US 2004.0122248A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2004/0122248A1 Shenai-Khatkhate et al. (43) Pub. Date: Jun. 24, 2004

(54) PREPARATION OF ORGANOMETAL Related U.S. Application Data COMPOUNDS (60) Provisional application No. 60/419,622, filed on Oct. (75) Inventors: Deodatta Vinayak Shenai-Khatkhate, 18, 2002. Provisional application No. 60/422,043, Danvers, MA (US); Ronald L. Dicarlo filed on Oct. 29, 2002. JR., Newfields, NH (US); Michael L. Timmons, Durham, NC (US) Publication Classification Correspondence Address: (51) Int. Cl...... C07F 5/02 EDWARDS & ANGELL, LLP (52) U.S. Cl...... 556/7 P.O. Box 91.69 (57) ABSTRACT Boston, MA 02209 (US) A method of preparing organometal compounds that does (73) Assignee: Shipley Company, L.L.C., Marlbor not use oxygenated Solvents is provided. The compounds ough, MA (US) produced by Such method are particularly useful as precur Sor compounds for metalorganic chemical vapor deposition (21) Appl. No.: 10/675,394 processes used in the manufacture of electronic devices. Methods of depositing metal films using Such organometal (22) Filed: Sep. 30, 2003 compounds are also provided. US 2004/O122248 A1 Jun. 24, 2004

PREPARATION OF ORGANOMETAL gallium compound. Certain procedures have been developed COMPOUNDS in an effort to remove Such Zinc impurities, Such as by contacting the trialkyl gallium compound with a metallic BACKGROUND OF THE INVENTION gallium-containing melt. Such contact may be achieved by refluxing the trialkyl gallium in the presence of the melt. 0001. The present invention relates generally to the field This purification procedure adds greatly to the manufactur of organometallic compounds. In particular, this invention ing costs of the trialkyl gallium compounds, Such as reduced relates to the preparation of alkyl metal compounds which output and increased waste handling costs, and does not are Suitable for use as precursors for chemical vapor depo guarantee complete removal of the impurities. Sition. 0006 For certain applications, such small amount of 0002 Metal layers may be deposited on Surfaces, such as aluminum present in a trialkyl gallium compound is not non-conductive Surfaces, by a variety of means Such as problematic. However, where ultrapure gallium-containing chemical vapor deposition (“CVD”), physical vapor depo layers are required, e.g. in blue LEDs, aluminum contami sition (“PVD”), and other epitaxial techniques such as liquid nation can be a problem. For example, when Such trialkyl phase epitaxy (“LPE'), molecular beam epitaxy ("MBE”), gallium compounds are used to deposit a gallium nitride and chemical beam epitaxy (“CBE). Chemical vapor depo layer, the Small amount of aluminum present will precipitate Sition processes, Such as metalorganic chemical vapor depo onto the growing film in the form of aluminum nitride. sition (“MOCVD), deposit a metal layer by decomposing Conventionally, trialkyl gallium compounds produced by a organometallic precursor compounds at elevated tempera transalkylation reaction with a trialkyl aluminum compound tures, i.e. above room temperature, either at atmospheric are Subjected to numerous purification Steps, Such as mul preSSure or at reduced pressures. In conventional CVD tiple distillations, in order to attempt to remove as much of processes, Suitable precursor compounds must have a Suf the aluminum impurity as possible. Such numerous purifi ficient vapor pressure to allow them to be transported to the cation Steps greatly increase the manufacturing cost and do deposition chamber. Both Solid and liquid precursor com not completely remove the aluminum impurity. Also, the pounds are known. trialkyl aluminum Starting materials are pyrophoric which 0003) A wide variety of metals may be deposited using makes handling them difficult and also increases the manu such CVD or MOCVD processes. See, for example, String facturing costs. Such trialkyl aluminum Starting materials fellow, Organometallic Vapor Phase Epitaxy. Theory and also typically contain Silicon impurities which are difficult to Practice, Academic Press, 2" Edition, 1999, for an over remove and causes problems in compound semiconductor View of Such processes. For example, gallium is used in a applications. variety of metal films produced by epitaxial growth, par ticularly in the manufacture of electronic devices Such as 0007 Hupe et al., Mechanism of the Stereoselective Alkyl integrated circuits and light emitting diodes (“LEDs). Group Exchange between Alkylboranes and Alkylzinc Com Exemplary gallium containing metal films include gallium pounds, Organometallics, vol. 21pp. 2203-2207 (2002), arsenide (“GaAs), indium-gallium-arsenide (“InCaAs), disclose the theoretical reaction of certain trialkylboranes aluminum-gallium-arsenide ("AlGaAs), indium-gallium with certain alkyl metal compounds, Such as diisopropylz aluminum-phosphide ("InGaAlP), indium-gallium-arsenic inc. Reactions of trialkylboranes with metal compounds phosphide ("InGaASP”), and indium-gallium-arsenide/gal other than alkyl metal compounds