JPH08165189A - Production of semiconductor single crystal - Google Patents

Abstract

PURPOSE: To produce the semiconductor single crystal little in crystal defects in a high yield by a lifting method. CONSTITUTION: The method for producing the semiconductor single crystal comprises holding the crystals of a lifting raw material at a high temperature in an atmospheric gas containing impure elements to be added, solidifying the melt, melting the solid, repeating the treatment cycles necessary times, melting the crystals of the raw material, and subsequently growing the semiconductor single crystal by the lifting method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to pulling a semiconductor single crystal by the Czochralski method.

[0002]

2. Description of the Related Art In recent years, the influence of crystal defects on device characteristics has been clarified, and reducing crystal defects has become an important issue. For example, when the dislocation density in the semiconductor single crystal becomes large, the reverse leakage current of the pn junction formed in the crystal increases, which deteriorates the semiconductor device characteristics and adversely affects the reliability. It has been known. Recently, the demand for reduction of dislocations and minute defects in semiconductor single crystals has been increasing with the high integration of semiconductor elements.

Conventionally, as an effective method of reducing crystal defects, there is a method of adding an element which becomes an electrically neutral impurity in the crystal. In this method, impurities to be added and raw materials to be pulled are put in a crucible, and then melted by heating to form a melt, and a single crystal is pulled. For example,
In the InSb crystal, it is effective to add a group V element such as nitrogen, phosphorus or arsenic as InN (indium nitride), InP (indium phosphide) or InAs (indium arsenide) as an impurity.
Has been reported in.

However, this method has the following problems. Since a small amount of the impurity element is added, it is added as a compound such as InN and InAs as described above. At this time, a fine powder (for example, in the case of InN, the particle size of the powder is about 10 μm) is used in order to facilitate melting in the melt and improve the accuracy of weighing. This fine powder is hermetically stored in an ampoule in an inert gas atmosphere, but since the surface area is larger than that of the bulk, a natural oxide film is likely to be formed simultaneously with opening the ampoule. Therefore, after the compound is decomposed in the melt, oxide scum is formed on the surface of the melt.

It is well known that scum on the melt surface has various adverse effects on pulling of a single crystal. For example, it inhibits seeding and crystal growth, and is one of the factors that cause twinning. In the worst case, it may become polycrystalline. Therefore, it is an important issue to remove the scum that hinders pulling.

[0006]

As described above, the method of adding impurities (powder) which becomes electrically neutral in the crystal is an effective method for reducing crystal defects, but In many cases, scum is formed which hinders the pulling of the single crystal, which makes the pulling of the single crystal difficult, resulting in a problem that the ratio of pulling the single crystal, that is, the single crystallization rate is significantly deteriorated. The present invention eliminates the above-mentioned defects, and provides a method for producing a single crystal with few crystal defects with good yield without generating scum.

[0007]

In order to achieve the above object, in the method for producing a semiconductor single crystal of the present invention, a crystal as a pulling source is heated at a high temperature in an atmosphere gas containing an impurity element to be added. By repeating the cycles of melting to solidification and solidification to melting as many times as necessary, the crystal is doped with a desired impurity element at a desired concentration, and then the crystal is melted to pull up a semiconductor single crystal.

[0008]

In the above manufacturing method, since gas doping is performed as a method of adding an impurity element, an oxide film is not formed on the surface of the dopant. As a result, scum of the oxide film does not occur on the melt surface, and the single crystal can be pulled up without being affected by scum. Further, in order to efficiently carry out the doping with a gas, the crystal is held at a temperature higher than the melting point, and the impurity element to be added is doped for the time until the crystal is melted. It is not doped, so the impurity element to be added is doped until the crystal is completely melted). After the crystal is completely melted, the temperature is lowered to below the melting point to solidify the melt surface (the reason is as described above), and then the crystal is again heated to a temperature higher than the melting point and held. A desired impurity concentration can be obtained by repeating the cycle from the melt to the solid and from the solid to the melt a required number of times.

Even if the crystal is held just below the melting point, an effect similar to the method of repeating melting and solidification and solidifying and melting of the present invention can be obtained, but it takes a long time and is not practical.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Although the present invention can be widely applied to the production of semiconductor single crystals by the pulling method, an InSb single crystal which is a III-V compound semiconductor will be described as an embodiment of the present invention with reference to the drawings.

