Process for purifying iodosilane

Abstract

A method is provided for purifying iodosilanes, such as diiodosilane, in which trace amounts of certain metal ion contaminants are removed, thus providing certain liquid compositions comprising iodosilanes, which may be advantageously used in the deposition of silicon-containing films on microelectronic device substrates.

Description

[Technical field]

[0001] The present invention is in the field of vapor phase deposition of microelectronic device substrates. More particularly, the present invention relates to a method for purifying diiodosilane, which is useful as a precursor in the atomic layer deposition of silicon dioxide films. [Background technology]

[0002] Low temperature deposition of silicon-based thin films is of fundamental importance to modern semiconductor device manufacturing and processing. For decades, SiO2 thin films have been utilized as essential structural components of integrated circuits (ICs), including microprocessors, logic and memory-based devices. SiO2 is a common material in the semiconductor industry and is used as the insulating dielectric material for virtually all commercially available silicon-based devices. SiO2 has been used for many years as an interconnect dielectric, capacitor, and gate dielectric material.

[0003] The conventional industrial approach to deposit high purity SiO2 films has been to utilize tetraethyl orthosilicate (TEOS) as a thin film precursor for the vapor deposition of such films. TEOS is a stable liquid material that has been used as a silicon source reagent in chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD) and atomic layer deposition (ALD) to achieve high purity thin films of SiO2. Other thin film deposition methods (e.g., focused ion beam, electron beam and other energetic means to form thin films) can also be performed using this silicon source reagent.

[0004] As integrated circuit device dimensions continue to decrease with corresponding advances in lithographic scaling methods and shrinking device geometries, new deposition materials and processes are accordingly required to form high integrity SiO2 thin films. SiO2 films, as well as other silicon-containing thin films, such as Si3N4, SiC, and doped SiO2 films, can be deposited at low temperatures, e.g., temperatures below 400°C. x Improved silicon-based precursors (and co-reactants) are desired for forming high-k thin films.

[0005] Also, achieving low temperature films requires the use and development of deposition processes that ensure the formation of uniform, conformal silicon-containing films. Thus, while chemical vapor deposition (CVD) and atomic layer deposition (ALD) processes are refined and implemented, reactive precursor compounds are sought that are stable in handling, vaporization, and transport to the reactor, but that exhibit the ability to decompose cleanly at low temperatures to form the desired thin films. A fundamental challenge in this endeavor is achieving a balance between the thermal stability of the precursor and its suitability for high purity, low temperature film growth processes.

[0006] Halosilanes are useful as precursors in the manufacture of microelectronic devices; in particular, halosilanes such as H2SiI2 and HSiI3 are useful as precursor compounds for the deposition of silicon-containing films used in the manufacture of microelectronic devices. Current solution-based synthesis methodologies describe the synthesis of H2SiI2 and other selected iodosilanes from (i) arylsilanes (Keinan et al., J. Org. Chem., Vol. 52, No. 22, 1987, pp. 4846-4851; Kerrigan et al., U.S. Pat. No. 10,106,425) or (ii) halosilanes such as SiH2Cl2 (U.S. Pat. No. 10,384,944).

[0007] Keinan et al. describe a synthetic methodology using stoichiometric treatment of arylsilanes, phenyl-SiH3, with iodine in the presence of a catalyst such as ethyl acetate to form SiH2I2. The reaction by-products are aromatic functional groups from the arylsilane released as benzene, and a complex by-product mixture resulting from ethyl acetate decomposition. The cumbersome separation of the reaction by-products from the desired SiH2I2 complicates the process. Additionally, arylsilane-based methods for preparing halosilanes typically produce products contaminated with iodine and / or hydrogen iodide, which are detrimental to the desired iodosilane product, and therefore antimony, silver, or copper are often utilized to stabilize the iodosilane product.

