JP2000308093A - Infrared picture generation element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise the heat resistant temperature of a picture element without deteriorating an opening rate and to obtain the infrared picture generation element having a large dynamic range by forming a part of a wiring used in respective picture elements, from a metallic wiring whose main material is high melting point metal. SOLUTION: Relating to an infrared picture generation element 1, a field oxide film for separation 32, a gate electrode 33 formed of polysilicon and the like and N-type impurity areas 34 and 35 are formed on a semiconductor substrate 31 formed of P-type silicon and the like. A conduction control transistor 12 is formed of the gate electrode 33 and the N-type impurity areas 34 and 35. A power wiring 37 formed of a material whose main material is the high melting point metal of W and Ti is electrically connected to the N-type impurity area 35 forming the drain of the conduction control transistor 12. The conduction control transistor 12 controls current flowing in a heat generation resistance body 11. Thus, the heat resistant temperature of a picture element can be improved and a maximum temperature at the time of real use can be set to be high.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared image generating device for use in a performance test of an infrared imaging system.

[0002]

2. Description of the Related Art A large number of solid-state imaging devices have been developed in which a large number of photodetectors are arranged in an array on a semiconductor substrate and provided with a readout circuit for reading out signal charges from each photodetector. Among them, an infrared solid-state imaging device using an infrared detector as a light detector has been put into practical use as an infrared imaging system in combination with an optical system, a drive circuit, a signal processing circuit, an element cooler, etc. It is used in various fields such as measurement and remote sensing. As the infrared detector used in the infrared solid-state imaging device, a quantum sensor that generates a photocurrent by photoelectric conversion, a thermal sensor that detects a rise in temperature due to incident infrared light by a change in electrical characteristics, and the like are used. It is used properly according to.

[0003] In the infrared imaging, an image is formed by detecting that the intensity of infrared radiation radiated varies depending on the temperature of a subject. However, the imaging result largely depends on ambient environmental conditions such as temperature and infrared transmittance of the atmosphere. Is done. For this reason,
The infrared imaging system is designed / manufactured according to the environmental conditions in which it is used, and it is desirable that the final performance test be performed in the same environment as when actually used. However, depending on the application, it is often difficult to perform a test in a real environment. Instead, it has been desired to develop a test apparatus that can simulate the real environment.

[0004] An infrared image generating apparatus has been developed in response to such a demand, and includes an infrared image generating element, an optical system,
It is composed of a drive circuit, a signal processing unit and the like. The infrared image generating element is composed of micro heating elements arranged in a two-dimensional array. Each of the heating elements is heated to a desired temperature according to an input signal to generate an infrared image corresponding to a real environment. Can be.

FIG. 5 is a sectional view of a pixel showing a structure of one pixel in a conventional infrared image generating element. In FIG. 5, an infrared image generating element 100 includes a field oxide film 102 for isolation and a gate electrode 103 made of polysilicon or the like on a semiconductor substrate 101 made of P-type silicon or the like.
And N-type impurity regions 104 and 105 are formed.
The gate electrode 103 and the N-type impurity regions 104 and 105
Form the transistor 106. N-type impurity region 105 serving as a drain of transistor 106 has A
A power supply wiring 107 made of a metal containing l (aluminum) as a main material is electrically connected. The semiconductor substrate 101 has a P-type impurity region 108 for transmitting the substrate potential.
Is formed, and an interlayer insulating film 1 made of an oxide film or a nitride film or the like is formed.
09 and 110 are formed.

As described above, the semiconductor substrate 101, the field oxide film 102, the gate electrode 103, the N-type impurity region 1
04, 105, power supply wiring 107, P-type impurity region 10
8 and the interlayer insulating films 109 and 110 form a pixel base circuit 111. On the base circuit 111, a microbridge 112 made of an insulating film such as an oxide film or a nitride film and formed by using a micromachine technique is formed. Ti on the microbridge 112
A heating resistor 113 made of N (titanium nitride) or the like is formed. The heating resistor 113 is connected to the metal wirings 114 and 115 mainly made of Al to form the transistor 10.
6 is electrically connected between the N-type impurity region 104 and the P-type impurity region
6 controls the current flowing through the heating resistor 113.

[0007] The micro bridge 1 is also provided so that the temperature of the heating resistor 113 is effectively increased by the heat generated by the heating resistor 113.
Numeral 12 has a hollow structure and is thermally separated from the underlying circuit 111. The microbridge 112 is connected to the underlying circuit 11.
1 to increase the aperture ratio, which is the ratio of the pedestal area of the microbridge 112 to the pixel area,
The amount of emitted infrared light is increased. Although other elements are formed in the pixel, they are omitted in FIG.

