United States Patent (19) 11 Patent Number: 4,833,103 Agostinelli et al. (45) Date of Patent: May 23, 1989 54 PROCESS FOR DEPOSITING A III-V Crystal Growth of III-V Semiconductors Using Coor COMPOUND LAYER ON A SUBSTRATE dination Compounds as Starting Material in the 75) Inventors: John A. Agostinelli; Henry J. MOCVD Process', Journal of Crystal Growth, vol. 55, Gysling, both of Rochester, N.Y. 1981, pp. 135-144. Maury et al., "Raman Spectroscopy Characterization of 73 Assignee: Eastman Kodak Company, Polycrystalline GaP Thin Films Grown by MO-CVD Rochester, N.Y. Process Using Et2Oa-PEt23 as Only Source', Journal 21 Appl. No.: 62,670 de Physique, Colloque C1, Suppl. No. 10, vol. 43, Oct. 22 Filed: Jun, 16, 1987 1982, pp. C1-347 to C1-252. 51) Int. Cl." ............................................... B05D 5/12 Primary Examiner-Janyce Bell 52 U.S. Cl. .................................. 437/231; 427/108; Attorney, Agent, or Firm-Carl O. Thomas 427/110; 427/123; 427/226; 427/229; 437/234; 437/245 58 Field of Search ................... 427/87, 229, 226, 88, 57 ABSTRACT 427/08, 123, 110,383.7, 383.5, 372.2; 437/104, A process comprising applying to a substrate a thin film 231, 82,234, 245 comprised of a liquid carrier and a precursor selected (56) References Cited from among compounds in which one or more pairs of U.S. PATENT DOCUMENTS group III and V elements are each joined by a thermally stable bond and the group III and V elements are each 3,802,967 4/1974 Ladany et al. ..................... 14.8/171 substituted with two thermally volatilizable ligands. 3,877,982 4/1975 Coldren ............................... 437/234 4,250,205 2/1981 Constant et al. ... 427/87 The precursor is heated to a temperature in excess of 4,427,714 l/1984 Davey ................................... 427/87 200 C. to remove its volatilizable ligands while leaving 4,510,182 4/1985 Cornils ................................ 427/226 a ligand free III-V compound as a monophasic layer on 4,594,264 6/1986 Jensen ................................ 427/53.1 the substrate. OTHER PUBLICATIONS Zaouk et al., "Various Chemical Mechanisms for the 10 Claims, No Drawings 4,833,103 1. 2 MOCVD Process', Journal of Crystal Growth, Vol. 55, PROCESS FOR DEPOSTING AII-V COMPOUND 1981, pp. 135-144 discloses a variation on the process of LAYER ON A SUBSTRATE Constant et all wherein elimination of one ligand from each of the III and V elements of the precursor is recog FIELD OF THE INVENTION nized to occur during heating. Maury et al., “Raman The present invention is directed to a processof pro Spectroscopy Characterization of Polycrystalline Gap ducing a layer of a III-V compound. Thin Films Grown by MO-CVD Process. Using Et2. Ga-PEt3 As Only Source', Journal de Physique, Col BACKGROUND OF THE INVENTION loque C1, suppl. no. 10, vol. 43, Oct. 1982, pp. C1-347 References to Group III, IV, and V elements follow O to C1-252, is essentially cumulative with Constant et al art established designations of elements found in groups and Zaouk et al, except for employing polymeric pre 13, 14, and 15, respectively, of the Periodic Table of cursors as starting materials. Zaouk et al and Maury et elements as adopted by the American Chemical Soci all share the disadvantages of Constant et al. ety. Davey U.S. Pat. No. 4,427,714 describes forming Following the discovery of the transistor, semicon 15 III-V compound layers by spraying. For example, gal ductor application interest focused on group IV ele lium arsenide layers are disclosed to be formed by pro ments, first primarily on germanium and then on silicon. cesses including It was later recognized that useful and, for many appli (1) spraying a solution of gallium arsenide or a pre cations, superior semiconductor properties are pro cursor thereof with an inert gas propellant in a reducing vided by III-V compounds-that is, compounds con gaseous atmosphere; sisting of group III and group V elements. This has led (2) spraying a solution of gallium/arsenic complex to intensive investigations of processes for preparing (each of the gallium and arsenic atoms having three layers of III-V compounds, particularly processes of substituent legands) with an inert gas propellant in an fering the stringent control of III-V compound layer inert or reducing atmosphere; stoichiometry, purity, uniformity, and thickness re 25 (3) creating a stable aerosol of trimethyl gallium dis quired for successful semiconductor applications. The most commonly employed approach for prepar persed in arsine, which is sprayed on a hot substrate; ing III-V compound layers is chemical vapor deposi and tion (CVD), which includes both vapor phase epitaxy (4) spraying a polymeric complex formed between (VPE) and metalorganic chemical vapor deposition 30 trimethyl gallium and methyl/phenyl arsine. All of the (MOCVD). A gaseous compound of a group III ele spraying processes are unattractive, since