United States Patent (19) 11 Patent Number: 4,734,514 Melas et al. 45 Date of Patent: Mar. 29, 1988 54 HYDROCARBON-SUBSTITUTED ANALOGS Organometallic Compounds of Arsenic, Antimony, and OF PHOSPHINE AND ARSINE, Bismuth, pp. 120-127. PARTICULARLY FOR METAL, ORGANIC Hagihara, et al., Handbook of Organometallic Com CHEMICAL WAPOR DEPOSTION pounds (1968), pp. 560, 566, 571, 574, 579,581. 75 Inventors: Andreas A. Melas, Burlington; Hagihara, et al. Handbook of Organometallic Com Benjamin C. Hui, Peabody, both of pounds (1968), pp. 720-723, 725-726. Mass.; Jorg Lorberth, Kisolapoff, et al., Organic Phosphorus Compounds, Weimar-Niederweimar, Fed. Rep. of vol. 1, pp. 4-11, 16-27. Germany Kuech, et al. "Reduction of Background Doping in Metal-Organic Vapor Phase Epitaxy of GaAs using 73) Assignee: Morton Thiokol, Inc., Chicago, Ill. Triethyl Gallium at Low Reactor Pressures', Appl. 21 Appl. No.: 828,467 Phys. Lett., Oct. 15, 1985. TZSchach, et al., Zur Sythese Zeitschrift fur Anorganis 22 Filed: Feb. 10, 1986 che und Allgemeine Chemie, Band 326, pp. 280-287 (1964). Related U.S. Application Data Primary Examiner-Paul F. Shaver 63 Continuation-in-part of Ser. No. 664,645, Oct. 25, 1984. Attorney, Agent, or Firm--George Wheeler; Gerald K. 5ll Int. Cl* ................................................ CO7F 9/70 White 52 U.S.C. .......................................... 556/70; 568/8; 57 ABSTRACT 568/17 58 Field of Search ........................ 556/70,568/8, 17 Organometallic compounds having the formulas: 56 References Cited U.S. PATENT DOCUMENTS x-y-y H 3,657,298 4/1972 King et al......................... 556/7OX OTHER PUBLICATIONS wherein N is selected from phosphorus and arsenic, His Kosolapoffetal, Organic Phosphorus Compounds, vol. hydride, and X and Y are independently selected from 1, pp. 109, 110, 111, 114 to 119 (1972) Wiley-Inter hydride, lower alkyl cyclopentadienyl, and phenyl, science, N.Y. except that Y cannot be hydrogen; and Kosolopoff, Organophosphorus Compounds, John Wiley & Sons, Inc., N.Y., pp. 30, 31 (1950). MR Doak et al, Organometallic Compounds of Arsenic, Antimony and Bismuth, Wiley-Intersc., N.Y., pp. 126 (1970). wherein x is an integer from 2 to 4 inclusive, each said Chemical Abstracts 100 174916b (1984). R substituent is independently selected from hydride, Chemical Abstracts 100 121221q (1984). lower alkyl, phenyl, alkyl-substituted phenyl, cyclopen Chemical Abstracts 86 89943t (1977). tadienyl, and alkyl-substituted cyclopentadienyl, and M Ashe, et al., Preparation ... Dibismuthines, Organome is selected from elements of Groups 2B, 2A, 3A, 5A, tallics 1983, No. 2, p. 1865, Cols. 1-2 (synthesis of ben and 6A of the Periodic Table, except carbon, nitrogen, zyldimethylarsine). oxygen, and sulfur. The use of these compounds in Chemical Abstracts 60:14536e. chemical vapor deposition processes and methods for Chemical Abstracts 62:11405g (1965). synthesizing these compounds are also disclosed. CRC Handbook of Chemistry and Physics, 61st Ed. (1980–81), pp. 640-676. 43 Claims, 6 Drawing Figures U.S. Patent Mar. 29, 1988 Sheet of 4 4,734,514 2 s 3 8 NOISSWSNW A. U.S. Patent Mar. 29, 1988 Sheet 2 of 4 4,734,514 tv'6|-! 2'5|- U.S. Patent Mar. 29, 1988 Sheet 3 of 4 4,734,514 am - O 2 s S. 3 3 8 S. S NOSSWSNW. A. U.S. Patent Mar. 29, 1988 Sheet 4 of 4 4,734,514 s 4,734,514 1. 2 operate the MOCVD apparatus, the carrier gas is intro HYDROCARBON-SUBSTITUTED ANALOGS OF duced into the bubbler under the surface of the organo PHOSPHINE AND ARSINE, PARTICULARLY FOR metallic compound. Rising bubbles of the carrier gas METAL, ORGANIC CHEMICAL WAPOR provide a large, constant contact surface and thus uni DEPOSITION formly vaporize the organometallic compound. The carrier gas and vapor collected in the headspace of the CROSS-REFERENCE TO RELATED bubbler are continuously directed to the deposition APPLICATION chamber. This application is a continuation-in-part of U.S. Ser. While it is possible to vaporize solid sources of ar No. 664,645, filed Oct. 25, 1984 by Hui, Melas, and O senic or phosphorus in a bubbler or furnace (see Bhat, Lorbeth, now pending. cited later), this way of providing arsenic orphosphorus has several disadvantages. First, when a III-V com TECHNICAL FIELD pound such as gallium arsenide is to be deposited the This invention relates to organometallic compounds Group III element (here, gallium) is conventionally comprising elements from Groups 2B, 2A, 3A, 5A, and 15 supplied from an organometallic compound such as 6A of the Periodic Table and mixed organic substituents trimethylgallium. The source of the Group V element selected from lower alkyl, hydride, phenyl, alkyl-sub should include hydride substituents so that monatomic stituted phenyl, cycloalkyl, and alkyl-substituted cyclo hydrogen will be formed when the hydride decomposes alkyl; particularly to analogs of arsine (AsH3) and phos in the deposition chamber. The monatomic hydrogen phine (PH3) in which one or two of the hydride substit 20 thus formed will react with the organic radicals (methyl uents is replaced by an organic substituent. This inven radicals, in the case of trimethylgallium) formed by tion also relates to metal organic chemical vapor depo decomposition of the Group V source in the deposition sition (MOCVD) processes employed in the semicon chamber to form gaseous waste (here, methane gas), ductor, optical, and optoelectronic industries for doping allowing the organic constituents to be removed from or coating a suitable substrate. 