CN1361867A - Electron density measurement and control system using plasma-induced changes in the frequency of a microwave oscillator - Google Patents

Abstract

A method and system for measuring at least one of a plasma density and an electron density (e.g., in a range of 10<10> to 10<12> cm<-3>). Measurement of at least one of the plasma density and the electron density enables plasma-assisted processes, such as depositions or etches, to be controlled using a feedback control. Both the measurement method and system generate a control voltage that in turn controls a plasma generator (205) to maintain at least one of the plasma density and the electron density at a pre-selected value.

Description

Use the electron density measurement and the control system of plasma-induced microwave oscillator frequency change

Cross-reference with related application

The present invention relates to name and be called " electron density measurement and Cement Composite Treated by Plasma control system that use locks onto the microwave oscillator of the open resonator that comprises plasma ", the common pending application of agent docket 2312-0709-2YAPROV, " use comprises the electron density and the Cement Composite Treated by Plasma control system of the open resonator variation of resonant frequency of plasma ", the common pending application of agent docket 2312-0710-2YA, these two applications have been applied at the same time.In this this two applications entirely as a reference.

Background of invention

Invention field

The invention provides a kind of method and system, be used in the plasma process system that uses such as semiconductor machining system, measuring electron density.

Background is described

For determining plasma electron density at least by three kinds of known technology based on microwave: (1) microwave interferometry, (2) reflection and the measurement that absorbs, the interference of (3) resonator cavity resonance frequency.Below with each notion of simple term description.

Microwave interferometry relates to determines differing between two microbeams.The first bundle microwave provides contrast signal, and second bundle passes reaction environment and experiences phase shift with respect to the first bundle microwave.From the change calculations refractive index that differs between this two bundle that measures.The interferometry technology is by the L.Goldstein professor's of the Illinois university of Urbana documentary evidence.United States Patent (USP) below: 2,971,153; 3,265,967; 3,388,327; 3,416,077; 3,439,266; 3,474,336; 3,490,037; Described interferometry in 3,509,452 and 3,956,695, each patent at this as a reference.When microbeam passes regional that plasma exists, can directly determine the character of some plasmas according to the absorption of measuring microbeam.At U.S. Patent number 3,599, the signal reflex in the plasma has been described in 089 and 3,383,509.

Used a kind of commercial measurement plasma electron density of measuring the resonator cavity resonance frequency interferences.Because plasma has the effective dielectric constant that depends on plasma electron density, therefore can influence the frequency of each resonant mode in the existence of resonator ionic medium body.This technology has been taught documentary evidence by the S.C.Brown of Massachusetts Institute of Technology (MIT).The part of this technology is described in U.S. Patent number 3,952, and 246 and following non-patent article: Havelag, M., et al, J ApplPhys 70 (7) 3472-80 (1991): use microwave resonance and photodecomposition from effect measurement CF ₄, C ₂F ₆, CHF ₃And C ₃F ₈13.56MHz RF plasma in negative ion density, and Havelag, M., et al, Materials Science Forum, vol.140-142,235-54 (1993): the electronegative particle in fluorocarbon RF etching plasma: the density measure that uses microwave resonance and photic separation effect.

Invention is summed up

It is a kind of than the accurate more plasma measurement system of prior art that one of purpose of the present invention is to provide.

Another object of the present invention is to provide a kind of improvement plasma measurement system that uses plasma-induced microwave oscillator frequency change.

These and other purpose of the present invention is to measure and backfeed loop that the signal of plasma chamber is passed in control is realized by using.Use a computer or digital signal processor (DSP), frequency and the frequency that compares and measures and the required frequency of the signal of plasma chamber passed in the present invention's measurement.According to the difference between frequency of measuring and the required frequency, computing machine/DSP control plasma generator increases or reduces to be fed to the power of plasma chamber, thereby influences plasma electron density.

The accompanying drawing summary

With reference to the following detailed description, when particularly connection with figures is considered, evaluation that the present invention is more complete and attached advantage thereof will become and understand easily, wherein in the accompanying drawings:

Fig. 1 is the block diagram according to plasma electron density measuring system of the present invention;

Fig. 2 is the schematic description of computer system that is used for a part of measuring system of execution graph 1; And

Fig. 3 is the chart of system responses to frequency.

