conversion section.

A method of manufacturing the infrared solid-state imaging device of the first embodiment having the above structure will be described below with reference to the sectional views 13a to 13f showing the formation state at each stage of the manufacturing process.

In the infrared solid-state image pickup device of this embodiment,
A p-type silicon semiconductor is used as the semiconductor substrate. In FIG. 13a, first, the element isolation region 104 is formed. This is the well known LOCOS
Silicon substrate 102 by a separation method (selective oxidation separation method)
It is composed of a relatively thick thermal oxide film formed above and a p ⁺ -type impurity diffusion region having a high impurity concentration formed immediately below the thermal oxide film to enhance element isolation.

Next, a BCCD (Buried Channel CCD) diffusion layer 105 is formed in the vertical charge transfer portion as a vertical charge transfer path, and a CC made of polysilicon is formed on the diffusion region 105.
The D transfer electrode 106 is formed. After that, an n-type impurity having a conductivity type opposite to that of the substrate is diffused into the substrate 102 to thereby form an n-type impurity diffusion layer 103 as a guard ring region.
Is formed. The depth is about 300 nm.

Although not shown in the figure, the source and the source of the MOS transistor, which is the output section of the charge transfer section, are formed.
All of the various thermal diffusion layers, including the drain diffusion layer, and all polysilicon electrodes are formed. Figure 13a
Shows the state where the formation of the thermal diffusion layer and the polysilicon electrode is completed. In this state, both the polysilicon electrode portion and the region to be the photoelectric conversion portion are covered with the thin oxide films 110 and 111.

Subsequently, as shown in FIG. 13B, a relatively thick oxide insulating film 112 having a thickness of about 400 to 1000 nm is laminated on the entire surface of the silicon substrate 102 by the CVD method (chemical vapor deposition method). . Usually, the insulating film 112 contains impurities such as phosphorus, boron, and arsenic,
When heat-treated at a temperature of about 900 ° C., the surface shape becomes flat.

As described above, the method of flattening the insulating film 112 containing impurities by heat treatment is a technique well known as "reflow treatment". This "reflow treatment" is effective in preventing electrical defects (disconnection, short circuit, etc.) of the metal wiring made of aluminum or aluminum alloy or the like that will be formed in a later step.

After the "reflow process" is completed, the resist 11
3 is applied, and then exposure / development processing is performed to perform patterning for removing the thermal oxide film 111 and the insulating film 112 in the region to be the photoelectric conversion portion. The state when this patterning is completed is shown in FIG. 13b. Next, the thin thermal oxide film 111 and the insulating film 112 are simultaneously etched and removed by a wet etching method to expose the surface of the silicon substrate 102. The state at this time is shown in FIG. 13c.

Now, referring to FIG. 13b and FIG. 13c described above.
The process will be described in more detail. In general, the photoelectric conversion unit in a solid-state image pickup device is the most important element active region and should not be damaged by crystal defects or the like. Therefore, in the step of forming a hole in the oxide insulating film 112 or the like by the above-described CVD method (FIG. 13c), the silicon substrate 102 is
The dry etching method, which easily damages the substrate, cannot be applied.
Therefore, first, the "reflow process" is performed on the CVD oxide insulating film 112 (FIG. 13B), and then the holes are formed by the wet etching method.

At this time, in the wet etching method, since the etching proceeds at a constant speed in all directions, side etching is large. As a result, if the insulating film 112 becomes extremely thin in the portion indicated by reference numeral I in FIG. 13C, electrical defects of the CCD transfer electrode 106 will frequently occur.

In order to prevent this, it is necessary to provide the resist 113 to a position that is sufficiently inside the light receiving cell by patterning, that is, to increase the dimension L ₁ in FIG. 13c with a sufficient margin. Normal,
The dimension L ₁ is selected to be about 1.5 to 2 μm. Therefore, assuming that the width W of the element active region to be formed in the light receiving cell is, for example, 10 μm, the width L ₂ of the region where the effective portion of the light receiving cell can actually be formed is about 6 to 7 μm.

Silicon substrate 1 in a region to be a photoelectric conversion part
After exposing the surface of 02, the resist 113 is peeled off.
Cleaning is performed, and then a photoelectric conversion unit is formed. In the step of forming the photoelectric conversion part, first, Pt is deposited on the exposed surface of the silicon substrate 102 in the region to be the photoelectric conversion part, and then heat treatment is performed. Therefore, platinum reacts with silicon to form a PtSi layer (platinum silicide layer). The platinum that did not react with the silicon remained
To be removed. In this way, the photoelectric conversion section (Schottky barrier diode) is formed at the junction between the PtSi layer and the Si substrate.
101 is formed. This state is shown in FIG. 13d.

Thereafter, as shown in FIG. 13e, a relatively thick oxide insulating film 107 is laminated on the entire surface by the CVD method again. At this time, as the material of the insulating film 107,
The same material as that of the insulating film 112 described above can be used.

After the step shown in FIG. 13e is completed, in the next step, as shown in FIG. 13f, a metal reflection film 108 made of aluminum or an aluminum alloy is formed on the surface of the insulating film 107 on the photoelectric conversion portion 101. . Finally, a wiring layer (not shown) made of aluminum or an aluminum alloy for driving the infrared solid-state imaging device is formed to complete the infrared solid-state imaging device.

The metal reflection film 108 is formed on the second surface of the semiconductor chip.
It is provided to improve the light receiving sensitivity (imaging sensitivity) with respect to infrared rays (light to be imaged) (arrow i in FIG. 13f) incident from the main surface side. That is, the incident infrared rays are incident on the Schottky junction portion 101 serving as a photoelectric conversion portion and photoelectrically converted into signal charges. However, since the Schottky junction portion 101 is extremely thin, only one incident light ray is photoelectrically converted at this time. It is a part, and the rest passes. However, the infrared light that has passed through the Schottky junction 101 is reflected by the metal reflection film 108 and is guided back into the original Schottky junction 101. In this way, the light receiving sensitivity can be improved.

The metal reflection film 108 formed on the photoelectric conversion portion 101 may be made of any material capable of internally reflecting incident light such as aluminum or aluminum alloy on the surface of the insulating film 107.

The size of the metal reflection film 108 is as shown in FIG.
3f, as shown in FIG. 1b, in particular the isolation region 10
It is not necessary to extend to 4 and it is sufficient that it extends at least outside the peripheral edge of the metal silicide layer of the photoelectric conversion portion. That is, like the metal reflection film 108B shown in FIG. 2, it may be provided so as to cover the entire surface of the insulating film 107 (the same effect). here,
In FIG. 2A, only the vicinity of the central region of the light receiving region is shown so that the state under the metal reflection film 108B can be seen.

