Patent Description:
Alkenyl or alkynyl-containing organosilicon precursor compounds such as, for example, tetravinylsilane (TVS) have been identified as leading candidates for the deposition of silicon carbide (SiC), silicon oxycarbide (SiOC), and silicon carbonitride (SiCN) films. During a conventional deposition process, a direct liquid injection (DLI) technique is employed to repeatedly deliver precisely controlled quantities of precursor compounds to the process tool deposition chamber. The deposition process can include chemical vapor deposition (CVD), atomic layer deposition (ALD), plasma enhanced chemical vapor deposition (PECVD), flowable chemical vapor deposition (FCVD), plasma enhanced atomic layer deposition (PEALD) or other methods to deposit these films.

During deposition it is necessary to deliver a constant flow of alkenyl or alkynyl-containing organosilicon precursor compound and alkenyl or alkynyl-containing organosilicon precursor compound-like precursors to the process tool using the combination of a liquid mass flow controller (LMFC) and a heated vaporizing injector system that will volatize the precursor, which will be swept away from the injector through a heated delivery line to the process chamber. During this process it is critical that non-volatile residues or components do not accumulate in the LMFC, injector, or chemical delivery line. The unsaturated moiety of the organosilicon precursor compound is prone to polymerization and the organosilicon precursor compound will gradually degrade or polymerize and precipitate out at ambient temperature or at moderate temperatures that are often encountered during normal processing, purification or application of the particular chemical. Such build-up of residues/precipitate leads to a disruption in flow of vapor into the process chamber, which would severely impact the repeatability of film growth making the process unworthy of high volume manufacturing (HVM).

Such examples of residues could include the residue left behind in the injector as a result of impurities in the alkenyl or alkynyl-containing organosilicon precursor compound, like chlorine-containing impurities that have less volatility relative to the alkenyl or alkynyl-containing organosilicon precursor compound, and higher molecular weight impurities resulting from self-initiated polymerization of the alkenyl or alkynyl-containing organosilicon precursor compound due to light absorption or the presence of other free radical generating impurities. In such instances it is believed that the higher molecular weight impurities would remain soluble in the alkenyl or alkynyl-containing organosilicon precursor compound until they passed thru the injector and would then begin to either thicken or condense and fall out into the gas delivery line where they would accumulate, eventually obstructing the flow of gas into the process chamber.

To prevent such disruptive phenomena from occurring it is necessary to have the proper composition of the alkenyl or alkynyl-containing organosilicon precursor compound, which includes a concentration of impurities that falls within a given range for both low and higher molecular weight impurities. Accordingly, there is a need for an alkenyl or alkynyl-containing organosilicon precursor compound that is produced as pure as possible and which remains pure over time, once it is packaged.

<CIT> and <CIT> relate to separation of unsaturated silane compounds from the reaction solvent tetrahydrofuran, by distillation with an additional solvent. Purity levels of tetravinylsilane of <NUM>-<NUM> % are disclosed.

<CIT> discloses methods for producing vinylsilanes comprising a distillation step.

<CIT> discloses a method for producing trimethoxysilane comprising a distillation step and storing the purified compound in a metallic vessel.

<NPL>, discloses formation and distillation of tetravinylsilane.

The present invention provides a method for producing a tetravinylsilane-containing organosilicon precursor composition, the method comprising the steps of:.

In another aspect, the present invention provides a system for storing tetravinylsilane, the system comprising:.

The various embodiments of the invention can be used alone or in combinations with each other.

In one or more embodiments, in their intended use, the precursors are exposed to reactive radicals to initiate a radical induced polymerization in the deposition chamber.

In one embodiment, the method of the present invention further comprises adding a stabilizer compound to the distilled tetravinylsilane-containing organosilicon precursor composition prior to said packing step.

To the extent that a composition comprising a crude (i.e., prior to purification by distillation according to the present invention) tetravinylsilane-containing organosilicon compound such as, for example, one having a residual chloride or other halide impurity, the majority of the chloride-containing components can be removed from the crude tetravinylsilane-containing organosilicon compound through distillation.

The organosilicon compounds according to the present invention are substantially free of halide. As used herein, the term "substantially free" as it relates to halide ions (or halides) such as, for example, chlorides (i.e. chloride-containing species such as HCl or organosilicon compounds having at least one Si-Cl bond) and fluorides, bromides, and iodides, means less than <NUM> ppm (by weight) measured by ion chromatography (IC), and preferably <NUM> ppm measured by IC. Significant levels of chloride in the final product can cause leaching metals from the stainless steel container during storage or use into the organosilicon precursor in presence of moisture or water and the leached metal ions may catalyze polymerization of the organosilicon precursor to form high molecular weight impurities. The gradual degradation of the organosilicon compounds may directly impact the film deposition process making it difficult for the semiconductor manufacturer to meet film specifications. In addition, the shelf-life or stability is negatively impacted by the higher degradation rate of the organosilicon compounds, thereby making it difficult to guarantee a <NUM>-<NUM> year shelf-life. The organosilicon compounds are preferably substantially free of metal ions such as Li+, Na+, K+, Mg<NUM>+, Ca<NUM>+, Al<NUM>+, Fe<NUM>+, Fe<NUM>+, Ni<NUM>+, Cr<NUM>+. As used herein, the term "substantially free" as it relates to Li, Na, K, Mg, Ca, Al, Fe, Ni, Cr means less than <NUM> ppm (by weight), preferably less than <NUM> ppm, and more preferably less than <NUM> ppm, and most preferably <NUM> ppm as measured by ICP-MS. The organosilicon compounds are also substantially free of water and preferably substantially free oforganosilane impurities such as other alkenyl or alkynyl-containing organosilicon compounds either from starting materials or by-products from the synthesis, as used herein, the term "substantially free" as it relates to water is less than <NUM> ppm (by weight) as analyzed by Karl Fisher, and preferably less than <NUM> ppm; the sum of all organosilane impurities such as trivinylchlorosilane as analyzed by gas chromatography (GC) is less than <NUM> wt. %, preferably less than <NUM> wt. %, and preferably less than <NUM> wt.

In some embodiments, added to the distilled tetravinylsilane-containing organosilicon precursor composition is a stabilizer compound. Exemplary stabilizer compounds include <NUM>,<NUM>-di-tert-butyl-<NUM>-methyl phenol (or BHT for butylhydroxytoluene), <NUM>,<NUM>,<NUM>,<NUM>-tetramethyl-<NUM>-piperidinyloxy (TEMPO), <NUM>- tert-butyl-<NUM>-hydroxyanisole, <NUM>-tert-butyl-<NUM>-hydroxyanisole, propyl ester <NUM>,<NUM>,<NUM>-trihydroxy-benzoic acid, <NUM>-(<NUM>,<NUM>-dimethylethyl)-<NUM>,<NUM>-benzenediol, diphenylpicrylhydrazyl, <NUM>-tert-butylcatechol, N-methylaniline, p- methoxydiphenylamine, diphenylamine, N,N'-diphenyl-p-phenylenediamine, p- hydroxydiphenylamine, phenol, octadecyl-<NUM>-(<NUM>,<NUM>-di-tert-butyl-<NUM>- hydroxyphenyl) propionate, tetrakis (methylene (<NUM>,<NUM>-di-tert-butyl)-<NUM>- hydroxy-hydrocinnamate) methane, phenothiazines, alkylamidonoisoureas, thiodiethylene bis (<NUM>,<NUM>,-di-tert-butyl-<NUM>-hydroxy-hydrocinnamate, <NUM>,<NUM>,-bis (<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxyhydrocinnamoyl) hydrazine, tris (<NUM>-methyl-<NUM>- hydroxy-<NUM>-tert-butylphenyl) butane, cyclic neopentanetetrayl bis (octadecyl phosphite), <NUM>,<NUM>'-thiobis (<NUM>-tert-butyl-m-cresol), <NUM>,<NUM>'-methylenebis (<NUM>-tert-butyl-p-cresol), oxalyl bis (benzylidenehydrazide) and naturally occurring antioxidants such as raw seed oils, wheat germ oil, tocopherols and gums. The function of the stabilizer compound is to prevent self-polymerization or oligomerization of the tetravinylsilane-containing organosilicon precursor.

The method of the present development comprises the step of packaging the distilled tetravinylsilane-containing organosilicon precursor composition in a container, wherein the container permits transmission into the container of no more than <NUM>% of ultraviolet and visible light having a wavelength of between <NUM> to <NUM>. As used herein, the packaged distilled tetravinylsilane-containing organosilicon precursor composition in the container as described herein is referred to as a "system.

In some embodiments, the container permits transmission of no more than <NUM>% of ultraviolet and visible light having a wavelength of between <NUM> to <NUM>. In other embodiments, the container permits transmission of no more than <NUM>% of ultraviolet and visible light having a wavelength of between <NUM> to <NUM>. In other embodiments, the container permits transmission of no more than <NUM>% of ultraviolet and visible light having a wavelength of between <NUM> to <NUM>. In other embodiments, the container permits transmission of no more than <NUM>% of ultraviolet and visible light having a wavelength of between <NUM> to <NUM>. In yet another embodiments, the container permits transmission of no more than <NUM>% of ultraviolet and visible light having a wavelength of between <NUM> to <NUM>. In still other embodiments, the container permits <NUM>% transmission into the container of ultraviolet and visible light having a wavelength of between <NUM> to <NUM>.

The percent of UV and visible light transmission through a solid medium can be measured by any method known to those skilled in the art such as, for example, UV-VIS absorption spectroscopy, where a sample is illuminated from one side, and the intensity of the light that exits from the sample in every direction is measured. Any UV-VIS absorption instrument commercially available may be employed to measure transmission of ultraviolet and visible light having a wavelength of between <NUM> to <NUM> according to the present invention.

The stainless steel material from which the container is made and the thickness of the container's wall structure operably inhibits transmission of light through the container wall structure having a wavelength between about <NUM> to <NUM>.

An example of a container that can be employed in the present invention is the high-purity chemical container disclosed in <CIT>.

Preferably, the container once filled with the distilled tetravinylsilane-containing organosilicon precursor composition of the present invention is stored at a temperature of from <NUM> to <NUM>, and more preferably at room temperature.

The following working examples show the importance of obtaining tetravinylsilane-containing blends with low levels of impurities such as higher molecular weight species, moistures and halogens such as chloride.

Example <NUM> (comparative): Samples from two different sources of tetravinylsilanes (TVS) were analyzed by Gel Permeation Chromatography (GPC) to determine the concentration of higher molecular weight (HMW) species present in the liquid. Table <NUM> below shows the comparative samples showing TVS containing > <NUM> wt. % of HMW species (> <NUM> atomic mass unit (amu), for example species or oligomers having molecular weight ranging from <NUM> to <NUM> amu) and TVS containing <NUM> wt. % (<NUM> ppm) higher molecular weight species (> <NUM> amu). The two sources of TVS would have significantly differing impacts on the continuous delivery of TVS through the DLI system and into the CVD process chamber.

A flow test was done on Versum Materials DLI (direct liquid injection) test system with Horiba STEC LF-410A liquid flow meter and MV1000 vapor injector. <NUM> of Tetravinylsilane (TVS) chemical was transferred under inert atmosphere to a Versum materials Chemguard™ liquid containment system. The TVS chemical assay was <NUM> wt. %, HMW impurity was <NUM> wt. %, chloride content was <NUM> ppm and H<NUM>O content was <NUM> ppm. The injector temperature was set to <NUM>. The injector downstream line was heated to <NUM>. Helium gas set at a pressure of <NUM> psig (<NUM> kPa absolute) was used to push the liquid to the vapor injector. An additional <NUM> sccm of helium was used as an inert carrier gas across the injector interface. The liquid flow was set at <NUM>/min. The liquid flow was periodically turned ON for <NUM> minutes and turned OFF for <NUM> mins controlled by PLC. The liquid flow and pressure in the line initially were very stable. After <NUM> hours of chemical flow cycling, the liquid flow rate and line pressure started to fluctuate, indicating a disruption in stable flow of chemical to the process chamber. After the test, the TVS container was unloaded from the Chemguard™ tool and a container with <NUM> of hexane was installed onto Chemguard™. A hexane solvent flush was performed with the same tool set up. The hexane flow was not stable, confirming the injector was partially clogged. After the flow test was complete, the injector and tubing located post injector was inspected for residue. Some amount of brownish polymer material was found in the injector and tubing post injector. The hexane flush results also indicated that the oligomers/polymers formed from TVS with a high HMW impurity level could not be solubilized using hexane. Not to be bound by theory, these results suggest that the oligomers/polymers are accumulated in a region of the DLI system where the solvent has been vaporized and thus not capable of solvating the oligomers, causing unstable flow of chemical into the process chamber.

For comparison, a flow test was done on Versum Materials DLI (direct liquid injection) test system with Horiba STEC LF-410A liquid flow meter and MV1000 vapor injector with distilled high purity TVS chemical. <NUM> of distilled TVS chemical was transferred under inert atmosphere to a Versum materials Chemguard™ liquid containment system. The TVS chemical assay was <NUM>%, chloride content was <NUM> ppm and H<NUM>O content was <NUM> ppm. The injector temperature was set to <NUM>. The injector downstream line was heated to <NUM>. Helium gas at a pressure of <NUM> psig (<NUM> kPa absolute) was used to push the liquid to the vapor injector. An additional <NUM> sccm of helium was used as an inert carrier gas across the injector interface. The liquid flow was set at <NUM>/min. The liquid flow was periodically turned ON for <NUM> minutes and turned OFF for <NUM> mins controlled by PLC. The liquid flow rate and line pressure and injector control voltage were stable throughout the test until the chemical supply ran out after <NUM> hours of flow test. After the test, the TVS container was unloaded from the Chemguard™ tool and a container with hexane was installed into the Chemguard™. A hexane flush was performed with the same tool set up. The hexane flow was stable, indicating that no oligomers/polymers were impeding the delivery of chemical through the DLI and to the tool.

An accelerated aging test was performed by heating TVS samples at <NUM> to determine how impurity concentration can increase over time. Observed in Table <NUM> was an increase in higher molecular weight (HMW) impurities ( > <NUM> amu such as ) determined by GPC after heating of the samples and exposure for <NUM> - <NUM> days. Without intending to be bound by a particular theory, it is believed that this increase is observed resulting from self-polymerization of the TVS. The consequences of this polymerization would be the observed reduction of chemical flow into the deposition chamber as discussed above. Oligomers or high molecular weight impurities was determined by GPC. Results indicate that lower initial HMW impurity concentrations will result in more gradual increases over the lifetime of material, which should greatly reduce the risk of chemical delivery interruptions.

Experiments were done to assess the effect of water and chloride in TVS (tetravinylsilane) on the corrosion of stainless steel. TVS with different levels of water and chloride were heated in electropolished <NUM> stainless steel tubes to simulate prolonged storage conditions at room temperature.

Four samples of TVS with different amounts of water and chloride were heated in separate stainless steel tubes for <NUM> days at <NUM>. One week at <NUM> is intended to simulate the ageing that would normally occur over one year at ambient temperature. For the purpose of this experiment accelerated aging is assumed to follow the Arrhenius principle using the modified <NUM>-degree rule methodology. For any age, at an accelerated aging temperature, the equivalent room temperature age can be estimated by the equation below where trt is the room temperature equivalent age, tAA is the age at the accelerated aging temperature, TAA is the accelerated aging temperature in °C, Trt is room temperature (<NUM>), and Q<NUM> is the reaction rate coefficient that is set to <NUM> for the current test. A further description of accelerated aging method can be found in ASTM method F1980-<NUM>.

Test Sample #<NUM> had low chloride and low water; Sample #<NUM> (comparative) had low chloride and high water; Sample #<NUM> (comparative) had high chloride and low water; and Sample #<NUM> (comparative) had high chloride and high water. These <NUM> samples of TVS were analyzed for their stainless steel metals content (Fe, Cr, Ni, Mn and Mo) by ICP-MS (inductively coupled plasma - mass spectrometry) before and after heat treatment. These were also analyzed by GC (gas chromatography) before and after heating to assess the impact of ageing on the TVS purity. A summary of these four samples and the analytical results are in Table <NUM> below.

No increase in any of the stainless steel metals was observed after ageing TVS Sample #<NUM> (low chloride, low water). This was not the case for TVS Samples #<NUM>-<NUM>. Increases in Ni, Cr and Mn were observed for the TVS Samples #<NUM>-<NUM>, all of which had high chloride, high water or high chloride and high water. An increase in the stainless steel metals content after heating is an indication of the corrosion that would occur after storage of the TVS in a stainless steel vessel after one year at room temperature. The overall purity as measured by GC did not change significantly after the heat treatment. No color change was evident before/after ageing of any of the TVS samples, irrespective of the chloride or water content.

These experiments demonstrate the importance of low chloride and low water in TVS to avoid corrosion of the stainless steel containers which would lead to leaching of the stainless steel metals, such as Fe, Cr, Ni, Mn and Mo, into the TVS liquid.

Claim 1:
A method for producing a tetravinylsilane-containing organosilicon precursor composition, the method comprising the steps of:
distilling at least once a composition comprising tetravinylsilane, wherein a distilled tetravinylsilane composition is produced after distilling, wherein the distilled tetravinylsilane composition includes less than <NUM> ppm (<NUM> wt. %) of ><NUM> amu impurities as determined by Gel Permeation Chromatography (GPC) and wherein the distilled tetravinylsilane composition includes less than <NUM> ppm water impurity and less than <NUM> ppm halide impurity; and
packaging the distilled tetravinylsilane composition in a container, wherein the container is made of stainless steel, and wherein the container permits transmission into the container of no more than <NUM>% of ultraviolet and visible light having a wavelength of between <NUM> to <NUM>.