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  Low-impurity organosilicon product as precursor for cvdRelated Patent Categories: Organic Compounds -- Part Of The Class 532-570 Series, Azo Compounds Containing Formaldehyde Reaction Product As The Coupling Component, Heavy Metal Containing (e.g., Ga, In Or T1, Etc.), Carbon Attached Directly Or Indirectly To The Silicon By Nonionic Bonding (e.g., Silanes, Etc.), Processes, Plural Silicons In A ReactantThe Patent Description & Claims data below is from USPTO Patent Application 20070287849. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of priority under 35 U.S.C. .sctn. 119(e) to earlier filed U.S. patent application Ser. No. 60/813,087, filed on Jun. 13, 2006, the disclosure of which is incorporated herein by reference in its entirety. BACKGROUND OF THE INVENTION [0002] The present invention is related to the field of low dielectric constant materials prepared by chemical vapor deposition (CVD) methods which serve as insulating layers in electronic devices. In particular, the present invention is directed to compositions for use as precursors to the low dielectric constant materials that have predetermined concentration limitations of certain impurities to eliminate process problems related to precipitation of such impurities. [0003] The electronics industry utilizes dielectric materials as insulating layers between circuits and components of integrated circuits (IC) and associated electronic devices. Line dimensions must be reduced in order to increase the speed and memory storage capability of microelectronic devices (e.g., computer chips). As the line dimensions decrease, the insulating requirements for the interlayer dielectric (ILD) become more rigorous. Shrinking dimensions requires a lower dielectric constant to minimize the RC time constant, where R is the resistance of the conductive line and C is the capacitance of the insulating dielectric layer. C is inversely proportional to spacing and proportional to the dielectric constant (k) of the ILD. [0004] Conventional silica (SiO.sub.2) CVD dielectric films produced from SiH.sub.4 or TEOS (tetraethylorthosilicate) and oxygen have a dielectric constant (k) of greater than 4.0. There are several ways in which the industry has attempted to produce silica-based CVD films with lower dielectric constants, the most successful being the doping of the insulating film with carbon atoms, fluorine atoms, or organic groups containing carbon and fluorine. Doping the silica with carbon atoms or organic groups lowers the k of the resulting dielectric film for several reasons. Organic groups, such as methyl, are hydrophobic; thus, adding methyl or other organic groups to the composition can act to protect the resulting CVD deposited film from contamination with moisture. The incorporation of such organic groups also serves to "open up" the structure of the silica, possibly leading to lower density through space-filling with bulky CH.sub.x bonds. Organic groups are also useful because some functionalities can be incorporated into the organosilicate glass (OSG), then subsequently "burned out" or oxidized to produce a more porous material which will inherently have a lower dielectric constant. [0005] Carbon can be incorporated into an ILD by using an organosilane as the silicon source material in the PECVD reaction. An example of such would be the use of methylsilanes, (CH.sub.3).sub.xSiH.sub.(4-x), as disclosed in U.S. Pat. No. 6,054,379. Alkoxysilanes (also referred to herein as silyl ethers) have also been disclosed as effective precursors for the introduction of organic moieties into the ILD. Particularly useful alkoxysilanes are disclosed in U.S. Pat. No 6,583,048. Of such alkoxysilanes, diethoxymethylsilane (DEMS) has found significant commercial use. [0006] The manufacture of organosilanes or alkoxysilanes, however, typically requires the use of halosilane chemical staring materials such as, for example, chlorosilane or organochlorosilane. In such reactions, the alkoxy group replaces the halogen, forming the desired alkoxysilane. Dimethyldimethoxysilane (DMDMOS), for example, is commercially manufactured utilizing the chemical reaction of dimethyldichlorosilane with methanol as shown below: (i) (CH.sub.3).sub.2SiCl.sub.2+2CH.sub.3OH.fwdarw.(CH.sub.3).sub.2Si(OCH.sub.- 3).sub.2+2HCl [0007] In a similar manner, DEMS is typically prepared primarily by one of two synthetic routes: the "direct" synthesis, shown below by equation (ii), involving the reaction of dichloromethylsilane with ethanol; and the "orthoformate" synthesis, shown by equation (iii), which involves the reaction of dichloromethylsilane with triethylorthoformate: (ii) CH.sub.3SiCl.sub.2H+2CH.sub.3CH.sub.2OH.fwdarw.CH.sub.3Si(OCH.sub.3).sub.