When the metal reflection film 108B is provided over the entire surface, a step such as patterning after vapor-depositing aluminum or aluminum alloy on the insulating film 107 becomes unnecessary, so that the size is limited (FIG. 1). In comparison, there is an advantage that the manufacturing process of the device is simple (simple).

Further, the above-mentioned "reflow treatment" is a step necessary for preventing disconnection or short circuit of the metal reflection film, but it is sensitive to small irregularities of the base (insulating film 107). It is very difficult to form the receiving metal reflection film without any disconnection or short circuit.
Therefore, the smaller the area of the formed metal reflective film, the better the yield.

That is, the metal reflection film formed over the entire surface of the device (FIG. 2) has a simple manufacturing process, but for example, as shown in FIG. 1, the size is limited (for each row of light receiving cells). The yield is better if it is formed by connecting to the above.

Although omitted in the manufacturing process described above,
Usually, in the final stage of the process, the silicon substrate 102 is cleaned by spraying a jet of pure water having a high specific resistance. At this time, static electricity is often generated in the metal reflection film 108 and the like, and is often negatively charged. Further, when the completed device is washed or dried, and also when it is attached to the camera, static electricity is similarly generated and charged to a negative potential.

In the present embodiment, the voltage applied from the voltage applying means 109 to the substrate is 5 V to 30 V with respect to the metal reflection film 108.
By applying a voltage in the range of V, preferably a voltage of 10V to 15V, such static electricity is removed and no white scratch is generated. Further, since the size of the metal reflection film is extended to a region wider than the peripheral edge of the photoelectric conversion portion, it is possible to effectively prevent the occurrence of white scratches, and the device has good white scratch durability. .

Of course, even when the completed device is attached to, for example, a camera and the image is picked up, the metal reflection film is fixed at a positive potential with respect to the p-type substrate. Does not occur.

As described above, according to this embodiment, the metal reflection film facing the Schottky junction as the photoelectric conversion portion is extended to the element isolation region of each light receiving cell, and is positive with respect to the p-type semiconductor substrate. Since the electric potential is maintained, the junction breakdown voltage at the Schottky junction of the photoelectric conversion portion is improved, and as a result, the dark current is reduced. That is, white scratches do not occur, the durability against white scratches is good, and the light receiving characteristics between the photoelectric conversion units can be kept uniform.

(Second Embodiment) Next, a second embodiment of the infrared solid-state imaging device according to the present invention will be described below with reference to FIG. FIG. 3a is a schematic view similar to FIG. 1a of the first embodiment, regarding the plane configuration of the apparatus. In the present embodiment, a metal thin film is further provided on the metal reflection film on the photoelectric conversion portion. In FIG. 3A, the metal reflection film is shown as a rightward hatching portion 208, and the metal thin film is shown as a cross hatching portion 211. Has been done. Here, the metal thin film 211 in FIG. 3A is shown only in the vicinity of the central region so that the state below it can be seen.

The metal reflection film 208 is formed individually for each light receiving cell. The peripheral edge of each metal reflection film 208 is
As in the first embodiment, it extends to the element isolation region 204 and covers the photoelectric conversion unit and a region including the guard ring region surrounding the photoelectric conversion unit. On the other hand, the metal thin film 211 is
It has a width narrower than that of the photoelectric conversion portion in the horizontal direction and is formed continuously over three light receiving cells arranged in the vertical direction. Of course, this may be formed continuously in the horizontal direction.

Further, the metal reflection film 208 and the metal thin film 211 are insulated from each other by the insulating film provided between them, but only by the through holes of the insulating film existing in the blackened portion 210 in the figure. It is conducted.
That is, the metal reflection films 208 arranged in the vertical direction are
The metal thin film 211 is commonly connected through the through holes 210.

FIG. 3b shows a part of the structure near the surface of the substrate in the cross section AB of FIG. 3a. In FIG. 3B, the photoelectric conversion unit 201 formed on the first main surface side of the semiconductor substrate 202.
Are surrounded by a guard ring region 203, and the outer periphery thereof is surrounded by an element isolation region 204. on the other hand,
The vertical charge transfer unit includes light receiving cells (201, 203 to 20).
4) a vertical charge transfer path 205 formed in the interval region,
The transfer electrode 206 and the like are formed thereon.

Further, a first insulating film 207 is provided to cover the light receiving cells and the vertical charge transfer portion, and the metal reflection film 208 is provided on the photoelectric conversion portion 201 via the first insulating film 207. Is provided. This metal reflection film 20
Unlike the conventional infrared solid-state image pickup device, 8 covers the guard ring region 203 surrounding the photoelectric conversion unit 201 and extends to the element isolation region 204.

Then, a second film is formed on the metal reflection film 208.
The metal thin film 211 is formed via the insulating film 209. A through hole 210 reaching the metal reflection film 208 is formed in the second insulating film 209, and the metal thin film 211 and the metal reflection film 208 are electrically connected to each other through the through hole 210. As shown in FIG. 3b, the metal thin film 211 of the present embodiment is formed smaller than the photoelectric conversion part, and functions as a terminal for applying the potential applied to the metal thin film 211 from the outside to the metal reflective film 208. is there.

A voltage is applied to the metal thin film 211 from the outside by the voltage applying means 212, and when the conductivity of the semiconductor substrate 202 is p-type, the metal reflection film 208 with respect to the potential of the substrate. Is fixed so that the potential of is a relatively positive potential. Here, the metal reflection film 208 is individually formed for each light receiving cell, but is commonly connected in the vertical direction in a plane by a metal thin film 211 terminal provided thereon, and a voltage is applied. Therefore, the above-mentioned power supply is facilitated.

From the experimental results, it has been found that the positive potential is preferably in the range of 5 V to 30 V with respect to the semiconductor substrate 202. Further, if the positive potential is in the range of 10 V to 15 V, it can be used in common with the power supply voltage of the circuit used for driving the charge transfer section (205 etc.), which is advantageous in terms of cost and is more preferable.

As described above, in the infrared solid-state image pickup device of this embodiment, the metal reflection film 2 provided on the photoelectric conversion unit 201 is used.
Not only is 08 fixed to the above potential through the metal thin film 211 terminal, but its size is limited as in the first embodiment. That is, the peripheral edge of the metal reflection film 208 extends to the element isolation region 204, and the region including the photoelectric conversion unit 201 and the guard ring region 203 surrounding the photoelectric conversion unit 201 is covered by the metal reflection film 208.

Therefore, as clearly shown by the results of the above-mentioned high-temperature storage test, the apparatus of this embodiment can not only prevent the occurrence of white scratches, but also have good durability against white scratches and are more effective. It is possible to prevent the occurrence of white scratches.

