JP6184898B2 - Chlorosilanes, purification method of chlorosilanes, and silicon crystals - Google Patents

Description

  The present invention relates to a purification technique for chlorosilanes including trichlorosilane, and more particularly to a technique for producing high-purity chlorosilanes suitable as a raw material for producing silicon crystals used in the production of semiconductor devices.

  Semiconductor grade high-purity polycrystalline silicon is usually produced by a CVD method called a “Siemens method” using a chlorosilane gas mainly containing trichlorosilane in the presence of hydrogen as a raw material. Accordingly, chlorosilanes that are raw materials for high-purity polycrystalline silicon are also required to have extremely high purity.

  In particular, if the impurities contained in the raw material chlorosilanes are impurities such as phosphorus and arsenic that serve as donors in the silicon crystal, or impurities such as boron and aluminum that serve as acceptors, these impurities are present in trace amounts. Even so, it significantly affects the electrical properties (resistivity) of the polycrystalline silicon produced. For this reason, provision of a technique for efficiently removing the donor impurities and acceptor impurities contained in the raw material chlorosilanes to achieve high purity has great practical significance.

  In general, chlorosilanes for producing polycrystalline silicon are chlorosilane distillates obtained from metallurgical grade silicon containing a relatively large amount of impurities (so-called metal grade silicon, hereinafter referred to as “metal silicon”) by a known method. After being obtained, the chlorosilane distillate is further purified by a technique such as distillation to be purified.

  However, usually, the above-mentioned donor impurities and acceptor impurities are contained in metal silicon in the order of several hundred ppba to several hundred ppma in terms of atomic ratio. For this reason, these impurities are not sufficiently removed in the purification process of chlorosilane distillates, and donor impurities and acceptor impurities remain in the finally obtained chlorosilanes. The problem of degrading the quality of polycrystalline silicon can arise.

As a method for obtaining a chlorosilane distillate, a hydrogenation step for obtaining a chlorosilane distillate containing trichlorosilane (SiHCl ₃ ) by reacting a tetrachlorosilane (SiCl ₄ ) -containing material with hydrogen in the presence of metallic silicon. (For example, see Japanese translations of PCT publication No. 2008-532907 (Patent Document 1), JP-A-58-217422 (Patent Document 2), JP-A-58-161915 (Patent Document 3), etc.) ).

  In addition, as another method for obtaining a chlorosilane distillate, a chlorination step is performed in which metal silicon and hydrogen chloride are brought into contact with each other in the presence of a catalyst to perform a chlorination reaction to obtain a chlorosilane distillate containing trichlorosilane. Is also known (see, for example, JP-A-2005-67979 (Patent Document 4)).

  Donor impurities and acceptor impurities contained in metallic silicon are considered to be mixed in the crude chlorosilanes as various forms of compounds, etc. by being hydrogenated or chlorinated simultaneously with the production of the crude chlorosilanes. ing. Such crude chlorosilanes are purified to obtain high-purity chlorosilanes. If the boiling point of a compound such as a donor impurity or an acceptor impurity is close to that of trichlorosilane, these impurities are removed by general distillation. It is difficult to separate and remove by a method. If polycrystalline silicon is produced using chlorosilanes with insufficient removal of donor impurities and acceptor impurities as raw materials, polycrystalline silicon having desired characteristics cannot be obtained.

  Under such circumstances, various methods have been proposed as methods for removing donor impurities and acceptor impurities in the chlorosilane distillate. For example, a method has been proposed in which an organic substance is added to a chlorosilane distillate to form an adduct with a donor impurity or an acceptor impurity, and then purified by distillation to obtain a high-purity chlorosilane.

  Specifically, JP-A-2005-67979 (Patent Document 4) discloses a method of distilling and purifying by adding ethers to chlorosilanes. US Pat. No. 3,126,248 (Patent Document 5) discloses a method for removing impurities by adding an organic compound composed of dioxane, benzaldehyde, methyl ethyl ketone, dimethylglyoxime, and valerolactone. Furthermore, JP-A-2009-62213 (Patent Document 6) discloses that chlorosilanes are reacted with oxygen in the presence of benzaldehyde to convert impurities into high-boiling compounds, and the treated chlorosilanes are distilled. A method for separating high-boiling impurities and chlorosilanes is disclosed.

  In addition, a method has been proposed in which a metal chloride is added to a chlorosilane distillate to produce an adduct with a donor impurity or an acceptor impurity and then purified by distillation to obtain a high-purity chlorosilane.