[0008]

On the other hand, the intensity of the infrared ray emitted from the infrared image generating element 100 is equal to that of the heating resistor 11.
In order to increase the dynamic range by increasing the intensity of radiated infrared rays, there is a demand to make the heating resistor 113 as high as possible. However, most of the wiring materials used in a normal IC process have a lowered resistance value due to a change in crystallinity due to high-temperature annealing.

When these wiring materials are used for the heating resistor 113, the resistance value decreases when the temperature becomes higher than a certain critical temperature (hereinafter referred to as a pixel heat-resistant temperature). A thermal runaway occurs due to a series of processes such as an increase in the calorific value. For this reason,
There is a problem in that pixel generation such as deformation of the microbridge 112 and disconnection of the heating resistor 113 is caused by generation of stress due to a volume change accompanying a change in crystallinity of the heating resistor 113.

In order to prevent this pixel destruction, the heating resistor 11 when using the infrared image generating element 100 is used.
3 at a temperature higher than the maximum temperature of
It is conceivable to perform a high-temperature heat treatment in advance during the manufacturing process to increase the heat-resistant temperature above the maximum temperature in actual use. In this case, although the resistivity of the heating resistor 113 is reduced by the high-temperature heat treatment, a desired resistance value can be obtained by designing the wiring pattern of the heating resistor 113 in anticipation of the decrease. When the heating resistor 113 is operated at a temperature equal to or lower than the heat treatment temperature, the resistivity does not decrease and the pixel does not break due to thermal runaway.

However, the conventional infrared image generating element 100
Then, as shown in FIG.
Is used as a main material, and since this Al wiring has a low melting point, about 500 ° C.
It is impossible to perform the high-temperature heat treatment described above, so that the heat treatment temperature after the heat generating resistor 113 is formed is limited to a low temperature. In addition, in order to avoid this restriction, the method of forming the heating resistor 113 first and performing the high-temperature heat treatment and then forming the Al wiring cannot form the heating resistor 113 above the underlying circuit 111. As a result, there is a problem that the aperture ratio is greatly reduced and the dynamic range is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to increase the heat resistant temperature of a pixel without lowering the aperture ratio and obtain an infrared image generating element having a large dynamic range. And

[0013]

An infrared image generating element according to the present invention comprises a microbridge having a hollow structure formed on a semiconductor substrate, a heating resistor formed on the microbridge, and a semiconductor substrate. And a control circuit for controlling heat generation of the heating resistor. A plurality of pixels are arranged in an array, and a pixel region is arranged in an array. In an infrared image generating element for generating an image, at least a part of a wiring used in each pixel is formed of a metal wiring mainly composed of a high melting point metal.

In the infrared image generating element according to the present invention, at least a part of the wiring used in the pixel region is formed of a metal wiring mainly composed of a high melting point metal. At least a part of the wiring used outside the region is formed of a metal wiring mainly made of aluminum.

Further, in the infrared image generating element according to the present invention, in any one of the first and second aspects, the heating resistor is formed of a high melting point metal silicide.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail based on an embodiment shown in the drawings. Embodiment 1 FIG. FIG. 1 is a schematic diagram showing a circuit configuration example of the infrared image generating element according to Embodiment 1 of the present invention. In FIG. 1, the infrared image generating element 1 includes a vertical scanning circuit 2, a horizontal scanning circuit 3, a horizontal selection circuit 4, and a pixel area 6 in which a plurality of pixels 5 are arranged in an array.

Each pixel 5 includes a heating resistor 11, a MOS transistor (hereinafter referred to as an energization control transistor) 12 for controlling a current flowing through the heating resistor 11, and a vertical selection MOS transistor (hereinafter referred to as a vertical selection transistor). 13) and a hold capacitor 14 provided to hold the gate voltage of the conduction control transistor 12 when the vertical selection transistor 13 is OFF.

The drain of each conduction control transistor 12 is connected to a power supply line 15 for supplying a bias to the heating resistor 11, and the power supply line 15 is connected to a power supply input terminal 16 for a bias power supply. The gate of each vertical selection transistor 13 is connected to the corresponding vertical selection line 1
7 are connected to the vertical scanning circuit 2 respectively.
The drain of each vertical selection transistor 13 is connected to the corresponding M of the horizontal selection circuit 4 through the corresponding signal line 18.
The transistors are connected to the sources of OS transistors (hereinafter, referred to as horizontal selection transistors) 20, respectively. The gate of each horizontal selection transistor 20 is connected to the horizontal scanning circuit 3, and the drain of each horizontal selection transistor 20 is connected to a signal input terminal 21 to which a control signal is input from the outside.

