CN101609264B - Method for improving focusing and leveling measurement accuracy - Google Patents
Method for improving focusing and leveling measurement accuracy Download PDFInfo
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- CN101609264B CN101609264B CN2009100553884A CN200910055388A CN101609264B CN 101609264 B CN101609264 B CN 101609264B CN 2009100553884 A CN2009100553884 A CN 2009100553884A CN 200910055388 A CN200910055388 A CN 200910055388A CN 101609264 B CN101609264 B CN 101609264B
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Abstract
The invention provides a method for improving focusing and leveling measurement accuracy. The method is applied in an optical exposure system and comprises the following steps: obtaining a current driving voltage V1 of a light source of a focusing and leveling device in the system; illuminating an alignment reference plate on a workpiece table in the system by using the light source, carrying out optical-electric signal conversion, and obtaining a peak voltage V2 of converted electric signals; detecting whether the light intensity of the light source is weakened; if so, illuminating the alignment reference plate with the light source, carrying out optical-electric signal conversion, obtaining a peak voltage V3 of the converted electric signals, calculating an optimum driving voltage V4 of the light source and adjusting the voltage of the light source to be the optimum driving voltage V4; and if not, maintaining the voltage of the light source to be constant. The method can discover and solve the problem of measurement accuracy decrease caused by the weakening of light intensity of the light source in time, thereby improving the focusing and leveling measurement accuracy.
Description
Technical field
The present invention relates to the semiconductor lithography field, and be particularly related to a kind of method that improves focusing and leveling measurement accuracy.
Background technology
In the projection lithography device, in order to carry out high-precision measurement in the position to silicon chip surface, for fear of measurement mechanism damage silicon chip, it must be non-contact measurement that focusing and leveling is measured simultaneously, and promptly device itself does not directly contact testee.Contactless focusing leveling measuring method commonly used has three kinds: optical measuring method, capacitance measurement, barometry.In scanning projection lithographic equipment now, use optical measuring method to realize the focusing and leveling measurement more, the technology of optical focusing leveling measurement apparatus is varied.The measuring object of focusing and leveling measurement apparatus is a silicon chip surface, and so because of different operating modes such as graphics arts, the reflectance varies of measuring object is bigger, might reach 10% to 100%.So, be one of focusing and leveling measurement apparatus subject matter that need solve to the adaptivity of different silicon chip surface reflectivities.
In the prior art that focusing and leveling is measured, some adopts the measurement means of beam split difference on light path, thereby avoids the influence of different reflectivity to measurement result, as the focusing and leveling measuring technique of ASML company; Some then is chosen in carries out the automatic gain adjusting on the circuit, promptly judge current silicon chip reflectivity according to the peak value or the effective value of current photodetector output, thereby on signal conditioning circuit, carry out the corresponding gain-adjusted that gets, as the focusing and leveling measuring technique of Nikon.Yet along with the decline of light source life, under same driving voltage, the power of light source output will descend synchronously, and the described technology of the latter just must take appropriate measures, otherwise the accuracy of measurement result will descend.According to the product maintenance handbook of Nikon as can be known, the described technology of the latter adopts the gain compensation technology to solve this problem.Promptly, gain is compensated according to the working time of current light source.As, when the light source works time was 0, the circuit gain of 50% silicon chip reflectivity correspondence was 1; And when the light source works time was 600 hours, the circuit gain of 50% silicon chip reflectivity correspondence was 1.5.This technology has solved the influence of light source life to the measurement result degree of accuracy well, but also there is following deficiency in it: do not solve light source life to measuring the influence of repeatable accuracy, when the optical power down of light source output, the signal to noise ratio (S/N ratio) of measuring-signal also descends after its opto-electronic conversion, iff carrying out gain-adjusted, can not eliminate signal to noise ratio (S/N ratio) fully and descend measuring the influence of repeatable accuracy.
Summary of the invention
In order to overcome the shortcoming that exists in the prior art, the invention provides a kind of method, can when the elimination light source life is to the influence of measurement result degree of accuracy, not produce the problem that descends the measurement repeatable accuracy is exerted an influence because of signal to noise ratio (S/N ratio).