DESCRIPTION OF THE PREFERRED

With reference now to accompanying drawing,, wherein identical reference number is indicated identical or corresponding part in these several views, and Fig. 1 is the block diagram that is used for measuring the plasma electron density measuring system of the plasma that plasma chamber 200 produces according to the present invention.A kind of embodiment of the present invention is used plasma generator 205 and self-excitation microwave oscillator 210, it comprises the closed-loop path, attenuator 213a, arrowband microwave amplifier 215, isolator 220, phase shifter, 225, directional coupler 230, the plasma chamber 200 that comprises open type radiation path, this path also comprises at least one emitter antenna 235, at least one receiver antenna 240, and can comprise one or more reverberators 245.Emitter antenna 235 and receiver antenna 240 can be funnel-shaped aerial, di-lens, or other forms of emitter; And reverberator 245 can have flat or curved surface or can be diffraction grating.

Shown in the embodiment among Fig. 1, transmitter 235, reverberator 245 and receiver 240 can be directed in one way, make open type radiation path be located substantially in the plane on the surface that is parallel to wafer just processed in plasma chamber 200.Yet other embodiment comprises other configuration, is not parallel to the surface of just processed wafer on these configuration middle open type radiation path planes, perhaps open type radiation path even also be not positioned at the plane.And other embodiment also comprises uses a plurality of microbeam paths, in various configurations or identical length or different length.The embodiment of these configurations is including, but not limited to star and triangle.Equally, during the multisystem of the microbeam that intersects when the several position of using in plasma inside, extract spatial information (similar to tomography), rather than be accumulated in the plasma electron density on the microbeam length direction, this point is possible.

If Amplifier Gain is enough high, with the self-excited oscillator that exists on the different frequency.These frequencies satisfy two standards:

1. clean round must surpass 1, and this clean round is amplifier numeral power gain G, the product of the transmission coefficient of all connections and the reflection coefficient of all mirrors. $G\&CenterDot;\{\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{T}_i\&CenterDot;\underset{j=1}{\overset{m}{\mathrm{\&Sigma;}}}{R}_j\}\&GreaterEqual;1---\left(1\right)$ Wherein supposition exists transmission coefficient to connect less than 1 " n ", and path comprises that reflection coefficient is less than " m " reverberator of 1.Although this is the necessary condition of vibration, is not sufficient; Adequacy is provided by second standard.

2. the electromagnetic round drift in the loop of being caused by all reasons must be added to the integral multiple of 2 π radians.This has just guaranteed to set up coherent oscillation from noise.The phase shift relevant with mirror with the most of passive junctions in the loop in fact with frequency-independent, therefore as described below, do not play an important role in its measuring method described here.The electromagnetic phase shift of passing round trip is main, and this is owing to following these three reasons: the propagation in the zone that plasma forms; Propagation in the element in waveguide and waveguide; With propagation (and amplification) by amplifier.Therefore adequate condition can be write as: $[\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{\mathrm{\&phi;}}_i+\underset{j=1}{\overset{m}{\mathrm{\&Sigma;}}}{\mathrm{\&phi;}}_j]+{\mathrm{\&phi;}}_{\mathrm{amp}}\left({\mathrm{\&omega;}}^{\&prime;}\right)+\mathrm{\&beta;}\left({\mathrm{\&omega;}}^{\&prime;}\right)d_{\mathrm{ckt}}+\frac{{\mathrm{\&omega;}}^{\&prime;}}{c}\underset{0}{\overset{d_p}{\&Integral;}}{n}_p({\mathrm{\&omega;}}^{\&prime;},z)\mathrm{dz}=q\&CenterDot;2\mathrm{\&pi;}---\left(2\right)$

Wherein first bracket representative is from the phase shift of any connection (i) or mirror (m); φ _Amp(ω ') is the phase shift of amplifier; β (ω ') d _CktFor passing the connection waveguide, attenuator, the phase shift of the phase shifter and the microwave of other passive elements propagation that comprise circuit; Last is the phase shift of passing the microwave in the zone that comprises plasma for the equation left side.Item n _p(ω ', z) be the refractive index of plasma, ω ' is for having from z=0 to z=d _pThe angular frequency of the microwave the when plasma of filling arm exists is assumed to d in inner treatment chamber electromagnetism length _p, the length of all the other connecting circuit is d _CktAnd supposition unguided microwave in the plasma zone can be had a uniform plane wave of the phase constant that is provided by ω ' n/c approximate.