Specifically, US Pat. No. 2,821,460 (Patent Document 7) discloses a method in which aluminum chloride is added to chlorosilanes to form an AlCl ₃ · PCl ₅ complex, followed by distillation purification. Japanese Patent Application Laid-Open No. 4-300206 (Patent Document 8) discloses a method in which an inorganic salt aqueous solution such as TiCl ₄ is added at a high concentration to hydrolyze impurities to form a high-boiling compound, followed by distillation purification. ing.

  Further, a method for removing impurities contained in chlorosilanes by adsorbing them on alumina, silica gel, activated carbon or the like has been proposed.

  Specifically, in US Pat. No. 3,252,752 (Patent Document 9), a substance having a lone electron pair (for example, a substance such as propionitrile having a nitrogen atom or benzaldehyde having an oxygen atom), activated carbon, A method is disclosed in which impurities are trapped and removed by immobilizing on an adsorbent such as silica gel and flowing a chlorosilane gas. German Patent 1,289,834 (Patent Document 10) discloses a method for removing impurities by contacting chlorosilanes with activated alumina in a liquid or vapor state. Further, US Pat. No. 4,112,057 (Patent Document 11) discloses a method for removing impurities by bringing chlorosilanes into contact with a metal oxide such as hydrated silica gel or alumina gel. No.-2407 (Patent Document 12) discloses a method of removing impurities by contacting chlorosilanes with an alkali or alkaline earth fluoride salt.

  In addition to these methods, a complex is formed by introducing a small amount of oxygen into chlorosilanes and reacting under high temperature conditions, and a new complex is formed by reacting this complex with donor impurities and acceptor impurities. A method of obtaining chlorosilanes having a low impurity concentration by separating them in a distillation step of chlorosilanes has also been proposed (see Japanese Patent Publication No. 58-500895 (Patent Document 13)).

Special table 2008-532907 JP 58-217422 A JP 58-161915 A JP 2005-67979 A U.S. Pat.No. 3,126,248 JP 2009-62213 U.S. Pat.No. 2,821,460 Japanese Unexamined Patent Publication No. 4-300206 U.S. Pat.No. 3,252,752 German Patent 1,289,834 U.S. Pat.No. 4,112,057 Japanese Patent Laid-Open No. 2001-2407 JP-T58-500895

  The quality of semiconductor grade trichlorosilane is evaluated by the resistance value of silicon polycrystal synthesized using this as a raw material, 500 Ω-cm or more for general-purpose trichlorosilane, and high grade trichlorosilane. In the case of trichlorosilane for synthesizing silicon crystals for sensors, detectors, and high voltages for which high resistance is required, a value of 5000 Ω-cm or more is required. It is done.

  Among the conventional purification methods described above, a method of adding an organic substance or a metal chloride to a chlorosilane distillate to produce an adduct with a donor impurity or an acceptor impurity is obtained by combining an adduct with trichlorosilane as a main component. When a difference in boiling point occurs between them, chlorosilanes can be purified with high purity by a subsequent distillation step.

  However, as described in the prior documents listed above, the organic substance that is effective in removing impurities in the purification method of adding an organic substance to a chlorosilane distillate is an organic substance containing an element having a lone pair of electrons. However, there are considerable restrictions on the selection of such organic substances.

  For example, the added organic matter should not be decomposed very easily during the purification process, and products near the boiling point of chlorosilanes may be reduced by reaction with substances in the chlorosilane distillate. It is also necessary that it does not occur. In particular, when the organic substance containing an element having a lone pair is a solid, it is necessary to consider whether it dissolves at the handling temperature of the chlorosilane distillate and whether it will precipitate due to operating conditions during handling. However, sufficient consideration is necessary to prevent moisture from being mixed at the time of charging. In other words, it is necessary to carefully select an organic substance effective for removing impurities in consideration of various conditions of the purification process.

Benzaldehyde (C ₆ H ₅ CHO) is known as an organic substance containing an element having a lone electron pair effective for removing donor impurities and acceptor impurities (see Patent Document 5, Patent Document 6, Patent Document 9, etc.). . Benzaldehyde is easy to handle at the time of addition and is easily available, but benzaldehydes form a solid high polymer in the presence of a metal chloride such as iron chloride. Since such highly polymerized products are solidified to generate clogs in pipes and containers, it is necessary to periodically stop the production equipment in order to remove the solids.