are not disclosed. lium-arsenide/aluminum-gallium-arsenide (“InGaAS/GaAS/ 0008. There is a need for a alkyl metal compounds, that AlGaAs”). Gallium arsenide phosphide (“GaAsP”) is are leSS costly to manufacture and can be prepared without suitable for visible LEDs and fiber optic emitters/detectors. the use of highly pyrophoric Starting materials. There is an additional need for trialkyl gallium and trialkyl indium 0004 For semiconductor and electronic device applica compounds having reduced or eliminated aluminum, Zinc tions, these organometallic precursor compounds must be and Silicon impurities. highly pure and be substantially free of detectable levels of both metallic impurities, Such as Silicon and Zinc, as well as SUMMARY OF THE INVENTION oxygenated impurities. Oxygenated impurities are typically 0009. It has been found that certain organometal com present from the Solvents used to prepare Such organome pounds, Such as trialkyl gallium, can be prepared in high tallic compounds, and are also present from other adventi yield and in high purity Starting from triorgano boron tious Sources of moisture or oxygen. compounds. Such reactions are performed in ether-free 0005 Trialkyl gallium compounds are typically used as Solvents. The organometal compounds produced by this precursor compounds for the deposition of gallium. Such method are extremely pure and Substantially free of oxy trialkyl gallium compounds are conventionally prepared by genated impurities. a transalkylation method Such as by reacting a gallium 0010. The present invention provides a method of pre trihalide with a trialkyl aluminum. The trialkyl gallium paring organometal compounds including the Step of react compounds generally contain Small amounts of impurities ing a triorgano boron compound with a metal halide com Such as aluminum, Zinc and Silicon, which are difficult to pound, wherein the metal halide compound includes a metal remove despite extensive purification procedures. Zinc is a Selected from gallium, indium, aluminum, cadmium and p-type impurity and even a few parts per million may be Zinc. Also contemplated by the present invention is an detrimental in certain Semiconductor applications. Dialky organometal compound free of oxygenated impurities, 1zinc compounds, which are often present in trialkyl gallium wherein the organometal compound includes a metal compounds, can be very difficult to remove using conven Selected from gallium, indium, aluminum, cadmium and tional methods, Such as distillation, due to the close proX Zinc. Preferred metal halide compounds are the metal diha imity of their boiling points to the corresponding trialkyl lides and trihalides. US 2004/O122248 A1 Jun. 24, 2004

0.011) Also provided by the present invention is a method lide compounds, triaryl aluminum compounds, dialkyl Zinc of depositing a metal layer including the steps of: a) con compounds, alkyl Zinc halide compounds, dialkyl cadmium veying an organometal compound in the gaseous phase to a compounds, alkyl cadmium halide compounds and the like. deposition chamber containing the Substrate; b) decompos Preferably, Such reaction is performed in an organic Solvent ing the organometal compound in the deposition chamber; free from oxygen Substitution. Such organometal com and c) depositing a metal layer on the Substrate; wherein the pounds are Substantially free of oxygenated impurities and organometal compound is free of oxygenated impurities, preferably free of such impurities. By “substantially free of and wherein the metal is Selected from gallium, indium, oxygenated impurities” it is meant that the organic Solvent aluminum, cadmium and zinc. contains S50 ppm of oxygenated impurities. 0012. The present invention further provides a method for manufacturing an electronic device including the Step of 0017 Suitable metal halide compounds are any that can depositing a metal layer on an electronic device Substrate be reacted with the triorgano boron compounds according to comprising the Steps of: a) conveying an organometal com the present invention and include, without limitation, gal pound in the gaseous phase to a deposition chamber con lium halide compounds, indium halide compounds, cad taining the Substrate; b) decomposing the organometal com mium halide compounds, and Zinc halide compounds. AS pound in the deposition chamber; and c) depositing a metal used herein, a metal halide compound is any metal com layer on the Substrate; wherein the organometal compound pound containing one or more halogens. In particular, Suit is free of oxygenated impurities, and wherein the metal is able metal halide compounds have the formula MY wherein Selected from gallium, indium, aluminum, cadmium and each Y is independently halogen, alkyl or aryl, a is the ZC. Valence of the metal, and M is gallium, indium, aluminum, 0013 In addition, the present invention provides a cadmium or Zinc, wherein at least one Y is halogen. Chlorine method for preparing an organometal compound including and bromine are particularly useful halogens. M