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Title: Semiconductor device having a Schottky junction and method of manufacturing same
Claims: What is claimed is: 1. A semiconductor device having a rectifying metal-to-semiconductor junction, and produced by the method comprising: a. providing a semiconductor body having a first conductivity region adjoining a surface of said body; b. providing a first metal layer on only the surface of said first region to form a rectifying junction; c. providing a second metal layer on said first metal layer and out of contact with said first region surface, said first and second layers comprising a layer structure, the respective said metals of said first and second layers being different from each other and being characterized by being capable of individually forming a rectifying junction with said semiconductor material of said region when disposed directly thereon, the ultimate barrier height of the junction between said first metal layer of said layer structure and said region being larger than the barrier heights of the respective junctions of said metals individually with said semiconductor material of said region; and then d. subjecting the thus-produced assembly to a thermal treatment of at least 400.degree.C, whereby said ultimate barrier height is attained. 2. A semiconductor device as in claim 1, wherein said barrier height of said first metal relative to the said region is lower than that of said second metal. 3. A semiconductor device as in claim 2, wherein said semiconductor material of said region is n-type silicon and said first metal layer consists essentially of nickel and said second metal layer consists essentially of aluminum. 4. A semiconductor device as in claim 2, wherein said semiconductor material of said region is n-type silicon and said first metal layer consists essentially of cobalt and said second metal layer consists essentially of aluminum. 5. A semiconductor device as in claim 2, wherein said first metal layer consists essentially of one of nickel and cobalt and has a thickness of substantially 0.1 micron and said second metal layer consists essentially of aluminum and has a thickness of substantially 1 micron. 6. A semiconductor device as in claim 1, wherein said body comprises a field effect transistor and said metal layers constitute a gate electrode therefor, said semiconductor region consisting of an epitaxial layer provided on a substrate of said first conductivity type. 7. A method of manufacturing a semiconductor device having a rectifying metal-to-semiconductor junction, comprising the steps of: a. providing a semiconductor body having a first region adjoining a surface of said body; b. providing a first metal layer on only the surface of said first region to form a rectifying junction; c. providing a second metal layer on said first metal layer and out of contact with said first region surface, said first and second layers comprising a layer structure, the respective said metals of said first and second layers being different from each other and being capable of individually forming a rectifying junction with said semiconductor material of said region, when disposed directly thereon, the metal of said first layer of said layer structure exhibiting a barrier height relative to the semiconductor region which is lower than that of the metal of said second layer, and then d. subjecting the thus-produced assembly to a thermal treatment of at least 400.degree.C, so as to provide a rectifying junction between said region and said layer structure having a barrier height exceeding those of the junctions individually formed by said first and second layers. 8. A method as in claim 7, wherein said step of forming said first metal layer comprises forming a nickel layer on an n-type silicon said region and said second metal layer is formed by providing an aluminum layer on said nickel first layer. 9. A method as in claim 7, wherein said step of forming said first layer comprises forming a cobalt layer on an n-type silicon said region and said second metal layer is formed by providing an aluminum layer on said cobalt first layer. 10. A method as in claim 7, wherein said step of thermally treating said assembly is carried out at a temperature of at most about 577.degree.C. 11. A method as in claim 10, wherein said temperature treatment step is carried out at substantially 500.degree.C. 12. A method as in claim 7, wherein said two metal layers are vapor-deposited successively in single vapor deposition operation. 13. A method as in claim 7, wherein a field effect transistor is produced, wherein said step of forming said semiconductor body comprises the steps of epitaxially forming a layer of n-type silicon on a substrate of opposite conductivity type, and said method further comprising the steps of forming source and drain electrodes of said epitaxial layer, and wherein said first and second metal layers are provided on the epitaxial layer between said source and drain electrodes. 14. A semiconductor device as in claim 1, wherein said body comprises a field effect transistor and said metal layers constitute a gate electrode therefor, said body comprising a substrate of said first conductivity type, an epitaxial layer of a second opposite conductivity type disposed on said substrate, and said first conductivity region disposed at said epitaxial layer. Other info: Inventors: Landheer, Frits (Eindhoven, NL) Wilting, Hermanus Josephus Henricus (Eindhoven, NL) Application Number: 547997 Filing Date: 1975-02-07 Publication_date: 1976-01-27 Assignee: U.S. Philips Corporation (New York, NY) Primary Class(es): 257/260 257/280, 257/486, 438/167, 438/571, 438/573 Other Classes: US Patent Ref:
Other Refs: Other References: Sze, Physics of Semiconductor Devices, Wiley & Son, N.Y., 1969, pp. 366-367. | |