[0008] As mentioned above, diiodosilane is a useful precursor compound for atomic layer deposition of silicon-containing films on microelectronic device substrates, especially silicon dioxide.In such applications, it is highly advantageous for the precursor compound to be as free of impurities as possible, since trace metals cause the diiodosilane to degrade over time.Therefore, there is still a need to purify halosilanes, such as diiodosilane, so that their use as vapor deposition precursor compounds and their effective storage can be optimized. Summary of the Invention

[0009] In summary, the present invention provides a method for purifying various iodosilanes. In this method, trace amounts of certain metal ion contaminants are removed, and a certain liquid composition containing iodosilane is provided, which can be advantageously used for depositing silicon-containing films on microelectronic device substrates. In one aspect, the present invention provides a method for removing one or more metals and / or metal ions from a liquid composition, wherein the liquid composition comprises an iodo-substituted silane selected from monoiodosilane, diiodosilane, triiodosilane, tetraiodosilane, monoiododisilane, diiododisilane, triiododisilane, tetraiododisilane, pentaiododisilane, and hexaiododisilane, and the method comprises contacting a filter material with a liquid composition comprising an iodo-substituted silane having one or more metals and / or metal ions as impurities, and the filter material comprises at least one hydrophilic functional group, thereby reducing the amount of one or more metals or metal ions in the liquid composition. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a process flow diagram illustrating the operation of one embodiment of the present invention. [Diagram 2] 1 is a graph of assay (%) of diiodosilane versus time (weeks) showing the (stability) performance of purified diiodosilane samples at different filtration temperatures versus a control sample. In the accompanying legend, RT no filtration refers to a control (i.e., unfiltered) sample of diiodosilane at room temperature. RT with filtration refers to a room temperature sample purified according to the present invention. Similarly, "40" refers to the corresponding sample maintained at 40° C. and "60" refers to the corresponding sample maintained at 60° C. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally used in its sense including "and / or" unless the content clearly dictates otherwise.

[0012] The term "about" generally refers to a range of numbers that are considered equivalent to a recited value (e.g., having the same function or result). In many instances, the term "about" may include numbers that are rounded to the nearest significant figure.

[0013] Numeric ranges expressed using endpoints include all numbers subsumed within that range (eg 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

[0014] Filters are used to remove unwanted materials from useful fluid streams and have become an important feature in a wide variety of industrial technologies. Fluids that are treated to remove unwanted materials include water, liquid industrial solvents and process fluids, industrial gases used in manufacturing or processing, and liquids with medical or pharmaceutical uses. Unwanted materials removed from fluids include impurities and contaminants, such as particles, microorganisms, and dissolved chemical species. Specific examples of filter applications include their use with liquid materials for semiconductor and microelectronic device manufacturing.

[0015] Filters can remove unwanted materials in a variety of different ways, for example, by size exclusion, or by chemical and / or physical interaction with the material. Some filters are dictated by the structural material that provides the filter with a porous structure, and the filter can capture particles of a size that cannot pass through the pores. Some filters are dictated by the ability of the structural material of the filter, or the chemical properties associated with the structural material, to associate and interact with materials passing on or through the filter. For example, the chemical characteristics of the filter can allow for association with unwanted materials from the stream passing on the filter, and capture those unwanted materials, for example, by ionic, coordination, chelating, or hydrogen bonding interactions. Some filters can utilize both size exclusion and chemical interaction characteristics to remove materials from the filtered stream.

[0016] In some cases, to perform the filtering function, the filter includes a filter membrane, which is responsible for removing unwanted materials from the fluid passing through. The filter membrane may be in the form of a flat sheet, which may be rolled (e.g., spirally), flat, pleated, or disk-shaped, as required. The filter membrane may alternatively be in the form of a hollow fiber. The filter membrane may be housed or otherwise supported within a housing such that the fluid being filtered enters through the filter inlet and must pass through the filter membrane before passing through the filter outlet.

[0017] As used herein, a "filter" refers to an article having a structure that includes a filter material. For example, a filter may be in any form useful for a filtration process, including, for example, in the form of a porous nonwoven membrane.

[0018] The filter may be of any desired form suitable for filtration applications. The material forming the filter may be a structural component of the filter itself, providing the filter with the desired structure. The filter may be porous and may be of any desired shape or configuration. The filter itself may be a single item, such as a non-woven fibrous membrane, or may be represented by multiple individual items.

