Correlation between electrostatic scan pattern and local dose nonuniformities

After a description of the principles of electrostatic scanning and the typical scan configuration in standard medium current implanters with their possible uniformity errors, optimum scan conditions are calculated. To realize these calculations crystal controlled scanner preamplifiers with significantly increased scan frequencies were built. The uniformity tests were carried out by a C-V technique, with a diode to diode distance of 0.1 mm. In contrast to remarkable nonuniformities with random frequency scanners, the results showed that a uniformity of +-1.05% can be achieved over a 3' wafer without any local nonuniformity. (orig.)