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Improved Technique for Cleaning Silicon

IP.com Disclosure Number: IPCOM000039151D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 38K

Publishing Venue

IBM

Related People

Harper, JM: AUTHOR [+2]

Abstract

Obtaining an atomically clean surface is often a prerequisite to any controlled growth or deposition process such as molecular beam epitaxy (MBE). One method that is often used is sputter clean where an energetic beam of inert gas ions is used to take off the first few surface layers of the substrate. The sputtering action introduces lattice displacement at the surface and also causes penetration of the sputtering species into the subsurface. The damage may be annealed out, but the residual implanted gas is difficult to eliminate at all but very high temperatures. This leads to defective film growth and also voiding at the interface between substrate and grown film [1]. Higher temperature post sputter heat treatment is often incompatible with other processing requirements. In references [2] and [3], Kugimiya et al.

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Improved Technique for Cleaning Silicon

Obtaining an atomically clean surface is often a prerequisite to any controlled growth or deposition process such as molecular beam epitaxy (MBE). One method that is often used is sputter clean where an energetic beam of inert gas ions is used to take off the first few surface layers of the substrate. The sputtering action introduces lattice displacement at the surface and also causes penetration of the sputtering species into the subsurface. The damage may be annealed out, but the residual implanted gas is difficult to eliminate at all but very high temperatures. This leads to defective film growth and also voiding at the interface between substrate and grown film [1]. Higher temperature post sputter heat treatment is often incompatible with other processing requirements. In references
[2] and [3], Kugimiya et al. and Tabe describe a technique of Si surface cleaning in which Si atoms are deposited onto the Si surface which is covered with a thin native oxide. The depositing flux of Si atoms reduces the native oxide to SiO, which is volatile at a temperature of about 800o Celsius. This technique eliminates the inert gas entrapment problem. The disadvantages of this technique, however, is that the process window where surface cleaning occurs without any silicon deposition is fairly narrow. This publication describes an improved technique that consists of incorporating an ion beam sputter deposition source into the Si processing system, and using the process of ion beam sputtering to produce an energetic Si atom flux. This energetic flux of Si atoms is used to perform the sputter cleaning and oxide reduction necessary to give a clean surface. The advantage is the elimination of implanted gas, and a lower cleaning temperature achieved by the energy of the incident Si atoms. An embodiment of the invention is shown in the figure, which shows an MBE system for the preparation of Si device structures. The ion beam sputtering source is shown directed at a Si target, to produce a deposition flux of energetic Si atoms onto the Si substrate. Ion beam sputtering is chosen because of the energy range of sputtered Si atoms ejected from the target. This sputtered atom energy is typically several eV to tens of eV, and is maintained until impact with the surface,...