JP3229984B2 - Infrared detection method using capacitance, infrared sensor, and infrared imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-cooling type infrared ray detecting method using capacitance, an infrared ray sensor, and an infrared ray imaging apparatus.

[0002]

2. Description of the Related Art An object emits infrared rays having different wavelengths depending on the temperature. For this reason, it is possible to measure the temperature of an object by detecting the wavelength of infrared rays,
A temperature change can be detected by detecting a change in the wavelength of infrared light. If the temperature change is detected, for example, the presence of a moving object can be detected . Here, detecting the wavelength of the infrared ray and detecting the change in the wavelength of the infrared ray are collectively referred to as “infrared ray detection”. An object held at a certain temperature radiates infrared rays having a wavelength distribution. However, here, for the sake of simplicity, description will be made assuming that an object held at a certain temperature radiates infrared light of a single wavelength.

An infrared sensor detects infrared radiation radiated from an object, and is used in a wide range of fields such as temperature measurement, defense, and monitoring. Infrared sensors include:
There are a quantum type (using HgCdTe or the like for the sensor), a Schottky type (using a Schottky junction for the sensor), a bolometer type, and a pyroelectric type. The quantum type and the Schottky type are called cooling type sensors because the infrared sensor is cooled down to about 77K. On the other hand, the bolometer type and the pyroelectric type can detect infrared rays without cooling, and are called uncooled types (however, in order to improve sensitivity, 27
It may be cooled to about 0K).

A bolometer-type sensor uses a bolometer substance for a light receiving portion for detecting infrared rays. The bolometer material is
This is to change the electric resistance value according to the temperature change.
When infrared rays are incident on the light receiving section using the bolometer substance, the bolometer substance changes in temperature. A current is passed through the bolometer material in advance, and this current changes with a change in the temperature of the bolometer material. The bolometer-type sensor detects infrared rays by measuring this current.

[0005] The pyroelectric sensor uses a pyroelectric substance in a light receiving portion for detecting infrared rays. When infrared rays are incident on the light-receiving unit using the pyroelectric substance, the pyroelectric substance causes a temperature change, and releases electric charges (signal charges) corresponding to the temperature change. That is, the pyroelectric substance generates and discharges a signal charge corresponding to a temperature change between a certain time point and the next time point. The pyroelectric sensor detects a change in infrared rays by detecting the emitted signal charges. Generally, in a pyroelectric sensor, a chopper is arranged in front of a light receiving unit. The chopper is
This is a propeller-shaped rotating plate including a portion (light-shielding plate) that blocks infrared light incident on the light-receiving portion and a portion (light-transmitting portion) that transmits infrared light. When the chopper is rotated, the light blocking plates and the light transmitting portions are alternately arranged in front of the light receiving portion. For this reason, infrared rays radiated from the object and infrared rays radiated from the light shielding plate are alternately incident on the light receiving unit. Then, the light receiving section made of the pyroelectric substance emits electric charges corresponding to the temperature difference between the chopper and the object. Further, by setting the temperature of the chopper as the reference temperature, the temperature of the object can be measured.

An uncooled infrared sensor has a lower sensitivity than a cooled type, but can be made smaller, and can be easily maintained. Therefore, it is widely used as a human body detection sensor (for example, for an automatic door) for detecting the movement of an object. Used. In addition, an infrared imaging device in which a plurality of light receiving sections made of a bolometer substance or a pyroelectric substance are arranged one-dimensionally or two-dimensionally has been developed.

[0007]

However, in the above-mentioned prior art, the bolometer-type sensor had to supply a measuring current to the bolometer material. For this reason, self-heating of the resistor occurs, and there is a problem that the measured value is not reliable. The present invention has been made in view of such conventional problems, and provides a new infrared detection method, and an infrared sensor and an infrared imaging device using the same.

[0008]

As a result of intensive studies, the present inventors have proposed and invented a novel infrared detecting method for detecting a change in infrared by measuring capacitance. According to this infrared detection method, a change in infrared light can be detected without causing an error due to self-heating.

The present invention firstly provides an " insulating substrate or semiconductor substrate"
Provide a support on top, support one end on the support and free the other end
At the end and at different temperatures depending on the temperature
A plate-like electrode whose electric capacitance with respect to the counter electrode changes, and the semiconductor substrate via a space facing the plate-like electrode.
Preparing a counter electrode disposed on the top, applying a voltage to the plate-shaped electrode and the counter electrode and measuring a change in the amount of electric charge accumulated in the plate-shaped electrode, the change in infrared radiation radiated from the object And a method for detecting infrared rays by means of capacitance (claim 1).

Further, the present inventor has proposed and invented a method of detecting infrared rays without using a chopper. The present invention provides, secondly, " providing a support portion on a semiconductor substrate,
And the free end and the other end is supported at one end to the support portion, and, electrodeposition of the counter electrode by temperature curved different curvatures by temperature
A plate-like electrode whose air volume changes , facing the plate-like electrode
And a counter electrode arranged on the semiconductor substrate via a space as described above, and a first electrode is provided between the plate electrode and the counter electrode.
A first step of causing a potential difference between the first and second electrodes to accumulate a first charge amount in the plate electrode, and a second step of causing a second potential difference between the plate electrode and the counter electrode to generate a second charge amount a second step of measuring the difference between the first amount of charge and the second charge amount causes accumulated in the plate electrode Tona
A method for detecting infrared rays by means of capacitance, wherein the method detects infrared rays.

Further, the present inventor has developed and invented an infrared sensor using this infrared detection method. The present invention prepares a "insulating substrate or a semiconductor substrate in the third, the
Protrudes from the substrate, and a support portion made of insulating material or conductors, by and temperature varies curvature with temperature
A plate-like electrode whose electric capacitance with the counter electrode changes and one end of which is fixed to the support portion and the other end of which is a free end; and
A counter electrode disposed on the semiconductor substrate via a space so as to face each other , and the plate-shaped electrode or the counter electrode
And a switch connected to either one of
The present invention provides a capacitance type infrared sensor (claim 3).

[0012]

The present inventors have developed and invented an infrared solid-state imaging device using this infrared detection method. The present invention includes a fourth to "the semiconductor projecting insulator from the substrate or support portion made of a conductor, different curvature with temperature 且
One plate-shaped electrode which is a free end and the other end is fixed the electric capacity change end of the counter electrode to the support portion by the temperature, the semiconductor base so as to face through the plate-shaped electrode and space
A counter electrode disposed on the plate , and a contact with one of the electrodes;
An infrared sensor having a switch connected to the semiconductor
That one or two dimensions are arranged on the substrate
Characteristic capacitive infrared imaging device (Claim 9) "is provided.

[0014]

[0015]

First, a method for detecting infrared rays by capacitance will be described. The capacitance is generated between the electrodes when the two electrodes are arranged so as to face each other via an insulator. When different voltages are applied to these electrodes to generate a potential difference between the two electrodes, charges are accumulated in each of the electrodes. The capacitance is determined by the area of the electrode (accurately, the area of the facing part), the distance between the electrodes, and the type of insulator. Electric charges are accumulated up to an amount corresponding to the potential difference between the electrodes and the capacitance.

Here, one of the electrodes is a plate-like (or rod-like) electrode that is curved to have a different curvature depending on the temperature. Examples of such a plate-like electrode include a bimetal made of two metals having different linear expansion coefficients, and a plate-shaped electrode made of an insulator and a metal having different linear expansion coefficients. One end of the plate-like electrode is fixed to the support, and the other end (hereinafter, referred to as a free end) is movable. The space between the plate-shaped electrode and the other electrode (hereinafter, referred to as a counter electrode) is set to air or vacuum. In this way, the curvature of the plate electrode corresponds to the temperature of the plate electrode (referred to as T1), and this temperature is further reduced by the infrared ray (λ) incident on the plate electrode.
1). If the plate-like electrode bends at a certain curvature, a capacitance corresponding to the curvature of the plate-like electrode is generated in the two electrodes. Therefore, if a potential difference is generated between these electrodes, the accumulated charge amount (Q1) is accumulated.

Here, the infrared ray incident on the plate electrode is λ1
From 1 to λ2, the temperature of the plate-like electrode changes from T1 to T2.
Changes to Then, the plate-like electrode is curved at a curvature corresponding to the temperature with the support portion as a fulcrum, and the capacitance between the electrodes changes. As described above, a constant voltage is applied to each electrode, and when the capacitance changes, a charge amount (Q2) corresponding to the capacitance is accumulated in each electrode. Therefore, the difference between the charge amounts Q1 and Q2 moves from (or to) the respective electrodes. Therefore, if the flow of the electric charge is measured as a current value or a voltage value, a temperature change of the plate-like electrode can be detected. Further, a change in the temperature of the plate electrode corresponds to a change in the incident infrared light. Therefore, if the above measurement is performed, a change in infrared light can be detected.

Hereinafter, a more detailed description will be given using equations.
A plate-like substance (or rod-like substance) having a different curvature depending on the temperature, such as a bimetal, is fixed at one end to the support portion 6 as shown in FIG. The thickness of the plate electrode is t (mm).
The plate-like electrode 5 receives infrared light from an object and has a temperature of T1.
(° C.), the capacitance becomes C1 (F). For simplicity, the plate electrode 5 is parallel to the counter electrode 2 in this state, the distance between the plate electrode 5 and the counter electrode is d1 (mm), and the facing length of the plate electrode 5 and the counter electrode 2 is L. (mm).

Here, it is assumed that, for example, infrared rays from a moving object are incident on the plate electrode. The wavelength of the infrared light incident on the plate electrode changes. For this reason, the temperature of the plate electrode 5 changes from T1 (° C.) to T2 (° C.), and the plate-like electrode 5 curves to a curvature corresponding to the temperature. At this time, assuming that the plate-like electrode is bent so as to approach the counter electrode side, the amount of position change D (mm) in the direction in which the free end of the plate-like electrode 5 is curved is expressed by Expression 1. D = (KΔTL ² ) / t (1) K is a curvature (/
° C) and ΔT are the absolute values of (T1-T2).

The plate electrode is curved with a radius R as shown in FIG. However, for the sake of simplicity, it is approximated to approach the counter electrode in a straight line with the fixed end as the support portion [FIG.
(C)]. At this time, if the average distance between the plate-like electrode 5 and the counter electrode is d2 and the capacitance is C2, Equations 2 and 3 are obtained.
Is represented. d2 = d1 - (D / 2 ) ······ type 2 C2 / C1 = (εA / d2) / (εA / d1) = d1 / d2 = d1 / (d1 -KΔTL 2 / 2t) ··· Equation 3 Therefore, if the capacitances C1 and C2 are measured, it is found that a temperature change has occurred in the plate-like electrode, whereby it is possible to detect that the infrared ray incident on the plate-like electrode has changed.
The capacitance can be detected by applying a constant voltage between the plate-shaped electrode and the counter electrode, and measuring a change in the amount of accumulated electric charge accompanying a change in the capacitance by measuring a current or a voltage.

