Semiconductor and thin film applications of a quadrupole mass spectrometer

Abstract

Commercial quadrupole mass spectrometer (QMS) residual gas analyzers became available in the late 1960s and have been popular in R&D laboratories, but have found limited use in semiconductor manufacturing. To sample at pressures above 10−5 Torr with ppm sensitivity or better (relative to the total process pressure), differential pumping is usually required. The newly available, small, high-pressure QMS sensors can operate as high as 10–20 mTorr without differential pumping, but provide somewhat lower mass resolution and partial pressure sensitivity than a standard QMS. Applications in semiconductor manufacturing include equipment monitoring, process monitoring, and effluent analysis. Equipment monitoring can include qualification after preventative maintenance, rate-of-rise tests, and leak identification and detection. Usually the burning question is, Why won’t the vacuum chamber pump down? Other uses that are not usually considered include the qualification of replaceable parts: sputter cathodes, electrodes, lamps, shields, etc. In process monitoring, the key question is, Is this process running normally? A manufacturing monitor can be useful simply by providing a comparison between a well-behaved high-yield process and a marginal or failing process. Examples are given for physical vapor deposition (sputtering) processes, chemical vapor deposition, and plasma etching. The effluent from chemical vapor deposition and plasma etch processes can be analyzed to measure the efficiency of process gas utilization or to monitor the efficacy of abatement methods used for the removal of global warming gases.

In Situ Selectivity and Thickness Monitoring During Selective Silicon Epitaxy Using Quadrupole Mass Spectrometry and Wavelets

“…Quadrupole mass spectrometry is one in situ sensing and monitoring technology that has been used increasingly in recent years [2]. Some recent real-time applications of QMS include: in situ feedback control of a plasma enhanced chemical-vapor deposition (PECVD) process (Knight [3] and Greve et al [4]), sidewall spacer etching (Min [5]), endpoint uniformity sensing and analysis during silicon dioxide plasma etching (Chambers et al, [6], [7]), monitoring of a tungsten metal CVD process (Kobayashi et al [8]), process sensing and metrology in amorphous and selective area silicon plasma deposition (Chowdhury et al [9]), process sensing during rapid thermal chemical-vapor deposition (RTCVD) of polysilicon (Rying et al [10], Tedder [11], [12], Smith [13], Lu [14], [15], and Rubloff et al [16]), and more recently in situ monitoring and characterization of RTCVD thin oxide (SiO ), nitride (Si N ), and tungsten (W) films (Lu et al [17], Rying et al [18], and Gougousi et al [19], [20]).…”

Simulation of a QMS Including the Effects of Pressure in the Electron-Impact Ion Source

“…The resulting fragmentation pattern, together with residual molecular ions, results in a mass spectrum that can be used as a "fingerprint" to characterize the analyte. This way, the application of mass spectrometers became widespread for residual gas analysis (RGA) in the study of kinetic reactions, biological analysis, biochemistry, explosives, and in the oil and gas industry [1], [2]. Mass spectrometry (MS) has also the potential to provide accurate mass measurements for low molecular weight compounds (gases) to large macromolecules.…”

Chamber in-situ estimation during etching process by SiF4 monitoring using laser absorption spectroscopy

“…12) Typical sensing methods for monitoring etching processes include optical emission spectroscopy (OES) [16][17][18][19][20][21] and quadrupole mass spectrometer (QMS). [20][21][22][23][24] Although OES can measure a large number of exited species simultaneously at high speed, its detection limit is not sufficient for use in some recent device structures with low open-areas and/or high aspect ratio (HAR). 19,25) In addition, quantitative measurement is difficult because of interference from adjacent emission peaks and degradation based on optical window coating and roughening.…”