CN102156001A - Method for diagnosing self-biased probe of radio-frequency discharge plasma - Google Patents

Abstract

The invention relates to a method for diagnosing a self-biased probe of a radio-frequency discharging plasma, belonging to the field of plasma science and technology. The method is characterized in that two probes, namely, a probe a and a probe b, are arranged in the plasma; the probe a is arranged in a floating state relative to the discharging circuit of the plasma; the probe b is connected with a discharging circuit ground by a blocking capacitor and a sampling capacitor. The voltage alternating-current component amplitude DeltaV between the probe a and the probe b, the first harmonic amplitude absolute value of i1Omega and the secondary harmonic amplitude absolute value of i2Omega of the current of the probe b can be measured; and the electronic temperature Te and the ion density ni can be calculated according to DeltaV, absolute value of i1Omega and absolute value of i2Omega. The method has the benefits of overcoming the influence of the insulating pollution of the probe surface and obtaining the parameters such as the ion density, electronic temperature and the like. The discharge disturbance on the plasma is small as the direct current or alternating-current bias voltage is not applied to the probe.

Description

A kind of rf (discharge) plasma automatic biasing probe diagnostics method

Technical field

The invention belongs to plasma science and technical field, relate to a kind of rf (discharge) plasma automatic biasing probe diagnostics method, be used to diagnose rf (discharge) plasma, can overcome the influence that the detecting probe surface insulation is polluted, obtain parameters such as ion concentration and electron temperature.

Background technology

The common method of diagnosis plasma parameter is that a probe is placed plasma and adds the scanning bias voltage, and the volt-ampere characteristic that measurement and analysis probe electric current change with the scanning bias voltage obtains the parameters of plasma.A serious limitation of this method is the reactive plasma that can not be used for having the insulation film deposition to take place, because detecting probe surface can be insulated product and covers in this case, and can't collected current and lost efficacy.

At this problem, people such as Lee disclose a kind of plasma diagnostic method [M.H.Lee of floating probe, et al., J.Appl.Phys.v101, p033305 (2007)], add high frequency AC bias voltage to probe, utilize the fundamental frequency of probe current and second harmonic amplitude to calculate electron temperature and ion concentration.Because this probe relies on displacement current work, even detecting probe surface exists pollution insulation to a certain degree still can continue to use.But the shortcoming of this method is to add high frequency AC bias voltage on probe, usually can the disturbance plasma, change original state of plasma, make measure inaccurate.

Summary of the invention

The technical problem to be solved in the present invention provides a kind of rf (discharge) plasma automatic biasing probe diagnostics method, with the plasma diagnostic method that solves above-mentioned floating probe owing to need on probe, add high frequency AC bias voltage and the disturbance plasma, change original state of plasma, make the inaccurate problem of measuring.

Technical solution of the present invention is:

In plasma, place two probes: probe a and probe b, probe a is in quick condition with respect to the plasma discharge loop, and probe b is connected the discharge loop ground wire by capacitance with sample resistance.Do not add direct current or AC bias voltage on the probe.

Voltage alternating component amplitude Δ V between measuring probe a and the probe b, the first harmonic amplitude of probe b electric current | i _{1 ω}| and the second harmonic amplitude | i _{2 ω}|, utilize Δ V, | i _{1 ω}| and | i _{2 ω}| calculate electron temperature T _eWith ion concentration n _i, computing formula is respectively:

|i _1ω|/|i _2ω|＝I ₁(eΔV/T _e)/I ₂(ΔV/T _e)(1)

$n_i=\frac{\left|i_{1\mathrm{\ω}}\right|\sqrt{M_i}}{1.22\mathrm{eA}\sqrt{k{T}_e}}\frac{I_0(\mathrm{e\ΔV}/T_e)}{I_1(\mathrm{e\ΔV}/T_e)}---\left(2\right)$

Above in two formulas, I ₀, I ₁And I ₂Be respectively zeroth order, single order and second order modified Bessel function; E is an electron charge, and unit is a coulomb; A is that detecting probe surface is long-pending, and unit is square metre; M _iBe the quality of ion, unit is a kilogram; K=1.38 * 10 ^-23J/K is a Boltzmann constant; Δ V unit is a volt; | i _{1 ω}| and | i _{2 ω}| unit is an ampere; T _eAnd n _iUnit is respectively Kelvin and every cubic metre.

