JPS63316489A - Manufacture of infrared sensor - Google Patents

Abstract

PURPOSE:To obtain an infrared sensor having a high S/N ratio and high reliability by making a single crystal as material thinner after etching or polishing the above crystal as well from the rear side through a hole which is made on the substrate when the untreated single crystal is affixed on the above substrate. CONSTITUTION:After fixing a single crystal as material, which is thinned to some extent on a substrate where a hole is made, etching or polishing of the single crystal as material from the rear side through the above hole as well makes its crystal further thinner and then, electrodes and the like are formed and the resultant infrared sensor is formed. For example, a board body 1 consisting of an n-type HgCdTe single crystal is affixed to the center part of a sapphire substrate 2 where a hole 3 is made at its center part. After the single crystal rear side is etched in a spheric form, a through hole 4 is made at the crystal center part and then, an indium (In) electrode 5 as well as a lead 6 are installed and zinc sulfide is coated to complete an infrared sensor. As this sensor lessons an internal strain very much and makes a S/N ratio high, it has a good performance.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor infrared sensor, that is, an optical Q-type infrared sensor, and in particular, aims to improve the manufacturing yield thereof and improve the performance. Concerning methods for measuring.

[Prior art and its problems]

Semiconductor infrared sensors are devices that have been widely used in Ila cameras, thermographs, infrared spectrometers, and the like because they have a high temperature and a high response speed.

In the photoconductive mode sensor, which is the most widely used sensor in the past, a single crystal compound semiconductor material such as indium antimony (InSb) or water-limited cadmium tellurium (HQCdTe) is processed into a thin plate shape, electrodes are attached, and then a reflective layer is formed. The surface is coated with a protective film.

By the way, most of the infrared light incident from the surface is absorbed at a depth of several micrometers, so in principle, if a single crystal of approximately two materials is thinned to a thickness of several micrometers, the Ba current will decrease and the S
It is thought that this improves the /N ratio.

However, as shown in Figure 2, as the thickness of the crystal becomes thinner, lattice defects due to bending deformation, etc. increase.
Due to the characteristics of the sensor, a problem arises in that the noise becomes harsh. Therefore, the practical optimum thickness is several tens of micrometers. However, even if the thickness is several tens of micrometers, crystal plane technology is required to thin the crystal without leaving processing strain that causes lattice defects.
For compound 2r conductors such as 2r conductors, there is no established strain uniformity thinning technology, and the technology is currently accumulated as know-how by each manufacturer.

For example, due to crystal imperfections due to processing strain, etc., energy gap abnormalities due to lattice defects or local non-uniformity of composition, or poor surface treatment, etc. can't get it.

■There is variation in the sensitivity distribution on the light receiving surface.

In the performance inspection of finished sensor products, many products are rejected due to high noise, resulting in a problem of poor manufacturing yield.

Furthermore, the crystal material is also expensive, which is the main reason why semiconductor infrared sensors are expensive.

Therefore, in order to solve these problems, a method of improving the S/N ratio by arranging electrodes (Japanese Patent Laid-Open No. 56-36028
), or a method of correcting variations in characteristics depending on the light receiving position using an electric circuit (Japanese Patent Application Laid-Open No. 132031/1983), etc. have been attempted.

However, none of these methods provides an essential solution, and improvements in characteristics have been desired.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an infrared sensor with a high S/N ratio and a high manufacturing yield.

[Solve the problem! ζth means]

Therefore, in the present invention, after pasting a wood single crystal that has been made into a cast plate to some extent on a substrate with holes, the material single crystal is further etched or polished from the back side through the holes to thin it. A comb, electrodes, etc. are formed to form an infrared sensor.

[Effect]

According to the above method, since there is no adhesive H in the hole part,
Even if the single crystal is thinner in this area, there is no addition of lattice defects due to residual stress in the adhesive layer, and the average thickness of the entire light-receiving area can be reduced, making it possible to significantly reduce the 'ifi M flow. can.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

First, as shown in FIG. 1(a), an n-type HgCdTe single crystal was sliced with a diamond cutter parallel to the (100) plane to form a plate-like body 1 of 3.5ffi#+X3.5m and 500μm thick. It was lapped with #3000 silicon carbide (S i C) abrasive grains to a thickness of 300 μm.

Thereafter, a Teflon frame was attached around the plate-shaped body 1 in the shape of a picture frame, and etching was performed with 5% bromine methanol until the thickness reached 200 μm. Further, the Teflon frame was removed and washed with methanol.

The plate-shaped body formed in this way has a somewhat thicker circumference due to variations in etching, so a mask (not shown) is attached to the central part.
Only the OOam portion is left and the surrounding area is removed by etching with 5% bromethanol. Then, it is washed with methanol in the same manner (FIG. 1(b)).

On the other hand, a sapphire substrate 2 with a thickness of 500 μm was placed in a 10 m
C) Cut into u+, and drill a hole 3 with a diameter of 1.5 in the center using ultrasonic processing. At this time, diamond was used as the abrasive grain, and each processing was operated under processing conditions of 36kHz and 25W. Thereafter, it was further lapped with diamond abrasive grains, mirror-finished, and then cut into a size of 3 U x 3 U.

In this way, as shown in FIG. 1(C), a plate-like body 1 made of the HqCdTe single crystal washed with methanol is coated with epoxy resin at the center of the sapphire substrate 2, which has a hole 3 drilled in the center. Attach using.

After the epoxy resin has hardened, the whole is immersed in 5% bromine methanol again and etched until the thickest single crystal periphery reaches 50 μm.

