JPH09318436A - Thermal-type infrared sensor and its manufacture as well as image sensor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-sensitivity temperature sensor by a method wherein a polycrystal silicon layer is formed on a semiconductor substrate and a Schottky barrier diode(SBD) in which a metal film or a metal silicide film is formed on its surface is used as a temperature sensor. SOLUTION: A W reflection layer 11 is formed on the surface of an n-type silicon substrate 1, a silicon nitride film 12 is formed on its whole face, and a base body 10B is formed. A silicon nitride film 13 is formed on it so as to be a bridge shape, and a polycrystal silicon layer 14 is formed on it. A platinum silicide layer 15 is formed in the center on the surface, and an SBD is formed. A guard ring 14G which is formed of an n-type diffusion layer is formed on the layer 14 in the circumference of a bonding face to the layer 15, and a p<+> type diffusion layer 14B is formed in its outside region. A silicon oxide film 18 is formed on the surface of the layer 14, and it is connected electrically to the ring 14G and the layer 14B by Ti interconnection layers 16A, 16B via contact holes 18A, 18B. A silicon nitride film 19 for protection is formed on their whole face, and a temperature sensor which uses the SBD of high sensitivity can be formed in an arbitrary place.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal infrared sensor, and more particularly to a thermal infrared sensor having a Schottky barrier diode as a temperature sensor in an infrared light receiving section.

[0002]

2. Description of the Related Art Infrared rays emitted from an object to be observed are received by an infrared ray receiving section, and a physical property value of the infrared ray receiving section which changes according to the intensity of the received infrared ray is detected to detect the infrared ray intensity. Thermal infrared sensors for detecting the temperature are known.
In such a thermal infrared sensor, a thermal infrared sensor has a Schottky barrier diode formed in its infrared light receiving portion and electrically detects a change in resistance value that changes according to a temperature change in the infrared light receiving portion. However, it is known, for example, from Japanese Patent Laid-Open No. 5-40064.

The thermal infrared sensor using this Schottky barrier diode as a temperature sensor portion utilizes that the reverse current flowing when a reverse bias is applied to the Schottky barrier diode changes depending on the temperature. It is a thing. In particular, in a Schottky barrier diode, when a bias is applied in the reverse direction, the dependence of the reverse current on the bias voltage is weak, so even if the bias voltage fluctuates during measurement, the fluctuation of the reverse current is small, It is possible to stably measure a current value that changes according to temperature.

Further, since the Schottky barrier diode can realize a high resistance change rate (ratio of voltage change to current change) with respect to temperature change, a high-sensitivity thermal infrared sensor can be achieved. JP-A-5-40
It is known from Japanese Patent Publication No. 064 and the like.

[0005]

By the way, in the thermal type infrared sensor, in order to largely change the temperature of the infrared light receiving portion when infrared light is incident, the infrared light receiving portion and the substrate (semiconductor substrate) are insulated from each other. As a structure, it is necessary to reduce the heat capacity of the infrared receiving section. However, Figure 1
As shown in FIG. 9 and FIG. 20, in a conventional thermal infrared sensor 100 using a Schottky barrier diode (SBD), a metal film or a metal silicide film (for example, platinum silicide) 1 that constitutes the Schottky barrier diode 1
Since 05 was directly formed on the silicon substrate (single crystal silicon) 101, the infrared light receiving portion 100A is integrated with the silicon substrate 101 to increase its heat capacity, and the sensor sensitivity of the thermal infrared sensor 100 can be improved. There wasn't. In FIGS. 19 and 20, 106A and 106B are aluminum wirings, 104G is a guard ring, 104B is a p ^{+ type} diffusion layer, and 102 and 103 are silicon nitride films.

By the way, the infrared receiving portion 100A directly formed on the silicon substrate 101 is replaced with the silicon substrate 10 concerned.
As a method for providing a heat insulating structure to the first example, after the infrared light receiving portion 100A is formed, the infrared light receiving portion 100A is covered with a protective film, and in this state, silicon under the infrared light receiving portion 100A is anisotropically etched. A method of providing a hole in the substrate 101 is also considered. However, according to this method, the hole formed by etching spreads outward so as to surround the infrared light receiving portion 100A, and in particular, the infrared image sensor in which the infrared light receiving portion 100A needs to be integrated at a high density. It was not suitable for application to.

The present invention has been made in view of the above circumstances, and a thermal infrared sensor in which the sensitivity of the temperature sensor portion is increased and the temperature dependency of the physical property value of the infrared light receiving portion is increased to improve the sensor sensitivity. It is also an object of the present invention to provide an image sensor in which the image sensor is highly integrated.

[0008]

In order to achieve the above object, in the thermal infrared sensor according to the invention of claim 1, a polycrystalline silicon layer is formed above a semiconductor substrate and the surface of the polycrystalline silicon layer is formed. A Schottky barrier diode is formed by forming a metal film or a metal silicide film, and the Schottky barrier diode is used as a temperature sensor unit.

According to a second aspect of the present invention, a void having a predetermined width is provided between the semiconductor substrate and the polycrystalline silicon layer, and the Schottky barrier diode is formed above the void. The invention according to claim 3 provides a bridge structure in which the polycrystalline silicon layer is supported on the void by one or more films forming an infrared ray receiving portion.

Further, the invention of claim 4 is such that at least one of the one or more films is an insulating film. or,
According to a fifth aspect of the invention, at least one of the one or more films is a wiring layer. According to the invention of claim 6, a concave portion having a predetermined depth is formed on the semiconductor substrate below the infrared ray receiving portion.

According to a seventh aspect of the present invention, an interlayer film having a predetermined width lower in thermal conductivity than the semiconductor substrate is provided between the semiconductor substrate and the polycrystalline silicon layer, and the interlayer film is provided above the interlayer film. The Schottky barrier diode described above is formed on. According to the invention of claim 8, a reflection layer for reflecting infrared rays is formed in a predetermined region of the semiconductor substrate located below the Schottky barrier diode.

According to a ninth aspect of the present invention, the reflecting layer is formed of a metal having a melting point higher than a temperature required in the step of forming the polycrystalline silicon layer. Claim 1
In the invention No. 0, the reflective layer is made of any metal of titanium, tungsten, or an alloy containing titanium and tungsten. The invention of claim 11 is
The height from the lower surface of the infrared ray receiving portion directly below the Schottky barrier diode to the surface of the reflective layer is set to n times the wavelength of the infrared ray (where n is an odd number).

According to the twelfth aspect of the present invention, in manufacturing a thermal infrared sensor, a sacrificial layer is formed on a semiconductor substrate, and a polycrystalline silicon layer is formed directly above the sacrificial layer or via one or more films. Is formed, a metal film is formed on the polycrystalline silicon layer to form a Schottky diode, and then the sacrificial layer is removed to form the bridge structure.

According to the thirteenth aspect of the present invention, in manufacturing the thermal infrared sensor, a concave portion having a predetermined depth is formed on the semiconductor substrate, the concave portion is filled with the sacrificial layer, and directly above the concave portion.
Alternatively, a polycrystalline silicon layer is formed via one or more films, a metal film is formed on the polycrystalline silicon layer to form a Schottky diode, and then the sacrificial layer is removed to A bridge structure is formed.

According to a fourteenth aspect of the present invention, the sacrifice layer is removed by wet etching.
According to the invention of claim 15, one of the one or more films constituting the infrared ray receiving portion is an infrared ray absorbing film. According to a sixteenth aspect of the invention, an image sensor is constructed by arranging a plurality of the thermal infrared sensors in a linear or planar shape.

