JP2002286552A - Infrared sensor device, and driving method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared sensor device of a low noise, high sensitivity and a wide dynamic range. SOLUTION: It is canceled by controlling a source voltage in an MOS amplifying transistor 10 in a column amplifying circuit 9 that an elevation of a temperature, of a thermoelectric transducing picture element 1, caused by Joule heat generated by a bias current for reading out temperature information inside the picture element is contained in an output signal as a self-heating voltage component. An output of a lamp waveform voltage generation circuit synchronized with an image selection pulse is impressed as the source voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared sensor device and a driving method thereof, and more particularly to a signal reading circuit of a thermal type infrared sensor and a driving method thereof. An object of the present invention is to provide a low-noise, high-sensitivity, wide dynamic range thermal infrared sensor and a driving method thereof.

[0002]

2. Description of the Related Art Infrared imaging is characterized by being capable of imaging both day and night, being more transparent to smoke and fog than visible light, and being capable of obtaining temperature information of a subject. It has a wide range of applications as a surveillance camera and fire detection camera in the defense field.

In recent years, development of uncooled thermal infrared solid-state imaging devices which do not require a cooling mechanism for low-temperature operation, which is the biggest drawback of the conventional quantum infrared solid-state imaging device which is the mainstream device, has become active. Is coming. In a thermal infrared solid-state imaging device, incident infrared light having a wavelength of about 10 μm is converted into heat by an absorption structure, and then a temperature change of a heat-sensitive portion caused by the weak heat is converted into an electric signal by some thermoelectric conversion means. By reading out the electric signal, infrared image information is obtained.

As a thermal-type infrared solid-state imaging device, a device in which a silicon pn junction for converting a temperature change into a voltage change by a constant forward current is formed in an SOI region has been reported (Tomohiro Ishikawa, et al., Proc. SPIE Vol.3
698, p.556, 1999).

A silicon pn junction type element using an SOI substrate has a feature that it can be manufactured only by a silicon LSI manufacturing process, and is therefore an element excellent in mass productivity.

Further, in the silicon pn junction type element, the internal structure of the pixel can be simplified since the pn junction as the thermoelectric conversion means has a pixel selection function utilizing the rectification characteristics of the pn junction. There are also features.

The temperature change of the pixel portion in the thermal type infrared solid-state imaging device depends on the absorptance of the infrared absorption layer and the optical system.
^The pixel temperature changes by 5 [mK] when the object temperature changes by 1 [K].

When eight silicon pn junctions are connected in series to one pixel element, the thermoelectric conversion efficiency is 10 [m
V / K], a signal voltage of 50 [μV] is generated in the pixel portion when the subject temperature changes by 1 [K].

In practice, a change in temperature of the subject is 0.1
Since it is often required to identify about [K], it is necessary to read out a signal voltage of about 5 [μV] generated in that case.

As described above, as a method of reading a very weak signal voltage, there is a circuit configuration in which a generated signal voltage is current-amplified as a gate voltage of a MOS amplifying transistor, and the amplified signal current is time-integrated with a storage capacitor. Are known.

This circuit configuration is a circuit called a gate modulation integration circuit. This circuit configuration is arranged as a column amplifier circuit for each column of a matrix, and a current amplification for one row is processed in parallel to obtain a signal. This has the effect of limiting the band and reducing random noise.

Voltage gain in the gate modulation integration circuit:
G is the transconductance of the amplification transistor: gm =
δId / δVg, integration time: ti, and storage capacity: C
It is determined by i and is expressed by G = (ti × gm) / Ci. When the integration time: ti and the storage capacitance: Ci are given, the above-mentioned gain is governed by the mutual conductance: gm of the amplifying transistor. When the n-type MOS transistor operates in the saturation region, gm is expressed by the following equation (1). Is approximated by gm = (W / L) · (εox / Tox) · μn · (Vgs−Vth) (1) where W: channel width, L: channel length, εox: dielectric constant of gate oxide film, Tox: gate oxide Film thickness, μn:
Electron mobility, Vgs: gate-source voltage, Vth:
The threshold voltage of the transistor.

As described above, since it is required to recognize about 0.1 [K] as the temperature difference of the subject,
At that time, it is necessary to read out a signal of about 5 [μV] generated in the pixel portion. However, this signal voltage level is extremely low as compared with a CMOS sensor which is a sensor that generally captures visible light. Voltage. For example, Nakamura and Matsunaga, "High Sensitivity CMOS Image Sensor", Journal of the Institute of Image Information and Television Engineers, Vol. 54, no. 2, p. 216, 20
According to 00, the noise voltage is about 0.4 [mV] = 400
In comparison with this, the noise level of the infrared sensor is as low as about 1/80 of that of the CMOS sensor, and the signal voltage to be handled is also as low as about 1/80.

