CN101169594B - Photo-etching machine imaging quality measuring method - Google Patents
Photo-etching machine imaging quality measuring method Download PDFInfo
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- CN101169594B CN101169594B CN2007101709161A CN200710170916A CN101169594B CN 101169594 B CN101169594 B CN 101169594B CN 2007101709161 A CN2007101709161 A CN 2007101709161A CN 200710170916 A CN200710170916 A CN 200710170916A CN 101169594 B CN101169594 B CN 101169594B
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Abstract
The invention relates to a method of measuring the imaging quality of a photoetching machine, and includes the following steps: the DFOCAL-mark images evenly distributed on a mask are exposed onto a silicon chip to form n exposure sites under n defocusing amount of the photoetching machine. An aligning system is utilized to conduct an equally-spaced sample measurement to the n exposure sites to obtain n/m on-site aligning position for each mark. The deviation of the horizontal position of the mark imaging and the variation law of the defocusing amount of the silicon chip are utilized to calculate the approximate position of the optimal focus for each DFOCAL marking point on the exposure site. The corresponding aligning position of the DFOCAL marking point on the n/m sites closest to the approximate position of the optimal focus for each DFOCAL marking point on the exposure site is measured. The optimal focus position for each DFOCAL marking point is figured out precisely. The axial image quality parameter is calculated. The invention can conduct a highly accurate, extensive and fast measurement to the axial image quality parameter for the imaging quality of a photoetching machine by utilizing DFOCAL marks.
Description
Technical field
The present invention relates to a kind of measuring method of image forming quality of photoetching machine, relate in particular to a kind of FOCAL (the mirror image focal plane detects alignment mark) mark of dual fine structure that utilizes and measure the method for photoetching arbor to the picture element parameter.
Background technology
Litho machine is one of key equipment in integrated circuit production and the manufacture process.Forming the picture element amount is the key factor that influences litho machine photolithography resolution and alignment precision.Parameters such as the curvature of field of optimal focal plane skew, image planes inclination and projection objective and astigmatism are to influence the principal element of litho machine along the image quality of optical axis direction, therefore are called as the axial picture element parameter of litho machine.They mainly influence lithography performance indexs such as lithographic feature size, imaging lines homogeneity, depth of focus.Along with reducing of lithographic feature size and diminishing of focal depth range, the detection of litho machine focal plane will become more and more important with correction.The detection technique of therefore axial picture element parameter also becomes the important composition of modern lithographic technologies.High precision, axially picture element parameter detecting function has been called one of critical function indispensable in the modern advanced litho machine fast.
At present, utilize the Changing Pattern between FOCAL test badge imaging horizontal level and the silicon chip defocusing amount to detect the picture element parameter, be mainly used in the detection of elementary axial picture element parameter.In this technology, at first a plurality of measurement markers on the mask plate are exposed on silicon chip in different defocusing amounts position, use the image space of alignment system test badge then, utilize image space to calculate the alignment offset amount, obtain elementary axial picture element parameter after at last the alignment offset amount being analyzed.
For the FOCAL technology, expect higher precision axis to the picture element parameter, need the fine structure line thickness of FOCAL mark can be as far as possible little, the out of focus step-length between different exposure field is also enough little simultaneously, will increase exposure number of fields and Measuring Time like this; Very little line thickness will make the Changing Pattern between FOCAL test badge imaging horizontal level and the silicon chip defocusing amount be limited in a smaller focal depth range simultaneously, make apart from the influence of the mark in optimal focal plane a lot of exposure field far away with the nonfertilization fine texture.And opposite, if the fine structure line thickness of FOCAL mark is bigger, influence will become not obvious to defocusing amount to FOCAL test badge imaging horizontal level, therefore can reduce the measuring accuracy of axial picture element parameter.
