Rf-powered glow discharge

Shick et af used radio frequency powered glow discharge atomization/ionization mass spectrometry (Rf GDMS) for the characterisation of bulk polymers. Fingerprint mass spectra were obtained for a series of polytetrafluoroethylene based polymers by looking at the differing base peaks and relative peak intensities. The technique exhibited excellent discharge stabilization and internal stability characteristics with a relative... 

To maintain reproducible excitation conditions in the glow discharge source, the working conditions (e. g. argon pressure, dc-current or rf-power) are carefully controlled. 

The radio-frequency glow-discharge method [30-34] has been the most used method in the study of a-C H films. In this chapter, it is referred to as RFPECVD (radio frequency plasma enhanced chemical vapor deposition). Film deposition by RFPECVD is usually performed in a parallel-plate reactor, as shown in Figure 1. The plasma discharge is established between an RF-powered electrode and the other one, which is maintained at ground potential. The hydrocarbon gas or vapor is fed at a controlled flow to the reactor, which is previously evacuated to background pressures below lO"" Torr. The RF power is fed to the substrate electrode... 

Silicon. The most widely studied and perhaps the best understood PECVD film is that of amorphous silicon (a-Si). Glow discharge a-Si is an alloy of silicon and hydrogen, with the hydrogen content ranging from 5 to 35 atom percent (atom %), depending upon the deposition conditions (temperature, rf power, rf frequency, etc.) and the resulting film structure. 

Current commercial plasma-enhanced CVD reactors operate with only two physical concepts. In one case, we have the inductively-excited discharge in a tube, which is used for plasma ashing of resist. The other is the parallel plate arrangement using high-frequency RF power to create a low-pressure glow discharge, where the wafers to be coated sit on one of the electrodes. 

Analytical glow discharges have conventionally operated with a constant negative dc potential applied to the cathode. There is no reason, however, that they can t be operated through the application of a pulsed potential, an applied rf potential, or a positive potential applied to the cathode. Many variations have been tried alone and in combination with one another. Perhaps the most interesting among these (because of the unique capabilities that it provides) is the radio-frequency-powered discharge. The analysis of nonconductors is covered extensively in a later chapter, but a brief overview is in order here. 

Figure 9 Radio frequency glow discharge mass spectrometry (rf GD-MS) spectrum of a 1.5-mm-thick polytetrafluoroethylene (PTFE) sample (rf power = 20 W, Ar pressure = 0.075 mbar, logarithmic units of ion signal current). (From Ref. 70.)...

---