JPH0648731B2 - Photovoltaic Infrared Detector Manufacturing Method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a photovoltaic infrared detection element, which is a combination of a compound semiconductor that performs photoelectric conversion and a semiconductor element that performs signal processing.

[Prior Art] A pn diode made of a compound semiconductor such as HgCdTe or InSb is a photovoltaic infrared detection element.
It is used as a detector for arranging two-dimensionally or two-dimensionally to obtain an infrared image. When operating such an infrared detector, further signal processing circuits, specifically individual pn
CC for reading the signal output of the diode in time series
A multiplexer such as a D or MOS switch array, a preamplifier for amplifying a weak signal output, and various higher-level signal processing circuits are required. However, it is difficult to realize such a signal processing function with HgCdTe or InSb, which are infrared detection element materials.Therefore, the signal processing circuit is formed on a Si substrate and electrically connected to each diode of the detection element. ing. As a method of this connection, for example, Proceeds of SPIE, 510
The loophole method, published on page 121, is known. The outline of this method is shown in FIG. First, Fig. 2
As shown in (a), compound semiconductor crystals, such as HgCdTe crystals
22 is a semiconductor element on which a signal processing circuit is formed, for example, Si
Bonded onto the IC 21 via the adhesive layer 23, and then shown in FIG.
As shown in (b), the HgCdTe crystal 22 on the signal input section 25 is removed and a through hole 24 is provided. Further, as shown in FIG. 2 (c), after the pn diode 27 is formed with the peripheral portion of the through hole as the n-type region 26, the n-type region 26 and the signal input part are formed.
A conductor electrode 28 connecting 25 is formed. As described above, each pn diode of the compound semiconductor crystal is connected to the signal processing circuit of the semiconductor element.

[Problems to be Solved by the Invention] However, when actually manufacturing an element by the above method, the step of forming a through hole in a compound semiconductor is not easy. That is, an ion milling method is used to form a through hole having a diameter of about 10 μm or less in a compound semiconductor having a thickness of about 10 μm, and the compound semiconductor and the adhesive layer immediately thereunder are collectively removed. However, at this time, there are variations in the thickness of the compound semiconductor and the thickness of the adhesive layer, and even though the adhesive layer has not been removed in the thick portion, not only the adhesive in the thin portion but In many cases, the signal input section is also removed, resulting in a poor connection. Therefore, the through-hole forming process is greatly affected by manufacturing variations, which causes a decrease in the yield rate, and there is a problem that productivity is inferior due to the need for more strict thickness control. It was

An object of the present invention is to solve the above-mentioned conventional problems, and to provide a method for manufacturing a photovoltaic infrared detecting element in which loop holes can be easily formed and productivity is improved.

[Means for Solving the Problems] According to the present invention, a compound semiconductor crystal is adhered to a semiconductor element on which a signal processing circuit is formed, and a pn junction formed around a through hole provided in the compound semiconductor crystal. In a method for manufacturing a photovoltaic infrared detecting element in which a conductor electrode connecting a p-type or n-type region and a signal input part of the semiconductor element is formed, the compound semiconductor crystal at a predetermined position by an ion milling method. Is removed, and then the exposed adhesive is removed by etching in oxygen gas plasma to form the through hole, which is a method for manufacturing a photovoltaic infrared detecting element.

