KR20150082332A - A container and method of mitigating metal-contact contamination of polysilicon - Google Patents

Abstract

The present disclosure relates to the reduction or mitigation of metal-contamination of polysilicon when housed or stored in a container having a polysilicon contact surface that is at least partially composed of metal and / or is at least partially metal. In particular, the present invention relates to a method for alleviating metal contamination of polycrystalline silicon due to contact with a metallic surface of a container by providing a protective liner comprising an ultra-fine elastomeric polyurethane on the metal surface of the container.

Description

Technical Field [0001] The present invention relates to a container and a method for mitigating metal contact contamination of polysilicon,

[Cross reference of related application]

This application claims the benefit of U.S. Provisional Application No. 61 / 724,844, filed on November 9, 2012, the entire contents of which are incorporated herein by reference.

[TECHNICAL FIELD]

The present disclosure relates to a modified container for polysilicon and a method for mitigating metal contamination of the polysilicon contained therein.

Ultra-high purity silicon is widely used in the electronics and photovoltaic industries. The purity required in industry for these applications is extremely high, and it is often considered acceptable to have only trace amounts of contamination when measured at the ppb level. Although it is possible to produce such high purity polycrystalline silicon by extreme control of the purity of the reactants used in the production of polycrystalline silicon, extreme care must be taken in any handling, packaging or transport operations to avoid post pollution thereafter . There is a risk of contamination of the polycrystalline silicon due to the surface material at all moments when the polycrystalline silicon contacts the surface. If the degree of contamination exceeds a predetermined industry standard, the ability to sell the material in this final application should be limited or even rejected. In this respect, if silicon performance standards are to be met in the semiconductor industry, minimizing contact metal contamination is a major challenge.

There is a need to provide a container that can solve the problem of preventing metal contact contamination while at the same time having an improved service life and preventing frequent replacement of the container and / or the necessity of replacing the resin member.

According to one aspect, the present disclosure relates to a method for reducing or eliminating contamination of granular polysilicon due to contact with an inner metal surface of a container during storage or transportation, Placing a polysilicon in a container provided with a protective liner comprising an ultrafine elastomeric polyurethane on a portion of the liner being positioned such that the polysilicon is shielded from contact with the inner metal surface.

According to another aspect of the present invention, this disclosure relates to a container suitable for receiving granular polysilicon. Wherein the container is a container having an inner metal surface that is at least partially composed of metal and defines a region containing polysilicon wherein the portion of the inner surface that is in contact with the polysilicon is coated with a protective liner comprising an ultrafine elastomeric polyurethane Thereby reducing or eliminating metal contamination of the polysilicon.

According to another aspect, the present disclosure relates to articles comprising:

a) a container suitable for receiving granular polysilicon, said container having an inner metal surface defining an area for receiving the polysilicon, and a protective liner containing an ultrafine elastomeric polyurethane on a portion of said inner metal surface ; And

b) granular polysilicon located within the vessel, the polysilicon contacting the protective liner, thereby reducing or eliminating metal contamination of the polysilicon.

The foregoing and other objects, features and advantages will become more apparent from the following detailed description.

Figure 1 is a schematic cross-sectional view of a lined container suitable for receiving polysilicon.
Figure 2 is a schematic perspective view of a liner-loaded hopper and discharge chute suitable for receiving and discharging polysilicon.

Unless otherwise indicated, all numbers and ranges recited in this application are approximations, i. E., Within the scientific uncertainty values in the tests necessary to measure these numbers and ranges, as known to those skilled in the art.

The expression "storage container" in the context of this specification is defined as a bin, a drum, a chute, a hopper having a polysilicon contact surface that is at least partially metallic and / ) Or a crushing bed. The container may be associated with the processing and manufacturing operations of the polysilicon and / or the packaging and transport of the polysilicon. The container may be a commercially available article in which the polysilicon is contained within the container.

The polysilicon contained in the vessel is not limited to any particular source and may include particulate or granular silicon used as a seed in a fluidized bed reactor process for producing polysilicon or a product harvested from the process. The polysilicon contained in the vessel may also be one obtained from the Siemens process and may be in the form of a silicon dendrite obtained according to the method disclosed in US Patent Publication No. US2003 / 0150378.

In one embodiment, the polysilicon storage vessel is a vessel for use in polysilicon associated with a fluidized bed fabrication process of crystalline polysilicon, typically granular or granular silicon. Granular silicon includes materials with a maximum dimension of an average size of from about 0.01 micron to 15 millimeters. More typically, most of the granular silicon has an average particle size of about 0.1 to about 5 millimeters, and essentially does not have any sharp or sharp edge structure in the form of a spheroid.

