JP2558966B2 - Infrared detector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pyroelectric infrared detector.

[0002]

2. Description of the Related Art As a pyroelectric infrared sensor, various types have been conventionally known, for example, those using a single crystal,
Some include ceramics and organic materials. The conventional infrared sensor is manufactured as a single unit, and when configured as an infrared detection device, the sensor unit, the resistor, and the FE are used.
T etc. were contained in the package.

[0003]

However, when an infrared sensor as a single unit, a resistor, and a FET are put in one package to form an infrared detecting device, an output signal of a high impedance sensor section is taken out through wiring. Therefore, the noise characteristic is deteriorated. Further, there is a limit to miniaturization, and a resistive element having a high resistance of about 1 GΩ is required.

Therefore, it is desired to integrate such a sensor portion, resistance, FET for impedance conversion, and the like into one chip. However, in order to make the pyroelectric element function for infrared detection, a work called polling is required, so that it is not easy to make it into one chip. That is, a high voltage is applied to the sensor portion in the polling step, but if this is executed in a one-chip state, the FET and the like will be destroyed. Therefore, it is not easy to provide an infrared detection device in which pyroelectric elements are arranged in an array. The present invention is intended to solve the problems of the prior art.

[0005]

In an infrared detector according to the present invention, a plurality of detection units are formed on a semiconductor substrate, and each of these detection units includes an impedance conversion element formed on the semiconductor substrate and the impedance conversion element. A pyroelectric element formed by interposing a pyroelectric material between a first electrode connected to a control electrode of a conversion element and a second electrode provided so as to face the first electrode; and a pyroelectric element formed on a semiconductor substrate. The semiconductor device includes a first diode having an anode terminal connected to the first electrode and a second diode formed on the semiconductor substrate and having a cathode terminal connected to the first electrode. Then, a switch element is provided for each detection unit,
ON / OFF control is individually performed by the scanning means, and in each detection unit, the second electrode of the pyroelectric element, the cathode terminal of the first diode, and the anode terminal of the second diode are provided. During, a high voltage is applied during poling.

[0006]

According to the invention, each detection unit has a first and a second diode respectively connected in anti-parallel, so that it acts as a low resistance to a high voltage during poling and therefore The pyroelectric element can be polled without imposing an excessive load on the impedance conversion element, and it also functions as a high resistance against a minute signal current when used as a sensor, thus enabling impedance conversion of the output of the pyroelectric element. To do.

[0007]

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

FIG. 1 shows the structure of an embodiment of the present invention. FIG. 1A is a plan view, FIG. 1B is a sectional view taken along line A ₁ -A ₂ , and FIG. 1C is B ₁ -B. it is a _two-wire cross section. Semiconductor substrate 40
N junction type FETs (J-FETs) 20 _{1 to} 20 _n
Are provided in an array as impedance conversion elements,
N anti-parallel diode circuits 30 ₁ to 30 _n are provided in an array along the array of J-FETs 20 _{1 to} 20 _n . And, the J-FET20 ₁ ~20 _n gates 21 ₁ through 21 _n, the pyroelectric element 10 ₁ to 10 _n each lower electrode 11 ₁ to 11 _n of provided connection, pyroelectric thereon The effect material layer 12 and the upper electrode 13 are provided in each pyroelectric element 1
It is commonly provided for 0 ₁ to 10 _n .

[0009] Figure 2 is the array of detection units, analog switch FET 15 ₁ to 15 _n and the scanning circuit 16
It is the circuit diagram which combined. In the above circuit, when a high voltage is applied between the common voltage terminals C1 and C2, the pyroelectric elements 10 ₁ to 10 _n can be polled all at once. When used as a sensor, a constant bias is applied between C1 and C2, and the scanning signal of the scanning circuit 16 is sequentially applied to the gates of the analog switch FETs 15 ₁ to 15 _n to be extracted as a video signal. You can

The more detailed structure and operation of the above embodiment will be described below.

