Jaerisch W, Makosch G
Appl Opt. 1973 Jul 1;12(7):1552-7. doi: 10.1364/AO.12.001552.
A precise nondestructive optical contour mapping method with adjustable sensitivity for noncontact testing of surface deformations up to 30 microm/cm is described. The method employs an optical grating that is placed in front of the test surface. Illumination of the grating by a monochromatic plane wave generates an interference pattern between the beam components of two different diffraction orders. Reflection at the test surface and superposition with the fixed grating generate a fringe pattern that resembles the surface contours of the test object. This fringe pattern consists of a superposition of an interference line system and a moiré line system. Whereas the distance between two adjacent contour lines of the interference pattern corresponds to a surface deformation of a half-wavelength of the illuminating light the distance between two lines of the moiré system is determined by the grid constant and the direction of the grid illumination. Therefore, the scale of measurement can be chosen according to the problem. Applications for surface flatness testing of semiconductor wafers and photomasks are presented.
描述了一种精确的无损光学轮廓映射方法，该方法灵敏度可调，用于对高达30微米/厘米的表面变形进行非接触测试。该方法采用放置在测试表面前方的光栅。用单色平面波照射光栅会在两个不同衍射级的光束分量之间产生干涉图样。在测试表面的反射以及与固定光栅的叠加会产生类似于测试对象表面轮廓的条纹图样。该条纹图样由干涉线系统和莫尔线系统叠加而成。干涉图样中相邻两条轮廓线之间的距离对应于照明光半波长的表面变形，而莫尔系统中两条线之间的距离由网格常数和网格照明方向决定。因此，可以根据问题选择测量比例。还介绍了该方法在半导体晶圆和光掩模表面平整度测试中的应用。
