JPH03108371A - Manufacture of infrared ray detecting element - Google Patents

Abstract

PURPOSE:To prevent the generation of crosstalk by forming a metallic film between PN junction areas which constitute infrared ray detecting elements, and heat-treating this metallic film so as to introduce metallic atoms between the PN junction areas. CONSTITUTION:An epitaxial layer 11 of Hg1-xCdxTe is formed on a CdZnTe substrate 15. Next, a resist film 16 of a specified pattern is formed on the layer 11, and with this as a mask, an N-type layer 17 is formed to form a PN junction area 12, and this is made infrared ray detecting element 13. Next, a resist film 18 is formed on this infrared ray detecting element, and then with this film 18 as a mask, a metallic film 14 is formed. Next, the film 18 and the film 14 thereon are removed, and the film 14 between the infrared ray detecting elements is made a contact electrode of the substrate 15. Next, the film 14 is annealed by laser. As a result, the metallic atoms of the film 14 are introduced into the substrate 15, and carrier concentration increases, whereby the lives of a small number of carriers are shortened, and the carriers generated between the detecting elements vanish, so the generation of cross talk decreases.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for manufacturing a multi-element type infrared sensing element, the objective is to produce a multi-element type photovoltaic type infrared sensing element that does not generate crosstalk, and a compound semiconductor crystal containing mercury is used. After forming a P-N junction region at a predetermined interval in the crystal by introducing an impurity of a conductivity type opposite to that of the crystal, or before forming the P-N junction, the P-N junction region of the substrate is The method includes the steps of depositing a metal film between the bonding regions, heat-treating the metal film, and introducing metal atoms of the metal film between the P-N bonding regions.

[Industrial application field]

The present invention relates to a method for manufacturing a multi-element photovoltaic infrared sensing element.

Impurity atoms of the opposite conductivity type to the crystal are introduced into a P-type compound semiconductor crystal made of mercury, cadmium, and tellurium (HgI-*Cdx Te), which has a narrow energy band gap, to create a P-N junction in a predetermined region. A multi-element type photovoltaic infrared sensing element provided with a large number of infrared rays is well known.

In such a multi-element type infrared sensing element, in order to increase the sensitivity and resolution of the sensing element, the pitch between the sensing elements formed in the compound semiconductor crystal is made as narrow as possible to increase the density of the sensing elements. It is desired that the system be installed in

[Conventional technology]

Conventionally, as shown in FIG. 2, a method for manufacturing such a multi-element type infrared sensing element is to use P-type (Igt-x) which is formed by liquid phase epitaxial growth on a CdTe substrate.
Poron (B) atoms are ion-implanted into the Cdz Te epitaxial layer 2 to form an N-type layer 3, a PN junction 4 is formed, and an infrared sensing element 5 is formed, and a large number of these infrared sensing elements are arranged. A multi-element photovoltaic infrared sensing element was formed.

In order to increase the sensitivity and resolution of such an infrared sensing element, it is necessary to arrange the infrared sensing elements as densely as possible.

However, as shown in FIG. 3, the distance l between the sensing elements is shorter than the diffusion length of carriers 6 generated by photoelectric conversion of light incident from the back side of CdTe substrate 1 along the six directions of arrows. When the infrared sensing elements 5A, 5B are formed in a compound semiconductor crystal with high density, the infrared sensing elements 5A, 5
The carrier 6 generated between the adjacent detection elements 5A and 5
B, a crosstalk phenomenon occurs in the signal obtained by the detection element, and the spatial resolution of the detection element decreases, resulting in a problem that a high-resolution infrared image cannot be obtained.

In order to solve such problems, the present applicant has proposed H.
g (Mercury) Highly concentrated P type with vacancies as acceptors
g+-x Cdx Te substrate 7 in a predetermined pattern l1
A P-type island region 8 is formed by selectively diffusing g to fill the 11g vacancies, and an N-type layer 9 is formed in this P-type island region.
A diode is formed by forming a diode, and this is used as a pixel of P"HgI-++Cd, in which the Hg is not diffused.
A multi-element photovoltaic infrared sensing element was formed with the Te substrate region serving as a channel stop.

[Problem to be solved by the invention]

However, in this method, since H is an atom with a large diffusion constant, the Hg atom is converted to P″Hfh□CdX T
In order to accurately diffuse Hg atoms into a predetermined concentration and a predetermined area on the e-substrate 7, temperature, time, etc. must be strictly controlled, and Hg atoms are diffused onto the P'' Hgr-x Cdx Te substrate at a predetermined concentration. Therefore, there is a disadvantage that island-like regions of P-type HgI-x Cdz Ti3 crystals having the desired concentration cannot be formed.

The present invention solves the above-mentioned problems and is a multi-element type photovoltaic device in which a channel stop can be easily formed between the above-mentioned infrared sensing elements and crosstalk phenomenon does not occur in the signals obtained by the sensing elements. The purpose of this invention is to provide a method for manufacturing a type of infrared sensing element.

[Means to solve the problem]

As shown in FIG. 1(a) to FIG. 1(C), the method for manufacturing an infrared sensing element of the present invention to achieve the above object is to provide a compound semiconductor crystal 11 containing mercury with a conductivity opposite to that of the crystal. After forming the infrared sensing element 13 by introducing a type of impurity and forming the P-N junction regions 12 at predetermined intervals, or before forming the P-N junction regions 12,
After forming the metal film 14 between the bonding regions 12, heat-treating the metal film 14 to introduce metal atoms of the metal film between the P-N junction regions formed in the compound semiconductor crystal 11. It is characterized by having

[Function] In general, the lifetime τ of minority carriers formed in a P-type compound semiconductor crystal is the Auger recombination lifetime τ4, the radiative recombination lifetime τ, and the Shockley-Reed recombination lifetime τ3,
If it is shown as Equation (11).