  The purification method of adding a metal chloride to a chlorosilane distillate is not easy to handle, and there are problems such as complicated waste disposal.

  The method of removing impurities contained in chlorosilanes by adsorbing them on alumina, silica gel, activated carbon, etc. requires an apparatus such as an adsorption tower, which complicates the equipment, and makes it easy to support the adsorbate. There is also a problem that there are no problems, such as handling of adsorbate after breakthrough and waste disposal.

  In other impurity removal methods, it is necessary to introduce a small amount of oxygen into chlorosilanes under high temperature conditions, and to react at high temperatures, and thus there are various problems such as inability to operate under simple and gentle conditions. ing.

  The present invention has been made in view of the problems of the conventional purification method of chlorosilanes as described above, and the object thereof is phosphorus (P) and acceptor which are donor impurities from distillates of chlorosilanes. An object of the present invention is to provide a technology that enables the production of high-purity chlorosilanes without complicating the purification process by removing boron (B) as an impurity at the same time.

In order to solve the above-mentioned problems, the purification method of chlorosilanes according to the present invention uses trichlorosilane containing phosphorus trichloride (PCl ₃ ) and boron trichloride (BCl ₃ ) as impurities as a disproportionation reaction catalyst. It is circulated to the anion exchange resin, the phosphorus trichloride (PCl ₃₎ and three composites phosphine, boron chloride (BCl ₃₎ and allowed to disproportionation (PH ₃₎ and borane _{(BH 3) (PH 3 -BH} 3 ) Is generated.

In the method for purifying chlorosilanes according to the present invention, the composite (PH ₃ -BH ₃ ) is distilled and separated from the chlorosilanes after the first step, and phosphorus impurities and boron impurities are simultaneously removed from the trichlorosilane. A second step is provided.

  In the purification method of chlorosilanes according to the present invention, the chlorosilanes after the second step are further distilled to separate the purified dichlorosilane, trichlorosilane, or tetrachlorosilane at least one chlorosilane. It can be set as the aspect provided with.

  For example, the anion exchange resin is a weakly basic anion exchange resin having a tertiary amine as an exchange group.

  For example, the anion exchange resin is a type I strongly basic anion exchange resin having trimethylammonium as an exchange group.

  The silicon crystal according to the present invention is a silicon crystal grown using chlorosilanes such as trichlorosilane obtained by the above-described purification method as a raw material, wherein the impurity concentration of phosphorus is less than 0.03 ppba and the impurity concentration of boron is 0. Less than .01 ppba.

In the method for purifying chlorosilanes according to the present invention, phosphorus trichloride (PCl ₃ ) contained in trichlorosilane is obtained by circulating trichlorosilane to be purified through an anion exchange resin as a disproportionation reaction catalyst. And a step of disproportionating boron trichloride (BCl ₃ ) to produce a composite of phosphine (PH ₃ ) and borane (BH ₃ ) (PH ₃ -BH ₃ ).

If the composite (PH ₃ -BH ₃ ) is distilled and separated from the chlorosilanes after the above steps, phosphorus impurities and boron impurities can be simultaneously removed from trichlorosilane without complicating the purification step. It becomes possible.

It is a flowchart for demonstrating the purification method of chlorosilane which concerns on this invention. It is a measurement example of GC-FPD. It is a measurement example of GC-MS. The figure which compared the specific resistance value of the silicon crystal obtained by carrying out the epitaxial growth using each gas obtained by further distilling and separating chlorosilanes obtained after the distillation separation process of PH ₃ -BH ₃ as a raw material (depth) Direction mapping).

  Below, with reference to drawings, the purification method of chlorosilanes concerning the present invention is explained concretely.

  FIG. 1 is a flowchart for explaining a method for purifying chlorosilanes according to the present invention.

  First, trichlorosilane is synthesized from metallic silicon and hydrochloric acid (S101). Since this trichlorosilane contains a large amount of phosphorus compounds and boron compounds as impurities, it is purified by distillation by a conventional method to obtain semiconductor grade trichlorosilane (S102).

The trichlorosilane after the distillation purification contains, to a small extent, phosphorus trichloride (PCl ₃ ) and boron trichloride (BCl ₃ ) as impurities. Therefore, this trichlorosilane is passed through an anion exchange resin as a disproportionation reaction catalyst (S103). Through distribution to this anion exchange resin, phosphorus trichloride (PCl ₃ ) and boron trichloride (BCl ₃ ) are disproportionated, and a phosphine (PH ₃ ) and borane (BH ₃ ) complex (PH ₃ -BH) ₃ ) Generate.

