METHOD AND SYSTEM FOR SELECTIVE RECOVERY OF MONOCHLOROSILANE AND DICHLOROSILANE IN POLYSILICON PRODUCTION PROCESS

A method and system for selectively recovering monochlorosilane and dichlorosilane from polysilicon production process are provided. The system and method selectively recover the monochlorosilane and the dichlorosilane contained in an exhaust stream discharged from a chemical vapor deposition unit for a polysilicon production process and the monochlorosilanes and the dichlorosilanes may be obtained with minimal capital investment or complexity.

BACKGROUND

Field

One or more embodiments of the present invention relate to a method for selective recovery of monochlorosilane and dichlorosilane from a polysilicon production process and a system thereof.

Description of the Related Art

Polysilicon is a source material of semiconductors and photovoltaic solar panels. There are several methods to produce polysilicon, but the most common method is the Siemens® process. The Siemens® process is the growth of silicon onto electrified silicon filaments by chemical vapor deposition of silicon from typically a mixture of a purified trichlorosilane with an excess of hydrogen. The exhaust stream from the Siemens® process contains unreacted hydrogen and trichlorosilane as well as byproducts monochlorosilane, dichlorosilane, tetrachlorosilane and hydrogen chloride.

Monochlorosilane, which is included in the exhaust stream from the chemical vapor deposition reactor, can be a precursor for synthesizing trisilylamine or diisopropylaminosilane. Trisilylamine and diisopropylaminosilane are used in the semiconductor chip manufacturing process as a precursor of silicon nitrogen and silicon oxynitride films.

Dichlorosilane, which is also included in the exhaust stream from the chemical vapor deposition reactor, can be a precursor of bis(tertiary-butylamino)silane or bis(Diethylamino)silane. The aminosilane, bis(tertiary-butylamino)silane and bis(Diethylamino)silane are precursors for the chemical vapor deposition of uniform silicon nitride, silicon oxynitride and silicon dioxide films used in semiconductor device fabrication.

Information disclosed in this Background section of the present disclosure was already recognized by the inventors or acquired during the process of attaining the present invention. Therefore, the Background section of the present disclosure may contain information that is not prior art because the information may not be known to a person of ordinary skill in the art.

SUMMARY

In accordance with one or more embodiments, there is provided a method for selective recovery of monochlorosilane and dichlorosilane in polysilicon production process, including: i) discharging an exhaust gas from a chemical vapor deposition reactor for producing polysilicon, wherein the exhaust gas includes at least hydrogen, hydrogen chloride, silicon tetrachloride, trichlorosilane, monochlorosilane and dichlorosilane; ii) removing the hydrogen and hydrogen chloride from the exhaust gas in a gas recovery system to produce a condensate; iii) removing the silicon tetrachloride and the trichlorosilane from the condensate using a set of distillation columns to produce a hydrogen silicon-tetrachloride trichlorosilane removed result; and iv) selectively recovering an upper stream and lower stream from the hydrogen silicon-tetrachloride trichlorosilane removed result, in a selective distillation column, wherein the upper stream comprises monochlorosilane and the lower stream comprises dichlorosilane.

In one or more embodiments, the selective recovery of the upper stream and the lower stream may include selecting a first mode or a second mode, wherein the first mode includes recovering the upper stream to collect separately, and recovering the lower stream to introduce the lower stream to the set of distillation columns; and wherein the second mode is recovering the lower stream to collect separately from the upper stream and recovering the upper stream to introduce the upper stream to the set of distillation columns.

In one or more embodiments, a method for selective recovery of monochlorosilane and dichlorosilane in polysilicon production process may further include reacting the collected upper stream with ammonia to produce trisilylamine or with diisopropylamine to produce diisopropylaminosilane.

In one or more embodiments, a method for selective recovery of monochlorosilane and dichlorosilane in polysilicon production process may further include further includes reacting the collected lower stream with a tertiary-butylamine to produce bis(tertiary-butylamino)silane.