With respect to the method of manufacturing the infrared solid-state imaging device of the second embodiment having the above-described structure, sectional views 10a to 10e showing the formation state at each stage of the manufacturing method, and FIG.
A description will be given below with reference to ac.

= First Half Step (FIGS. 10A to 10E) = As in the first embodiment, a p-type silicon semiconductor is used as the semiconductor substrate, and the element isolation region 204 and the vertical charge transfer path 2 are used.
05, the CCD transfer electrode 206 is formed. After that, the guard ring region 203, various thermal diffusion layers (not shown), and other polysilicon electrodes (not shown) are formed to obtain the sectional structure shown in FIG. 10a. In this state, both the polysilicon electrode and the region to be the photoelectric conversion portion are thin oxide films 213 and 21.
It is covered with 4. Up to this point, the manufacturing process and the sectional structure are the same as those of the first embodiment.

Subsequently, in the second embodiment, a photolithography process for forming a photoelectric conversion portion is performed. That is,
A resist 215 is applied, and then exposure / development processing is performed to perform patterning for removing the oxide film 214 in a region to be a photoelectric conversion portion. The state at the end of this patterning is shown in FIG. 10b. At this time, the region other than the region (device active region) that becomes the photoelectric conversion unit is protected by the resist 215.

Next, by wet etching, a hole is formed in the oxide film 214 to expose the surface of the silicon substrate 202 in the region to be the photoelectric conversion portion. The state at this time is shown in FIG.
It is shown in c. At this stage, only the thin oxide film 214 (gate oxide film) having a thickness of 200 nm or less is removed by etching. Therefore, the amount of side etching is extremely small.

In the case of this embodiment, the dimension L ₁ (transfer electrode 20
The size required to protect 6) is 0.5
It may be set to about μm. Therefore, when the width dimension W of the element active region to be formed in the light receiving cell is, for example, 10 μm, the width dimension L _{2 of the} region actually formed as the photoelectric conversion portion in this embodiment is about 9 μm. When this is compared with the width L ₂ obtained by the method of manufacturing the device of the first embodiment (FIG. 13c) (hereinafter referred to as the conventional manufacturing method), even if the unit pixel size is the same, it is shown in FIG. 13c. Compared with the method (L ₂ = 6 to 7 μm), the method of this embodiment can significantly increase the effective area of the photoelectric conversion unit.

After that, the resist 215 is peeled off and washed, and then the photoelectric conversion portion 201 is formed. Also in this embodiment, the photoelectric conversion unit 201 is a Schottky barrier diode, and the same configuration and forming method as in the first embodiment apply.

Next, as shown in FIG.
An insulating film 207 obtained at a relatively low temperature of about C or less is laminated on the entire surface. The insulating film 207 can be selected from various materials such as an oxide film, an oxynitride film, or a nitride film formed by an atmospheric pressure CVD method, a plasma CVD method, a low pressure CVD method, a sputtering method, or the like.

After that, the insulating film 20 on the photoelectric conversion portion 201 is formed.
A metal reflection film 208 is formed on the surface of 7 by, for example, aluminum or an aluminum alloy so that its peripheral edge extends to the element isolation region 204. The state at this time is shown in FIG. 10e.

The device of this embodiment obtained in the above manufacturing process (first half) is a device in which the effective area of the photoelectric conversion portion is greatly expanded as compared with the device of the first embodiment. Generally, in order to simultaneously satisfy the requirements for the solid-state imaging device, such as reduction in chip size, improvement in spatial resolution (increased pixel density) and improvement in light-receiving sensitivity, the area occupied by the photoelectric conversion unit in the unit pixel of the solid-state imaging device It is necessary to increase the ratio (aperture ratio). In other words, it is necessary to reduce the area of the region that does not affect the sensitivity characteristics of the solid-state imaging device.

As one method to meet such a demand, it is conceivable to reduce the width of the element isolation region 204 and further reduce the dimension L ₁ as much as possible. However, in the conventional manufacturing method, the large side etching of the relatively thick CVD oxide insulating film 112 is unavoidable as shown in FIG. 13C, so that the dimension L ₁ cannot be reduced and the light receiving sensitivity is improved. It was difficult.

On the other hand, in the method of manufacturing the infrared solid-state imaging device of this embodiment, the surface of the semiconductor substrate in the region for forming the photoelectric conversion portion is exposed without stacking the thick CVD oxide insulating film 112 of the conventional method. To be done. That is, in the wet etching step of exposing the surface of the semiconductor substrate, only the thin thermal oxide film (usually about 50 to 150 nm) grown on the surface of the region to be the photoelectric conversion portion may be removed. Therefore, the amount of side etching can be suppressed to be extremely small (0.1 to 0.3 μm).

As described above, in the method of manufacturing the device of this embodiment, the peripheral edge of the opening of the photoelectric conversion portion 201 can be brought as close as possible to the element isolation region 204 around the light receiving cell, and as a result, the device is manufactured by the conventional method. A solid-state imaging device structure can be obtained in which the area aperture ratio of the photoelectric conversion unit in the unit pixel is significantly increased as compared with the imaging device (for example, FIG. 1 of the first embodiment).

Furthermore, in the method of manufacturing the infrared solid-state image pickup device of this embodiment, the thick CVD oxide insulating film 112 (FIG. 13c) of the conventional method is not laminated. Therefore, the “reflow treatment” step performed on the insulating film 112 is not necessary. The image pickup apparatus of the present embodiment obtained by this manufacturing method capable of omitting this step can be obtained very easily as compared with the first embodiment.

Therefore, the photoelectric conversion portion 201 is formed without the intervention of the flattened insulating film 112 obtained by the “reflow treatment”, that is, without being flattened, and then the insulating film covering the entire surface is formed. 207 is provided. Therefore, the metal reflection film 208 is the insulating film 207.
Will be formed on the non-planarized surface of the (FIG. 10e). However, in this embodiment, the metal reflection film 208
Is formed for each unit pixel, there is almost no problem such as disconnection or short circuit of the metal reflection film 208.

Here, the first shown in FIG. 1 or FIG.
When the continuous area of the metal reflection film extends over a plurality of light receiving cells as in the embodiment, a problem due to disconnection / short circuit occurs, and therefore, the manufacturing method of the present embodiment omitting the “reflow treatment” step is used. However, the yield is very poor and cannot be used.