To achieve these goals, the present invention proposes a kind of method that improves focusing and leveling measurement accuracy, described method is applied to optical exposure system, may further comprise the steps: when in described system, focusing and leveling measurement apparatus being installed for the first time, obtain the current driving voltage V1 of the light source of described focusing leveling device; With the alignment reference plate on the work stage in the described system of described light source irradiation, obtain from the light signal of described alignment reference plate reflection and carry out the photosignal conversion by described focusing and leveling measuring system, obtain the first peak threshold voltage V2 of conversion back electric signal; Whether the light intensity that detects described light source dies down, if, then use the described alignment reference plate of described light source irradiation, obtain from the light signal of described alignment reference plate reflection and carry out the photosignal conversion by described focusing and leveling measuring system, obtain the second crest voltage V3 of conversion back electric signal, calculate the optimal drive voltage V4 of described light source, computing formula is V4=V1*f (V2, V3), wherein (V2 V3) is the functional relation of V2 and V3 to f, is optimal drive voltage V4 with the voltage-regulation of described light source, if not, then keep the voltage of described light source constant.
Optionally, and described functional relation f (V2, V3)=V2/V3.
Optionally, described light source is a bulb.
The beneficial effect of the method for raising focusing and leveling measurement accuracy of the present invention mainly shows: when method provided by the invention dies down in the light intensity that detects light source, by the voltage on the timely adjustment light source, make the light intensity of light source remain constant, thereby eliminated effectively because of light source dies down and had influence on the problem of measurement result degree of accuracy, also avoided in addition descending to measuring the problem that repeatable accuracy exerts an influence because of signal to noise ratio (S/N ratio).
Description of drawings
Fig. 1 is optical exposure system first synoptic diagram;
Fig. 2 is optical exposure system second synoptic diagram;
Fig. 3 the present invention improves the schematic flow sheet of the method for focusing and leveling measurement accuracy.
Embodiment
Below, the present invention is further illustrated in conjunction with the accompanying drawings.
At first, please refer to Fig. 1, Fig. 1 is optical exposure system first synoptic diagram, can see on scheming, and under the irradiation of illuminator 100, the light source of illuminator 100 exposes the image projection on the mask 220 to silicon chip 420 by projection objective 310.Mask 220 is by mask platform 210 supportings, and silicon chip 420 is by work stage 410 supportings.In Fig. 1, a silicon slice focusing and leveling measurement apparatus 500 is arranged between projection objective 310 and silicon chip 420, it is 300 rigidly connected that this device and projection objective support, be used for measurement to the positional information on silicon chip 420 surfaces, measurement result is sent to silicon chip surface position control system 560, after the calculating through signal Processing and focusing and leveling amount, the position that drives 430 pairs of work stage 410 of focusing and leveling actuator is adjusted, and finishes the focusing and leveling of silicon chip 420.
Except silicon chip 420, alignment reference plate 440 also is one of measuring object of focusing and leveling measurement apparatus 500.In projection mask aligner, may comprise a plurality of alignment reference plate 440.Fig. 2 is optical exposure system second synoptic diagram, it is the synoptic diagram that focusing and leveling measurement apparatus 500 is measured alignment reference plate 440, the relative position of other devices and light path all with Fig. 2 in introduced the same, unique difference is exactly that Fig. 1 measures silicon chip 420, Fig. 2 measures alignment reference plate 440.
Then, please refer to Fig. 3, Fig. 3 is the schematic flow sheet that the present invention improves the method for focusing and leveling measurement accuracy, as we can see from the figure, the present invention includes following steps: step 11: when in described system, focusing and leveling measurement apparatus being installed for the first time, obtain the current driving voltage V1 of the light source of described focusing leveling device, described light source is a bulb, because be first use, therefore bulb can not occur causing the problem that light intensity dies down under normal voltage work because of wearing out, and described current driving voltage V1 in this case just can be as being the optimal drive voltage use; Step 12: with the alignment reference plate on the work stage in the described system of described light source irradiation, obtain from the light signal of described alignment reference plate reflection and carry out the photosignal conversion by described focusing and leveling measuring system, obtain the first peak threshold voltage V2 of conversion back electric signal, electric signal after the conversion is a sine wave signal, and the first peak threshold voltage V2 that is obtained is the maximal value of sinusoidal wave amplitude; Step 13: whether the light intensity that detects described light source dies down; Step 14: if, then use the described alignment reference plate of described light source irradiation, obtain from the light signal of described alignment reference plate reflection and carry out the photosignal conversion by described focusing and leveling measuring system, obtain the second crest voltage V3 of conversion back electric signal; Step 15: the optimal drive voltage V4 that calculates described light source, computing formula is V4=V1*f (V2, V3), f (V2 wherein, V3) be the functional relation of V2 and V3, this funtcional relationship can be defined according to actual conditions voluntarily by the research staff, can be for linearity, also can be for nonlinear, such as secondary or funtcional relationship repeatedly, with the linear functional relation example, then described functional relation f (V2, V3)=and V2/V3, step 16: with the voltage-regulation of described light source is optimal drive voltage V4, in the actual conditions, optimal drive voltage V4 is generally greater than current driving voltage V1, therefore this step is to heighten the voltage of light source in essence, ideally, make heighten the light intensity of the light source behind the voltage and initially the time light source intensity the same; Step 17: if not, then keep the voltage of described light source constant.