In one or more embodiments, a method for selective recovery of monochlorosilane and dichlorosilane in polysilicon production process may further include reacting the collected lower stream with a diethylamine to produce bis(diethlylamino)silane.

In one or more embodiments, the recovery of the upper stream may occur at a pressure in a range of 3 bars to 7 bars and at a temperature in a range of −2° C. to 26° C. and the recovery of the lower stream may occur at a pressure in a range of 3 bars to 7 bars and at a temperature in a temperature of 42° C. to 74° C.

In one or more embodiments, the recovering the upper stream may occur at a pressure in a range of 1 bar to 16 bars and at a temperature in a range of −30° ° C. to 60° C.; and the recovering the lower stream may occur at a pressure in a range of 1 bar to 16 bars and at a temperature in a range of 8° C. to 115° C.

In one or more embodiments, o the removing the silicon tetrachloride and the trichlorosilane operation may include removing the silicon tetrachloride from the hydrogen and hydrogen chloride removed condensate in a first distillation column; and removing the trichlorosilane from the silicon tetrachloride removed results in a second distillation column.

In one or more embodiments, there is provided is a system for selectively recovering monochlorosilane and dichlorosilane in polysilicon production process including a chemical vapor deposition reactor to produce polysilicon and discharge of an exhaust gas, wherein the exhaust gas comprises hydrogen, hydrogen chloride, silicon tetrachloride, trichlorosilane, monochlorosilane and dichlorosilane; a gas recovery system to introduce the exhaust gas to separate the hydrogen and hydrogen chloride and discharge a first stream without hydrogen; a set of distillation columns to introduce the first stream to separate the silicon tetrachloride and the trichlorosilane and to discharge a second stream; and a selective distillation column to introduce the second stream and selectively discharge an upper stream and a lower stream respectively, wherein the upper stream includes monochlorosilane and the lower stream comprises dichlorosilane.

In one or more embodiments, the selective distillation column may include a top outlet and a bottom outlet, the upper stream may discharge from the top outlet, and the lower stream may discharge from the bottom outlet.

In one or more embodiments, there is provided at a pressure in a range of 3 bars to 7 bars of the selective distillation column, a temperature of the top outlet in the range of −2° C. to 26° C. and a temperature of the bottom outlet in a range of 42° C. to 74° C.

In one or more embodiments, there is provided the selective distribution column may have at a pressure in a range of 1 bar to 16 bars of the selective distillation column; the top outlet may have a temperature of said top outlet from in the range of −30° C. to 60° C.; and the bottom outlet may have a temperature of said bottom outlet from in the range of 8° C. to 115° C.

In one or more embodiments, the set of distillation columns may include at least two distillation columns to separate the silicon tetrachloride and the trichlorosilane respectively.

In one or more embodiments, a system for selectively recovering monochlorosilane and dichlorosilane in polysilicon production process may further include a reactor for reacting discharged upper stream with ammonia to produce trisilylamine or with diisopropylamine to produce diisopropylaminosilane.

In one or more embodiments, a system for selectively recovering monochlorosilane and dichlorosilane in polysilicon production process may further include a reactor to react the discharged lower stream with tertiary-butylamine to produce bis(tertiary-butylamino)silane.

In one or more embodiments, a system for selectively recovering monochlorosilane and dichlorosilane in polysilicon production process may further include a reactor to react the discharged lower stream with diethylamine to produce bis(diethlylamino)silane.

In one or more embodiments, there is provided selective recovering the monochlorosilane and dichlorosilane contained in the exhaust stream discharged from the chemical vapor deposition reactor for polysilicon production process, which were previously ignored, monochlorosilanes and dichlorosilanes may be obtained with minimal capital investment or complexity.

In one or more embodiments, the amount of monochlorosilane and dichlorosilane may include in the exhaust stream discharged from the chemical vapor deposition reactor in the process of producing polysilicon may be controlled, reduced or removed in the recycle to the polysilicon chemical vapor deposition process to avoid manufacturing lower grade polycrystalline silicon product caused by the recycling of excessive or uncontrolled amounts of monochlorosilane and dichlorosilane.