Therefore, considering that the sensor output is processed by a circuit similar to a CMOS sensor, which is a general image pickup device, a column amplification circuit having a gate modulation and integration circuit having a gain of about 80 times is required.

[0015]

By the way, in the thermal infrared sensor, it is often necessary to supply a current to the thermoelectric converter in order to read out temperature information of the thermoelectric converter as an electric signal. There is a so-called self-heating problem in which the bias current or the bias voltage for reading the temperature information generates Joule heat in the thermoelectric conversion unit, and the thermoelectric conversion unit is heated by the Joule heat.

For example, when a thermoelectric conversion pixel is incorporated in a semiconductor substrate, the thermal conductance between the thermoelectric conversion pixel and the semiconductor substrate is
The effect of self-heating in the pn junction type thermoelectric conversion unit, which is a general value of 10 ⁻⁷ [W / K], is based on the assumption that the number of pn junctions is 8,
The bias current is 200 [μA], the pixel selection period for signal readout is 25 [μs], and the frame rate is 60.
When calculated as [fps], the temperature rises by about 30 [K]. This temperature rise is very large when compared with the above-mentioned temperature rise of 5 [mK] due to the incidence of infrared rays.
It turns out that solving the self-heating problem is very important.

Temperature change of the pixel due to self-heating (voltage: V
An example of (sig conversion) is shown in FIG. As is clear from the figure, the pixel temperature rapidly rises due to the pixel selection during the row selection period, and is gradually cooled by the thermal time constant of the thermoelectric converter after the pixel selection pulse is turned off.

According to the above calculation, the temperature change due to self-heating is 30 [K], and the temperature signal due to the incidence of infrared rays of only about 5 [mK] is at a level lower than the thickness of the curve in FIG. As a result, in a general column amplifier circuit connected to a signal line, a weak current flows in the initial stage of pixel selection, and the amount of signal current increases with time due to self-heating during pixel selection. In operation, most of the current components are temperature information currents caused by self-heating, that is, noise currents.

FIG. 12 schematically shows the outline of the electric charge integrated and accumulated in the storage capacitor on the output side of the column amplifier circuit as a potential well diagram of the storage capacitor. As is apparent from the figure, most of the accumulated charge is a charge Q _SH by self-heating, the signal charge Qsig is slight.

FIG. 3 shows the result of temperature change due to self-heating,
It also shows a state in which the current in the latter half of the pixel selection period is large, and as a result, the information of the last stage is weighted from the latter half of the pixel selection period. As a result, the effective sampling time is shortened, and the signal band is expanded, thereby causing an increase in random noise.

In the case of using a bolometer based on the operating principle of the temperature change of the electric resistance value, a method of avoiding the above-described self-heating problem by forming a bridge circuit has been proposed by X. Gu, et al.
al. (X. Gu, et al., Sensors and Act
uators A, Vol. 69, p. 92, 1998).

They arrange reference insensitive pixels having the same heat capacity and low thermal resistance for each column, constitute a bridge circuit, and amplify the difference.

This method utilizes the fact that the temperature rise due to self-heating during the pixel selection period, which is a very short time, is mainly governed by the heat capacity with respect to the thermal time constant.

However, although this method has the effect of reducing the effect of self-heating, it is an approximate solution to the self-heating problem, and it cannot be said that the self-heating problem has been completely solved.

In order to solve the strict self-heating problem, it is necessary to arrange the reference insensitive pixels one-to-one with respect to each sensitive pixel. Therefore, the pixels are laid out two-dimensionally. There is no real solution in the image sensor.

This is because arranging the reference insensitive pixels constituting the bridge circuit in each pixel means that if the pixel size is the same, there is a disadvantage that the sensitivity is reduced to half or less. Therefore, the self-heating cancellation by the bridge circuit cannot be said to be effective because of the advantages and disadvantages of solving the self-heating problem.

The self-heating problem has not been solved in a thermoelectric conversion pixel using a column amplifier circuit according to the technical field of the present invention, for example, a pn junction type infrared sensor. An object of the present invention is to solve such a problem.

[0028]

According to a first aspect of the present invention, a plurality of rows and columns are arranged in a matrix, and the heat generated by absorbing incident infrared light is subjected to thermoelectric conversion to be extracted as a change in resistance value. Thermoelectric conversion pixels, a plurality of selection lines respectively connected to one of the rows or columns of the thermoelectric conversion pixels, and a plurality of signals respectively connected to the other of the rows or columns of the thermoelectric conversion pixels A pixel selection unit connected to each of the selection lines and selectively applying a readout voltage to the thermoelectric conversion pixel for each selection line to generate a voltage output signal on the signal line; a first input unit; Output signal amplifying means having two input means, wherein the first input means is connected to each of the signal lines to amplify a voltage output signal from the thermoelectric conversion pixel, and a second one of the output signal amplifying means. Connected to the input means, A compensation voltage is applied to the thermoelectric conversion pixel by applying a voltage having a waveform that cancels or reduces a voltage component included in the voltage signal due to a resistance change component caused by self-heating generated by the readout current in synchronization with the readout voltage. And an infrared sensor device comprising:

