JPH01179712A - Treatment of scrap indium-phosphorus compound semiconductor - Google Patents

Abstract

PURPOSE:To recover high-purity InP film scrap InP semiconductors in high yield by decomposing powdered scrap InP semiconductors into an InCl3 soln. and PH3, and then selectively hydrolyzing the soln. CONSTITUTION:Scrap indium-phosphorus compd. semiconductors are powdered, and the powdered scrap is decomposed into an indium chloride soln. and hydrogen phosphide by the reaction with hydrochloric acid in an inert gas atmosphere. The soln. is then selectively hydrolyzed to precipitate and recover associated impurities. Since the soln. is further hydrolyzed in succession to the hydrolysis by hydrochloric acid in this process, the concn. of hydrochloric acid after the decomposition reaction is preferably made as low as possible. Accordingly, the scrap InP is effectively heated for the purpose. The heating is appropriately carried out in the air at 300-500 deg.C, hence the decomposition rate is increased to several to several tens percent, and violent frothing, which is frequently seen in the reaction of the powdered scrap with hydrochloric acid, can be eliminated.

Description

[Detailed description of the invention] (Industrial application field) The present invention is an indium-phosphorus compound semiconductor C and below.

The present invention relates to a method for recovering highly pure indium and hydrogen phosphide from scrap generated in processes such as the production and processing of InP compound semiconductors.

(Prior art and its problems) InP is being developed for use as one of the representative materials for IV group compound semiconductors, but like other semiconductor materials, it is difficult to form a single crystal during the single crystallization process. In the process of manufacturing wafers, etc., a considerable portion of indium inevitably becomes scrap. It is very important from the viewpoint of
It is also useful to use it as a raw material for nP4'GaP.

Conventionally, there are the following methods for processing InP scrap.

(1) Pyrolysis method This method requires operation at high temperatures of 900°C or higher.

(2) Method of melting with alkali hydroxide (Unexamined Japanese Patent Publication No. 1983-
(No. 24332) In this method, all phosphorus is converted to sodium phosphate, making it difficult to reuse.

Furthermore, a problem common to these methods is that impurities in the scrap migrate into the recovered metal indium, and their removal is not always easy.

The impurity Qyl that accompanies InP scrap is not constant, but there are animal metals such as tin and zinc that are used as doping agents, and iron and copper that accompany the generation and collection of scrap. Furthermore, gallium-based compound hand conductors may also be present.

(Objective of the Invention) In view of the above, the present inventors have provided a processing method for recovering high-purity In and P from InP compound semiconductor scrap at a high yield by solving the problems of the above-mentioned conventional technology. In order to do this, we first need to decompose InP to form indium in a form that is easy to purify, and at the same time separate and recover phosphorus, remove impurities from it without incurring loss of indium, and make these operations sufficiently economical. As a result of examining processing methods that place emphasis on properties, it was discovered that the above object could be achieved by decomposing an InP compound semiconductor with hydrochloric acid, and the present invention was achieved.

(Structure of the Invention) That is, according to the present invention, indium-phosphorus compound semiconductor scrap is decomposed into an indium chloride solution and hydrogen phosphide by reaction with hydrochloric acid in an inert gas atmosphere.
A method for treating indium-phosphorus compound semiconductor scrap is obtained, which is characterized in that accompanying impurities are precipitated and removed by selective hydrolysis of the indium chloride solution.

As described above, in the present invention, in the treatment of InP scrap, decomposition using hydrochloric acid is employed as a means for decomposing the scrap into indium and phosphorus.

This reaction proceeds as follows, producing an indium chloride solution and hydrogen phosphide mainly consisting of phosphine (PHs, +171-87.4°C).