In one or more embodiments, the precursor for the semiconductor device insulating layers may be prepared using monochlorosilane and dichlorosilane which is recovered from the process of manufacturing polysilicon allowing for additional business with minimal capital investment by within a conventional polysilicon production facility.

Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of embodiments presented in the description which follows.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. In this regard, exemplary embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, exemplary embodiments are merely described below, by referring to the figures, to explain aspects of the present disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. The suffix “(s)” is intended to include both the singular and the plural of the term that it modifies, thereby including at least one of that term (e.g., the colorant(s) includes at least one colorant). The modifier “about” used in reference to quantity includes the stated value and has the meaning indicated in the context. (For example, it includes the degree of error associated with a specific amount of measurement.) The notation “+/−10%” means that the indicated measurement can be an amount of +10% from an amount of −10% of the stated value. End points of all ranges related to the same component or property may be comprehensively and independently combinable. The disclosure of a narrower or more specific range in addition to the broader range does not deny a wider range or a larger group. The streams introducing or discharging from/to each unit in the figures can be liquid or gas, or a mixture of liquid and gas, depending on the environmental condition.

FIG.1provides an illustration of a system used to recover monochlorosilane and dichlorosilane selectively using polysilicon manufacturing process in accordance with an exemplary embodiment of a system of the present disclosure.

Methods for producing high purity polysilicon include Siemens® method, Fluidized Bed Reactor method and the metal refining method. In an exemplary embodiment, a method for producing polysilicon by Siemens® method is described, but exemplary embodiments of the present disclosure are not limited thereto.

A system100according to an exemplary embodiment includes a trichlorosilane production unit (trichlorosilane producer or trichlorosilane generator)110, a trichlorosilane purification unit (trichlorosilane purifier)120, a chemical vapor deposition unit (chemical vapor deposition depositor, chemical vapor deposition device, or chemical vapor deposition assembly)130, a gas recovery unit (a gas recovery assembly or gas recovery device)140, a distillation column set (distillation column assembly)150, an ion exchange catalyst reaction unit (ion exchange catalyst reactor)160, and a selective distillation column170. Chemical Vapor deposition may be referred to as CVD.

First, approximately 99% pure metal silicon1and a chloride and hydrogen source2are supplied to the trichlorosilane production unit110and reacted to form trichlorosilane (TCS, SiHCl3). In a closed loop process, a silicon tetrachloride stream50containing silicon tetrachloride (STC, SiCl4) from the chemical vapor deposition unit130is hydrogenated to form trichlorosilane. The silicon tetrachloride stream50may also be referred to as first distillation column bottom output stream50. The trichlorosilane stream10containing trichlorosilane is introduced into the trichlorosilane purification unit120. The trichlorosilane production unit110may be a hydrochlorination system.

The trichlorosilane purification unit120purifies and distills the trichlorosilane stream10from the trichlorosilane production unit110. Then the trichlorosilane purification unit120discharges a purified trichlorosilane stream20including trichlorosilane. The purified trichlorosilane stream20of trichlorosilane and recycled hydrogen40from the gas recovery unit140is introduced into the chemical vapor deposition unit130.

There is at least one reactor and one high temperature silicon rod (not shown) arranged in the chemical vapor deposition unit130\. Silicon crystals are deposited on the surface of the high temperature silicon rod (not shown) by the hydrogen reduction (SiHCl3(TCS)+H2(Hydrogen)→Si (Silicon)+3HCl (hydrogen chloride)) and the thermal cracking reaction of trichlorosilane (4SiHCl3(TCS)→Si (Silicon)+3SiCl4+(STC)+2H2(Hydrogen)). This process results in the growth of a polycrystalline silicon rod having a gradually increasing radius and high purity polycrystalline silicon30is acquired.

