CN101482704A - Alignment light intensity signal collection and demodulation apparatus - Google Patents

Abstract

The invention provide an aligning signal acquiring and demodulating device for acquiring the aligning light intensity signal modulated by an optical signal modulator. The aligning signal acquiring and demodulating device comprises a photoelectric sensor, a preamplifier, a variable gain amplifier, a band pass filter, a reference signal generator and a demodulator. The device can avoid the phase difference between the modulating signal and the aligning signal, can implement the demodulation process of the aligning signal and improve the accuracy of the aligning signal.

Description

Aim at light intensity signal collection and demodulating equipment

Technical field

The invention relates to signals collecting and demodulating equipment in a kind of SIC (semiconductor integrated circuit) photoetching production equipment, and particularly relevant for a kind of aligning light intensity signal collection and demodulating equipment.

Background technology

In the manufacture process of integrated circuit (IC) or other microdevice, by lithographic equipment, the multilayer mask that will have different mask patterns is imaged on the silicon chip that is coated with photoresist under accurately aiming at successively, for example semi-conductor silicon chip or LCD plate.The alignment system of lithographic equipment, its major function are to realize mask-silicon chip aligning before the alignment exposure, to satisfy the requirement of alignment precision.

At present, the most alignment device that adopts of lithographic equipment is the grating alignment system, as shown in Figure 1, this grating alignment device comprises, illuminator 1, supporting mask 3, mask platform 4, aims at grating marker 2, projection optical system 5, silicon chip 6, silicon chip grating marker 7, base station 8, motion platform 9, aims at grating marker 10, servo motion control system 11, aims at illuminator 12 and silicon chip and aim at and gather and disposal system 300.

Illuminator 1 provides exposing light beam; Mask platform 4 is used to support mask 3; Projection optical system 5 is used for the mask pattern on the mask 3 is projected to silicon chip 6; Base station 8 supports silicon chip 6; Motion platform 9 drives base station 8x and y moves to linear reciprocation, and motion platform 9 is by servo motion control system 11 and measuring system IFx and IFy gathers and control; Aiming at illuminator 12 provides silicon chip to aim at illumination; Silicon chip aim to be gathered with disposal system 300 and is comprised that the collection that is used for the alignment light signal with processing module 301, in the collection and the processing module 303 of position data, based on aiming at light intensity signal and position data, determines the registration signal processing module 302 of aligned position.

In the alignment scanning process, aim at a plurality of discrete wavelength illuminating bundles that illuminator 12 provides, shine on silicon chip grating marker 7 or the base station grating marker 10 through Transmission Fibers, diffraction takes place, diffraction light carries about aiming at the structural information of grating marker, through alignment optical imaging system (figure does not show), on reference grating front surface, form light and dark periodicity hot spot striped.Along with the at the uniform velocity straight line of motion platform moves, driving silicon chip grating marker 7 and base station grating marker 10 moves with uniform velocity together, periodically the hot spot striped will be at the uniform velocity inswept with reference to grating, the collection of alignment light signal and processing module 301 will detect the signal curve of the sinusoidal form with constant cycle, the collection of binding site data and processing 303, through registration signal processing module 302, can obtain to do the light intensity curve that sinusoidal form changes, thereby determine aligned position with the position.Because the intensity of alignment optical signal is faint, fluctuation is big, is subjected to characteristics such as working environment interference easily, in the process that registration signal is gathered, for stability and the antijamming capability that improves signal, adopts the modulation and demodulation technology of photosignal usually.Carry out phase modulation (PM) at aligning illuminating bundle end, to obtain to comprise the high-frequency carrier signal of alignment information; Collection terminal in registration signal carries out phase demodulating, introduces reference signal as restituted signal, and the demodulation high-frequency carrier signal extracts the low frequency registration signal that comprises wherein.

(low level light signal is surveyed technique of alignment to document 1, Yang Xingping, Cheng Jianrui, the electronics industry specialized equipment, 2006,140:7～12) disclose a kind of collection and demodulation techniques of lithography alignment signal, this technology adopts former modulation signal (Hinds partitioned signal) as introducing with reference to signal, realizes the demodulation and the gatherer process of registration signal.Yet, since registration signal and modulation signal arrive detuner the path of process different, have phase differential between the two.Phase differential is big more, and the amplitude of output signal is just more little after the demodulation, and precision is also just low more.Though the method that has adopted variable phase to adjust in the document constantly detects the leading and lagged relationship of phase place between registration signal and the modulation signal, is less than certain setting value to adjust phase differential.But, owing to be dynamic adjustment process, make that twice adjustment under same prerequisite may produce different results, and then the repeatable accuracy of influence aligning.In addition, even if the two phase differential has been adjusted to enough little stage (less than certain setting value), still can influence final aligning repeatable accuracy because of there being phase differential.