is typically the Steps of reacting a triorgano boron compound with a gallium, indium, cadmium or Zinc and more typically gal metal halide compound, wherein the metal halide includes a lium, indium or zinc. Suitable alkyl groups for Y are metal Selected from gallium, indium, aluminum, cadmium (C-C)alkyl, preferably (C-C)alkyl, and more preferably and Zinc, to form a boron halide compound and the orga (C-C)alkyl. When two or more Ys are alkyl, each such nometal compound; isolating the boron halide compound; alkyl may be the same or different. Suitable aryl groups and reacting the boron halide compound with an organo include, without limitation, phenyl, benzyl, biphenyl, and aluminum compound or an alcohol. naphthyl. The aryl groups for Y may optionally be substi tuted, Such as by replacing one or more hydrogens with a DETAILED DESCRIPTION OF THE (C-C)alkyl. It will be appreciated by those skilled in the art INVENTION that more than one metal compound may be used in the 0.014 AS used throughout this specification, the follow present invention. ing abbreviations shall have the following meanings, unless 0018 Exemplary metal compounds include, but are not the context clearly indicates otherwise: C.=degrees centi limited to, gallium trichloride, gallium tribromide, gallium grade, NMR=nuclear magnetic resonance; mol=moles, triiodide, chlorodimethy gallium indium trichloride, indium g=gram; L=liter; ca.=approximately, micron=micrometer; tribromide, indium triiodide, cadmium dichloride, cadmium and mL=milliliter. diiodide, cadmium dibromide, Zinc dichloride, Zinc dibro 0.015 “Halogen” refers to fluorine, chlorine, bromine and mide, and mixtures thereof. Metal compounds containing iodine and "halo' refers to fluoro, chloro, bromo and iodo. mixed halogens may also be used. Such metal compounds Likewise, "halogenated” refers to fluorinated, chlorinated, are generally commercially available from a variety of brominated and iodinated. “Alkyl” includes linear, branched Sources or may be prepared by a variety of methods known and cyclic alkyl. Likewise, the term “alkenyl' includes in the literature. linear, cyclic and branched alkenyl. AS used herein, “alk 0019. A wide variety of organo boron compounds may be enyl' includes dienes. Unless otherwise noted, all amounts used. Exemplary triorgano boron compounds have the for are percent by weight and all ratios are molar ratios. All mula ZB, wherein each Z is independently Selected from numerical ranges are inclusive and combinable in any order halogen, (C-C)alkyl, (C-C)alkenyl or aryl, provided that except where it is clear that Such numerical ranges are at least one Z is alkyl, alkenyl or aryl. Suitable alkyl groups constrained to add up to 100%. include, but are not limited to, methyl, ethyl, propyl Such as 0016. The present invention provides a method for pre n-propyl and isopropyl, and butyl Such as n-butyl, iso-butyl paring organometal compounds including the Step of react and tert-butyl. Particularly suitable alkyls include, methyl, ing a metal halide compound with a triorgano boron com ethyl, n-propyl and iso-propyl. Preferably, each Z is the pound, wherein the metal is Selected from gallium, indium, Same. Suitable aryl groups include, but are not limited to, aluminum, cadmium and zinc. By “organometal compound' phenyl, benzyl, biphenyl, and naphthyl. It will be appreci is meant any organic group-containing gallium, indium, ated by those skilled in the art that the alkyl or aryl group aluminum, cadmium and Zinc compound, Such as trialkyl may optionally be substituted. By “substituted” it is meant gallium compounds, dialkyl gallium halide compounds, that one or more of the hydrogens on the alkyl or aryl group alkyl gallium dihalide compounds, triaryl gallium com are replaced by one or more Substituent groupS. Suitable pounds, trialkyl indium compounds, monoalkyl indium Substituent groups are those that do not contain oxygen and dihalide compounds, dialkyl indium halide compounds, tri that do not adversely affect the reaction. Suitable substituent aryl indium compounds, trialkyl aluminum compounds, groups include, without limitation, (C-C)alkyl, di(C- dialkyl aluminum halide compounds, alkyl aluminum diha Cl)alkyl amino, and phenyl. Triorgano boron compounds US 2004/O122248 A1 Jun. 24, 2004

