CN101221894B - Phase demodulation apparatus and method for sensor of radio frequency adaptation - Google Patents

Abstract

The invention relates to a phase discrimination device for a sensor of a radio frequency adapter and a method for using the same, which is applied on a sensor of a radio frequency adapter and is used to detect the phase of radio frequency load impedance via radio frequency transmission wire. The device comprises a signal processing and sampling circuit, a single shot trigger and a filter circuit, wherein the single shot trigger does not have stricter requirements for signal input, which requires neither two input signals of equal amplitude nor symmetrical input square waves necessarily; therefore, the system is easy to realize. Although the system is not complicated, the device can also well detect the phase of the load impedance.

Description

A kind of phase demodulation apparatus of transducer of radio frequency adaptation and method

Technical field

The present invention relates to the detection and the monitoring technique field of semiconductor manufacturing facility, relate in particular to a kind of phase demodulation apparatus and method of transducer of radio frequency adaptation.

Background technology

Plasma is widely used in the production of semiconductor device.In plasma etching system, radio-frequency power supply is powered to produce plasma to plasma chamber.The atom, molecule and the free radical isoreactivity particle that contain a large amount of electronics, ion, excitation state in the plasma, these active particles interact with the semiconductor crystal wafer that places cavity and expose to the open air under plasma environment, make the semiconductive material wafer surface that various physics and chemical reaction take place, thereby the material surface performance is changed, finish the etching process of semiconductor crystal wafer.

Radio-frequency power supply operating frequency commonly used is 13.56MHz, and output impedance is 50 Ω, is that the coaxial cable of 50 Ω links to each other with reaction chamber by characteristic impedance.Along with the carrying out of etching process, gas componant in the chamber and pressure is all in continuous variation, therefore, as the isoionic impedance of load also in continuous variation.And the internal resistance of radio-frequency power supply is 50 fixing Ω, and promptly impedance is unmatched between power source and the load, so just causes having bigger reflection power on the radio frequency transmission line, and radio frequency power output can't all be applied to plasma chamber.If the RF energy shortage that obtains is so that plasma glow start, etching process just can't be carried out, and power is understood the reflected back power supply, when reaching 20% left and right sides of power output, will damage the RF power supply.

Thus, the block diagram of whole radio-frequency (RF) transmission system as shown in Figure 1 inserts a matching network between general RF power source and the plasma chamber, makes load impedance and source impedance can reach conjugate impedance match.Because along with the carrying out of etching process, the value of load impedance is constantly to change, need to introduce a modulus of impedance value, phase detectors, i.e. transducer (Sensor).By the voltage on the sense transmission line, current signal, utilize certain amplitude discrimination and phase detecting method, just can obtain the mould value and the phase place of load impedance.The automatic impedance controller is according to the output of transducer, the rotation of control step motor, thus adjust variable element in the matching network, the total impedance that finally makes matching network and plasma cavity is 50 Ω, realizes mating.

For method according to the phase place of the voltage and current calculated signals load impedance on the transmission line, conventional a kind of method as shown in Figure 2, adopt analog multiplier, if the phase difference of input signal and reference signal is φ, then the output of analog multiplier is directly proportional with COS φ, therefore can use the multiplier phase demodulation.The output of φ＜0 o'clock and φ＞0 are o'clock identical, phase discriminator can not differential phase leading with lag behind, it is operated in pi/2 ± pi/2 scope, near φ=pi/2, the phase discriminator linearity is best, sensitivity is the highest.Influencing accuracy factors has the amplitude of input signal, output non-linear etc.

As shown in Figure 2 the output of analog multiplier equal K doubly * take advantage of y.

According to triangle formula abbreviation: Uo=(1/2) * K * Usm * Ucm * COS φ

In the formula: Uo is the output signal of analog multiplier phase discriminator;

K is constant coefficient;

Usm, one of input signal;

Ucm, another road input signal.

Be analog multiplier exported one with signal between the relevant amount of phase difference, finished phase discrimination function

The shortcoming that this method exists is, output signal is the cosine function of phase place, is non-linear, and signal amplitude influence identified result, so can't obtain result accurately.

The method of conventional another kind of phase demodulation is to adopt a door phase discriminator as shown in Figure 3 and Figure 4, and wherein the most frequently used be the XOR gate phase demodulation, it is made up of XOR gate and low pass filter.It is as shown in table 1 that the circuit symbol of XOR gate reaches truth table as shown in Figure 3, output waveform and phase characteristic such as Fig. 5, Fig. 6 and shown in Figure 7.

Table 1

V1	V2	V3
			0	0	0
0	1	1
			1	0	1
1	1	0

Output voltage waveforms V ₃Through the average voltage behind the low pass filter be

${\mathrm{\&upsi;}}_d=\left\{\begin{array}{cc}\frac{V_{\mathrm{dm}}}{\mathrm{\&pi;}}{\mathrm{\&phi;}}_{\mathrm{<figure-callout\; id="0"\; label="e"\; filenames="S07163392620070406E000022.png,S07163392620070406E000033.png"\; state="\{\{state\}\}">e</figure-callout>}}& 0\&le;{\mathrm{\&phi;}}_e\&le;\mathrm{\&pi;}\\ \frac{V_{\mathrm{dm}}}{\mathrm{\&pi;}}(2\mathrm{\&pi;}-{\mathrm{\&phi;}}_e)& \mathrm{\&pi;}{\&le;\mathrm{\&phi;}}_e\&le;2\mathrm{\&pi;}\end{array}\right.$ (formula 1)

Wherein, phase difference _e=ω τ _e, V _DmIt is output pulse amplitude.

