JPH09286699A - Production of mercury cadmium telluride crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the crystal in which crystal defects due to oxide, such as surface pits or p<+> defects are remarkably reduced by performing crystal growth of a HgCdTe crystal in a specific gas atmosphere. SOLUTION: In this production, crystal growth of a HgCdTe crystal is performed in an atmosphere 18 of hydrogen with which the inside of a closed tube 11 is filled so that the pressure inside the closed tube 11 is >=0.6atm, preferably 0.8 to 1.0atm expressed in terms of pressure at ordinary temp. As a result, oxygen or oxide remaining in the closed tube 11 is effectively reduced to prevent a growing layer from being contaminated by oxygen and to reduce the generation of p<+> defects due to oxide to a <=1cm<-2> defect density that is equivalent to <=1/10 of the density of a conventional HgCdTe crystal. Preferably, the internal volume of a connection 16 of a hydrogen filling device for filling the inside of the closed tube 11 with hydrogen, that is used for connecting the device to the closed tube 11, is adjusted to a volume larger than the internal volume of the closed tube 11 to suppress the change in pressure inside the tube 11 due to the heat generated at the time of sealing the closed tube 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a HgCdTe crystal, and particularly to HgC in which crystal defects such as surface pits and p ⁺ defects caused by an oxide are reduced.
The present invention relates to a method of manufacturing a dTe crystal.

[0002]

2. Description of the Related Art Conventionally, as an infrared detecting element for detecting infrared rays in the vicinity of 10 μm band, Hg having a Cd ratio of about 0.2 is used.
Although a pn junction diode using CdTe is used, a crystal growth technique with easy control of carrier concentration and low defects is required for manufacturing a high-performance infrared detection element.

Conventionally, in order to meet such a demand, a crystal growth jig containing a crystal growth substrate and a growth melt is inserted into a quartz ampoule, and the interior of the ampoule is evacuated to a vacuum. Fill with 2 atmospheres of hydrogen, then
After the ampoule was sealed, it was placed in a heat treatment furnace for crystal growth (if necessary, see, for example, JP-A-60-2046).
No. 99).

As described above, by filling hydrogen into the ampoule during crystal growth, oxygen remaining in the ampoule is reduced, and defects such as surface pits resulting from the incorporation of oxygen into the growth layer and oxide formation. Generation was suppressed and the carrier concentration was controlled to a low concentration of about 1 × 10 ¹⁴ cm ⁻³ .

Although the above-mentioned reference describes that the filling pressure of hydrogen is about 0.5 atm (0.5 kg / cm ² ) at room temperature, in reality, as described above, Since 0.2 atm is sufficient, the crystal was grown at 0.2 atm.

[0006]

However, 0.2 atm,
Alternatively, filling of 0.5 atm of hydrogen was effective for controlling carrier concentration and suppressing surface pits, but was insufficient for suppressing p ⁺ defects, which is one of the pixel defect factors of infrared detection elements. LBIC (Laser Beam)
It became clear by the crystal evaluation by the Induced Current.

This p⁺The defects are p existing in the p-type crystal.
⁺Type region and is believed to be due to dislocation clusters
However, in the conventional 0.2 atm hydrogen filling,
P ⁺Defect density is 12 to 13 cm^-2And is a practical problem
was there.

Therefore, it is an object of the present invention to provide a method of reducing p ⁺ defects in HgCdTe growth layers.

[0009]

FIG. 1 is an explanatory view of the principle configuration of the present invention, and means for solving the problems in the present invention will be described with reference to FIG. See FIG. 1 (1) In the method for producing a HgCdTe crystal, the present invention is characterized in that crystal growth is performed in a hydrogen atmosphere 5 in which hydrogen is filled in a closed tube 1 at a pressure of 0.6 atm or more at room temperature.

As described above, by performing crystal growth in the hydrogen atmosphere 5 in which hydrogen is filled into the closed tube 1 at a pressure of 0.6 atm or more at room temperature, oxygen or oxide remaining in the closed tube 1 can be effectively removed. Reduction of oxygen prevents oxygen from being taken into the growth layer, and reduces generation of p ⁺ defects due to oxides to 1/10 of the conventional level
It can be reduced to ~ 1 cm ^-2 below.

(2) Further, according to the present invention, in the above (1), the internal volume of the connecting portion of the hydrogen filling device for filling the closed tube 1 with the closed tube 1 is made larger than the internal volume of the closed tube 1. It is characterized by

In this way, by making the internal volume of the connecting portion of the hydrogen filling device with the closed tube 1 larger than the internal volume of the closed tube 1, it is possible to suppress the pressure change in the closed tube 1 due to heat at the time of sealing. You can

(3) Further, according to the present invention, in the above (1) or (2), when the closed tube 1 is sealed, the closed tube 1 other than the sealing portion 7 and the closed tube 1 of the hydrogen filling device are provided. It is characterized in that the connection part is cooled.