However, since the thermal cracking reaction is fast and reactive to hydrogen reduction, a large amount of the by-product silicon tetrachloride is produced (SiHCl3(TCS)+HCl (Hydrogen chloride)→SiCl4(STC)+H2(Hydrogen)). Also, in a similar way, dichlorosilane (DCS, SiH2Cl2) is produced from silicon tetrachloride (2SiHCl3(TCS)→SiH2Cl2(DCS)+SiCl4+(STC)), and monochlorosilane (MCS, SiH3Cl) is produced from dichlorosilane (DCS, SiH2Cl2) (2SiH2Cl2(DCS)→SiH3Cl (MCS)+SiHCl3(TCS)). Therefore, an exhaust stream31from the chemical vapor deposition unit130contains at least a large amount of silicon tetrachloride together with unreacted hydrogen, hydrogen chloride, trichlorosilane and the other by-products monochlorosilane and dichlorosilane.

Next, this exhaust stream31from the chemical vapor deposition unit130is introduced into the gas recovery unit140. The gas recovery unit140, which includes at least one condenser and the exhaust stream31, is ultimately cooled to temperature of −40° C. or less. At this point, unreacted hydrogen and much of the hydrogen chloride remain in the gas state, and the other components remain in the condensate. The remaining condensate (condensate)41is introduced into the distillation column set150. The condensate41\ which is introduced into the distillation column set150contains at least trichlorosilane, silicon tetrachloride, monochlorosilane and dichlorosilane. The recovered hydrogen gas40is refined and returned to the chemical vapor deposition unit130, and thus reused as part of the raw material gas. The recovered hydrogen chloride gas (not shown) may be refined and returned to the trichlorosilane production unit110, and thus reused as part of the raw material gas.

The distillation column set150includes at least one distillation column. According to an exemplary embodiment, the distillation column set150includes two distillation columns (first distillation column151, second distillation column152). A distillation column is a structure that separates a mixture based on the differing boiling points of its components. It can undergo various distillation methods, such as normal pressure distillation and reduced pressure distillation, among others. Since this is a well-known concept, a detailed description will be omitted.

A condensate41is introduced into the first distillation column151and is distilled to discharge a silicon tetrachloride stream (first distillation column bottom output stream)50containing silicon tetrachloride at the bottom of the first distillation column151and discharges a first distillation column top output stream51including at least trichlorosilane, monochlorosilane and dichlorosilane at the top of the first distillation column151. The temperature of the first distillation column151is determined based on the boiling point of each material. For example, silicon tetrachloride which has a boiling point of about 58° C. at a pressure of about 1 bar, trichlorosilane which has a boiling point of about 32° C. at a pressure of about 1 bar, dichlorosilane which has a boiling point of about 8° C. at a pressure of about 1 bar, and monochlorosilane which has a boiling point of about −30° C. at a pressure of about 1 bar. Therefore, the temperature at the top of the first distillation column151is set to the distillation temperature which is set in the range of more than boiling point of dichlorosilane to less than that of trichlorosilane to recover silicon tetrachloride and trichlorosilane by distillation. For example, the distillation temperature is set preferably from about 8° C. to about 32° C. at the pressure of about 1 bar. However, the distillation temperature is not limited to those described, and may vary with pressure and composition of the mixture.

Next, the above-mentioned first distillation column top output stream51from the first distillation column151is introduced into the second distillation column152and is distilled to discharge a second distillation column bottom output stream52which contains trichlorosilane at the bottom of the second distillation column152and to discharge a second distillation column top output stream53including at least monochlorosilane and dichlorosilane at the top of the second distillation column152. The temperature at the top of the second distillation column152is set to the distillation temperature which is set in the range of more than boiling point of monochlorosilane to less than that of dichlorosilane to recover trichlorosilane by distillation. For example, the distillation temperature is set preferably from about −30° C. to 8° C. at the pressure of about 1 bar. However, the distillation temperature is not limited to those described, and may vary with pressure and composition of the mixture.