- 2H+2HCl (iii) CH.sub.3SiCl.sub.2H+2(CH.sub.3CH.sub.2O).sub.3CH.fwdarw.CH.sub.3Si(OCH.su- b.3).sub.2H+CH.sub.3CH.sub.2Cl+2CH.sub.3CH.sub.2OC(O)H [0008] In all of the above cases the synthesis of the desired alkoxysilane is accompanied by the production of stoichiometric quantities of chloride-containing byproducts such as hydrochloric acid (HCl), as in the case of the reactions (i) and (ii), or ethylchloride, (CH.sub.3CH.sub.2Cl) as in the case of the latter reaction. The crude product mixture also typically contains some amount of unconverted chloromethylsilane. This is particularly true for the synthesis of DEMS, in which it is not practical to treat the dichloromethylsilane starting material with a substantial molar excess of reactant in order to drive the reaction to quantitative conversion. The presence of Si--H in the dichloromethylsilane makes it particularly vulnerable to attack forming undesirable side-reaction products if exposed to a substantial excess of either ethanol (CH.sub.3CH.sub.2OH) or triethylorthoformate ((CH.sub.3CH.sub.2O).sub.3CH). Given these constraints, the crude DEMS product typically has a significant amount of acid chlorides (HCl) and/or complexed silicon chloride impurities. Distillation is effective for removing most of the chloride impurities, but has limited efficacy for reducing the chlorides to the low levels required for CVD precursor source chemicals (e.g., <10 ppm by weight). In order to achieve these low chloride levels the product can be treated with a basic scavenger which will remove the chloride through complexation or adsorption. The basic scavenger can be in the form of a pure liquid or solid, such as in the case of an organoamine, in the form of a resin material such as in a packed bed of solid adsorbent material, or in the form of a gas such as, for example, gaseous ammonia. [0009] Industry standards for ILD source materials have stringent requirements for low levels of residual chloride and nitrogen-containing components. Residual chloride presents integration issues due to its potential migration and high reactivity. Nitrogen also needs to be minimized because of its potential for diffusion, possibly causing resist poisoning issues. Consequently, unacceptably high levels of halogen or nitrogen in CVD feed materials may cause undesirable performance problems for the resulting ILD films. [0010] As described above, two common routes for the preparation of DEMS are exemplified, each of which may yield unacceptably high levels of chloride contamination in the crude product due to unreacted starting material, acid chloride or complexed chloride byproducts. Distillation is commonly employed to purify the crude product, but it is not an effective means for reducing the chloride to acceptable levels. Typically, the distilled DEMS product is treated with an appropriate amount of a halide scavenger material in order to complex the chloride as the corresponding insoluble salt. This halide scavenger is often basic in nature, examples of which include amines, imides, alkali metal alcoholates, metal alkoxides, or solid adsorbent or resin materials such as activated carbons, alkali-treated activated carbons or other base-treated adsorbent substrates. The scavenger-chloride salt, thus formed, can be separated by conventional means such as filtration or further distillation in order to produce a DEMS product with less than 10 ppm chloride by weight. [0011] There are significant drawbacks, however, associated with the use of residual chloride scavengers. For example, during CVD processing it is not uncommon that different lots of organosilicon precursor such as, for example, DEMS, may be combined, such as when a partially empty container is back-filled with a second source container of precursor, or when two different precursor source containers are feeding a common manifold. Precipitation of solids may occur if a sample of precursor containing a substantial amount of dissolved residual chloride is combined with a second source of precursor containing a substantial amount of dissolved residual basic scavenger. Solids formation in this manner leads to production problems because the solid precipitate typically restricts or blocks the flow of the liquid precursor, contaminates the liquid delivery or deposition hardware, and numerous potential performance and or quality issues associated with the deposited low-k films. Accordingly, there is a need in the art for an organosilicon precursor composition that is substantially free of having the potential to precipitate chloride salts upon mixture with other organosilicon precursor material. BRIEF SUMMARY OF THE INVENTION [0012] The present invention satisfies the need for an organosilicon precursor composition that is substantially free of having the potential to precipitate chloride salts upon mixture with other organosilicon precursor material. The present invention satisfies this need by defining an upper limit for the concentration of chloride and chloride scavenger in an organosilicon such as, for example, DEMS, that must be met in order to ensure that chloride will not precipitate when such organosilicon product is mixed either with another lot of the product from the same source or with another product from a different source. [0013] In one aspect, the present invention provides an organosilicon composition comprising: at least one organosilicon selected from the group consisting of: an alkoxysilane and a carboxysilane; a first concentration of dissolved residual