In this way, except for the sealing portion 7 of the closed tube 1, and
By cooling the connection portion of the hydrogen filling device with the closed pipe 1, it is possible to suppress the pressure change in the closed pipe 1 due to heat at the time of sealing, and in particular, by cooling the connection portion made of metal, the O-ring Can be prevented from melting.

(4) Further, according to the present invention, in any one of the above (1) to (3), when the closed tube 1 is sealed, a hydrogen filling gap is left below 0.6 atm at room temperature. After temporary sealing, the hydrogen pressure is raised to perform final sealing.

By thus performing the two-stage sealing,
Since the time of final sealing can be shortened, the pressure change in the closed tube 1 due to the heat at the time of sealing can be suppressed more effectively.

(5) Furthermore, the present invention is characterized in that in any one of the above (1) to (4), the inner wall of the closed tube 1 and at least a part of the crystal growth jig 2 are coated with carbon. To do.

The closed tube 1 and the crystal growth jig 2 are made of quartz, and the quartz and the oxide of Cd easily react with each other. Therefore, at least a part of the inner wall of the closed tube 1 and the crystal growth jig 2 is formed. By coating carbon with carbon, the oxygen reduction effect is enhanced, and the generation of p ⁺ defects can be suppressed.

(6) Further, the present invention is characterized in that, in the above (5), a carbon coating is applied to a contact portion with the melt 4 for crystal growth.

Such a carbon coating may be applied at least to the contact portion with the melt 4 for crystal growth, and the closed tube 1
It is not necessary to coat the entire surface of the crystal growth jig 2 with carbon.

(7) Further, in the present invention according to any one of the above (1) to (6), an alloy for crystal growth melt having a predetermined composition as a material for melt for crystal growth prior to crystal growth. Is used.

In the crystal growth step, it takes time to start crystal growth after melting the various crystal growth melt materials and stabilizing the crystal growth melt 4, and during that time, Cd
Since the crystal growth substrate 3 such as a Te substrate may be thermally damaged, it is possible to shorten the formation time of the crystal growth melt 4 by using a crystal growth melt alloy having a predetermined composition in advance. Damage to the crystal growth substrate 3 can be reduced.

(8) Further, in the present invention according to the above (7), when the alloy for crystal growth melt is formed by using a melt producing jig consisting of a carbon coated portion and a carbon uncoated portion, Characterized by melting the raw material for crystal growth melt in the carbon coating part in a closed tube filled with hydrogen at 0.6 atm at room temperature or higher, and then transferring and solidifying the melt to the carbon non-coating part .

As described above, even when the alloy for crystal growth melt is formed, in a hydrogen atmosphere of 0.6 atm or more in terms of room temperature so that oxygen is not taken into the alloy for crystal growth melt as much as possible. It is important to do this, and the melt preparation jig is composed of a carbon coating part and a carbon non-coating part, and the oxygen reduction effect is enhanced by melting the raw material for crystal growth melt in the carbon coating part, and The alloy for crystal growth melt can be prevented from sticking to the carbon-coated portion by transferring and solidifying the melt to the carbon-uncoated portion.

[0025]

FIG. 2 shows a first embodiment of the present invention.
This will be described with reference to FIG. See FIG. 2 (a). First, CdTe is placed in a quartz crystal growth ampoule 11.
The crystal growth jig 12 accommodating the substrate 13 and the HgCdTe melt alloy 14 is inserted, then the inner tube 15 for ampoule sealing is inserted into the open end of the crystal growth ampoule 11, and the open end is connected to a vacuum exhaust device. The ampoule connection part 16 of the double hydrogen filling device is attached airtightly via an O-ring.

In this case, it is important that the internal volume of the ampoule connection portion 16 of the hydrogen filling device is sufficiently larger than the internal volume of the crystal growth ampoule 11 in order to suppress the pressure change during sealing. is there.

Further, in this case, the alloy 14 for HgCdTe melt has a composition ratio of Hg, Cd and Te of H in terms of molar ratio.
The composition was previously melted and solidified so that g: Cd: Te = 20: 1: 79.
It is appropriately changed according to the composition ratio of the gCdTe crystal.

Then, the inside of the crystal growth ampoule 11 is sufficiently evacuated by a hydrogen filling device which also serves as a vacuum exhaust device, and then hydrogen is fed into the inside of the crystal growth ampoule 11 from the hydrogen filling device to 0.6 atmospheric pressure or less. , For example,
By heating the ampoule sealing portion 17 with a burner in a state of 0.4 atm, a gap 19 for hydrogen filling is left between the ampoule sealing inner tube 15 and the crystal growth ampoule 11. Temporarily seal.