Metal contamination of the silicon contained in the container is caused by direct contact of the silicon with the metal surface or by entrainment of corrosion or wear products as discrete metal particles in a large amount of silicon mass (e.g., particulate polysilicon) . In the disclosed embodiment, the contamination can be reduced or prevented by the presence of a protective liner at least partially covering at least one inner metal surface of the container, wherein the protective liner comprises an ultrafine elastomeric polyurethane. In the context of the present application, the term "polyurethane" may also include materials wherein the polymer backbone comprises polyurethane or polyurethane-isocyanurate linkages. In some embodiments, at least 50% or at least 75% of the surface is covered by the protective liner disclosed herein. In certain embodiments, the surface is completely covered with a protective liner. "Completely" should be regarded as essentially absent from a practical point of view. When polysilicon is added to the container, the polysilicon contacts the protective liner instead of the bare metal surface.

Figure 1 is a schematic cross-sectional view of an exemplary polysilicon storage container 10 that includes a container 20 that is at least partially metallic in configuration and a protective covering 20 that at least partially covers at least one interior surface 22 of the container 20. [ Liner < / RTI > Particulate or granular polysilicon 40 located in the vessel 20 is in contact with the protective liner 30.

FIG. 2 is a schematic perspective view of an exemplary polysilicon container system 100, including a storage hopper 11 and a discharge chute 120. One or both of the storage hopper 110 and the chute 120 are at least partially constructed of metal. A protective liner 130 at least partially covers at least one inner metal surface 112 of the hopper 110 and / or at least partially covers one or more inner metal surfaces 122 of the chute 120. A particulate or granular polysilicon 140 is positioned within the hopper 110 and chute 120 and contacts the protective liner 13.

The term "elastomeric " refers to a polymer having elastic properties, such as, for example, a vulcanized natural rubber. Thus, the elastomeric polymer can be stretched, but shrinks to almost the original length and shape upon release.

The term "ultrafine" refers generally to a foam structure having a pore size in the range of 1-100 [mu] m. Typically, the ultrafine material appears to be a normal-looking solid without any distinguishable network structure unless viewed with a high magnification microscope. For elastomeric polyurethanes, the term "ultrafine" is typically defined by density, such as an elastomeric polyurethane having a bulk density of greater than 600 kg / m 3. Polyurethanes with lower bulk densities typically begin to acquire a reticular pattern and are therefore generally less suitable for use as the protective coatings described herein.

The ultrafine elastomeric polyurethane suitable for use in the present application has a bulk density of 1150 kg / m3 or less and a Shore hardness of 65 A or greater. In one embodiment, the elastomeric polyurethane has a Shore hardness of 90 A or less, such as 85 A or less, and 70 A or more. Thus, the Shore hardness may be 65A to 90A, e.g., 70A to 85A. In addition, a suitable elastomeric polyurethane has a bulk density of at least 600 kg / m 3, such as at least 700 kg / m 3, more preferably at least 800 kg / m 3; 1150 kg / m 3 or less, for example, 1100 kg / m 3 or less, or 1050 kg / m 3 or less. Thus, the bulk density may range from 600-1150 kg / m 3, for example 800-1150 kg / m 3 or 800-1100 kg / m 3. The bulk density of the solid polyurethane is understood to be in the range of 1200-1250 kg / m3. In one embodiment, the elastomeric polyurethane has a Shore hardness of 65 A to 90 A and a bulk density of 800 to 1100 kg / m 3.

The elastomeric polyurethane may be a thermosetting or thermoplastic polymer; The presently disclosed application is more suitable for use with thermosetting polyurethanes. Ultrafine elastomeric polyurethanes with the above physical properties appear to be particularly rigid and are particularly resistant to abrasive environments and the exposure of particulate granular silicon to a number of other materials.

The protective liner or coating on the inner metal surface of the container may have a total thickness of at least 0.1 millimeter, such as at least 0.5 millimeter, at least 1.0 millimeter, or at least 3.0 millimeters, such as less than 10 millimeters, such as 7 millimeters or less, ≪ / RTI > Thus, embodiments of the disclosed protective liner may have a thickness of 0.1 to 10 mm, such as 0.5-7 mm or 3-6 mm. The protective liner may be a plastic laminate structure comprising an outer polyurethane lamella in contact with the silicone. However, in one embodiment, most or all of the protective liner is considered an elastomeric ultra-fine polyurethane.

