JPH05226685A - Manufacture of photodetector - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a photodetector in which electrodes can be accurately formed and element isolation can be effectively conducted. CONSTITUTION:An insulating film 11 of a predetermined pattern is formed on a semiconductor substrate 1. With the film 11 as a mask a recess 14 is formed on the substrate 1. One conductivity type semiconductor layer and an opposite conductivity type layer to the semiconductor layer are sequentially laminated and buried in the recess 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a photo-sensing element, and more particularly to a method for manufacturing a photo-sensing element capable of reliably separating elements and forming electrodes with high precision.

A photo-sensing element such as an infrared sensing element is required to have high sensitivity and high resolution.
It is desired to form a high-density photodetection element on a single compound semiconductor substrate, and a large area is required for the light-receiving portion of the photodetection element.

By the way, when the photo-sensing elements are arranged at a high density as described above, a phenomenon in which a detection signal cross-talks between the elements is likely to occur. Therefore, various methods for element isolation have been proposed.

[0004]

2. Description of the Related Art A conventional method for manufacturing a photodetector will be described. As shown in FIG. 3 (a), MOCV is formed on a CdTe substrate 1.
An n-type HgCdTe layer 2 and a p-type HgCdTe layer 3 are sequentially laminated by D (Metal Organic Chemical Vapor Deposition).

Next, as shown in FIG. 3B, a resist film (
Etching is performed until the CdTe substrate 1 is reached by using a mesa etching solution composed of a mixed solution of bromine (Br ₂ ) and methanol (CH ₃ OH) using a mask (not shown) as a mask. Since this CdTe substrate 1 has high resistance, n-type Hg formed on the CdTe substrate 1
The photodiode 4 composed of the CdTe layer 2 and the p-type HgCdTe layer 3 is separated between elements.

After removing the resist film described above,
As shown in FIG. 3 (c), an electrode 5 made of gold is formed on the p-type HgCdTe layer 3 and the n-type HgCdTe layer 2 to form a mesa type photovoltaic photodetecting element.

With such a method, a low concentration of n-type Hg, which is difficult to form by the conventionally used ion implantation method, is used.
It is possible to form a pn junction having a high concentration p-type HgCdTe layer 3 on the active layer composed of the CdTe layer 2, and it is possible to manufacture a hole-injection type photodiode array with low mobility and to achieve zero bias. It is possible to manufacture a photo-sensing element with improved characteristics.

[0008]

By the way, when the elements are separated by the mesa etching as described above, the surface of the substrate 1 is not flat, and when the electrode 5 is formed, the n-type HgCdTe etched in the mesa type is formed. After gold for electrode formation is formed on the layer 2 and the p-type HgCdTe layer 3 by vapor deposition or the like, a resist film is formed thereon to form an electrode film of the gold in a predetermined pattern. There is a step of developing the resist film after exposing to a predetermined pattern using a photomask.

In this process, as shown in FIG. 3 (c), the substrate 1
If the surface is not flat, a step will be created in the resist film formed on the substrate, and the photomask cannot be installed in close contact with the resist film, and contact exposure cannot be performed, resulting in poor exposure accuracy. Therefore, there is a problem that the electrode 5 cannot be formed in a predetermined pattern with high accuracy.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and provide a method for manufacturing a photo-sensing element which can form electrodes with high precision and can ensure element isolation.

[0011]

According to a method of manufacturing a photo-sensing element of the present invention, an insulating film having a predetermined pattern is formed on a semiconductor substrate, and the insulating film is used as a mask on the substrate. A recess is formed, and a semiconductor layer of one conductivity type and a layer of the opposite conductivity type of the semiconductor layer are sequentially stacked and embedded in the recess.

According to a second aspect of the present invention, the recess according to the first aspect is etched with an isotropic etching solution to form an overhang structure in the insulating film, and a semiconductor layer laminated in the recess is formed by a vapor phase growth method. The compound semiconductor layer formed in 1.

[0013]

According to the method of manufacturing a photodetecting element of the present invention, the insulating film is formed so as to overhang the concave portion where the photodetecting element is to be formed so as to overhang the structure. Since the n-type layer is exposed in a flat state below the insulating film overhanging the hang structure, the photomask can be brought into close contact with the resist film used when forming the electrode pattern, so that the exposure accuracy is improved and the electrode pattern is improved. Can be formed with high precision.

Further, since the HgCdTe crystal for forming the photodiode is vapor-phase-grown and buried in the recess formed in the high-resistance semiconductor substrate, element isolation can be surely performed.

[0015]

An embodiment of the present invention will be described in detail below with reference to the drawings. As shown in Fig. 1 (a), Si is formed on the CdTe substrate 1.
The insulating film 11 made of an O ₂ film is formed by a method such as vapor deposition.