The chart that figure 3 illustrates (1) and (2) result shows (function as ω draws), wherein G ₀(ω) be the small-signal gain of amplifier, S is to withstand that part of electromagnetic power of round trip and is the abbreviation of braces in (1); Clear in order to draw, ignore the bracket in (2) and the phase shift of amplifier; β (ω) is approximate by the phase constant ω of uniform plane wave/c.In order to draw, if neglect the frequency dependence of plasma refraction rate, (2) left side becomes straight line, has diagonal frequencies and is [d _Ckt+ n _pd _pThe slope of]/C.The requirement of noticing (1) is that the restriction vibration becomes G ₀The part of 〉=1 amplifier band width, and can be by increasing the decay in the backfeed loop reduces S value and increase 1/S value and reduces this part.

The straight line of representative (2) with by the vertical empty horizontal joining that separates of 2 π for satisfying the angular frequency of (2), if they also satisfied (1) just become oscillation frequency.The outstanding solid arrow of those conducts of satisfying really illustrates.Flow gain excessively on each amplitude and this frequency (is G ₀(ω) S-1) is directly proportional.If compare with the bandwidth of possible vibration, free spectral range (promptly (2) are adjacent separate between interval) is little, and the vibration at the frequency multiplication place is possible and/or likely so.

Turn back to the description of Fig. 1, Fig. 1 also shows the frequency meter 250a between the output that is connected directional coupler 230 and frequency mixer 255 inputs.A frequency stabilization local oscillator 260 is connected to second input of frequency mixer 255 by attenuator 213b.Select the frequency of frequency stabilization local oscillator 260, perhaps a shade below or be higher than the passband of narrow-band amplifier 215 a little.(attenuator 213b also is connected to check and stablizes on the second frequency meter 250b of local oscillator 260 frequencies).In order to simplify description subsequently, suppose that the frequency configuration of frequency stabilization local oscillator 260 is the passband a shade below narrow-band amplifier 215.The frequency of the IF signal that occurs from frequency mixer 255 is the difference between the frequency of the frequency of frequency stabilization local oscillator 260 and self-excited oscillator 210.According to the embodiment of describing, the frequency typical case of IF signal is in 0 in the scope of about 2GHz.Certainly, other the frequency range of amplifier parameter for other also is possible.

Fig. 2 is that the signal of computer system 100 is described, and this system is used for measuring and controlling the plasma that is produced at plasma chamber 200 by plasma generator 205.Computing machine 100 is carried out method of the present invention, wherein in the counter body 102 mainboard 104 is housed, it comprises CPU106, storer 108 (for example, DRAM, ROM, EPROM, EEPROM, SRAM and FlashRAM), with other specific purposes logical device (for example ASIC) or configurable logic device (for example, GAL and Reprogrammable FPGA) arbitrarily.Computing machine 100 also comprises a plurality of entering apparatus (for example keyboard 122 and mouse 124) and is used to control the video card 110 of display 120.In addition, computer system 100 also comprises floppy disk 114; Other removable medium devices (for example CD 119, tape and removable magnet-optical medium (not shown)); With hard disk 112, or other fixing high-density medium drivers, use suitable device bus (for example SCSI bus strengthens the IDE bus, or super dma bus) to connect.Computing machine 100 can comprise CD-ROM drive 118 in addition, disc read/write unit (not shown) or CD player (not shown), and be connected to identical device bus or another device bus.Although CD 119 illustrates with the CD box, CD 119 can directly be inserted in the CD-ROM drive that does not need box.In addition, the printer (not shown) also provides the printing tabulation of the plasma density under different time and the situation.

As mentioned above, this system comprises a computer-readable medium at least.The example of computer-readable medium is a CD 119, hard disk 112, floppy disk, tape, magneto-optic disk, PROM (EPROM, EEPROM, Flash EPROM), DRAM, SRAM etc.The present invention includes the hardware that is used for control computer 100 and be used to make computing machine 100 can with the interactional software of user, be stored on any one computer-readable medium or its assembly.Described software can include but are not limited to: device driver, and operating system and user use, such as developing instrument.Described computer-readable medium also comprises the computer program of the present invention that is used for monitoring and controlling the plasma of plasma chamber.Computer code equipment of the present invention can be any compiling or executable coding mechanism, including, but not limited to SCRIPT, and interpreter, dynamic link library, java class and complete executable program.