I n P+ 38C, 13=I n ClOs 10P
Hs l1lInP is also decomposed by sulfuric acid and nitric acid, but the reaction with sulfuric acid is significantly slower than with hydrochloric acid, and - nitric acid has a fairly good decomposition rate, but unlike hydrochloric acid, hydrogen phosphide is oxidized secondarily. and fixed in the liquid as phosphoric acid. This is undesirable not only because it causes loss of valuable materials but also because it interferes with the subsequent impurity removal operation. Furthermore, the advantage of using hydrochloric acid is that even if GaP and GaAr5 are mixed in the scrap, only partial decomposition occurs, but this point is especially noticeable for GaP, and treatment with hydrochloric acid By appropriately selecting the conditions, the decomposition rate of G a P can be kept very low.

The main conditions governing the reaction rate between InP and hydrochloric acid include the particle size of the scrap, the concentration of hydrochloric acid, and the temperature, and it is desirable that the particle size is as small as possible. Scrap generated in processes such as cutting single crystals and polishing wafers is extremely fine and can be used as is, but scrap from single crystallization is usually in the form of irregular lumps, so it is difficult to use scraps that are smaller than one smoke. Grind and process. Hydrochloric acid needs to have a concentration of 0.5N or more, and 2 to 6N is particularly suitable. If the concentration of hydrochloric acid is less than IN, the decomposition rate of scrap will decrease considerably, and if the concentration is too high, stirring will become difficult.
And the volatilization loss of hydrochloric acid increases.

In the method of the present invention, hydrolysis is performed subsequent to decomposition with hydrochloric acid, so it is desirable that the concentration of hydrochloric acid at the end of the decomposition reaction be as low as possible.

Therefore, after conducting separate studies on the reactivity of InP scrap with hydrochloric acid, it was found that heat treatment of the scrap was effective in addition to the above-mentioned conditions. It is appropriate to carry out the heat treatment in the air at a temperature of 300 to 500°C, thereby reducing the decomposition rate by a low concentration of hydrochloric acid to a factor of 1 to 1.
096, and also eliminates the significant foaming that often occurs with powdered scrap when reacting with hydrochloric acid.

For example, when scrap with a particle size of 100 μm or less is treated with a small excess of hydrochloric acid at a concentration of 2 to 6 N at 60 to 100°C for 1 hour, the decomposition rate is 85 to 100%, but heat treatment of scrap If this is done, the decomposition rate increases to 92-100%. This reaction is carried out in an inert gas atmosphere, which has the effect of preventing the generated hydrogen phosphide from being oxidized and remaining in the liquid, as well as preventing the danger of spontaneous combustion.

When scrap is processed in this manner, the proportion of phosphorus fixed in the liquid as hydronic acid is only less than is, and the rest evaporates as hydrogen phosphide.

The 9 atmosphere gas released from the reaction system of InP scrap and hydrochloric acid contains phosphine and a trace amount of diphosphine (PtH<
-Boiling point: 58°C), hydrogen chloride, water, etc. Chloride water purple by alkaline cleaning from this gas? After removal, it is cooled to around -70° C. to remove the phosphorus and moisture, and then cooled to below -100° C. to recover phosphine Wl-wI. If necessary, this phosphine is further refined by removing impurities by low-temperature distillation.

Metallic indium is usually extracted by an electrochemical method from the indium chloride solution produced in the above hydrochloric acid decomposition reaction.
Prior to that, tin, iron and other impurities contained therein are removed. In particular, tin has a slightly higher potential than indium and is precipitated together with indium, so in order to collect highly pure indium, it is desirable to remove it sufficiently in advance.

The purification method adopted in the method of the present invention is to adjust the hydrogen ion concentration of the indium chloride solution, selectively hydrolyze impurities such as tin and iron, and remove them as precipitates.

This is because tin and iron present in the indium chloride solution obtained by the reaction of InP scrap with hydrochloric acid are tetravalent and trivalent, respectively.
Even at a low concentration of 0.1jp7 or less, indium undergoes hydrolysis and precipitates in the weakly acidic region of pH 1.5 to 3. In contrast, as shown in Figure 1, indium precipitates in a liquid state. 20g/J if there is almost no phosphoric acid in the
This is based on the knowledge that even at a concentration of 3, precipitation does not occur up to around pH 3. Selection of pH is important in selective hydrolysis, and this is determined by considering two factors: indium concentration and impurity removal rate.