= Second Half Step (FIGS. 11A to 11C) = Next, a flat insulating film 209, which is obtained at a relatively low temperature of about 500 ° C. or less and is now flat, is formed on the entire surface. FIG. 11a shows
The state where the insulating film 209 is formed and the surface thereof is flattened is shown. The insulating film 209 is mainly composed of a polyimide film formed by spin-coating a liquid polyimide resin and heat-treating it, a spin-on-glass (SGO) film, or an oxide film formed by a CVD method, particularly tetraethoxysilane (TEOS). The CVD oxide film can be selected from various materials.

A through hole 210 having a relatively small diameter reaching the metal reflection film 208 is formed in each light receiving cell of the insulating film 209 by using a normal photolithography technique (FIG. 11).
b). Subsequent to the formation of the through holes 210, a metal thin film 211 made of aluminum or an aluminum alloy is formed on the flattened surface of the insulating film 209 by a photolithography method so as to bridge the through hole 210 portions (FIG. 11c). ). Finally, a metal wiring layer (not shown) for driving the infrared solid-state imaging device is formed, and the device is completed.

The metal thin film 21 formed in this embodiment.
As shown in FIG. 3a, one terminal is continuously formed over, for example, three light receiving cells arranged in the vertical direction. As described above, the surface of the second insulating film 209, which is the base on which the metal thin film 211 is formed, is very flat even over a plurality of light receiving cells, and problems such as disconnection and short circuit hardly occur.

Therefore, the metal reflection film 208 does not need to be formed vertically over a plurality of light receiving cells as in the first embodiment, but is formed separately for each light receiving cell as shown in FIG. 3a. It is a thing. As described above, the base on which the metal reflection film 208 is formed is in a state where surface irregularities are severe, and even after the flattening step by the "reflow process" as in the conventional method, there were many failures in formation due to disconnection or the like. Here, since the area of the metal reflection film 208 can be reduced, the yield is improved.

The infrared solid-state image pickup device obtained by the manufacturing method of this embodiment described above has a complicated structure as compared with the first embodiment. However, as described above, since the "reflow treatment" is not performed in the first half step, it can be easily manufactured. Furthermore, as described above, the device obtained as a result has a large area ratio (aperture ratio) occupied by the photoelectric conversion unit in the unit pixel. Therefore, it is possible to simultaneously satisfy the requirements for the solid-state imaging device, such as reduction in chip size, improvement in spatial resolution (increase in pixel density), and improvement in light receiving sensitivity.

Similar to the first embodiment, the metal reflecting film 208 is a reflecting surface for infrared light incident from the second main surface side of the silicon substrate, and is provided for improving the light receiving sensitivity. The size of the metal reflection film 208 is as shown in FIG.
As shown in FIG. 3B, there is no particular need to extend to the element isolation region 204, as long as it extends at least outside the peripheral edge of the metal silicide layer of the photoelectric conversion portion.

After the completion of the device, the voltage applying means applies a voltage higher than the potential of the p-type substrate by 5 V to 30 V, preferably 10 V to 15 V to the metal thin film, and the potential thereof is increased. It is given to the metal reflection film through the through hole. In this way, cleaning during manufacturing, cleaning and drying after completion,
Alternatively, since static electricity generated at the time of attachment to the camera is removed, white scratches do not occur.

Furthermore, since the size of the metal reflection film is extended to a region wider than the peripheral edge of the photoelectric conversion portion, it is possible to effectively prevent the generation of white scratches and the device has good white scratch durability. Became. Further, even when the apparatus is in use (during image capturing), since the above-mentioned potential is similarly applied to the metal reflection film, white scratches do not occur on the image.

As described above, according to the present embodiment, the metal reflection film facing the Schottky junction as the photoelectric conversion portion is extended to the element isolation region of each light receiving cell, and the positive potential with respect to the semiconductor substrate. Therefore, the junction breakdown voltage in the Schottky junction of the photoelectric conversion part is improved, and as a result, the dark current is reduced. In other words, not only white scratches do not occur, but also the durability against white scratches is good, and the light receiving characteristics between the photoelectric conversion units can be kept uniform.

(Third Embodiment) Next, a third embodiment of the infrared solid-state imaging device according to the present invention will be described below with reference to FIG. FIG. 4a is a schematic view of a plane configuration of the device, similar to the above-described embodiment. In this embodiment, similar to the second embodiment, a metal reflection film and a metal thin film are provided on the photoelectric conversion portion, and are shown as a rightward hatching portion 308 and a cross hatching portion 311A in FIG. 4a, respectively. . Here, the metal thin film 311A in FIG.
Shows only the vicinity of the central region so that the situation below can be seen.

The metal reflection film 308 is individually formed for each light receiving cell. The peripheral edge of each metal reflection film 308 is
Unlike the first and second embodiments, the metal reflective film 308 extends only up to the peripheral edge of the photoelectric conversion unit and faces the guard ring region 303 surrounding the photoelectric conversion unit.
Does not exist.

However, the metal thin film 311A has its peripheral edge extended to the element isolation region 304. That is, the metal thin film 311A covers a region including the photoelectric conversion unit and the guard ring region 303 surrounding the photoelectric conversion unit. Further, the metal thin film 311A is continuously formed over three light receiving cells arranged in the vertical direction. This may of course be formed continuously in the horizontal direction.

Further, the metal reflection film 308 and the metal thin film 311A are insulated from each other by the insulating film provided between them, but the blackened portion 310 in the figure.
Is conducted only by the through holes of the insulating film existing in the. That is, the metal reflection films 308 arranged in the vertical direction.
Is a metal thin film 311A through each through hole 310.
It is configured to be commonly connected to.

FIG. 4b shows a part of the structure near the surface of the substrate in the section AB of FIG. 4a. In FIG. 4B, the photoelectric conversion unit 301 formed on the first main surface side of the semiconductor substrate 302.
Is surrounded by a guard ring region 303 and further surrounded by an element isolation region 304. on the other hand,
The vertical charge transfer unit includes light receiving cells (301, 303 to 30).
4) a vertical charge transfer path 305 formed in the interval region,
The transfer electrode 306 and the like formed thereon are included.

Further, a first insulating film 307 is provided to cover the light receiving cells and the vertical charge transfer portion, and the metal reflection film 308 is provided on the photoelectric conversion portion 301 via the first insulating film 307. Is provided. This metal reflective film 30
Unlike the first and second embodiments, the reference numeral 8 covers only the photoelectric conversion unit 301 as in the conventional infrared solid-state imaging device (FIG. 9).