The phase demodulation scope of phase discriminator is 0～π, and discriminator sensitivity is

$A_d=\frac{V_{\mathrm{dm}}}{\mathrm{\&pi;}}=\frac{V_{\mathrm{DD}}}{\mathrm{\&pi;}}$ (formula 2)

Because the logic level of XOR gate is 0 and V _DDSo, V _Dm=V _DD

The shortcoming that this method of utilizing the XOR gate phase demodulation exists is that two inputs of requirement must be the square waves of symmetry fully, and symmetrical square wave is difficult to realize.When sine wave is converted to square wave, because the threshold value of high-low level is not a zero level, but greater than zero, so the duty cycle square wave that is changed into by sine wave is all less than 1.Because the input waveform is asymmetric, cause XOR gate itself to produce the extra output that differs, therefore can't obtain result accurately.

Summary of the invention

At the technological deficiency that exists in the prior art scheme, the purpose of this invention is to provide a kind of phase demodulation apparatus and method of transducer of radio frequency adaptation, do not require that the amplitude of two input signals equates; Do not require the square wave that is input as symmetry, promptly exportable result accurately,

The objective of the invention is to be achieved through the following technical solutions:

A kind of phase demodulation apparatus of transducer of radio frequency adaptation is applied to be used to detect the phase place of rf load impedance in the transducer of radio frequency adaptation, comprising:

The signal processing sample circuit is used to obtain voltage and current signal on the radio-frequency transmission line, and the voltage and the current signal of the sine wave gathered are handled the output square-wave signal to monostable flipflop;

Monostable flipflop is handled according to the square-wave voltage and the current signal process of input, and the output pulse control signal is to filter circuit;

Filter circuit carries out low-pass filtering to the burst pulse control signal of input, and output contains the output control signal of voltage and current signal phase difference.

Described signal processing sample circuit gate circuit comparator is treated to square-wave signal with the voltage and the current signal of the sine wave gathered.

Described monostable flipflop comprises, rest-set flip-flop, d type flip flop, JK flip-flop or T trigger.

Described filter circuit comprises low pass filter.

A kind of phase detecting method of transducer of radio frequency adaptation comprises,

A, obtain voltage and current signal on the radio-frequency transmission line, and the voltage and the current signal of the sine wave gathered are handled output square-wave voltage and current signal;

B, according to square-wave voltage and the current signal of input through handling, export the burst pulse control signal;

C, the burst pulse control signal of input is carried out low-pass filtering, output contains the output control signal of voltage and current signal phase difference.

Described steps A comprises, adopts the gate circuit comparator that the voltage and the current signal of the sine wave gathered are treated to square-wave signal.

As seen from the above technical solution provided by the invention, the phase demodulation apparatus of the transducer of a kind of radio frequency adaptation of the present invention and method, be applied in the transducer of radio frequency adaptation, be used for detecting by the radio frequency main transmission line phase place of rf load impedance, described device comprises signal processing sample circuit, monostable flipflop and filter circuit.Wherein, monostable flipflop is not very strict to the requirement of input signal, does not only require that the amplitude of two input signals equates but also do not require to be input as symmetrical square wave, so system realizes than being easier to.Though system is also uncomplicated, this phase demodulation scheme also can well detect the phase place of load impedance.

Description of drawings

Fig. 1 is the schematic block diagram of whole radio-frequency (RF) transmission system;

Fig. 2 is the analog multiplier phase demodulation apparatus structural representation of prior art;

Fig. 3 is the XOR gate phase demodulation apparatus structural representation one of prior art;

Fig. 4 is the XOR gate phase demodulation apparatus structural representation two of prior art;

Fig. 5 is the indicatrix schematic diagram one of the XOR gate phase demodulation apparatus of prior art;

Fig. 6 is the indicatrix schematic diagram two of the XOR gate phase demodulation apparatus of prior art;

Fig. 7 is the indicatrix schematic diagram three of the XOR gate phase demodulation apparatus of prior art;

Fig. 8 is the phase demodulation apparatus structural representation of the transducer of radio frequency adaptation of the present invention;

Fig. 9 is the graphical diagram of rest-set flip-flop of phase demodulation apparatus of the transducer of radio frequency adaptation of the present invention;

Figure 10 is the state transition diagram of rest-set flip-flop of phase demodulation apparatus of the transducer of radio frequency adaptation of the present invention;

Figure 11 is the waveform schematic diagram of rest-set flip-flop of phase demodulation apparatus of the transducer of radio frequency adaptation of the present invention;

Figure 12 be radio frequency adaptation of the present invention transducer phase demodulation apparatus the indicatrix schematic diagram of rest-set flip-flop.