The invention has the beneficial effects as follows: can overcome the influence that the detecting probe surface insulation is polluted, obtain parameters such as ion concentration and electron temperature.Do not add direct current or AC bias voltage on the probe, article on plasma body discharge disturbance is little.

Description of drawings

Accompanying drawing is a diagnostic method synoptic diagram of the present invention.

Among the figure: 1 probe a, 2 probe b, 3 plasmas, 4 capacitance a, 5 capacitance b,

6 amplifier a, 7 amplifier b, 8 frequency spectrum analysers, 9 discharge loop ground, 10 sample resistances.

Embodiment

Be described in detail specific embodiments of the invention below in conjunction with technical scheme and accompanying drawing.

In Fig. 1,1 probe a and 2 probe b are arranged in 3 plasmas, and 1 probe a is in quick condition with respect to the plasma discharge loop, and 2 probe b are connected 9 discharge loop ground through 5 capacitance b with 10 sample resistances; 1 probe a and 2 probe b are connected the positive-negative input end of 6 amplifier a respectively with 5 capacitances through 4 capacitances, the voltage alternating component between 1 probe a and the 2 probe b through 6 amplifier a amplify and rectifying and wave-filtering after output amplitude Δ V; The electric current of 2 probe b is transformed to voltage signal through 10 sample resistances, delivers to 8 frequency spectrum analysers after 7 amplifier b amplify, output first harmonic amplitude after 8 frequency spectrum analyser analyses | i _{1 ω}| and the second harmonic amplitude | i _{2 ω}|; With output Δ V, | i _{1 ω}| and | i _{2 ω}| data bring formula (1) into and formula (2) calculates electron temperature T respectively _eWith ion concentration n _i

Claims (1)

1. rf (discharge) plasma automatic biasing probe diagnostics method, it is characterized in that: in plasma, place two probes: probe a (1) and probe b (2), probe a (1) is in quick condition with respect to the plasma discharge loop, and probe b (2) is connected discharge loop ground (9) by capacitance (5) with sample resistance (10); Do not add direct current or AC bias voltage on the probe;

Voltage alternating component amplitude Δ V between measuring probe a (1) and the probe b (2), the first harmonic amplitude of probe b (2) electric current | i _{1 ω}| and the second harmonic amplitude | i _{2 ω}|, utilize Δ V, | i _{1 ω}| and | i _{2 ω}| calculate electron temperature T _eWith ion concentration n _i

Computing formula is respectively:

|i _1ω|/|i _2ω|＝I ₁(eΔV/T _e)/I ₂(eΔV/T _e)(1)

$n_i=\frac{\left|i_{1\mathrm{\ω}}\right|\sqrt{M_i}}{1.22\mathrm{eA}\sqrt{k{T}_e}}\frac{I_0(\mathrm{e\ΔV}/T_e)}{I_1(\mathrm{e\ΔV}/T_e)}---\left(2\right)$

Above in two formulas, I ₀, I ₁And I ₂Be respectively zeroth order, single order and second order modified Bessel function; E is an electron charge, and unit is a coulomb; A is that detecting probe surface is long-pending, and unit is square metre; M _iBe the quality of ion, unit is a kilogram; K=1.38 * 10 ^-23J/K is a Boltzmann constant; Δ V unit is a volt; | i _{1 ω}| and | i _{2 ω}| unit is an ampere; T _eAnd n _iUnit is respectively Kelvin and every cubic metre.