Generally, it is appropriate for the pH to be in the range of 2 to 3, and under these conditions, a high removal rate of tin, iron, etc. can be obtained without substantial loss of indium.

In carrying out this method, caustic alkali or ammonia is added to indium chloride obtained by hydrochloric acid decomposition to adjust pF to around 2 to 3, and then tin (divalent) and iron (divalent) contained in the solution are added. Add an oxidizing agent necessary for oxidizing oxidizable ions such as
to flocculate the precipitate. As a result, tin is almost completely removed, and most of the iron is precipitated and removed. As the oxidizing agent, aqueous peroxide, sodium hypochlorite, potassium permanganate, etc. are used, and especially in the case of potassium permanganate, a high removal rate can be obtained. This is presumed to be due to the adsorption effect of hydrated manganese dioxide produced in the oxidation reaction. Now, the concentration of indium is 5011/, L tin (
Bivalent) 3o 01 da/,,e, Iron (bivalent) 100~/
! When this treatment is carried out using hydrogen peroxide as an oxidizing agent on a solution with a composition of
%, and the loss of -10,000 indium is only less than 1. Furthermore, when using potassium permanganate as an oxidizing agent, the removal rate of tin and iron was 99% or more, respectively, and 8°~
Rise to 98c6. Note that this method is also effective to some extent for gallium, and when potassium permanganate is used, about 90% is removed.

Next, the present invention will be specifically explained using Examples, but the following Examples are not intended to limit the scope of the present invention.

Example 1 Small lump-like scrap generated in the production process of n-type InP single crystal with tin as a dopant was processed into 44 μm using a ball mill.
The composition shown in Table 1 was obtained as a result of analysis of the powder.

Table 1 Component Content (wt%) In 79.21 p 20.04 Sn 0.41 Fe O,012 M9. Ca, etc. 40p of this pulverized material and 69114 of pure water are mixed in a stirring device, a reflux condenser, and! Once placed in a four-loop flask equipped with a separating funnel and a gas blowing tube, nitrogen gas was blown in at 2 minutes per minute while stirring.
! It passed at a speed of When the temperature reached 60°C by external heating, 74 d of hydrochloric acid with a concentration of 12N was added from the separating funnel.
was added over a period of 30 minutes, and then the temperature was raised to 95° C. and the reaction was continued for an additional 30 minutes. In addition, phosphine was recovered from the gas exiting from the top of the reflux condenser in accordance with Example 3.

The indium chloride solution produced in this decomposition reaction was filtered to remove a small amount of unreacted materials, and the P washing solution was analyzed as 600 WLt. The results are shown in Table 2. It has migrated.

Table 2 Component Concentration Water solubilization rate C%) In
49.11 1/43 93p 60.
2 Da/I! J O,45Sn 268
W/13 98Fe 8. OW/II
10011) HO,52 Take 580 Wtl from this indium chloride solution and
While heating to 0°C, add aqueous ammonia with a concentration of 28 to adjust the pH to 2.5, then gradually add 15 dl of a 2% solution of potassium permanganate, boil for 10 minutes, and finally adjust the pH to 2.5. % manganese sulfate solution was added to destroy excess potassium permanganate and readjust p[() to 2.5.

After the treated liquid was left to cool, a small amount of nonionic polymer flocculant was added and precipitated by filtration.
It was set to 1. The analysis results of the thus purified indium chloride solution are shown in Table 3, and indium with a purity of 99.9914 was recovered from this solution by precipitating indium using an aluminum plate.

Table 3 Component Concentration Removal rate (%) In
42.85g/4 0.70 (recovery rate 8-9.3
Value) P 3.2 da/43 94Sn
O,31!9/43 99.9Fe 1
,2+1197. , g sa! j! Example 2 Example 2 is a case of processing muddy scrap generated during processing of InP single crystal. This scrap was sieved to remove a -53 μm portion, washed with water, and dried to obtain the composition shown in Table 4.