In addition, when the live width of the fine structure of FOCAL mark is very little, it is in when exposing under the out-of-focus appearance, corresponding more significantly change can take place because of varying in size of defocusing amount in the live width of the fine structure of this FOCAL mark, thereby the centre of gravity place of mark is changed, produce alignment offset amount (as shown in Figure 1); But when defocusing amount exceeds mark out of focus sensitive range [F ,+F], out of focus will no longer influence the markers align position.For specific litho machine system, mark out of focus sensitive range is directly to be determined by mark fine structure live width size, and live width is more little, and sensitive range is also more little.The FOCAL mark fine structure of broad lines can obtain bigger litho machine optimal focal plane deviation range, can obtain more accurate optimal focal plane position than the FOCAL mark fine structure of hachure in less depth of focus.
Summary of the invention
Fundamental purpose of the present invention is to provide a kind of photo-etching machine imaging quality measuring method, it utilizes the FOCAL mark (being called for short the DFOCAL mark) of dual fine structure, can carry out high precision, measure fast the axial picture element parameter of litho machine of the image quality that is used to estimate litho machine, can overcome the shortcoming that measurement range and measuring accuracy can not be taken into account simultaneously in the prior art.
For reaching above-mentioned purpose, the invention provides a kind of photo-etching machine imaging quality measuring method, it comprises following steps:
Described DFOCAL mark comprises thick lines fine structure and hachure fine structure; The lines of the hachure fine structure that the lines of this thick lines fine structure compare are wide more than 3 times;
After step 2, silicon chip develop,, utilize alignment system to carry out systematic sampling and measure, obtain each DFOCAL markers align position in n/m the exposure field, obtain the imaging alignment offset amount of n/m DFOCAL mark thus for a formed n exposure field;
Described m is expressed as the sampling interval that systematic sampling is measured;
The pinpointed focus approximate location of each DFOCAL gauge point in step 3, the imaging alignment offset amount of utilizing the DFOCAL test badge that obtains and the Changing Pattern rough calculation exposure field between the silicon chip defocusing amount:
Changing Pattern described in this step 3 is: because axially the big young pathbreaker of the alignment offset amount that causes of picture element changes with the variation of out of focus, be embodied in: when silicon chip exposes on best focal plane, system resolution is stronger, the fine structure of DFOCAL mark can be transferred on the silicon chip fully, and this moment, the alignment offset amount was bigger; And when exposing on the plane of silicon chip in out of focus, system resolution is relatively poor, and the fine structure of DFOCAL mark can not be transferred on the silicon chip by undistorted, causes the side-play amount of optical alignment less.
This step 3 specifically comprises: at the exposed portion of thick lines fine structure on silicon chip of DFOCAL mark, utilize the alignment offset amount under n/m the defocusing amount that sampling measurement obtains, carry out curve fitting 2 times, when obtaining curve and obtaining maximal value, defocusing amount when being alignment offset amount maximum is the pinpointed focus approximate location;
The DFOCAL markers align position of correspondence in nearest n/m of each DFOCAL gauge point pinpointed focus approximate location in the step 4, measuring distance exposure field obtains the corresponding imaging alignment offset amount of this each DFOCAL mark thus;
DFOCAL markers align position described in the step 4, near the mark position of exposure image when being in the pinpointed focus for the DFOCAL mark;
This step 5 specifically comprises: at the exposed portion of hachure fine structure on silicon chip of DFOCAL mark, utilize the alignment offset amount under each defocusing amount that measures in the step 4, carry out curve fitting 2 times, when obtaining curve and obtaining maximal value, defocusing amount when being alignment offset amount maximum is optimal focus position;
The axial picture element parameter of step 6, calculating litho machine: focal plane, the curvature of field, astigmatism, image planes inclination etc.
Photo-etching machine imaging quality measuring method provided by the invention has the following advantages:
1, the inventive method adopts the DFOCAL mark as alignment mark: because this DFOCAL mark ectomesoderm fine structure lines broad, so be used for the pinpointed focus approximate location of each point in the rough measure field, and its internal layer fine structure line thickness is very little, is used for accurately measuring near the pinpointed focus approximate location of coarse localization the optimal focus position of this point;
2, the inventive method is an each point optimal focus position in the field that obtains under all very little condition of fine structure live width and out of focus step-length, so can obtain higher measuring accuracy;
3, the inventive method is in test process, and each time shutter of silicon chip is shorter, and the markers align Measuring Time is longer, and the present invention has reduced Measuring Time only to having carried out locating tab assembly internal labeling position, sub-fraction field.