[0019] In some embodiments, the filter material is formed from a polymeric material, a mixture of different polymeric materials, or polymeric and non-polymeric materials. In certain embodiments, the polymeric material is in the form of a non-woven fiber that forms a membrane. The polymeric materials forming the filter may be cross-linked to each other to provide a filter structure with a desired degree of integrity. Such polymeric materials form a backbone of hydrophobic (e.g., ion-exchange) functional groups that function to actively filter metal ion contaminants.

[0020] Polymeric materials that can be used to form the filter material of the presently disclosed filters include a variety of polymers. In some embodiments, the filter material is a membrane and includes a polyolefin or a halogenated polymer. Exemplary polyolefins include polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polybutene (PB), polyisobutylene (PIB), and copolymers of two or more of ethylene, propylene, and butylene. In further specific embodiments, the filter material includes ultra-high molecular weight polyethylene (UPE). UPE filter materials, such as UPE membranes, typically have a molecular weight of about 1×10 6 Daltons (Da) or more, e.g., about 1 × 10 6 ~9×10 6 Da, or 1.5 × 10 6 ~9×10 6It is formed from a resin having a molecular weight (weight average molecular weight) in the Da range. Crosslinking between polyolefin polymers such as polyethylene can be promoted by the use of heat or crosslinking chemicals, such as peroxides (e.g., dicumyl peroxide or di-tert-butyl peroxide), silanes (e.g., trimethoxyvinylsilane), or azoester compounds (e.g., 2,2'-azo-bis(2-acetoxy-propane). Exemplary halogenated polymers include polytetrafluoroethylene (PTFE), polychlorotrifluoro-ethylene (PCTFE), fluorinated ethylene polymers (FEP), polyhexafluoropropylene, and polyvinylidene fluoride (PVDF).

[0021] In other embodiments, the filter material comprises a polymer selected from ultra-high molecular weight polyethylene, polyamide, polyimide, polysulfone, polyether-sulfone, polyarylsulfone polyacrylate, polymethacrylate, polyester, cellulose, cellulose ester, polycarbonate, polystyrene, poly(styrene-divinylbenzene), or combinations thereof. In one embodiment, the filter material is poly(tetrafluoroethylene).

[0022] In other embodiments, the filter may be a composite filter constructed using a first filter membrane of the present disclosure in combination with a filter membrane that is different from the first filter membrane.

[0023] The filter material may be made of any suitable material or combination of materials. As mentioned above, an exemplary filter material may include one or more polymers. Furthermore, the material of the filter may have a suitable chemical property for the attachment of hydrophilic groups by grafting or by coating with a coating having such hydrophilic groups. In one embodiment, the hydrophilic groups are selected from acid, base, and ionic groups. In another embodiment, the hydrophilic groups are ion-exchange groups.

[0024] For example, sulfonic acid functional groups can be introduced into the surface of a filter material (e.g., a filter membrane) by immersing the material in a mixture of monomer solutions containing 0.3% Irgacure 2959 (UV catalyst), acrylamidomethylpropanesulfonic acid (AMPS), methylenebisacrylamide (MBAm) crosslinker, methanol, and water, and then exposing the thus-coated filter material to ultraviolet radiation to cause curing (i.e., crosslinking) of the coating. Thus, the filter material thus prepared will have sulfonic acid functional groups. Similarly, a filter membrane having phosphonic acid groups can be prepared utilizing vinylphosphonic acid as a reactive monomer.

[0025] Porous polymer membranes with ion exchange moieties on the polymer surface can remove metal and metal ion contaminants in the solution passing through the membrane, as well as any material that is too large in size to pass through the pores of the membrane. For example, commercially available ion exchange filters such as Protego® Plus DI (Entegris, Inc.) can be utilized. Other examples of commercially available membranes useful in the methods of the present invention include those sold by ASTOM Corporation and Membranes International Inc.

[0026] In one embodiment, the membrane comprises at least one such ion exchange group by type or structure, although it will be understood that the number of such ion exchange groups and their filtration characteristics can be adjusted to suit the desired purity of the resulting purified liquid composition comprising the halogen-substituted silane.

[0027] In one embodiment, the functionalized membrane is based on hydrophilic functionalized nonwoven fabric produced by graft polymerization. This type of membrane has a higher density of ion exchange groups on the surface of the medium, which makes ion exchange work effectively. The raw materials used to prepare diiodosilane contain trace amounts of polyvalent metal impurities such as Al, Ca, Cr, Au, Fe, Ni, Na, Ti, and Zn, which have the tendency to form metal ions or charged colloids. The membrane of the present invention efficiently captures such metal ions and microcolloids through electrostatic interactions.