Compare with traditional focusing leveling measuring method in optical exposure system, method provided by the invention is by the voltage on the light source that improves the focusing and leveling measurement, the light source that makes light intensity die down returns to the light intensity of primary light source again, thereby, can not introduce the new problem that descends the measurement repeatable accuracy is exerted an influence because of signal to noise ratio (S/N ratio) from having avoided in essence because of light source life causes the influence of light intensity to the measurement result precision yet.
Though the present invention discloses as above with preferred embodiment, so it is not in order to limit the present invention.The persond having ordinary knowledge in the technical field of the present invention, without departing from the spirit and scope of the present invention, when being used for a variety of modifications and variations.Therefore, protection scope of the present invention is as the criterion when looking claims person of defining.
Claims (3)
1. method that improves focusing and leveling measurement accuracy, described method is applied to optical exposure system, it is characterized in that may further comprise the steps: when in described system, focusing and leveling measurement apparatus being installed for the first time, obtain the current driving voltage V1 of the light source of described focusing leveling device; With the alignment reference plate on the work stage in the described system of described light source irradiation, obtain from the light signal of described alignment reference plate reflection and carry out the photosignal conversion by described focusing and leveling measuring system, obtain the first peak threshold voltage V2 of conversion back electric signal; Whether the light intensity that detects described light source dies down, if, then use the described alignment reference plate of described light source irradiation, obtain from the light signal of described alignment reference plate reflection and carry out the photosignal conversion by described focusing and leveling measuring system, obtain the second crest voltage V3 of conversion back electric signal, calculate the optimal drive voltage V4 of described light source, computing formula is V4=V1*f (V2, V3), wherein (V2 V3) is the functional relation of V2 and V3 to f, is optimal drive voltage V4 with the voltage-regulation of described light source, if not, then keep the voltage of described light source constant.
2. the method for raising focusing and leveling measurement accuracy according to claim 1, it is characterized in that described functional relation f (V2, V3)=V2/V3.
3. the method for raising focusing and leveling measurement accuracy according to claim 1 is characterized in that described light source is a bulb.
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| CN101609264B true CN101609264B (en) | 2011-03-30 |
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| CN102830590B (en) * | 2011-06-14 | 2015-04-15 | 上海微电子装备有限公司 | Light source life monitoring system and its monitoring method |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5015866A (en) * | 1988-12-05 | 1991-05-14 | Nikon Corporation | Stage apparatus in exposing apparatus |
| CN101089732A (en) * | 2006-06-14 | 2007-12-19 | 株式会社阿迪泰克工程 | Lighting device for exposal |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5015866A (en) * | 1988-12-05 | 1991-05-14 | Nikon Corporation | Stage apparatus in exposing apparatus |
| CN101089732A (en) * | 2006-06-14 | 2007-12-19 | 株式会社阿迪泰克工程 | Lighting device for exposal |
Non-Patent Citations (3)
| Title |
|---|
| JP特开平10-300573A 1998.11.13 |
| JP特开平6-29187A 1994.02.04 |
| JP特开昭63-46728A 1988.02.27 |
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Address after: 201203 Zhangjiang High Tech Park, Shanghai, Zhang Dong Road, No. 1525 Patentee after: Shanghai microelectronics equipment (Group) Limited by Share Ltd Address before: 201203 Zhangjiang High Tech Park, Shanghai, Zhang Dong Road, No. 1525 Patentee before: Shanghai Micro Electronics Equipment Co., Ltd. |
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