JPH04192559A - Array-type infrared detector and its manufacture - Google Patents

Abstract

PURPOSE:To reduce a dark current by a method wherein through holes corresponding to output-signal processing parts in a silicon chip are made in individual photodiodes and the photodiodes are connected electrically to the output- signal processing parts in the chip via the through holes. CONSTITUTION:A compound semiconductor whose forbidden band width is narrow is epitaxially grown linearly on the mirror-finished rear of a silicon chip 3 provided with output-signal processing parts 4; individual photodiodes 6 arranged and formed on the compound semiconductor and the output-signal processing parts 4 in the silicon chip 3 are connected electrically via through holes 7. Consequently, the reliability of electrical interconnections during an operation, i.e., against a violent temperature change, is enhanced. Since the uniformity of the film thickness of the compound semiconductor is good, a dark current is small in all elements and a high-performance characteristic can be obtained. Thereby, it is possible to improve a dark-current characteristic caused by a crystal defect or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an infrared detector using a semiconductor with a narrow forbidden band width and a method for manufacturing the same.

[Conventional technology]

Generally speaking, it is known that infrared detectors using semiconductors with a narrow forbidden band width have high sensitivity. In particular, a detector having a configuration in which single detection elements are arranged in one or two dimensions is very effective when used in an infrared imaging device.

The configuration of a conventional array type infrared detector is described, for example, in the magazine "NISPI" (S, P, I).

E)" (Vol. 443, 1983, p. 120), a semiconductor with a narrow bandgap is used in the infrared detector section, and a second signal source such as a silicon CC0 (S charge coupling element) is used. Hybrid Sodo purchasing connected to the processing section is known.

FIG. 3 is a sectional view showing a conventional array type infrared detector. In the figure, the configuration of a conventional array-type infrared detector is
CdTe substrate 11, go, 8Cdo, 2Te layer 1
2, a photodiode 13 formed on the Hgo, a Cd, 2T e layer 12 and serving as an infrared detection section, an indium column 14, and a signal processing chip 15 including a silicon CCD.
and a charge signal injection layer 16 to the signal processing section, and the infrared light 10 enters from the lower side in the figure. In this configuration, a photodiode 13 serving as an infrared detection section is formed in a Hgo, aCdo, and 2Te layer 12 epitaxially grown on a CdTe substrate 11, and an electric signal as an output is sent to a silicon CCD 15 through an indium column 14.
This is what you input. As a result, the output signal generated by the incident infrared light 10 at each infrared detector in the array is
The data is read out through the silicon CCD 15.

The reason why the above structure is effective will be described below.

First, since high sensitivity can be obtained by using a narrow band width semiconductor for the infrared detection section, Hgo, 8Cdo, and 2Te are used as the materials. in this case,
It can detect infrared rays with a maximum wavelength of about 10 μm. Further, the CdTe substrate 11 is transparent to infrared light and is effective as a substrate for epitaxial growth of the Hgo, 8cd0.2Te layer 12. When a large number of infrared detectors are arranged, especially in this two-dimensional arrangement, the output signal lines from the detectors have an extremely complicated configuration and must be read out to the outside through a signal processing chip 15 such as a CCD. However, in materials such as Hgo, 8Cdo, and 2Te,
It is not possible to make a high-performance CCD. Therefore, a high-performance COD is formed on silicon, where it is easy to make, and the two are connected. Hg Cd Te has a temperature of 0.80 at 100°C.
When exposed to high temperatures of 2 or higher, various crystal defects occur, so indium pillars 14, which can be bonded at low temperatures, are used for this connection.

The disadvantages of this array type detector are described below.

Generally, an array type infrared detector is used after being cooled to about 77°C using liquid nitrogen. In this case, it is efficient to cool the device only when it is actually used, rather than keeping it cool all the time, and doing so is a good idea. but,
In such cases, the detector will go through several temperature cycles between room temperature and low temperature. Silicon signal processing chip 1
5 and CdTe substrate 11, or Hg (1,g Cdo
, 2T e layer 12 have different thermal expansion coefficients, and furthermore, indium is a metal with extremely low mechanical strength, so such severe temperature fluctuations will put stress on the indium column 14, eventually causing it to break. It may come to that.

Therefore, the reliability of this array type infrared detector is low.