Embodiment

The phase demodulation apparatus of the transducer of a kind of radio frequency adaptation of the present invention and method, as shown in Figure 8, it is applied in the transducer of radio frequency adaptation, is used for detecting by the radio frequency main transmission line phase place of rf load impedance, and its embodiment is:

As shown in Figure 8, the phase demodulation apparatus of the transducer of a kind of radio frequency adaptation of the present invention comprises signal processing sample circuit, monostable flipflop and filter circuit.Wherein,

The signal processing sample circuit is used to obtain voltage and current signal on the radio-frequency transmission line, and the voltage and the current signal of the sine wave gathered are handled the output square-wave signal to monostable flipflop; The concrete gate circuit comparator that adopts of this example becomes square wave with the primary voltage current sinusoidal conversion of signals of importing.

Monostable flipflop is handled according to the square-wave voltage and the current signal process of input, and the output pulse control signal is to filter circuit; The concrete rest-set flip-flop that adopts of this example is as monostable flipflop.As shown in Figure 9, be the graphical diagram of rest-set flip-flop, rest-set flip-flop has two inputs, and SET and RESET can put 1 and put 0 to trigger respectively.It is effective that input adds circle expression low level.There are the output Q and the Q of two complementations to mend, generally the state indication end of Q as trigger.Figure 10 is the state transition diagram of rest-set flip-flop, therefrom can clearly be seen that the logic function of rest-set flip-flop: if originally state is 0, import then that state still be 0 behind the RESET signal, import the SET signal after flip-flop states become 1.If originally state is 1, import then that flip-flop states still be 1 behind the SET signal, import the RESET signal after state become 0.

R end that the square-wave voltage of input and current signal are added to rest-set flip-flop respectively and S end.The output of rest-set flip-flop is put 0 with regard to a period of time so, and a period of time is put 1, puts the phase difference that 1 time length depends on R, two port signals of S.

Described monostable flipflop also can adopt d type flip flop, JK flip-flop or T trigger except that adopting rest-set flip-flop.

Filter circuit carries out low-pass filtering to the burst pulse control signal of input, and output contains the output control signal of voltage and current signal phase difference.Filter circuit adopts low pass filter, carries out low-pass filtering at the rest-set flip-flop output, and the voltage level that obtains and put 1 time correlation that is to say the output signal that has obtained containing phase information, has finished phase discrimination function.The waveform schematic diagram of rest-set flip-flop as shown in figure 11.

Figure 12 is the performance diagram of rest-set flip-flop phase demodulation, can see, its characteristic curve is a straight line, shines in pairs with the cosine function of analog multiplier output is suitable.

In sum, the rest-set flip-flop that relates among the present invention is not very strict to the requirement of input signal, does not only require that the amplitude of two input signals equates but also do not require to be input as symmetrical square wave, so system realizes than being easier to.Because in the present invention, input signal is converted into burst pulse earlier, that is to say, has only the rising edge of pulse to work, so duty of ratio can not impact the result.As seen phase demodulation apparatus of the present invention does not require the duty ratio of Us and Uc.

Moreover by the rest-set flip-flop principle as can be known, it has one to put 1 end and one and put 0 end, after the two-way input signal becomes burst pulse respectively, is equivalent to repeatedly trigger be put 1, put 0.Determined the output signal pulses width from putting for 1 to the time of putting 0.So output pulse width is proportional to phase difference.So output signal is about the phase difference linearity.

As seen, the precision height of its phase demodulation, good linearity, and also the phase demodulation scope is near 2 π, applied range.

The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claim.

Claims (3)

1. the phase demodulation apparatus of the transducer of a radio frequency adaptation is applied to be used to detect the phase place of rf load impedance in the transducer of radio frequency adaptation, it is characterized in that, comprising:

The signal processing sample circuit, described signal processing sample circuit comprises the gate circuit comparator, be used to obtain voltage and current signal on the radio-frequency transmission line, and the voltage and the current signal of the sine wave gathered are handled, output square-wave voltage and current signal are to monostable flipflop;

Monostable flipflop is handled the square-wave voltage and the current signal of input, and the output burst pulse controls signal to filter circuit, and described burst pulse has only the rising edge of pulse to work;

Filter circuit, described filter circuit comprises low pass filter, and the burst pulse control signal of input is carried out low-pass filtering, output contains the output control signal of voltage and current signal phase difference.

2. the phase demodulation apparatus of the transducer of radio frequency adaptation according to claim 1 is characterized in that, described monostable flipflop comprises, rest-set flip-flop, d type flip flop, JK flip-flop or T trigger.

3. the phase detecting method of the transducer of a radio frequency adaptation is characterized in that, comprising:

A, obtain voltage and current signal on the radio-frequency transmission line, and adopt the gate circuit comparator that voltage and the current signal of the sine wave gathered are handled, export square-wave voltage and current signal;

B, described square-wave voltage and current signal are handled, output burst pulse control signal, described burst pulse has only the rising edge of pulse to work;

C, described burst pulse control signal is carried out low-pass filtering, output contains the output control signal of voltage and current signal phase difference.

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