JP2830285B2 - Method for manufacturing photodetector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a method for manufacturing a multi-element photodetector, which is intended to be a multi-element photodetector which is surely separated and has a high density, and is formed on a substrate. A groove for element isolation reaching the substrate surface is formed in the P-type compound semiconductor crystal containing mercury by ion milling, and the substrate containing the compound semiconductor crystal is heated in an atmosphere of mercury vapor, After the side wall region of the groove converted into the N-type region due to the damage of the ion milling is restored to the P-type region and the compound semiconductor crystal is converted into a P-type crystal having a predetermined carrier concentration, the compound semiconductor crystal separated by the groove is removed. A plurality of photodetection PN junction elements are formed by selectively introducing element-forming impurities into each predetermined region to form a plurality of photodetection PN junction elements.

[Industrial applications]

The present invention relates to a method for manufacturing a light sensing element, and more particularly to a method for manufacturing a multi-element type light sensing element in which the area of an element isolation region is reduced and arranged at high density.

Infrared detectors such as photo detectors are made of mercury, cadmium, tellurium (Hg _1-x C
d _x Te) is used as a device forming material, and these devices are used for high resolution.
It is desired to arrange them on the crystal substrate as densely as possible.

By the way, when a large number of the sensing elements are arranged on a crystal substrate, if the distance between the elements is shorter than the diffusion length of carriers photoelectrically converted by the crystal substrate, crosstalk may occur in a signal obtained by the sensing element. Therefore, a detection element that prevents the occurrence of the crosstalk is desired.

[Conventional technology]

Heretofore, the present applicant has previously disclosed in Japanese Patent Application No. 61-281341 a light-sensing element that prevented the occurrence of such crosstalk by diffusing mercury into a predetermined region of a P ⁺ type Hg _1-x Cd _x Te crystal. To fill the vacancies of the P ⁺ type Hg _1-x Cd _x Te crystal to form a P type crystal,
An element is formed on the P-type crystal to form a P ⁺
A device using a type Hg _1-x Cd _x Te crystal as a device isolation region has been proposed.

Also, the applicant of the present invention has disclosed in Japanese Patent Application No. 61-187508 a method of selectively forming a high x-value Hg _1-x Cd _x Te crystal in a predetermined region of a CdTe substrate, and forming a high-value Hg _1-x Cd _x Te crystal thereon. to form Hg _1-x Cd _x Te crystal x values, it has proposed a device in which the Hg _1-x Cd _x Te crystal element isolation region of the high x values.

In addition to such an element separation method, as an easier manufacturing method, etching is performed between element forming regions of Hg _1-x Cd _x Te crystals for element formation formed on a CdTe substrate until reaching the CdTe substrate. There is a method in which a groove is provided to separate elements.

Conventionally, as a method of forming such a groove, a resist film is formed in a predetermined region on a Hg _1-x Cd _x Te crystal formed on a CdTe substrate, and then a bromo (B)
a method of etching until reaching the CdTe substrate with r ₂₎ and consisting of a mixture of methanol (CH ₃ OH) etchant.

However, in the etching method using this liquid, the etching direction is isotropic, and it is difficult to form a groove having a large aspect ratio (groove depth dimension / groove width dimension). The area becomes large, the number of sensing elements to be arranged on one substrate decreases, and there is a problem that elements cannot be arranged at high density.

As a method of forming such a high aspect ratio groove, an ion milling method using an argon gas has been conventionally proposed.

[Problems to be solved by the invention]

However, according to JP-A-57-170577, as shown in FIG. 3, when the Hg _1-x Cd _x Te crystal 2 formed on the CdTe substrate 1 is etched by such an ion milling method, the grooves 3 are formed. And the area around the groove is damaged by ion bombardment during ion milling, and Hg becomes Hg higher than the damaged area.
_The interstitial impurities are introduced into the _1-x Cd _x Te crystal, and the Hg introduced into the interstitial becomes an N-type impurity to form the N ⁺ layer 4.

As described above, when the N ⁺ layer 4 is formed in the groove 3 and the region around the groove, the N-type layer 6 is formed by ion-implanting N-type impurities into the element forming region 5 defined by the groove. There is a problem that the N-type layer 6 and the N ⁺ layer 4 formed at the time of the ion milling come into contact with each other, and the groove does not perform the function of element isolation.

The present invention eliminates the above-described problems, and even if a groove having a high aspect ratio is formed by an ion milling method, the N ⁺ layer is not formed in the groove, and in the region around the groove, and the element can be formed at a high density. It is an object of the present invention to provide a method for manufacturing a light sensing element that can be arranged.