On the metal reflection film 308, a second film is formed.
The metal thin film 311 is formed via the insulating film 309. The second insulating film 309 has a through hole 310 reaching the metal reflection film 308, and the metal thin film 311A and the metal reflection film 308 are electrically connected to each other through the through hole 310. In addition, the metal thin film 311 of this embodiment covers the guard ring region 303 surrounding the photoelectric conversion unit 301 and extends to the element isolation region 304 as shown in FIG. 4B. That is, the metal thin film 311A of the present embodiment is the same as the metal thin film 311 from the outside.
It functions not only as a terminal for applying the potential applied to A to the metal reflection film 308, but also as an electrode for eliminating white scratches.

A voltage is externally applied to such a metal thin film 311A by the voltage applying means 312, and when the conductivity of the semiconductor substrate 302 is p-type, the metal reflection film 308 with respect to the potential of the substrate. Is fixed so that the potential of is a relatively positive potential. Here, the metal reflection film 308
Are individually formed for each light receiving cell, and are commonly connected in a vertical direction in a plane by a metal thin film 311A provided thereon, and a voltage is applied. Therefore, the above-mentioned power supply is facilitated.

As described above, the positive potential is preferably in the range of 5V to 30V with respect to the semiconductor substrate 302, and more preferably in the range of 10V to 15V.

As described above, in the infrared solid-state image pickup device of this embodiment, the metal reflection film 3 provided on the photoelectric conversion section 301 is used.
08 and the metal thin film 311A are not only fixed to the above potential, but also the size of the metal thin film 311A is limited. That is, the peripheral edge of the metal thin film 311A extends to the element isolation region 304, and the region including the photoelectric conversion unit 301 and the guard ring region 303 surrounding the photoelectric conversion unit 301 is covered by the metal thin film 311A.

Therefore, as clearly shown by the results of the above-mentioned high temperature storage test, the apparatus of this embodiment can not only prevent the occurrence of white scratches, but also have good durability against white scratches and are more effective. It is possible to prevent the occurrence of white scratches.

The method of manufacturing the infrared solid-state image pickup device of the third embodiment having the above structure is almost the same as the case of manufacturing the device of the second embodiment described above. The difference is that FIG.
patterning of the metal reflective film in FIG.
It is the patterning of the metal thin film in c. That is, in this embodiment, the metal reflection film is formed smaller (about the same size as the photoelectric conversion portion) and the metal thin film is formed larger (size extending to the element isolation region) than in the second embodiment. .

First, since the surface of the insulating film (207 in FIG. 11), which is the base on which the metal reflection film is formed, is not flattened, the smaller the continuous area of the metal reflection film, the more frequently the disconnection or short circuit occurs. Becomes smaller and the yield is improved.
Since the size of the metal reflective film of the present embodiment is smaller than that of the second embodiment, this embodiment is less likely to fail in forming the metal reflective film for the above-mentioned reason.

On the other hand, although the size of the metal thin film is larger than that of the second embodiment, the surface of the insulating film (209 in FIG. 11) which is the base for forming the metal thin film is formed with the metal reflective film by the conventional method. The degree of flatness is higher than that of the surface of the flattening insulating film (107 in FIG. 13) by the reflow process, which is the underlying layer. Therefore, as in the present embodiment, the metal thin film is formed to be large so as to extend to the element isolation region, and even when continuously formed over a plurality of light receiving cells, problems such as disconnection and short circuit do not occur. It can be easily formed.

Further, when the image pickup apparatus of the present embodiment is compared with the apparatus of the first embodiment, the structure is complicated, but the formation is easy and the yield is good for the reasons described above.

The metal reflection film 308 functions as a reflection surface for infrared light incident from the second main surface side of the silicon substrate, as in the above-mentioned embodiment, and is provided for improving the light receiving sensitivity. ing. Therefore, as in this embodiment, if it has a size comparable to that of the photoelectric conversion portion, it can sufficiently function as a reflecting surface.

As shown in FIG. 4, the size of the metal thin film 311A does not need to extend particularly to the element isolation region 304, and extends at least outside the peripheral edge of the metal silicide layer of the photoelectric conversion portion. If you have. That is, like the metal thin film 311B shown in FIG. 5, it may be provided so as to cover the entire surface of the insulating film 309 (the same effect). Here, in FIG. 5a, only the vicinity of the central region of the light receiving region is shown so that the state under the metal thin film 311B can be seen.

When the metal thin film 311B is provided over the entire surface, a step such as patterning after vapor-depositing aluminum or aluminum alloy on the insulating film 309 is unnecessary, so that the size of the device is smaller than that when the size is limited. There is an advantage that the manufacturing process is simple. Also in this case, since the underlying insulating film is flat, there is no difficulty in manufacturing.

After the completion of the device, the voltage applying means applies a voltage higher than the potential of the p-type substrate by 5 V to 30 V, preferably 10 V to 15 V to the metal thin film, and the potential thereof is changed. It is given to the metal reflection film through the through hole. In this way, cleaning during manufacturing, cleaning and drying after completion,
Alternatively, since static electricity generated at the time of attachment to the camera is removed, white scratches do not occur.

Furthermore, since the size of the metal thin film is extended to a region wider than the peripheral edge of the photoelectric conversion portion, it is possible to effectively prevent the occurrence of white scratches and to provide a device having good white scratch durability. became. Further, even when the apparatus is in use (during image capturing), since the above-mentioned potential is similarly applied to the metal reflection film, white scratches do not occur on the image.

As described above, according to this embodiment, the metal thin film facing the Schottky junction as the photoelectric conversion portion is extended to the element isolation region of each light receiving cell, and a positive potential is applied to the semiconductor substrate. Since this is maintained, the junction breakdown voltage at the Schottky junction of the photoelectric conversion portion is improved, and as a result, the dark current is reduced. In other words, not only white scratches do not occur, but also the durability against white scratches is good, and the light receiving characteristics between the photoelectric conversion units can be kept uniform.

(Fourth Embodiment) Next, a fourth embodiment of the infrared solid-state imaging device according to the present invention will be described below with reference to FIG. First, FIG. 6a is a schematic view of the plane configuration of the device. In the figure, the hatching portion 4 is on the right
Reference numeral 08 represents a metal reflection film, and cross-hatched portion 411A represents a metal thin film. Here, the metal thin film 411A is shown only in the region near the center so that the state below it can be seen.

Metal reflection film 408 and metal thin film 411A
The formation area (range) of is similar to that of the third embodiment. That is, the metal reflection film 408 only covers the photoelectric conversion unit individually for each light receiving cell, and the metal thin film 411 on one side is covered.
A is a guard ring region 40 surrounding the photoelectric conversion unit and its periphery.
It covers the area including 3 and 3. Further, the metal thin film 411A is continuously formed over three light receiving cells arranged in the vertical direction.