Summary of the invention

The object of the present invention is to provide a kind of demodulation and harvester of registration signal, to improve the disappearance of prior art.

In order to achieve the above object, the invention provides a kind of registration signal collection and demodulating equipment, gather aligning light intensity signal through the optical signal modulator modulation.Registration signal collection and demodulating equipment comprise photoelectric sensor, prime amplifier, variable gain amplifier, bandpass filter, reference signal generator and detuner.

It is current signal that photoelectric sensor will be aimed at the light intensity conversion of signals; Prime amplifier electrically connects photoelectric sensor, and current signal is converted to voltage signal; Variable gain amplifier electrically connects prime amplifier, and voltage signal is adjusted to the setting amplitude; Bandpass filter electrically connects variable gain amplifier, flip-flop in the filtering voltage signal and interference component, and reference signal generator electrically connects bandpass filter, and isolates reference signal from voltage signal; Detuner electrically connects bandpass filter and reference signal generator, with reference signal voltage signal is carried out demodulation, exports a restituted signal; Low-pass filter electrically connects detuner, and the frequency that is used for the restituted signal of filtering detuner output is the composition of the twice of frequency modulating signal.

Aligning light intensity signal collection provided by the invention and demodulating equipment are isolated the frequency modulating signal composition from modulation light intensity signal (registration signal).Because detachment process makes modulation signal produce fixing phase change, therefore can make registration signal and modulation signal same-phase by adjusting the phase shifter parameter.The aligning light intensity signal collection and the demodulating equipment of adopting said method have been realized light intensity signal collection and demodulation function.

For above and other objects of the present invention, feature and advantage can be become apparent, preferred embodiment cited below particularly, and conjunction with figs. are described in detail below.

Description of drawings

Figure 1 shows that the synoptic diagram of present grating alignment system.

Figure 2 shows that silicon chip registration signal production process synoptic diagram.

Figure 3 shows that the structural representation of aiming at light intensity signal collection and demodulating equipment according to an embodiment of the invention.

Figure 4 shows that the structural representation of the variable gain amplifier of aiming at light intensity signal collection and demodulating equipment according to an embodiment of the invention.

Figure 5 shows that the structural representation of the reference signal generator of the aligning light intensity signal collection of one embodiment of the invention and demodulating equipment.

Figure 6 shows that the aligning light intensity signal collection of one embodiment of the invention and the detuner output waveform and the low-pass filter output waveform synoptic diagram of demodulating equipment.

Embodiment

Figure 2 shows that registration signal production process synoptic diagram.Please refer to Fig. 2,305 for the light signal after the registration signal modulators modulate shines on the alignment mark, through the periodicity hot spot striped of image-forming module generation.In the alignment scanning process, periodically the hot spot striped is at the uniform velocity inswept with reference to grating 306 with the motion of work stage for this, is transferred on the photoelectric sensor through detection optical fiber 307, obtains to aim at light intensity signal 308.In aiming at light intensity signal 308, include the modulation signal ω of high frequency _HThe raster scanning frequency information ω of frequency content (frequency modulating signal) and low frequency _S(being envelope).

Figure 3 shows that the structural representation of aiming at light intensity signal collection and demodulating equipment according to an embodiment of the invention.Aim at light intensity signal collection and demodulating equipment 310 and couple registration signal modulator 320.Aim at light intensity signal collection and demodulating equipment 310 and mainly comprise signal modulating unit, bandpass filter 314, reference signal generator 315, the detuner of forming by optical signal modulator 320, photoelectric sensor 311, prime amplifier 312, variable gain amplifier 313 316.Further also comprise a low-pass filter 317, be used to improve follow-up alignment work precision.