[Means for solving the problem]

In order to achieve the above object, a method for manufacturing a photodetector of the present invention includes forming a groove for element isolation reaching the substrate surface by ion milling in a P-type compound semiconductor crystal containing mercury formed on a substrate, The substrate including the compound semiconductor crystal is subjected to a heat treatment in an atmosphere of mercury vapor to restore the side wall region of the groove converted into the N-type region to the P-type region due to the damage of the ion milling, and to convert the compound semiconductor crystal to a predetermined shape. And then selectively introducing element forming impurities into a predetermined region of each compound semiconductor crystal separated by the trench to separate a large number of photodetecting PNs.
It is characterized in that a junction element is formed.

(Operation)

Due to the damage of the P ⁺ type Hg _1-x Cd _x Te crystal during ion milling, the groove and the periphery of the groove are converted to an N ⁺ layer because Hg is Hg _1-x Hg that has entered the interstitial region becomes an N-type impurity and forms an N ⁺ layer because the interstitial impurity of the Cd _x Te crystal intrudes.

When a substrate having a Hg _1-x Cd _x Te crystal that is damaged in the groove and the area around the groove by such ion milling is heated in mercury vapor, Hg between the lattices diffuses during the heating. and evaporated from Hg _1-x Cd _x Te crystal surface by the N ⁺
The groove converted into the layer and the area around the groove are restored to the P-type layer.

On the other hand, Hg vacancies are formed in the P ⁺ type Hg _1-x Cd _x Te crystal in the region other than the region around the groove, and these Hg vacancies become impurities of the acceptor. Hg by heating
By filling the vacancies and controlling the concentration of Hg vacancies to form a P-type layer having a predetermined acceptor concentration, the groove and the area surrounding the groove are converted to a P-type layer, and the damaged portion is restored to the P-type layer. Thus, a groove having a high aspect ratio is formed.

Then, when an N-type impurity is introduced into the element formation region defined by the groove, a multi-element type photodetector arranged at high density can be obtained.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1 (a), a 15 μm thick
Pg type Hg _1-x Cd _x with a carrier concentration of about 1 × 10 ¹⁷ / cm ³
A Te crystal 12 is formed by a liquid phase epitaxial growth method.

Next, a positive type resist film 13 is formed in a predetermined pattern on the substrate, and the resist film 13 is etched by an ion milling method using an argon gas using the mask as a mask, and has a depth of 15 μm, a width of 10 μm, and a high aspect ratio. A groove 14 is formed.

Next, when the resist film is removed, a state as shown in FIG. 1B is obtained.

Next, as shown in FIG. 2, a CdTe substrate 11 having the groove formed therein in an ampoule 15 and mercury 17 contained in a mercury containing container 16 are sealed, and the ampoule is placed in a heating furnace 18 at a temperature of 440 ° C. After heating for 48 hours, the ampoule is taken out of the heating furnace, put into water and rapidly cooled.

The reason why the substrate is rapidly cooled in this way is to suppress the diffusion amount of mercury to a predetermined value and to fix the carrier concentration to a predetermined value.

In this way, the Hg _1-x Cd _x Te crystal has a carrier concentration of 2
It becomes a P-type crystal of × 10 ¹⁶ / cm ³ , and N ⁺
The groove converted into the layer and the region surrounding the groove also recover to the P-type layer.

Next, as shown in FIG. 1C, boron (B ⁺ ) ions are ion-implanted into the element forming region 19 defined by the groove 14 to form an N-type layer 21 to form a PN junction. To form a light detecting element.

In this manner, a multi-element photodetector element which is element-separated by grooves having a high aspect ratio and arranged at high density can be obtained.

〔The invention's effect〕

As is clear from the above description, according to the present invention, there is an effect that a multi-element photodetector arranged at high density and free from crosstalk can be obtained.

[Brief description of the drawings]

1 (a) to 1 (c) are cross-sectional views showing the method of the present invention, FIG. 2 is an explanatory view of the method of the present invention, and FIG. 3 is a disadvantage of an element formed by a conventional method. It is sectional drawing which shows a proper state. In the figure, 11 is a CdTe substrate, 12 is a P-type Hg _1-x Cd _x Te crystal, 13 is a resist film, 14 is a groove, 15 is an ampoule, 16 is a mercury container, 17 is mercury, 18 is a heating furnace, 19 Denotes an element formation region, and 21 denotes an N-type layer.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) H01L 27/14 H01L 21/477 H01L 31/0264

Claims (1)

(57) [Claims] An element-isolating groove reaching the substrate surface is formed in a P-type compound semiconductor crystal containing mercury formed on a substrate by an ion milling method. After performing heat treatment in an atmosphere to recover the side wall region of the trench converted into the N-type region due to the damage of the ion milling into a P-type region, the compound semiconductor crystal becomes a P-type crystal having a predetermined carrier concentration. Photodetection characterized by selectively introducing element-forming impurities into a predetermined region of each compound semiconductor crystal separated by the groove to form a large number of photodetection PN junction elements, each of which is element-isolated. Device manufacturing method.