JPH0447989B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method of manufacturing an infrared sensing element using a photoconductive phenomenon.

[Conventional technology]

FIG. 4 is a sectional view showing the structure of a conventional photoconductive infrared sensing element, and FIG. 5 is a plan view thereof. In these figures, 1 is a high-resistance substrate, 2 is a compound semiconductor such as HgCdTe, 3 is a light-receiving surface, and 4 is a high-resistance substrate.
5 is a first protective film of the light-receiving surface 3 formed of an anodic oxide film of the compound semiconductor 2, 5 is a second protective film of the light-receiving surface 3 made of, for example, ZnS, and 6 is an electrode.

Next, a method for manufacturing a conventional photoconductive type infrared sensing element will be explained using FIGS. 4 and 5.

First, a wafer is manufactured by forming a compound semiconductor 2 made of HgCdTe or the like to a predetermined thickness on a high-resistance substrate 1 by a method such as epitaxial growth.

Next, the wafer is cut using a dicing saw or the like according to the dimensions of the device to be fabricated, and then
Lightly etch the wafer surface with a Br ₂ -methanol solution to clean the surface.

Next, the wafer is immersed in a potassium hydroxide (KOH) electrolyte, the compound semiconductor 2 on the wafer is used as an anode, and carbon is used as a cathode, and a voltage is applied between both electrodes to form an anodic oxide film, followed by photolithography. The first protective film 4 is then patterned into a predetermined shape.

Next, the material constituting the second protective film 5, e.g.
After sputtering ZnS over the entire surface of the wafer, it is patterned into a predetermined shape by photolithography to form the second protective film 5.

After that, using a vapor deposition mask, for example, In is vapor-deposited on the part excluding the light-receiving surface 3 to form the electrode 6,
Manufactures infrared sensing elements.

[Problem that the invention seeks to solve]

In the conventional manufacturing method of an infrared sensing element as described above, the anodic oxide film, which becomes the first protective film 4, is contaminated by the photoresist etc. used when patterning it into a predetermined shape, and the second protective film 4 is contaminated. There were problems in that the protective film 5 was difficult to adhere to, and even if it did adhere, the characteristics of the device deteriorated.

This invention was made to solve the above-mentioned problems, and provides a method for manufacturing an infrared sensing element in which the anodic oxide film, which is the first protective film, is not contaminated in subsequent steps.

[Means for solving problems]

The method for manufacturing an infrared sensing element according to the present invention includes:
A process of forming a compound semiconductor layer on which an infrared sensing element is formed on a high-resistance substrate, and an insulator on one side and a part or all of the other side on the surface of the compound semiconductor layer other than the light receiving area. Pressing the other side of the anodic oxidation electrode/mask of a desired shape made of metal and plasma anodizing the surface of the light receiving region of the compound semiconductor layer to form a first protective film; a step of forming a second protective film on the first protective film so as to cover it; and a step of forming an electrode on the second protective film except for a portion corresponding to the first protective film. It includes.

[Effect]

In this invention, since the formation and patterning of the anodic oxide film are performed at the same time, the second protective film can be formed immediately after the formation of the first protective film, and the first protective film will not be contaminated in a later process. never be done.

〔Example〕

Figures 1 to 3 are diagrams illustrating a method for manufacturing an anodic oxide film, which is the first protective film in this invention.
This method is used in place of the conventional process of forming an anodized film in a KOH electrolyte and photolithography.

In FIGS. 1 to 3, 7 is an anodizing electrode and mask, for example, on one side of a thin plate 8 of quartz glass.
For example, it is formed by vapor depositing a metal vapor deposition film 9 such as gold. Reference numerals 1 and 2 are high-resistance substrates and compound semiconductors that constitute the wafer after cutting with the same dicing saw as in the conventional example.

FIG. 3 is a structural diagram of a commercially available plasma anodizing device, in which 10 is a vacuum vessel, 11 is a lower electrode,
12 is an upper electrode, 13 is a high frequency source, 14 is a gas introduction tube, and 15 is a quartz cover. 16 is a wiring for electrically connecting the anodic oxidation electrode/mask 7 of the present invention and the lower electrode 11 of the plasma anodization apparatus.