In the above, the case where the plate-like electrode approaches the counter electrode side has been described. However, conversely, the plate-like electrode can be formed so as to be separated from the counter electrode. If the distance between the central portion of the plate electrode 5 and the counter electrode at this time is d3 and the capacitance is C3, Equations 4 and 5 are expressed. d3 = d1 + (D / 2 ) = ····· Formula 4 C3 / C1 (εA / d3 ) / (εA / d1) = d1 / d3 = d1 / (d1 + KΔTL 2 / 2t) ····· Expression 5 Expression 6 is expressed by Expression 3 and Expression 5. (C2 / C1) - (C3 / C1) = d1 KΔTL 2 / t [(d1 -KΔTL 2 / 2t) (d1 + KΔTL 2 / 2t)]> 0 ······ formula 6 Formula 6 is always positive It is. In other words, it can be seen that the change rate of the capacitance is larger when the plate-shaped electrode approaches the counter electrode. For this reason, it is preferable that the plate-like electrode is formed closer to the counter electrode because the sensitivity is higher in infrared detection.

If the change in the infrared ray is detected based on the change in the capacitance, self-heating does not occur unlike the bolometer type sensor. Therefore, a change in temperature can be accurately measured. Further, as can be seen from Equation 1, the amount of change in the position of the free end of the plate-like electrode is a function of the length and thickness of the plate-like electrode, and does not depend on the width of the plate-like electrode. For this reason, when an imaging device in which a plurality of sensors are integrated on the same semiconductor substrate is manufactured, the width of the plate-shaped electrodes can be reduced to achieve high-density integration in the width direction.

When detecting a change in infrared light, a temperature change amount corresponding to the magnitude of the change in infrared light is detected. However, the temperature of the object cannot be detected. Next, an infrared detection method capable of measuring a temperature will be described. A plate-like (or rod-like) electrode having a different curvature depending on the temperature is arranged so as to face the counter electrode via a space. One end of the plate-like electrode is fixed to the support, and the other end is a free end. The space between the plate-shaped electrode and the other electrode (hereinafter, referred to as a counter electrode) is set to air or vacuum. The plate-shaped electrode is brought to a certain temperature (T1) by the infrared ray (λ1) incident thereon. Then, the plate-like electrode curves to a curvature corresponding to the temperature T1. Here, different voltages are respectively applied to the plate-shaped electrode and the counter electrode. Therefore, a first potential difference occurs between the plate electrode and the counter electrode. For example, the counter electrode is ground voltage, the plate electrode is 1 V
Then, the first charge amount (QL1) corresponding to the 1V difference is accumulated in the plate-like electrode. This is the first step.

Next, a second potential difference is applied between the plate electrode and the counter electrode while the temperature of the plate electrode is T1.
For example, if the opposite electrode is at ground voltage and the plate electrode is 5V, a second charge (QT1) corresponding to a potential difference of 5V is stored in the plate electrode. However, QL1 has already been
Are stored. Therefore, a charge amount corresponding to the difference (5V-1V) between the first potential difference and the potential difference here moves to the plate-shaped electrode and is newly accumulated. That is, the second charge amount (QT1) is composed of QL1 and the newly flowing charge amount. This newly flowing charge amount is called a signal charge amount (QS1). The signal charge amount can be measured as a current value or a voltage value. This is the second step. By measuring the amount of signal charge, the temperature of the plate-like electrode is determined,
Further, the wavelength of the incident infrared light is detected.

At another time, if the wavelength of the infrared ray incident on the plate electrode changes from λ1 to λ2, the temperature of the plate electrode changes from T1 to T2. The plate-like electrode is curved with a curvature corresponding to the temperature T2 with the support portion as a fulcrum. In this state, the operation of the first step is repeated. The first charge amount (QL2) is stored in the plate-like electrode. Next, the above-described second step is repeated. The signal charge (QS2) flows into the plate-like electrode and is accumulated. Then, the signal charge amount (QS2) is measured.

In other words, this method of detecting infrared rays is based on the fact that while the plate-like electrode is kept at the same temperature (ie, while the same infrared ray is incident on the plate-like electrode), The signal charge is detected by applying a different potential difference between the electrodes twice. The charge amount of the smaller potential difference between the plate electrode and the counter electrode (first charge amount in the above example) acts as the reset charge amount. The amount of (signal) charge newly flowing in at the other potential difference is an amount uniquely determined by the temperature of the plate-like electrode. That is, this detection method is based on the fact that the amount of electric charge accumulated when the plate-shaped electrode is at a certain temperature (T1) and another temperature (T2)
It does not measure the change in the amount of charge accumulated at the time. The difference between the reset charge amount and the total charge amount at each temperature is measured. For this reason, the infrared light incident on the plate-like electrode can be measured. According to this detection method, not only can the temperature change be accurately measured without self-heating, but also the temperature can be measured without using a chopper. Here, the voltage of the counter electrode is fixed, but the voltage of the plate electrode may be fixed and the voltage of the counter electrode may be changed.

Here, the configuration of a sensor or an imaging device using the infrared detection method of the present invention will be described. The plate-shaped electrode is an electrode in which two or more types of substances having different coefficients of linear expansion are laminated in a layered manner. Such a plate-like electrode bends to a different curvature depending on the temperature. It is preferable that the difference between the linear expansion coefficients is large.
The material used for the plate electrode is bimetal, Al and Al
There is an electrode in which ₂ O ₃ is laminated in layers. The counter electrode is
It is arranged in a planar shape facing the plate-like electrode. Wirings for applying a voltage are connected to these electrodes. The support portion supports the plate-shaped electrode, and the material thereof may be an insulator or a conductor. If you use a conductor for the support,
The supporting portion also functions as a part of a wiring for applying a voltage to the plate-like electrode. If an insulator is used for the support portion, the thermal conductivity of the insulator is small, so the support portion also acts as a heat shield. This corresponds to the infrared sensor described in claim 3.