Next, referring to FIG. 2 (b), hydrogen is further fed into the crystal growth ampoule 11 from the hydrogen filling device, and when it reaches 0.6 atm or more, for example, 0.8 atm at room temperature, Final sealing is performed by heating the ampoule sealing portion 17 again using a burner.

In the steps of temporary sealing and final sealing, a portion other than the ampoule sealing portion 17 of the crystal growth ampoule 11 is prevented so that the pressure inside the crystal growth ampoule 11 due to the heat of the burner does not rise. Also, it is desirable to cool the ampoule connection portion 16 of the hydrogen filling device, and by cooling, it is possible to prevent melting of the O-ring in the ampoule connection portion 16 of the hydrogen filling device.

As a cooling means in this case, a method of winding a cloth containing water around the ampoule sealing part 17 of the crystal growth ampoule 11 and the ampoule connection part 16 of the hydrogen filling device is simple. However, it may be cooled by blowing liquid nitrogen.

Next, although not shown, the sealed crystal-growing ampoule 11 is removed from the hydrogen filling device, inserted into a heat treatment furnace, heated to 500 ° C., and then cooled to 0.1 ° C./min. By cooling with C
An HgCdTe crystal is epitaxially grown on the dTe substrate 13.

See FIG. 3. FIG. 3 is a diagram showing the hydrogen filling pressure dependency of p ⁺ defects in the grown HgCdTe crystal, which was 12 to 13 cm ⁻² at 0.2 to 0.4 atm. ⁺ Defects are reduced to about 1 cm ^-2 by setting the hydrogen filling pressure to 0.6 or more,
Even if an infrared detecting element is constructed using such HgCdTe crystal, pixel defects hardly occur.

In this case, the hydrogen filling pressure may be 0.6 atm or more, but it is more preferably 0.8 atm or more, and such sealing is usually performed under normal pressure. Therefore, when the internal pressure of the crystal growth ampoule 11 becomes 1 atm or more, the ampoule sealing portion 17 softened by heating expands to the outside and sealing cannot be performed. Therefore, the hydrogen filling pressure needs to be 1 atm or less. is there.

Further, in the first embodiment,
The generation of crystal defects such as surface pits can be sufficiently suppressed as in the conventional case, and the controllability of the carrier concentration is almost the same as in the conventional case.

In the first embodiment described above, the time required for final sealing is shortened by performing temporary sealing in advance to suppress the change in pressure.
It is not necessary to perform stepwise sealing, and final sealing may be performed in a state where hydrogen is filled to 0.6 atm or more from the beginning.

Further, in the above-mentioned first embodiment, the usual quartz-made crystal-growing ampoule 11 and crystal-growing jig 12 are used. However, quartz easily reacts with the oxide of Cd, and oxygen Since the effect of (3) tends to remain, the quartz surface may be coated with carbon having a thickness of 100 to 500 nm to enhance the oxygen reduction effect by hydrogen.

In this case, it is not always necessary to coat the entire surfaces of the crystal-growing ampoule 11 and the crystal-growing jig 12 with carbon, and only the portion in contact with the crystal-growing melt is coated with carbon. Is also good.

Next, with reference to FIG. 4, a second embodiment of the method for producing the alloy for HgCdTe melt used in the first embodiment will be described. See FIG. 4 (a). First, in an ampoule 21 for producing a melt for growth made of quartz,
Melt producing raw material 25, for example, Hg: Cd: T in a molar ratio
After inserting the melt producing jig 22 containing Hg, Cd, and Te, in which e = 20: 1: 79, the melt for producing was prepared using the hydrogen filling device as in the first embodiment. The ampoule 21 for sealing is sealed in a state where the hydrogen pressure in the ampoule 21 is 0.6 atmospheric pressure or more, for example, 0.8 atmospheric pressure.

The sealing method may be two-step sealing as in the first embodiment or one-step sealing, and the ampoule 21 for the growth melt making ampoule 21 may be used. It may be performed while cooling the ampoule connection part (not shown) of the hydrogen filling device other than the sealing part 27.

Further, the melt producing jig 22 in this case is composed of an uncoated carbon portion 23 and a carbon coating portion 24, and can be divided into upper and lower parts. In the initial stage, the carbon coating portion 24 is at the bottom. To arrange.

Then, the ampoule 21 for producing the melt for growth is inserted into a heat treatment furnace and heated at 600 to 700 ° C. for 8 to 10 hours to uniformly melt the HgCdTe melt 29.
To form

Next, when cooling, the melt-making jig 22 is turned upside down, the HgCdTe melt 29 is transferred to the carbon-uncoated portion 23, and then solidified to obtain the HgCdTe melt alloy 30. Form.