FIG. 3 shows the structure of one detection unit,
The figure (a) is a circuit diagram and the figure (b) is a schematic diagram of a cross section. As illustrated, the gate 21 of the junction type FET (J-FET) as the impedance conversion element has a pyroelectric element 1
The lower electrode 11 of 0 is connected, and the anodes and cathodes of the diodes D1 and D2 which are in an antiparallel relationship are connected. The anti-parallel diode circuit 30 is formed on the same substrate as the semiconductor substrate 40 on which the J-FET is formed. On the lower electrode 11 of each pyroelectric element, a pyroelectric effect material layer 12 made of, for example, an organic material, is provided for each pyroelectric element 10.
₁ to 10 _n are commonly deposited, and the upper electrode 13 made of an infrared absorbing material is commonly formed on the upper surface thereof to configure each of the above-mentioned n pyroelectric elements 10.

In the above structure, the pyroelectric effect material layer 12
At the time of polling, a high voltage is applied between the common electrodes C1 and C2. Then, a voltage equal to or higher than the level shift voltage of the diodes D1 and D2 is applied to all the anti-parallel diode circuits 30 ₁ to 30 _n , so that the polling current is equivalently conducted as a low resistance element. Therefore, the common pyroelectric effect material layer 12 is formed on each lower electrode 11 ₁
While polled every ~ 11 _n , J-FET2
No excessive voltage is applied to the gate of 0 _{1 to} 20 _n . When used as an infrared sensor, the pyroelectric element 10
The potential difference of each sensor caused by the pyroelectric effect is low voltage, and therefore, a voltage equal to or lower than the level shift voltage of the diodes D1 and D2 is applied to the respective anti-parallel diode circuits 30 ₁ to 30 _n . Therefore, the anti-parallel diode circuits 30 equivalently function as sufficiently high resistance elements, and the impedance conversion by the J-FETs 20 _{1 to} 20 _n is individually and suitably performed.

Next, a specific example of the above embodiment will be described with reference to FIG.

An n-type silicon layer 41 is formed on the n-type silicon substrate 40 by an epitaxial growth method, and each J-
The formation regions of the FETs 20 _{1 to} 20 _n are junction-separated by the p-type isolation layers 42 _{1 to} 42 _n , respectively. Then, the p-type gate region 21 ₁ is formed in the J-FET region.
21 _n , n-type source regions 22 _{1 to} 20 _n, and n-type drain regions 23 ₁ to 23 _n are formed. In the diode region, p-type regions 31 _{1 to} 31 _n are formed, in which n-type cathode regions 32 _{1 to} 32 _n and p-type anode regions 33 _{1 to} 33 _n are formed. , And the anti-parallel diode circuit 30
₁ to 30 _n are configured.

An insulating film 61 made of SiO ₂ is formed on such a substrate, and p-type gate regions 21 ₁ to 2 are formed.
1 _n , n-type cathode regions 32 _{1 to} 32 _n, and p-type anode regions 33 _{1 to} 33 _n are individually formed with openings in the insulating film 61. Then, the anti-parallel diode circuit 30 ₁
To 30 _n extraction electrode 71 ₁ ~71 _n, 72 ₁ ~72
with _n is formed, the lower electrode 11 ₁ to 1 connected to p-type gate region 21 ₁ through 21 _n is on J-FET region
1 _n is formed of, for example, aluminum or a nickel chromium alloy. A single pyroelectric effect material layer 12 is commonly formed on the lower electrodes 11 _{1 to} 11 _n , and a single upper electrode 13 made of nickel-chromium alloy or gold black is commonly formed thereon. . Then, a part of the insulating film 61 is S
Another insulating film 62 made of iO ₂ (may be SiN or the like)
It is covered with.

In the infrared detecting device having the above structure, the pyroelectric effect material layer 12 is formed by spin coating an organic material. So-called polling is required in order to allow it to exhibit the pyroelectric effect, which is done after the device of FIG. 4 is completed.