In the infrared sensor according to the fourth aspect, a switch is further arranged. As described above, when the temperature of an object is measured (that is, when infrared rays are detected), different voltages are applied to the plate-shaped electrode twice. That is, the voltage must be switched. The switch is arranged to switch the voltage in this way. After the first voltage is applied to the plate-like electrode, the switch is turned off, the infrared sensor having the switch is turned off, the switch is switched to the second voltage, and the switch is turned on again. The electrode to which different voltages are applied twice may be a counter electrode instead of a plate electrode. In this case, the switch is connected to the counter electrode.

Also, when measuring a change in temperature (ie, when detecting a change in infrared rays), the switch has the effect of improving the sensitivity. The plate-like electrode bends to another curvature as the temperature changes. However, it does not bend instantaneously. A time lag occurs. Therefore, the movement of the accumulated charge is not performed instantaneously, but is performed in a certain time. The amount of charge movement is detected by measuring current or voltage. At this time, the measurement sensitivity increases as the value of [the amount of moving charge / the time from the start to the end of the transfer of the charge] increases. The higher the measurement sensitivity, the higher the detection sensitivity of the infrared change. Here, the molecule of the above formula (the amount of moving charge)
Are the same, the sensitivity increases as the denominator (the time from the start to the end of the charge transfer) decreases. The switches are arranged to reduce the time for the charge to move. Less than,
This will be described.

A switch is connected to the plate-like electrode. Wiring is connected to the other end of the switch. At a certain time t1, the switch is turned on, and a constant voltage is applied to the plate-like electrode via a wiring. An infrared ray λ1 is incident on the plate-like electrode, and the plate-like electrode is curved to a certain curvature. For this reason,
A capacitance C1 is generated between the plate electrode and the counter electrode, and a corresponding charge Q1 is accumulated in the plate electrode (and the counter electrode). Next, at time t2, the switch is turned off. In this state, the incident infrared light changes to λ2.
The plate-like electrode changes in temperature and bends to different curvatures. The capacitance of the plate electrode and the counter electrode changes from C1 to C2. However, the switch is turned off, and the amount of charge stored in the plate-like electrode remains at Q1. Next, at time t3
In, the switch is turned on again, and a constant voltage is applied to the plate-like electrode. A charge Q2 corresponding to the capacitance C2 is accumulated in the plate-like electrode. At this time, the charge amount of Q2-Q1 moves instantaneously, and a current corresponding thereto is generated. This current is measured and changes in infrared light are detected (or
This current may be converted to a voltage and the voltage measured.

In the infrared sensor in which no switch is provided, a change in infrared light is detected by the movement of the electric charge of Q2-Q1 which occurs between time t2 and time t3. However, by arranging the switch, substantial charge transfer is instantaneously performed. For this reason, the value of [the amount of moving charges / moving time] becomes extremely large, and the current or voltage measurement sensitivity is increased. Accordingly, the detection sensitivity of infrared rays can be increased. Since the switch operates at high speed and can be miniaturized, a semiconductor element such as a MOS transistor is preferable. For this purpose, the infrared sensor and the switch are preferably formed on the same semiconductor substrate. Further, if the switch is arranged below the counter electrode as in the sensor according to the fifth aspect, the infrared sensor can be miniaturized.

According to the infrared sensor of the present invention, if an infrared absorbing layer is arranged on the plate-like electrode,
It is possible to further increase the detection sensitivity of infrared rays. The infrared absorbing layer includes gold and black. Part of the infrared light incident on the plate electrode is reflected. The reflected infrared rays have no effect of contributing to the temperature change of the plate-like electrode. The infrared absorbing layer prevents infrared rays from being reflected from the plate electrode. For this reason, the temperature of the plate electrode is more effectively changed.

Further, if a plurality of infrared sensors are arranged and signal charges are sequentially taken out, an infrared image and a temperature distribution can be obtained. For this reason, on the same semiconductor substrate as the infrared sensor,
A switch transistor for generating first and second potential differences between the plate-shaped electrode and the counter electrode, and a wiring portion for transferring charges to the plate-shaped electrode and reading out signal charges are arranged. This is the infrared solid-state imaging device according to the ninth aspect.

Further, if a transfer gate is arranged in the switch transistor and a transfer section such as a CCD is arranged in the wiring section, a solid-state imaging device using the CCD as a read section is obtained. This is the infrared solid-state imaging device according to the tenth aspect.

[0035]

The present invention will be described more specifically below with reference to examples. However, the present invention is not limited to these examples. (First Embodiment) FIG. 1 is a sectional view of a capacitance type infrared sensor according to a first embodiment. The infrared sensor according to the present embodiment includes a plate electrode 5 on a glass substrate (insulating substrate) 1,
It comprises an opposing electrode 2 arranged to face it via a space, a support 6 for fixing the plate electrode 5, and wirings 8, 9 connected to the plate electrode 5 and the opposing electrode 2, respectively. The substrate 1 is not limited to glass but may be an insulator. The plate-like electrode 5 includes a metal electrode 3 having a composition of Ni (36%) Fe (64%) and a metal electrode 3 of Ni (20%) Mn (6%) Fe (74%)
Are laminated. The metal electrode 3 has a small coefficient of linear expansion, and the metal electrode 4 has a large coefficient of linear expansion.
This combination of constituent metals is a common bimetal.