[0028] In this regard, iodo-substituted silanes, such as diiodosilane compositions, can be purified to remove virtually all metal cations that contribute to undesirable disproportionation reactions over time (i.e., during storage), as described above. In the practice of the present invention, the diiodosilane composition to be purified is contacted with or passed through a membrane of the present invention to remove undesirable metal cation contaminants, such as Al, Ca, Cr, Au, Fe, Ni, Na, Ti, and Zn. The diiodosilane composition can be utilized neat or as a dilute solution in an inert solvent, such as pentane, hexane, and heptane.

[0029] Thus, in a first aspect, the present invention provides a method for removing one or more metals and / or metal ions from a liquid composition, the liquid composition comprising an iodo-substituted silane selected from monoiodosilane, diiodosilane, triiodosilane, tetraiodosilane, monoiododisilane, diiododisilane, triiododisilane, tetraiododisilane, pentaiododisilane, and hexaiododisilane, the method comprising contacting a filter material with a liquid composition comprising an iodo-substituted silane having one or more metals and / or metal ions as impurities, the filter material comprising at least one hydrophilic functional group; thereby reducing the amount of one or more metals or metal ions in the liquid composition.

[0030] In one embodiment, the iodo-substituted silane is a diiodosilane. In one embodiment, a liquid composition including a diiodosilane is passed through a filter material.

[0031] In one embodiment, the method of the present invention provides a liquid composition comprising diiodosilane containing about 100 to about 1000 ppb of a metal selected from Al, Ca, Cr, Au, Fe, Ni, Na, Ti, and Zn. In another embodiment, about 40 to about 90 weight percent of metal and / or metal ion contaminants are removed.

[0032] In another aspect, the present invention provides a purified liquid composition comprising a halogen-substituted silane subjected to the method of the present invention, which thus results in a purified iodosilane composition having parts per billion levels of various metal impurities, which composition exhibits superior stability during storage compared to a control sample. In one embodiment, such a purified composition comprises about 100 to about 500 ppb total of metals selected from Al, Ca, Cr, Au, Fe, Ni, Na, Ti, and Zn. In one embodiment, the liquid composition comprises a diiodosilane. In another embodiment, the liquid composition comprising a diiodosilane contains about 100 ppb or less total of metals selected from Ca, Cr, Fe, Ni, and Ti. In another embodiment, the liquid composition comprising a diiodosilane contains about 50 ppb or less total of metals selected from Ca, Cr, Fe, and Ni.

[0033] In this regard, references to metals in this disclosure are to their corresponding cations, i.e., Al +3 , Ca +2 , Na + , Fe +2 and Fe +3 , and Ni +2 is also intended to include.

[0034] Figure 1 shows a process flow diagram of one embodiment of the present invention in RM tank (100), process tank A (101), filter A system (102), filter B system (103), process tank B (104), and FG tank (105).

[0035] Figure 2 shows the shelf life of diiodosilane purified according to the method of the present invention compared to a control sample at room temperature, i.e., about 23°C, 40°C, and 60°C, over a 16 week period. The graph illustrates the greatly improved stability of the diiodosilane composition so purified. This result was surprisingly achieved without prior or subsequent distillation of the desired diiodosilane. EXAMPLES

[0036] Example 1 The purification process described in FIG. 1 shows the configuration of process tanks A and B, and filters A and B, and system A. Filter systems A (102) and B (103) are composed of filter cartridges with hydrophilic functionalized membranes and filter housings with stainless steel cylinders. Nitrogen inlet gas is connected to both process tanks A and B, and the filtration process is carried out under dry nitrogen atmosphere. A predetermined amount of diiodosilane raw material in the RM tank (100) is transferred to process tank A (101). The inlet flow of diiodosilane raw material under nitrogen gas pressure enters the inlet port of filter A system (102), passes through the filter membrane cartridge in the filter housing, and is discharged from the outlet port of filter A system (102) into process tank B (104). This forward process continues to operate until all diiodosilane raw material in process tank A (101) is depleted, while monitoring the weight of process tank A (101). For the reverse process, the diiodosilane raw material in the process tank B (104) under nitrogen gas pressure enters the inlet port of the filter B system (103), passes through the filter membrane cartridge in the filter housing, and is discharged from the outlet port of the filter B system (103), passes through the filter membrane cartridge in the filter housing, and is discharged from the outlet port of the filter B system (103) into the process tank A (101). This reverse process continues to operate until all the diiodosilane raw material in the process tank B (104) is depleted, while monitoring the weight of the process tank B (104). Then, the filtration loop cycle is repeated about 5 to about 10 times. Finally, a selected amount of the purified diiodosilane material in the process tank B is transferred to the FG tank (105).