Disposing the protective liner in the container comprises: obtaining the elastomeric ultrafine polyurethane in sheet form; Cutting said sheet to form at least one portion shaped to match the internal size and contour of the pupil of said container; Coating at least a portion of the metal inner surface of the vessel with an adhesive; And contacting the adhesive with the polyurethane sheet to form a metal / adhesive / polyurethane laminate structure. In another embodiment, the adhesive is applied to the outer surface of the polyurethane material (i.e., the surface facing the inner metal surface of the container), and the polyurethane / adhesive contacts the inner metal surface of the container. In another embodiment, the adhesive is applied to both the inner metal surface and the surface of the polyurethane material. Preferably, the adhesive is chosen to be miscible with the metal and polyurethane, and provides adequate adhesion to prevent subsequent peeling and / or deterioration. Suitable adhesives include, but are not limited to, polyurethane, isocyanate or epoxy adhesive. Optionally, the metal surface in contact with the adhesive and / or the back surface of the polyurethane sheet may be roughened and / or treated with a primer material to improve the integrity and strength of the adhesive bond.

In other embodiments, for example, where the internal contour and shape of the container is complex, the placement of the ultra-fine polyurethane protective liner may be accomplished by spray-coating techniques. In this technique, the precursor material for the polyurethane is introduced in the same way, directly sprayed onto the exposed metal surface as a reactive material, and the desired protective liner is provided by reaction and curing. The preparation of the protective liner in this way provides the advantage of good adhesion of the polyurethane to the metal surface while preventing the seam problem inherent in the arrangement method involving the above-mentioned cutting sheet. An alternative application to spray coating is in situ casting of polyurethane, which has the additional advantage of providing an article having a substantially smooth, continuous polyurethane surface.

Processes for preparing ultrafine polyurethane elastomers are well known to those skilled in the art and generally comprise reacting polyisocyanates with polyether polyols to produce polyether polyol polyurethanes ("PE-PU"), or alternatively polyisocyanates ("Pst-PU") by reaction with a polyester polyol. Polyester polyol-based polyurethane elastomers are typically elastomeric polyurethanes that are observed to have physical properties more suitable for the present application than polyether polyol-based oligourethane elastomers and are therefore more preferred for use in the present application. Exemplary publications that teach the preparation of ultrafine polyurethane elastomers include: US 4,647,596; US 5,968,993; US 5,231,159; US 6,579,952; US2002 / 111,453 and US2011 / 003103. Methods of making polyurethane lined metal articles are also known to those skilled in the art and are described in US 2005/189, 028; GB 2,030,669; US 5,330,238; Or JP52-20452, all of which are incorporated herein by reference. Processes for making polyurethanes or polyurethane-ureas and for producing articles containing them by spraying techniques are also known to those skilled in the art and are described in US2008 / 305,266; WO2012 / 005351; US 6,399,736; US 6,747,117; US 7,736,745; And US 6,730,353.

Such polyurethane liner containers can satisfactorily alleviate metal contamination of the granular polysilicon during storage and / or transport of the granular polysilicon. The abrasive deterioration or cracking of the polyurethane lining during transport of the granular polysilicon is very low or absent. It is observed that the organic or carbon contamination of the polysilicon is also minimized so as not to degrade the overall quality of the polysilicon.

The particular embodiments included in this specification are for illustrative purposes only and should not be considered as limiting the specification.

Example  One:

The advantage of the selection of ultrafine elastomeric polyurethane for other potential liner materials as protective liners of the containers is demonstrated by studying the abrasion resistance of potential liner materials. Wear is considered the most likely deterioration of the protective liner. Thus, an accelerated abrasion wear test was used to confirm material selection.

The accelerated abrasion test of various plastic resins considered as potential candidates for use as the protective coating layer of the present application was performed. The test method is designed to mimic the requirements that may arise in typical operations involving the manufacture, transport and storage of granular polysilicon. A general method consists of performing abrasive impact etching on a plastic resin coupon (3 "x 3" x 0.5 "(7.6 x 7.6 x.1.3 cm) with particulate polysilicon and observing the change of the coupon surface after a predetermined time The particulate or granular polysilicon used consists essentially of smooth spheroid spherical particles with an average (95%) particle size of 0.9-1.2 mm. The polysilicon particles operate at a pressure of about 15 psi (103,420 Pa) Is conveyed by a jet stream assumed to confer a particle velocity of 45 to 55 feet / sec (13.7-16.8 m / s), thereby causing an impact on the large surface of the plastic coupon, focusing on the midpoint. The orientation of the airflow was designed to provide a predetermined fixed impact angle to the coupon surface. This arrangement was used to pass the coupon surface to a passage of granular polysilicon material of about 24 kg / hour The wear and friction losses on the coupon are observed by the formation of the surface craters and the depth of the craters is measured after a set of consecutive exposure times to the polysilicon.