The plate electrode 5 is electrically connected to the extraction electrode 7 via the support 6. In the present embodiment, the metal electrode 3, the support portion 6, and the extraction electrode 7 are formed simultaneously from the same metal. However, different conductive materials may be used and may be formed separately. The extraction electrode 7 is connected to the aluminum wiring 8. On the other hand, the counter electrode 2 is made of aluminum and is connected to the wiring 9.

The area where the plate electrode 5 and the counter electrode 2 face each other is 500 μm ² (length 50 μm, width 10 μm), and the distance between the plate electrode 5 and the counter electrode 2 is 4500 °. When a potential difference of 5 V was applied between these electrodes and the temperature of the plate electrode 5 was changed by 0.01 ° C., the number of electrons (charge amount) accumulated in the plate electrode 5 changed by 2500. Thereby, a change in infrared light was detected.

Next, a method of manufacturing the infrared sensor according to this embodiment will be described. FIG. 2 is a cross-sectional view illustrating each step of the infrared sensor for explaining this. First, an aluminum thin film is grown on the glass substrate 1 by a sputtering method, and is patterned by a known photolithographic etching method. Thereby, the counter electrode 2 is formed. Next, a polyimide resin is applied and heat treatment is performed at 400 ° C. for 1 hour. Further, this is patterned to form the counter electrode 2
Is formed so as to cover. FIG. 2A shows this state. The film thickness of the portion 11 in the polyimide film 10 is 4500 °. The film formed here does not have to be a polyimide film. However, the aluminum thin film melts at a temperature of 500 ° C. or higher. The film formed here can be formed at 500 ° C. or lower and can be removed later, and is, for example, SOG (spin-on-glass).

Next, the composition was Ni (36%) Fe (64
%) Of a metal film is grown by sputtering, and then patterned to form a metal electrode 3, a support 6, and an extraction electrode 7 at the same time. FIG. 2B shows this state. Next, the composition is Ni (20%) Mn (6
%) A metal film of Fe (74%) is grown by a sputtering method and then patterned to form a metal electrode 4 on the metal electrode 3. Thus, a plate-like electrode 5 formed by laminating the metal electrode 3 and the metal electrode 4 is formed. Next, an aluminum thin film is grown and patterned to form wirings 8 and 9. FIG. 2 shows this state.
(C). Finally, the polyimide film 10 is removed, and the infrared sensor of this embodiment is completed. (Second Embodiment) FIG. 3 is a sectional view of a capacitance type infrared sensor according to a second embodiment. The infrared sensor according to the present embodiment includes a plate electrode 5 a on a glass substrate (insulating substrate) 1.
And the counter electrode 2 disposed so as to face through a space, and a support portion 6a for fixing the plate electrode 5.
The substrate 1 is not limited to glass but may be an insulator.

The plate electrode is an aluminum electrode (Al) 3
a and aluminum oxide (Al_TwoO _Three) 4a was laminated
Things. Aluminum oxide oxidizes aluminum
Can be easily formed, and
If possible, even if stress due to bending occurs, these two films
Is difficult to peel off. Wiring 8 made of aluminum
Is formed simultaneously with the aluminum electrode 3a. Armini
The voltage is applied to the electrode 3a by the wiring 8, and the signal
Signal charge is accumulated. On the other hand, the wiring 9 to the counter electrode 2
It is formed simultaneously with the counter electrode 2.

The support 6a is formed of a silicon nitride film (insulator). In this case, since the silicon nitride film has low thermal conductivity, detection sensitivity to infrared rays is improved. Further, the plate-like electrode 5a is firmly fixed to the support. Therefore, it becomes strong against stress due to bending. (Third Embodiment) FIG. 4 is a sectional view of a capacitance type infrared sensor according to a third embodiment. In the infrared sensor according to the present embodiment, a plate-like electrode 25 disposed on a silicon substrate (semiconductor substrate) 21, a counter electrode 22 disposed so as to face through a space to the plate-like electrode 25, and the plate-like electrode 25 are fixed. And a MOS transistor (switch) 30.

A desired portion of the surface of the silicon substrate 21 is covered with a thermal oxide film (silicon oxide film) 37. The plate electrode 25 is a general bimetal composed of the metal electrodes 23 and 24 having the same composition as in the first embodiment. A silicon nitride film (insulator) is disposed on the support 26. If you do this,
Since the silicon nitride film has low thermal conductivity, the detection sensitivity to infrared rays is improved. Further, the plate-like electrode 5a is firmly fixed to the support. Therefore, it becomes strong against stress due to bending.

The MOS switch 30 includes a source region 32,
It comprises a drain region 31 and a gate electrode 33. The drain region 31 is connected to the metal electrode 23 via the extraction electrode 27. A wiring 28 made of polysilicon is connected to the source region 32. The counter electrode 22 and the gate electrode 33 are formed of tungsten silicide (WSi). In addition, wirings 29 and 34 made of polysilicon are connected to the counter electrode 22 and the gate electrode 33. The periphery of the counter electrode 22 is covered with the silicon nitride film 35.
In this way, even if the opposing electrode 22 comes into contact with the plate electrode 25, no short circuit occurs. In addition, a protective film 36 made of PSG (phosphorus-containing silicon glass) is disposed on the wiring 28 and the MOS transistor 30.

Here, a method of manufacturing the infrared sensor according to this embodiment will be described. FIG. 5 is a cross-sectional view of each step of the infrared sensor for explaining this. First, a 500 ° thermal oxide film (silicon oxide film) 37 is formed on a P-type silicon substrate (semiconductor substrate) 21. Next, a resist is patterned so as to open the planned source region and the planned drain region of the MOS transistor. Using this as a mask, phosphorus is ion-implanted into the opening to form a source region 32.
And a drain region 31 are formed. Next, a WSi thin film is grown to a thickness of 0.2 μm on the silicon substrate 21 by a sputtering method.
Then, a gate electrode 33 is formed. FIG. 5A shows this state.