FIG. 6b shows a part of the structure near the surface of the substrate in the section AB of FIG. 6a. In FIG. 6B, the photoelectric conversion unit 401 formed on the first main surface side of the semiconductor substrate 402.
Are surrounded by a guard ring region 403 and further surrounded by an element isolation region 404. on the other hand,
The vertical charge transfer unit includes light receiving cells (401, 403 to 40).
4) a vertical charge transfer path 405 formed in the interval region,
It is composed of the transfer electrode 406 and the like formed thereon.

Further, a first insulating film 407 for covering the light receiving cells and the vertical charge transfer portion is provided, and the metal reflection film 408 is provided on the photoelectric conversion portion 401 via the first insulating film 407. Is provided. This metal reflective film 40
Similar to the third embodiment, 8 covers only the photoelectric conversion unit 401. Then, a metal thin film 411A is formed on the metal reflection film 408 via a second insulating film 409 so as to cover the guard ring region 403 surrounding the photoelectric conversion unit 401 and extend to the element isolation region 404. Further, in plan view, it is formed continuously in the vertical direction.

Unlike the second embodiment, the metal thin film 411A is formed so as to be galvanically insulated from the metal reflection film 408 and capacitively coupled to the galvanic AC. . With this structure, the metal reflection film 408 is electrostatically shielded by the metal thin film 411A and the semiconductor substrate 402.

The voltage applied to the metal thin film 411A from the outside by the voltage applying means 412 is a constant voltage higher than the potential of the substrate when the conductivity of the semiconductor substrate 402 is p-type. Thereby, the metal reflection film 408
The potential of is always maintained at a certain positive potential with respect to the potential of the substrate by capacitive coupling with the metal thin film 411A.

The positive potential applied to the metal reflection film 408 is, as described above, preferably in the range of 5V to 30V with respect to the semiconductor substrate 402, and more preferably in the range of 10V to 15V. Here, in order to keep the potential of the metal reflection film 408 within the range of 10V to 15V, the metal thin film 41
A potential of about 15 to 20 V may be applied to 1 A.

However, as described above, the metal thin film 411A
The electric potential applied to the metal reflective film 408 is applied to the metal reflective film 408 by capacitive coupling. Therefore, to be precise, the potential of the metal reflection film 408 is equal to the distance between the metal thin film 411A and the metal reflection film 408 (that is, the film thickness of the second insulating film 409) or the distance between the metal reflection film 408 and the semiconductor substrate 402 (that is, the first thickness). It depends on the film thickness of the insulating film 407) and the dielectric constant of each insulating film.

Letting C _{1 be} the first capacitance between the silicon substrate and the metal reflection film, and C ₂ be the second capacitance between the metal reflection film and the metal thin film, these capacitances are equivalent. in will be connected in series, the potential V _c of the silicon substrate, the potential V _b of the metal reflection film, the relationship between the potential V _a of the metal thin film can be expressed by equation (1) above. Generally, the capacitance C of a parallel plate capacitor can be expressed by the following equation (2) using the dielectric constant ε _OX of the insulating film and the film thickness T _{OX of the} insulating film.

C = ε _OX / T _OX ··· Equation (2)

That is, if the dielectric constant ε _OX of each insulating film is constant, the smaller the film thickness T _OX , the larger the electrostatic capacitance, which is given to the metal reflection film 408 by capacitive coupling according to the equation (1). It is possible to increase the positive potential V _b that can be generated.
This will be described below using a specific example.

Here, for example, if the first and second insulating films are silicon oxide films, ε _OX = 3.5 × 10 ⁻¹³ (F /
cm). Therefore, each capacitance C ₁ and C ₂ is
It is determined depending on the spacing (thickness of the first insulating film) T _OX1 between the silicon substrate and the metal reflective film and the spacing (thickness of the second insulating film) T _OX2 between the metal reflective film and the metal thin film, respectively.

First, T _OX1 is 750 nm due to optical restrictions.
The degree is appropriate. Therefore, from the formula (2), the first capacitance is C ₁ = 4.7 × 10 ⁻⁹ (F / cm ² ). Then T
_{When OX2} is, for example, 500 nm, the second electrostatic capacitance is C ₂ = 7 × 10 ⁻⁹ (F / cm ² ) similarly. In the device having the above structure, when the potential V _a = 15V is applied to the metal thin film, the metal reflection film is kept at the potential V _b = 9V. Here, for simplification, the potential of the silicon substrate is set to V
_c = 0V.

The film thickness of the second insulating film is thinner than the above, and T
When _OX2 = 100 nm, a second capacitance C ₂ = 3.
It becomes 5 × 10 ⁻⁸ (F / cm ² ). In the device of this configuration, when the potential V _a = 15V is applied to the metal thin film as before, the metal reflection film is kept at the potential V _b = 13.2V, which is higher than the above (when the film thickness is 500 nm). Become.

On the other hand, even if each insulating film has the same film thickness T _OX , strong capacitive coupling can be realized by using a material having a higher dielectric constant ε _OX as the insulating film. Specifically, instead of the above-described insulating film formed of only a silicon oxide film, an insulating film formed of a silicon nitride film or a combination of a silicon nitride film and a silicon oxide film has a higher dielectric constant (silicon oxide film). (Since the silicon nitride film has a higher dielectric constant than that of).

As described above, in the infrared solid-state image pickup device of this embodiment, not only the metal reflection film 408 and the metal thin film 411A are fixed to the above potential, but also the metal thin film 411A.
Is limited in size. That is, the metal thin film 411
A peripheral edge of A extends to the element isolation region 404, and a region including the photoelectric conversion unit 401 and a guard ring region 403 surrounding the photoelectric conversion unit 401 is covered with the metal thin film 411A.

Therefore, as clearly shown by the results of the above-mentioned high-temperature storage test, the apparatus of this embodiment can not only prevent the occurrence of white scratches, but also have good durability against white scratches and are more effective. It is possible to prevent the occurrence of white scratches.

The method of manufacturing the infrared solid-state image pickup device having the above-mentioned structure according to the fourth embodiment is substantially the same as the method of manufacturing the device according to the second embodiment described above. The first half process up to the provision of the metal reflection film is the same as in the third embodiment except that the size thereof is reduced, and therefore the description thereof is omitted here. On the other hand, the latter half process after providing the metal reflection film will be described below with reference to the cross-sectional views 12a to 12d showing the formation state at each stage of the manufacturing method.

= Latter half step (FIGS. 12a to 12d) = First, in FIG. 12a, the metal reflection film 408 corresponds to the photoelectric conversion section 40.
The cross-sectional structure at the stage of being formed to the same size as 1 is shown. On top of this, a flat second insulating film 409 obtained at a relatively low temperature of about 500 ° C. or lower is formed on the entire surface. The second insulating film 409 is formed of the same material as the insulating film 209 of FIG. 11, and the description is omitted here. FIG. 12b shows a state in which the second insulating film 409 is formed and the surface thereof is flattened.