(Operation) According to the first aspect of the present invention, the Schottky barrier diode composed of the polycrystalline silicon layer and the metal film or the metal silicide film on the polycrystalline silicon layer is used as the temperature sensor section. Therefore, a high-sensitivity thermal infrared sensor can be appropriately formed at a site where the polycrystalline silicon film can be formed, and the degree of freedom in designing the thermal infrared sensor is increased.

According to the second aspect of the present invention, the polycrystalline silicon film in which the Schottky barrier diode is formed is formed by the gap between the semiconductor substrate and the polycrystalline silicon layer.
A high heat insulation structure can be provided for the semiconductor substrate.
Further, according to the invention of claim 3, the Schottky barrier diode can be used as a temperature sensor part of a thermal infrared sensor having a bridge structure, which can obtain a high heat insulation structure between the infrared light receiving part and the semiconductor substrate.

Further, according to the invention of claim 4, since the portion constituting the Schottky barrier diode is supported on the semiconductor substrate by the insulating film having a relatively low thermal conductivity, the heat of the infrared light receiving portion is concerned. Conductance becomes small. Further, this insulating film can simultaneously function as a protective film for the infrared ray receiving portion. Further, according to the invention of claim 5, the wiring layer for electrically connecting the Schottky barrier diode and the semiconductor substrate can be used as a film for supporting the Schottky barrier diode.

Further, according to the invention of claim 6, a high heat insulating structure between the semiconductor substrate and the infrared ray receiving portion can be obtained by the concave portion provided in the semiconductor substrate. Further, according to the invention of claim 7, it is possible to easily achieve the heat insulating structure between the infrared receiving portion of the thermal infrared sensor and the semiconductor substrate. Further, according to the invention of claim 8, the infrared light transmitted through the infrared light receiving portion can be reflected by the reflecting layer and made incident on the infrared light receiving portion again.

Further, according to the invention of claim 9, the reflecting layer formed in advance on the semiconductor substrate is prevented from being melted in the subsequent manufacturing step of the polycrystalline silicon layer.
Further, according to the invention of claim 10, by using the metal film containing titanium having a high melting point, the reflection layer is prevented from being melted in the manufacturing process of the polycrystalline silicon layer.

Further, according to the invention of claim 11, the infrared rays transmitted through the infrared light receiving portion and the infrared rays reflected on the surface of the reflecting layer thereafter do not cancel each other.
The reflected infrared rays can be efficiently incident on the infrared light receiving section again. According to the twelfth aspect of the present invention, the Schottky barrier diode can be used as the temperature sensor unit only by removing the sacrificial layer formed in advance on the semiconductor substrate after forming the infrared light receiving unit of the thermal infrared sensor. The thermal infrared sensor having the bridge structure used can be formed.

According to the thirteenth aspect of the present invention, a concave portion is provided on the semiconductor substrate, and the sacrificial layer formed so as to fill the concave portion is removed after the infrared light receiving portion of the thermal infrared sensor is formed. A thermal infrared sensor having a bridge structure using a Schottky barrier diode as a temperature sensor unit can be formed only by doing so. According to the invention of claim 14, the sacrificial layer below the infrared ray receiving portion can be easily removed by highly isotropic etching.

According to the fifteenth aspect of the invention, the temperature change of the infrared ray receiving portion with respect to the incident infrared ray becomes large. or,
According to the invention of claim 16, an image sensor provided with a large number of highly sensitive thermal infrared sensors is achieved.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings. It should be noted that the first embodiment includes claims 1 to 5, and claims 8 to 1.
2. It corresponds to claims 14 to 16.

First, an outline of the thermal infrared sensor 10 will be described with reference to FIGS. 1 to 3. Incidentally, FIG. 2 shows the silicon nitride film 19 formed on the surface of the thermal infrared sensor 10.
FIG. 3 is a plan view showing a state in which the silicon oxide film 18 formed on the surface of the polycrystalline silicon layer 14 is removed. In the thermal infrared sensor 10 of the first embodiment, as shown in FIGS. 1 to 3, an infrared light receiving portion 10A is supported on a base body 10B (silicon substrate 1, silicon nitride film 12) by a bridge portion 10C. It has a bridge structure.

Further, at a position directly below the infrared light receiving portion 10A of the substrate 10B, a reflecting portion 10D (reflection layer 11) for reflecting the infrared light transmitted through the infrared light receiving portion 10A and absorbing it again by the infrared light receiving portion 10A. Are formed. In the thermal infrared sensor 10 having such a bridge structure, since the space S provided between the infrared light receiving portion 10A and the base body 10B provides a heat insulating structure between the infrared light receiving portion 10A and the base body 10B, an infrared ray having a certain strength is obtained. The temperature change of the infrared light receiving portion 10A when the incident light becomes large. Further, the reflecting portion 1
Due to the action of 0D, the infrared light that has once passed through the infrared light receiving portion 10A is reflected by the reflecting portion 10D and then absorbed by the infrared light receiving portion 10A, so that the infrared light can be efficiently absorbed.

A Schottky barrier diode (hereinafter abbreviated as "SBD") used as a temperature sensor portion is formed in the infrared light receiving portion 10A. This S
In the BD, when the temperature of the infrared light receiving unit 10A changes according to the intensity of the infrared light incident on the infrared light receiving unit 10A, the value of the reverse saturation current thereof changes according to the temperature change. Then, the intensity of the incident infrared ray can be obtained by detecting the value of the reverse saturation current.

As described in JP-A-5-40064, when an SBD is used in the thermal infrared sensor 10, a predetermined reverse bias is applied to the SBD so that a current other than the reverse saturation current is applied. So that it can be ignored,
From the exponential relational expression of the reverse saturation current to the temperature, the temperature change can be measured as in the thermistor.

Next, the detailed structure of the thermal infrared sensor 10 will be described with reference to FIGS. A reflection layer 1 made of tungsten is formed on the upper surface of the n-type silicon substrate 1.
1 is formed, and a silicon nitride film 12 is formed on the entire surface so as to cover the reflective layer 11. Thus,
The silicon substrate 1 and the silicon nitride film 12 form a base body 10B of the thermal infrared sensor 10, and the reflection layer 11 forms the reflection portion 10D.

An example in which tungsten is used as the metal forming the reflective layer 11 will be described below.
Not limited to this, other metals, for example, metals having a high melting point such as titanium or an alloy of titanium and tungsten may be used. On the other hand, a silicon nitride film 13 is formed in a bridge shape above the base body 10B, and the polycrystalline silicon layer 1 is formed on the upper surface thereof.
4 are formed.

A platinum silicide layer 15 is formed substantially in the center of the upper surface of the polycrystalline silicon layer 14 and forms an SBD with the polycrystalline silicon layer 14. In addition, a guard ring 14G made of an n-type diffusion layer is formed in the polycrystalline silicon layer 14 so as to surround the bonding surface with the platinum silicide layer 15, and a p ^{+ -type} diffusion layer is formed outside the guard ring 14G. The layer 14B is formed.

On the surface of the polycrystalline silicon layer 14, acid
The silicon oxide film 18 is formed, and the silicon oxide film 18 is formed.
Through the contact holes 18A and 18B provided in
And the wiring layers 16A and 16B made of titanium are respectively
Guard ring 14G, p above ⁺Electricity to the diffusion layer 14B
Connected. And cover all of these
A silicon nitride film 19 as a protective film and an infrared absorption layer
Are formed.

