JPS63308970A - Hybrid type infrared detector - Google Patents

Abstract

PURPOSE:To maintain high reliability even when the number of picture elements is increased by using a second semiconductor substrate having a thermal expansion coefficient equal to or approximately equal to that of a first semiconductor substrate. CONSTITUTION:When infrared rays are projected as shown in the arrow, infrared rays having 3-5mum bands are photoelectric-converted in an N-type diffusion region 10 formed to an InSb substrate, and infrared rays having 8-14mum bands are transmitted through the substrate 5 as they are, and photoelectric-converted in an N-type diffusion region 2 shaped to an HgCdTe substrate 1. Signal charges photoelectric- converted by a CCD (a charge coupled device) electrode 9 are transferred by properly turning a first transfer gate 8 and a second transfer gate 11 ON at every one side, thus acquiring an infrared picture by both wave bands of 3-5mum bands and 8-14mum bands from a single hybrid type infrared solid-state image sensing device. Since the difference of the thermal expansion coefficients of the substrate 1 and the substrate 5 is brought to zero or approximately zero, no strain is generated even then the title device receives heat history between room temperature and the temperature of liquid nitrogen, thus maintaining reliability even when density and the number of picture elements are increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a zero-dimensional, -dimensional, or two-dimensional hybrid infrared detection device that detects infrared rays. In particular, the present invention relates to a detection device useful for infrared solid-state imaging devices.

[Conventional technology]

Among infrared rays with a wavelength of 0.8 μm or more, semiconductor substrates that are sensitive to the so-called "atmospheric window" region of 3 to 5 μm and 8 to 14 μm include InSb, InAsSb,
t(gcdTc, Pb5nTe, etc. are widely known.

The infrared detection device using the above-mentioned semiconductor substrate has a high detection sensitivity, and an operating temperature of 77, which can be easily achieved by using liquid nitrogen or the like, is sufficient, so it is highly regarded, and today - A prototype of a dimensional or two-dimensional infrared solid-state imaging device (hereinafter referred to as IRcTD) has been produced.

For example, InSb, which is sensitive to infrared rays in the 3-5 μm band,
Development of IRCTDs that utilize this technology has focused on monolithic IRCTDs, which have a light receiving section that performs photoelectric conversion and a charge transfer section that reads out the signal charges generated in the light receiving section, both of which are installed on the same semiconductor substrate. A 1nsb monolithic IRCTD having a pixel count of 1oooo or more has already been realized. On the other hand, 8 to 1
In an IRCTD using HgCdTe that is sensitive to infrared rays of 4 μm, a light receiving section that performs photoelectric conversion and a charge transfer section for reading signal charges generated in the light receiving section are made of different semiconductor 2S. Development is mainly focused on hybrid IRCTDs, which are installed in +l1iE and further connect amphibic conductor substrates to each other, but a high-density H g CdTe hybrid IRCTD has not yet been realized, and The number of pixels is about 4000 at most.

In order to obtain higher quality infrared images using the monolithic I RCTD or hybrid I RCTD described above, it is important to first increase the number of pixels in order to improve the spatial resolution. others,
A single IRc to enhance the ability to identify target objects.
It is desirable that the TDs be able to detect infrared rays in different wavelength bands.

Here, IR using HgCdTe, which is known as a semiconductor material sensitive to infrared rays in the 8 to 14 μm band, is used.
cTD will be explained in more detail.

First, i(g Cd T e monoline, ri-type IRcTD
In this case, both the light receiving part and the charge transfer part are l-1g Cd, T
This means that the Hg
This means that it is necessary to fabricate a signal readout device such as a charge transfer device (hereinafter referred to as CCD) on the c d're substrate. However, ``insulating film formation technology that exhibits good interface characteristics'', which is an essential technological element for manufacturing high-performance CCDs, has not yet been established, and therefore increasing the number of pixels is extremely difficult to achieve. It's a situation. Furthermore, t(g C
Since the bandgap of dTe is very small, about 0.1eV, the amount of charge that can be accumulated in the CCD potential well is very small.
It is difficult in principle to form a CCD on a substrate.
I have problems like this.

Therefore, Hg as an infrared detection substrate in the 8-14μI band
A light receiving section for photoelectric conversion is formed on a CdTe substrate, and a Si substrate CCD is used as a charge transfer device to read out signal charges generated in the light receiving section.
e. A "hybrid type IRC" in which the ZS board and the Si substrate on which the COD is formed are stacked and bonded vertically, and the light receiving part and the processing circuit (CCD) are electrically connected and integrated.
TI) J was proposed.

[Problem that the invention seeks to solve]

However, since the hybrid IRcTD uses an S1-CCD as a charge transfer device, it is possible to easily realize a high-performance signal readout device, but on the other hand, the connection between the HgCdTc7S+ffl and the Sl substrate is If you have low confidence in the
Due to the difference in thermal expansion coefficient between Te-based IRcTD and Si-based IRcTD, the above-mentioned hybrid IRcTD
When subjected to thermal history between room temperature and liquid nitrogen temperature, problems such as cracking or peeling of the joints occurred.