[0037] The functionalized membrane is based on a hydrophilic functionalized nonwoven fabric prepared by grafting. The resulting membrane has a high density of ion-exchange functional groups on its surface, which allows the ion-exchange moieties to function effectively. The diiodosilane raw material contains polyvalent metal impurities such as Al, Ca, Cr, Au, Fe, Ni, Na, Ti, and Zn, which have a tendency to form charged colloids. The ion-exchange functionalized membrane was found to efficiently capture metal ions and microcolloids.

[0038] In the methods of the present invention and in the following examples, liquid compositions containing diiodosilane and the indicated amounts of metal impurities were passed through an Entegris Protego® Plus DI filter at room temperature at a flow rate of about 0.2 to about 0.5 liters per minute or a residence time in the ion exchange filter membrane of about 4 to about 10 minutes. The liquid compositions so purified were analyzed to obtain the data set forth below.

[0039] Example 2 Analysis of trace metal content Table 1 below details the filtration results of diiodosilane using the membranes of the present invention in parts per billion (ppb). TIFF0007665046000001.tif111170

[0040] Example 3 Storage life test in EP stainless steel cylinder In this example, diiodosilane was subjected to filtration according to Example 1 and compared to diiodosilane that was not subjected to filtration (control). The data, as shown in Figure 2, indicates that the filtered diiodosilane of Example 1 was able to maintain a purity of 99.9% or greater, as determined by gas chromatography, upon storage in a stainless steel cylinder for (a) (i) at room temperature, and (ii) 40°C for 4 months, and (b) 60°C for 2 months. The detailed results are as follows: TIFF0007665046000002.tif104170

[0041] Table 3 shows the purity on a monthly basis of both the filtered and control samples as determined by gas chromatography upon storage in a stainless steel cylinder for 7 months at (a) (i) room temperature, and (ii) 40° C., and (b) 60° C. The data, as shown in Table 3, indicates that the filtered diiodosilane of Example 1 was able to maintain a purity of 99.9% or greater as determined by gas chromatography upon storage in a stainless steel cylinder for (a) 7 months at room temperature, and (b) 5 months at 40° C., and (c) 2 months at 60° C.

[0042] In terms of monthly disproportionation reaction rates, the filtered sample exhibited (a) 0.003%(-)RR at room temperature, (b) 0.013%(-)RR over 7 months at 40° C., and (c) 0.032%(-)RR over 6 months at 60° C., as shown in Table 3. The results indicate that the filtered sample exhibited (a) a disproportionation rate 70 times lower than that of the control sample at room temperature and (b) approximately 40 times lower than that of the control sample at 40° C. and 60° C. TIFF0007665046000003.tif86170

[0043] Aspects In a first aspect, the present invention provides a method for removing one or more metals and / or metal ions from a liquid composition, the liquid composition comprising an iodo-substituted silane selected from monoiodosilane, diiodosilane, triiodosilane, tetraiodosilane, monoiododisilane, diiododisilane, triiododisilane, tetraiododisilane, pentaiododisilane, and hexaiododisilane, the method comprising: The method includes contacting a filter material with a liquid composition comprising an iodo-substituted silane having one or more metals and / or metal ions as impurities, wherein the filter material comprises at least one hydrophilic functional group selected from acidic, basic and ionic groups; thereby reducing the amount of the one or more metals or metal ions in the liquid composition.

[0044] In a second aspect, the present invention provides a method of the first aspect, wherein the filter material comprises a membrane.

