Fabrication of silicon strip detectors using a step-and-repeat lithography system

The author describes the use of a step-and-repeat lithography system (stepper) for the fabrication of silicon strip detectors. Although the field size of the stepper is only 20 mm in diameter, much larger detectors have been fabricated by printing a repetitive strip detector pattern in a step-and-repeat fashion. The basic unit cell is 7 mm in length. The stepper employs a laser interferometer for stage placement, and the resulting high precision allows one to accurately place the repetitive patterns on the wafer. A small overlap between the patterns ensures a continuous strip. A detector consisting of 512 strips on a 50 mu m pitch has been fabricated using this technique. The dimensions of the detector are 6.3 cm by 2.56 cm. Yields of over 99% have been achieved, where yield is defined as the percentage of strips with reverse leakage current below 1 nA.<>