The above-mentioned problems (phenomena) will be explained in detail below using the drawings. FIG. 2(A) is a partial cross-sectional view of an example of a conventional Hg CdTe hybrid type IRc'FD, and for the sake of simplicity, only the peripheral parts of pixels at both left and right ends of the hybrid type I RCTD are shown.

In Figure 2 (A), P-type HgCd1'e, lfM2
1 includes an n-type diffusion region 22 which is a light receiving part, and a metal pad 23 for extracting signal charges generated in the light receiving part to the outside.
, an insulating film 24 are formed respectively. On the other hand, the P-type Si% plate 25 includes a metal pad 26 and an input diode 27 for receiving and receiving signal charges, and 2 cc of signal charges received.

A transfer gate 28 and a CCD electrode 29 for charge transfer are formed, respectively. and,
11 P-type Hg Cd '■'e4+anti-21 and P-type Si
By connecting the substrate 25 with a metal hump '30, the hybrid IRCT shown in FIG.
D is obtained. Note that the above-mentioned connection work is normally performed at room temperature.

On the other hand, when actually operating an IRCTD, it is essential to cool the device using liquid nitrogen, etc.
The temperature of TD is about 77, but here, as shown in Fig. 2 (B
) to create the hybrid IR shown in Figure 2(A).
The state when the CTD is cooled is illustrated. By cooling,
Both the HgCdTe substrate 21 and the Si substrate 25 shrink, but since the coefficient of thermal expansion of the HgCdTe substrate 21 is much larger than that of Si, the amount of shrinkage of the HgCdTe substrate 21 is much smaller than that of the Si substrate 25. big.

Therefore, strain concentrates particularly on the metal bump portion of the hybrid IRCTD, and for example, the metal bump is deformed as shown in 30a. Furthermore, if you stop using the detection device, return it to room temperature, cool it again, and use it repeatedly, the metal pipe will eventually crack as shown in 30b or peel off as shown in 30c. cause a phenomenon. The above-mentioned phenomenon essentially means a pixel defect, resulting in the inconvenience that the image obtained by the hybrid IRcTD is significantly degraded.

Next, when using the hybrid IRCTD described above and increasing the number of pixels in order to obtain an infrared image of higher quality, the distortion that a single pixel of the hybrid IRCTD receives will be considered.

For example, if a is the ratio of the amount of distortion to the pixel size in pixels at both ends of a hybrid IRcTD with m pixels, then a=□・1α−βj・ΔT−m・・・(1) given. However, 1α-β1 is a hybrid IR
The difference in thermal expansion coefficient ΔT between the first and second semiconductor substrates constituting the CTD is the temperature difference that the hybrid IRCTD is subjected to. Therefore, as is clear from equation (1) above, in the conventional hybrid IRCTD, the pixels are made finer to obtain high-quality infrared images, and the higher the number of pixels (m), the greater the amount of distortion with respect to the pixel size. The ratio a increases, and as a result, the defect occurrence rate at the connection part of the hybrid IRCTD increases. Therefore, it is extremely difficult to realize a highly reliable hybrid IRCTD with an increased number of pixels. Ta.

The present invention has been made to solve the above-mentioned problems. In other words, in order to obtain higher quality infrared images, high reliability can be maintained even when the number of pixels is increased, and furthermore, high reliability can be maintained even when the number of pixels is increased. , a completely new hybrid type IRc that can detect infrared rays in different wavelength bands simultaneously in some cases.
The purpose is to provide TD.

[Means for solving problems]

The present invention provides a first semiconductor substrate provided with a light receiving section, for example, Hg
A hybrid infrared detection device using a second semiconductor substrate, such as InSb, having a coefficient of thermal expansion equal to or less than that of CdTe is provided.

[Effect]

According to the invention, the first semiconductor 43 +5. The difference in thermal expansion coefficient between the first semiconductor substrate and the second semiconductor substrate, that is, the value of 1α−β1 in the above-mentioned equation (1) is equal to 0 or approximately O.

Therefore, in the hybrid IRCTD according to the present invention,
Even if the number of pixels is increased, almost no distortion occurs, and therefore,
A hybrid IRcTD that can maintain sufficient reliability even when the number of pixels is increased can be realized.

The HgCdTe substrate useful as the first semiconductor substrate is 8 to 1
It has sensitivity to infrared rays in the 4μ-band. On the other hand, an InSb substrate useful as a second semiconductor substrate not only has sensitivity to infrared rays in the 3 to 51 tm band, but also allows for fabrication of a high-performance signal readout circuit on the InSb substrate. Therefore, depending on the case, a light receiving section for photoelectric conversion may be provided on both the acid HgCdTe-1nSb semiconductor substrates, and the signal charge generated in the light receiving section may be read out using a CCD etc. fabricated on a 1nSb75 board.
A hybrid IRCTD that can simultaneously detect infrared rays in two wavelength bands, 3 to 5 μm band and 8 to 14 μm band, can be realized.

