CN103389623A - Focusing and leveling device - Google Patents
Focusing and leveling device Download PDFInfo
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- CN103389623A CN103389623A CN2012101438442A CN201210143844A CN103389623A CN 103389623 A CN103389623 A CN 103389623A CN 2012101438442 A CN2012101438442 A CN 2012101438442A CN 201210143844 A CN201210143844 A CN 201210143844A CN 103389623 A CN103389623 A CN 103389623A
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Abstract
A focusing and leveling device includes a lighting unit, a projection unit, a detection unit and a relay unit. The lighting unit includes a light source and a projection slit array, and the light source is used for producing illumination light; the projection slit array in the lighting unit is projected onto the surface of a silicon wafer by the projection unit to form a plurality of measuring light spots; the detection unit comprises a scan reflector for the modulation of incident optical signals; the relay unit includes a detection slit array and a width detecting unit; wherein the width detecting unit can detect in real time the width of the projection light spots. Through use of the focusing and leveling device, measuring errors caused by uneven light intensity distribution of the light spots can be well avoided.
Description
Technical field
The present invention relates to field of lithography, relate in particular to the focusing leveling device for projection mask aligner.
Background technology
Projection mask aligner a kind ofly projects to device on the silicon chip face to the pattern on mask by object lens.In apparatus for projection exposure, must there is the automatic focusing leveling system silicon chip face accurately to be brought into the exposure position of appointment.Put down in writing a kind of focusing-levelling detection device in US Patent No. 4558949, its system principle as shown in Figure 1.Wherein, the light of lighting unit 101 outgoing, reflex to silicon chip surface 104 by the first plane mirror 103 after projection slit 102, forms the projection hot spot; Silicon chip surface 104 reflexes to the second plane mirror 105 with light; Be incident on scanning reflection mirror 106 from the light of the second plane mirror 105 outgoing; Scanning reflection mirror 106 is done periodically simple harmonic oscillation, light signal is modulated, to improve the signal to noise ratio (S/N ratio) of measuring-signal; The emergent light of scanning reflection mirror 106, through surveying slit 107, incides on photodetector 108, and photodetector 108 is again according to the received corresponding voltage signal of light intensity magnitude output.Due to the modulating action of scanning reflection mirror 106, what photodetector 108 was finally exported is periodic dynamic voltage signal, as shown in Figure 2.Finally,, by this dynamic voltage signal is carried out analyzing and processing, realize the detection of silicon chip surface 104 defocusing amounts.
Yet generally, the light distribution in hot spot is also inhomogeneous, will make the dynamic voltage signal distorted (as shown in Figure 3) of final output, and will there will be the larger error to the detection of silicon chip surface 104 defocusing amounts this moment.
Summary of the invention
In order to address the above problem, the present invention proposes a kind of focusing leveling device, comprise lighting unit, projecting cell, probe unit and TU Trunk Unit, wherein, lighting unit comprises for generation of the light source of illumination light and projection slit array;
Projecting cell projects to silicon chip surface with the projection slit array in lighting unit, forms a plurality of measurement hot spots;
Probe unit comprises scanning reflection mirror, is used for incident optical signal is modulated;
TU Trunk Unit comprises surveys slit array and width detection unit;
It is characterized in that the width of described width detection unit real-time detection projection hot spot.
Wherein, described width detection unit is surveyed on the direction of scanning of scanning reflection mirror.
Wherein, the slit width of described detection slit array equates with the width of surveying hot spot.
Wherein, scanning reflection mirror is done simple harmonic motion, and its frequency is f, choose the dynamic width signal that detects according to the width detection unit, therefrom extract 1f, 2f signal intensity, according to the power of 2f signal, judge whether to carry out the detection of silicon chip surface defocusing amount according to the 1f signal in the accurate measurement scope.
Wherein, described width detection unit is ccd array.
Wherein, while being 0 ° and amplitude greater than default threshold epsilon, the expression silicon chip enters the accurate measurement scope when the phase place of described 2f signal.