The height h1 of the lower surface 13A of the silicon nitride film 13 from the upper surface 11A of the reflecting layer 11 is
It is formed to be n times the wavelength λ of the infrared ray (where n is an odd number). As a result, the infrared light transmitted through the infrared light receiving portion 10A is reflected by the reflective layer 11 and then efficiently absorbed again by the infrared light receiving portion 10A. Further, in the figure, 1A and 1B are p ^{+ type} diffusion layers formed in advance on the silicon substrate 1, and the p ^{+ type} diffusion layers 1A and 1B are formed.
Through the contact holes 12A and 12B provided in the silicon nitride film 12, respectively.
6B, and on the other hand, it is electrically connected to the wiring (not shown) of the readout circuit formed on the silicon substrate 1.

Next, a method of manufacturing the thermal infrared sensor 10 having the above structure will be described with reference to FIGS. (1) A readout circuit (not shown) of the thermal infrared sensor 10 is formed in advance on the n-type silicon substrate 1 by a well-known semiconductor manufacturing technique, and then the silicon substrate 1 is used.
Of tungsten on the surface of, for example, by sputtering.
5 μm in thickness is formed, and this is patterned into a desired shape by etching using a well-known photolithography technique to form a reflection layer 11 made of tungsten. Next, a silicon nitride film 12 having a film thickness of 0.1 μm is formed on the upper surface by, for example, the plasma CVD method. Further, a liquid silica-based compound is spin-coated on the upper surface thereof, and then is baked (spin-on-glass method) to form the SOG film 2 (FIG. 4A).

(2) A resist is applied to the upper surface of the SOG film 2 formed as described above, and this is exposed / developed into a desired shape to form a mask 3, and the SOG film 2 is dry-etched using the mask 3. Then, the SOG film 2A having a desired shape is formed.
(FIG. 4B) (3) The mask 3 is removed, and S is formed on the upper surface of the formed SOG film 2A by the same spin-on-glass method as described above.
An OG film is formed, and then etching back is performed to form inclined portions 4A and 4A for eliminating the step between the SOG film 2A and the silicon nitride film 12. Thus, the inclined portions 4A and 4A cooperate with the SOG film 2A to form the sacrificial layer 5. In this case, the sacrifice layer 5 has a height h1 from the upper surface of the reflective layer 11 to the upper surface of the SOG film 5.
However, the height (= n × λ / 4: where n is an odd number, λ
Is the wavelength of the incident infrared ray), and its thickness is determined (FIG. 4C).

(4) A silicon nitride film of 0.3 μm is formed by, for example, a CVD method so as to cover the sacrifice layer 5, and is patterned to form a silicon nitride film 13 (FIG. 1, FIG.
(See FIG. 2). By the patterning at this time, the sacrificial layer 5 once covered with the silicon nitride is exposed again (shown by the one-dot chain line in FIG. 2). Then, on the upper surface thereof, a polycrystalline silicon film having an n-type impurity introduced so as to have a resistivity of 1 × 10 ¹⁶ Ωcm is formed, for example, by the CVD method to have a thickness of 1.0 μm, and this is covered with a resist. The resist is exposed / developed into a desired shape (the shape of the infrared light receiving portion 10A) to form a mask, and the polycrystalline silicon layer 14 having the desired shape is formed by dry etching using the mask. After removing the resist, a silicon oxide film 18 having a thickness of 0.1 μm is formed on the surface of the polycrystalline silicon layer 14 by thermal oxidation (FIG. 4D).

(5) Polycrystalline silicon with oxide film 18 formed
A desired mask is formed on the upper surface of the con layer 14 and is used.
Boron implantation by ion implantation (5
× 10 ^Fifteencm^-2). After removing the mask,
A mask is formed by the known photolithography technique, and
Inject arsenic by ion implantation using this
Enter (3 x 10^Fifteencm^-2), After removing the mask,
Annealed (900 ℃, 1 hour), guard ring
14G and p⁺Forming a diffusion layer 14B (FIG. 5)
(E)).

(6) Next, a resist is applied on the entire surface,
This is exposed / developed into a desired shape to form a silicon oxide film 18
Of a desired region (corresponding to the region of the polycrystalline silicon layer 14 where the SBD is formed) is exposed, and wet etching is performed in this state to expose the exposed silicon oxide film 18
Is removed. Further, platinum silicide is formed on the upper surface by 0.01 μm by, for example, a spatter method, and then,
The resist is removed (lift-off), and the platinum silicide film 15 is formed only in the desired region (FIG. 5).
(F)).

(7) Next, a resist is applied on the silicon nitride film 12 formed on the upper surface of the silicon substrate 1,
This is exposed / developed into a desired shape to form a mask, and the silicon nitride film 12 is formed by etching using the mask.
Contact holes 12A and 12B communicating with the p ^{+ type} diffusion layers 1A and 1B of the silicon substrate 1 are provided. Next, a resist is applied so as to cover at least the silicon oxide film 18, and this is exposed / developed to form a mask, and the guide ring 14G and the p ^{+ -type} diffusion layer 14B are formed by etching the silicon oxide film 18 using the resist. Contact holes 18A, 18B communicating with the. After removing the resist, titanium is formed to a thickness of 0.5 μm on the upper surface by, for example, a sputtering method, and the titanium is patterned into a desired shape by a known photolithography technique.
6A and 16B are formed (FIG. 5 (g)).

(8) Next, a silicon nitride film is formed to a thickness of 0.3 μm as a protective film and an infrared absorbing film by, for example, a CVD method, and this is patterned by a known photolithography technique to correspond to the infrared receiving portion 10A. A silicon nitride film 19 having a desired shape is formed in the desired region (FIG. 5 (h)). In this case as well, the entire surface of the sacrificial layer 5 is once covered with the silicon nitride film, but by the subsequent patterning, as shown by the chain line in FIG.
Part of it is exposed again.

(9) In this state, wet etching is performed to remove the sacrificial layer 5 to form a space S between the silicon nitride film 12 and the reflective layer 11 to form the bridge structure shown in FIGS. To get FIG. 6 shows a thermal infrared sensor 10 ′ according to a modified example of the first embodiment. This thermal infrared sensor 10 ′ has a silicon substrate 1 instead of the reflective layer 11.
The difference is that the metal wirings 11A and 11B formed in advance are used to reflect incident infrared rays. By using the metal wiring formed on the silicon substrate 1 instead of the reflective layer in this manner, the manufacturing process is simplified and the space below the thermal infrared sensor 10 ′ can be effectively used. High integration can be achieved when an image sensor is constructed using the thermal infrared sensor 10 '.

As the metal wiring, metal wiring provided in the read circuit of the image sensor can be considered. In this case, the metal wiring is formed of a metal having a high melting point, such as tungsten, which can sufficiently withstand the heat treatment in the subsequent semiconductor manufacturing process. Next, an image sensor 20 using the thermal infrared sensor 10 will be described with reference to FIG.
This will be described with reference to FIG.

Although not shown in the figure, the thermal infrared sensor 10 having the above-described structure is arranged in a two-dimensional lattice on the base 10B to form the image sensor 20. That is,
As shown in FIG. 7, the image sensor 20 is a MOS type image sensor, and in reality, one image sensor 20 has a large number of thermal infrared sensors 10, 10, 10.
Are arranged in the horizontal and vertical directions, and the thermal infrared sensor 10 arranged in each of the above constitutes each pixel of the image sensor 20. Note that FIG. 7 shows an example in which a total of four thermal infrared sensors 10a to 10d are arranged in two pixels in the horizontal and vertical directions for the sake of simplicity.