FIG. 5 shows a modification of the infrared detector shown in FIG. This is different from FIG. 4 in that the n-type silicon substrate 40 and the n-type silicon layer 41 are removed by etching from the back surface, and the pyroelectric elements 10 ₁ to 10 _{n are} removed.
That is, it is thinned in the formation region. By doing so, the pyroelectric elements 10 ₁ to 10 _{n can be connected} to the n-type silicon substrate 4
Since the heat radiation to the 0- and n-type silicon layers 41 can be reduced, it is possible to detect infrared rays with higher sensitivity. FIG. 6 is a circuit diagram of a detection unit according to another embodiment. As illustrated, the source of the J-FET 1 for impedance conversion is connected to the drain of another J-FET 2 serving as a current source. And, the drain of the J-FET2 is connected to the power supply terminal C3, the voltage V _B of the current control is applied to the gate. In this circuit, the output signal OUT is J-FE.
It is taken out from the source electrode of T1. According to this circuit, the infrared sensor and the current source can be integrated, which makes it easier to handle.

[0018]

As described above in detail, according to the infrared detecting apparatus of the present invention, since each detecting unit has a diode connected in anti-parallel, it is possible to prevent a high voltage during polling. Acts as a low resistance, and therefore can poll the pyroelectric element without imposing an excessive load on the impedance conversion element, and also acts as a high resistance to a low voltage when used as a sensor, and thus the output of the pyroelectric element. Enables impedance conversion. Therefore, the array type pyroelectric sensor unit and the J for impedance conversion are used.
-It becomes possible to integrate the FET, the resistor, and the like into one chip. As described above, it is obvious that a MOS FET may be used to obtain the same effect.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an infrared detection device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a circuit configuration of the embodiment shown in FIG.

FIG. 3 is a diagram showing a configuration of a detection unit according to the embodiment shown in FIG.

FIG. 4 is a diagram illustrating a specific example of FIG.

FIG. 5 is a diagram showing a modification of the infrared detection device shown in FIG.

FIG. 6 is a circuit diagram of a detection unit having an infrared detection device according to another embodiment of the present invention.

[Explanation of symbols]

10 ₁ to 10 _n ... Pyroelectric element 11 _{1 to} 11 _n ... Lower electrode 12 ... Pyroelectric effect material layer 13 ... Upper electrode 21 _{1 to} 21 _n ... P-type gate region 22 _{1 to} 22 _n ... N-type source region 23 ₁ to 23 _n ... n-type drain region 30 ₁ to 30 _n ... anti-parallel diode circuit 31 _{1 to} 31 _n ... p-type region for diode

Claims (4)

(57) [Claims] 1. A plurality of detection units are formed on a semiconductor substrate, and each of the detection units includes an impedance conversion element formed on the semiconductor substrate and a first electrode connected to a control electrode of the impedance conversion element. a pyroelectric element pyroelectric material formed is interposed between the second electrode provided so as to face the front
An anode end is formed on the semiconductor substrate and is formed on the first electrode.
A first diode to which a child is connected and the semiconductor substrate
Formed, and the cathode terminal was connected to the first electrode
Is constituted by a second diode, the plurality of impedance conversion elements a plurality of switching elements connected respectively to further comprise a scanning means the respectively ON / OFF controlling the switch element, the plurality of detection units In each, the pyroelectric element
A second electrode of the child and a cathode end of the first diode
Between the child and the anode terminal of the second diode
In addition, an infrared detector characterized in that a high voltage is applied at the time of polling . 2. The infrared detection according to claim 1, wherein the semiconductor substrate is partially thinned by etching from the back surface, and the pyroelectric element is extended on the thinned semiconductor substrate. apparatus 3. The infrared detection device according to claim 1, wherein a plurality of current source circuits are formed on the semiconductor substrate and are connected to the impedance conversion elements, respectively. 4. The infrared detection device according to claim 1, wherein the plurality of switch elements and the scanning means are formed on the semiconductor substrate.