An operation example of the infrared image generating element 1 having such a configuration will be described. In addition, in order to make the description easy to understand, one pixel in each pixel 5 will be described as an example, but the same applies to the other pixels 5 and the description is omitted. First, when one column of the vertical selection transistors 13 is selected and turned on by the vertical scanning circuit 2, and then one horizontal selection transistor 20 is turned on by the horizontal scanning circuit 3, it is at the intersection of the two selection lines. A signal voltage is input from the signal input terminal 21 to the gate of the conduction control transistor 12 of the selected pixel.

At this time, the current flowing through the conduction control transistor 12 changes according to the signal voltage, and the amount of heat generated by the heating resistor 11 connected thereto changes. Next, when the pixel once selected by the scanning circuit operation is deselected, the vertical selection transistor 13 is turned off, and the gate of the conduction control transistor 12 is electrically floating. Since a large hold capacitor 14 is connected to this gate, the conduction control transistor 12
Hold the signal voltage at the time of selection as it is.

Thus, even when the pixel is not selected, the current flowing through the conduction control transistor 12 does not change, and the heating resistor 11 is not changed until the scanning of all the pixels is completed and the next pixel is selected.
Is constant. Pixel selection is sequentially performed by the vertical scanning circuit 2 and the horizontal scanning circuit 3, and by changing the signal voltage input from the signal input terminal 21 in synchronization with the selection, the infrared image generating element 1 generates a desired infrared image. generate.

FIG. 2 is a pixel sectional view showing an example of the structure of one pixel in the infrared image generating element 1 shown in FIG. In FIG. 2, an infrared image generating element 1 has a field oxide film 32 for isolation and a gate electrode 3 made of polysilicon or the like on a semiconductor substrate 31 made of P-type silicon or the like.
3 and N-type impurity regions 34 and 35 are formed. The conduction control transistor 12 is formed by the gate electrode 33 and the N-type impurity regions 34 and 35. An N-type impurity region 35 serving as a drain of the conduction control transistor 12 includes:
A power supply wiring 37 made of a material mainly composed of a high melting point metal such as W (tungsten) and Ti (titanium) is electrically connected. In the semiconductor substrate 31, a P-type impurity region 38 transmitting a substrate potential is formed, and interlayer insulating films 39 and 40 made of an oxide film or a nitride film are formed.

As described above, the semiconductor substrate 31, the field oxide film 32, the gate electrode 33, the N-type impurity regions 34, 3
5, a power supply wiring 37, a P-type impurity region 38, and interlayer insulating films 39 and 40 form a pixel base circuit 41. On the base circuit 41, a microbridge 42 made of an insulating film such as an oxide film or a nitride film and formed by using a micromachine technique is formed. The heating resistor 11 made of TiN (titanium nitride) or the like is formed on the microbridge 42. The heating resistor 11 is
Metal wires 44 and 45 formed of a material mainly composed of a high melting point metal such as W or Ti provide electrical connection between the N-type impurity region 34 and the P-type impurity region 38 serving as the source of the conduction control transistor 12. And the conduction control transistor 12 controls the current flowing through the heating resistor 11.

Further, the micro bridge 42 is provided so that the temperature of the heating resistor 11 is effectively increased by the heat generated by the heating resistor 11.
Is thermally separated from the underlying circuit 41 as a hollow structure. Further, by forming the microbridge 42 above the base circuit 41, the aperture ratio, which is the ratio of the pedestal area of the microbridge 42 to the pixel area, is increased, and the amount of emitted infrared light is increased. The temperature of the heating resistor 11 is
Since it is uniquely determined by the balance between Joule heat generated by energization and heat conduction from the support legs of the microbridge 42 to the semiconductor substrate 31 and radiation by radiation, heat is generated by the signal voltage input to the gate of the energization control transistor 12. The temperature of the resistor 11 can be arbitrarily controlled. Note that the vertical selection transistor 1 is provided in the pixel.
3, other elements such as the hold capacitor 14 are also formed, and a high melting point metal is used for the metal wiring in the pixel, but these are omitted in FIG.