A second aspect of the present invention is that an infrared absorbing portion is arranged two-dimensionally on a semiconductor substrate and absorbs incident infrared light and converts it into heat, and converts a temperature change caused by heat generated by the absorbing portion into an electric signal. A thermoelectric conversion pixel having a thermoelectric conversion unit for performing the operation, a pixel selection unit connected to the thermoelectric conversion pixel and reading the signal from the thermoelectric conversion pixel, and selecting the thermoelectric conversion pixel; and a pixel selection unit. An infrared sensor device comprising: a pixel signal readout unit that reads out a signal from the thermoelectric conversion pixel selected by: and an output unit that outputs the signal that is read out by the pixel signal readout unit. The reading means includes an amplifier circuit for amplifying a signal from the thermoelectric conversion pixel,
This amplifier circuit has a MOS transistor, and at least a signal from the thermoelectric conversion pixel is a voltage signal,
Means for applying a ramp waveform voltage or a step waveform voltage synchronized with the pixel selection timing of the pixel selection means to the source of the MOS transistor, the voltage being input to the gate of the OS transistor and suppressing the increase in the voltage signal. An infrared sensor device characterized in that:

According to the present invention, in order to solve the problem of self-heating of the thermoelectric converter due to Joule heat generated due to pixel selection in the thermal infrared sensor, a voltage signal from the thermoelectric converter is input to the gate. M for amplification of amplifier circuit
A ramp waveform voltage or a step waveform voltage synchronized with the pixel selection pulse is applied to the source of the OS transistor. As a result, the self-heating component voltage can be removed from the gate-source voltage: Vgs of the amplification transistor, and an infrared sensor with high sensitivity, low noise, and a wide dynamic range can be obtained.

Further, according to the present invention, a plurality of voltage generators are alternately operated each time one row or a plurality of rows of pixels are selected, so that a pulse waveform voltage having an appropriately long time constant is applied to the source of the MOS transistor. , The self-heating component voltage can be removed from the gate-source voltage: Vgs of the amplifying transistor in the same manner as applying the ramp waveform voltage, and a high-sensitivity, low-noise, wide dynamic range infrared sensor device can be provided. Obtainable.

Further, according to the present invention, there is provided an insensitive pixel column in which one or more heat separation insensitive pixels are arranged in each row,
By applying a voltage based on the output voltage from the insensitive pixel column to the source of the amplifying transistor, a self-heating component is obtained from the gate-source voltage: Vgs of the amplifying transistor in the same manner as applying a ramp waveform voltage. The voltage can be removed, and an infrared sensor device with high sensitivity, low noise, and wide dynamic range can be obtained.

[0033]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of an infrared sensor device according to a first embodiment of the present invention, and shows a two-dimensional matrix configuration of m × n pixels in m rows and n columns (m and n are natural numbers of 2 or more).

An infrared detecting thermoelectric conversion pixel 1 for converting incident infrared light into an electric signal is two-dimensionally arranged on a semiconductor substrate 2 to form an imaging area 3. Inside the imaging area 3, a row selection line 4 (4-1, 4-2...) And a vertical column signal line 5 (5-1, 5-2...) Are arranged. For pixel selection, a row selection circuit 40 and a column selection circuit 70 are arranged adjacent to each other in the row direction and the column direction of the imaging region 3, and are connected to the row selection line 4 and the column selection line 7, respectively.

Load MOS transistors 8-1, 8-2,... Are connected to the column signal lines 5 of each column as a constant current source 80 for obtaining a pixel output voltage.

In FIG. 1, the substrate voltage: Vs is applied to the source of the load MOS transistor. However, it is possible to adjust the source voltage if necessary, which is more preferable.

In the row selected by the row selection circuit 40, the power supply voltage: Vd is applied to the row selection line 4, for example, 4-1.
Vs is applied to a row selection line not selected by the row selection circuit 40. As a result, the pn junction regions 115 inside the thermoelectric conversion pixel 1 in the selected row 4-1 become forward biased and a bias current flows, and the operating point is determined by the temperature of the pn junction inside the pixel and the forward bias current, Pixel signal output voltages are generated on the column signal lines 5-1 and 5-2 of each column. At this time, the pn junction regions 115a,... Of the pixels not selected by the selection circuit 40 are reverse biased. That is, the pn junction inside the pixel has a function of selecting a pixel.