are generally commercially available from a variety of alkyl metal compound and boron trihalide. This reaction is Sources or may be prepared by a variety of methods known illustrated by the following equation for gallium trichloride in the literature. which is reacted with triethylboron to form triethyl gallium and boron trichloride. 0020 Typically, the metal halide compound is reacted with the triorgano boron compound in an organic Solvent. A wide variety of organic Solvents may optionally be used in 0024 Optionally, the reaction of the metal halide com the present invention, provided that Such organic Solvents do pound with the triorgano boron compound may be per not contain oxygenated Species. It is preferred that Such formed in the presence of a tertiary amine. For example, a organic Solvents are free of oxygen Substitution. It is further tertiary amine may be used with a gallium compound, preferred that the organic Solvents do not contain dissolved particularly when a gallium-nitride layer is desired. A wide oxygen. Particularly Suitable organic Solvents include, but variety of tertiary amines may be used in the present are not limited to, hydrocarbons and aromatic hydrocarbons. invention. Suitable tertiary amines include, but are not Exemplary organic Solvents include without limitation ben limited to, those having the general formula NR'R'R'', Zene; alkyl Substituted benzenes Such as toluene, Xylene, and wherein R, R and R are independently selected from (C-Co.)alkyl benzenes Such as (Co-C)alkyl benzenes; (C-C)alkyl, di(C-C)alkylamino-Substituted (C- alkyl Substituted naphthalenes Such as 1,2-dimethylnaphth C.)alkyl, and phenyl and wherein R' and R may be taken ylene, and (Co-Co)alkyl biphenyls, and aliphatic hydro together along with the nitrogen to which they are attached carbons Such as pentane, hexane, heptane, octane, decane, to form a 5-7-membered heterocyclic ring. Such heterocy dodecane, nonadecane, octadecane, hexadecane, pentade clic ring may be aromatic or non-aromatic. Exemplary cane, eicosane, Squalane, cyclopentane, cyclohexane, and tertiary amines include, but are not limited to, trimethy cycloheptane; and mixtures thereof. Typically, the organic lamine, triethylamine, tri-n-propylamine, tri-n-butylamine, Solvent is benzene, toluene, xylene, (C-C)alkylbenzenes, tri-iso-propylamine, tri-iso-butylamine, dimethylaminocy hexane, heptane, cyclopentane or cyclohexane. It will be clohexane, diethylaminocyclohexane, dimethylaminocyclo appreciated that more than one organic Solvent may be pentane, diethylaminocyclopentane, N-methylpyrrolidine, advantageously used in the present invention. Such organic N-ethylpyrrolidine, N-n-propylpyrrolidine, N-iso-propy Solvents are generally commercially available from a variety lpyrrolidine, N-methylpiperidine, N-ethylpiperidine, N-n- of Sources. Such Solvents may be used as is or, preferably, propylpiperidine, N-isopropylpiperidine, N,N'-dimethylpip purified prior to use. erazine, N,N'-diethylpiperazine, N,N'-dipropylpiperazine, N,N,N',N'-tetramethyl-1,2-diaminoethane, pyridine, pyra 0021 Preferably, such organic solvents are deoxygenated Zine, pyrimidine, and mixtures thereof. Preferred amines prior to use. The Solvents may be deoxygenated by a variety include trimethylamine, triethylamine, tri-n-propylamine, of means, Such as purging with an inert gas, degassing the triso-propylamine, and tri-n-butylamine. In one embodi Solvent in vacuo, or a combination thereof. Suitable inert ment, the tertiary amine is triethylamine or tri-npropy gases include argon, nitrogen and helium, and preferably lamine. It will be appreciated by those skilled in the art that argon or nitrogen. more than one tertiary amine may be used in the present 0022. The molar ratio of metal halide compound to invention. Such tertiary amines are generally commercially trialkylboron compound in the present invention is typically available from a variety of Sources. Such tertiary amines from 4:1 to 1:4, and preferably from 1:1 to 1:1.5, although may be used as is or, preferably further purified prior to use. greater and lesser ratioS may be used. By controlling the See U.S. Pat. No. 4,792,467 (Melas et al.) for a description molar ratio of the metal halide compound to the triorgano of gallium-nitride film deposition. boron compound a variety of alkyl or aryl metal compounds 0025. In general, the metal halide compound, the trior can be prepared. Exemplary alkyl or aryl metal compounds gano boron compound, optional Solvent and any other that can be prepared by the present invention include with optional components, Such as the tertiary amines described out limitation monoalkyl gallium dihalide, dialkyl gallium above, may be added to the reaction vessel in any order. The halide, trialkyl gallium, triaryl gallium, monoalkyl indium reaction mixture is typically Stirred and degassed. The dihalide, dialkyl indium halide, trialkyl indium, triaryl reaction mixture is then typically heated, such as from 30 indium, monoaryl indium dihalide, dialkyl cadmium, to 250° C. and more typically from 40° to 150° C. The monoalkyl Zinc halide, and dialkyl zinc. Such alkyl metal reaction mixture is allowed to react for a period of time compounds may be homoleptic or heteroleptic. Such molar Sufficient to provide the desired organometal compound. ratio determination is well within the ability of those skilled When the reaction is preformed in a batch process, the in the art and will depend upon the particular organometal reaction mixture is typically allowed to react for 0.5 to 48 compound desired. Thus, the present invention also provides hours, and preferably for 1 to 36 hours, and more preferably a method of preparing an organometal compound including for 4 to 12 hours. the Step of reacting a metal halide compound with a