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Study On The Positioning Measurement Method With Nanometer Resolution

Posted on:2014-11-26Degree:DoctorType:Dissertation
Country:ChinaCandidate:E W WangFull Text:PDF
GTID:1268330398996820Subject:Optics
Abstract/Summary:PDF Full Text Request
The measurement of parallel between two flat planes has wide application inoptical testing and manufacture. The conventional laser interference measuringtechnique is well developed to detect the parallel between two planes, and it’saccuracy is as high as0.3mrad. In general, the laser interefering method could meetmost applications with the advantages of high precision and non-contacting. However,with the trend to develop optoelectronic devices to be more miniaturizable and highlyintegrated, the aligent between two planes needs to more accurate. Such as innanolithography, the aligent accuracy between two planes is required to be as high as1m rad. The precision of the aligent between two planes will directly affect theaccuracy of the nanolithography. However, for laser interfering method, the precisionis limited by the intereference pattern in field of view. To overcome this limitation, anew method, i.e. the phase-shifting interferential method, is proposed for themeasurement of parallel between two planes. The basic principle of the proposedmethod is to introduce an ordered displacement between two coherent light beams inthe interferometer. The position of the interference pattern could be changedaccordingly, while the intensity or phase of the reference light beam is changed. Thenew method could solve the problem of perfect aligent in nanometer photolithography.And make sure the precision of aligent could reach microradian scale when the size oftested planes is1mm. In addition, the algorithm of fringe analysis and the method of eliminating measurement error are studied to eliminate the measuring error and obtainmore reliable results.Optical diffraction limit is well-known to limit the resolution of the opticalmeasuring methods based on laser intereference. Up to now, the optical interferencemethod is still the regular method to measure the absolute distance between twoisolated planes. The diffraction limit still limits the applications of opticalmeasurements. A number of workers made further efforts to extend the opticalinterference method to the nanometer-scale gap measurements. However, the methodcan only work on the range of micron magnitude, and the resolution can reach ananometer scale. The surface plasmon resonance (SPR) sensor has high sensitivity,and the sensiticity for angle change around critical angle can reanch a value of1200.It can be used for detecting angular and displacement with high precision. Somemethod had been proposed to detect the nanometer spacing, and the measuredsmallest air gap is about126nm. However, those methods can not work when the airgap is smaller than100nm. In nanolithography, the range of nanogap which can bedetected and adjusted is normally smaller than100nm. The precision of the nanogapdetecting between two planes will directly determine the accuracy of thenanolithography. Hence, the detecting of nanometer sacle has important practicalsignificance and practical value. In this thesis, we extended the resolution of thenanogap measuring method down to nanometer scale, i.e.<100nm. In physical optics,if there is a small displacement between the reflecting plane and the focused plane ofthe objective lens, the reflected beam will have an angle deviation, which isproportional to this displacement. In addition, under SPR condition, the phasedifference between p-and s-polarizations of the beam is proportional to the anglechange of the incident beam as well. Therefore, the nanometer spacing can bemeasured by detecting the phase change between p-and s-polarizations of the beam.The resolution of this method can be as small as1nm due to the high sensitivity ofSPR sensor. We measured the phase difference instead of the reflectivity, and thenumerical simulation shows that the smallest gap can be obtained is smaller than10 nm. The nanoscale positioning detecting method developed in this thesis will be greathelpful for the following near-filed nanolithography.
Keywords/Search Tags:optic measurement, phase difference, PZT phase-shifting, nanometerspacing, SPR angle sensor, resonance angle
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