The voltage generated on the column signal line 5 is a very low voltage, and it is assumed that the ratio between the subject temperature change dTs and the pixel temperature change dTd is 5 × 10 ^−3. According to the thermoelectric conversion sensitivity when eight pn junctions are connected in series: dV / dTd = 10 [mV / K], when dTs = 0.1 [K], only 5
[ΜV].

Therefore, in order to recognize the object temperature difference, it is necessary to reduce the noise generated on the column signal line to 5 [μV] or less. The value of this noise is about 1 of the noise of the CMOS sensor which is a MOS type visible light image sensor.
/ 80, very low. The column amplifier circuit 9 is connected between each of the signal lines 5-1 and 5-2 and the column selection transistor group 60, and each signal line is connected to the gate 10g of the amplifying MOS transistor 10 of the amplifier circuit. On the drain 10d side of the MOS transistor 10, a storage capacitor 12 for integrating and storing the amplified signal current is connected. The accumulation time for integrating the signal current depends on the row selection circuit 40.
And is determined by the row selection pulse applied to the row selection line 4.

The storage capacitor 12 is connected to a reset transistor 14 for resetting the voltage of the storage capacitor.
After the reading of the signal voltage by the column selection transistor 6 is completed, the reset operation is performed. Terminal 24 is an output terminal.

FIGS. 2A and 2B illustrate the structure of the thermoelectric conversion pixel 1 for infrared detection according to the present embodiment. FIG.
(B) is a sectional view. The thermoelectric conversion pixel 1 including the pn junction region 115 for thermoelectric conversion is formed on the hollow structure 107 formed inside the single crystal silicon semiconductor substrate 106 and the infrared absorption units 118 and 120 and for thermoelectric conversion. A pn junction region 115 inside the SOI layer 108, a wiring 117 connecting the pn junction region 115, and a thermoelectric converter 110 of a buried silicon oxide film layer 114 supporting the SOI layer 108
Consisting of The figure shows a diode structure in which two pn junction regions are arranged for explanation. Further, the supporting portion 1 for supporting the pixel 1 through the hollow bottom portion 107 and the hollow side portion 119 having a hollow structure and outputting an electric signal from the pixel 1.
And a connection portion (not shown) for connecting the pixel 1 to the column signal line 5 and the row selection line 4. Pixel 1
In addition, since the support portion 111 is provided on the hollow structure 107, the heat dissipation of the pixel becomes slow, and the temperature of the element 1 is efficiently modulated by incident infrared rays.

The manufacturing method for realizing such a structure is described in the prior patent application relating to the invention of the present inventors, for example, Japanese Patent Application Nos. 2000-298277 and 2000-0.
95678 and the like.

According to the first embodiment of the present invention, a voltage generator 300 is mounted on a semiconductor substrate as shown in FIG. When the selection pulse is input, a ramp waveform voltage as shown in FIG. 3 synchronized with the row selection pulse is generated in the row selection period, and the source voltage of the source 10 s of the amplification transistor 10 in the column amplification circuit 9 is input. Supply. Although the temperature rise due to the self-heating of the pixel, which has already been described, is shown in FIG. 11, the thermal time constant of this temperature rise is determined by the thermal separation of the thermoelectric conversion pixel 1, and is generally
[ms] order.

On the other hand, as shown in FIG. 11, since the row selection period is on the order of [μs], it is very short compared to the above thermal time constant, and in this row selection period, linear approximation is sufficiently possible. It is. Therefore, the amplification transistor 1
The voltage of the self-heating component generated in the column signal line 5 applied to the gate 10g of 0 is canceled out by applying the ramp waveform voltage to the source 10s of the amplification transistor 10, and the temperature change due to the incidence of infrared rays Only the signal of the component can be amplified.

As a result, the operating point of the amplifying transistor 10 is optimized, the current can be amplified only for the signal component without the self-heating component, the gain can be improved, and the random noise due to the band expansion can be reduced. There is no increase. Therefore, an infrared sensor with high sensitivity, low noise, and wide dynamic range can be obtained.

In the second embodiment of the present invention, FIG.
A voltage generator 300 for generating a step waveform voltage is mounted on a semiconductor substrate, and the voltage generator 300 receives a row selection pulse from a row selection circuit 40 to generate a step waveform synchronized with the row selection pulse. A voltage is generated as shown in FIG.
It is supplied as a source voltage of the amplifying transistor 10 inside.

In order to generate the step waveform voltage, for example, a D / A conversion circuit can be used. By appropriately setting the number of bits, the same effect as when a ramp waveform voltage is applied can be obtained. The effect can be obtained. Moreover, there is an advantage that the waveform line can be finely adjusted.

Therefore, similarly to the first embodiment, the voltage of the self-heating component generated on the column signal line 5 and applied to the gate of the amplification transistor 10 as the first input is differentially controlled in a direction to suppress the increase. The above-described step waveform voltage is applied to the source of the amplifying transistor 10 and is canceled out, and only the signal of the temperature change component due to the incidence of infrared rays can be amplified.