On the other hand, in FIGS. 1 and 2, the metal wiring used in the pixel 5 is made of a metal having a high melting point as a main material, but the metal wiring used in the pixel region 6 is used as the metal wiring. A wiring may be used, and an Al wiring may be used as a metal wiring used outside the pixel region portion 6. FIG. 3 is a schematic diagram showing an example of a circuit configuration of such an infrared image generating element. In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted and only the differences from FIG. 1 will be described.

The difference between FIG. 3 and FIG. 1 is that high melting point metal wiring is used for the metal wiring used in the pixel region portion 6.
This is because Al wiring is used as the metal wiring outside the pixel region 6. For this reason, the pixel region 6 in FIG. 1 is defined as the pixel region 6a, and the infrared image generating device 1 in FIG. 1 is defined as the infrared image generating device 1a. In FIG. 3, the pixel region 6a
Each of the power supply lines 15a is electrically connected to each of the connection portions A15 corresponding to the power supply lines 15b outside the pixel region 6a. In addition, each vertical selection line 1 in the pixel region 6a
7a is a corresponding vertical selection line 17b outside the pixel area 6a.
Are electrically connected to each other at connection portions A17. Further, each signal line 18a in the pixel region 6a is electrically connected to a corresponding signal line 18b outside the pixel region 6a at each connection portion A18.

The drain of each energization control transistor 12 is connected to the power supply line 1a through the power supply line 15a and the connection portion A15.
5b, and the power supply wiring 15b is connected to the power supply input terminal 16. Each vertical selection transistor 1
3 are connected to the corresponding vertical selection line 17a and the connection A
Each of the vertical scanning lines 17b is connected to a corresponding one of the vertical selection lines 17b via the corresponding one of the vertical scanning circuits 2. The drain of each vertical selection transistor 13 is connected to the corresponding signal line 18b via the corresponding signal line 18a and the connection portion A18, and the signal line 18b is connected to the corresponding horizontal selection transistor 20 of the horizontal selection circuit 4. Each is connected to a source.

Here, the metal wiring in the pixel area 6a, that is, the metal wiring in each pixel 5, each power supply wiring 15a, each vertical selection line 17a, and each signal line 18a are each formed of a high melting point metal wiring. ing. Also, the power supply wiring 15b,
All metal wirings outside the pixel area 6a including the vertical selection lines 17b and the signal lines 18b are formed of Al wirings. The wiring is formed by refractory metal wiring, heating resistor,
Al wires are formed in this order, and a high-temperature heat treatment is performed after the heating resistor is formed and before the Al wires are formed.

By doing so, the heat-resistant temperature of the pixel is improved, and the maximum temperature of the pixel in actual use can be set higher. Further, if the peripheral circuit of the pixel region 6a is formed only of the high melting point metal wiring, various problems occur, such as the high melting point metal wiring having a higher wiring resistance than the Al wiring and making it difficult to form a multilayer wiring. Since Al wiring is used for the peripheral circuit, wiring defects when forming the peripheral circuit are reduced.

As described above, in the infrared image generating element according to the first embodiment, since the wiring in each pixel or the pixel area is formed by using the high melting point metal, the heat generation resistance is reduced in the manufacturing process of the infrared image generating element. After the body 11 is formed, a high-temperature heat treatment of 500 ° C. or more can be performed. For this reason, the heat-resistant temperature of the pixel can be improved by performing the high-temperature heat treatment, and the maximum temperature of each pixel in actual use can be set high.

Embodiment 2 In the first embodiment, TiN is used for the heat generating resistor 11, but a high melting point metal silicide having a higher heat resistance temperature than TiN may be used, and such a structure is referred to as a second embodiment of the present invention. FIG. 4 is a pixel cross-sectional view illustrating a structural example of one pixel in the infrared image generating element according to Embodiment 2 of the present invention. In FIG. 4, the same components as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted and only the differences from FIG. 2 will be described. The schematic diagram showing an example of the circuit configuration of the infrared image generating element according to the second embodiment of the present invention is the same as FIG. 1 except that the signs of the infrared image generating element 1 and the heating resistor 11 in FIG. 1 are changed. Omitted.

The difference between FIG. 4 and FIG. 2 is that the heating resistor 11 of FIG. 2 is changed to a heating resistor 51 because the material of the heating resistor 11 of FIG. 2 is changed. 2 in that the infrared image generating element 1 of FIG. In FIG. 4, in the infrared image generating element 55, a heating resistor 51 made of a high melting point metal silicide is formed on a microbridge. The heating resistor 51 is connected to the N-type impurity region 3 serving as the source of the conduction control transistor 12 by the metal wires 44 and 45.
The conduction control transistor 12 is electrically connected between the P-type impurity region 4 and the P-type impurity region 38, and controls a current flowing through the heating resistor 51.

