8.1.1 Movement of the charged particles in plasma of the abnormal glow discharge
The trajectory of electron movement in plasma of magnetron sputtering systems is very complicated, and it is practically impossible to describe it analytically taking into account all components of movement. The quantitative account of complicated movement of charged particles in gas is usually carried out by their decomposition on two components: chaotic (diffusion) and directed movement. Prevalence of this or that kind of movement depends on pressure of gasр and intensity of the electric fieldЕ working in the field of the discharge. Criterion of an estimation of the character of particles movement is ratioЕ/р. If value of this ratio is great, the directed movement under action of an electric field [25, 39] is prevailing.
Volumetric charges and narrow areas of cathode and anode potential drop for which high values of electric field tencity are typical exist in magnetron sputtering systems working at rather low pressure. Therefore valueЕ/р is great (exceeds 105 V/m·Pa), that allows to count electron and ion movement in plasma of magnetron sputtering systems to be directed.
The important parameter of plasma, determining its condition is Debye radius of shielding λD on which the sphere of influence of the allocated trial charge depends [39]:
λD = 49·(T/n)1/2 (8.1)
where Т — temperature, К; n — electron concentration (or ion concentration) in plasma, m-3. Debye number ND, i.e. number of particles in Debye sphere, is usually used as a measure of plasma faultiness:
ND=(4π/3)·n λ3D. (8.2)
This value for magnetron sputtering systems is great (more than 102), that allows to count plasma of discharge the ideal gas consisting of charged particles, , i.e. action of particles among themselves can be neglected.
The basic type of movement of the charged particle in a plane, perpendicular to the magnetic field, is the cyclotron rotation described in the following parameters:
, 
(8.3)
where гл – radius
of rotation of a particle (larmor radius), m;
- a component of speed of
a particle in the direction, perpendicular to field lines of the magnetic
field, km/s;ω
- cyclotron
frequency, c-1; е - an electron charge Kl; z - frequency rate of a
particle charge; B - induction of the magnetic field, Тl;m
- weight of a
particle, kg.
Joint action of electric and magnetic fields causes drift of the charged particle in the direction, perpendicular to both electric, and magnetic fields with a speed
vн=E/B (8.4)
where Е — intensity of the electric field, V/m.
At movement in homogeneous electric and magnetic fields without initial speed the trajectory of a particle represents a cycloid which height is equal to two larmor radiuses::
hц = 2mE/ezB2. (8.5)
Other types of drift movements can exist in the crossed electric and magnetic fields, for example gradient and centrifugal drifts, caused by heterogeneity of a magnetic field and a curvature of its field lines. Speeds of these kinds of movements depend on weight and a charge of a particle that results in division of charges and occurrence of currents. Total speed of drift of the charged particle in the magnetic stream with the bent field lines is composed from speeds of gradient and centrifugal drifts:
(8.6)
where n – an individual vector in the direction B;v // - speed of movement of a particle in the direction parallel with B, km/s.
Both electric, and magnetic fields are considered to be non-uniform in magnetron systems, and that’s why there are all just listed types of drift movements of the charged particles.
8.1.2 Definition of characteristics of the discharge gap
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