chloride; and a first concentration of dissolved residual chloride scavenger, wherein the organosilicon composition has a first K.sub.sp(os) defined as the product of [the first concentration of the dissolved residual chloride in parts per million by weight].sup.X, wherein X is 1, 2, 3, or 4 and [the first concentration of the dissolved residual chloride scavenger in parts per million by weight], wherein the first concentration of dissolved residual chloride is less than the square root of the first K.sub.sp(os) when X is 1, less than cubed root of the first K.sub.sp(os) when X is 2, less than the fourth root of the first K.sub.sp(os) when X is 3, or less than the fifth root of the first K.sub.sp(os) when X is 4, and the first concentration of the dissolved residual chloride scavenger is less than the square root of the first K.sub.sp(os) when X is 1, less than cubed root of the first K.sub.sp(os) when X is 2, less than the fourth root of the first K.sub.sp(os) when X is 3, or less than the fifth root of the first K.sub.sp(os) when X is 4. [0014] In another aspect, the present invention provides a method method for preventing solids formation in an organosilicon material employed in a chemical vapor deposition process, the method comprising the steps of: providing an organosilicon composition comprising: at least one organosilicon selected from the group consisting of: an alkoxysilane and a carboxysilane; a first concentration of dissolved residual chloride; and a first concentration of dissolved residual chloride scavenger, wherein the organosilicon composition has a first K.sub.sp(os) defined as the product of [the first concentration of the dissolved residual chloride in parts per million by weight].sup.X, wherein X is 1, 2, 3, or 4 and [the first concentration of the dissolved residual chloride scavenger in parts per million by weight], wherein the first concentration of dissolved residual chloride is less than the square root of the first K.sub.sp(os) when X is 1, less than cubed root of the first K.sub.sp(os) when X is 2, less than the fourth root of the first K.sub.sp(os) when X is 3, or less than the fifth root of the first K.sub.sp(os) when X is 4, and the first concentration of the dissolved residual chloride scavenger is less than the square root of the first K.sub.sp(os) when X is 1, less than cubed root of the first K.sub.sp(os) when X is 2, less than the fourth root of the first K.sub.sp(os) when X is 3, or less than the fifth root of the first K.sub.sp(os) when X is 4; providing a second organosilicon comprising at least one organosilicon selected from the group consisting of: an alkoxysilane and carboxysilane, a second concentration of dissolved residual chloride, and a second concentration of dissolved residual chloride scavenger, wherein the second organosilicon has a second K.sub.sp(os) defined as the product of [the second concentration of the dissolved residual chloride in parts per million by weight].sup.X, wherein X is 1, 2, 3, or 4, and [the second concentration of the dissolved residual chloride scavenger in parts per million by weight] and wherein each of the second concentration of dissolved residual chloride and the second concentration of the dissolved residual chloride scavenger is less than the square root of the first K.sub.sp(os) when X is 1, less than cubed root of the first K.sub.sp(os) when X is 2, less than the fourth root of the first K.sub.sp(os) when X is 3, or less than the fifth root of the first K.sub.sp(os) when X is 4. [0015] In yet another aspect, the present invention provides a method for purifying an organosilicon composition comprising at least one of an an alkoxysilane and a carboxysilane; and dissolved residual chloride, the method comprising the steps of: contacting the organosilicon composition with a stoichiometric excess of a basic chloride scavenger to cause at least a portion of the dissolved residual chloride to precipitate as a chloride salt; removing the precipitated chloride salt from the organosilicon composition; contacting the organosilicon composition with an acid gas to form a precipitate comprising a salt of the acid gas upon reaction with the excess basic chloride scavenger; and removing the salt of the acid gas to form a purified organosilicon product. [0016] In preferred embodiments of the present invention, the organosilicon composition comprises diethoxymethylsilane (DEMS). BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS [0017] FIG. 1 is a flow diagram illustrating the present invention; [0018] FIG. 2 is a phase diagram of a composition according to the present invention; [0019] FIG. 3 is the phase diagram of FIG. 2 further illustrating preferred embodiments of the present invention; and [0020] FIG. 4 is a comparative chromatogram that illustrates a feature of the present invention. Continue reading... Full patent description for Low-impurity organosilicon product as precursor for cvd Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Low-impurity organosilicon product as precursor for cvd patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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