Table 4 Component Content (weight-)In
68.70P
16.90Sn 4.5X
10″″3F’e a, 02xlO
-2Ga 2.40X10''-2 carboy, Ca5i, etc. 30I of this dried material was taken and heat-treated at 400°C for 1 hour in an electric Matsufuru furnace, followed by Example 1
Similarly, a small excess of hydrochloric acid was added to decompose. Table 5 shows the results of analysis of 500 ag of the r-washing solution, showing that 96% of the indium was soluble in water. In addition, when hydrochloric acid treatment was performed without heat treatment, it took about 1.5 hours to add hydrochloric acid due to foaming of the contents of the flask, and the water solubilization rate remained low at 71 cm. .

Table 5 Component Concentration Water solubilization rate c%) In
39.58g/J 96P 42.
6 Ing/, 130.42Sn 2.5W/
4 93Fe 17.8 q/II
98Ga 7.81n9/43 54 Take 480R1 from this indium chloride solution and heat it to about 70℃
While heating the eggs, add aqueous ammonia with a concentration of 28% to adjust the pH.
After adjusting the concentration to 3.0, gradually add 7 d of potassium permanganate solution with a concentration of 1.0% and boil for 10 minutes.Finally, add a manganese sulfate solution with a concentration of 1.0% to decompose excess potassium permanganate. and p[( was readjusted to 3.0.

After the treated liquid was left to cool, a small amount of nonionic polymer agglomerate was added and filtered to form a precipitate.
And so. The analysis results of the indium chloride solution purified in this way are shown in Table 6, and from this solution Example 1
Indium with a purity of 99.99- was recovered using the same method as in the case of .

Table 6 Component Concentration Removal rate (%) I n 34.29g743 0.75
(Recovery rate 99.3%) P 14.51R9/Type 61 Sn <0.1 my/,,e)95Fe
O,9N9/E 94 Ga O,7yty/4390 Example 3 In Example 1, the nitrogen-based gas coming out from the top of the reflux condenser contained phosphine and a trace amount of diphosphine, as well as hydrogen chloride and water. etc. are included. This gas is sequentially passed through a gas washing bottle containing a sodium hydroxide solution with a concentration of IN and a collector cooled to -77°C to remove impurities other than phosphine. The phosphine was collected. The amount of phosphine recovered was 7.6 g, which corresponds to 94.8% of the phosphorus in the scrap.

(Effects of the Invention) By adopting the above configuration, the present invention makes it possible to recover indium and phosphorus from InP scrap with mild conditions and simple operations in high purity and good yield. Therefore, it is very useful in the field of semiconductor industry.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between phosphoric acid concentration and In precipitation starting pH (95° C.). Patent applicant: Mitsubishi Metals Co., Ltd. Naokiku Yoshihiro Jll
1 plan of two east L+, zo% lノ〉Shinon *(,P>

Claims (4)

[Claims] (1) After pulverizing indium-phosphorus compound semiconductor scrap and decomposing the pulverized scrap into an indium chloride solution and hydrogen phosphide by reaction with hydrochloric acid in an inert gas atmosphere, the indium chloride solution is selectively removed. 1. A method for treating indium-phosphorus compound semiconductor scrap, which comprises precipitating and removing accompanying impurities through hydrolysis. (2) A method for processing indium-phosphorus compound semiconductor scrap according to claim (1), wherein the indium-phosphorus compound semiconductor scrap is heated in air at 300 to 500°C prior to the reaction with the hydrochloric acid. A treatment method characterized by heat treatment in the range of (3) A method for processing indium-phosphorus compound semiconductor scrap according to claim (1), in which potassium permanganate is used as an oxidizing agent in selectively hydrolyzing the indium chloride solution. A processing method characterized by (4) A method for treating an indium-phosphorus compound semiconductor according to claim (1), characterized in that phosphine is recovered from the gas containing hydrogen phosphide.