Hereinafter, description will be made with reference to FIG. The SBD 21 of the thermal infrared sensor 10a has a p-type MO for reading.
The drain of the S transistor (vertical switch) 25 is connected, the gate of the vertical switch 25 is connected to the vertical scanning circuit 31, and the source of the vertical switch 25 is connected to the vertical read line 37. In addition, the thermal infrared sensor 10
The drain of the vertical switch 26 is connected to the SBD 22 of b, the gate of the vertical switch 26 is connected to the vertical scanning circuit 31, and the source of the vertical switch 26 is connected to the vertical read line 38. In addition, the thermal infrared sensor 10
The drain of the vertical switch 27 is connected to the SBD 23 of c, the gate of the vertical switch 27 is connected to the vertical scanning circuit 31, and the source of the vertical switch 27 is connected to the vertical read line 37. In addition, the thermal infrared sensor 10
The drain of the vertical switch 28 is connected to the SBD 24 of d, the gate of the vertical switch 28 is connected to the vertical scanning circuit 31, and the source of the vertical switch 28 is connected to the vertical read line 38.

The drain of a horizontal output p-type MOS transistor (horizontal switch) 35 is connected to one end of the vertical read line 37, the gate of the horizontal switch 35 is connected to the horizontal scanning circuit 32, and the source of the horizontal switch 35 is an output. It is connected to the terminal 39. On the other hand, the drain of a horizontal output p-type MOS transistor (horizontal switch) 36 is connected to one end of the vertical read line 38, the gate of the horizontal switch 36 is connected to the horizontal scanning circuit 32, and the source of the horizontal switch 36 is an output terminal. It is connected to 39. A resistor 33 and a power supply 34 are connected between the output terminal 39 and the horizontal switches 35 and 36.

The horizontal scanning circuit 32 and the vertical scanning circuit 31
Are each constituted by a shift register or the like, and are each driven by a clock pulse and a start pulse. The horizontal scanning circuit 32 generates drive pulses Φ1 and Φ2, and outputs these to the horizontal switches 35 and 36, respectively. On the other hand, the vertical scanning circuit 31 generates drive pulses Φ11 and Φ12, which are
7 and 28, respectively.

The drive pulses Φ1 and Φ2 output from the horizontal scanning circuit 32 are supplied to the gates of the horizontal switches 35 and 36, respectively, and the on / off timings of the horizontal switches 35 and 36 are controlled. On the other hand, the driving pulses Φ11 and Φ12 output from the vertical scanning circuit 31
5 and 26, respectively, are supplied to the gates of the vertical switches 27 and 28, respectively.
8 is controlled.

By controlling the on / off timings of the horizontal switches 35, 36 and the vertical switches 25, 26, 27, 28 in this manner, the thermal infrared sensors 10a ...
10d and the output terminal 39 conduct at a predetermined timing.

Next, the operation of the image sensor 20 having the above structure will be described with reference to FIG. FIG. 8 is a timing chart showing temporal changes in the waveforms of the drive pulses Φ11, Φ12, Φ1, and Φ2 output from the vertical scanning circuit 31 and the horizontal scanning circuit 32 and the waveform of the output voltage Vout of the output terminal 39. .

First, at time t0, the vertical scanning circuit 3
When the drive pulse Φ11 from 1 is changed to the low level, the vertical switches 25 and 26 are turned on. Next, at time t
In 1, when the drive pulse Φ1 from the horizontal scanning circuit 32 is changed to the low level, the horizontal switch 35 is turned on. As a result, in synchronization with the conduction between the SBD 21 and the output terminal 39, the capacity of the SBD 21 is first precharged (charged) by the voltage V0 of the power supply 34. Therefore, the output voltage Vout of the output terminal 39 rises to V1,
When precharging is completed, it begins to fall. However, SB
When the reverse current IR of D21 is large, while the horizontal switch 35 is on (while Φ1 is at the low level), it drops only to the level of V2 = IR × R.
After that, at time t2, when the drive pulse Φ1 from the horizontal scanning circuit 32 is returned to the original high level, the horizontal switch 35 is turned off, and the output voltage Vout of the output terminal 39 becomes the level before the horizontal switch 35 was turned on. Return. At this time,
Reverse current I of the charge accumulated in the parasitic capacitance of the SBD 21
The discharge by R is started.

Next, at time t3, the horizontal scanning circuit 3
When the second drive pulse Φ2 is changed to the low level, the SBD 22 is precharged by the voltage V0 of the power supply 34 in synchronization with the turning on of the horizontal switch 36, as in the case described above. Therefore, the output voltage V of the output terminal 39
out rises to V1 and begins to fall when precharge ends. However, when the reverse current IR of the SBD 22 is large, V is maintained while the horizontal switch 36 is on.
2 = Only falls to the level of IR × R. After that, at time t4, the drive pulse Φ2 from the horizontal scanning circuit 32.
Is returned to the original high level, the horizontal switch 36 is turned off, and the output voltage Vout of the output terminal 39 changes to the horizontal switch 3
Return to the level before 6 was turned on. At this time, discharge of the electric charge accumulated in the parasitic capacitance of the SBD 22 by the reverse current IR is started. After that, the drive pulse Φ11 from the vertical scanning circuit 31 is returned to the original high level (time t5).

Next, at time t10, the vertical scanning circuit 3
When the drive pulse Φ12 from 1 is changed to the low level, the vertical switches 27 and 28 are turned on. Next, at time t
11, the driving pulse Φ1 from the horizontal scanning circuit 32
When is changed to a low level, the horizontal switch 35 is turned on. As a result, in synchronization with the conduction of the SBD 23 and the output terminal 39, first, the capacity of the SBD 23 is changed to the power source 3
It is precharged by the voltage V0 of 4. For this reason,
The output voltage Vout of the output terminal 39 rises to V1 and begins to drop when precharge is completed. However, SBD2
When the reverse current IR of 3 is large, the horizontal switch 3
While 5 is on, it only drops to the level of V2 = IR × R. After that, at time t12, when the drive pulse Φ1 from the horizontal scanning circuit 32 is returned to the original level, the horizontal switch 35 is turned off, and the output voltage Vout of the output terminal 39 is output.
Returns to the level before the horizontal switch 35 was turned on. At this time, discharge of the charges accumulated in the parasitic capacitance of the SBD 23 by the reverse current IR is started.

Next, at time t13, the horizontal scanning circuit 3
When the second drive pulse Φ2 is changed to the low level, the SBD 24 is precharged by the voltage V0 of the power supply 34 in synchronization with the turning on of the horizontal switch 36, as in the case described above. Therefore, the output voltage Vo of the output terminal 39
ut rises to V1 and begins to fall when precharge ends. However, when the reverse current IR of the SBD 24 is large, V is maintained while the horizontal switch 36 is on.
2 = Only falls to the level of IR × R. After that, at time t14, the drive pulse Φ from the horizontal scanning circuit 32.
When 2 is returned to the original high level, the horizontal switch 36 is turned off, and the output voltage Vout of the output terminal 39 changes to the horizontal switch 3
Return to the level before 6 was turned on. At this time, discharge of the electric charge accumulated in the parasitic capacitance of the SBD 24 by the reverse current IR starts. After that, the drive pulse Φ12 from the vertical scanning circuit 31 is returned to the original high level (time t15).

The operation described above is repeated after time t20. That is, at time t20, the vertical scanning circuit 31
The drive pulse Φ11 from is changed to the low level, and the vertical switches 25 and 26 are turned on. Next, at time t21, the drive pulse .PHI.1 from the horizontal scanning circuit 32 is changed to the low level, and the horizontal switch 35 is turned on. As a result, in synchronization with the conduction between the SBD 21 and the output terminal 39, first, the capacity of the SBD 21 changes to the voltage V0 of the power source 34.
Precharged by.

