CN106413237A - Plasma diagnostic method of multi-amplitude AC bias probe based on data acquisition card - Google Patents

Abstract

The invention belongs to the technical field of plasma, and discloses a plasma diagnostic method of a multi-amplitude AC bias probe based on a data acquisition card. The plasma diagnostic method comprises the steps of: generating AC bias signals based on the data acquisition card, driving the signals via a power amplifier, and applying the signals to a probe in plasma through a sampling resistor, meanwhile, acquiring a voltage signal on the sampling resistor by means of a differential simulation input port of the data acquisition card commanded by a computer, sending the voltage signal to the computer, and converting the voltage signal into a current signal by the computer; and carrying out spectral analysis and least square method fitting, and further calculating to obtain an accurate electronic temperature value and an accurate ion density value. The plasma diagnostic method solves the problem that electronic temperature and ion density measured by adopting the existing fixed-amplitude AC bias probe diagnostic technique are inaccurate, can diagnose the plasma especially insulating deposition environment plasma, can automatically complete the plasma diagnosis process, and output the accurate electronic temperature and ion density values.

Description

A kind of many amplitude AC bias probe plasma diagnostics based on data collecting card Method

Technical field

The invention belongs to technical field of plasma, it is related to a kind of many amplitude AC biasing spies based on data collecting card Pin plasma diagnostic method, for diagnosing plasma, particularly insulate depositional environment plasma, obtain electron temperature and Ion concentration.

Background technology

Existing probe technique is used for diagnosing plasma parameter, has polytype.The most frequently used Single probe is one Little metal electrode is that probe is placed in plasma, adds scanning bias voltage between probe and plasma ground electrode, Then measurement probe current, with the change of scanning bias voltage, obtains VA characteristic curve, then by analyzing VA characteristic curve Obtain the parameter of plasma.In addition also have double types such as probe, three probes, a something in common of these probe techniques It is to be required on probe plus DC offset voltage, and the problem that this is brought is：When having in the plasma environment being diagnosed When insulation deposition occurs, detecting probe surface can deposited material cover, thus losing electric conductivity and cannot working.

The prior art that solves the above problems is to produce a fixed amplitude V with signal generator₀AC bias electricity Pressure is added on probe, measures probe current signal, then using spectrum analyzer, probe current signal is analyzed, obtains First harmonic amplitude i_1ωWith second-harmonic amplitude i_2ω, then use formula i_1ω/i_2ω=I₁(eV₀/T*)/I₂(eV₀/ T*) calculate T* is as electron temperature, then uses formulaCalculate n* as ion concentration, on In the formula of face two, e is electron charge, I₀(eV₀/T*)、I₁(eV₀/ T*) and I₂(eV₀/ T*) it is eV respectively₀The zeroth order of/T*, single order With second order Bessel function of imaginary argument, A and M is that detecting probe surface amasss and mass of ion respectively.Because alternating current can be with displacement The form of electric current passes through the insulating barrier of detecting probe surface, even if this technology is in the case that detecting probe surface is covered by megohmite insulant Can be using it is thus possible to the plasma of diagnosing insulation depositional environment.

But T* and n* that above-mentioned prior art obtains not is accurate electron temperature and ion concentration.This is because on Its theoretical foundation of diagnostic techniquess stating existing fixed amplitude AC bias probe is infinity plane electrode model it is assumed that electric current Signal amplitude is unrelated with the amplitude of AC bias potential, and actually used probe is all very little it is impossible to regard infinitely great as Plane electrode, current signal amplitude is relevant with the amplitude of AC bias potential.This makes the electricity obtaining using prior art Sub- temperature and ion concentration numerical value change with the change of selected AC bias potential amplitude, and existing fixed amplitude exchange is partially The diagnostic techniquess putting probe can not accurately obtain electron temperature value and the density value of plasma.

On the other hand, the diagnostic techniquess of existing fixed amplitude AC bias probe utilize signal generator and spectrum analyses Instrument is it is impossible to be automatically performed plasma diagnostics process, output result.

Content of the invention

The present invention provides a kind of many amplitude AC bias probe plasma diagnostic method based on data collecting card, to solve The certainly diagnostic techniquess measurement electron temperature of existing fixed amplitude AC bias probe and the inaccurate problem of ion concentration, and energy Enough it is automatically performed plasma diagnostics process, export accurate electron temperature value and density value.

The technical scheme is that：

A the simulation output port of () computer instruction data collecting card gradually produces amplitude and is respectively V=V_j(j=1, 2 ...) AC bias signal, drive through power amplifier, then be added in, through sample resistance, the probe being placed in plasma On, meanwhile, the voltage signal that the difference analogue input port of computer instruction data collecting card gathers on sample resistance sends into meter Calculation machine, and current signal is converted into by computer.

B () computer is to each amplitude AC bias voltage V=V_jProbe current signal under (j=1,2 ...) is carried out Spectrum analyses, obtain first harmonic amplitude i_1ωj(j=1,2 ...) and second-harmonic amplitude i_2ωj(j=1,2 ...) and calculate Go out their ratio P_j=i_1ωj/i_2ωj(j=1,2 ...).

C () computer is to data point (P_j,V_j) (j=1,2 ...) in order to T for variable function I₁(eV_j/T)/I₂(eV_j/ T (wherein e is electron charge, I) to carry out least square fitting₁(eV_j/ T) and I₂(eV_j/ T) it is eV respectively_jThe single order of/T and two Rank Bessel function of imaginary argument), output meets the T value T=T of least square fitting_e, T_eIt is accurate electron temperature value.