Table 1 below shows the observations; It is evident that the elastomeric polyurethane has better performance as evidenced by reduced crater formation.

Comparative Example 1 Comparative Example 2 Example 1 Example 2 Coupon Material Polypropylene Ethylene-tetrafluoroethylene Polyurethane elastomer (polyether polyol type) Polyurethane elastomer (polyester polyol type) density
(Kg / m3) 900 1700 1100 1100 Shore hardness 67 D 67 D 80A 74A Exposure time
(minute) 1500 1500 1500 1500 1500 1500 1500 1500 Impact strength
(Degree) 15 30 15 30 15 30 15 30 Crater depth (cm) 0.46 cm 1.3 cm
Excess Not observed 1.0 cm 0.10 cm 0.13 cm <0.025 cm 0.025 cm

While the foregoing discussion has focused on the implementation of linered containers for the storage and / or transport of polysilicon, there are other materials that are important in the semiconductor industry, such as germanium, where similar management It will also be appreciated by those of ordinary skill in the art that a great need exists.

A method for reducing or eliminating contamination of granular polysilicon due to contact with an inner metal surface of a container during storage or transportation comprises the steps of providing a protective coating comprising at least a portion of an inner metal surface of the container, And placing the granular polysilicon in a container provided with a liner, wherein the liner is disposed such that the granular polysilicon is shielded from contact with the inner metal surface. In some embodiments, the polyurethane has a Shore hardness of 65 A to 90 A and a bulk density of 800 to 1150 kg / m 3.

In any or all of the embodiments, the protective liner may have a total thickness of 0.1 to 10 millimeters. In any or all of the above embodiments, the granular polysilicon may be in the form of an essentially spheroidal shape with an average dimension with a maximum dimension of 0.01 micron to 15 millimeters, and may not have a sharp or sharp edge structure.

A container suitable for receiving granular polysilicon, the container having a container having an inner metal surface defining a region containing granular polysilicon; And a protective liner comprising an ultrafine elastomeric polyurethane on at least a portion of the inner metal surface facing the area, wherein when the granular polysilicon is in the area, And the polyurethane is a vessel having a Shore hardness of 65 A to 90 A and a bulk density of 800 to 1150 kg / m 3. In some embodiments, the protective liner has a total thickness of 0.1 to 10 millimeters. In any or all of the embodiments, the granular polysilicon may be essentially spheroidal in shape with an average size with a maximum dimension of 0.01 micron to 15 millimeters, and may be essentially free of sharp or sharp edge structures .

A method of making a container, the method comprising: placing a protective liner comprising an ultrafine elastomeric polyurethane within a container comprising an inner metal surface, thereby covering at least a portion of the inner metal surface with the protective liner . In one embodiment, the step of disposing the protective liner in the container comprises: (a) spray coating the polyurethane onto the portion of the inner surface; or (b) forming the protective liner by in situ casting . In another embodiment, the step of disposing the protective liner in the container comprises the steps of (i) obtaining an elastomeric ultrafine polyurethane sheet, (ii) cutting the sheet to form a protective liner defined by the inner metal surface of the container (Iii) coating the metal inner surface of the container with an adhesive; and (iv) applying the at least one elastomeric ultrafine polyurethane portion to the at least one elastomeric &lt; RTI ID = Contacting the ultrafine polyurethane portion with the adhesive to form a metal / adhesive / polyurethane laminate structure. In yet another embodiment, the step of disposing the protective liner in the container comprises the steps of: (i) obtaining an elastomeric ultrafine polyurethane sheet; (ii) cutting the sheet, (Iii) coating the outer surface of the at least one polyurethane portion with an adhesive to form one or more adhesive-coated (at least one) elastomeric ultrafine polyurethane portion Forming a polyurethane portion; and (iv) contacting the at least one adhesive-coated polyurethane portion with an inner metal surface of the container to form a metal / adhesive / polyurethane laminate structure.