As shown in Figure 1, the IF signal frequency is received and simulated numeral (A/D) converter 150b by the FV convertor in the computing machine 100 152 and converts digital signal to.(in another embodiment, FV convertor 152 and A/D converter 150b are counted the digital counter replacement of IF cycle index.) computing machine 100 also receive by the equipment operator provide by the input data 275 of second A/D converter 150a conversion.In another embodiment, input data 275 directly are received (for example by keyboard 122) with digital form, and the second A/D converter 150A is optional in this embodiment.DSP or CPU106 receive and comparative figures IF signal is transferred on digital simulation (D/A) converter 160 with input data 275 and with digital output signal, this converter is followed transmission of analogue signal to plasma generator 205, to revise the output power of plasma generator 205 where necessary.In another embodiment, D/A converter 160 be integrated into improved plasma generator 205 ' in, and the numeral of DSP/CPU106 output be applied directly to improved plasma generator 205 ' on.

The frequency of the self-excited oscillator shown in Fig. 1 depends on the plasma electron density of the path of the circuit in the process chamber, so the skew in its operating frequency can be used to control plasma generator.Derive the relation between the space average electron density of frequency shift (FS) and plasma below.

If plasma electron density is zero, n _p(ω, z)=1, so equation (2) becomes: $[\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{\mathrm{\&phi;}}_i+\underset{j=1}{\overset{m}{\mathrm{\&Sigma;}}}{\mathrm{\&phi;}}_j]+{\mathrm{\&phi;}}_{\mathrm{amp}}\left(\mathrm{\&omega;}\right)+\mathrm{\&beta;}\left(\mathrm{\&omega;}\right)d_{\mathrm{ckt}}+\frac{\mathrm{\&omega;}}{c}\underset{0}{\overset{{\mathrm{<figure-callout\; id="1"\; label="d\; p"\; filenames="A0081056300151.png,A0081056300161.png"\; state="\{\{state\}\}">d</figure-callout>}}_p}{\&Integral;}}1\mathrm{dz}=q\&CenterDot;2\mathrm{\&pi;}---\left(3\right)$ Recognize that wherein refractive index in the process chamber is along from z=0 to z=d _pPath turn back to its vacuum values (n=1).As a result, frequency restoration is to ω rather than ω ', wherein owing to there is not frequency shift (FS) ω '=ω+Δ ω=ω+0.Identical measures on the right of present equation (2) and (3), and therefore the left side of (2) and (3) can equate.Therefore first bracket in equation (2) and (3) is left out, and residual term can be by following grouping: $\frac{{\mathrm{\&omega;d}}_p}{c}\&CenterDot;\frac{1}{d_p}\underset{0}{\overset{d_p}{\&Integral;}}[1-n_p(\mathrm{\&omega;},z)]\mathrm{dz}=[{\mathrm{\&phi;}}_{\mathrm{amp}}\left({\mathrm{\&omega;}}^{\&prime;}\right)-{\mathrm{\&phi;}}_{\mathrm{amp}}\left(\mathrm{\&omega;}\right)]+[\mathrm{\&beta;}\left({\mathrm{\&omega;}}^{\&prime;}\right)d_{\mathrm{ckt}}-\mathrm{\&beta;}\left(\mathrm{\&omega;}\right)d_{\mathrm{ckt}}]---\left(4\right)$ Wherein for the item that multiply by in integration and the plasma refraction rate expression formula, the difference between ω ' and the ω is left in the basket.