In addition, when trichlorosilane circulates, there is a possibility that phosphorus trichloride (PCl ₃ ) and boron trichloride (BCl ₃ ) may be adsorbed on the anion exchange resin. Adsorption to was not observed at all. This fact means that the regeneration treatment of the anion exchange resin used for the above distribution is unnecessary, and the fact that the resin regeneration treatment operation is unnecessary is a very important advantage in practice. As described above, according to the present invention, the purification process can be performed at low cost without complicating the purification process.

The present inventors understand the reason why the composite (PH ₃ —BH ₃ ) is formed as follows. Nitrogen (N) atoms on the anion exchange resin surface have a positive polarizability, while Cl atoms have a negative polarizability due to their electronegativity. Therefore, due to the polarization effect, phosphorus trichloride (PCl ₃ ) and boron trichloride (BCl ₃ ) are attracted to nitrogen (N) on the surface of the anion exchange resin that is positively polarized. At the same time, the disproportionation reaction of trichlorosilane (exchange reaction of -H and -Cl) proceeds simultaneously. Phosphorus trichloride (PCl ₃ ) and boron trichloride (BCl ₃ ) are supplied with —H from the hydrogen source generated by the above-mentioned disproportionation reaction of trichlorosilane, and phosphine (PH ₃ ) and borane (BH ₃ ) to form a composite (PH ₃ -BH _3). As described above, the composite (PH ₃ -BH ₃₎ because it does not adsorb to the anion exchange resin surface, and flows out together with the trichlorosilane.

  The distribution of the trichlorosilane is specifically performed as follows. An anion exchange resin is filled into a cylindrical tube, thoroughly washed with ethanol, and the washing is repeated until the water content in ethanol becomes 10 ppm or less. Next, toluene is passed through and the washing is repeated until the ethanol in the toluene is 50 ppm or less. The anion exchange resin after washing is controlled to a temperature range of 55 to 60 ° C., and for example, trichlorosilane is circulated (liquid flow) at a rate of 4 kg / min (linear velocity of 2.8 mm / sec), and trichlorosilane is mainly used. A component liquid is obtained.

  The anion exchange resin may be a weak basic anion exchange resin or a strong basic anion exchange resin. Preferably, as the weak base anion exchange resin, a weak base anion exchange resin having a tertiary amine as an exchange group is selected, and as the strong base anion exchange resin, trimethyl ammonium is used as an exchange group. A type I strongly basic anion exchange resin is selected.

When the liquid after passing through the anion exchange resin is analyzed by distillation fraction, the amount of P and B on the trichlorosilane side is extremely small, and it is confirmed that it exists on the dichlorosilane side produced as a result of the disproportionation reaction. It was done. From this, it can be concluded that the composite (PH ₃ -BH ₃ ) has a low boiling point. Moreover, as a result of qualitative analysis by GC-FPD (Flame Photometric Detector) and GC-MS, it was concluded that this low boiling point component was PH ₃ -BH ₃ .

  FIG. 2 shows a measurement example of GC-FPD. In this measurement, an optical filter (526 nm) that detects only phosphor (P) emission by a hydrogen-oxygen combustion flame and transmits only phosphor (P) emission. ) For selective detection. The apparatus used is GC-2010FPD manufactured by Shimadzu Corporation.

  As the GC separation column, a packed column capable of injecting many samples was used in order to ensure sensitivity. For the liquid phase, KF-96H (1,000,000 cps) manufactured by Shin-Etsu Chemical Co., Ltd. is used, and particles obtained by crushing Teflon (registered trademark) PTFE are used for the carrier, thereby increasing the separation of low-boiling components. Therefore, the column temperature was set to 10 ° C.

  FIG. 3 shows an example of GC-MS measurement. An Agilent 5975 MSD manufactured by Agilent was used for the GC-MS measurement. The separation column used was DB-1 ms (60 m × 0.53 mm diameter, liquid phase 1.5 μm). Note that mass spectrometry was performed in an EI mode (electron impact ionization) and an applied voltage of + 200V.