considerable ment and a gaseous compound of a group V element are unwanted deposition occurs on spray confining walls. introduced into a vacuum chamber and thermally de Thus precursor waste and burdensome cleaning of composed in the presence of a substrate. Although ex equipment is encountered. tensively used, this process exhibits a number of disad 35 It has been recognized that III-V compound layers vantages. First, there is the safety hazard of working can be produced by supplying liquids to substrate sur with toxic gases. Second, each of the group III element faces. Ladany et al U.S. Pat. No. 3,802,967 discloses and group V element compounds are pyrophoric, react first forming a thin III-V compound layer by CVD ing spontaneously with oxygen. Third, with the group techniques and then increasing the thickness of this III and group V elements being introduced as separate layer by conventional liquid phase epitaxy. For in gases, the potential for layers which are stoichiometri stance, in Example 1 a liquid consisting of 97 percent cally unbalanced in either the concentration of the gallium, 2.99 percent gallium arsenide, and 0.01 percent group III or group V element is always present, and tellurium is flowed over a 10 micrometer CVD GaAs precise gas metering is required for balanced stoichion layer on a spinel substrate by tipping a graphite boat etry. Fourth, working with high vacuum equipment is 45 containing the liquid and substrate. The temperature of time consuming, cumbersome, and operationally limit the liquid is maintained at 700° C. The Ladany et al 1ng. process, since it begins with CVD, incurs all of the Constant et al U.S. Pat. No. 4,250,205 discloses a disadvantages of that process and in addition is unat variation on the CVD process described above. Instead tractive in requiring very high temperatures for liquid of employing a gaseous compound of a group III ele SO phase epitaxy. ment and a gaseous compound of a group V element as Jensen U.S. Pat. No. 4,594,264 discloses a process for separate precursors for III-V compound deposition, a preparing gallium arsenide layers on monocrystalline, single gaseous precursor is employed which is a coor gallium arsenide or silicon substrates. A gallium-arsenic dinatin compound of one group III element substituted complex is employed of the formula with three volatilizable ligands and one group V ele 55 ment substituted with three volatilizable ligands. Such (I) X3GaAsR3 coordination compounds are also referred to in the art as III-V donor acceptor complexes and as III-V Lewis where acid and Lewis base adducts. Constant et all teaches X is chlorine, bromine, iodine, phenyl, benzyl, avoiding ligand elimination leading to polymeric com methyl, or trifluoromethyl, and pounds. Although the coordination compound ap R is hydrogen, phenyl, benzyl, methyl, or trifluoro proach offers better replication of ratios of III and V methyl. elements and to some extent ameliorates problems of The complex is dissolved in a hydrocarbon or chlori toxicity and oxygen sensitivity, the limitations of using nated hydrocarbon solvent which is free of oxygen, high vacuum equipment for coating remain unabated. 65 sulfur, and nitrogen. The resulting solution is coated as Zaouk et al, "Various Chemical Mechanisms for the a film on the substrate in an amount sufficient to form a Crystal Growth of III-V Semiconductors. Using Coor gallium arsenide layer of from 1 to a few micrometers dination Compounds as Starting Material in the (um) in thickness. The film is then heated to a tempera 4,833,103 3 4. ture of less than 200 C. to volatilize the solvent while referred to simply as III-V compounds. These com avoiding decomposition of the gallium-arsenic complex. pounds are formed of group III (boron, aluminum, gal The next step of the process is to convert the complex lium, and indium) and group V (nitrogen, phosphorus, coating remaining to gallium arsenide by exposing the arsenic, antimony, and bismuth) elements. The III-V coating to ultraviolet (UV) radiation, such as the UV compound layer can contain one or a combination of radiation from a laser. The presence of moisture and III-V compounds. For example, layers of binary III-V oxygen is avoided. All reactions were carried out under compounds, such as aluminum nitride, aluminum phos an inert, dry atmosphere (typically less than 1 ppm phide, aluminum arsenide, aluminum antimonide, gal oxygen content) using purified, dry, oxygen-free sol lium nitride, gallium phosphide, gallium arsenide, gal vents. Analysis of a layer produced from a complex of 10 lium antimonide, indium nitride, indium phosphide, C13GaAsOC6H5)3 revealed that it had lost only 70 per indium arsenide, indium antimonide, boron nitride, cent of the carbon and 54 percent of the chlorine of its boron phosphide, boron arsenide, and boron antimon parent coating as measured prior to UV exposure.