Because $\frac{{\mathrm{\&omega;}}_p^2}{{\mathrm{\&omega;}}^2}<<1,n_p\left(\mathrm{\&omega;}\right)\&ap;\sqrt{1-\frac{{\mathrm{\&omega;}}_p^2}{{\mathrm{\&omega;}}^2}}\&ap;1-\frac{1}{2}\&CenterDot;\frac{{\mathrm{\&omega;}}_p^2}{{\mathrm{\&omega;}}^2}---\left(5\right)$ And (unit is m to the Ne=electron density ^-3).According in the value of ω and the skew of frequency Δ ω, Φ amp that utilizes Taylor series expansion to ask to locate and the value of β at ω '. ${\mathrm{\&phi;}}_{\mathrm{amp}}\left({\mathrm{\&omega;}}^{\&prime;}\right)={\mathrm{\&phi;}}_{\mathrm{amp}}\left(\mathrm{\&omega;}\right)+\frac{{\&PartialD;\mathrm{\&phi;}}_{\mathrm{amp}}\left(\mathrm{\&omega;}\right)}{\&PartialD;\mathrm{\&omega;}}\&CenterDot;\mathrm{\&Delta;\&omega;}---\left(7a\right)$ $\mathrm{\&beta;}\left({\mathrm{\&omega;}}^{\&prime;}\right)=\mathrm{\&beta;}\left(\mathrm{\&omega;}\right)+\frac{\&PartialD;\mathrm{\&beta;}\left(\mathrm{\&omega;}\right)}{\&PartialD;\mathrm{\&omega;}}\&CenterDot;\mathrm{\&Delta;\&omega;}---\left(7b\right)$ The item that relates to Φ amp partial derivative is the group delay Tg that is exaggerated device and inserts and very little usually; The item that relates to the partial derivative of β is the inverse of group velocity Vg (wherein Vg is less than c).Therefore equation (4) can be approximately: $\frac{e^2}{{\mathrm{m\&epsiv;}}_0}\&CenterDot;\left[\frac{1}{d_p}\underset{0}{\overset{d_p}{\&Integral;}}{N}_e\left(z\right)\mathrm{dz}\right]=\frac{<N_e>e^2}{{\mathrm{m\&epsiv;}}_0}=2\&CenterDot;\mathrm{\&Delta;\&omega;}\&CenterDot;\mathrm{\&omega;}\&CenterDot;\{\frac{c}{v_g}\&CenterDot;\frac{d_{\mathrm{ckt}}}{d_p}+\frac{{\mathrm{cT}}_g}{d_p}\}---\left(8\right)$

Equation (8) shows space average electron density and frequency shift (FS) Δ ω, the nominal frequency ω of vibration, basic constant c, m and ε ₀, relevant with the amount in the bracket that only need determine once (8).

Available common wavemeter is measured oscillation frequency ω, reaches to be higher than 1% degree of accuracy; Basic constant is accurately known; And by with under the various air pressure such as SF ₆, the heavy gas filling vias dp of argon gas and xenon and estimation frequency shifted by delta ω can test the value of determining braces.(for above-mentioned calibration procedure, local oscillator (LO) should be higher than controlled oscillator on frequency.) use heterodyne technology can measure the bigger precision of the latter, wherein frequencies omega ' with at ω _LOUnder stable local oscillator mix, make usable frequency counter and other known frequencies determine commercial measurement difference ω '-ω _LO

The average electron density that uses equation (8) then is applied to the voltage of the plasma generator 205 that connects plasma chamber 200 as FEEDBACK CONTROL with control.

According to the present invention, a kind of example that obtains the method for the average electron density approximate value between transmitter 235 and the receiver 245 may further comprise the steps:

1. open measurement mechanism and after plasma is initial, make it reach steady state (SS).

2. import the value of the item in equation (8) braces.Notice that this value depends on the setting of the adjustable element (for example, attenuator 213a and phase shifter 225) in the backfeed loop; Therefore determining that these settings of back should not change.In another embodiment, construct a plurality of values (each possible combination that value is provided with corresponding to environment), and be arranged on the suitable value of selection in the operating process according to environment for the item in the braces in the equation (8).

3. the frequency of checking frequency stabilization local oscillator 260 is also adjusted when needed.

4. with keyboard 122 or with the required plasma electron density of another data-in port input.

5. from initial this method of data-in port.

On the basis of difference between the IF signal of required IF signal and measurement, adjust the output of plasma generator 205, the required IF signal with measuring is more closely mated.For example, if the IF signal of measuring greater than required IF signal, is exported increment of RF power reduction.Similarly, if, exporting RF power less than required IF signal, the IF signal of measuring increases an increment.And for coarse adjustment, the predetermined relationship between plasma electron density and the RF power can be used for the approximate RF power that will be applied in.Then, apply fine tuning more accurately to control plasma system.