As a result, the operating point of the amplifying transistor 10 is optimized, the current can be amplified only for the signal component having no self-heating component, and the gain can be improved.
In addition, random noise caused by the above-mentioned band expansion does not increase. Therefore, an infrared sensor with high sensitivity, low noise, and wide dynamic range can be obtained.

Further, as a modification of the first and second embodiments, the voltage generator 300 can be mounted outside the semiconductor substrate. The voltage generator 300 includes the row selection circuit 4
When a row selection pulse from 0 is input from the row selection pulse output unit 21, a ramp waveform or a step waveform voltage synchronized with the row selection pulse is generated as shown in FIGS. The voltage is supplied as a source voltage of the amplification transistor 10 in the column amplification circuit 9 to the amplification transistor source voltage input section 22 on the substrate.

Therefore, similarly to the first and second embodiments, the voltage of the self-heating component generated on the column signal line 5 applied to the gate of the amplification transistor 10 is obtained by changing the above-mentioned step waveform voltage to the source of the amplification transistor 10. By applying the voltage to 10 s, the signals are canceled out, and only the signal of the temperature change component due to the incidence of infrared rays can be amplified.

As a result, the operating point of the amplifying transistor 10 is optimized, the current can be amplified only for the signal component having no self-heating component, and the gain can be improved.
In addition, random noise caused by the above-mentioned band expansion does not increase.

Next, a third embodiment of the present invention is shown in FIGS. 1 have the same reference numerals. This embodiment is the same as the configuration shown in FIG. 1 except that the voltage generator 301 is a generator for generating a rectangular wave voltage, and an integrating circuit 302 is arranged between the source voltage input terminals 22 of the amplifying transistors. The voltage generator 301 is mounted inside the semiconductor substrate, and the row selection pulse from the row selection circuit 40 is input from the row selection pulse output unit 21 to synchronize the rectangular wave voltage V1 with the row selection pulse (FIG. 6A). Occurs.

In this embodiment, the voltage generator 301
And amplifying transistor source voltage input section 2 on the semiconductor substrate
An integration circuit 302 including a capacitance 303 is provided on the wiring 23 between the first and second wirings. When a rectangular wave voltage pulse V1 synchronized with the row selection pulse is input to the integration circuit 302 as shown in FIG. 6A, the integration circuit 302 changes the integration waveform voltage V2 shown in FIG. The source voltage of the amplification transistor 10 in the column amplification circuit 9 is supplied to the upper amplification transistor source voltage input unit 22. This integral ramp waveform can be approximated to the voltage of the self-heating component included in the input signal of the amplification transistor, and therefore is applied to the gate 10g of the amplification transistor 10 as in the first and second embodiments. Column signal line 5
The voltage of the self-heating component generated in the above is canceled by applying the above-mentioned integrated waveform voltage to the source of the amplification transistor 10, so that only the signal of the temperature change component due to the incidence of infrared rays can be amplified.

As a result, the operating point of the amplifying transistor 10 is optimized, the current can be amplified only for the signal component having no self-heating component, and the gain can be improved.
In addition, random noise caused by the above-mentioned band expansion does not increase.

As a modification of the third embodiment, the voltage generator 301 and the integrating circuit 302 can be mounted outside the sensor chip.

FIGS. 7 and 8 show a fourth embodiment.
The same reference numerals as those in FIG. 1 indicate the same parts. In this embodiment, pixels are grouped every other row into two groups, for example, divided into two groups of odd rows and even rows, and a first group of voltage generators 304 and a second group of voltage generators 305 are alternately operated. It is to let. This embodiment adds a sampling and holding (S / H) circuit for 1H period for the purpose of reducing random noise,
Most of the 1H period is driven as a row selection period, that is, a pixel selection period as shown in FIG.

Alternatively, the signal charges accumulated by the column amplification operation are moved to the added sample and hold circuit,
A circuit configuration and a driving method that output at a timing delayed by one row are also possible. In this case, all rows are processed by the same circuit, so that generation of fixed pattern noise such as so-called horizontal stripes every other row is performed. Can be suppressed, and therefore it is more preferable.

In the case of such a drive, the non-selection period t1 of the pixel selection pulses of two consecutive rows is short depending on the time constant set by the additional capacitance, and therefore, as shown in FIG. The voltage Vs' at the source voltage input section of the amplifying transistor does not drop sufficiently like Vs ", and the circuit does not operate normally.