Next, a silicon nitride film (SiN) is grown to a thickness of 0.7 μm by LP-CVD. Then
A resist having an opening in a region other than the planned supporting portion is patterned, and the SiN is dry-etched using the resist as a mask to a thickness of 500 °. In this way, the support portion 26 made of SiN is formed, and the periphery of the counter electrode 22 is covered with SiN. The height of the support from the counter electrode is 4500 °. After removing the resist pattern, a new resist pattern having an opening in a part of the drain region 31 is formed, and using this as a mask, the SiN and the thermal oxide film (silicon oxide film) 37 are etched. As a result, a contact hole 38 is formed in the drain region 31.

Next, SOG (spin-on-glass) is applied and heat-treated at 1000 ° C. to form an SOG film 39. In this embodiment, the thickness of the SOG film is 1.
It was 5 μm or more. However, it may be 1 μm or more.
Next, the entire surface is etched until the surface of the support portion 26 comes out. FIG. 5B shows this state. S
If the OG film 29 has a thickness of 0.3 μm or more, cracks (fine cracks) occur. But here,
Cracks may occur.

Next, a resist pattern having an opening from the support portion 26 to the drain region 31 is formed, and the SOG film 39 is etched using the resist pattern as a mask. As a result, the SOG film from the contact hole in the drain region 31 to the support portion 26 is removed. Next, when the composition is Ni
A (36%) Fe (64%) metal film is grown by sputtering. Next, this metal film is patterned to form a metal electrode 23 and a lead electrode 27.
Metal electrode 23 is connected to drain region 31. Next, the composition is Ni (20%) Mn (6%) Fe (74%)
Is grown by a sputtering method. Next, the metal film is patterned to form a metal electrode 24. Thereby, the plate-shaped electrode 25 which is a bimetal is formed. In this example, the thickness of each of the metal electrodes 23 and 24 was 500 °. FIG. 5C shows this state.

Next, the SOG film 29 remaining between the plate-like electrode 25 and the counter electrode 22 is etched away. Further, a resist pattern having openings as a part of the source region 32 and a part 2 of the counter electrode 22 is formed, and the SiN and the thermal oxide film are etched using the resist pattern as a mask. As a result, contact holes are formed in the source region 32 and the counter electrode 22. Next, as shown in FIG. 5D, polysilicon is grown and is patterned to form wirings 28, 29, and 34. Finally, the SOG film 39 existing between the plate electrode 25 and the counter electrode 22 is removed, and the infrared sensor of the present embodiment is completed.

The infrared sensor according to the present embodiment is capable of detecting a change in infrared light and detecting infrared light. First, an operation for detecting a change in infrared light will be described. A ground potential is applied to the counter electrode 22 via a wiring 29. The source 32 of the MOS transistor 30 includes:
A voltage of 5 V is applied via the wiring 28. In this state, first, a negative voltage is applied to the gate electrode 33 of the MOS transistor 30, and the MOS transistor 30 is turned on. Thereby, the plate electrode 25 and the counter electrode 22
, A potential difference of 5 V is generated, and charges corresponding to the capacitance are accumulated. Next, MOS transistor 30 is turned off. In this state, when the wavelength of the incident infrared ray changes and the plate electrode 25 changes in temperature, the plate electrode 25
Is curved, and the capacitance changes. However, the MOS transistor 30 is turned off, and the amount of stored charge does not change. Here, the MOS transistor 30
Is turned on. Then, at that moment, the charge corresponding to the amount of change in the capacitance moves to the plate-like electrode 25. The amount of charge transfer can be measured as a current value or a voltage value. If this is measured, a change in infrared light can be detected. Further, by providing a switch as in this embodiment, a current flows instantaneously as compared with a case without a switch, and the detection sensitivity is increased.

Next, an operation for detecting infrared rays will be described. The ground potential is always applied to the counter electrode 22 via the wiring 29. When infrared rays are incident on the plate electrode 25, the plate electrode 25 bends to a curvature corresponding to the temperature. The capacitance at this time is defined as CA1. In this state, first, MO
S transistor 30 is turned on. Plate electrode 25
A first potential difference is generated between the first electrode and the counter electrode 22. Here, -5 V was applied to the plate electrode 25. As a result, the reset charge amount QR1 corresponding to the capacitance CA1 increases
5 is stored. This is the first step.

Next, the MOS switch 30 is turned off. However, the amount of charge stored in the plate electrode 25 is equal to QR1
Is held. Here, another voltage is applied to the wiring 28. Here, -15 V was applied. Next, MO
S transistor 30 is turned on. Plate electrode 25
A second potential difference is generated between and the counter electrode 22. As a result, the charge amount QT1 is stored in the plate electrode 25. The accumulated charge amount QT1 is QT1 = CA1 × (15-5). Therefore, the amount of charge represented by QS1 = QT1-QR1 moves from the wiring 28 to the plate electrode 25 via the MOS switch. Therefore, a current corresponding to the charge amount QS1
Occurs. This current is measured. This is the second step. This current corresponds to the infrared light incident on the plate electrode.