In an embodiment of fine tuning method, on the basis of the size of given increment, adjust the RF power that applies (promptly increase or reduce a given increment) and can not more closely mate up to the signal of measuring with required.Reduce given increment (for example reducing half) then, and it is thick too up to new given increment to continue fine tuning.Yet, if the difference that the difference between that measure and the required signal becomes and can mate greater than by current intervals increases current intervals so.

In another embodiment of method of adjustment, other information is used to fine tuning feedback/control procedure.The signal that described information can include but are not limited to: every RF variable power changes (i.e. first derivative), flection and integration.The present invention is a general controls mechanism, is not limited by the feedback mechanism of the type of information and selection.

The comparison of the precision and the prior art of the inventive method is described hereinafter.Suppose that backfeed loop can be divided into two parts that physical length L equates.First represents open type radiation path, and second portion is represented the remainder of backfeed loop.When lacking plasma, frequency is f, and the wavelength in the open type radiation path is λ ₂Wavelength in the remainder of backfeed loop is λ ₁, and the length of the backfeed loop in wavelength is q.For the sake of simplicity, the phase velocity of supposing the signal in the whole backfeed loop is c.(clearly the phase velocity in the waveguide still neglects complicated factor here greater than c.Thereby) draw by these hypothesis

L/ λ ₁+ L/ λ ₂≈ Lf ₁/ c+Lf ₂/ c ≈ q (9) is when plasma occurs, and frequency becomes f2, and the mean refractive index in open type radiation path becomes＜n〉and the total length of feedback network in wavelength keeps q.Therefore,

Lf ₂/ c+＜n〉Lf ₂/ c ≈ q (10) merges equation (9) and (10) and obtains: $\frac{1-<n>}{1+<n>}\&ap;\frac{f_2-f_1}{f_1}---\left(11\right)$ Frequency-splitting f ₂-f ₁Corresponding to above-mentioned IF frequency.By calculating the differential of natural logarithm, obtain following equation (15): $\mathrm{\&delta;}\ln \left(\frac{1-<n>}{1+<n>}\right)=\mathrm{\&delta;}\ln \left(\frac{f_2-f_1}{f_1}\right)---\left(12\right)$ $\frac{\mathrm{\&delta;}\left(\frac{1-<n>}{1+<n>}\right)}{\left(\frac{1-<n>}{1+<n>}\right)}\&ap;\frac{\mathrm{\&delta;}\left(\frac{f_2-f_1}{f_1}\right)}{\left(\frac{f_2-f_1}{f_1}\right)}\&ap;\frac{\mathrm{\&delta;}\left(\frac{\mathrm{IF}}{f_1}\right)}{\left(\frac{\mathrm{IF}}{f_1}\right)}---\left(13\right)$ IF=f here ₂-f ₁Be the IF signal frequency.For fixing f1, and utilize approximate

1+＜n〉it is very goodly approximate for the situation in this care for ≈ 2 (14), can draw: $\frac{\mathrm{\&delta;}(1-<n>)}{1-<n>}|\&le;|\frac{\mathrm{\&delta;IF}}{\mathrm{IF}}|+|\frac{\mathrm{\&delta;}{f}_1}{{\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="A0081056300151.png,A0081056300161.png"\; state="\{\{state\}\}">f</figure-callout>}}_1}|---\left(15\right)$ The reasonable expectation value of measuring accuracy causes the estimation on every about 0.0025 on the right of top equation (15).Therefore, $\left|\frac{\mathrm{\&delta;}(1-<n>)}{1-<n>}\right|\&ap;0.005---\left(16\right)$ Suppose: $n\&ap;1-\frac{e^2}{8{\mathrm{\&pi;}}^2{\mathrm{\&epsiv;}}_0{\mathrm{mf}}^2}N---\left(17\right)$ Thereby draw: $\frac{\mathrm{\&delta;}(1-<n>)}{1-<n>}\&ap;0.005\&ap;\frac{\mathrm{\&delta;}<n>}{<n>}---\left(18\right)$ And about 0.5% magnitude of expected accuracy.

