TABLE OF CONTENTS The understanding of glow discharges is important in order to master the sputter deposition system since virtually all of the energetic incident particles originate in the plasma.
In this chapter, the basic concepts of the glow discharge are given, after which the construction and operation of the sputtering deposition system are described.
In a diode gas-discharge tube, the minimum voltage, which initiates the discharge, i.e., the spark or breakdown voltage, V s, is given by
| (4.1) |  |
where p is the gas pressure, l is the electrode spacing, and a and b are constant. The relationship between spark voltage, V s, and the gas pressure, p, is called Paschen's Law. A typical experimental result is shown in Fig. 4.1, which shows the existence of minimum spark voltage at gas pressure p m.[1]
In a conventional sputtering system, the gas pressure is kept below the pressure p m. To initiate the discharge, the gas pressure, p s, under a given electrode separation, l, is expressed by
| (4.2) |  |
where ? 0 is the mean free path of electrons in the discharge gas, given by ? 0 = 1/ p c, where p c denotes the elastic collision cross section between electrons and gas atoms. The p c values for Ne,...