At this time, the electric charge accumulated in the SBD 21 at the time t2 is discharged from the time t2 to the time t21, and only the electric charge corresponding to the remaining electric charge remains precharged. By the way, SBD21
The reverse current IR of is larger as the temperature of the SBD 21 is higher, and is smaller as the temperature is lower. Therefore, the amount of the accumulated charges discharged within the predetermined time also increases as the temperature increases, and decreases as the temperature decreases. Therefore, the above value V1 of the output voltage Vout of the output terminal 39 when precharged to the SBD 21 is
It will change according to the temperature.

Although not described here, the SBD 22-
Also in the case of 24, the output voltage V1 corresponding to those temperatures can be obtained respectively in the same manner as the above case. Therefore, by sampling and holding the value V1 of the output voltage Vout of the output terminal 39, the infrared light receiving portions 10A and 10A of the thermal infrared sensors 10a to 10d are sampled and held.
An infrared image can be obtained by detecting the temperatures of A, ... In this case, the period from time t1 to time t21 is the accumulation time (discharge time), which is about 1/60 second.

(Second Embodiment) Next, a second embodiment will be described with reference to FIGS. 9 to 13. This second embodiment corresponds to claims 1 to 6, claims 8 to 11 and claims 13 to 15.

First, an outline of the thermal infrared sensor 40 will be described with reference to FIGS. 9 to 11. 10 is a plan view showing a state in which the silicon nitride film 49 formed on the surface of the thermal infrared sensor 40 and the silicon oxide film 48 formed on the surface of the polycrystalline silicon layer 44 are removed. As shown in FIGS. 9 to 11, the thermal infrared sensor 40 has a bridge structure in which the infrared light receiving portion 40A is supported by the bridge portion 40C on the base body 40B. Further, in the base body 40B immediately below the infrared light receiving section 40A, the recess 40 having a predetermined depth d is formed.
E is formed. In addition, in FIG.
0A and the bridge portion 40C are indicated by thick lines.

Further, at the bottom of the recess 40E, there is formed a reflection layer (reflecting portion) 41 for reflecting the infrared light transmitted through the infrared light receiving portion 40A and absorbing it again by the infrared light receiving portion 40A. The thermal infrared sensor 40 having such a bridge structure includes an infrared light receiving portion 40A and a base body 40B.
The space S provided between the infrared receiver 40A and the base 40B provides a heat insulating structure between the infrared receiver 40A and the base 40B, so that the temperature change of the infrared receiver 40A with respect to the incident infrared light having a certain strength increases. In particular, by providing the concave portion 40E in the base body 40B, the void S can be made large, so that the heat insulating effect can be enhanced.

Further, due to the function of the reflecting layer 41, the infrared rays that have once passed through the infrared receiving section 40A are reflected by the reflecting layer 41 and then absorbed by the infrared receiving section 40A. Also in this case, since the depth d of the recess 40E to the upper surface 41A of the reflective layer 41 can be appropriately set, infrared rays can be efficiently absorbed by the infrared light receiving section 40A again, as described later.

Also in the thermal infrared sensor 40, as in the thermal infrared sensor 10, a Schottky barrier diode (SBD) is used as the temperature sensor unit to reduce the reverse saturation current IR of the SBD. By using an exponential relational expression with respect to temperature, the temperature change, that is, the intensity of infrared rays can be measured as in the case of the thermistor.

Next, a specific structure of the thermal infrared sensor 40 will be described with reference to FIGS. 9 and 10. A groove 51D is formed in an n-type silicon substrate 51 that forms a base 40B of the thermal infrared sensor 40. The reflective layer 4 made of tungsten is formed on the surface of the groove 51D.
1 is formed, and a silicon nitride film 42 is further formed so as to cover the reflective layer 41 to form the recess 40E.

Above the base 40A, the recess 40 is formed.
A silicon nitride film 43 is formed in a bridge shape so as to straddle E,
A polycrystalline silicon layer 44 is formed on the upper surface of the silicon nitride film 43. On the upper surface of the polycrystalline silicon layer 44, a platinum silicide layer 45 that cooperates with the polycrystalline silicon layer 44 to form an SBD is formed. Further, a guard ring 44G made of an n-type diffusion layer is formed in the polycrystalline silicon layer 44 so as to surround the bonding surface with the platinum silicide layer 45, and p ⁺ is formed in a region outside the guard ring 44G. The shape diffusion layer 44B is formed.

On the surface of the polycrystalline silicon layer 44, acid
The silicon oxide film 48 is formed, and the silicon oxide film 48 is formed.
Through the contact holes 48A and 48B provided in
And the wiring layers 46A and 46B made of titanium are respectively
Guard ring 44G, p above ⁺Electricity to the diffusion layer 44B
Connected. And cover all of these
A silicon nitride film 49 is formed on.

The height h2 of the lower surface 43K of the silicon nitride film 43 from the upper surface 41A of the reflection layer 41 is
It is formed to be n times the wavelength λ of the infrared ray (where n is an odd number). As a result, the infrared light transmitted through the infrared light receiving portion 40A is reflected by the reflective layer 41 and then again absorbed by the infrared light receiving portion 40A. Further, in the figure 51A, 51B is a p ⁺ -type diffusion layer which is previously formed on the silicon substrate 1, the p ⁺ -type diffusion layer 51A,
51B is the wiring layer 46A, via the contact holes 43A and 43B formed in the silicon nitride film 43, respectively.
46B, and on the other hand, it is also electrically connected to the wiring of the readout circuit formed on the silicon substrate 51 (not shown).

Next, a method of manufacturing the thermal infrared sensor 40 having the above structure will be described with reference to FIGS. (1) First, a resist is applied on an n-type silicon substrate 51 on which a read-out circuit (not shown) of the thermal infrared sensor 40 is formed by a well-known semiconductor manufacturing technique, and a region corresponding to the infrared light receiving portion 40A is formed. Only exposed
This is exposed / developed, and the silicon substrate 51 is dry-etched using the resist thus produced to a predetermined depth d1.
Forming a groove 51D. After that, the resist is removed, and a tungsten film 52 is formed on the surface of the silicon substrate 51 by 0.5 μm, for example, by a sputtering method, and then a silicon nitride film 53 is formed by 0.3 μm. At this time, from the predetermined depth d1 to the thickness of the tungsten film 52 (0.
The value obtained by subtracting 5 μm) is the depth d described above (see FIG. 1).
2 (a)).

(2) Then, a process of spin-coating a liquid silica-based compound and baking this is repeated twice (spin-on-glass method) to form a thick SOG film, and a resist is formed thereon. A desired mask is formed by applying and exposing / developing this into a desired shape, and the SOG film 55 filling the groove 51D is formed by dry etching using this. Next, the resist is applied again, and the infrared ray receiving section 40
A desired mask 54 is formed by exposing / developing it so that only the region corresponding to A is covered, and the tungsten film 52 and the silicon nitride exposed on the silicon substrate 51 are formed by dry etching using this. The film 53 is removed (FIG. 12B).

(3) The mask 54 is removed, and thereafter,
The SOG film is formed again by the spin-on-glass method, and the SOG film is patterned to form the sloped portion 5 made of the SOG film at the step between the SOG film 55 and the silicon substrate 51.
6A and 56A are formed. The inclined portion 5 formed at this time
The sacrificial layer 57 is formed by the 6A and 56A and the SOG film 55.
Is configured. In this case, the sacrificial layer 57 is the reflective layer 4 described above.
Height h2 from the upper surface of 1 to the upper surface of the SOG film 55
However, its thickness is determined so as to have a desired height (= n × λ / 4: where n is an odd number and λ is the wavelength of the incident infrared ray) (FIG. 12C).