The silicon tetrachloride stream (first distillation column bottom output) stream50including recovered silicon tetrachloride of the first distillation column151is returned to the polysilicon production process and thus reused as part of the raw material for producing the polycrystalline silicon material. For example, the recovered silicon tetrachloride is returned to the trichlorosilane production unit110and thus reused as part of raw material for producing trichlorosilane. As another example, the recovered silicon tetrachloride is sent to the ion exchange catalyst reaction unit160to turn into trichlorosilane and thus returned to the polysilicon production process. Alternatively, the recovered silicon tetrachloride is returned to both the trichlorosilane production unit110and the ion exchange catalyst reaction unit160. The ion exchange catalyst reaction unit160may include an ion-exchange resin or ion-exchange polymer. An ion-exchange resin or ion-exchange polymer is a resin or polymer that acts as a medium for ion exchange. For example, a resin or polymer may be a bead-form, weak base anion exchange resin provided for the removal of specific materials from inlet streams.

The second distillation column bottom output stream52including recovered trichlorosilane and optionally dichlorosilane from the second distillation column152, which is returned to the polysilicon production process and thus reused as part of the raw material for producing the polycrystalline silicon material. For example, the recovered trichlorosilane is returned to the trichlorosilane purification unit120or the chemical vapor deposition unit130and thus reused as part of raw material for producing the polycrystalline silicon material. Alternatively, the recovered trichlorosilane is returned to the trichlorosilane purification unit120and the chemical vapor deposition unit130.

Next, according to an exemplary embodiment, the second distillation column top output stream53including at least monochlorosilane and dichlorosilane from the top of the second distillation column152introduced into the selective distillation column170and is distilled to discharge a first distillation column stream (monochlorosilane stream)71including monochlorosilane at a top of the selective distillation column170and to discharge second distillation column stream (dichlorosilane stream)72including dichlorosilane at the bottom of the column170. In the selective distillation column170, various techniques may be employed to achieve this separation. Some common methods may include the use of specific reboilers, condensers, and trays or packing materials designed to target the desired component. Additionally, specific temperatures of the top outlet and the bottom outlet may be set to receive the desired component. The distillation temperature may be set in the range from more than the boiling point of monochlorosilane to less than that of dichlorosilane. For example, the temperature of the top outlet and the bottom outlet may be set as shown in table, according to the pressure.

According to an exemplary embodiment, the temperature of the top outlet of the selective distillation column170may be set from about −2° C. to about 26° C. at a pressure from about 3 bar to about 7 bars, and the temperature of the bottom outlet of the selective distillation column170may be set from about 42° C. to about 74° C. at a pressure from about 3 bars to about 7 bars. If the pressure is greater than about 7 bars, there is more risk in the case of a loss of containment. Both monochlorosilane and dichlorosilane are pyrophoric materials and may lead to an explosion with a loss of containment. In addition, if the column is operated at too high of a pressure, separate pumps may be required to feed the stream to the selective distillation column170. In the case the pressure is less than about 3 bars, separate pumps and low temperature refrigeration system may also be required to discharge the stream from the selective distillation column170. Therefore, the above-mentioned distillation temperature is required to avoid installing additional equipment and to mitigate a loss of containment from the system.

In the selective distillation column170, monochlorosilane and dichlorosilane may be selectively recovered. The user may optionally recover either monochlorosilane or dichlorosilane, or both monochlorosilane and dichlorosilane at the same time, and output a first distillation column stream (monochlorosilane stream)71and/or second distillation column stream (dichlorosilane stream)72using the selective distillation column170.

As a result, monochlorosilane and dichlorosilane in the exhaust stream31, which has been ignored in the polysilicon manufacturing process, may be recovered by the selective distillation column170and used as a raw material to synthesize precursors for semiconductor insulating layers.