Since the refractory metal silicide used for the heating resistor 51 has a higher heat-resistant temperature of the material itself than TiN, it is advantageous in increasing the maximum temperature of the pixel in actual use. On the other hand, conventionally, high melting point metal silicide has been used as a gate wiring material in an IC process.
In some production lines, in order to prevent metal contamination of the production equipment, the use is often limited only to the step before the formation of Al (aluminum) wiring. However, in the infrared image generating element 55, the metal wirings 37, 44, 4
Since the high-melting-point metal wiring is used for 5 instead of the Al wiring, the high-melting-point metal silicide can be used for the heating resistor 51 without any restriction on the operation of the production line.

As described above, the infrared image generating element according to the second embodiment is formed by using the refractory metal silicide for the heating resistor 51. From this, the refractory metal silicide has a higher resistivity than TiN, and when obtaining a desired resistance value, the wiring length of the entire heating resistor 51 can be shortened, and the pixel size can be reduced. In addition, the smaller the pixel size, the smaller the amount of input power required to cause the heating resistor 51 to generate heat to a certain temperature, the smaller the power consumption. Therefore, the power consumption can be significantly reduced without lowering the maximum temperature of the pixel.

[0035]

The infrared image generating element according to claim 1 is
At least a part of the wiring used in each pixel was formed of a metal wiring mainly composed of a high melting point metal. From this, the maximum temperature of the pixel in actual use can be set higher,
The dynamic range can be increased.

According to a second aspect of the present invention, in the infrared image generating device according to the first aspect, at least a part of the wiring used in the pixel region is formed of a metal wiring mainly composed of a high melting point metal. At least a part of the wiring used outside was formed of a metal wiring mainly composed of aluminum.
Accordingly, it is possible to reduce wiring defects when forming a peripheral circuit outside the pixel region portion, and it is possible to improve the manufacturing yield of elements.

According to a third aspect of the present invention, in the infrared image generating element according to the first or second aspect, the heat generating resistor is formed of a high melting point metal silicide. From this,
Since the maximum temperature of the pixel during actual use can be set high and the pixel size can be reduced, the dynamic range can be increased and the power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a circuit configuration example of an infrared image generating element according to Embodiment 1 of the present invention.

FIG. 2 is a pixel cross-sectional view showing a structural example of one pixel in the infrared image generating element 1 shown in FIG.

FIG. 3 is a schematic diagram showing another circuit configuration example of the infrared image generating element according to the first embodiment of the present invention.

FIG. 4 is a pixel sectional view showing a structural example of one pixel in an infrared image generating element according to a second embodiment of the present invention.

FIG. 5 is a pixel sectional view showing a structure of one pixel in a conventional infrared image generating element.

[Explanation of symbols]

1, 1a, 55 infrared image generating element, 2 vertical scanning circuit, 3 horizontal scanning circuit, 4 horizontal selection circuit, 5
Pixel, 6, 6a Pixel region, 11, 51 Heating resistor, 15, 15a, 15b, 37 Power supply wiring,
17, 17a, 17b vertical selection lines, 18, 18a,
18b signal line, 41 ground circuit, 42 micro bridge, 44, 45 metal wiring.

 ────────────────────────────────────────────────── ─── Continued on front page F term (reference) 2G065 AB02 BA06 BA14 BA34 BB49 BC10 CA21 DA20 4M118 AA02 AA04 AA09 AB01 BA06 BA14 CA35 CB14 GA10 5C024 AA06 CA14 5C061 BB02 CC01

Claims (3)

[Claims] 1. A micro-bridge having a hollow structure formed on a semiconductor substrate, a heating resistor formed on the micro-bridge, and a control circuit formed on the semiconductor substrate and controlling heat generation of the heating resistor. An infrared image generating element that includes a pixel region portion in which a plurality of pixels configured by an array is arranged, and selectively generates heat by generating heat from the heat generating resistor of each pixel; Wherein at least a part of the wiring used in (1) is formed of a metal wiring mainly composed of a high melting point metal. 2. A method according to claim 1, wherein at least a part of the wiring used in the pixel region is formed of a metal wiring having a high melting point metal as a main material, and at least a part of the wiring used outside the pixel region is The infrared image generating element according to claim 1, wherein the infrared image generating element is formed of a metal wiring mainly composed of aluminum. 3. The heating resistor according to claim 1, wherein the heating resistor is formed of a refractory metal silicide.
The infrared image generating device according to any one of the above.