In the above-described third embodiment, there is a step for forming a through hole in the second insulating film 409 next, but the metal reflection film 408 of this embodiment is capacitively coupled with a metal thin film to be formed next. Since a positive potential is supplied by the metal reflection film 4
08 does not need to be electrically connected to the metal thin film, and therefore it is not necessary to provide a through hole in the second insulating film 409.

Therefore, next, the metal thin film 4 is formed on the second insulating film 409 by aluminum or aluminum alloy.
11B is formed (FIG. 12C), and thereafter, using a known photolithographic etching technique, this is patterned so as to extend to the element isolation region 404, and the metal thin film 411 is formed.
Form A (FIG. 12d). Thus, the device of this embodiment shown in FIG. 6b is completed.

As described above, the apparatus of the fourth embodiment has the third
Compared to the embodiment, the step of forming the through hole is omitted, and the manufacturing is easier. Further, it is not necessary to consider the yield reduction due to the formation of the through holes, and it is possible to provide an image pickup device excellent in mass productivity.

Here, the size of the metal thin film 411A is not particularly required to extend to the element isolation region 404, and it is sufficient that the metal thin film 411A extends at least outside the peripheral edge of the metal silicide layer of the photoelectric conversion portion. . Therefore, like the metal thin film 411B shown in FIG. 7, it may be provided so as to cover the entire surface of the second insulating film 409, and the same effect is obtained. Here, in FIG. 7a, the metal thin film 411B is shown only near the center of the light receiving region.

When the metal thin film 411B is provided over the entire surface, the patterning process for the metal thin film described above is unnecessary, and the formation of the metal thin film on the photoelectric conversion portion is completed at the stage of FIG. 12c. Therefore, there is an advantage that the manufacturing process is simplified as compared with the case where the size is limited.

After the completion of the device, the voltage applying means applies a voltage higher than the potential of the p-type substrate to the metal thin film, and capacitively couples the metal reflective film with a voltage of 5 or more than the potential of the p-type substrate.
The voltage is increased by a voltage in the range of V to 30V, preferably 10V to 15V. In this way, the white scratches do not occur because the effects of the electrostatic charge generated by the cleaning during manufacturing, the cleaning and drying after completion, and the static electricity generated at the time of attachment to the camera are removed.

Furthermore, since the size of the metal thin film is extended to a range wider than the peripheral edge of the photoelectric conversion portion, it is possible to effectively prevent the occurrence of white scratches and to provide a device with good white scratch durability. became. Further, even when the apparatus is in use (during image capturing), since the above-mentioned potential is similarly applied to the metal reflection film, white scratches do not occur on the image.

As described above, according to this embodiment, the metal thin film facing the Schottky junction as the photoelectric conversion portion is extended to the element isolation region of each light receiving cell, and a positive potential is applied to the semiconductor substrate. Since this is maintained, the junction breakdown voltage at the Schottky junction of the photoelectric conversion portion is improved, and as a result, the dark current is reduced. In other words, not only white scratches do not occur, but also the durability against white scratches is good, and the light receiving characteristics between the photoelectric conversion units can be kept uniform.

It is needless to say that the present invention is not limited to the embodiments described above. The metal silicide layer of the photoelectric conversion part is not limited to PtSi, but may be palladium silicide, indium silicide, or the like.

The charge reading section is not limited to the CCD, but may be any of MOS, CSD, CPD, and the like.

Further, it is apparent from the gist of the present invention that the metal reflection film may be any substance that is conductive and can reflect infrared light.

Furthermore, since the white flaw can be eliminated without increasing the impurity concentration of the guard ring diffusion layer formed around the Schottky junction of the photoelectric conversion portion, the overlap amount of the Schottky junction and the guard ring can be reduced. It is not necessary to increase the number, and it is possible to obtain an image pickup device with a high sensitivity and a high pixel density, in which the aperture ratio of the photoelectric conversion unit is improved.

Further, since the positive potential is applied to the metal reflection film, the electrostatic capacity of the photoelectric conversion section is increased. Therefore, it is possible to increase the maximum storage amount of electric charges generated by photoelectric conversion, and there is also an advantage that the dynamic range of photoelectric conversion characteristics of the photoelectric conversion unit can be expanded.

[0200]

As described above, according to the infrared solid-state image pickup device of the present invention, the photoelectric conversion portion can be effectively shielded and the white scratch can be eliminated. Also,
Not only that, the durability against white scratches is also good, and it is possible to configure an imaging device having uniform light receiving characteristics between the photoelectric conversion units.

Further, the aperture ratio of the photoelectric conversion part is greatly increased, and as a result, the light receiving sensitivity is improved. Therefore, the chip size can be further reduced and the spatial resolution is improved. An imaging device with high sensitivity and high pixel density can be configured.

[Brief description of drawings]

FIG. 1A is a schematic plan view of a light receiving region of an infrared solid-state imaging device according to a first embodiment of the present invention. FIG. b is a schematic diagram showing the structure of the cross section AB in FIG.

FIG. 2A is a schematic plan view of a light receiving region of an infrared solid-state imaging device according to the first embodiment of the present invention. FIG. b is a schematic diagram showing the structure of the cross section AB in FIG.

FIG. 3A is a schematic plan view of a light receiving region of a second embodiment in an infrared solid-state imaging device according to the present invention. FIG. b is a schematic diagram showing the structure of the cross section AB in FIG.

FIG. 4A is a schematic plan view of a light receiving region of a third embodiment of the infrared solid-state imaging device according to the present invention. FIG. b is a schematic diagram showing the structure of the cross section AB in FIG.

FIG. 5A is a schematic plan view of a light receiving region of an infrared solid-state imaging device according to a third embodiment of the present invention. FIG. b is a schematic diagram showing the structure of the cross section AB in FIG.

FIG. 6A is a schematic plan view of a light receiving region of a fourth embodiment of the infrared solid-state imaging device according to the present invention. FIG. b is a schematic diagram showing the structure of the cross section AB in FIG.

FIG. 7A is a schematic plan view of a light receiving region of an infrared solid-state imaging device according to a fourth embodiment of the present invention. FIG. b is a schematic diagram showing the structure of the cross section AB in FIG.

FIG. 8 is an explanatory diagram showing a schematic plane configuration of an infrared solid-state imaging device.

FIG. 9A is a schematic plan view of a light receiving area of a conventional infrared solid-state imaging device. FIG. b is a schematic diagram showing a structure in a cross section AB of FIG.