Traditionally monochlorosilane and dichlorosilane have been returned to the conventional polysilicon manufacturing process together with trichlorosilane and/or silicon tetrachloride without being recovered separately for reuse. However, dichlorosilane and monochlorosilane are more reactive material compared than trichlorosilane. So, if the amount of dichlorosilane and/or monochlorosilane becomes either too large a part of trichlorosilane feed or if dichlorosilane and/or monochlorosilane has a variable level during the course of a reactor run, the quality of polycrystalline silicon can be affected. For example, even small amounts of variation, for example less than about +/−1 mol % dichlorosilane in trichlorosilane can affect instantaneous growth rates of polysilicon crystal, gas phase nucleation, and therefore overall reactor performance. Also, high and/or variable dichlorosilane and/or monochlorosilane levels can influence dust formation in the gas phase, leading to difficulties in maintaining desired gas temperatures, shortening batch times, and overall productivity. Further, high and/or variable dichlorosilane and/or monochlorosilane levels can be associated with a lower grade polysilicon product manifested by uneven and/or porous silicon crystal growth. However, according to an exemplary embodiment, an amount of dichlorosilane and/or monochlorosilane returning to the polysilicon manufacturing process may be controlled by the selective distillation column170. Additionally, according to another exemplary embodiment, dichlorosilane and/or monochlorosilane may be removed to prevent dichlorosilane and/or monochlorosilane from being recycled to the polysilicon manufacturing process by recovering dichlorosilane and/or monochlorosilane by the selective distillation column170.

Next, according to an exemplary embodiment, the system contains the ion exchange catalyst reactor160. The recovered monochlorosilane in the first distillation column stream (monochlorosilane stream)71and/or dichlorosilane in the second column distillation steam (dichlorosilane stream72) from the selective distillation column170may be introduced into the ion exchange catalyst reactor160and reacted with recovered silicon tetrachloride in the silicon tetrachloride stream (first distillation column bottom output stream)50discharged from the distillation column set150. In the ion exchange catalyst reactor160, monochlorosilane and/or dichlorosilane may be converted to trichlorosilane by the ion exchange reaction. For example, monochlorosilane is turned into dichlorosilane and silane (2SiH3Cl (MCS)+SiCl4(STC)→3SiH2Cl2(DCS)). And dichlorosilane is reacted with silicon tetrachloride and turned into trichlorosilane (SiH2Cl2(DCS)+SiCl4+(STC)→2SiHCl3(TCS)). The produced trichlorosilane of the ion exchange catalyst reactor160is returned to the polysilicon production process and thus reused as part of the raw material for producing the polycrystalline silicon material.

According to an exemplary embodiment, the selective distillation column170may operate at least two modes.FIG.2provides an illustration of the first mode of system100used in an exemplary embodiment of a method of the present disclosure. The first mode is that only monochlorosilane in the first distillation column stream (monochlorosilane stream)71is recovered and the dichlorosilane72the second column distillation stream (dichlorosilane stream) is returned into the polysilicon production process to recycle it.

In the first mode, stream (the first distillation column stream or monochlorosilane stream)71which contains monochlorosilane discharged to the top outlet is collected separately. This monochlorosilane can be stored in a container (not shown) or sent to a trisilylamine reactor180through a pipe to react with ammonia8to form trisilylamine (3SiH3Cl (MCS)+4NH3(Ammonia)→N(SiH3)3(trisilylamine)+3NH4Cl (Ammonium chloride)) in a trisilylamine stream80discharged from trisilylamine reactor180or sent to a diisopropylaminosilane reactor181through a pipe to react with diisopropylamine18to form diisopropylaminosilane in a diisopropylaminosilane stream81discharged from diisopropylaminosilane reactor181.

Conventionally, people have used the ion exchange catalyst reaction to produce monochlorosilane which is the precursor of trisilylamine and diisopropylaminosilane (2SiH2Cl2(DCS)→SiH3Cl (MCS)+SiHC3(TCS)). However, this reaction also produces silicon tetrachloride and silane as by-product (2SiH3Cl (MCS)⇔SiH4(Silane)+SiH2Cl2(DCS) and 2SiHCl3(TCS)⇔SiH2Cl2(DCS)+SiCl4(Silane)) which are required to separate, so using this method requires extra capital expense and cost.

However, according to an embodiment, the monochlorosilane contained in the exhaust stream is recovered and used as a precursor of trisilylamine and diisopropylaminosilane. Therefore, there is no problem of waste treatment so trisilylamine or diisopropylaminosilane may be produced at lower cost than above-mentioned conventional way.