The boiling point of the composite (PH ₃ —BH ₃ ) produced by the above flow is considered to be between −85 ° C. and −87.5. This is because, in GC measurement, when the above-mentioned GC separation column of nonpolar silicone oil type in which the elution time is eluted in the order of the boiling point is used, HCl having a boiling point of −85 ° C. and B ₂ H _{6 having} a boiling point of −87.5 By eluting in between.

If the boiling point of the composite (PH ₃ -BH ₃ ) is in such a low temperature region, separation from trichlorosilane having a boiling point of 32 ° C. is easy, and tetrachlorosilane (boiling point 57) generated by the disproportionation reaction of trichlorosilane. Is more easily separated. Further, dichlorosilane (boiling point 8 ° C.) is also generated by the disproportionation reaction of trichlorosilane, but it is not difficult to separate dichlorosilane and the composite (PH ₃ —BH ₃ ).

Therefore, PH ₃ -BH ₃ is separated by distillation (S104), and the separated PH ₃ -BH ₃ is removed. At this time, if the reflux ratio at the time of distillation is set high, it can be separated to the ppbw level.

Incidentally, the boiling point of PCl ₃ is 76 ° C., and the boiling point of BCl ₃ is 12 ° C. In other words, phosphorus trichloride (PCl ₃ ) and boron trichloride (BCl ₃ ) are disproportionated to form a composite (PH ₃ -BH ₃ ), resulting in a low-boiling compound, which is separated from chlorosilanes. It became easy.

  As described above, tetrachlorosilane (boiling point 57 ° C.) and dichlorosilane (boiling point 8 ° C.) are produced by the disproportionation reaction of trichlorosilane, and these chlorosilanes are further separated by distillation and purified dichlorosilane. At least one chlorosilane of chlorosilane, trichlorosilane, or tetrachlorosilane can be separated. In the example shown in FIG. 1, the chlorosilanes are separated by distillation in two stages, and the rough distillation process in step S105 is provided before the distillation process in step S106.

  Needless to say, the trichlorosilane obtained in step 106 may be returned to step S103 and the subsequent steps may be repeated for further purification.

Example 1 Resistivity of Epitaxial Film FIG. 4 is obtained by further distilling and separating (S105, S106) chlorosilanes obtained after the above-described composite (PH ₃ -BH ₃ ) distillation separation step (S104). It is the figure (depth direction mapping) which compared the specific resistance value of the silicon crystal obtained by carrying out the epitaxial growth using each obtained gas as a raw material.

  Samples 1A to 1E were obtained by further subjecting dichlorosilane (1A) distilled and separated in step S105, dichlorosilane (1B) distilled and separated in step S106, and dichlorosilane distilled and separated in step S106 to precision distillation, respectively. Silicon crystals obtained by epitaxial growth using the obtained dichlorosilane (1C), trichlorosilane (1D) distilled and separated in step S106, and tetrachlorosilane (1E) distilled and separated in step S106 as raw materials. As an epitaxial substrate, a non-doped (n-type) silicon substrate having a specific resistance of 990 Ω-cm (10 mm × 5 mm, thickness 0.75 mm) was used for each sample.

  For the growth of the epitaxial film, a transparent reaction tube made of quartz was used, the light from the infrared lamp was condensed and heated from the outside, and high purity glassy carbon was used for the susceptor. The surface temperature of the silicon substrate was monitored with a radiation thermometer and controlled at 1120 to 1126 ° C.

Looking at sample 1A (dichlorosilane distilled and separated in step S105), the average specific resistance value is relatively low at 1,152 Ω-cm (n-type), and from this, PH ₃ -BH ₃ is It can be seen that it remains at a higher concentration on the fraction side of dichlorosilane having a relatively low boiling point than trichlorosilane or tetrachlorosilane.

In addition, a region having a high specific resistance value is recognized locally at the interface between the substrate surface and the epitaxial film. This phenomenon is considered to be a result of PH ₃ —BH ₃ remaining in dichlorosilane being used as a source, P and B being taken into the epitaxial film, and compensating each other as a donor and an acceptor. However, if the epitaxial growth is continued, the specific resistance value shows a constant value of about 1,100 Ω-cm. This is because, since the boiling point of PH ₃ -BH ₃ is low as described above, vaporization starts from the moment the valve of the container (10 liters) filled with dichlorosilane is opened, and the concentration gradually decreases.