Significantly, according to above-mentioned instruction, various modifications and variations of the present invention are possible.Therefore be to be understood that in the scope of additional claims, can according to implement the present invention in this special different mode of describing.

Claims (24)

1. a system is used at plasma source, measures at least a in plasma density and the electron density at least one in plasma chamber and the electron source, and this system comprises:

First sensor is used for measuring and passes plasma source, first signal of at least one in plasma chamber and the electron source;

Second sensor is used to measure the secondary signal from reference source; And

Comparer is used for difference between comparison first and second signals determining plasma source, at least a in plasma chamber and the electron source in plasma density of at least one and the electron density.

2. system as claimed in claim 1, plasma source wherein, at least a in plasma chamber and the electron source in plasma density of at least one and the electron density 10 ¹⁰To 10 ¹²Cm ^-3Scope in.

3. system as claimed in claim 1 also comprises being used to keep plasma source, the self-excitation microwave oscillator of at least one in plasma chamber and the electron source.

4. system as claimed in claim 1, wherein first sensor comprises the closed-loop path, this loop comprises the open type radiation path that is used to transmit first signal.

5. system as claimed in claim 4, its middle open type radiation path comprises plasma.

6. system as claimed in claim 4, wherein the closed-loop path also is included in the arrowband microwave amplifier in the open type radiation path.

7. system as claimed in claim 3 also comprises:

Stablize local oscillator; And

Frequency mixer, wherein the second frequency of the first frequency of self-excited oscillator and stable local oscillator mixes to produce the IF signal.

8. system as claimed in claim 1 also comprises by the equipment operator and imports at least a data input device in required plasma density and the required electron density.

9. system as claimed in claim 8, wherein data input device comprises keyboard.

10. system as claimed in claim 1, wherein comparer comprises digital signal processor.

11. system as claimed in claim 1 also comprises being used for measuring and passes plasma source, the 3rd sensor of the 3rd signal of at least one in plasma chamber and the electron source.

12. system as claimed in claim 1 also comprises being used for measuring and passes plasma source, the 3rd sensor of the 3rd signal of at least one in plasma chamber and the electron source wherein first passes different length with the 3rd signal.

13. system as claimed in claim 1, also comprise being used for measuring and pass plasma source, third and fourth sensor of third and fourth signal of at least one in plasma chamber and the electron source, wherein the path of the path of third and fourth signal and first signal intersects.

14. a method is used to measure plasma source, at least a in plasma density at least one in plasma chamber and the electron source and the electron density, and this method may further comprise the steps:

Plasma source is passed in measurement, first signal of at least one in plasma chamber and the electron source;

Measurement is from the secondary signal of reference source; And

Relatively the difference between first and second signals to be determining plasma source, at least a in plasma density of at least one in plasma chamber and the electron source and the electron density.

15. as the method for claim 14, the step of wherein measuring first signal comprises that density measurement is 10 ¹⁰To 10 ¹²Cm ^-3Scope in plasma source, at least a in plasma density of at least one of plasma chamber and electron source and the electron density.

16., comprise that also the control signal that applies from the self-excitation microwave oscillator keeps plasma source, the step of at least one in plasma chamber and the electron source as the method for claim 14.

17. as the method for claim 14, the step of wherein measuring first signal comprises uses the closed-loop path to measure first signal, this closed-loop path comprises the open type radiation path that transmits first signal.

18., also comprise the step of plasma as open type radiation path is provided as the method for claim 17.

19. as the method for claim 17, the step of wherein measuring first signal comprises uses the closed-loop path to measure first signal, this closed-loop path comprises the arrowband microwave amplifier in the open type radiation path.

20., also comprise step as the method for claim 16:

The first frequency of mixing self-excited oscillator and the second frequency of stable local oscillator are to produce the IF signal.

21., also comprise by the equipment operator and import at least a step in required plasma density and the required electron density as the method for claim 14.

22., also be included at least a step in required plasma density of input on the keyboard and the required electron density as the method for claim 14.

23. as the method for claim 14, the step that wherein compares comprises utilizes relatively difference of digital signal processor.

24. method as claim 14, also comprise control signal is applied to plasma source, on in plasma chamber and the electron source at least one, to revise plasma source, at least a step in plasma density of at least one in plasma chamber and the electron source and the electron density.

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