JPH0217988B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an infrared two-dimensional sensor, and more particularly to an infrared solid-state imaging device that is entirely made of solid material and is used to obtain an infrared video signal.

Conventional sensors for detecting infrared rays include those using semiconductors that utilize quantum effects and those using pyroelectric crystals that convert infrared rays into heat, and various types of two-dimensional sensors have been considered. Classified by scanning method, these are optical scanning, electron beam scanning, and self-scanning, each of which has its advantages and disadvantages, but there is still no infrared two-dimensional sensor that can be used in a wide range of applications and satisfies the characteristics and price. Not put into practical use. That is, in the optical scanning method, a single infrared sensor mainly made of InSb or HgCdTe is used to perform two-dimensional scanning using a rotating or vibrating optical system. This method has disadvantages such as large size, high power consumption, and short lifespan due to mechanical failure.The performance of the optical sensor section as an infrared camera is also at its limit, and no improvement measures have been considered. do not have. In addition, in the electron beam method, the signal is focused on a matrix detector mainly made of pyroelectric crystal, and the signal is extracted using an electron beam, but this detector generally has low sensitivity and has a small number of pixels. Since not so many are formed, the resolution is poor, and since an electron beam is required, there are drawbacks such as the large size of the device, similar to the former case. The next self-scanning method is considered to be the newest method, and is a CCD (Charge-Coupled Device).
It consists of a semiconductor element that has a self-scanning function for signals, such as a charge-coupled device, and a sensor section.
Compared to the previous two methods, this method has advantages such as high performance, high reliability, and low cost, and is considered promising, but nothing satisfactory has yet been achieved in the infrared region.

In other words, in the visible light range, ordinary semiconductor silicon (Si) absorbs light at an appropriate depth depending on the wavelength, so if a PN junction (photodiode) is formed at an appropriate thickness of Si, light can be detected as an electric current. By forming a drive unit such as a CCD on the same Si substrate, a self-scanning solid-state imaging device can be constructed. However, when infrared rays have long wavelengths, they pass through the Si semiconductor and cannot be detected. Therefore, in order to detect these long wavelengths using this method, impurities such as In or Ga are doped into the Si semiconductor to create a band gap. Either make it narrower or use InSb instead of using Si semiconductor.
A narrow bandgap semiconductor such as HgCdTe must be used. However, semiconductors with narrow band gaps inherently have increased thermal noise and a significant relative decrease in sensitivity. Therefore, in order to reduce this thermal noise, this sensor part must be cooled (50°K).
Monolithic solid-state imaging devices in the infrared region have not been put to practical use because the cooling equipment is difficult and the CCD part, which is the driving part, is also cooled and causes abnormal operation, making it impractical. .

On the other hand, a hybrid type configuration is being considered as a system similar to this conventionally considered system in the infrared region. In other words, the hybrid type is InSb,
It is composed of a semiconductor type sensor such as HgCdTe or PbSnTe or a sensor using a pyroelectric crystal and a Si-CCD drive unit.For example, it is formed with the configuration shown in the perspective view in Figure 1, and 1 is an infrared sensor. array,
2 is the input gate, 3 is the Si-CCD part which is the drive part, the semiconductor type sensor can be cooled separately, and the Si-CCD part is the input gate.
The CCD drive unit can be kept at room temperature and driven. Although pyroelectric crystals do not require cooling, it is difficult to form them with a small heat capacity, resulting in a decrease in sensitivity.In addition, this hybrid type requires a large number of elements for both semiconductor and pyroelectric crystal types. As a result, the wiring between the sensor section and the Si-CCD section becomes difficult, which limits the number of elements, making it impossible to obtain high resolution, which is a serious drawback.

The present invention was made in view of these drawbacks.
The object of the present invention is to provide a monolithic infrared solid-state imaging device that has good sensitivity, high resolution, and does not require cooling. Specifically, a pyroelectric crystal and an electrode material are deposited in a thin film on an insulating film on a semiconductor substrate to form a sensor part for detecting radiation waves, and the semiconductor substrate under the insulating film located below the sensor part is A portion of the semiconductor substrate is removed by corrosion to form a corrosion hole to reduce the heat capacity of the sensor portion to improve sensitivity, and a MOS structure and a drive portion such as a CCD are formed on other portions of the semiconductor substrate. be.

A feature of the present invention is that a highly sensitive sensor section that does not require cooling is formed using a pyroelectric crystal on the same semiconductor substrate on which the driving section, such as a CCD, is formed. Other than CCD
BBD (Bucket-Brigade Device), CID (Charge Injection Device)
Other systems such as the above may also be used, and since these configurations are conventionally known techniques, the sensor section will mainly be described in detail below with reference to the drawings.

FIG. 2 is a plan view of an infrared solid-state imaging device according to an embodiment of the present invention, FIG. 3 is a sectional view taken along line AA', and FIG. 4 is a sectional view taken along line BB' in FIG.
In Figures 2 to 4, the main surface of 4 and 6 is (100)
an n-type silicon crystal layer having a plane or a (110) plane; 5 is a P ⁺ type impurity layer formed in advance; 7;
8 is a high-temperature oxide film or an insulating film such as a silicon oxide film or a silicon nitride film formed by a CVD method; 9 is an n ⁺ diffusion layer for making ohmic contact with the electrode 13;
10 is an n ⁺ type diffusion layer for channel stopper;
11 and 13 are electrodes of the pyroelectric crystal 12, and 14 is a gate electrode, which is connected to the insulating film 8 and the n-type silicon crystal layer 6.
It has a MOS structure and transfers the charge generated in the pyroelectric crystal in accordance with the pulses of the CCD, which is the driving unit, to prevent pixel signals from being mixed with other pixel signals. 15, 17, 18 are drive parts
16 is a corrosion hole provided in the n-type silicon crystal 6 below the pyroelectric crystal 12; 19 is a P-type diffusion layer for extracting output power; 20 is the electrode; 21 is the corrosion hole 16 This is a perforation provided in the insulating film 8 to obtain the following.

