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Method for Reducing Mass Interference in Mass Spectroscopic Measurements

IP.com Disclosure Number: IPCOM000041668D
Original Publication Date: 1984-Feb-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Hu, SM: AUTHOR

Abstract

In mass spectroscopic analysis the detectability of a species of interest may be limited by a background signal of an entirely different species which happens to have the same mass. For example, a sputtering process often yields polyatomic fragments in addition to monatomic (or ions derived from monatomic) particles. An example is the sputtering of silicon and oxygen wherein a fraction of the sputtered material will be in the form of a silicon-oxygen cluster of the formula Si2O. A further fraction (0.03 x 0.046) of this will be 29Si 30SiO, which has a mass of 75. This mass interferes with the mass-spectroscopic analysis of arsenic, also of mass 75. Arsenic is often found in silicon semiconductors as a dopant.

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Method for Reducing Mass Interference in Mass Spectroscopic Measurements

In mass spectroscopic analysis the detectability of a species of interest may be limited by a background signal of an entirely different species which happens to have the same mass. For example, a sputtering process often yields polyatomic fragments in addition to monatomic (or ions derived from monatomic) particles. An example is the sputtering of silicon and oxygen wherein a fraction of the sputtered material will be in the form of a silicon-oxygen cluster of the formula Si2O. A further fraction (0.03 x 0.046) of this will be 29Si 30SiO, which has a mass of 75. This mass interferes with the mass-spectroscopic analysis of arsenic, also of mass 75. Arsenic is often found in silicon semiconductors as a dopant. The interference problem may be overcome by providing means which break up these polyatomic particles during sputtering. One such means is a light source of sufficient energy. The Si-Si bond energy is about 2.0 eV. Therefore, an intense light source of energy greater than about 2.0 eV is provided to flood the sputtering chamber during the deposition process. As soon as the polyatomic particles emerge from the target, many or most of them can be broken into smaller or monatomic particles. The interference problem encountered in mass- spectroscopic analysis is thereby removed.

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