(4) Next, the silicon nitride film 43 is subjected to CV.
The D method is used to form 0.5 μm, and this is patterned. By this patterning, the silicon nitride film 43
The sacrificial layer 57 once covered by is again exposed. Thereafter, a polycrystalline silicon film mixed with n-type impurities so that the resistivity becomes 1 × 10 ¹⁶ Ωcm is grown to 1.0 μm by, for example, the CVD method, covered with a resist, and exposed / developed. A desired mask is formed, and the polycrystalline silicon film is etched into a desired shape (the shape of the infrared light receiving portion 40A) by dry etching using the mask, thereby forming the polycrystalline silicon layer 44. After removing the resist, by thermal oxidation, on the surface of the polycrystalline silicon layer 44,
A silicon oxide film 48 having a film thickness of 0.1 μm is formed (FIG. 12D).

(5) A desired mask is formed on the upper surface of the polycrystalline silicon layer 44 on which the oxide film 48 is formed, and boron is implanted into a desired region by ion implantation using this mask (5 × 10 ¹⁵ cm ⁻² ), and then a mask is formed again by the well-known photolithography technique, and arsenic is implanted into a desired region by ion implantation (3 × 10 ¹⁵ cm ⁻² ), followed by annealing (900 (° C., 1 hour) to form a guard ring 44G and ap ^{+ -type} diffusion layer 44B made of an n ^{+ -type} diffusion layer (FIG. 13E).

(6) Next, a resist is applied on the entire surface,
This is exposed / developed to form a mask that exposes only a desired region of the silicon oxide film 48 (corresponding to the region where the SBD of the polycrystalline silicon layer 44 is formed), and wet etching is performed in this state to expose it. Silicon oxide film 4
8 is removed. Further, platinum silicide is formed on the upper surface by 0.01 μm by, for example, a spatter method, and then,
The resist is removed (lift-off), and the platinum silicide film 45 is formed only on the desired region (FIG. 13).
(F)).

(7) Next, a resist is applied on the silicon nitride film 43 formed on the upper surface of the silicon substrate 51, and the resist is patterned to form a mask, and the silicon nitride film 42 is etched by using the resist. Then, contact holes 43A and 43B communicating with the p ^{+ type} diffusion layers 51A and 51B of the silicon substrate 51 are provided. Then
A contact covering at least the silicon oxide film 48 is formed, the mask is prepared by exposing / developing the resist, and the guide ring 44G and the p ^{+ -type} diffusion layer 44B are connected to each other by etching the silicon oxide film 48 using the resist. The holes 48A and 48B are formed. After removing the resist used as the mask, 0.3 μm of titanium is formed on the upper surface by, for example, a sputtering method and is patterned into a desired shape by a known photolithography technique to form wiring layers 46A and 46B. Yes (Fig. 13
(G)).

(8) Finally, as the protective film and the infrared absorbing film, a silicon nitride film is formed to a thickness of 0.5 μm by, for example, the CVD method, and this is patterned by a known photolithography technique to form the infrared light receiving portion 40A. The silicon nitride film 49 is formed in the corresponding region. By this patterning, the sacrificial layer 57 once covered with the silicon nitride film is exposed again. Then, in this state, wet etching is performed to remove the sacrificial layer 57,
An air gap S is formed between the silicon nitride film 43 and the reflective layer 41 to obtain the bridge structure shown in FIGS. 9 to 11.

FIG. 14 shows a thermal infrared sensor 40 'according to a modification of the second embodiment. The thermal infrared sensor 40 ′ according to this modification is the thermal infrared sensor 40 described above.
Instead of the reflective layer 41 formed in the recess 40E of the metal wirings 41A, 41
The difference is that B is used as a reflective layer. In this case, the slope of the recess 40E is formed in a tapered shape to improve the step coverage of the metal wirings 41A and 41B. In this case, the metal wiring is formed of a metal having a high melting point, such as tungsten, which can sufficiently withstand the heat treatment in the subsequent semiconductor manufacturing process.

Even when an image sensor is constructed by using the thermal infrared sensor 40 and the thermal infrared sensor 40 'according to the second embodiment, the same circuit as that of the first embodiment is used. In the configuration (FIG. 7), these thermal infrared sensors 40 (or 40 ') may be arranged linearly or in a plane. The detailed description of the circuit configuration and the operation of the image sensor using the thermal infrared sensor 40 (or 40 ') will be omitted.

In the second embodiment as well, the reflective layer 41 is used.
Although the example in which tungsten is formed is shown, the reflection layer 41 may be formed of another metal having a high melting point, such as titanium or an alloy of titanium and tungsten. (Third Embodiment) Next, a third embodiment will be described with reference to FIGS. The third embodiment includes claim 1, claim 7 to claim 11, and claim 1.
Corresponds to 5.

First, the thermal infrared sensor 40 will be outlined with reference to FIGS. 15 and 16. Note that FIG. 16 is a plan view showing a state in which the silicon nitride film 69 and the silicon oxide film 68 formed on the surface of the thermal infrared sensor 60 are removed. The thermal infrared sensor 60 according to the third embodiment
As shown in FIG. 15 and FIG.
A heat insulating part 60S is formed under the heat insulating part 60S.
On the connection surface with the silicon substrate (base) 71, a reflection layer 61 for reflecting the infrared light transmitted through the infrared light receiving portion 60A and absorbing again by the infrared light receiving portion 60A is formed.

In the thermal infrared sensor 60 having such a structure, the heat insulating portion 60S formed between the infrared light receiving portion 60A and the silicon substrate 71 forms a heat insulating structure between the infrared light receiving portion 60A and the silicon substrate 71.

In the third embodiment, the SOG film 62 is used for the heat insulating section 60S. Here, while the thermal conductivity of the silicon substrate 71 is 140 W / (m · K), S
The thermal conductivity of the OG film 62 is 1.4 W / (m · K). In this way, since there is a large difference in thermal conductivity between the silicon substrate 71 and the SOG film 62 that constitutes the heat insulating portion 60S, sufficient heat insulation between the infrared light receiving portion 60A and the silicon substrate 71 is achieved.

Thus, the temperature change of the infrared ray receiving portion 60A with respect to the incident infrared ray having a constant intensity becomes large. Further, due to the function of the reflection layer 61, the infrared rays that have once passed through the infrared light receiving section 60A are reflected by the reflection layer 61 and then absorbed by the infrared light receiving section 60A.
Further, a Schottky barrier diode (SBD) is formed in the infrared light receiving portion 60A, similar to the thermal infrared sensors 10 and 40 of the first and second embodiments, and is adapted to the temperature change of the infrared light receiving portion 60A. Further, the intensity of the incident infrared ray is detected by detecting the reverse saturation current value of the SBD.

Next, the specific structure of the thermal infrared sensor 60 will be described with reference to FIGS. A reflection layer 61 made of tungsten is formed on the upper surface of the n-type silicon substrate 71, and an SOG film 62 is formed on the entire surface so as to cover the reflection layer 61. Thus, the SOG film 62 functions as the heat insulating section 60S as described above.

A polycrystalline silicon film is formed on the upper surface of the SOG film 62.
An insulating layer 64 is formed. In addition, the polycrystalline silicon layer
A platinum silicide layer 65 is formed on the upper surface of 64.
An SBD is formed with the polycrystalline silicon layer 64.
You. In addition, the polycrystalline silicon layer 64 has the above-mentioned platinum
The n-type diffusion layer so as to surround the junction surface with the conduction layer 65.
A guard ring 64G is formed.
In the area outside G, p ⁺Form diffusion layer 64B is formed
You.

