Coating processes – Electrical product produced – Integrated circuit – printed circuit – or circuit board
Patent
1997-07-14
1999-11-09
Meeks, Timothy
Coating processes
Electrical product produced
Integrated circuit, printed circuit, or circuit board
427 99, 427123, 427124, 427229, 427252, 117103, 117104, C23C 1618
Patent
active
059809787
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is the National Stage of International Patent Application No. PCT/GB95/02089, filed Sep. 4, 1995; which claims priority from Great Britain Application GB94107707.8, filed Sep. 2, 1994 and Great Britain Application GB9508702.9, filed Apr. 28, 1995.
BACKGROUND OF THE INVENTION
This invention concerns semiconductor devices and their production.
While there is a considerable interest in InP/InGaAs devices grown by chemical beam epitaxy (CBE), particularly in the area of selective growth, the GaAs/AlGaAs material system is less well established. With the exception of very encouraging data for heterojunction bipolar transistors (HBT's) and high eletron mobility transistors (HEMTS's) the quality of AlGaAs alloys grown by CBE have generally been inferior to those grown by metalorganic vapor phase epitaxy (MOVPE) or molecular beam epitaxy (MBE). The degradation of material quality results from unintentional moieties of group III metal alkyls and also unintentional oxygen incorporation. Much effort has, therefore, gone into the development of new precursors which reduce unintentional impurity incorporation in epitaxial AlGaAs layers.
A direct correlation has been established between oxygen concentrations unintentionally incorporated into AlGaAs grown by CBE and trace quantities of diethylether detected by in-situ modulated beam mass spectrometry (MBMS) in the group III metalorganic precursors. The trace ether is residual from the synthesis of the metal trialkyl MR.sub.3, which involves the alkylation of the metal trihalide by a Grignard reagent RMgX carried out in an ether solvent. Subsequent purification processes are then performed to remove the oxygen containing ether solvent and other impurities from the metalorganic precursor. However, these processes are never entirely successful.
For example, U.S. Pat. No. 4,464,233 describes the formation of dimethylmagnesium by reacting a Grignard reagent with a metal halide using electrolysis, having tetra(n-butyl) ammonium percholate as an ionizable support electrolyte and a solvent such as an aliphatic ether, cyclic aliphatic mono- or poly- ether or a non-cyclic ether. Similarly, U.S. Pat. No. 4,604,473 discloses a method of producing a trialkylgallium compound by reacting a gallium trihalide with a Grignard reagent in the presence of an ether.
Trimethylindium compounds with nitrogen-containing Lewis-bases have also been prepared using Lewis-base solvents, such as diethyl ether (see Journal of the Chemical Society, Dalton Transactions vol. 1. 1998, USA; Foster et al: "synthesis and thermal properties of trimethylindium with nitrogen-containing Lewis bases") and the interaction of, for example, ethers and amines with trimethylalane adducts is discussed in Inorganic Chemistry vol. 7, no. 6., Jun. 3, 1986, USA pages 1047-1051; C. H. Henrickson et al.
Alternative methods for producing metalorganic precursors for use in the deposition of epitaxial layers have been described in, for example, U.S. Pat. No. 4,812,586 and EP0460598.
BRIEF SUMMARY OF THE INVENTION
A first object of this invention is to provide a method of growing semiconductor layers in which the above-mentioned oxygen impurity problem is eliminated or at least reduced in effect.
A second object of this invention is to provide semiconductor devices in which the above-mentioned oxygen impurity problem is eliminated or at least reduced in effect.
According to a first aspect of the invention there is provided a method of growing semiconductor layers on a substrate comprising the steps of delivering to the substrate, a metalorganic compound of the formula MR.sub.3, R being an alkyl group, prepared by reacting a Grignard reagent with a metal halide, and causing deposition on the substrate of metal from the metalorganic compound, characterised in that reaction of the Grignard reagent with the metal halide is carried out in an amine solvent.
According to a second aspect of the invention there is provided a semiconductor device comprising a layer grown on a s
REFERENCES:
patent: 4464233 (1984-08-01), Mullin et al.
patent: 4604473 (1986-08-01), Cole-Hamilton et al.
patent: 4812586 (1989-03-01), Mullin et al.
Abernathy, Solid-State Electronics, vol. 38, No. 3, pp. 737-738, May 1995.
Freer et al., Advanced Materials, vol. 7, No. 5, pp. 478-481, May 1995.
Inorganic Chemistry, vol. 7, No. 6, Jun. 3, 1986, Henrickson, C.H. et al., "Lewis Acidity of Alanes. Interactions of Trimethylalane with Amines, Ethers, and Phosphines," pp. 1047-1051.
Journal of Chemical Society, Dalton Transactions, vol. 1, 1988, Foster D.F., et al., "Synthesis and Thermal Properties of Adduicts of Trimethylindium with Nitrogen-containing Lewis Bases," pp. 7-11 (no month) .
Freer Richard William
Jones Anthony Copeland
Martin Trevor
Rushworth Simon Andrew
Whittaker Timothy John
Meeks Timothy
The Secretary of State for Defence in Her Britannic Majesty's Go
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