Description of drawings
Fig. 1 is the synoptic diagram of the out of focus described in the background technology to the influence of FOCAL markers align position;
Fig. 2 is the measuring system synoptic diagram of photo-etching machine imaging quality measuring method of the present invention;
Fig. 3 is the DFOCAL mark in the embodiment of the invention 1 and the synoptic diagram of dual fine structure thereof;
Fig. 4 is the distribution schematic diagram that DFOCAL is marked at the exposure field on the silicon chip in the embodiment of the invention 1;
Fig. 5 is the curve map that DFOCAL mark internal layer fine structure imaging size changes with out of focus in the embodiment of the invention 1;
Fig. 6 is the curve map that the outer fine structure imaging size of DFOCAL mark changes with out of focus in the embodiment of the invention 1;
Fig. 7 is marked as graph of relation between picture dutycycle and the defocusing amount according to what the result of Fig. 5 and Fig. 6 calculated in the embodiment of the invention 1;
Fig. 8 is the dual fine structure synoptic diagram of the DFOCAL mark in the embodiment of the invention 2;
Fig. 9 is the graph of relation between mark imaging dutycycle and the defocusing amount in the embodiment of the invention 2.
Embodiment
Below in conjunction with Fig. 2-Fig. 9, describe preferred implementation of the present invention in detail:
As shown in Figure 2, the employed measuring system of the inventive method comprises: the light source 101 that produces projected light beam; Be used to adjust the light distribution of the light beam that described light source sends and the illuminator 102 of partial coherence factor; The imaging optical system 103 that mask pattern imaging and its numerical aperture can be able to be regulated; Can carry described mask R and pinpoint mask platform 104; Can carry silicon chip W and pinpoint work stage 105; And the alignment system 106 that can be used for aiming at the silicon chip position.
In the present embodiment, adopt DFOCAL mark as shown in Figure 3, this DFOCAL mark comprises outer fine structure and internal layer fine structure; The wide 1.5um of the lines of this skin fine structure, the wide 200nm of the lines of this internal layer fine structure.
The step of photo-etching machine imaging quality measuring method of the present invention is as follows:
The deep ultraviolet laser that step 1, light source 101 send shines on the mask R that is carved with the DFOCAL mark through illuminator 102, this mask R goes up 65 the DFOCAL marks that evenly distribute, mask R optionally sees through a part of light, this part light is through imaging optical system 103, under 60 defocusing amounts in the 3um scope pattern exposure on the mask R is imaged onto on the different piece of silicon chip W, as shown in Figure 4,12 fields of exposure in this scope, divide equally 5 layers of 65 the DFOCAL mark that evenly distributes in each exposure field, the distance of each interlayer axialy offset 400um;
The approximate location of pinpointed focus separately that step 3, the imaging alignment offset amount of utilizing the DFOCAL test badge that obtains and the Changing Pattern between the silicon chip defocusing amount come to go out than rough calculation 65 points in the exposure field, this step is embodied in: at the exposed portion of thick lines fine structure on silicon chip of DFOCAL mark, utilize the alignment offset amount under 12 defocusing amounts of each mark, carry out curve fitting 2 times, when obtaining curve and obtaining maximal value, be the defocusing amount of alignment offset amount when maximum, be the pinpointed focus approximate location of this mark loca;
The nearest interior corresponding DFOCAL markers align position of 12 layers of the approximate location of pinpointed focus separately of 65 gauge points obtains corresponding imaging alignment offset amount in step 4, the measuring distance exposure field;
In the present embodiment, combine 2 characteristics described below: the one, utilize the thick lines of DFOCAL mark fine structure to determine mark pinpointed focus approximate location, the 2nd, utilize the accurate measurement markers pinpointed focus of the hachure exact position of DFOCAL mark fine structure.