Next, the manufacturing procedure for this embodiment of the infrared solid-state imaging device will be described below. First, a P ⁺ type impurity layer 5 is formed in advance in the shape of a sandwich arch.
One semiconductor substrate consisting of type Si crystals 4 and 6 is prepared, an insulating film is formed on both sides of the substrate, the upper insulating film (high temperature oxide film) is cut out by photolithography, and n-type diffusion layers 9 and 10 are formed. and a P-type diffusion layer 19 is formed. After that, all of the cut-out insulation film (high temperature oxide film) is peeled off and a new high temperature oxide film method or
An insulating film 8 such as a silicon oxide film or a silicon nitride film is formed by a CVD method or the like. Thereafter, holes for bringing the electrodes 13 and 20 into ohmic contact again and holes 21 for providing the corrosion holes 16 in the lower part of the pyroelectric crystal 12 are punched out in the insulating film 8 by photolithography. Next, electrodes 11, 14, 15,
17 and 18 are formed. Furthermore, a pyroelectric crystal 12 is formed on a portion of the electrode 11 by sputtering or the like.
Furthermore, an upper electrode 13 and
Ohmic contact electrodes 13 and 20 are formed on the n ⁺ diffusion layer 9 and the P type diffusion layer 19. Next, through the holes 21 cut in the insulating film 8, an alkaline anisotropic chemical etchant mainly consisting of caustic soda or caustic potash, an anisotropic chemical etchant consisting of ethylenediamine and pyrocatechol, or an anisotropic chemical etchant consisting of hydrazine and water is applied. When chemical etching is performed using an anisotropic chemical etchant for silicon, such as an anisotropic chemical etchant,
Regions along the crystal axes are etched faster than regions along other crystal axes, so that the major surface is (100)
In a plane Si crystal, α is as shown in Figure 3.
A corrosion hole 16 can be formed in the shape of 54°44' and stopped by the P ⁺ type impurity layer 5, and the lower insulating film 8 can be left in the shape of a bridge on the pyroelectric crystal. It is possible to obtain a compact infrared solid-state imaging device that has a small heat capacity, is strong, and is connected to a driving section. In this embodiment, the P ⁺ impurity layer 5 is provided in the middle of the semiconductor substrate, and the pyroelectric crystal 12 of the semiconductor substrate is corroded from the side to which it is attached, and the corrosion is stopped at the impurity layer ⁵ .
If the Si crystal 6 is thick enough, corrosion will proceed at an angle of 54°44' and stop when the interfaces meet, forming a pyramid-shaped corrosion hole. Even if it is thin, the Si crystal in the lower part of the pyroelectric crystal 12 can be etched away by etching it from the back side of the semiconductor substrate. This corrosion method is detailed in Japanese Patent Application No. 55-102893.

FIG. 5 shows a cross-sectional view similar to FIG. 3 of another embodiment of the present invention, and in this embodiment, the method of forming the pyroelectric crystal electrodes was changed after the thin film of the pyroelectric crystal 12 was attached. The structure is such that electrodes 11 and 13 are taken out from both sides of the pyroelectric crystal.

In the embodiment of the present invention described above, the characteristics of PbTiO ₃ as the pyroelectric crystal, number of pixels 100 x 100, and size of the pyroelectric element pixel 20 μm x 20 μm are as follows: Temperature measurement range: 0 to 2000°C Temperature resolution: 0.05°C Sensitivity: 100V /W Noise RMS 10μV Obtains saturated output 2mV. Therefore, the present invention has much better resolution and sensitivity than conventional hybrid two-dimensional infrared sensors, has a very simple production process, can be done at a very low cost, and is very easy to use as it does not require cooling. It has the advantage of being simple.

The present invention provides a two-dimensional infrared solid-state imaging device that is easy to use, low-cost, and has good resolution and sensitivity.
It can be applied to various industrial measurements such as geological surveys, meteorological observation, military, pollution prevention, crime prevention, and disaster prevention, and has the effect of having a very wide range of uses.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a conventionally considered hybrid type infrared solid-state imaging device, FIG. 2 is a plan view of a monolithic type infrared solid-state imaging device that is an embodiment of the present invention, and FIG. A- in Figure 2
4 is a sectional view taken along the line BB' in FIG. 2, and FIG. 5 is a sectional view similar to FIG. 3 showing another embodiment of the present invention. 4, 6...n-type or p-type silicon crystal, 5...
P ⁺ type impurity layer, 8... Insulating film, 11, 13... Electrode, 12... Pyroelectric crystal, 14... Gate electrode, 15,
17, 18... Electrodes constituting the drive unit, 16... Corrosion holes, 21... Corrosion holes.

Claims (1)

[Claims] 1 An insulating film formed on a single semiconductor substrate having a (100) or (110) plane as its main surface, and an electrode metal, a pyroelectric crystal, and an electrode metal each laminated in a thin film form on the insulating film. a sensor section for detecting radiation waves formed by etching away at least a portion of the semiconductor substrate below the pyroelectric crystal that is in contact with the insulating film; An infrared solid-state imaging device, characterized in that a gate electrode for transferring detected charge from a sensor section and a driving section formed of a group of electrodes for inputting transfer pulses are integrally formed on the semiconductor substrate.