Improved Process for Manufacture of Radiation Hard N-Channel JFETs for Detector Electronics

Abstract

Input transistors for SSC cryogenic calorimer preamplifiers must have very good low noise performance while remaining tolerant to the high radiation found inside the calorimeter near the interaction region. N-channel Junction Field Effect Transistors (JFETs) combine the best features of low noise operation and high tolerance to radiation to a greater extent than bipolar or MOS transistors. New designs and manufacturing methods are described which reduce the degradation of JFET noise performance due to neutrons. Two basic premises governed the choice of design and manufacturing methods. First, the JFET was designed with smaller features and spacings in order to minimize silicon in the active volume of the transistor. This reduces the interaction cross section with neutron radiation. Second, reduced feature size should increase the transconductance of the transistor, thereby improving noise performance.