Additionally, in the first mode, the second column distillation stream72which contains dichlorosilane discharged to the bottom outlet and thus reused as part of raw material for producing polysilicon. For example, the discharged dichlorosilane can be returned to the second distillation column152, to the second distillation column outlet with stream54, to the trichlorosilane production unit110with silicon tetrachloride stream (first distillation column bottom output50, to the chemical vapor deposition unit130with ion exchange catalyst output stream60, or to the ion exchange catalyst reaction unit160to turn into trichlorosilane and thus returned to the polysilicon production process. The returning ways of dichlorosilane are not limited to those described and may vary with user's demands.

FIG.3provides an illustration of the second mode of system100used in an embodiment of a method of the present disclosure. The second mode is that only dichlorosilane in the second distillation distribution column stream72is recovered and monochlorosilane in the first distillation column stream (monochlorosilane stream)71is returned into the polysilicon production process to recycle it.

In the second mode, the second distillation distribution column stream72which contains dichlorosilane discharged to the bottom outlet is collected separately. This dichlorosilane in the second distillation distribution column72can be stored in a container (not shown) or sent to a bis(tertiary-butylamino)silane reactor190through a pipe to react with tertiary butylamine9(TBA) to form bis(tertiary-butylamino)silane (BTBAS or SiH2[CNH(CH3)3]2)(90) or sent to a bis(diethlylamino)silane reactor191through a pipe to react with diethylamine19to form bis(diethlylamino)silane91.

Additionally, in the second mode, the first distillation column stream71which contains monochlorosilane discharged to through a top outlet of the selective distillation column170and thus reused as part of raw material for producing polysilicon. The discharged monochlorosilane in the first distillation column stream71can be returned to the second distillation column152, to the trichlorosilane production unit110with silicon tetrachloride stream (first distillation column bottom output stream)50, to the chemical vapor deposition unit130with ion exchange catalyst output stream60, or to the ion exchange catalyst reaction unit160to eventually turn into trichlorosilane and thus returned to the polysilicon production process. The returning ways of monochlorosilane are not limited to those described and may vary with user's demands.

According to one or more exemplary embodiments shown inFIGS.2and3, the monochlorosilane and/or dichlorosilane is/are recovered separately through the selective distillation column170or recycled into the polysilicon process after it is converted to trichlorosilane or silicon tetrachloride. Thus, an exemplary embodiment can prevent monochlorosilane and/or dichlorosilane from being directly returned into the chemical vapor deposition unit130. In the process of an exemplary embodiment, dust occurring by monochlorosilane and/or dichlorosilane to the reactor can be prevented, and high-quality polysilicon can be produced. In addition, the recovered monochlorosilane and/or dichlorosilane can be utilized as a raw material for the precursor of the semiconductor insulating layers to generate economic profit.

According to another exemplary embodiment, various modes may be disclosed in addition to the modes disclosed in one or more exemplary embodiments shownFIGS.2and3.

For example, there may be the third mode that both monochlorosilane and dichlorosilane are recovered separately at the same time. In the third mode, the first distillation column stream (monochlorosilane stream) containing monochlorosilane is recovered from the selective distillation column170and the bottom stream (second column distillation stream or dichlorosilane stream) containing dichlorosilane is recovered simultaneously.

According to another exemplary embodiment, o the mode conversion may be performed by various methods. In an exemplary embodiment, the mode may be selected according to user's needs. For example, if the user needs to recover monochlorosilanes, the first mode can be selected by operating valves (not shown) and then monochlorosilane is recovered. If the user needs to recover dichlorosilane, the second mode can be selected by operating valves (not shown) and then dichlorosilane is recovered.

FIG.4provides an illustration of the system used in another exemplary embodiment of a method of the present disclosure.

Referring toFIG.4, the system according to another exemplary embodiment of the present disclosure further includes an adsorbent media200before the selective distillation column170.

