Measurement Uncertainity and Noise in Nanometrology
James E. Potzick
The measurement of feature sizes on integrated circuit photomasks and wafers is an economically important and technically challenging application of nanometrology. The displacement measuring laser heterodyne interferometer is a popular tool in such applications, but measurement errors which may be unimportant in other applications can become significant in measuring such small objects. Measurment uncertainty resulting from interferometer resolution and nonlinearity can be reduced by oversampling and averaging multiple measurements, but only if there is some noise on the measurand. In this paper the optimum noise level is determined and the consequent improvement in measurement uncertainty calculated.
Laser Metrology for Precision Measurement and Inspection in Industry