When a plurality of infrared sensors according to the present embodiment are arranged and wiring for reading out signal charges from each sensor is arranged, an infrared imaging apparatus is obtained. (Fourth Embodiment) FIG. 6 is a sectional view of a capacitance type infrared sensor according to a fourth embodiment. In this embodiment, the MO
S transistor 30 (source region 32, drain region 3
1, the gate electrode 33) is disposed below the counter electrode 22, and the plate electrode 25 and the drain region 31 are connected by the extraction electrode 27. Therefore, the portion that receives infrared rays (that is, the light receiving portion), the switch, and the wiring portion can be stacked, and the infrared sensor can be downsized. The wiring to each electrode is not shown in FIG. However, each electrode or diffusion region extends in the vertical direction of the drawing, and wiring is connected to this.
Further, if a plurality of infrared sensors according to the present embodiment are arranged, an infrared imaging device is obtained. (Embodiment 5) FIG. 7 shows a capacitance type infrared imaging apparatus according to a fifth embodiment. (A) is a conceptual plan view,
FIG. 2B is a cross-sectional view taken along the line AA ′ of FIG.
The capacitance type infrared sensor 40 is two-dimensionally arranged on a P-type silicon substrate (semiconductor substrate) 21. The infrared sensor 40 includes a support 26 made of a silicon nitride film (insulator) and a plate-like electrode 25 having one end fixed to the support 26.
And the opposing electrode 22 facing the plate electrode 25 via a space. The plate-like electrode 25 has two linear expansion coefficients different from each other.
It is a bimetal composed of various types of metal electrodes 23 and 24.
The plurality of opposing electrodes 22 arranged in the infrared imaging device are all connected and a ground potential is applied. The support 26 is made of a silicon nitride film (insulator). In this case, since the silicon nitride film has low thermal conductivity, detection sensitivity to infrared rays is improved. Further, the plate-like electrode 5a is firmly fixed to the support. Therefore, it becomes strong against stress due to bending.

Under the counter electrode 22, the silicon oxide film 3
7, a transfer gate 44 and a vertical CCD 4
5 are arranged. The transfer gate 44 includes a transfer gate electrode 47 and a diffusion region 46 of an opposite conductivity type (N type) to the substrate. The diffusion region 46 is provided for the extraction electrode 2.
7 and connected to the electrode 23. The vertical CCD 45
A buried channel 48 of the opposite conductivity type (N type) to the substrate;
It comprises a transfer electrode 49.

One end of the vertical CCD 45 is connected to the horizontal CCD 41.
Connected to. The vertical CCD 45 and the horizontal CCD 41 are
It is a transfer unit that transfers a signal from the infrared sensor 40 and also supplies an electric charge to the infrared sensor 40. 42 is an output amplifier, and 43 is an electrode for wire bonding. When the infrared sensor and the charge transfer portion have a stacked structure as described above, the size can be reduced, or more infrared sensors can be integrated.

Next, the operation of the infrared imaging apparatus according to this embodiment will be described. A ground potential is always applied to the counter electrode 22 via a wiring. When infrared rays enter the infrared sensor 40, the temperature of the plate electrode 25 becomes T1 corresponding to the wavelength λ1 of the infrared rays. The plate-like electrode curves to a curvature corresponding to the temperature. The capacitance at this time is defined as CA1. In this state, first, the reset voltage VH1 is applied to the transfer gate electrode 47. Here, +5 V was applied.
As a result, the transfer gate 44 is turned on, and the initial charge amount QR1 corresponding to the capacitance CA1 is accumulated in the plate electrode 25 (and the counter electrode 22). Plate electrode 25
The electric charge stored in the storage area is an electron, and its amount is QR1 = CA1
× (VH1 -VT). VT is the threshold voltage of the transfer gate. In addition, in the buried channel 48, charges remaining without being supplied to the plate electrode 25 are accumulated.

Next, 0 is applied to the transfer gate electrode 47.
A voltage of V is applied, and the transfer gate 44 is turned off. In this state, the vertical CCD and the horizontal CCD are driven, and the charge remaining in the buried channel 48 is transferred and discarded outside. Next, the read voltage VH2 is applied to the transfer gate electrode 47. VH2 is VH1
Greater voltage. Here, +15 V was applied. As a result, the transfer gate 44 is turned on, and the charge amount QT1 is reduced to the plate electrode 25 (and the counter electrode 2).
It is accumulated in 2). The amount of charge stored is: QT1 = CA1
× (VH2-VT). For this reason, the amount of electrons represented by QT1 = QS1-QR1 moves from the buried channel 48 to the plate electrode 25. This corresponds to the movement of the amount of hole represented by QS1 from the plate-like electrode 25 to the buried channel 48, and the difference between the initial charge amount and the accumulated charge amount is accumulated in the buried channel 48.

Next, 0 is applied to the transfer gate electrode 47.
A voltage of V is applied, and the transfer gate 44 is turned off. In this state, the vertical CCD and the horizontal CCD are driven, and the charges (holes) accumulated in the buried channel 48 are transferred. In this way, it is possible to convert the infrared light incident on each infrared sensor into an amount of electric charge, detect the electric charge, and form an image.

After the transfer is completed, a reset voltage is applied to the transfer gate electrode 47 again, and the above operation is repeated. In any of the embodiments, if an infrared absorbing film such as gold black is disposed on the surface of the plate-like electrode, the sensitivity to infrared rays is improved.

[0059]

As described above, the infrared detecting method of the present invention is based on the capacitance and does not generate self-heating. Therefore, the temperature can be accurately detected. Further, if the difference between the reset charge amount and the total charge amount stored in the plate-like electrode is measured, the temperature can be measured without using a chopper. Therefore, the use of the infrared sensor according to the present invention makes it possible to reduce the size of the entire system.