Next, the sample 1B (dichlorosilane obtained by distillation separation in step S106) and the sample 1C (dichlorosilane obtained by further precision distillation of the dichlorosilane obtained by distillation separation in step S106) are higher than the sample A. Sample 1B has an average specific resistance of 1,503 Ω-cm (n-type), and sample 1C has an average specific resistance of 1,751 Ω-cm (n-type). That is, the PH ₃ —BH ₃ content in dichlorosilane is reduced by distillation.

  As for sample 1D (trichlorosilane distilled and separated in step S106) and sample 1E (tetrachlorosilane distilled and separated in step S106), the average specific resistance values are 7,484 Ω-cm (n-type) and 6, respectively. It was confirmed that an epitaxial silicon film having a high resistance of 495 Ω-cm (n-type) was obtained.

  The above results are summarized in Table 1.

[Example 2] Specific resistance of epitaxial film Table 2 shows silicon crystals epitaxially grown using trichlorosilane after step S102 (before step S103), dichlorosilane, trichlorosilane, and tetrachlorosilane after step S106 as source gases. It is the table | surface which put together evaluation results, such as specific resistance, P and B density | concentration ([P] and [B]).

  The anion exchange resins used for the distribution of trichlorosilane were all manufactured by Rohm and Haas, and were weakly basic (Amberlyst B20) in Example 2A and strongly basic (Amberlite IRA400J in Example 2B). In the comparative example, it is strongly acidic (Amberlite IR120B).

  The specific resistance is measured by a spread resistance measurement method using two probes (apparatus: SSM-150 manufactured by Nippon SSM Co., Ltd.). The concentrations of P and B in the epitaxial silicon film were quantified by a photoluminescence method in accordance with JISH0615 (1996).

In the distillation separation process, PH ₃ —BH ₃ having a low boiling point is likely to be mixed on the dichlorosilane side having a relatively low boiling point. On the other hand, POCl ₃ having a high boiling point is likely to be mixed with the tetrachlorosilane side having a relatively high boiling point. For this reason, it is difficult for impurities of P and B to be taken into trichlorosilane having a boiling point between dichlorosilane and tetrachlorosilane.

  As a result, when silicon crystals are grown using trichlorosilane purified according to the present invention as a raw material, as shown in Examples 2A and 2B, the impurity concentration of phosphorus is less than 0.03 ppba and the impurity concentration of boron is less than 0.01 ppba. A sufficiently high purity can be obtained.

As described above, in the method for purifying chlorosilanes according to the present invention, trichlorosilane to be purified is circulated through an anion exchange resin as a disproportionation reaction catalyst, whereby trichlorosilane contained in trichlorosilane is contained. was the provision of the step of generating a phosphorus (PCl ₃₎ and tertiary phosphines, boron chloride (BCl ₃₎ and allowed to disproportionation (PH ₃₎ and composites of borane _{(BH 3) (PH 3 -BH} 3).

If the composite (PH ₃ -BH ₃ ) is distilled and separated from the chlorosilanes after the above steps, phosphorus impurities and boron impurities can be simultaneously removed from trichlorosilane without complicating the purification step. It becomes possible.

  In the present invention, phosphorus (P), which is a donor impurity, and boron (B), which is an acceptor impurity, are simultaneously removed from distillates of chlorosilanes, so that high-purity chlorosilanes can be produced without complicating the purification process. Provide the technology that makes it possible.

Claims (3)

Phosphorus trichloride (PCl ₃₎ and three-trichlorosilane comprising boron chloride (BCl ₃₎ as an impurity, it is circulated to the anion-exchange resin as a disproportionation reaction catalyst, the phosphorus trichloride (PCl ₃₎ and boron trichloride (BCl ₃ ) is disproportionated to form a composite of phosphine (PH ₃ ) and borane (BH ₃ ) (PH ₃ -BH ₃ ) having a boiling point between −85 ° C. and −87.5 a first step of producing a
A second step of simultaneously removing phosphorus impurities and boron impurities from the trichlorosilane by distillation separation of the composite (PH ₃ -BH ₃ ) from the chlorosilanes after the first step ;
A method for purifying chlorosilanes, comprising a third step of further distilling the chlorosilanes after the second step to separate the purified trichlorosilane. The method for purifying chlorosilanes according to claim 1 , wherein the anion exchange resin is a weakly basic anion exchange resin having a tertiary amine as an exchange group. The method for purifying chlorosilanes according to claim 1 , wherein the anion exchange resin is a type I strongly basic anion exchange resin having trimethylammonium as an exchange group.