FIG. 1 is a sectional view of the pulling device used in this embodiment. High purity I used for pulling InSb single crystal
Seed crystal 3 in which nSb polycrystal, for example, 700 g, was placed in the quartz crucible 2 in the chamber 1 and cut in the <211> orientation
Is attached to a seed crystal attachment jig 4 and sealed in the chamber 1. Next, the pressure in the sealed chamber 1 is 10 ⁻⁴ Torr.
It is evacuated to r and filled with high-purity N ₂ (nitrogen) gas, and this gas is allowed to flow at a constant flow rate. Then, the heater 5 surrounding the crucible 2 is heated to a temperature higher than the melting point of InSb of 525 ° C., for example, 600 ° C., and held. Until the crystal melts, the InSb polycrystal will be held in the hot N ₂ gas, and N ₂ will effectively react with the InSb polycrystal surface, resulting in N doping. Further, in order to increase the N doping amount, a temperature lower than the melting point, for example, 520 ° C.
Cool down to solidify. Solidification starts from the surface of the melt. Hold for about 30 minutes with the surface of the melt completely solidified. During this time, N is further doped as described above. Next, the crystal is heated again to a temperature higher than the melting point of InSb of 525 ° C., for example, 600 ° C., and the solidified InSb polycrystal is melted again to form the InSb melt 6. On the melt surface 6,
No oxide scum is present because of the attempted gas doping of the present invention. Then, as shown in FIG. 1, for example, the pulling rate is 10 mm / h, the rotation number is 10 rpm, and the pulling rate is 550 ° C. to produce the InSb single crystal 7.

In the present invention, N doping with gas is performed as a method of adding an impurity element. As described above, in order to check whether the gas doping method is effective in reducing the crystal defects, the crystal defect evaluation of the InSb single crystal pulled up by the method of the present invention was performed by the following procedure. This evaluation uses the etching method, and first, <211>
From an InSb single crystal ingot grown in the direction (11
The wafer of (1) plane was cut out, and this (111) In plane was sequentially polished from Al ₂ O ₃ powder having a grain size of 16 μm to 0.05 μm to finish it as a mirror surface. Next, in order to remove polishing scratches, etching was performed at 20 ° C. for 5 minutes using an etching solution having a composition ratio of CH ₃ CH (OH) COOH: HNO ₃ = 6: 1. Subsequently, the composition ratio is 49% HF: 3 for detecting etch pits.
Etching was performed for 1 minute at 20 ° C. using an etching solution of 5% H ₂ O ₂ : H ₂ O = 1: 2: 2.

As a result, D-pits (dislo
Although only cation-pits are slightly present in the facet region (dislocation density is in the order of one digit), S-pits (Saucer-like-pits) corresponding to other microdefects and impurity precipitation in the central part , Or P-pits (punchin) in which S-pits are generated in the [110] direction around this defect.
Various pits such as g-out-pits) were not observed, and it was found that an InSb single crystal with few crystal defects was obtained.

In the above embodiments, the case where the present invention is applied to the InSb single crystal which is a III-V group compound semiconductor has been described, but needless to say, it is not limited to the InSb single crystal and is widely applied to pulling other semiconductor single crystals. It is possible. Further, although the case where nitrogen gas is used as the impurity element has been described in the above-mentioned embodiment, it is not necessary to limit to nitrogen gas, and instead of nitrogen gas, other impurity elements such as phosphorus and arsenic can also be changed to a gas phase state. It is applicable by doing. Nitrogen, phosphorus, arsenic, etc.
Since it is electrically neutral to nSb, a single crystal with few crystal defects can be obtained without affecting the carrier concentration.

[0015]

As described above, according to the present invention, a gas doping method is used as a means for adding impurities to crystals. Therefore, even if the polycrystal is melted, oxides are not formed on the melt surface. There is no scum, which facilitates seeding and crystal growth, and suppresses twinning and polycrystallization. Further, in order to carry out the doping more efficiently, since a cycle of melting to solidification and solidification to melting at a high temperature is adopted, a desired impurity concentration can be obtained. As a result, a single crystal with low crystal defects can be manufactured with a high yield, and the economic effect is significantly increased.

[Brief description of drawings]

FIG. 1 is a sectional view of a single crystal pulling apparatus showing an embodiment of the present invention.

[Explanation of symbols]

 1. Chamber 2. Quartz crucible 3. Seed crystal 4. Seed crystal mounting jig 5. Heater 6. Melt 7. InSb single crystal

Claims (6)

[Claims] 1. A method for producing a semiconductor single crystal by a pulling method, characterized in that, before the start of single crystal growth, a crystal serving as a pulling material is melted and solidified in a high temperature atmosphere gas, and a cycle from solidification to melting is repeated a required number of times. And a method for manufacturing a semiconductor single crystal. 2. The method for producing a semiconductor single crystal according to claim 1, wherein the atmosphere gas is an atmosphere gas which becomes an electrically neutral impurity in the crystal. 3. The method for producing a semiconductor single crystal according to claim 1, wherein the crystal is a III-V group compound semiconductor. 4. The crystal is indium antimony (InS).
The method for producing a semiconductor single crystal according to claim 1, wherein the method comprises b). 5. The method for producing a semiconductor single crystal according to claim 1, wherein the atmosphere gas is nitrogen (N ₂ ) gas. 6. The crystal is indium antimony (InS).
_{2. The} method for producing a semiconductor single crystal according to claim 1, wherein the atmosphere gas comprises b) and the atmosphere gas is nitrogen (N ₂ ) gas.