D () computer utilizes V_j(j=1,2 ...), i_1ωj(j=1,2 ...) and T_eData substitutes into formulaIt is calculated n_j(j=1,2 ...), in formula, A and M is that detecting probe surface amasss respectively And mass of ion, I₀(eV_j/T_e) it is eV_j/T_eZeroth order Bessel function of imaginary argument, then to data point (n_j,V_j) (j=1, 2 ...) carry out Linear Quasi merging continuation to V=0, export value n in V=0 for the fitting a straight line₀, n₀It is accurate ion concentration Value.

The invention has the beneficial effects as follows：

Plasma can be diagnosed particularly insulate depositional environment plasma, be automatically performed plasma diagnostics process, Export accurate electron temperature value and density value.

Brief description

Fig. 1 is the schematic diagram diagnosing plasma using the inventive method.

Fig. 2 is the data point (P being obtained using the inventive method_j,V_j) (j=1,2 ...) and use function I₁(eV_j/T)/I₂ (eV_j/ T) it is carried out with the result of least square fitting, and the data point (n being obtained using the inventive method_j,V_j) (j= 1,2 ...) and it is carried out with Linear Quasi merging continuation to the result of V=0.

In figure：1 probe；2 argon plasmas；3 computers；4 director data capture cards；5 simulation output ports；6 power are put Big device；7 sample resistances；8 difference analogue input ports.

Specific embodiment

Describe the specific embodiment of the present invention with reference to technical scheme and accompanying drawing in detail.

In FIG, probe 1 be an area be 0.15cm²Tinsel, be placed in argon plasma 2.Computer 3 refers to The simulation output port 5 making data collecting card 4 gradually produces amplitude and is respectively V=V_jThe AC bias letter of (j=1,2 ...) Number, drive through power amplifier 6, then be added on the probe 1 being placed in plasma 2 through sample resistance 7, meanwhile, computer 3 The voltage signal that the difference analogue input port 8 of director data capture card 4 gathers on sample resistance 7 sends into computer 3, by calculating Machine 3 is converted into current signal.

In Fig. 2, P_j=i_1ωj/i_2ωj(j=1,2 ...) it is computer 3 to each amplitude AC bias voltage V=V_j(j= 1,2 ...) under probe current signal carry out the first harmonic amplitude i that spectrum analyses obtain_1ωj(j=1,2 ...) and secondary humorous Wave-amplitude i_2ωjThe ratio of (j=1,2 ...).Each P_jWith corresponding V_jConstitute data point (P_j,V_j) (j=1,2 ...) use labelling "○" represents in figure.

Computer 3 is to data point (P_j,V_j) (j=1,2 ...) in order to T for variable function I₁(eV_j/T)/I₂(eV_j/T) (wherein e is electron charge, I to carry out least square fitting₁(eV_j/ T) and I₂(eV_j/ T) it is eV respectively_jThe single order of/T and second order Bessel function of imaginary argument).Function I as T=2.35eV₁(eV_j/T)/I₂(eV_j/ T) (solid-line curve in Fig. 2) meet right Data point (P_j,V_j) (j=1,2 ...) least square fitting, export T_e=2.35eV is accurate electron temperature value.

In fig. 2, n_j(j=1,2 ...) it is that computer utilizes V_j(j=1,2 ...), i_1ωj(j=1,2 ...) data And T_e=2.35eV substitutes into formulaResult (the A=0.15cm in formula calculating²It is Detecting probe surface amasss and M=6.68 × 10^-26Kg is argon ion quality).Each n_jWith corresponding V_jConstitute data point (n_j,V_j) (j=1, 2 ...) represented in figure with labelling " Δ ".

Computer is to data point (n_j,V_j) (j=1,2 ...) (in Fig. 2, void is straight to V=0 to carry out Linear Quasi merging continuation Line), fitting a straight line is in value n of V=0₀=9.1 × 10⁹cm^-3, export n₀=9.1 × 10⁹cm^-3For accurate density value.

Claims (1)

1. a kind of many amplitude AC bias probe plasma diagnostic method based on data collecting card is it is characterised in that include Following steps：

A the simulation output port of the data collecting card of () computer instruction gradually produces amplitude and is respectively V=V_j(j=1,2 ...) AC bias signal, drive through power amplifier, then be added on the probe being placed in plasma through sample resistance, with When, the voltage signal that the difference analogue input port of the data collecting card of computer instruction gathers on sample resistance sends into calculating Machine, and current signal is converted into by computer；

B () computer is to each amplitude AC bias voltage V=V_jProbe current signal under (j=1,2 ...) carries out frequency spectrum and divides Analysis, obtains first harmonic amplitude i_1ωj(j=1,2 ...) and second-harmonic amplitude i_2ωj(j=1,2 ...) and calculate the two Ratio P_j=i_1ωj/i_2ωj(j=1,2 ...)；

C () computer is to data point (P_j,V_j) (j=1,2 ...) in order to T for variable function I₁(eV_j/T)/I₂(eV_j/ T) enter Row least square fitting, wherein e are electron charges, I₁(eV_j/ T) and I₂(eV_j/ T) it is eV respectively_jThe single order of/T and second order are empty Argument Bessel function, output meets the T value T=T of least square fitting_e, T_eIt is accurate electron temperature value；

D () computer utilizes V_j(j=1,2 ...), i_1ωj(j=1,2 ...) and T_eData substitutes into formulaIt is calculated n_j(j=1,2 ...), in formula, A and M is that detecting probe surface amasss respectively And mass of ion, I₀(eV_j/T_e) it is eV_j/T_eZeroth order Bessel function of imaginary argument, then to data point (n_j,V_j) (j=1, 2 ...) carry out Linear Quasi merging continuation to V=0, export value n in V=0 for the fitting a straight line₀, n₀It is accurate ion concentration Value.