Therefore, in this case, a plurality of voltage generators 304 and 305 corresponding to the two groups are provided, and a plurality of amplifying transistor source voltage input sections 22 are provided.
A configuration for switching every other line is added. Thus, when the two voltage generators 304 and 305 are provided, the voltage Vs having the waveforms shown in FIGS. 8B and 8C is output alternately every other row, and also inside the sensor chip. The voltage Vs shown in FIGS. 8B and 8C every other row,
Vs is supplied as the source voltage of the amplification transistor in the column amplification circuit 90.

Accordingly, similarly to the first to third embodiments, the voltage of the self-heating component generated on the column signal line 5 applied to the gate 10 g of the amplification transistor 10 is obtained by subtracting the above-mentioned step waveform voltage from the amplification transistor 10. Source 1
By applying 0 s, the signal is canceled and only the signal of the temperature change component due to the incidence of infrared rays can be amplified.

As a result, the operating point of the amplifying transistor 10 is optimized, the current can be amplified only for the signal component without the self-heating component, and the gain can be improved.
In addition, random noise caused by the above-mentioned band expansion does not increase. Therefore, an infrared sensor with high sensitivity, low noise, and wide dynamic range can be obtained.

The fifth embodiment of the present invention will be described with reference to FIGS.
Explanation will be made using 0. The thermoelectric conversion pixel 1 has the same structure as the hollow support structure of the pn junction region described with reference to FIG. 2, and includes a constant current source 80 using a load transistor and a row selection circuit 4.
0, row selection line 4, column selection circuit 70, column signal line 5, column selection transistor group 60, column amplification circuit group 90, etc.
Therefore, the description of this part is omitted.

In this embodiment, as shown in FIG. 9, the last column of the pixel matrix is provided as a heat-separation insensitive pixel column 500, and heat-separation insensitive pixels 501 are distributed and provided in each row. The structure of the thermal separation insensitive pixel 501 is as follows:
As shown in FIG. 10, the pixel structure is almost the same as that of FIG. 2, except that an infrared reflection layer 130 made of a metal film such as aluminum is provided on the infrared absorption layer 118.

In the thermal separation insensitive pixel 501,
The incident infrared rays are reflected by the infrared reflection layer 130, and no temperature change occurs due to the incident infrared rays, and only the self-heating signal by the pixel selection is output to the column signal line 502.

The column signal line output from the thermal separation insensitive pixel column 500 is supplied to the amplifying transistor 10 (see FIG. 1) in the column amplifying circuit 90 via the source follower circuit 400 as shown in FIG. Can be supplied as a source voltage.

It is needless to say that the adjustment of the operating point can be optimized by appropriately adjusting the voltages of the terminals 401 and 402 of the source follower circuit. Therefore, as in the first to fourth embodiments, the voltage of the self-heating component generated on the column signal line 5 in the output signal, which is applied to the gate of the amplification transistor 10, is equal to the waveform voltage of the column signal line. By applying the voltage to the source input section 22 of the amplification transistor 10, the signal is accurately canceled, and only the signal of the temperature change component due to the incidence of infrared rays can be amplified. By mounting the insensitive pixel on the same semiconductor substrate, the self-heating component is output as a voltage having almost the same tendency, so that the obtained waveform can be applied as it is.

As a result, the operating point of the amplifying transistor 10 is optimized, the current can be amplified only for the signal component having no self-heating component, and the gain can be improved.
In addition, random noise caused by the above-mentioned band expansion does not increase. Therefore, an infrared sensor with high sensitivity, low noise, and wide dynamic range can be obtained.

Although FIG. 9 shows a case in which a single-stage source follower circuit 400 is provided, the source follower circuit may be changed to a multi-stage source follower circuit if necessary.

The circuit 400 is not limited to the source follower circuit, but can be changed as appropriate as long as it does not affect the output voltage of the thermal isolation insensitive pixel column signal line.

As described above, the present invention has been described in the embodiment as a column amplifier circuit composed of a single amplification MOS transistor having a first input as a gate and a second input as a source as an output signal amplifier. This amplifier circuit is preferable in terms of manufacturing because of its simple configuration. However, other amplifier circuits such as a differential amplifier can be used as long as they have two inputs.

In the present embodiment, the thermoelectric conversion pixel has been described using a pn junction. However, the present invention is not limited to this. For example, the thermoelectric conversion pixel includes a bolometer such as vanadium oxide. It is also applicable to an infrared sensor device.

In this case, it goes without saying that a selection transistor for selecting a pixel is required in each pixel.

In addition, various modifications can be made without departing from the spirit of the present invention.

[0075]

According to the present invention, a thermal infrared sensor having high sensitivity, low noise, and wide dynamic range can be obtained.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of first and second embodiments of the present invention.

FIGS. 2A and 2B are views for explaining thermoelectric conversion pixels according to the first and second embodiments, wherein FIG. 2A is a plan view and FIG. 2B is AA of FIG.
A sectional view taken along a line.