[Embodiment] Next, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a vertical cross-sectional view showing a method of manufacturing a photovoltaic infrared detecting element according to an embodiment of the present invention, and particularly showing through-hole forming steps in the order of steps. In this example, a p-type HgCdTe crystal is used as the compound semiconductor crystal, and Si is used as the semiconductor element.
IC was used. First, as shown in Fig. 1 (a), SiIC
P-type HgCdTe crystal 2 adhered onto 1 via an adhesive layer 3
A photoresist pattern 4 is formed on the upper surface. The photoresist pattern 4 is a pattern in which a hole is formed in a portion directly above the signal input portion 5 on the SiIC 1. Here, the thickness of the HgCdTe crystal 2 is set to about 10 μm, and
Although not shown in C1, HgCd formed in a later step
A signal processing circuit such as a multiplexer circuit such as a CCD or a MOS switch array for extracting signals from a pn diode arranged in a Te crystal array in a time series, an amplification circuit such as a preamplifier integration amplifier, etc. is formed. The signal input section 5 made of a body material is provided corresponding to each pn diode. Next, as shown in FIG. 1B, ion milling is performed using the photoresist pattern 4 as a mask to remove the exposed portion of the p-type HgCdTe crystal and expose the adhesive layer 3. If the thickness of the HgCdTe crystal 2 varies, the thick crystal portion should be completely removed. Therefore, in the thin crystal portion, the signal input portion 5 directly below the adhesive layer 3 is partially removed. There is. Next, as shown in FIG. 1 (c), plasma etching is performed in an oxygen gas atmosphere to remove the adhesive layer 3. In the oxygen gas plasma etching, only organic substances such as the adhesive layer 3 and the photoresist 4 are selectively removed, and the compound semiconductor crystal such as the HgCdTe crystal 2 and the semiconductor element such as the SiIC 1 and the conductor of the signal input unit 5 are not required. Not affected. Therefore, the thickness of the remaining adhesive layer 3 is largely varied during the bonding and by the ion milling performed before the plasma etching, but nevertheless, it is exposed at the hole 2 of the HgCdTe crystal. Since only the adhesive layer 3 is removed and the etching is stopped when the signal input portion 5 is exposed, the signal input portion is not removed unlike the conventional case. Thus, the through hole forming process is completed. After this, as in the conventional manufacturing method, the pn diode 7 is formed by the ion implantation method or the impurity diffusion method with the peripheral portion of the through hole as the n-type region 6 as shown in FIG. The body electrode 8 is formed to connect the n-type region 6 and the signal input unit 5. Although not shown, the p-type portion of the HgCdTe crystal 2 is also connected to the SiIC 1 in the same manner as above, so that the HgCdTe crystal for photoelectric conversion and the SiIC for signal processing are connected.
Are combined with each other, and the manufacturing of the photovoltaic infrared detecting element is completed.

Next, the manufacturing method of the present invention will be compared with the conventional method. HgCd
The thickness of the Te crystal is usually about 10 μm, and its variation is about 1 μm. This variation corresponds to about 6 minutes as the ion milling time. Furthermore, the thickness of the adhesive layer is usually 1 μm or less, but the variation is about several thousand Å, and the difference in ion milling time is about tens of minutes. Therefore, according to the conventional method, the total of the two is Variation of about 20 minutes occurs. On the other hand, as a conductor of the signal input section, this ion milling time is 0.5 ~ depending on the material.
This corresponds to a thickness of 2 μm. Generally, the thickness of the conductor of the signal input portion is about 1 μm at the maximum, and therefore, due to the above variation, the adhesive layer still remains in some portions, but the signal input portion is removed in other portions. As a matter of course, the connection between the HgCdTe crystal and the SiIC becomes poor. On the other hand, in the manufacturing method of the present invention, ion milling is used only to remove the HgCdTe crystal, and the variation in the thickness of the HgCdTe crystal is sufficiently absorbed by partially etching the adhesive layer. By selectively removing only the adhesive layer, the problems of the conventional example can be solved.

In the above examples, HgCdTe was used as the compound semiconductor crystal.
An example using a crystal is shown, but the same applies when InSb or the like is used. Furthermore, in the above-described through-hole forming process, a small amount of surface oxide layer depending on the conductive material of the signal input portion can be removed by performing ion milling for a short time after oxygen gas plasma etching, and the process is complicated. However, the electrical connection can be made more reliable.

[Effects of the Invention] As described above, according to the present invention, it is possible to significantly improve the connection failure in the joint portion between the compound semiconductor crystal that performs photoelectric conversion and the semiconductor element that performs signal processing, and further, the compound semiconductor crystal and the adhesive agent. Since it is not necessary to strictly control the thickness of the, the productivity can be improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a through hole forming step in one embodiment of the present invention, and FIG. 2 is a vertical sectional view showing a conventional through hole forming step. 1,21 …… SiIC, 2,22 …… p-type HgCdTe crystal 3,23 …… Adhesive layer 4 …… Photoresist pattern 5,25 …… Signal input part 6,26 …… N-type area 7,27 ...... pn diode 8,28 ...... conductor electrode, 24 ...... through hole

Claims (1)

[Claims] 1. A compound semiconductor crystal is adhered to a semiconductor element having a signal processing circuit formed therein, and a p-type pn junction is formed around a through hole provided in the compound semiconductor crystal.
In a method of manufacturing a photovoltaic infrared detecting element in which a conductor electrode for connecting a p-type or n-type region to a signal input part of the semiconductor element is formed, the compound semiconductor crystal at a predetermined position is formed by an ion milling method. A method of manufacturing a photovoltaic infrared detecting element, comprising the steps of removing and then exposing the exposed adhesive in an oxygen gas plasma to remove the through hole.