A) a container suitable for receiving polysilicon, the container having an inner metal surface defining a region containing polysilicon, wherein at least a portion of the inner surface is covered with a protective liner comprising an ultrafine elastomeric polyurethane And b) granular polysilicon located within the container, wherein the polysilicon comprises granular polysilicon, wherein contact with the inner metal surface is blocked by the protective liner. In some embodiments, the granular polysilicon is essentially spheroidal in shape with an average size with a maximum dimension of 0.01 micron to 15 millimeters and is essentially free of sharp or sharp edge structures.

It should be appreciated that in view of the many possible implementations to which the principles of the present disclosure apply, the illustrated implementations are only preferred examples and should not be construed as limiting the scope of the present disclosure. Rather, the scope of the disclosure is defined by the following claims.

Claims (13)

A method for reducing or eliminating the contamination of granular polysilicon due to contact with the inner metal surface of a container during storage or transportation, said method comprising the step of applying an ultrafine elastomeric polyurethane on at least a portion of the inner metal surface of said container Disposing a granular polysilicon in a container provided with a protective liner, wherein the liner is positioned such that the granular polysilicon is shielded from contact with the inner metal surface. The method of claim 1, wherein the polyurethane has a Shore hardness of 65 A to 90 A and a bulk density of 800 to 1150 kg / m 3. 3. The method of claim 1 or 2, wherein the protective liner has a total thickness of 0.1 to 10 millimeters. 3. The method of claim 1 or 2, wherein the granular polysilicon is essentially spheroidal in shape with an average size with a maximum dimension of between 0.01 micron and 15 millimeters and is free of sharp or sharp edge structures. A container suitable for receiving granular polysilicon, the container comprising:
A container comprising an inner metal surface defining a region containing granular polysilicon; And
A protective liner comprising an ultrafine elastomeric polyurethane on at least a portion of said inner metal surface facing said area,
Said granular polysilicon contacting said protective liner when said granular polysilicon is in said region, said polyurethane having a Shore hardness of 65A to 90A and a bulk density of 800 to 1150 kg / m3. 6. The container of claim 5, wherein the protective liner has a total thickness of from 0.1 to 10 millimeters. 7. The container of claim 5 or 6, wherein said granular polysilicon is essentially spheroidal in shape with an average size with a maximum dimension of between 0.01 micron and 15 millimeters and is essentially free of sharp or sharp edge structures. 7. A method of making a container as claimed in claim 5 or claim 6, wherein the method comprises disposing a protective liner comprising an ultrafine elastomeric polyurethane in a container comprising an inner metal surface, whereby at least a portion of the inner metal surface Covering with a protective liner. The method of claim 8, wherein disposing the protective liner within the container comprises: (a) spray coating polyurethane onto the portion of the inner surface; or (b) forming the protective liner by in situ casting. &Lt; / RTI &gt; 9. The method of claim 8, wherein the step of disposing the protective liner within the container comprises:
Obtaining an elastomeric ultrafine polyurethane sheet;
Cutting said sheet to form at least one elastomeric ultrafine polyurethane portion shaped to match the internal size and contour of said region defined by said internal metal surface of said container;
Coating the inner metal surface of the vessel with an adhesive; And
Contacting the at least one elastomeric ultrafine polyurethane portion with the adhesive to form a metal / adhesive / polyurethane laminate structure. 9. The method of claim 8, wherein the step of disposing the protective liner within the container comprises:
Obtaining an elastomeric ultrafine polyurethane sheet;
Cutting said sheet to form at least one elastomeric ultrafine polyurethane portion shaped to match the internal size and contour of said region defined by said internal metal surface of said container;
Coating an outer surface of the at least one polyurethane portion with an adhesive to form at least one adhesive-coated polyurethane portion; And
Contacting the at least one adhesive-coated polyurethane portion with an inner metal surface of the container to form a metal / adhesive / polyurethane laminate structure. a) a container suitable for receiving polysilicon, the container having an inner metal surface defining a region containing polysilicon, wherein at least a portion of the inner surface is provided with a protective liner comprising an ultrafine elastomeric polyurethane A container; And
b) granular polysilicon located within the vessel, wherein the polysilicon is blocked by contact with the inner metal surface by the protective liner. 13. The article of claim 12, wherein the granular polysilicon is essentially spheroidal in shape with an average size with a maximum dimension of 0.01 micron to 15 millimeters and is essentially free of sharp or sharp edge structures.

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