10A to 10E are process diagrams showing sectional structures at respective stages of the first half manufacturing process of the second to fourth examples in the infrared solid-state imaging device according to the present invention.

11A to 11C are process diagrams showing cross-sectional structures in respective stages of the second half of the manufacturing process of the second to third embodiments in the infrared solid-state imaging device according to the present invention.

12A to 12D are process drawings showing a sectional structure in each stage of the latter half of the manufacturing process of the fourth embodiment of the infrared solid-state imaging device according to the present invention.

13A to 13F are process drawings showing a cross-sectional structure in each stage of the manufacturing process of the first embodiment of the infrared solid-state imaging device according to the present invention.

[Explanation of symbols]

101, 201, 301, 401, 1: photoelectric conversion unit 102, 202, 302, 402, 2, 82: semiconductor substrate 103, 203, 303, 403, 3: guard ring region 104, 204, 304, 404, 4: Element isolation regions 105, 205, 305, 405, 5, 83: Vertical charge transfer paths 84: Horizontal charge transfer paths 106, 206, 306, 406, 6: Transfer electrodes 107, 207, 209, 307, 309, 407, 4
09, 7: Insulating films 108A, 108B, 208, 308, 408, 8: Metal reflective films 211, 311A, 311B, 411A, 411B: Metal thin films 109, 212, 312, 412: Voltage applying means 210, 310: Through holes 110, 111, 213, 214: Thermal oxide film 112: CVD oxide insulating film 113, 215: Resist 81: Light receiving cell 85: Output circuit 86: Bonding pad 87: Metal wiring

Claims (13)

[Claims] 1. A plurality of photoelectric conversion parts formed on a first main surface of a semiconductor substrate, an insulating film covering a region including the plurality of photoelectric conversion parts, and a plurality of photoelectric conversion parts of the semiconductor substrate on the plurality of photoelectric conversion parts. In order to reflect each light that has entered from the second main surface side opposite to the one main surface and has passed through each photoelectric conversion section in the direction in which it again enters the original photoelectric conversion section, A metal reflection film formed on the surface so as to face the plurality of photoelectric conversion units in a region wider than the periphery thereof, and the metal reflection film so as to hold the metal reflection film at a predetermined potential. An infrared solid-state image pickup device comprising: a voltage applying unit that applies a DC voltage from the outside. 2. The semiconductor substrate is a p-type semiconductor substrate, and the voltage applying means has a polarity that maintains the potential of the metal reflection film as the DC voltage at a positive potential relative to the potential of the semiconductor substrate. The infrared solid-state imaging device according to claim 1, wherein the DC voltage is applied. 3. The photoelectric conversion unit includes a Schottky junction formed of a semiconductor substrate and a Schottky electrode made of a metal silicide layer formed in contact with the semiconductor substrate. 2. The infrared solid-state imaging device according to 2. 4. The infrared solid-state imaging device according to claim 3, wherein the metal reflection film extends at least outside the peripheral edge of the metal silicide layer of the photoelectric conversion unit. 5. A plurality of photoelectric conversion units formed on a first main surface of a semiconductor substrate, a first insulating film covering a region including the plurality of photoelectric conversion units, and a semiconductor for the plurality of photoelectric conversion units. In order to reflect the respective lights that have entered from the second main surface side opposite to the first main surface of the substrate and passed through the respective photoelectric conversion units in the directions in which they re-enter the original photoelectric conversion units, A plurality of metal reflection films formed on the surface of the first insulating film so as to face each of the plurality of photoelectric conversion units in a region wider than the periphery thereof, and a region including the plurality of metal reflection films. A second insulating film that covers the top and has a flattened surface, and includes a plurality of through holes that reach the plurality of metal reflection films; and on the flattened surface of the second insulating film The plurality of penetrating holes are formed so as to face the plurality of metal reflection films. A metal thin film electrically connected to the plurality of metal reflective films via a metal thin film, and a voltage application for externally applying a DC voltage to the metal thin film so as to maintain the metal reflective film at a predetermined potential. An infrared solid-state imaging device comprising means. 6. The semiconductor substrate is a p-type semiconductor substrate, and the voltage applying means has a polarity that maintains the potential of the metal reflection film as the DC voltage at a positive potential relative to the potential of the semiconductor substrate. 6. The infrared solid-state image pickup device according to claim 5, wherein the DC voltage is applied. 7. The photoelectric conversion unit includes a Schottky junction formed of a semiconductor substrate and a Schottky electrode made of a metal silicide layer formed in contact with the semiconductor substrate. 6. The infrared solid-state imaging device according to item 6. 8. The infrared solid-state imaging device according to claim 7, wherein the metal reflection film extends at least outside the peripheral edge of the metal silicide layer of the photoelectric conversion section. 9. The infrared solid-state imaging device according to claim 7, wherein the metal thin film extends at least outside the peripheral edge of the metal silicide layer of the photoelectric conversion unit. 10. A plurality of photoelectric conversion units formed on a first main surface of a semiconductor substrate, a first insulating film covering a region including the plurality of photoelectric conversion units, and a semiconductor for the plurality of photoelectric conversion units. In order to reflect the respective lights that have entered from the second main surface side opposite to the first main surface of the substrate and passed through the respective photoelectric conversion units in the directions in which they re-enter the original photoelectric conversion units, A plurality of metal reflection films formed on the surface of the first insulating film so as to face each of the plurality of photoelectric conversion units in a region wider than the periphery thereof, and a region including the plurality of metal reflection films. A second insulating film that covers the upper surface and has a flattened surface; the second insulating film is formed on the flattened surface of the second insulating film so as to face the plurality of metal reflection films; With respect to the reflective film, the second insulating film causes direct current electrical A metal thin film that is capacitively coupled to the metal thin film and that is capacitively coupled in an AC electrical manner; An infrared solid-state image pickup device characterized by the above. 11. The semiconductor substrate is a p-type semiconductor substrate, and the voltage applying means has a polarity that maintains the potential of the metal reflection film as the DC voltage at a positive potential relative to the potential of the semiconductor substrate. 11. The infrared solid-state imaging device according to claim 10, wherein the DC voltage is applied. 12. The photoelectric conversion part includes a Schottky junction formed by a semiconductor substrate and a Schottky electrode formed of a metal silicide layer in contact with the semiconductor substrate. Alternatively, the infrared solid-state imaging device according to item 11. 13. The method according to claim 12, wherein at least one of the metal reflection film and the metal thin film extends to the outside of at least the peripheral edge of the metal silicide layer of the photoelectric conversion unit. Infrared solid-state imaging device.