Plasma anodic oxidation is a method in which a sample is inserted into oxygen plasma generated by high-frequency discharge, and a positive voltage is applied to the sample with respect to other electrodes in the plasma to perform anodic oxidation. When a compound semiconductor such as GaAs is anodized using the apparatus shown in FIG. 3, the sample is placed on the lower electrode 11 and the vacuum vessel 10
After evacuating the inside to a vacuum, oxygen gas is introduced, oxygen plasma is generated by high-frequency discharge, and a voltage is applied between the lower electrode 11 and the upper electrode 12. In this case, since the sample is conductive, a voltage can be applied between the sample and the upper electrode 12 simply by placing the sample on the lower electrode 11, and no other special electrodes are required.

However, since the compound semiconductor 2 in this invention is formed on the high-resistance substrate 1, it cannot be anodized simply by placing it on the lower electrode 11 as described above.

Therefore, in the present invention, as shown in FIGS. 1 to 3, an anodic oxidation electrode/mask 7 is covered so that the metal vapor deposited film 9 side is in contact with the surface of the compound semiconductor 2, and the gap between the metal vapor deposited film 9 and the lower electrode 11 is electrically connected. connected.
In this way, the compound semiconductor 2 and the upper electrode 12
A voltage can be applied between. Note that if the surface of the anodic oxidation electrode/mask 7 is a conductor, a current will flow through this portion and prevent anodic oxidation of the compound semiconductor, so the surface was made of quartz glass, which is an insulator.

By the above method, the compound semiconductor 2 on the high-resistance substrate 1 can be anodized in the same way as when an anodizing current flows from the front surface to the back surface of the compound semiconductor as in the case of GaAs.

Furthermore, in this invention, the formation and patterning of the anodic oxide film are performed at the same time.
As shown in the figure, the anodic oxidation electrode/mask 7 was processed into, for example, a U-shape so that only the region where the first protective film 4 was to be formed was exposed. If plasma anodization is performed in this way, the part under the anodic oxidation electrode/mask 7 will not be anodized, and only the part exposed to the outside of the anodic oxidation electrode/mask 7 will be anodized. The first protective film 4 having the same shape as the conventional example can be formed without using photolithography. After forming the first protective film 4, the anodic oxidation electrode/mask 7 is removed.

The second protective film 5 and the electrode 6 are formed in exactly the same manner as in the conventional example, and an infrared sensing element can be manufactured.

In the above embodiment, a rectangular anodic oxide film is formed using a U-shaped anodic oxidation electrode/mask 7 as shown in FIG. It is possible to form a shaped anodic oxide film. Also, by making the U-shaped tip longer or using a comb-shaped anodic oxidation electrode and mask 7,
By sandwiching a plurality of wafers between the anodic oxidation electrode/mask 7 and the lower electrode 11, a plurality of wafers can be anodized at once.

〔Effect of the invention〕

As explained above, this invention uses an anodic oxidation electrode and mask to form the first protective film, so it has the excellent effect of eliminating contamination of the protective film by resist etc. and improving the yield and characteristics of the device. .

[Brief explanation of drawings]

FIG. 1 is a plan view illustrating an anodic oxidation electrode/mask showing an embodiment of the present invention, FIG. 2 is a cross-sectional view taken from FIG. 1, and FIG. 3 is a method for forming a first protective film of the present invention. FIG. 4 is a cross-sectional view of a conventional infrared sensing element,
FIG. 5 is a plan view of FIG. 4. In the figure, 1 is a high-resistance substrate, 2 is a compound semiconductor, 3 is a light-receiving surface, 4 is a first protective film, and 5 is a second protective film.
6 is an electrode, 7 is an anodic oxidation electrode/mask, 8 is a thin plate of quartz glass, and 9 is a metal vapor deposition film. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A step of forming a compound semiconductor layer on which an infrared sensing element is formed on a high-resistance substrate, and an insulator on one side and a part or all of the other side on the surface of the compound semiconductor layer other than the light-receiving area. Pressing the other side of the anodic oxidation electrode/mask having a desired shape made of metal, and plasma anodizing the surface of the light-receiving region of the compound semiconductor layer to form a first protective film; a step of forming a second protective film on the first protective film so as to cover it; and a step of forming an electrode on the second protective film except for a portion corresponding to the first protective film. A method for manufacturing an infrared sensing element, comprising: