Low-Temperature Organometallic Chemical Vapor Deposition of Transition Metals
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LOW-TEMPERATURE ORGANOMETALLIC CHEMICAL VAPOR DEPOSITION OF TRANSITION METALS Herbert D. Kaesz,* R. Stanley Williams,* Robert F. Hicks,t Yea-Jer Arthur Chen,* Ziling Xue,* Daqiang Xu,* David K. Shuh* and Hareesh Thridandamt *Departmentof Chemistry & Biochemistry - UCLA - Los Angeles, CA 90024-1569 tDepartmentof Chemical Engineering - UCLA - Los Angeles, CA 90024-1592
ABSTRACT A variety of transition-metal films have been grown by organometallic chemical vapor deposition (OMCVD) at low temperatures using hydrocarbon or hydrido-carbonyl metal complexes as precursors. The vapors of the metal complexes are transported with argon as the carrier gas, adding H2 to the stream shortly before contact with a heated substrate. High-purity platinum films have been grown using (il'-CH 5 )PtMe 3 [1] or (rI5 -CH 3C5 H4 )PtMe 3 [2] at substrate temperatures of 180 0C or 120 0C, respectively. The incorporation of a methyl substituent on the cyclopentadienyl ligand decreases the melting point of the organoplatinum complex from 106'C [1] to 30'C [2] and increases the vapor pressure substantially. Film deposition also occurs at a lower substrate temperature. Analyses by X-ray diffraction (XRD), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) indicate that the films are well crystallized and do not contain any observable impurities after sputter cleaning. The substrate temperatures for the first appearance of other transition-metal films from organometallic precursors are as follows ('C): Rh(i13-C 3H5 )3 (120/Si), Ir(71 3-C 3 H5 ) 3 (100/Si), HRe(CO) 5 (130/Si) and Niil 5-CH 3 CsH 4 )2 (190/glass, 280/Si). These films are
essentially amorphous and contain trace oxygen impurities (< 2%), except for the Re film, which was 10% oxygen and 20% carbon.
INTRODUCTION Low-temperature deposition processes are desired for very large-scale integrated (VLSI) microelectronics to reduce wafer warpage, generation of defects, and redistribution of dopants(s). Organometallic chemical vapor deposition (OMCVD) often provides routes to desired materials at lower temperature than possible with corresponding inorganic precursors. The difficulties of deposition of most transition metals using CVD are, (a) the non-availability of volatile precursors and, (b) the high temperatures required to decompose the precursors. However, the possibilities of large throughput and good step coverage are so attractive that attempts continue to be made to find ways to deposit transition metals using OMCVD at low temperature. SELECTION OF SOURCE MATERIALS Much of the previous work involved transition metal complexes of acac (acetylacetonate), carbon monoxide, halogens and/or PF3 [1-5]. These precursors frequently led to incorporation of heteroatoms into the films, and otherwise unsuitable results. Based on earlier observations in this laboratory [6] and elsewhere [7,8] of the decomposition of metal carbonyl and/or hydrocarbon complexes under an atmosphere of hydrogen, we were prompted to examine such derivatives for OMCVD in the presence of H2 .
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