trior gano boron compound, optionally in the presence of an 0026. Alternatively, the present reaction may be per organic Solvent free of oxygenated impurities, wherein the formed in a continuous process. For example, the triorgano metal is Selected from gallium, indium, aluminum, cadmium boron compound may be added to the reaction vessel in a and zinc. continuous manner, Such as by bubbling the triorgano boron compound through the metal halide compound or a Solution 0023 The use of metal halides as the starting metal containing the metal halide compound, while continuously compound results in the formation of boron halides, Such as distilling the desired organometal compound, Such as using boron trihalides. When gallium, indium or aluminum triha a conventional two-trap technique. The first trap is typically lide or cadmium or Zinc dihalide is used as the metal maintained at a temperature Sufficient to condense the compound, the present transalkylation reaction produces an desired organometal compound but not Sufficient to con US 2004/O122248 A1 Jun. 24, 2004 dense the boron compound by-product. The Second trap is 0031. A wide variety of organometal compounds may be typically maintained at a temperature Sufficient to condense prepared according to the present process. Exemplary orga the boron-compound by-product. In Such continuous pro nometal compounds have the formula RM, wherein each R ceSS, the metal halide compound Starting compound is also is independently selected from (C-C)alkyl, (C- continuously added to the reaction vessel, either neat or as C.)alkenyl, aryl or halogen, a is the Valence of the metal, and a Solution. M is a metal Selected from gallium, indium, aluminum, cadmium and zinc. Preferably, R is (C-C)alkyl, and more 0027. The boron halide by-products of the present preferably (C-C)alkyl. Exemplary organometal com method typically have low boiling points. For example, pounds include, but are not limited to, trimethylindium, boron trichloride is typically a gas at room temperature. The triethylindium, tri-n-propylindium, tri-iso-propylindium, tri present method is enhanced by removal, preferably continu iso-butylindium, tri-tert-butylindium, tri-n-butylindium, tri ous removal, of the boron halide produced. Preferably, such n-hexylindium, trimethyl gallium, triethyl gallium, tri-iso removal is achieved by distillation, but other suitable meth propyl gallium, tri-n-propyl gallium, tri-iso-butyl gallium, ods, Such as liquid extraction, may be used. In an alternate tri-tert-butyl gallium, tri-Sec-butyl gallium, tri-neo-pentyl embodiment, a catalytic amount of an amine, Such as the gallium, dimethyl Zinc, diethyl cadmium, dimethyl cad tertiary amines described above, may be added to the mium, diethyl Zinc, di-iso-propyl Zinc, di-iso-butyl Zinc and reaction to react with the boronhalide produced to help drive di-tert-butyl Zinc. In particular, the present invention pro the reaction to completion. vides an ultrapure trialkyl gallium or trialkyl indium com 0028. Following reaction, the desired organometal com pound free of ethereal Solvent, oxygenated impurities, Sili pound is Separated from the reaction Solvent or reaction con, aluminum and zinc. Preferred ultrapure trialkyl gallium mixture by any Suitable means Such as extraction, distilla and trialkyl indium compounds are Selected from trimethyl tion, or Sublimation. Any extraction technique known in the gallium, triethyl gallium, tripropyl gallium, tributyl gallium, art may Suitably be used. For example, the organic reaction trimethyl indium, trimethyl indium, tripropyl indium and Solvent may be removed completely, Such as by distillation, tributyl indium. The terms “tripropyl” and “tributyl” are to yield a concentrated reaction mixture. Such reaction meant to include all isomers of propyl and butyl, e.g. the n-, mixture may then be contacted with a solvent for the iso-, Sec-, and tert-isomers as appropriate. organometal compound, or alternatively, a Solvent for the 0032. The present process provides numerous advantages unwanted material Such as cyclopentane or cyclohexane, over conventional organometal compound, particularly alkyl thereby leaving the organometal compound. In another metal compound, preparation methods. These advantages embodiment, the organometal compound may be extracted include: easier processing of reaction products, lowered cost from the organic reaction Solvent using an extraction Sol of raw materials per batch of organometal compounds, vent. Any extraction Solvent that dissolves the organometal increased capacity of alkyl metal compound manufacture, compound is Suitable. Exemplary extraction Solvents increased yield of alkyl metal compounds, improved Safety include, but are not limited to, benzene, lower alkylben due to reduced handling of pyrophoric materials, and lower Zenes Such as toluene, Xylene including all isomerS Such as impurity incorporation in the final product. One disadvan ortho-Xylene, meta-xylene, and para-Xylene, and trimethyl tage of conventional trialkylindium preparatory