Further, if an infrared absorbing film is disposed on the surface of the plate-like electrode, the sensitivity of detecting infrared rays is improved. If a plurality of infrared sensors according to the present invention are arranged, an infrared imaging device is obtained. Furthermore, an infrared imaging device in which an infrared sensor and a charge transfer unit are stacked can reduce the chip size, and thus has an effect of improving the yield. If the chip size is the same, more infrared sensors can be integrated.

[Brief description of the drawings]

FIG. 1 is a sectional view of a capacitance type infrared sensor according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the infrared sensor according to the first embodiment in each manufacturing process.

FIG. 3 is a sectional view of a capacitance type infrared sensor according to a second embodiment of the present invention.

FIG. 4 is a sectional view of a capacitance type infrared sensor according to a third embodiment of the present invention.

FIG. 5 is a cross-sectional view of the infrared sensor according to the third embodiment in each manufacturing process.

FIG. 6 is a sectional view of a capacitance type infrared sensor according to a fourth embodiment of the present invention.

FIG. 7 shows a capacitance type infrared imaging device according to a fifth embodiment of the present invention.

FIG. 8 is a conceptual sectional view of a capacitance type infrared sensor for explaining the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate (insulating substrate) 2, 22 Counter electrode 3, 4, 23, 24 Metal electrode 3a Aluminum electrode 4a Aluminum oxide 5, 5a, 25 Plate electrode 6, 6a, 26 Supporting part 7, 27 Leading electrode 8, 9 Aluminum wiring 10 Polyimide film 21 Silicon substrate (semiconductor substrate) 28, 29, 34 Polysilicon wiring 30 MOS switch 31 Drain 32 Source 33 Gate electrode 35 Silicon nitride film 36 Protective film 37 Silicon oxide film 38 Contact hole 39 SOG film 40 Infrared sensor 41 horizontal CCD 42 output amplifier 43 wire bonding electrode 44 transfer gate 45 vertical CCD 46 diffusion area 47 transfer gate electrode 48 buried channel 49 transfer electrode

Continuation of the front page (51) Int.Cl. ⁷ identification code FI H01L 27/14 H01L 31/00 Z 31/00 (58) Field surveyed (Int.Cl. ⁷ , DB name) G01J 1/00-1 / 60 G01J 5/00-5/62 H01L 27/00 JICST file (JOIS) WPI / L (QUESTEL)

Claims (10)

(57) [Claims] A support is provided on an insulating substrate or a semiconductor substrate.
And one end is supported by the support portion and the other end is a free end.
The opposite electrode depending on the temperature
A plate-like electrode whose electric capacity changes , and a pair with the plate-like electrode .
Preparing a counter electrode disposed on the semiconductor substrate through a space so as to face each other, and applying a voltage to the plate electrode and the counter electrode to measure a change in a charge amount accumulated in the plate electrode; Detecting a change in infrared radiation radiated from an object by performing the detection. 2. A method according to claim 1, further comprising: providing a support on the semiconductor substrate;
At one end and the other end as a free end, and bends at different curvatures depending on the temperature.
A plate electrode that changes, and a counter electrode disposed on the semiconductor substrate through a space so as to face the plate electrode are prepared, and between the plate electrode and the counter electrode. A first step of causing a first potential difference to accumulate a first charge amount in the plate electrode; and a second step of generating a second potential difference between the plate electrode and the counter electrode. A second step of storing a charge amount on the plate-like electrode and measuring a difference between the first charge amount and the second charge amount, and detecting a change in infrared light. Infrared detection method. 3. An insulating substrate or a semiconductor substrate is prepared, and a supporting portion, which is provided so as to protrude from the substrate and is made of an insulating material or a conductor, has a different curvature depending on temperature and an electric contact between the counter electrode depending on temperature.
The air volume changes and one end is fixed to the support part and the other end is free
A plate-shaped electrode that is an end, and the semiconductor via a space so as to face the plate-shaped electrode.
A counter electrode disposed on the substrate , and connected to either the plate-like electrode or the counter electrode
Capacitance type red, characterized by comprising a switch
Outside line sensor. 4. The plate-like electrode has two linear expansion coefficients different from each other.
Types of materials are laminated, and at least
The one of the substances is made of a metal.
4. The capacitive infrared sensor according to 3. Wherein said switch is claimed in claim 3 or claim 4 noise, characterized in that disposed below the counter electrode
An electrostatic capacitance type infrared sensor according to any one of the claims. 6. The capacitance type infrared sensor according to claim 3, wherein the plate-like electrode is made of a bimetal. 7. The capacitive infrared sensor according to claim 3, wherein the plate-like electrode is a laminated film made of layered Al and layered Al2O3. 8. The capacitance type infrared sensor according to claim 3, wherein an infrared absorbing film is disposed on a surface of the plate-like electrode. 9. A semiconductor substrate is prepared, and a support portion protruding from above the semiconductor substrate and made of an insulator or a conductor is electrically connected to a counter electrode having a different curvature depending on temperature and different temperature.
The air volume changes and one end is fixed to the support part and the other end is free
A plate electrode which is the end, the semiconductor so as to face through the plate-shaped electrode and space
Infrared light having a counter electrode disposed on a substrate , and a switch connected to one of the electrodes
A sensor is one-dimensionally or two-dimensionally duplicated on the semiconductor substrate.
Capacitance type infrared imaging device characterized by being arranged in a number
Place. 10. The capacitance type infrared imaging according to claim 9.
A vertical CCD connected to the switch in the imaging device;
And a horizontal CCD connected to the vertical CCD.
And, wherein the infrared sensor by the switch is turned on
Charge accumulated in the vertical CCD and the horizontal CCD.
Capacitive infrared imaging device characterized by transmitting
Place.