FIGS. 3A and 3B are waveform diagrams illustrating a first embodiment.

FIGS. 4A and 4B are waveform diagrams illustrating a second embodiment.

FIG. 5 is a configuration diagram of a third embodiment of the present invention.

FIGS. 6A and 6B are waveform diagrams illustrating a third embodiment of the present invention.

FIG. 7 is a configuration diagram of a fourth embodiment of the present invention.

FIGS. 8A, 8B, and 8C are waveform diagrams illustrating a fourth embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of a fifth embodiment of the present invention.

10A and 10B are views for explaining a thermoelectric conversion pixel according to a fifth embodiment, in which FIG. 10A is a plan view, and FIG. 10B is a cross-sectional view taken along line AA of FIG.

FIG. 11 is a diagram illustrating a state in which the pixel temperature Td and the output signal voltage Vsig rapidly change due to self-heating during a row selection period, and the pixel temperature returns to its original state over one frame period.

[12] the storage capacity of the internal column amplifier circuit, and the noise charges Q _SH due to the signal charge Qsig and self heating, potential wells diagram schematically showing the manner in which accumulated during the pixel selection period.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Thermoelectric conversion pixel 2 ... Semiconductor substrate 3 ... Image pick-up area 4 ... Row selection line 5 ... Column signal line 6 ... Column selection transistor 7 ... Column selection line 8 ... Load transistor 9 ... Column amplification circuit 10 ... MOS amplification transistor 12 ... Storage Capacitor 14 Reset transistor 21 Pixel selection pulse output unit 22 Source voltage input unit of amplifying transistor 23 Wiring 24 Signal output unit 40 Row selection circuit 60 Column selection transistor group 70 Column selection circuit 80 Constant current circuit 90 column transistor group 106 semiconductor substrate 107 hollow bottom part 108 SOI layer 110 thermoelectric conversion part 111 support leg 114 embedded oxide film 115 pn junction region 117 wiring 118 infrared ray absorbing part 119 hollow side part 120 ... Infrared absorbing section 130 ... Infrared reflecting layer 300 ... Voltage generator 400 ... Source Follower circuit 401: Source follower circuit terminal 402: Source follower circuit terminal 500: Thermal separation insensitive pixel row 501: Thermal separation insensitive pixel

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01J 5/22 G01J 5/22 H01L 27/14 H01L 35/00 S 35/00 H04N 5/33 H04N 5 / 33 H01L 27/14 K F term (reference) 2G065 AA11 AB02 BA12 BA32 BA34 BE08 CA30 DA06 DA18 DA20 2G066 AC14 BA09 BB20 CA02 CA08 CA20 4M118 AA01 AA02 AB01 BA06 CA03 CA35 FA06 5C024 AX06 BX03 CX41

Claims (12)