methods, benzene including all its isomers. such as those in U.S. Pat. No. 5,756,786, is that the high 0029 When the organometal compound is extracted into level of fluoride Salt provides a Suspension in the reaction the extraction Solvent, the desired organometal compound is vessel. Such Suspension makes complete reaction of the obtained by removing the extraction Solvent Such as by Starting materials difficult. In contrast, the present proceSS distillation. Alternatively, the organometal compound may provides a reaction mixture Solution which allows easier be crystallized from the extraction solvent by a variety of handling and mixing of reaction components. known methods. For example, when trimethylindium is 0033. In an alternate embodiment, the present invention prepared according to the present proceSS and extracted provides a method of preparing organometal compounds using a mixture of linear alkyl benzenes, the trimethylin that allows for recycling or reuse of the reaction by-prod dium may be crystallized from the linear alkyl benzene ucts. For example, boron trihalide produced by this reaction Solution by Slowly adding a Small amount of a nonsolvent, may be isolated and re-used, Sold or easily converted into Such as cyclopentane or cyclohexane. The organometal trialkyl boron or trialkyl borate compounds. The boron compound may be purified after recovery/isolation from the trihalide compounds may be reacted with trialkyl aluminum extraction Solvent. In general, trialkylindium compounds are compounds, using conventional reaction conditions, to pro purified by Sublimation in the presence of a fluoride Salt, duce trialkyl boron compounds. Alternatively, the boron particularly potassium fluoride, in a Small amount of Solvent, trihalide compounds may be reacted with an alcohol, Such as Such as Squalane. methanol, to produce trialkyl borate, Such as trimethyl 0030 Alternatively, the organometal compounds may be borate. Such trialkyl boron compounds or trialkyl borate Separated from the reaction mixture by contacting the reac compounds may be further used as is, or may be further tion mixture with an amine or phosphorous compound to purified. Suitable applications for trialkyl borate include form an adduct with the alkyl or aryl metal compound. ceramicS applications. Particularly useful amines are the tertiary amines described 0034. Accordingly, the present invention provides a above. Such adduct may then be isolated, Such as by method for preparing an organometal compound including crystallization, and Subsequently dissociated, Such as by the Steps of reacting a triorgano boron compound with a heating, to provide the Separated organometal compound. metal halide compound, wherein the metal halide includes a Such adduct isolation Step may be performed in a quantita metal Selected from gallium, indium, aluminum, cadmium tive or nearly quantitative yield. and Zinc, to form a boron trihalide compound and the US 2004/O122248 A1 Jun. 24, 2004

organometal compound; isolating the boron trihalide com Substrates are particularly useful in the manufacture of pound; and reacting the boron trihalide compound with an integration circuits and light emitting diodes. organo aluminum compound or an alcohol. Such metal 0039) Deposition is continued for as long as desired to halide compound is preferably a metal dihalide or trihalide produce a film having the desired properties. Typically, the compound. film thickness will be from several hundred to several 0035. The organometal compounds of the present inven thousand angstroms or more when deposition is stopped. tion are Suitable for use as chemical vapor deposition and/or 0040. The present organometal compounds are useful in metalorganic chemical vapor deposition precursor com depositing any film including indium, gallium, aluminum, pounds. The compounds of the present invention are Sub Stantially free of oxygenated impurities, i.e. they contain cadmium, Zinc and alloys of any of these. Suitable films S50 ppm of oxygenated impurities and preferably s25 ppm include, but are not limited to, indium, indium-phosphide of Such impurities. Trialkylindium and trialkyl gallium com (“InP), GaAs, InGaAs, InCaAlP, InGaAsP, InGaAS/GaAs/ pounds produced by the present method are preferably AlGaAs, indium-arsenide ("InAs), indium-antimonide substantially free of detectable levels of silicon, tin, alumi (“InSb”) and indium-arsenic-bismuthide (“InASBi”). num, germanium and Zinc, i.e. they contain <1 ppm and 0041. Thus, the present invention provides a method for preferably <0.5 ppm of such impurities. More typically, such depositing a metal layer on a Substrate including the Steps of: compounds are free of detectable levels of Such impurities. a) conveying an organometal compound in the gaseous phase to a deposition chamber containing the Substrate; b) 0.036 Indium, gallium, aluminum, cadmium or zinc films decomposing the organometal compound in the deposition are typically deposited by first placing the desired indium, chamber; and c) depositing a metal