Localization of sub-100-nm particles on wafers with solid state detector arrays

Scatterometry is a powerful and fast measurement method to measure surfaces and its properties. The analysis of the backscattered light from a coherently illuminated surface enables the determination of various integral surface topography constants, surface defects and surface material properties. This paper is a continuation a previous paper (Proc. SPIE Vol. 4779, pp. 72-82). In this paper localization of sub- 100nm polystyrene particles on wafers with solid state detector arrays will be considered. In first part of the paper the angle resolved light scatter sensor system LARISSA (Large Dynamic Range Intelligent Scatter Sensor Approach) will be reviewed. The system consists of an elliptical mirror optics and a CMOS photodiode detector array. The elliptical mirror optics enables the angle resolved and the integral scatter measurement in a solid angle of π sr. The CMOS photodiode detector array consists of 32k single detector elements which are aligned in a circular form. Each single detector element is calibrated in a dynamic range of 7 decades of intensity. The ARS system can be used to realize a scatter measurements without moving parts which is a significant advantage in speed over conventional goniometer setups. The integral scatter measurement mode of the ARS sensor LARISSA enables the detections of very small scatter sources. In the second part of the paper localization of sub- 100nm polystyrene particles on wafers will be considered. The integral scatter measurement mode will be described in detail and measurements at a wavelength of 488nm will be presented. The measurement results will be analyzed by using scatter simulations which are based on discrete sources method. The comparison of measurement and simulation enables the determination of the detection limits of the sensor system and the derivation of design hints for particle scanner systems. Finally the results will be summarized and further development will be outlined.