Next, as shown in FIG. 1 (b), a resist film 12 is formed on the substrate 11, and using the resist film 12 as a mask, an etching solution of a mixed solution of hydrofluoric acid and ammonium fluoride is used. The insulating film 11 is etched into a predetermined pattern.

Then, as shown in FIG. 1C, a recess 13 having a depth of 12 μm and an area of 20 μm × 20 μm is formed by ion beam etching using the patterned insulating film 11 as a mask.

Then, as shown in FIG. 1 (d), bromine (Br ₂ )
By etching the substrate 1 using an isotropic etching solution composed of a mixed solution of methanol and CH ₃ OH, a concave portion 15 that extends in the lateral direction is formed. In this way, the insulating film 11
Has a structure overhanging above the concave portion 14, and an overhang structure can be formed.

Then, as shown in FIG. 2 (a), dimethylcadmium [Cd (CH ₃ ) ₂ ] and diisopropyl tellurium [Te (C ₃ H ₅ )]
₂ ], mercury (Hg), trimethylindium [(CH ₃ ) ₃ In]
Is used as a source gas, and a low-concentration n-type HgCdTe layer 2 having a thickness of 10 μm and a carrier concentration of 1 to 5 × 10 ¹⁵ / cm ³ is formed as M
It is formed by the OCVD method. This n-type HgCdTe layer 2 is made of SiO ₂
Does not grow on the insulating film 11.

Then, as shown in FIG. 2 (b), dimethylcadmium [(CH ₃ ) ₂ Cd] and diisopropyl tellurium [Te (C ₃ H ₇ )]
₂ ], mercury (Hg), and butylarsine (C ₄ H ₉ ) As H ₂ as source gases, the thickness is 2 μm and the carrier concentration is 10 μm.
MOCVD of highly concentrated p-type HgCdTe layer 3 of ¹⁶ to 10 ¹⁷ / cm ³
Form by method. The high-concentration p-type HgCdTe layer 3 can be easily formed by the MOCVD method described above.

By using the MOCVD method in this way,
Low-concentration n-type HgCd that is difficult to control and form by ion implantation
The high-concentration p-type HgCdTe layer 3 can be reliably and easily formed on the Te layer 2.

Next, as shown in FIG. 2 (c), the insulating film 11 thus formed is removed by etching to expose the surface of the CdTe substrate 1. Then, the n-type HgCdTe layer 2 and the p-type HgCdTe layer 3 are exposed on the surface in a flat state. Therefore, when the electrode 5 is formed, after forming a gold electrode film forming metal film on the substrate, Even if a resist film is formed thereon, the resist film can be formed in a flat state. Therefore, a photomask for exposure of the resist film can be closely attached to the resist film, and contact exposure can be performed, so that the exposure accuracy of the resist film is improved and the resist pattern can be formed with high accuracy. By etching the above-mentioned metal film for forming an electrode film using as a mask, the electrode 5 can be formed with a predetermined pattern with high precision.

Since the pn junction portion forming the photodiode is surely buried in the recess 14 of the high resistance CdTe substrate 1, element isolation can be surely performed.

[0024]

As described above, according to the method for manufacturing a photodetecting element of the present invention, element separation can be reliably performed, and the electrode forming surface is formed flat, so that the electrode forming surface can be formed. The exposure accuracy of the resist film is improved, the electrodes can be formed in a predetermined pattern with high accuracy, and the reliability of the device is improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing steps of a manufacturing method of the present invention.

FIG. 2 is a cross-sectional view showing steps of the manufacturing method of the present invention.

FIG. 3 is a cross-sectional view showing a conventional manufacturing method.

[Explanation of symbols]

1 CdTe substrate 2 n-type HgCdTe layer 3 p-type HgCdTe layer 4 photodide 5 electrode 11 insulating film (SiO ₂ ) 12 resist film 13,14 recess

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor ▲ Sai Tetsuo Fuji, Tetsuo 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (2)

[Claims] An insulating film (11) having a predetermined pattern is formed on a semiconductor substrate (1), and a recess (14) is formed in the substrate (1) using the insulating film (11) as a mask. A method of manufacturing a photo-detecting element, characterized in that a semiconductor layer (2) of one conductivity type and a layer (3) of the opposite conductivity type of the semiconductor layer are sequentially laminated and embedded in (14). 2. The recess (14) according to claim 1 is etched with an isotropic etching solution so that the end of the insulating film (11) has a recess (14).
A photo-sensing device having an overhang structure for covering the above, wherein the two semiconductor layers (2, 3) laminated in the recess (14) are compound semiconductor layers formed by a vapor phase growth method. Production method.