layer on the Substrate; gallium, aluminum, cadmium or Zinc precursor compound, wherein the organometal compound is free of oxygenated or Source compound, in a bubbler, or other delivery device impurities, and wherein the organometal compound includes Suitable for delivering the compounds in the gaseous phase a metal Selected from gallium, indium, aluminum, cadmium having an outlet connected to a deposition chamber. A wide and zinc. Also provided by the present invention is a method variety of bubblers may be used and are well-known to those for manufacturing an electronic device including the Step of skilled in the art. A particularly useful bubbler for Solid depositing a metal layer on an electronic device Substrate Source compounds is that disclosed in U.S. Pat. No. 6,607, including the steps of: a) conveying an organometal com 785 (Timmons et al.). The particular bubbler selected will pound in the gaseous phase to a deposition chamber con depend in part on the particular deposition apparatus used. taining the Substrate; b) decomposing the organometal com The Source compound is maintained in the bubbler as a pound in the deposition chamber; and c) depositing a metal liquid or Solid. Solid Source compounds are typically lique layer on the Substrate; wherein the organometal compound fied or Sublimed prior to transportation to the deposition is free of oxygenated impurities, and wherein the organo chamber. The Source compound is typically transported to metal compound includes a metal Selected from gallium, the deposition chamber by passing a carrier gas through the indium, aluminum, cadmium and Zinc. Such organometal bubbler. Suitable carrier gasses include nitrogen, hydrogen, compounds are typically trialkyl galliums, trialkyl indiums, and mixtures thereof. In general, the carrier gas is introduced trialkyl aluminums, dialkyl cadmiums, dialkyl Zincs and below the Surface of the Source compound, and bubbles up mixtures thereof. through the Source compound to the headspace above it, entraining or carrying vapor of the Source compound in the 0042 Suitable electronic devices include, but are not carrier gas. The entrained or carried vapor then passes into limited to, integrated circuits and light emitting diodes the deposition chamber. (“LEDs"). 0037. The deposition chamber is typically a heated vessel 0043. The following examples are expected to illustrate within which is disposed at least one, and possibly many, various aspects of the present invention, but are not intended substrates. The deposition chamber has an outlet which is to limit the Scope of the invention in any aspect. typically connected to a vacuum pump in order to draw by-products out of the chamber and to provide a reduced EXAMPLE 1. pressure where that is appropriate. MOCVD can be con 0044 Five grams of gallium trichloride and 2.8 g of ducted at atmospheric or reduced pressure. The deposition triethylboron (1:1 molar ratio) are added to a flask equipped chamber is maintained at a temperature Sufficiently high to with a condenser under a nitrogen atmosphere. The reaction induce decomposition of the Source compound. The typical is performed neat, i.e. no Solvent is used. The reaction deposition chamber temperature is from about 300 to about mixture is heated to 50° C. and maintained at that tempera 1200° C., the exact temperature selected being optimized to ture for one hour. The reaction mixture is analyzed by provide efficient deposition. Such optimization is well FT-NMR and shows the presence of triethyl gallium: "H within the ability of one skilled in the art. Optionally, the NMR; 81.08 (CH, t) and 0.45 (CH, q). The chemical shifts temperature in the deposition chamber as a whole can be for triethylboron are also distinguished at Ö=0.91 (CH, t) reduced if the Substrate is maintained at an elevated tem and 1.12 (CH, q). perature, or if other energy Such as radio frequency ("RF") energy is generated by an RF Source. EXAMPLE 2 0.038 Suitable substrates for deposition may be any upon 0045. Five grams of gallium trichloride and 4.2 g of which a film including indium, gallium, aluminum, cad triethylboron (2:3 molar ratio) are added to a flask equipped mium or Zinc is desired, Such as, but not limited to Silicon with a condenser under a nitrogen atmosphere. The reaction Such as Silicon wafers used in integrated circuit manufacture, is performed neat. The reaction mixture is heated to 60° C. gallium arsenide, indium phosphate, and the like. Such for one hour. A slight reflux is observed and a partial takeoff US 2004/O122248 A1 Jun. 24, 2004