As shown in Figure 5, the wide 200nm of hachure of the fine structure of the DFOCAL mark in the present embodiment, this DFOCAL mark 200nm fine structure imaging critical size is the prolith simulation curve with the out of focus change curve, among the figure as can be seen, at out of focus (0.4um, 0.4um) scope outside, when promptly being in outside the out of focus sensitive range shown in Fig. 1, the DFOCAL mark of 200nm fine structure can not imaging.
As shown in Figure 6, the wide 1.5um of thick lines of the fine structure of the DFOCAL mark in the present embodiment, this DFOCAL mark 1.5um fine structure imaging critical size is the prolith simulation curve with the out of focus change curve, among the figure as can be seen, at out of focus (1.5um, 1.5um) outside the scope, when promptly being in outside the out of focus sensitive range shown in Fig. 1, the DFOCAL mark of 1.5um fine structure can not imaging.
Simulation result according to Fig. 5 and Fig. 6, can calculate DFOCAL is marked as the relation between dutycycle and the defocusing amount, concrete computing method are: the CD/3000nm of the CD/400nm+1500nm lines imaging of 200nm lines imaging, concrete result of calculation as shown in Figure 7, this result is corresponding to the relation between markers align position and the defocusing amount.
In the present embodiment, adopt DFOCAL mark as shown in Figure 8, this DFOCAL mark comprises outer fine structure and internal layer fine structure; The wide 1.2um of the lines of this skin fine structure, the wide 150nm of the lines of this internal layer fine structure.
The step of photo-etching machine imaging quality measuring method of the present invention is identical with embodiment 1, and difference only is in the step 1, present embodiment be under 40 defocusing amounts in the 2um scope with the mask pattern exposure image on the different piece of silicon chip W.
Simultaneously, DFOCAL is marked as the relation between picture dutycycle and the defocusing amount in the present embodiment, and concrete computing method are: the CD/2400nm of the CD/300nm+1200nm lines imaging of 150nm lines imaging, concrete result of calculation as shown in Figure 9.
Comprehensively above-mentioned, can be according to different testing requirements, concrete parameters such as the thick lines of the fine structure by changing the DFOCAL mark and the width of hachure and out of focus scope better realize test purpose, when the fine structure line thickness more hour, test specification also reduces, but can improve the precision of test relatively.
Photo-etching machine imaging quality measuring method provided by the invention has the following advantages:
1, the inventive method adopts the DFOCAL mark as alignment mark: because these DFOCAL mark ectomesoderm fine structure lines are wider, so be used for the pinpointed focus approximate location of each point in the rough measure field, and its internal layer fine structure line thickness is very little, is used for accurately measuring near the pinpointed focus approximate location of coarse localization the optimal focus position of this point;
2, the inventive method is each point optimal focus position in the field that fine structure live width and out of focus step-length are all obtained under the very little condition, so can obtain higher measuring accuracy;
3, the inventive method is in test process, and each time for exposure of silicon chip is shorter, and mark aligning Measuring Time is longer, and the present invention has reduced Measuring Time only to having carried out locating tab assembly internal labeling position, sub-fraction field.