[Claims] 1. A plurality of thermoelectric conversion pixels which are arranged in a matrix of a plurality of rows and columns and which thermoelectrically converts heat generated by absorbing incident infrared light and extracts the change as a change in resistance value; A plurality of selection lines respectively connected to either one of each row or each column of the thermoelectric conversion pixel; a plurality of signal lines respectively connected to the other one of each row or each column of the thermoelectric conversion pixels; and A pixel selection unit for selectively applying a readout voltage to the thermoelectric conversion pixel for each selection line to generate a voltage signal on the signal line; a first input unit and a second input unit; An output signal amplifying means connected to the first input means for amplifying a voltage signal from the thermoelectric conversion pixel; a second input means of the output signal amplifying means connected to the thermoelectric conversion pixel for reading out the signal. Voltage An infrared sensor comprising: voltage generating means for applying a voltage having a waveform that cancels or reduces a voltage component included in the voltage signal due to a resistance change component caused by self-heating generated in synchronization with the read voltage. apparatus. 2. The infrared sensor device according to claim 1, wherein the output signal amplifying means includes a plurality of output amplifying means which are independently connected to the plurality of signal lines. 3. An infrared absorbing portion which is two-dimensionally arranged on a semiconductor substrate and absorbs incident infrared light and converts it into heat, and a thermoelectric converter for converting a temperature change caused by heat generated by the absorbing portion into an electric signal. A thermoelectric conversion pixel having means, a pixel selection means connected to the thermoelectric conversion pixel, and for reading a signal from the thermoelectric conversion pixel, selecting the thermoelectric conversion pixel; and An infrared sensor device comprising: a pixel signal readout unit that reads a signal from a thermoelectric conversion pixel; and an output unit that outputs the signal read out by the pixel signal readout unit. An amplifying circuit for amplifying a signal from the thermoelectric conversion pixel;
A transistor, and at least an output signal from the thermoelectric conversion pixel is input as a voltage signal to a gate of the MOS transistor, and a source of the MOS transistor has a ramp waveform voltage synchronized with a pixel selection timing of the pixel selection unit or Means for applying a step waveform voltage so as to suppress an increase in the voltage signal. 4. The semiconductor substrate as a means for applying the ramp waveform voltage or the step waveform voltage, wherein the voltage generator generates a ramp waveform voltage or a step waveform voltage in synchronization with a pixel selection pulse from the pixel selection means. The infrared sensor device according to claim 3, wherein the infrared sensor device is formed on the upper surface. 5. A voltage generator for generating a ramp waveform voltage or a step waveform voltage synchronized with a pixel selection pulse from the pixel selection means as means for applying the ramp voltage or the step waveform voltage, outside the semiconductor substrate. The infrared sensor device according to claim 3, wherein the infrared sensor device is provided. 6. The thermoelectric conversion pixel includes at least a thermoelectric conversion unit and a support structure for supporting the thermoelectric conversion unit on a hollow structure formed inside the semiconductor substrate. 3. The infrared sensor device according to claim 1, further comprising a wiring for reading a signal from the thermoelectric converter, wherein the wiring is connected to the selection line and the signal line. 7. The pixel selection means has a pixel selection pulse output terminal, and a voltage generator for generating a rectangular wave voltage in synchronization with the pulse output is provided outside the semiconductor substrate. And a current path between the output terminal of the voltage generator and the source, wherein an integration circuit including at least one capacitance is added. 3. The infrared sensor device according to 3. 8. The infrared sensor device according to claim 7, comprising a plurality of said voltage generators. 9. An infrared absorbing portion that is two-dimensionally arranged in a plurality of rows and a plurality of columns on a semiconductor substrate and absorbs incident infrared light and converts it into heat, and electrically detects a temperature change caused by heat generated in the absorbing portion. A thermoelectric conversion unit having a thermoelectric conversion unit for converting into a signal, and a thermoelectric conversion pixel having a support structure for supporting the infrared absorption unit and the thermoelectric conversion unit on a hollow structure formed inside the semiconductor substrate. , The support structure includes:
At least a wiring for reading a signal from the thermoelectric conversion unit is included, and this wiring is connected to a row selection line and a column signal line, and outputs a pixel selection pulse for reading a signal from the thermoelectric conversion pixel to each of the above. Pixel selection means for selecting a thermoelectric conversion pixel by applying to a row selection line; pixel signal reading means for reading a signal from the thermoelectric conversion pixel selected by the pixel selection means from each of the column signal lines; An output unit for outputting a signal from the thermoelectric conversion pixel read by the reading unit, wherein the pixel reading unit amplifies a signal from the thermoelectric conversion pixel. The amplifier circuit includes at least a signal from the thermoelectric conversion pixel as a voltage signal, and a gate of the MOS transistor. The circuit includes a circuit for performing current modulation by applying a signal, and is provided with at least one heat separation insensitive pixel in each row on the semiconductor substrate, which is optically insensitive to infrared light and is supported on the hollow structure by the support legs. The thermal isolation insensitive pixel is arranged as an insensitive pixel column, and a voltage based on an insensitive column signal line voltage generated in the column signal line of the insensitive pixel column is supplied to a source of the MOS transistor. An infrared sensor device comprising input means. 10. A source follower circuit having at least a single-stage source follower circuit to which a reference voltage generated from the thermal isolation insensitive pixel is inputted, and wherein an output of the source follower circuit is inputted to a source of the MOS transistor. The infrared sensor device according to claim 9, wherein: 11. The infrared sensor device according to claim 9, wherein the thermal separation insensitive pixel has an infrared reflective layer formed on a surface of an infrared absorbing portion inside the thermoelectric conversion pixel. 12. A two-dimensional arrangement on a semiconductor substrate,
An infrared absorbing portion for absorbing incident infrared light and converting it into heat, and a thermoelectric converting portion for converting a temperature change due to heat generated in the absorbing portion into an electric signal, wherein the thermoelectric converting portion is a semiconductor substrate. A thermoelectric conversion pixel having a support structure for supporting on a hollow structure formed therein; the support structure includes at least wiring for reading a signal from the thermoelectric conversion unit; Pixel selection means for selecting the thermoelectric conversion pixel for reading a signal from the conversion pixel; pixel signal reading means for reading a signal from the thermoelectric conversion pixel selected by the pixel selection means; And an output unit for outputting a signal from the thermoelectric conversion pixel read out by the following. An infrared sensor which includes a circuit for performing a current modulation by applying at least a signal from the thermoelectric conversion pixel as a voltage signal to a gate of the MOS transistor, including a MOS transistor amplifier circuit for amplifying a signal; The method of driving the infrared sensor device, wherein a ramp waveform voltage or a step waveform voltage synchronized with a selection pulse of the thermoelectric conversion pixel is applied to a source of the MOS transistor.