Further, etching is performed with 1% and 0.5% bromethanol for 5 minutes and 10 minutes, respectively.

At this time, the surface becomes a mirror surface, and the edge of the single crystal is approximately 40 μm thick.
It became. Furthermore, when observed from the back side through a hole in the sapphire substrate, the back side of the single crystal was etched into a spherical shape as shown in Figure 1(d)! g was approved.

Next, as shown in Figure 1(e), place the single crystal with the top surface, and while dropping 1% bromine methanol from the vertical direction into the hole using a glass villet, examine the crystal using a magnifying glass. Observe the situation and repeat this process until fine communication holes are created in the middle part of the crystal. As soon as the communicating holes 4 were formed, the whole was exposed to hot methanol and thoroughly cleaned.

Here, the reason why the cleaning was performed in methanol vapor without using methanol liquid is to prevent the crystals around the holes from being permanently deformed by the liquid pressure.

Finally, as shown in FIG.
nS) coating was applied to complete an infrared sensor, and its performance was evaluated.

Here, FIG. 1(f) is a sectional view taken along the line AA in FIG. 1(q).

Note that the area of the light receiving section is 1. It was set as Oa2.

Performance measurements were carried out with the completed sensor set in a commercially available de-wax bottle and cooled with liquid nitrogen. As a light source, a blackbody furnace at 500° was used, and the standardized S/N ratio was determined to be 2X as shown in the following table.
109 ((IHz ""W-1>.

At this time, the average crystal thickness of the entire light receiving area is approximately 1
It was 5 μm. The fact that the internal strain is extremely small despite the small average thickness is due to the fact that S/N
Needless to say, this is the reason for the high ratio and high performance.

For comparison, we created the following two infrared sensors,
Performance was measured.

Comparison Example 1 3rm formed in the same manner as in Example except for the drilling process.
On a sapphire substrate of After the height reaches 50μm,
The crystal surface is mirror-finished by immersing it in 1% and 0.5% bromethanol for 5 and 10 minutes, respectively. At this time, the thickness was 40 μm, and since there were no holes in the sapphire substrate, the crystal was never etched from the back surface.

Then, in exactly the same manner as in the examples, after attaching electrodes and lead wires and forming an anti-q dimension film, performance evaluation was performed.

As shown in the table below, the crystal has an S/N ratio of 4X108 (
(JH2""W-'), and it is clear that excellent performance cannot be achieved because the average thickness of the delivered product is large.

Comparison Example 2 In exactly the same manner as Comparative Example 1, the average thickness of the crystal was 35 μm.
After reaching the desired temperature, mirror finishing was performed, the final thickness was set to 25 μm, electrodes and lead wires were attached in the same manner, and an antireflection film was formed, followed by performance evaluation.

As shown in the table below, the results show that the S/N ratio is 1×108 (
c! RH21/2W-1).

It is clear that because the final thickness of the crystal is too small, the crystal is distorted by the residual stress of the contact layer 12 and good performance cannot be obtained.

A comparison of this table also shows that the S/N ratio of the infrared sensor formed by the method of the example of the present invention is extremely excellent.

In the example, the etching end point of the single crystal was set at a point where a fine through hole was formed, but the N311 hole does not need to be formed, and etching may be performed until it is as thin as possible.

Furthermore, the etching method is not limited to the embodiments, and any method with good reproducibility may be selected as appropriate.

In addition, it goes without saying that the method of the present invention is applicable not only to HqCdTetl crystals but also to other materials.

〔Effect of the invention〕

As explained above, according to the method of the present invention, after a Δ material single crystal is adhered to a substrate formed with holes, a kite material single crystal is further attached from the back side through the holes. Since C is thinned by etching or polishing, it is possible to provide an infrared sensor with a high S/N ratio and high reliability.

[Brief explanation of drawings]

Figures 1(a) to 1(c) are manufacturing process diagrams of an infrared sensor according to an embodiment of the present invention, and Figure 2 is a diagram showing the thickness and S/N ratio of a single crystal material in a conventional sensor. 1 is a diagram showing the relationship between the following: 1... Material single crystal (plate-like body), 2... Sapphire blocking plate, 3... Hole, 4... Orifice, 5... Electrode, 6 ...Lead wire, 7...Anti-reflection film. Fig. 1 (a) Fig. 1 (b) Fig. 1 (C). Fig. 1 (d) to Fig. 1 (e) Fig. 1 (f) Figure 1 (9)

Claims (3)

[Claims] (1) When manufacturing an infrared sensor comprising an electrode on a thin plate made of a photoconductive material, an adhesion step of adhering a material single crystal onto a support substrate having holes formed therein; and the above-mentioned steps. A thinning step of thinning the material single crystal from the back side through the hole, and a sensor forming step of arranging electrodes on the thinned material single crystal to form a sensor. A manufacturing method for a featured infrared sensor. (2) The method for manufacturing an infrared sensor according to claim (1), wherein the thinning step is a wet etching step in which the entire plate is immersed in an etching solution and the plate is thinned by etching. (3) The thinning process includes: a first etching process in which the entire plate is immersed in an etching solution to make the plate thin; a second etching process in which the entire plate is immersed in a low-concentration etching solution to make the surface mirror-like; and the holes. and a third etching step of dropping an etching solution into the hole while observing the hole so that it is on the upper surface, and performing final etching until a predetermined thickness is reached. ) The method for manufacturing the infrared sensor described in item 2.