The invention allows for a kind of method of utilizing said apparatus to carry out focusing and leveling, comprise in the method: step 1, light spot image, 1f square wave and 2f square wave input that the width detection unit is gathered, to the FPGA unit, obtain 1f signal intensity and 2f signal intensity; Step 2, the described 2f signal intensity of contrast and the size of subscribing threshold,, if described 2f signal intensity, less than described reservation threshold, represents to exceed the accurate measurement scope, finish to measure, otherwise carry out step 3; Step 3, obtain side-play amount e according to described 1f signal intensity, and is last according to the geometric relationship between defocusing amount Z and described side-play amount e, obtains Z.Wherein step 1 comprises and utilizes the FPGA unit to extract the spot width time series, described spot width time series is carried out 1f signal digital frequency-selective filtering, obtain the time series of high s/n ratio, the time series of described high s/n ratio is multiplied each other with 1f square wave time series, 2f square wave time series respectively, and multiplied result is carried out respectively low-pass digital filter, obtain 1f signal intensity and 2f signal intensity.
The present invention has adopted the width detection unit to replace common photodetector, on the direction of scanning of scanning reflection mirror, carries out the real-time detection of projected light spot width.At this moment, the signal of the final output in width detection unit is periodic dynamic width signal, finally this signal is carried out analyzing and processing, realizes the detection of silicon chip surface defocusing amount.Thereby avoided well the measuring error that causes because of the light distribution inequality in hot spot.
Description of drawings
Can be by following detailed Description Of The Invention and appended graphic being further understood about the advantages and spirit of the present invention.
Figure 1 shows that the structural representation of typical focusing-levelling detection device in prior art;
Figure 2 shows that when the light distribution of adopting in the hot spot that device shown in Figure 1 obtains is even, adopt photodetector array to carry out light intensity and survey, finally the periodic dynamic voltage signal of output;
Figure 3 shows that when the light distribution of adopting in the hot spot that device shown in Figure 1 obtains is inhomogeneous, adopt photodetector array to carry out light intensity and survey, finally the periodic dynamic voltage signal of output;
Figure 4 shows that the structural representation according to focusing and leveling system of the present invention;
Figure 5 shows that the projection hot spot is at the characteristics of motion schematic diagram of surveying on slit;
Figure 6 shows that scanning reflection mirror does simple harmonic motion (frequency is f), and e gets 0, ± 0.25d, ± during 0.5d, the spectrogram of the oscillogram of the spot width L that ccd array records (t) and L (t);
Figure 7 shows that the 1f that extracts from dynamic spot width signal, the graph of a relation that the amplitude of 2f and phase place change with e;
Figure 8 shows that signal processing flow figure.
Embodiment
Describe specific embodiments of the invention in detail below in conjunction with accompanying drawing.
According to the structure of focusing leveling device of the present invention as shown in Figure 4, this device mainly is comprised of lighting unit 201, projecting cell 203, probe unit 206 and TU Trunk Unit 208.Wherein, lighting unit 201 produces the required illumination light of focusing leveling device; Projecting cell 203 projects to silicon chip surface 204 with the projection slit array 202 in lighting unit, forms a plurality of measurement hot spots, obtains the pattern information of silicon chip surface; 206 of probe units use 205 pairs of light signals of scanning reflection mirror to modulate, to improve the signal to noise ratio (S/N ratio) of measuring-signal; The picture of projection slit array 202 incides on ccd array 209 after the detection slit array 207 in TU Trunk Unit 208, relay imaging mirror group after probe unit 206.Ccd array 209 on the direction of scanning of scanning reflection mirror 205, carries out the real-time detection of projected light spot width, and due to the modulating action of scanning reflection mirror 205, the signal of ccd array 209 final outputs is periodic dynamic optical spot width signal.Finally this signal is carried out analyzing and processing, realize the detection of silicon chip surface 204 defocusing amounts.