[Example] Hereinafter, an example of the present invention will be explained using the drawings.
The figure is a partial cross-sectional view of one embodiment of a hybrid IRCTD according to the configuration of the present invention, in which the first semiconductor substrate is a P-type H
On the gCdTe substrate 1, an n-type diffusion region 2 serving as a first light receiving section, a metal pad 3 for extracting signal charges generated in the light receiving section to the outside, and an insulating film 4 are formed.

On the other hand, in the P-type 1nSb substrate 5 which is the second semiconductor substrate,
In addition to a metal pad 6 and a human-powered diode 7 for receiving and taking signal charges from the outside, a first transfer electrode 1-8 for sending the received signal charges to a CCD, and a CCD electrode 9 for transferring charges, An n-type diffusion region 10 serving as a second light receiving section and a second transfer gate 11 for transmitting signal charges generated in the light receiving section to the CCD are formed.

Then, the Hg Cd Te group + Fi, 1 and 1 ns
By connecting the bi temporary 5 with the metal bump 12,
A hybrid IRCTD is configured.

When infrared rays are incident on the hybrid IRCTD described above as shown by the arrows in FIG. Infrared rays in the 8-14μm band are InS
The b-substrate 5 passes through as it is, and the Hg Cd T e-substrate 1
Photoelectric conversion is performed in the n-type diffusion region 2 formed in the. Then, by appropriately turning on the first transfer gate 8 and the second transfer gate 11 one by one, the C
If the signal charge photoelectrically converted at the CD electrode 9 is transferred,
In the end, a single hybrid IRCTD according to this embodiment
Therefore, it is possible to obtain infrared images in both the 3-5 μm band and the 8-14 μm band.

In addition, in the hybrid IRcTI according to the present invention, H
Since the difference in thermal expansion coefficient between the gCdTe substrate l and the In5bi plate 5 is O or almost 0, the hybrid IRCT
No distortion occurs even if D undergoes thermal history between room temperature and liquid nitrogen temperature, and therefore, sufficient reliability can be maintained even when the density is increased and the number of pixels is increased.

In the above examples, for convenience of explanation, HgCdTe
Substrate 1 and 1nsI? Although the substrate 5 is connected to the substrate 5 using the metal bump 12, this connection method is not particularly limited.In addition, the signal readout device may also include a charge injection device (CiD), a charge imaging matrix, in addition to a CCD. (CIM) etc., it is clear that the effects of the present invention can be similarly applied and obtained.

(Effects of the Invention) As explained above, according to the present invention, high reliability can be ensured even when the number of pixels is increased.Furthermore, light receiving parts having infrared sensitivities in different wavelength bands are arranged in the first and second light receiving parts. If provided on two substrates, it becomes possible to provide an infrared detection device capable of detecting two wavelengths simultaneously with a simple configuration, and a great effect can be expected in application to thermal imaging cameras and in practical use.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of an embodiment of an infrared detection device according to the present invention, and FIG. 2(A) is a conventional hybrid type I
A partial cross-sectional view of an example of the RCTD (FIG. 2 CB) is a partial cross-sectional view of the hybrid IRCTD of FIG. 2(A) when it is cooled. [Explanation of symbols of main parts] 1.21-P-type Hg Cd Te 4 plate (first semiconductor substrate) 2.22...n-type diffusion region 3.23...metal pad 4.24- ...Insulating film 5... p-type 1 n S b? s+i (second semiconductor? S+anti) 25...P-type Si substrate 6.26...Metal bad door, 27...Input diode 8...First transfer electrode 28...Transfer electrode 9.29 ...CCD electrode 10...n-type diffusion region 11...second transfer electrode 12.30...metal bump 30a...deformed metal bump 30b...cracked metal hump 30C... ...Peeled metal bump g? 77 5 10 ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑廿口so(△) (B) Figure 2

Claims (3)

[Claims] (1) A first semiconductor substrate including an infrared light receiving section, and a second semiconductor substrate including a processing circuit that processes an electrical signal from the light receiving section.
In a hybrid infrared detection device formed by overlapping and bonding a semiconductor substrate and electrically connecting the light receiving section and a processing circuit, a second semiconductor substrate having the same or substantially the same coefficient of thermal expansion as the first semiconductor substrate; A device characterized by using a semiconductor substrate. (2) The hybrid infrared detection device according to claim 1, wherein the first semiconductor substrate is HgCdTe and the second semiconductor is InSb. (3) A second light receiving section having a wavelength sensitivity different from that of the light receiving section is provided on the second semiconductor substrate, and this is electrically connected to the processing circuit.
The hybrid infrared detection device described in .