[0045] In a third aspect, the present invention provides a method of the first aspect, wherein the hydrophilic functional group is an ion exchange group.

[0046] In a fourth aspect, the present invention provides the method of the first aspect, wherein the iodo-substituted silane is a diiodosilane.

[0047] In a fifth aspect, the invention provides the method of any one of the first four aspects, wherein the liquid composition comprising diiodosilane comprises from about 100 ppb or less to about 500 ppb of a metal selected from Al, Ca, Cr, Au, Fe, Ni, Na, Ti, and Zn.

[0048] In a sixth aspect, the present invention provides a method of any one of the first to fifth aspects, wherein about 40 to about 90% of the metal and / or metal ion contaminants are removed.

[0049] In a seventh aspect, the present invention provides a liquid composition comprising an iodo-substituted silane containing no more than about 30 ppb total of a metal selected from Ca, Cr, Fe, and Ni.

[0050] In an eighth aspect, the present invention provides a liquid composition, wherein the iodo-substituted silane is a diiodosilane, said composition containing no more than about 100 ppb total of a metal selected from Ca, Cr, Fe, Ni, and Ti.

[0051] In a ninth aspect, the present invention provides the liquid composition of the seventh aspect, wherein the iodo-substituted silane is a diiodosilane, and said composition contains up to 50 ppb total of a metal selected from Ca, Cr, Fe, and Ni.

[0052] In a tenth aspect, the present invention provides the liquid composition of the seventh aspect, wherein the iodo-substituted silane is a diiodosilane, and the composition contains no more than about 30 ppb total of a metal selected from Ca, Cr, Fe, and Ni.

[0053] In an eleventh aspect, the present invention provides a composition comprising a diiodosilane having a (-) reaction rate of less than 0.020 percent as calculated by Equation 1 using gas chromatographic assay data measured below room temperature, wherein Equation 1 is Reaction Rate (Percentage) + [(A 初期 -A 時間 ) / A 初期 ] / hour×100, where A is the gas chromatography assay percentage.

[0054] In a twelfth aspect, the present invention provides a composition comprising a diiodosilane having a (-) reaction rate of less than 0.05 percent, calculated according to Equation 1 described in the eleventh aspect, measured between room temperature and 40°C.

[0055] In a thirteenth aspect, the present invention provides a composition comprising a diiodosilane having a (-) reaction rate of less than 0.100 percent, as calculated by Equation 1 described in the eleventh aspect using gas chromatography data measured between 40°C and 60°C.

[0056] Having thus described several exemplary embodiments of the present disclosure, it will be readily apparent to one skilled in the art that still other embodiments may be made and used within the scope of the claims appended hereto. Numerous advantages of the present disclosure encompassed by this specification have been set forth in the foregoing description. It will be understood, however, that the present disclosure is in many respects merely illustrative. Of course, the scope of the present disclosure is defined in the language in which the appended claims are expressed.

Claims

1. 1. A method for removing one or more metals and / or metal ions from a liquid composition, the liquid composition comprising an iodo-substituted silane selected from monoiodosilane, diiodosilane, triiodosilane, tetraiodosilane, monoiododisilane, diiododisilane, triiododisilane, tetraiododisilane, pentaiododisilane, and hexaiododisilane, the method comprising: contacting a filter material with a liquid composition comprising an iodo-substituted silane having one or more metals and / or metal ions as impurities to reduce the amount of the one or more metals or metal ions in the liquid composition; and Repeating the contact of the filter material with the liquid composition for a total of 5 to 10 cycles. Including, The method, wherein the filter material is formed from a polymeric material, a mixture of different polymeric materials, or polymeric and non-polymeric materials, and includes at least one hydrophilic functional group selected from acidic, basic and ionic groups.

2. The method of claim 1 , wherein the hydrophilic functional group is an ion exchange group.

3. The method of claim 1 , wherein the iodo-substituted silane is a diiodosilane.

4. The method of claim 3, wherein the liquid composition contains 100 ppb to 1000 ppb of a metal selected from Al, Ca, Cr, Au, Fe, Ni, Na, Ti, and Zn.

5. The method of claim 3, wherein the diiodosilane is diluted with an inert solvent selected from pentane, hexane, and heptane.

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