摘要
平面间平行度的测量方法在光学检测和加工中有着广泛的需求。激光干涉测量技术用于平行度的检测已经发展地非常成熟，具有测量精度高和非接触性等优点，能够很好地满足大多情况下对两平面平行度的检测要求。但是，在一些需要高精度平行度检测的场合，如近场纳米光刻中，对平面间平行度的检测精度要求高达微弧度量级，并且平行度的精度能否达到将直接关系到纳米光刻的加工精度。在诸如此类的应用中。常用的激光干涉测量技术由于受到视场内条纹读数的限制，无法达到微弧度的测量精度。针对该问题，本论文引入移相干涉测量方法来解决这个难题。移相干涉技术的基本原理是在干涉仪的两相干光之间引入有序的位相差，当参考光光强或位相发生变化时，干涉条纹的位置也做出相应的移动，而通过条纹位置的移动量的变化，则可以反演出平面间平行度的变化。本文主要建立和发展了移相干涉技术精密测量平面间平行度的方法，使1mm口径的平面间平行度的检测精度达到几个微弧度的量级，解决了现有方法无法达到纳米光刻中对平行度检测的高精度需求；同时，发展和优化了相移反演算法，以最大限度地消除干涉仪的测量误差，提高条纹分析的精确度，达到消除移相干涉测试方法的总体误差，使得测量结果更加地可靠。
一直以来，由于光学衍射极限的存在，使得光学干涉方法在检测两物体间绝对间距精度无法达到纳米尺度，从而极大地限制了该检测方法的应用范围。为了将光学干涉方法在间距方面的检测精度提高到纳米尺度，许多科研工作者做出了大量的工作，但是目前尽管检测精度可以达到纳米量级，但检测范围却一般都被限定在微米量级。表面等离子共振(SPR)传感器具有极高的敏感度，其在临界角附近对于角度变化的敏感度可达1200，因此可以被用来实现角度和距离的高精度检测。一些学者提出的方法中，利用SPR角度传感器可以实现纳米精度的间距检测，其检测最小间距可以达到126nm。但是对于小于100nm以下的间距检测，这些方法将不能适用。纳米光刻技术中往往要求实现100nm以下的间距的精确定位，其对准的精度直接关系到纳米器件的加工精度，因此，纳米尺度的检测具有十分重要的现实意义和实用价值。我们提出一种基于物理光学原理结合SPR角度传感器来检测纳米间距的方法。该方法利用物理光学的原理，当反射镜与透镜后焦面没有重合而存在一极小位移时，反射光束会产生一个角度偏离，并且其偏移量与反射镜的离焦位移有一定的比例关系；同时在满足SPR的情况下，光束P分量和S分量的位相变化与入射光角度的变化成一定的比例关系。因此，通过检测位相变化可以实现纳米间距的测量。本文提出的纳米精度定位检测方法，利用SPR传感器的高敏感度，将纳米间距的检测分辨率提高到了1nm的精度，而最小检测距离达到了10nm以下。本文所发展和建立的纳米精度定位检测方法，为后续的近场纳米光刻技术在基片和模板的高精度定位和检测方面打下了良好的技术积累。
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.
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