Analysis Of Environmental Disturbance Effects On High Pricision Figure Measurement

The demands of semiconductor lithography optics provide a significant driver for continuous improvement of optical manufacturing and metrology. At present, the 193nm lithography requires optical surfaces to 1~2nm rms or more accuracy. For such accuracy to be achieved, highly accurate figure metrology is essential, because the optics are polished according to the error ditribution which is measured from an interferometer. Repeatability and reproducabiligy of a measurement are essential to low measurement uncertainty. The enviromental disturbance will introduce large radomly chaning errors, to reduce the enviromental disturbance effects, we should control the enviroment to some level. For this purpose, this thesis analyzes the enviromental disturbance effects to optical figure measurements and evaluates the figure error caused by envrioment. The major works of this thesis are summarized as follows:(1) Analysed the thermal deformation of the lens with simulation models. According to temperature distribution characteristics in a real laboratory, the ununiformity in space, unstability with time of air temperature and because of insufficiently stablization of lens itself, will cause figure deformation error. Then the goals of enviromet control are provided from the aspects of guaranting enough mechanical stability. (2) Aiming at the influence of environmental condition on the optical cavity between the refrence surface and test surface, the flow simulational analysis model is established and the temerature, pressure distributions of the optical cavity under different flow state when there are heat source/heat sink exsting in the room is analysed. At the same time the raytracing model is established to calculate the resulting wavefront deviation. The feasibility of reducing the nonuniform distribution temperature of the optical cavity and depressing the resulting wavefront deviation by increasing flow speed is analyzed, too.(3) According to practical figure measurement process, the uncertainty matrix and wavefront repeatability are introduced to describe the figure mesurement uncertainty caused by environment turbulence in a single measurement. The distribution of uncertainty after many mesurements being averaged is analyzed. Measurement uncertainties under different environment conditions are compared to provide a reference for improvement of environment conditions. (4) A high precise air temperature testing system is established. The error sources of a temperature sensor are analyzed. The feature of a Silicone-Bead thermistor probe Fluke 5611s in a narrow temperature range are tested to verify the measurement accuracy of the probe. Thus, we have assured the high accurate measurement of the air temperature in a highly controlled laboratory environment.