25 the site of deposition. For this reason, in prior practice BACKGROUND ART a large excess of Group V hydride (here, arsine) has MOCVD is a method for depositing dopants or thin been supplied to ensure thorough removal of organic metal or metal compound films on a silicon or other constituents. Elemental arsenic supplied to the deposi substrate. (In the present disclosure "metal' includes all 30 tion chamber would include no hydride substituents, of the elements of Groups 2B, 2A, 3A, 4A, 5A, and 6A and thus the resulting film would be contaminated with of the Periodic Table except carbon, nitrogen, oxygen, carbon from the Group III source. and sulfur.) The deposited films can be sources of dop Second, it is difficult to control the rate of vaporiza ing impurities which are driven into the substrate, or the tion of such solid sources because the surface area of a films themselves can have different electrical or optical 35 solid exposed to the carrier gas changes as vaporization properties than the substrate. These films are used in proceeds. In contrast, a liquid contained in a bubbler laser diodes, solar cells, photocathodes, field effect tran with substantially vertical walls presents the same sur sistors and other discrete devices, in fiber optic commu face area to the carrier gas so long as the flow and nications, microwave communications, digital audio bubble size of the carrier gas remains steady. Also, gases disc systems, and other advanced semiconductor, opti 40 (defined here as materials having a vapor pressure cal, and optoelectronic technologies. The properties of which exceeds the pressure within the bubbler at conve the film depend on the deposition conditions and the nient bubbler temperatures) are not preferred for chemical identity of the deposited film. MOCVD because gases cannot be evaporated at a uni A special advantage of MOCVD is that organometal form rate in a bubbler. For example, arsine and phos lic compounds can be found which have much higher 45 phine have been supplied as gases in pressurized cylin vapor pressures at moderate temperatures than the cor ders and metered directly into the deposition chamber. responding metals, and which decompose to release the Organometallic compounds for MOCVD desirably corresponding metals or form compounds thereof at the are liquids at bubbler pressure and at a temperature 200 to 800 degrees Celsius deposition temperatures between about -20 C. and about 40 C. Such con which should not be exceeded during fabrication. 50 pounds also should have a vapor pressure of at least Typical apparatus currently in use for MOCVD com about 1.0 torrs at the bubbler temperature, boil and prises a bubbler which contains a supply of the organo decompose at temperatures substantially exceeding the metallic compound chosen for a particular process, a bubbler temperature, and decompose readily at the reactor or deposition chamber which contains the sub temperature encountered in the deposition chamber. strate on which a film is to be deposited, a source of a 55 Another problem facing practitioners of MOCVD is carrier gas which is inert to the organometallic com that arsine and phosphine, commonly employed as pound in the bubbler and either inert or reactive to the sources of arsenic- and phosphorus-containing deposi compound in the deposition chamber, and optionally tion products, are highly toxic. They have been the sources of other reactants or dopants supplied to the subject of proposed and existing restrictive legislation. reaction chamber. The bubbler and contents are main 60 The triorganometallic compounds previously proposed tained at a constant and relatively low temperature to replace them, such as trimethylarsine, are far less which typically is above the melting point of the or toxic, but leave residual carbon decomposition products ganometallic compound but far below its decomposi in the deposited films. (See Bhat, “OMCVD Growth of tion temperature. The deposition chamber is typically GaAs and AlGaAs Using a Solid as a Source', Journal maintained at a much higher temperature, such as about 65 of Electronic Materials, Vol. 14, No. 4, 1985, pp.433-449. 200 to 800 degrees Celsius, particularly about 600 to 750 Kuech, et al. "Reduction of Background Doping in degrees Celsius, at which the organometallic compound Metal-Organic Vapor Phase Epitaxy of GaAs Using readily decomposes to release its constituent metal.