On the surface of the polycrystalline silicon layer 64, acid
A silicon oxide film 68 is formed, and the silicon oxide film 68 is formed.
Through contact holes 68A, 68B provided in
The wiring layers 66A and 66B made of titanium
Guard ring 64G, p above ⁺Electricity to the diffusion layer 64B
Connected. And cover all of these
A silicon nitride film 69 is formed on.

The height h3 of the lower surface 64A of the polycrystalline silicon layer 64 from the upper surface 61A of the reflective layer 61 is set.
However, n times the wavelength λ of the infrared ray (where n is an odd number)
It is formed so that it becomes. As a result, the infrared light transmitted through the infrared light receiving portion 60A is reflected by the reflective layer 61 and then again absorbed by the infrared light receiving portion 60A.

Further, in the figure, 71A and 71B are p ^{+ -type} diffusion layers formed in advance on the silicon substrate 71, and the p ^{+ -type} diffusion layers 71A and 71B are contact holes 62A and 62A formed in the SOG film 62. 62B through the wiring layer 66
In addition to being electrically connected to A and 66B, they are also electrically connected to the wiring and the like (not shown) of the read circuit formed on the silicon substrate 71.

Next, a method of manufacturing the thermal infrared sensor 60 having the above structure will be described with reference to FIGS. (1) A read circuit (not shown) of the thermal infrared sensor 60 is formed in advance on the n-type silicon substrate 71 by a well-known semiconductor manufacturing technique, and then tungsten is formed on the surface of the silicon substrate 71. It is 0.
5 μm is formed, this is patterned into a desired shape by etching using a well-known photolithography technique, a reflection layer 61 made of tungsten is formed, and a liquid silica-based compound is spin-coated on the upper surface of the reflection layer 61. Is fired (spin-on-glass method), and the film thickness of S is 2.5 μm.
The OG film 62 is formed. In this case, the thickness (2.5 μm) of the SOG film 62 is the same as that of the SO film from the upper surface of the reflective layer 61.
The height h3 to the upper surface 62K of the G film 62 is determined so as to be a desired height (= n × λ / 4: where n is an odd number and λ is the wavelength of the incident infrared ray) (FIG. 17 (a )).

(2) On the upper surface of the SOG film 62 formed as described above, a polycrystalline silicon film having an n-type impurity introduced to have a resistivity of 1 × 10 ¹⁶ Ωcm is formed by, for example, 1.0 μm by the CVD method. After being formed and covered with a resist, exposed / developed to a desired shape to form a mask, and dry etching using the mask forms a polycrystalline silicon layer 64 having a desired shape (the shape of the infrared ray receiving portion 60A). Form. After removing the resist, the polycrystalline silicon layer 64 is formed by thermal oxidation.
A silicon oxide film 68 having a film thickness of 0.1 μm is formed on the surface of (FIG. 17B).

(3) Polycrystalline silicon with oxide film 68 formed
A desired mask is formed on the upper surface of the con layer 64, and this mask is used.
Boron is implanted by ion implantation
(5 × 10^Fifteencm^-2), And then again the well-known photolithography
Ion using a mask formed by using the
Implant arsenic by implantation (3 x 10^Fifteen
cm ^-2), And then anneal (900 ° C, 1 hour)
And the guard ring 64G and p made of an n-type diffusion layer⁺Form expansion
The diffused layer 64B is formed (FIG. 17C).

(4) A resist is applied to the entire surface, and this is exposed / developed into a desired shape to expose only a desired region of the silicon oxide film 68 (corresponding to a region where the SBD of the polycrystalline silicon layer 64 is formed). The exposed silicon oxide film 68 is removed by performing wet etching in this state. Further, platinum silicide is formed on the upper surface thereof by 0.01 μm by, for example, a sputter method, and then the resist is removed (lift-off) to form a platinum silicide film 65 only on the desired region (FIG. 18D). ).

(5) Again, a resist is applied to the entire surface, and this is exposed / developed into a desired shape to form a mask, and etching is performed using the resist, and the SOG film 62 is etched by p ^{+ of the} silicon substrate 71. Contact holes 62A and 62B communicating with the shape diffusion layers 71A and 71B are formed, and the resist is removed (FIG. 18E).

(6) Next, a resist is applied so as to cover at least the silicon oxide film 68, and this is exposed / developed to form a mask, and the silicon oxide film 68 is used.
Of the contact holes 68A, 68 communicating with the guide ring 64G and the p ^{+ -type} diffusion layer 64B by etching
Form B. After removing the resist, titanium is formed to a thickness of 0.3 μm on the upper surface by, for example, a sputtering method and is patterned into a desired shape by a known photolithography technique to form wiring layers 66A and 66B (FIG. 18). (F)).

(7) Next, a silicon nitride film is formed to a thickness of 0.3 μm as a protective film and an infrared absorbing film by, for example, a CVD method, and this is patterned by a known photolithography technique to correspond to the infrared light receiving portion 60A. A silicon nitride film 69 having a desired shape is formed in a region to be formed,
A thermal infrared sensor 60 having the structure shown in FIG. 15 is obtained. still,
Even when an image sensor is configured using the thermal infrared sensor 60 according to the third embodiment, the above-described first
The thermal infrared sensors 60, 60 ... May be arranged linearly or in a plane with the same circuit configuration (FIG. 7) as that of the above embodiment. A specific description of the image sensor using these thermal infrared sensors 60 will be omitted.

In the third embodiment as well, the reflective layer 61 is used.
Although the example in which tungsten is formed is shown, the reflection layer 61 may be formed of another high melting point metal such as titanium or an alloy of titanium and tungsten.

[0094]

According to the first aspect of the present invention, the Schottky barrier diode composed of the polycrystalline silicon layer and the metal film or the metal silicide film on the polycrystalline silicon layer is used as the temperature sensor section. For,
A high-sensitivity thermal infrared sensor can be appropriately formed at a site where a polycrystalline silicon film can be formed.
The degree of freedom in designing the thermal infrared sensor increases.

According to the invention of claim 2, the polycrystalline silicon film having the Schottky barrier diode formed thereon is
Since it can be a heat insulating structure for the semiconductor substrate,
The sensitivity of the thermal infrared sensor can be further increased. Further, according to the invention of claim 3, since the Schottky barrier diode is formed in a bridge structure that can obtain a high heat insulation structure between the infrared light receiving portion of the thermal infrared sensor and the semiconductor substrate, the sensitivity of the thermal infrared sensor is high. Can be further increased.

Further, according to the invention of claim 4, since the portion constituting the Schottky barrier diode is supported by the insulating film having relatively low thermal conductivity, the thermal conductance of the infrared light receiving portion becomes small. , The sensitivity of the sensor is improved. Further, according to the invention of claim 5, the wiring layer for electrically connecting the Schottky barrier diode and the semiconductor substrate can also be used as a film for supporting the portion constituting the Schottky barrier diode, thereby improving the sensor sensitivity. An improved thermal infrared sensor can be easily achieved.

According to the invention of claim 6, a thermal insulation type infrared sensor having a high heat insulation structure between the semiconductor substrate and the infrared ray receiving portion can be obtained by the groove provided in the semiconductor substrate, and the sensor sensitivity is improved. Can be easily achieved. Further, according to the invention of claim 7, a thermal infrared sensor is provided in which a thermal insulation structure between the infrared light receiving portion of the thermal infrared sensor and the semiconductor substrate can be easily achieved, and the sensor sensitivity is improved.

Further, according to the invention of claim 8, since the infrared rays transmitted through the infrared light receiving portion can be reflected by the reflecting layer and made to enter the infrared light receiving portion again, heat with improved sensor sensitivity can be obtained. Type infrared sensor is provided. or,
According to the invention of claim 9, there is provided a thermal infrared sensor in which a reflective layer previously formed on a semiconductor substrate does not melt in a subsequent manufacturing step of a polycrystalline silicon layer and the sensor sensitivity is improved. Provided.