Figure 5 shows that the projection hot spot at the characteristics of motion schematic diagram of surveying on slit, wherein survey the width of hot spot and the width of detection slit and equate, is all d.In figure, (A) the expression silicon chip is positioned at best focal plane; (B) expression silicon chip out of focus, e wherein represents the side-play amount at spot center and slit center.When silicon chip is positioned at best focal plane position, (c) in figure (A) is depicted as scanning reflection mirror 205 and is positioned at zero-bit, survey hot spot all by surveying slit, survey hot spot this moment and overlap with the center of surveying slit, it is maximal value d that ccd array 209 records spot width; Figure in (A) (b) and (d) be depicted as when scanning reflection mirror 205 forwards or negative sense swing an angle, only some can be by the detection slit to survey hot spot, ccd array 209 records spot width and will diminish; Figure in (A) (a) and (e) be depicted as when scanning reflection mirror 205 forwards or negative sense swing to maximum angle, surveying hot spot fully can't be by the detection slit, ccd array 209 records spot width will be 0.During not in best focal plane position, as shown in (c) in figure (B), the detection hot spot after the reflection of silicon chip face when scanning reflection mirror 205 is positioned at zero-bit, will depart from the center of surveying slit, namely have a side-play amount e when silicon chip; When scanning reflection mirror 205 is done periodic wobble, the (a) and (b) of figure in (B), (d) and (e) shown in, the relative position relation of surveying hot spot and surveying between slit can change, the dynamic optical spot width signal that obtains on ccd array 209 also can change, wherein contained and can detect the useful information of surveying facula deviation amount e, and side-play amount e is produced by silicon chip surface 204 defocusing amounts, there is certain geometric relationship between them, therefore can, by analyzing side-play amount e, ask for defocusing amount Z.
Figure 6 shows that scanning reflection mirror 205 does simple harmonic motion (frequency is f), and e gets 0, ± 0.25d, ± during 0.5d, the spectrogram of the oscillogram of the spot width L that ccd array 209 records (t) and L (t), can draw from these frequency spectrums: at e from the process of ± 0.5d to 0, the 1f signal more and more a little less than, and the 2f signal is more and more stronger.And when e equaled 0, the 1f signal was the most weak, and the 2f signal is the strongest; And when e equal ± during 0.5d, the 1f signal is the strongest, the 2f signal is the most weak.
Figure 7 shows that the 1f that extracts from dynamic spot width signal, the graph of a relation that the amplitude of 2f and phase place change with e, therefrom can find out: when e was positioned at [0.5d, 0.5d], the amplitude of 1f was an even function, when e＜0, the 1f phase place is-90 °, as e〉0 the time, the 1f phase place is 90 °, when e=0, the amplitude of 1f and phase place are all 0.Therefore, utilize amplitude and the phase place of 1f, can realize the detection of silicon chip defocusing amount.When e was positioned at [0.5d, 0.5d], 2f had amplitude, and phase place is 0; And when e was positioned at [1.5d ,-0.5d] and [0.5d, 1.5d], the phase place of 2f was 180 °.Therefore can utilize the phase place of 2f and amplitude to judge whether silicon chip enters the accurate measurement scope, consider ± near 0.5d 1f amplitude sensitivity is poor, thereby actual accurate measurement scope should be than [0.5d, 0.5d] slightly little, can establish a threshold epsilon (ε〉0, can be obtained by demarcation), when the 2f phase place is 0 ° and amplitude during greater than ε, the expression silicon chip enters the accurate measurement scope.
Figure 8 shows that signal processing flow figure, whole signal processing flow is: with the light spot image of ccd array 209 high speed acquisition, 1f square wave and 2f square wave input to the FPGA unit (hardware logic programming unit), at first the FPGA unit extracts spot width time series L1[n], to L1[n] carry out 1f signal digital frequency-selective filtering, obtain the time series L2[n of high s/n ratio]; Wherein sampling obtains 1f square wave time series, 2f square wave time series through high-speed AD respectively for 1f square wave and 2f square wave; L2[n with gained] multiply each other with 1f square wave time series, 2f square wave time series respectively, obtain time series L1f[n] and L2f[n]; Again respectively to L1f[n] and L2f[n] carry out low-pass digital filter, obtain 1f signal intensity and 2f signal intensity.1f signal intensity and 2f signal intensity are input to DSP unit (signal acquisition process unit), and at first the DSP unit compares 2f signal intensity and predetermined threshold ε, if the 2f signal intensity, less than ε, represents to exceed the accurate measurement scope; If the 2f signal intensity, more than or equal to ε, is obtained side-play amount e according to the 1f signal intensity, last according to the geometric relationship between defocusing amount Z and e, obtain Z.