Claims (3)
1. a photo-etching machine imaging quality measuring method is characterized in that, comprises following steps:
Step 1, under litho machine n different defocusing amounts, the pattern exposure of the DFOCAL mark that is carved with evenly distributing on the mask forms n exposure field on the silicon chip different piece, described DFOCAL mark is made up of thick lines fine structure and hachure fine structure;
After step 2, silicon chip develop, for a formed n exposure field, utilizing alignment system to carry out systematic sampling measures, obtain each DFOCAL markers align position in n/m the exposure field, obtain the imaging alignment offset amount of DFOCAL mark thus, this m represents the sampling interval that systematic sampling is measured;
The pinpointed focus approximate location of each DFOCAL gauge point in step 3, the imaging alignment offset amount of utilizing the DFOCAL mark that obtains and the Changing Pattern rough calculation exposure field between the silicon chip defocusing amount, described step 3 specifically comprises: at the exposed portion of thick lines fine structure on silicon chip of DFOCAL mark, utilize the alignment offset amount under n/m the defocusing amount that sampling measurement obtains, carry out curve fitting 2 times, when obtaining curve and obtaining maximal value, promptly the defocusing amount when the alignment offset amount is maximum is exactly the pinpointed focus approximate location;
The DFOCAL markers align position of correspondence in nearest n/m of each DFOCAL gauge point pinpointed focus approximate location in the step 4, measuring distance exposure field obtains the corresponding imaging alignment offset amount of this each DFOCAL mark thus;
Step 5, utilize markers align position measured in the step 4, accurately simulate the optimal focus position of each DFOCAL gauge point, described step 5 specifically comprises: at the exposed portion of hachure fine structure on silicon chip of DFOCAL mark, utilize the alignment offset amount under each defocusing amount that step 4 measures, carry out curve fitting 2 times, when obtaining curve and obtaining maximal value, promptly the defocusing amount when the alignment offset amount is maximum is exactly an optimal focus position;
The axial picture element parameter of step 6, calculating litho machine: focal plane, the curvature of field, astigmatism, image planes tilt.
2. photo-etching machine imaging quality measuring method as claimed in claim 1 is characterized in that, the line thickness of described thick lines fine structure is wideer more than 3 times than the line thickness of hachure fine structure.
3. photo-etching machine imaging quality measuring method as claimed in claim 1 is characterized in that, in the step 4, and the described DFOCAL markers align position that records, near the mark position of exposure image when being in the pinpointed focus for the DFOCAL mark.
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| CN102402139A (en) * | 2010-09-14 | 2012-04-04 | 上海微电子装备有限公司 | Method for determining optimal height of photoelectric sensor of work piece table |
| CN102495533B (en) * | 2011-11-24 | 2015-08-26 | 上海华虹宏力半导体制造有限公司 | Detect the method and system of exposure sources focal position |
| CN106569390B (en) * | 2015-10-08 | 2019-01-18 | 上海微电子装备（集团）股份有限公司 | A kind of projection aligner and method |
| US10962892B2 (en) * | 2018-09-28 | 2021-03-30 | Taiwan Semiconductor Manufacturing Co., Ltd. | Lithography process monitoring method |
| DE102019100154B4 (en) | 2018-09-28 | 2020-11-05 | Taiwan Semiconductor Manufacturing Co. Ltd. | Method for performing a lithography process and lithography process monitoring method |
| CN111401673A (en) * | 2019-09-16 | 2020-07-10 | 国营武汉新宇机器厂 | Dot matrix engraving effect evaluation method of laser engraving machine |
| CN110880469B (en) * | 2019-11-26 | 2022-04-29 | 中国科学院微电子研究所 | Optimization method of silicon wafer alignment mark layout |
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| US5674650A (en) * | 1994-08-02 | 1997-10-07 | U.S. Philips Corporation | Method of repetitively imaging a mask pattern on a substrate, and apparatus for performing the method |
| CN1601385A (en) * | 2004-10-18 | 2005-03-30 | 上海微电子装备有限公司 | Method of determining range of exposure dose in tech of picture quality detection of aligner |
| CN1673871A (en) * | 2005-04-21 | 2005-09-28 | 中国科学院上海光学精密机械研究所 | Method for detecting imaging quality of photoetching machine |
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| US5674650A (en) * | 1994-08-02 | 1997-10-07 | U.S. Philips Corporation | Method of repetitively imaging a mask pattern on a substrate, and apparatus for performing the method |
| CN1601385A (en) * | 2004-10-18 | 2005-03-30 | 上海微电子装备有限公司 | Method of determining range of exposure dose in tech of picture quality detection of aligner |
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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. |