According to the tenth aspect of the invention, the reflective layer is made of a polycrystalline silicon layer by using any metal of high melting point titanium, tungsten, or an alloy containing titanium or tungsten. A thermal infrared sensor that does not melt during the process and has improved sensor sensitivity is provided. According to the invention of claim 11, the infrared rays transmitted through the infrared receiving section and the infrared rays reflected by the surface of the reflecting layer thereafter do not cancel each other, so that the reflected infrared rays can be efficiently and efficiently received. There is provided a thermal infrared sensor having improved sensor sensitivity.

According to the twelfth aspect of the invention, the Schottky barrier diode can be used as the temperature sensor by simply removing the sacrificial layer previously formed on the semiconductor substrate after forming the infrared light receiving portion of the thermal infrared sensor. It is possible to form a thermal infrared sensor having a bridge structure with high sensor sensitivity used as the section. Further, according to the invention of claim 13, a shot is formed by forming a groove on the semiconductor substrate and removing the sacrificial layer formed so as to fill the groove after forming the infrared light receiving portion of the thermal infrared sensor. It is possible to form a thermal infrared sensor having a bridge structure with high sensor sensitivity using a key barrier diode as a temperature sensor unit.

According to the fourteenth aspect of the present invention, the sacrificial layer can be easily removed, and a thermal infrared sensor with improved sensor sensitivity can be easily manufactured. Claim 1
According to the fifth aspect of the invention, the temperature change of the infrared ray receiving portion with respect to the incident infrared ray becomes large, and the sensitivity of the sensor is improved.
According to the invention of claim 16, an image sensor including a large number of highly sensitive thermal infrared sensors is achieved, and
High integration can be achieved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a thermal infrared sensor 10 according to a first embodiment.

2 is a plan view of the thermal infrared sensor 10. FIG.

3 is a perspective view of the thermal infrared sensor 10. FIG.

FIG. 4 is a cross-sectional view showing the manufacturing process of the thermal infrared sensor 10.

5 is a cross-sectional view showing a manufacturing process of the thermal infrared sensor 10 performed after the manufacturing process shown in FIG.

FIG. 6 is a thermal infrared sensor 1 of a modified example of the first embodiment.
It is a perspective view which shows 0 '.

FIG. 7 is an image sensor 20 using the infrared sensor 10.
3 is a circuit diagram of the data read circuit of FIG.

FIG. 8 is a timing chart for explaining the operation of the image sensor 20.

FIG. 9 is a sectional view showing a thermal infrared sensor 40 according to a second embodiment.

10 is a plan view of a thermal infrared sensor 40. FIG.

FIG. 11 is a perspective view of a thermal infrared sensor 40.

FIG. 12 is a cross-sectional view showing the manufacturing process of the thermal infrared sensor 40.

FIG. 13 is a cross-sectional view showing a manufacturing process of the thermal infrared sensor 40, which is performed subsequent to the manufacturing process shown in FIG.

FIG. 14 is a perspective view showing a thermal infrared sensor 40 ′ of a modified example of the second embodiment.

FIG. 15 is a cross-sectional view showing a thermal infrared sensor 60 according to a third embodiment.

16 is a plan view of a thermal infrared sensor 60. FIG.

FIG. 17 is a cross-sectional view showing the manufacturing process of the thermal infrared sensor 60.

FIG. 18 is a cross-sectional view showing a manufacturing process of the thermal infrared sensor 60, which is performed following the manufacturing process shown in FIG. 16;

FIG. 19 is a cross-sectional view showing a conventional thermal infrared sensor 100.

FIG. 20 is a plan view of a conventional thermal infrared sensor 100.

[Explanation of symbols]

 1, 51, 71 Semiconductor substrate (silicon substrate) 5, 55 Sacrificial layer 10, 40, 60 Thermal infrared sensor 10A, 40A, 60A Infrared light receiving part 10B, 40B, 60B Substrate 10C, 40C, 60C Crosslinking part 10D Reflecting part 11 , 41, 61 Reflective layer 14, 44, 64 Polycrystalline silicon film 20 Image sensor 40E Recessed portion 60S Thermal insulation portion S Void

Claims (16)

[Claims] 1. A Schottky barrier diode is formed by forming a polycrystalline silicon layer above a semiconductor substrate, and forming a metal film or a metal silicide film on the surface of the polycrystalline silicon layer to form a Schottky barrier diode. A thermal infrared sensor characterized by being used as a temperature sensor unit. 2. A void having a predetermined width is provided between the semiconductor substrate and the polycrystalline silicon layer, and the Schottky barrier diode is formed above the void. The thermal infrared sensor described. 3. The polycrystalline silicon layer is supported on the voids by one or more films forming an infrared ray receiving portion to form a bridge structure. Thermal infrared sensor. 4. The thermal infrared sensor according to claim 3, wherein at least one of the one or more films is an insulating film. 5. The method according to claim 3, wherein at least one of the one or more films is a wiring layer.
The thermal infrared sensor described in. 6. The thermal infrared sensor according to claim 2, wherein a concave portion having a predetermined depth is formed on the semiconductor substrate below the infrared light receiving portion. 7. An interlayer film having a predetermined width and having a lower thermal conductivity than that of the semiconductor substrate is provided between the semiconductor substrate and the polycrystalline silicon layer, and the Schottky barrier is provided above the interlayer film. The thermal infrared sensor according to claim 1, wherein a diode is formed. 8. A reflection layer for reflecting infrared rays is formed in a predetermined region of the semiconductor substrate located below the Schottky barrier diode.
9. The thermal infrared sensor according to claim 7. 9. The thermal infrared sensor according to claim 8, wherein the reflective layer is formed of a metal having a melting point higher than a temperature required in the step of forming the polycrystalline silicon layer. 10. The thermal infrared sensor according to claim 8, wherein the reflective layer is made of any one of titanium, tungsten, and an alloy containing titanium and tungsten. 11. The infrared ray receiving section has a height from a lower surface of the infrared ray receiving section directly below the Schottky barrier diode to a surface of the reflective layer, which is n / 4 times the wavelength of the infrared ray (where n is a wavelength of the infrared ray). Is an odd number), and the thermal infrared sensor according to any one of claims 8 to 10. 12. A sacrificial layer is formed on a semiconductor substrate, and a sacrificial layer is formed directly above the sacrificial layer or via one or more films,
A polycrystalline silicon layer is formed, a metal film is formed on the polycrystalline silicon layer to form a Schottky diode, and then the sacrificial layer is removed to form the bridge structure. The method for manufacturing a thermal infrared sensor according to any one of claims 3 to 5 or claim 8 to 11. 13. A concave portion having a predetermined depth is formed on a semiconductor substrate, the concave portion is filled with a sacrifice layer, and the concave portion is directly provided thereabove or through one or more films.
A polycrystalline silicon layer is formed, a metal film is formed on the polycrystalline silicon layer to form a Schottky diode, and then the sacrificial layer is removed to form the bridge structure. The method for manufacturing the thermal infrared sensor according to claim 6, or claim 8. 14. The method for manufacturing a thermal infrared sensor according to claim 12, wherein the sacrifice layer is removed by wet etching. 15. The infrared absorbing film as one of the one or more films forming the infrared receiving section, as claimed in any one of claims 3 to 6 or 8 to 14.
The thermal infrared sensor according to any one of the above. 16. Claims 1 to 11 and claim 1.
5. An image sensor using a thermal infrared sensor, characterized in that a plurality of thermal infrared sensors according to any one of 5 are arranged linearly or in a plane.