Described in this instructions is preferred embodiment of the present invention, and above embodiment is only in order to illustrate technical scheme of the present invention but not limitation of the present invention.All those skilled in the art, all should be within the scope of the present invention under this invention's idea by the available technical scheme of logical analysis, reasoning, or a limited experiment.
Claims (8)
1. a focusing leveling device, comprise lighting unit, projecting cell, probe unit and TU Trunk Unit, wherein,
Lighting unit comprises for generation of the light source of illumination light and projection slit array;
Projecting cell projects to silicon chip surface with the projection slit array in lighting unit, forms a plurality of measurement hot spots;
Probe unit comprises scanning reflection mirror, is used for incident optical signal is modulated;
TU Trunk Unit comprises surveys slit array and width detection unit;
It is characterized in that the width of described width detection unit real-time detection projection hot spot.
2. device according to claim 1, wherein, described width detection unit is surveyed on the direction of scanning of scanning reflection mirror.
3. device according to claim 2, wherein, the slit width of described detection slit array equates with the width of surveying hot spot.
4. device according to claim 3, wherein, scanning reflection mirror is done simple harmonic motion, its frequency is f, choose the dynamic width signal that detects according to the width detection unit, therefrom extract 1f, 2f signal intensity, according to the power of 2f signal, judge whether to carry out the detection of silicon chip surface defocusing amount according to the 1f signal in the accurate measurement scope.
5. device according to claim 4, wherein, described width detection unit is ccd array.
6. device according to claim 5, wherein, while being 0 ° and amplitude greater than default threshold epsilon, the expression silicon chip enters the accurate measurement scope when the phase place of described 2f signal.
7. method of utilizing any one described device in claim 4-6 to carry out focusing and leveling comprises:
Step 1, light spot image, 1f square wave and 2f square wave input that the width detection unit is gathered, to the FPGA unit, obtain 1f signal intensity and 2f signal intensity;
Step 2, the described 2f signal intensity of contrast and the size of subscribing threshold,, if described 2f signal intensity, less than described reservation threshold, represents to exceed the accurate measurement scope, finish to measure, otherwise carry out step 3;
Step 3, according to described 1f signal intensity, obtain side-play amount e, last according to the geometric relationship between defocusing amount Z and described side-play amount e, obtain Z.
8. focusing and leveling method according to claim 7, the described light spot image that the width detection unit is gathered, 1f square wave and 2f square wave input are to the FPGA unit, obtain 1f signal intensity and 2f signal intensity, comprise and utilize the FPGA unit to extract the spot width time series, described spot width time series is carried out 1f signal digital frequency-selective filtering, obtain the time series of high s/n ratio, with the time series of described high s/n ratio respectively with 1f square wave time series, 2f square wave time series multiplies each other, and multiplied result is carried out respectively low-pass digital filter, obtain 1f signal intensity and 2f signal intensity.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104635428A (en) * | 2013-11-14 | 2015-05-20 | 上海微电子装备有限公司 | Focusing and leveling measurement apparatus based on image processing and method thereof |
| WO2017129095A1 (en) * | 2016-01-26 | 2017-08-03 | 上海微电子装备（集团）股份有限公司 | Scan reflective mirror monitoring system and method, focusing and leveling system |
| CN109426101A (en) * | 2017-08-31 | 2019-03-05 | 上海微电子装备（集团）股份有限公司 | A kind of focusing leveling device and method |
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| CN109426101A (en) * | 2017-08-31 | 2019-03-05 | 上海微电子装备（集团）股份有限公司 | A kind of focusing leveling device and method |
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