distillation head is attached to the flask to collect the EXAMPLE 1.4 refluxing material. The reaction flask is heated to 70° C. and a Small amount of the refluxing material is collected. The 0057 The procedure of Example 1 is repeated except that reaction mixture and the distillate are analyzed by FT-NMR toluene is used as a Solvent. and show the presence of triethyl gallium. EXAMPLE 3 What is claimed is: 1. A method of preparing an organometal compound 0.046 Fifteen grams of gallium trichloride and 8.4 g of comprising the Step of reacting a triorgano boron compound triethylboron is added to a reaction flask equipped with a with a metal halide compound, wherein the metal halide condenser under nitrogen. The reaction mixture is heated at compound comprises a metal Selected from gallium, indium, 100° C. for three hours. A partial takeoff distillation head is aluminum, cadmium and zinc. attached to the reaction flask. The reaction mixture is then 2. The method of claim 1 wherein the organometal heated to 90° C. A small amount of refluxing material is compound is free of oxygenated impurities. collected. The distillate and the refluxing material are ana 3. The method of claim 1 wherein the metal halide lyzed by FT-NMR and show the presence of trimethyl compound has the formula MY wherein each Y is indepen gallium in the distillate. dently halogen, alkyl or aryl; a is the Valence of the metal; and M is gallium, indium, aluminum, cadmium or Zinc, and EXAMPLE 4 at least one Y is halogen. 0047 The procedure of Example 1 is repeated except that 4. The method of claim 3 wherein the metal halide trimethyl boron is used instead of triethylboron to produce compound is a metal trihalide metal compound. trimethyl gallium. 5. The method of claim 1 wherein the triorgano boron compound has the formula ZB, wherein each Z is indepen EXAMPLE 5 dently Selected from halogen, (C-C)alkyl, (C-C)alkenyl 0.048. The procedure of Example 1 is repeated except that or aryl, provided that at least one Z is alkyl, alkenyl or aryl. gallium tribromide is used and Squalane is used as a Solvent. 6. The method of claim 1 further wherein the triorgano boron compound and the metal halide compound are reacted EXAMPLE 6 in an organic Solvent. 0049. The procedure of Example 4 is repeated except that 7. The method of claim 6 wherein the organic solvent is gallium tribromide is used. free of oxygen Substitution. 8. The method of claim 1 wherein the metal is gallium, EXAMPLE 7 indium, or zinc. 0050. The procedure of Example 1 is repeated except that 9. A method for preparing an organometal compound tri-iso-propyl boron is used to produce tri-iso-propyl gal comprising the Steps of reacting a triorgano boron com lium. pound with a metal halide compound, wherein the metal halide comprises a metal Selected from gallium, indium, EXAMPLE 8 aluminum, cadmium and Zinc, to form a boron trihalide 0051. The procedure of Example 2 is repeated except that compound and the organometal compound; isolating the gallium triiodide and trimethyl boron are used to produce boron trihalide compound; and reacting the boron trihalide trimethyl gallium. compound with an organo aluminum compound or an alco hol. EXAMPLE 9 10. A method of preparing a trialkyl gallium compound 0.052 The procedure of Example 7 is repeated except that comprising the Step of reacting a trialkyl boron compound tri-n-propyl boron is used to produce tri-n-propyl gallium. with a gallium trihalide compound. 11. The method of claim 10 wherein the gallium trihalide EXAMPLE 10 compound is Selected from gallium trichloride, gallium 0053. The procedure of Example 1 is repeated except that tribromide and gallium triiodide. Zinc dichloride is used instead of gallium trichloride to 12. The method of claim 10 wherein the trialkyl boron produce diethyl Zinc. compound is Selected from trimethylboron, triethylboron, tripropyl boron and tributylboron. EXAMPLE 11 13. A trialkyl gallium or trialkyl indium compound free of 0.054 The procedure of Example 2 is repeated except that ethereal Solvent, oxygenated impurities, Silicon, aluminum Zinc dibromide is used instead of gallium trichloride to and zinc. produce diethyl Zinc. 14. The compound of claim 13 wherein the trialkyl gallium compound is Selected from trimethyl gallium, tri EXAMPLE 12 ethyl gallium, tripropyl gallium and tributyl gallium. 0.055 The procedure of Example 1 is repeated except that 15. The compound of claim 13 wherein the trialkyl indium trichloride is used instead of gallium trichloride to indium compound is Selected from trimethyl indium, trim produce triethyl indium. ethyl indium, tripropyl indium and tributyl indium. 16. A method of depositing a metal layer comprising the EXAMPLE 13 Steps of: a) conveying a trialkyl gallium or trialkyl indium 0056. The procedure of Example 4 is repeated except that compound of claim 13 in the gaseous phase to a deposition indium trichloride is used instead of gallium trichloride to chamber containing the Substrate; b) decomposing the tri produce triethyl indium. alkyl gallium or trialkyl indium compound in the deposition US 2004/O122248 A1 Jun. 24, 2004 chamber; and c) depositing a layer comprising gallium or 18. The method of claim 16 wherein the trialkyl indium indium on the Substrate. compound is Selected from trimethyl indium, trimethyl 17. The method of claim 16 wherein the trialkyl gallium indium, tripropyl indium and tributyl indium. compound is Selected from trimethyl gallium, triethyl gal lium, tripropyl gallium and tributyl gallium. k . . . .