The second distillation column top output stream53including at least monochlorosilane and dichlorosilane from the top of the second distillation column152is introduced into the adsorbent media (200). According to another exemplary embodiment of the present disclosure, the second distillation column top output stream53from the top of the second distillation column152may contain monochlorosilane, dichlorosilane and siloxane. In detail, the second distillation column top output stream53from the top of the second distillation column152may contain about 3% of monochlorosilane, about 1% of siloxane, and about 96% of dichlorosilane.

The adsorbent media200includes a packed carbon bed. The packed carbon bed may comprise carbon, in a stainless-steel exterior bed with some sort of mesh or filter on the inlet and outlet. Siloxane contamination in the second distillation column top output stream53from the top of the second distillation column152is removed by the packed carbon bed and there is no siloxane in an adsorbent media output stream201from the adsorbent media200.

The packed carbon bed may catalyze disproportionate the second distillation column top output stream53from the top of the second distillation column152into a mixture of monochlorosilane, dichlorosilane, trichlorosilane and small amounts of silicon tetrachloride while adsorbing siloxane. The act of the surface adsorption catalyzes the disproportionation by trapping a Cl or H atom, so the process may generate trichlorosilane, silicon tetrachloride, and silane. Further, the reaction mechanism catalyzed by the packed carbon media with dichlorosilane may make more monochlorosilane. Therefore, this mechanism in turn increases the quantity of monochlorsilane in the adsorbent media output stream201discharged from the adsorbent media200and the overall monochlorsilane yield for the process.

Therefore, the adsorbent media output stream201discharged from the adsorbent media200may contain monochlorosilane, dichlorosilane, trichlorosilane, silicon tetrachloride, and silane. Siloxane contaminant remains adsorbed on surface of adsorbent media200and is not present in the adsorbent media output stream201discharged from the adsorbent media200.

Next, the adsorbent media output stream201discharged from the adsorbent media200may be introduced into the selective distillation column170and is distilled to discharge a first distillation column stream71including monochlorosilane and higher boilers at the top of the selective distillation column170and to discharge the second distillation column stream72including dichlorosilane and lower boilers at the bottom of the selective distillation column170. Regarding other processes, including the use of the selective distillation column, redundant descriptions will be omitted since they are identical to the description provided inFIGS.1to3above.

FIG.5provides an illustration of the system used in the other exemplary embodiment of a method of the present disclosure.

Referring toFIG.5, the system according to the another exemplary embodiment of the present disclosure, includes a stripping tank column310and disproportionation bed320after the selective distillation column170.

The first distillation column stream71from the adsorbent media200may include monochlorosilane but also may include silane (SiH4) as a byproduct.

According to the another exemplary embodiment of the present disclosure, the first distillation column stream71including monochlorosilane and silane (SiH4) from the top of the selective distillation column170is introduced into a stripping tank column310. The stripping tank column310may be distilled to discharge a first stripping tank column discharge stream311including silane at the top of the stripping tank column310, and to discharge a second stripping tank column discharge stream312including monochlorosilane at the bottom of the stripping tank column310. The stripping tank column310may act as a product tank column. The stripping tank column310may be a small tower with a condenser on top, where the silane is stripped from the first distillation column stream71.

The stream stripping tank column discharge311from the stripping tank column310including silane is introduced into a disproportion bed320. The disproportion bed320may be a neutral ion exchange reactor used as fluid bed resin where a tetrachlorosilane stream319including tetrachlorosilane may be fed. The disproportion bed320may turn the silane into a chlorosilane mixture with an excess of tetrachlorosilane. The chlorosilane mixture including dichlorosilane, trichlorosilane, and tetrachlorosilane discharged from the disproportion bed320is shown as a disproportion bed discharge stream321inFIG.5.

The disproportion bed discharge stream321may be fed back into a polysilicon plant. The disproportion bed discharge stream321including the chlorosilane mixture may be recycled back into a column. Especially trichlorosilane, and tetrachlorosilane may be used for polysilicon manufacturing. Regarding other processes, including the use of the selective distillation column, redundant descriptions will be omitted since they are identical to the description provided inFIGS.1to4above.