It is current signal that photoelectric sensor 311 will be aimed at the light intensity conversion of signals.Prime amplifier 312 electrically connects photoelectric sensor 311, and current signal is converted to voltage signal.Variable gain amplifier 313 electrically connects prime amplifier 312, and voltage signal is adjusted to the setting amplitude.Bandpass filter 314 electrically connects variable gain amplifier 313, the filtering flip-flop in the filtering voltage signal and other interference component.Reference signal generator 315 electrically connects bandpass filter 314, and isolates reference signal from voltage signal; Detuner 316 electrically connects bandpass filter 314 and reference signal generator 315, with reference signal above-mentioned voltage signal is carried out demodulation, exports a restituted signal; Low-pass filter 317 electrically connects detuner 316, the above-mentioned twice frequency modulating signal composition in the restituted signal of the above-mentioned detuner output of filtering.

In the present embodiment, the frequency of reference signal and frequency modulating signal ω _HIdentical.

In the present embodiment, variable gain amplifier 313 comprises variable-gain amplification circuit 3131, testing circuit 3132, gain control signal generative circuit 3133.Variable-gain amplification circuit 3131 electrically connects prime amplifier 312; Testing circuit 3132 electrically connects variable-gain amplification circuit 3131, and the effective value of testing circuit 3132 detectable voltage signals; Gain control signal generative circuit 3133 electrically connects variable-gain amplification circuit 3131 and testing circuit 3132, generates gain control signal, and adjusts voltage signal to setting amplitude, as shown in Figure 4.

In the present embodiment, bandpass filter 314 employing centre frequencies are modulation signal ω _HThe bandwidth-limited circuit of frequency.

In the present embodiment, reference signal generator 315 comprises zero-crossing comparator 321, bandpass filter 322, phase shifter 323.Zero-crossing comparator 321 is isolated the frequency modulating signal in the voltage signal, and output and the same square-wave signal frequently of modulation signal; Bandpass filter 322, with the frequency modulating signal composition in the filtering square-wave signal, and output and the same reference signal frequently of modulation signal; Phase shifter 323 carries out phase compensation to reference signal, as shown in Figure 5 according to the phase effect of zero- crossing comparator 321 and 322 pairs of reference signals generations of bandpass filter.

In the present embodiment, modulation signal is expressed as:

H=A _HSin (ω _HT+ θ _H)+B _H(formula 1)

Registration signal is expressed as:

S=A _SSin (ω _ST+ θ _S)+B _S(formula 2)

B wherein _HA _H, B _SA _S, ω _Hω _S, can be expressed as by photoelectric sensor 311 detected current signals:

$H\×S=A_H{A}_S\sin ({\mathrm{\ω}}_{H}t+{\mathrm{\θ}}_H)\sin ({\mathrm{\ω}}_{S}t+{\mathrm{\θ}}_S)+A_H{B}_S\sin ({\mathrm{\ω}}_{H}t+{\mathrm{\θ}}_H)$

$+A_S{B}_H\sin ({\mathrm{\ω}}_{S}t+{\mathrm{\θ}}_S)+B_H{B}_S$

$=-\frac{A_H{A}_S}{2}\{\cos [({\mathrm{\ω}}_H+{\mathrm{\ω}}_S)t+({\mathrm{\θ}}_H+{\mathrm{\θ}}_S)]-\cos [({\mathrm{\ω}}_H-{\mathrm{\ω}}_S)t+({\mathrm{\θ}}_H-{\mathrm{\θ}}_S)]\}$

$+A_H{B}_S\sin ({\mathrm{\ω}}_{H}t+{\mathrm{\θ}}_H)+A_S{B}_H\sin ({\mathrm{\ω}}_{S}t+{\mathrm{\θ}}_S)+B_H{B}_S$ (formula 3)

Photoelectric sensor 311 detected light intensity signal frequency contents comprise (ω as can be seen from formula 3 _H+ ω _S), (ω _H-ω _S), ω _H, ω _SAnd flip-flop.

Prime amplifier 312 is converted to voltage signal with the current signal that photoelectric sensor 311 collects.Variable gain amplifier 313 is used for voltage signal is adjusted to the setting amplitude.