Also in this case, since the heat treatment is carried out in a hydrogen atmosphere of 0.6 atm at room temperature, oxygen remaining in the growth melt making ampoule 21 can be reduced.
Oxygen or oxide is not taken into the HgCdTe melt alloy 30. By using this HgCdTe melt alloy 30 to perform crystal growth as in the first embodiment, oxygen-induced p ⁺ Defects can be suppressed more effectively.

In the form of this second embodiment,
The alloy for HgCdTe melt 3 which prevents reaction with oxygen when HgCdTe melt 29 is melted and which is solidified during solidification
In order to prevent sticking / adhesion to the melt production jig 22 of No. 0, the melt production jig 22 composed of the uncoated carbon portion 23 and the carbon coating portion 24 is used. It is not limited to this, and a melt producing jig consisting only of an uncoated portion of carbon or a melt producing jig consisting of only a carbon coating portion may be used. No need to flip.

In the first embodiment described above, by using a preformed alloy for HgCdTe melt, the melt formation time is shortened and the thermal damage to the CdTe substrate is reduced. , Hg
It is not necessary to use an alloy for CdTe melting, and Hg, Cd, and Te in a predetermined molar ratio may be directly put in the crystal growth jig.

[0047]

According to the present invention, since HgCdTe crystals are grown in a hydrogen atmosphere of 0.6 atm at room temperature, high quality HgCdT with few p ⁺ defects due to oxygen is grown.
e crystal can be obtained, the quality of the infrared detection element can be improved,
Alternatively, it greatly contributes to the improvement of manufacturing yield.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a principle configuration of the present invention.

FIG. 2 is an explanatory diagram of the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of dependency of p ⁺ defect density and hydrogen filling pressure.

FIG. 4 is an explanatory diagram of a second embodiment of the present invention.

[Explanation of symbols]

 1 Closed Tube 2 Jig 3 Crystal Growth Substrate 4 Growth Melt 5 Hydrogen Atmosphere 6 Sealing Inner Tube 7 Sealing Part 11 Crystal Growth Ampoule 12 Crystal Growth Jig 13 CdTe Substrate 14 HgCdTe Melt Alloy 15 Ampule Sealing Inner pipe 16 Ampoule connection part of hydrogen filling device 17 Ampoule sealing part 18 Hydrogen 19 Gap 21 Melt making ampoule for growth 22 Melt making jig 23 Carbon uncoated part 24 Carbon coating part 25 Melt making raw material 26 Inside ampoule sealing Tube 27 Ampoule sealing part 28 Hydrogen 29 HgCdTe melt 30 HgCdTe melt alloy

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kosaku Yamamoto 4-1-1 Kamikodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited (72) Inventor Koji Ebe, 4 Ueoda-chu, Nakahara-ku, Kawasaki, Kanagawa Chome 1-1 No. 1 within Fujitsu Limited

Claims (8)

[Claims] 1. A method for producing an HgCdTe crystal, which comprises performing crystal growth in a hydrogen atmosphere in which hydrogen is filled into a closed tube at a pressure equal to or higher than 0.6 atm at room temperature. 2. The Hg according to claim 1, wherein an internal volume of a connecting portion of the hydrogen filling device for filling hydrogen into the closed tube with the closed tube is larger than an internal volume of the closed tube.
Method for producing CdTe crystal. 3. The method according to claim 1, wherein, when the closed pipe is sealed, a portion other than the sealed portion of the closed pipe and a connection portion of the hydrogen filling device with the closed pipe are cooled. H
Method for producing gCdTe crystal. 4. When the closed tube is sealed, it is temporarily sealed with a hydrogen filling gap of less than 0.6 atm at room temperature, and then the hydrogen pressure is raised to perform final sealing. The method for producing the HgCdTe crystal according to any one of claims 1 to 3. 5. The HgCd according to claim 1, wherein the inner wall of the closed tube and at least a part of the crystal growth jig are coated with carbon.
Method for manufacturing Te crystal. 6. The method for producing an HgCdTe crystal according to claim 5, wherein the carbon coating is applied to a contact portion with the crystal growth melt. 7. An alloy for crystal growth melt having a predetermined composition is used as a material for crystal growth melt prior to the crystal growth, according to any one of claims 1 to 6.
Item 6. A method for producing a HgCdTe crystal according to item. 8. When forming the alloy for crystal growth melt by using a melt producing jig consisting of a carbon coated portion and a carbon uncoated portion, hydrogen is filled to a pressure of 0.6 atm or more in terms of room temperature. The method for producing a HgCdTe crystal according to claim 7, wherein the raw material for crystal growth melt is melted in the carbon coating part in the closed tube, and then the melt is transferred to the carbon non-coating part and solidified. .