1/τ=1/τ, +1/τ, +1/τ, l...
......(1) τ* (no + po+ n
e) Publication (2) However, no represents the electron concentration, po represents the hole concentration, and no represents the minority carrier concentration. Further, τ can be expressed by equation (3).

τ^ ((po+n5)(no+po+n,))
−' −・・・・・・・・・(3) Moreover, τ311 can be expressed by equation (4).

τsyr po−'・・・・・・・・・(4)th (1st
As shown in equations 1 to (4), the minority carrier lifetime becomes shorter as the carrier concentration increases.

In other words, in equations (2), (3), and (4), when the carrier concentration of the genuine tag increases, equation (2) becomes (no +
po + n m ) Equation (3) is ((po + n e
)(no + po+ nm)), since equation (4) is inversely proportional to po, τ1, τ8, τ, ll
becomes smaller. Therefore, the minority carrier lifetime τ also becomes smaller than the il1 equation.

In 11g1□Cd, Te crystals, metal atoms such as gold, silver, and copper are atoms that increase the hole concentration.If four of these atoms are placed between the sensing elements, the lifetime of minority carriers will be shortened. Since the lifetime of the holes of minority carriers formed in the compound semiconductor crystal through photoelectric conversion between the sensing elements is shortened, these minority carriers no longer reach adjacent sensing elements, and therefore the occurrence of crosstalk is reduced.

Then, the metal atoms to be introduced into this compound semiconductor crystal are formed by depositing a metal film between the sensing elements as a contact electrode of the sensing element, and when this metal film is laser annealed, the metal atoms in the metal film easily form a compound. When introduced into the semiconductor crystal, it becomes a recombination center for minority carriers, A, and the minority carriers are captured at this recombination center and easily disappear.

〔Example〕

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

As shown in FIG.
P with a carrier concentration of l xlOI6/cm”
An epitaxial layer 11 of type Hg+-, 1CdxTe (x = 0.22) is formed by a liquid phase epitaxial growth method.

Next, a resist film 16 with a predetermined pattern is formed on the P-type Hg+-x Cdx Te epitaxial layer 11,
By using the resist film 16 as a mask, B is
``Atomic ion implantation is performed to form an N-type layer 17 to form a PN junction region 12, and an infrared sensing element 13 is formed.

Next, as shown in FIG. 1(b), a resist film 18 is formed on the infrared sensing element, and then a metal film 14 of gold, silver, or copper is formed by vapor deposition using the resist film 18 as a mask.

Next, as shown in FIG. 1(C), the resist film 18 of FIG. 1(b) is removed and the metal film 14 thereon is removed.
is also removed, and a metal film 14 is formed between the infrared sensing elements 13 as a contact electrode of the substrate.

Next, although not shown in the figure, an argon (^r) ion laser beam with a wavelength of 488 nm and an output of 1 W was focused into a light beam with a diameter of 5 μ-, and was applied onto the metal Hg 14 at a scanning speed of 10/min. is scanned, and the metal film 14 deposited by the vapor deposition is laser annealed. Thereafter, although not shown, a connection electrode made of indium (In) for making contact with a signal processing element such as a charge transfer element is formed by vapor deposition on the infrared sensing element 13 to form a multi-element type infrared sensing element. .

In this way, the metal atoms in the metal film 14 are introduced into the compound semiconductor substrate by laser annealing, and the carrier concentration increases, which shortens the life of minority carriers, and the carriers generated between the sensing elements disappear. Therefore, a sensing element with less occurrence of crosstalk can be obtained.

Note that Hg1-x C before forming the P-N junction 12
A PN junction may be formed after forming a contact electrode on a dXTe crystal and adding metal atoms by laser annealing.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, carriers generated between sensing elements are easily annihilated, so that a high-resolution multi-element infrared sensing element that does not cause crosstalk can be obtained.

[Brief explanation of drawings]

Figure 1 (up to C1 is a cross-sectional view showing the manufacturing process of the infrared sensing element of the present invention, Figure 2 is a cross-sectional view of a conventional infrared sensing element, and Figure 3 is a cross-sectional view of a conventional infrared sensing element. Fig. 4 is a cross-sectional view showing the conventional manufacturing method of an infrared sensing element. In the figure, 11 is a compound semiconductor crystal (P-type Hg+-x Cdx T
12 is a P-N junction region, 13 is an infrared sensing element, 14 is a metal film, 15 is a CdZnTe substrate, 16.18 is a resist film, and 17 is an N-type layer. 5iS4 diagram

Claims (3)

[Claims] (1) After introducing an impurity of a conductivity type opposite to that of the crystal into a compound semiconductor crystal (11) containing mercury to form P-N junction regions (12) at a predetermined interval in the crystal, P
- Infrared rays characterized by comprising a step of depositing and forming a metal film (14) between the N junction regions, heat-treating the metal film and introducing metal atoms of the metal film between the P-N junction regions. Method of manufacturing a sensing element. (2) Before forming the P-N junction region (12),
The metal film (14
), and heat-treating the metal film to introduce metal atoms of the metal film between the planned P-N junction regions. Production method. (3) The method further comprises a step of laser annealing the metal film to introduce metal atoms of the metal film between P-N junction regions formed in the compound semiconductor crystal. 2) The method for manufacturing an infrared sensing element according to item 2).