This voltage signal is ω by centre frequency then _HThe bandpass filter 314 of (frequency of modulation signal), filtering ω _SComposition and flip-flop keep (ω _H+ ω _S), (ω _H-ω _S), ω _HThree kinds of frequency contents, that is:

$H\×S_{\mathrm{BPF}}=A_H{A}_S\sin ({\mathrm{\ω}}_{H}t+{\mathrm{\θ}}_H)\sin ({\mathrm{\ω}}_{S}t+{\mathrm{\θ}}_S)+A_H{B}_S\sin ({\mathrm{\ω}}_{H}t+{\mathrm{\θ}}_H)$

$=\sin ({\mathrm{\ω}}_{H}t+{\mathrm{\θ}}_H)(A_H{A}_S\sin ({\mathrm{\ω}}_{S}t+{\mathrm{\θ}}_S)+A_H{B}_S)$

$=-\frac{A_H{A}_S}{2}\{\cos [({\mathrm{\ω}}_H+{\mathrm{\ω}}_S)t+({\mathrm{\θ}}_H+{\mathrm{\θ}}_S)]-\cos [({\mathrm{\ω}}_H-{\mathrm{\ω}}_S)t+({\mathrm{\θ}}_H-{\mathrm{\θ}}_S)]\}$

$+A_H{B}_S\sin ({\mathrm{\ω}}_{H}t+{\mathrm{\θ}}_H)$ (formula 4)

By in the formula 4 as can be seen, have only (ω as sin _HT+ θ _H)=0 o'clock is 0 through filtered voltage of signals.Reference signal generator 315 can the signal behind bandpass filtering, produce and the registration signal same-phase according to these characteristics, and the reference signal R=A identical with frequency modulating signal _RSin (ω _RT+ θ _R), ω wherein _R=ω _H, θ _R=θ _HFig. 5 illustrates the structural representation of reference signal generator 315.For the input signal of certain frequency, zero-crossing comparator 321 and bandpass filter 322 caused phase change can be thought constant.Phase shifter 323 is used to compensate comparer 321 and bandpass filter 322 caused phase change, i.e. R=A _RSin (ω _RT+ θ _R), ω wherein _R=ω _H, θ _R=θ _H, finally make two signal phases of detuner input identical.

The reference signal that detuner 316 utilizes reference signal generator to produce is to carrying out demodulation through bandpass filter 314 filtered signals, that is:

$H\·S_{\mathrm{BPF}}\·R=\frac{A_H{A}_S{A}_R}{4}\{-\sin [(2{\mathrm{\ω}}_H+{\mathrm{\ω}}_S)t+({\mathrm{\θ}}_H+{\mathrm{\θ}}_S+{\mathrm{\θ}}_R)]$

(formula 5)

$+\sin [{\mathrm{\ω}}_{S}t+({\mathrm{\θ}}_H+{\mathrm{\θ}}_S-{\mathrm{\θ}}_R)]+\sin [(2{\mathrm{\ω}}_H-{\mathrm{\ω}}_S)t+({\mathrm{\θ}}_H-{\mathrm{\θ}}_S+{\mathrm{\θ}}_R)]$

$-\sin [(-{\mathrm{\ω}}_S)t+({\mathrm{\θ}}_H-{\mathrm{\θ}}_S-{\mathrm{\θ}}_R)]\}$

$-\frac{A_H{B}_S{A}_R}{2}\{\cos [\left(2{\mathrm{\ω}}_H\right)t+{\mathrm{\θ}}_H+{\mathrm{\θ}}_R]-\cos ({\mathrm{\θ}}_H-{\mathrm{\θ}}_R)\}$

Because the frequency of reference signal is got ω _R=ω _H, phase theta _R=θ _H, then formula 5 can get:

$=\frac{A_H{A}_S{A}_R}{4}\{\mathrm{}$

$-\sin [(2{\mathrm{\ω}}_H+{\mathrm{\ω}}_S)t+(2{\mathrm{\θ}}_H+{\mathrm{\θ}}_S+)]$

(formula 6)

$+\sin [(2{\mathrm{\ω}}_H-{\mathrm{\ω}}_S)t+(2{\mathrm{\θ}}_H-{\mathrm{\θ}}_S)]$

$+2\sin ({\mathrm{\ω}}_{S}t+{\mathrm{\θ}}_S)\}$

$-\frac{A_H{B}_S{A}_R}{2}\{\cos [\left(2{\mathrm{\ω}}_H\right)t+2{\mathrm{\θ}}_H]-0\}$