In order to overcome this drawback, a detector having the structure shown in "Advanced Infrared Detectors and Systems" (1983, p. 12) was devised. A cross-sectional view of this sideway is shown in FIG. 2. In FIG. 2, this detector includes an Hgo, sCd Te layer 17, an infrared detector formed on the Hgo, B Cd 0.2 Te layer 170.2, and an infrared detector formed on the Hgo, sCd Te layer 17. photodiode 18
, insulating adhesive 19, metal bar 20, connection wiring electrode 21, Jj37B hole 22, silicon CC
It has a signal processing chip 23 including D and a charge signal injection layer 24 to the signal processing section. In this case, Hgo9
g Cdo, 2T e The layer 11 is provided with holes corresponding to each infrared detecting section in the array, each photodiode 18 is formed around the through hole 22, and a connection wiring electrode is formed through the through hole 22. 21 is used to connect each infrared detection section, that is, the photodiode 18 and the charge signal injection layer 24. Thereby, the array of photodiodes 18 and the signal processing chip 23 are electrically connected. In this case, unlike the third factor structure, the silicon signal processing chip 23 and Hg
o, I3 Cdo, 2T e layer 17 is mechanically fixed by adhesive 19. Therefore, compared to the structure shown in FIG. 3, which is connected by indium columns 14, the mechanical strength is stronger and the reliability against temperature changes is higher.

[Problem to be solved by the invention]

However, the array type infrared detector having such a structure also has the following drawbacks in its manufacturing process. That is, in the case of a semiconductor with a narrow band gap, for example, HgCdTe,
The growth methods include bulk growth method and epitaxial growth method. Among these, it is well known that epitaxial growth is superior in crystal uniformity, which is an extremely important property in array-type infrared detectors. The epitaxially grown H
g (1, g Cd 0.2 T e layer is used in a detector with the structure shown in Fig. 4, Hg on a substrate such as CdTe etc.
04 Cdo and 2Te layers are grown, and the epitaxial growth side and silicon signal processing section are bonded and fixed by contact. The next step is to open a through hole.
s Cd 0.2 T e layer is several hundred μm CdT
Since the epitaxial growth is approximately 20 μm on the e substrate, the substrate such as Cd Te is mpA before opening the through hole.
A process of removing it by a method such as target polishing is required. In general, Hg1-xCdxTc is a material with very weak mechanical strength, so many crystal defects occur during the polishing process. If it shows good characteristics or has many crystal defects,
Dark current increases due to recombination at the surface or pnW interface, which causes detector malfunction. Mana 20
There are many difficulties in the polishing process for A1m or less, especially in terms of control over polishing thickness uniformity, and there is a possibility that variations in characteristics may occur within the array element.

An object of the present invention is to provide an array type infrared detector and a method for manufacturing the same which eliminates these drawbacks.

[Means to solve the problem]

In order to achieve the above object, in the array type infrared detector of the present invention, a compound semiconductor having a relatively narrow forbidden band width is epitaxially grown on the back surface of the silicon chip having the output signal processing section of the array type infrared detector, and Photodiodes are formed in an array on the compound semiconductor, and each photodiode is provided with a through hole corresponding to an output signal processing section of the silicon chip.

The photodiode and the output signal processing section of the silicon chip are electrically connected through the through hole.

The manufacturing method also includes the steps of bonding a silicon chip having an output signal processing section of an array type infrared detector to a relatively hard substrate, polishing the back surface of the silicon chip, and polishing the back surface of the polished silicon chip. a step of epitaxially growing a compound semiconductor with a narrow band gap; a step of arranging and forming photodiodes on the compound semiconductor; and a step of electrically connecting each of the photodiodes and the output signal processing section through a through hole. This includes:

[Effect]

In the array-type infrared detector of the present invention, a narrow bandgap compound semiconductor is directly epitaxially grown on the mirror-polished back surface of a silicon chip having an output signal processing section, and is further formed by arranging it on the compound semiconductor. Each of the photodiodes and the output signal processing section of the silicon chip are electrically connected to each other by a wiring electrode through a through hole.

Therefore, the reliability of the electrical wiring during operation, that is, against severe temperature fluctuations, is extremely high.

In the manufacturing method of the present invention, there is no polishing process that causes crystal defects in the compound semiconductor in which the photodiode is formed, and epitaxially grown crystals are used as they are, resulting in good film thickness uniformity of the compound semiconductor. It is. Therefore, all elements of the array-type infrared detector can exhibit low dark current and high performance characteristics.

Since the silicon chip is bonded to a relatively hard substrate and the back side is made thinner by polishing, the depth of the through hole can be shallow, and the electrical connection between the photodiode and the output signal processing section of the silicon chip is connection can be easily made.

In addition, on the back surface of the polished silicon signal processing chip, it is necessary to perform epitaxial growth of a compound semiconductor with a narrow M-bandwidth, or apply an appropriate buffer layer using the MBE method or the VI OCV D method. It is possible to grow a layer with sufficiently high crystal quality.

〔Example〕

Next, embodiments of the present invention will be described using the drawings.

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2(a)
, (b), (c), and (d) are diagrams for explaining the manufacturing method of the present invention to realize the embodiment shown in FIG. Here, HgCdo and 2Te layers were used as a narrow bandgap compound semiconductor.