By formula 6 as can be known, the restituted signal behind detuner 316 comprises ω _S, 2 ω _H, (2 ω _H+ ω _S), (2 ω _H-ω _S) four kinds of frequency contents.By analog filter 317, filtering is to 2 ω in the quasi-analog signal _H, (2 ω _H+ ω _S), (2 ω _H-ω _S) composition and partial noise (because ω _Hω _S, suitably dispose filtering circuit and can obtain ω _S), obtain registration signal $\frac{A_H{A}_S{A}_R}{2}\sin ({\mathrm{\ω}}_{S}t+{\mathrm{\θ}}_S)o.$

Fig. 6 shows the form figure of photosignal, and wherein, signal 331 is detuner 316 output signals, and this signal comprises ω _SWith 2 ω _HFrequency content; Signal 332 is for through the output signal behind the low-pass filter 317, filtering 2 ω _HFrequency content has kept ω _SFrequency content, signal 332 are required align frequencies signal.

The invention provides a kind of aligning light intensity signal collection and demodulating equipment, this device is introduced demodulating process by isolating the frequency modulating signal composition in the registration signal (signal to be demodulated) as the reference signal, thereby realizes the collection and the modulation function of registration signal.This device can be avoided having phase differential between modulation signal and the registration signal (signal to be demodulated), realizes the demodulating process of registration signal, improves the precision of registration signal (after low-pass filtering).Simultaneously, this demodulating equipment can also be simplified the registration signal acquisition system, improves the collecting efficiency of registration signal.

Concrete case study on implementation only is a preferable case study on implementation of the present invention described in the present invention, is not to be used for limiting practical range of the present invention.Be that all equivalences of doing according to the content of the present patent application claim change and modification, all should be as technology category of the present invention.

Claims (9)

1, a kind of registration signal collection and demodulating equipment comprise:

The signal modulating unit is used for being converted to the voltage signal of setting amplitude with aiming at light intensity signal after modulation; Bandpass filter, flip-flop and interference component in the described voltage signal of filtering; Generate reference signal after a described voltage signal part enters reference signal generator, another part enters detuner; Described detuner carries out demodulation with described reference signal to described voltage signal, the output restituted signal.

2, registration signal collection as claimed in claim 1 and demodulating equipment is characterized in that, described signal modulating unit comprises: optical signal modulator is modulated the light intensity signal amplitude; Photoelectric sensor, being used for aligning light intensity conversion of signals is current signal; Prime amplifier is converted to voltage signal with current signal; Variable gain amplifier is adjusted to the setting amplitude with voltage signal.

3, according to described aligning light intensity signal collection of claim 1 and demodulating equipment, it is characterized in that above-mentioned variable gain amplifier comprises:

Variable-gain amplification circuit is connected with described prime amplifier;

Testing circuit is connected with described variable-gain amplification circuit, is used to detect the effective value of described voltage signal;

The gain control signal generative circuit is connected with testing circuit with described variable-gain amplification circuit, generates gain control signal, adjusts described voltage signal to described setting amplitude.

According to described aligning light intensity signal collection of claim 1 and demodulating equipment, it is characterized in that 4, it is the bandwidth-limited circuit of frequency modulating signal that described bandpass filter adopts centre frequency.

According to described aligning light intensity signal collection of claim 1 and demodulating equipment, it is characterized in that 5, the frequency of described reference signal is identical with the described voltage signal frequency that enters detuner.

6, registration signal collection as claimed in claim 1 and demodulating equipment is characterized in that, described restituted signal comprises twice frequency modulating signal composition and raster scanning frequency content.

7, registration signal collection as claimed in claim 6 and demodulating equipment is characterized in that, comprise a low-pass filter further, in order to the twice frequency modulating signal composition in the described restituted signal of filtering.

8, registration signal collection according to claim 6 and demodulating equipment is characterized in that, described reference signal generator comprises:

Zero-crossing comparator is isolated the frequency modulating signal in the described voltage signal, and output and the same square-wave signal frequently of modulation signal;

Bandpass filter, in order to the center frequency composition in the described square-wave signal of filtering, and output and the same above-mentioned reference signal frequently of modulation signal; And

Phase shifter to the phase effect that described reference signal produces, carries out phase compensation to described reference signal according to described zero-crossing comparator and bandpass filter.

9, registration signal collection according to claim 6 and demodulating equipment is characterized in that, described detuner carries out multiplying with described voltage signal and reference signal, are used for separating the frequency modulating signal and the raster scanning frequency of described modulated voltage signal.

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