0.8 First, the manufacturing method of the present invention will be explained using FIG. 2.

As shown in FIG. 2(a), a signal processing silicon chip 3 is bonded onto a sapphire substrate 1 using an adhesive 2 with the signal processing section 4 facing downward.

Next, the back surface of the signal processing silicon chip 3 is mirror-polished until the thickness becomes about 10 μm to expose the polished surface 9.

As shown in FIG. 2(b), the mirror-polished polished surface 9
Using the MBE method, Hgo, a CdO,2T
The e-layer 5 is epitaxially grown to a thickness of about 20 μm. Silikoshi and T[σ Cd T' e are not shown in the figure because their lattice constants are equal to 00.8 0.2, or here,
Ga, As, and CdTe layers are used as buffer layers.

Next, as shown in FIG. 2C, a through hole 7 is formed at the position of the signal processing section 4 by milling using the ion millijig method until the signal processing section 4 is reached.

Thereafter, a photodiode 6 is formed around the through hole 7 by ion implantation. The pitch of each photodiode was 50 μm, and the diameter was 25 μm.Finally, as shown in FIG. and the photodiode 6 are electrically connected. In this way, the array type infrared detector of the present invention is completed.

In the manufacturing method of the present invention, the back surface of the signal processing silicon chip 3 is polished to a thickness of about 10 μm, and then a Hgo, 8Cdo, and 2Te layer 5 of about 20 μm is directly deposited on the back surface.
m epitaxial growth.

Therefore, since there is no polishing process for the Hgo, aCdo, and 2Te layers 5, the Hg 066210 layer 5 has very few crystal defects. Further, since the photodiode b and the signal processing section 4 are separated by only about 10 μm, electrical wiring through the through hole 7 is very easy.

Next, the operation of the array type infrared detector of the present invention will be explained using FIG.

Incident infrared light 10 enters from the upper side in the figure.

The infrared light 100.8 absorbed by the Hg Cd 0 , 2 Te layer 5 generates carriers (E electrons or holes), and when the carriers reach the photodiode 6 within the diffusion length, they are output as an output signal. It is output from the signal processing section 4. As mentioned earlier, due to the manufacturing process, Hg Cdo, 2 T
Since the e-layer 5 is almost uniform in all elements and has very few crystal defects, the dark current caused by recombination current at the surface and p-n junction interface caused by this is greatly improved. A high-performance array-type infrared detector can be realized.

In addition, since the connection between the photodiode 6 and the signal processing section 4 is made using the connection wiring electrode 8 through the through hole 7, the connection strength is strong (and it can withstand severe temperature fluctuations without damage or deterioration). less likely to occur.

〔Effect of the invention〕

As explained in detail above, the present invention provides an array-type infrared detector that can significantly improve dark current characteristics caused by crystal defects, has excellent reliability against severe temperature fluctuations, and has high performance. can be served as a culm offering.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an array type infrared detector which is an embodiment of the present invention, and FIGS. 2(a), (b), (c)
. (d) is a diagram for explaining the manufacturing method of the present invention for realizing the array type infrared detector shown in FIG. 1, FIGS. 3 and 4.
The figure is a sectional view for explaining a conventional example. ■...Sapphire substrate 2,19...Adhesive 3
, 15.23...Silicon chip for signal processing 4...
Signal processing unit 5, 12.17...Hg Cd O, 2T e
Layer 0.8 6, 13.18... Photodiode 7.22... Through hole 8.21... Connection wiring electrode 9... Polished surface 10... Infrared light 11...
・CdTe substrate 14... Indium columns 16, 2
4...Charge signal injection layer 20...Metal pad Patent applicant NEC Corporation Representative Patent attorney Kanno Nakabox 1 Figure 2 (fc) Figure 2 Figure 4

Claims (2)

[Claims] (1) A compound semiconductor having a relatively narrow forbidden band width is epitaxially grown on the back surface of a silicon chip having an output signal processing section of an array type infrared detector, and photodiodes are arranged and formed on the compound semiconductor, Each of the photodiodes is provided with a through hole corresponding to the output signal processing section of the silicon chip, and the photodiode and the output signal processing section of the silicon chip are electrically connected through the through hole. Array type infrared detector. (2) A step of bonding a silicon chip having an output signal processing section of an array type infrared detector to a relatively hard substrate, polishing the back surface of the silicon chip, and forming a narrow band gap on the back surface of the polished silicon chip. a step of epitaxially growing a compound semiconductor; a step of arranging and forming photodiodes on the compound semiconductor; and a step of electrically connecting each of the photodiodes and the output signal processing section through a through hole. A method for manufacturing an array-type infrared detector.