Laser-recrystallized polycrystalline silicon resistors for integrated circuit applications

Abstract

The influence of grain boundaries on the electrical properties of laser-recrystallized polycrystalline silicon films, with a typical grain size 1×20 μm2 and doping concentration between 1016 and 1020 cm−3, has been investigated. Over a wide range of doping concentration, sheet resistance and its temperature dependence are found to be very close to the values expected for single crystal material. Deviations occur at low doping levels and are related to the average grain size perpendicular to the current flow. The standard deviation and laser power dependence of sheet resistance R⧠ are strongly correlated to the influence of grain boundaries, as measured by the deviation of R⧠ from the single crystal value. The main sources of resistor nonlinearity are substrate field effects and the dependence of grain boundary potential barriers on applied bias. At doping concentrations ≳1018 cm−3 very linear resistors are obtained reproducibly. Resistance ratios can be controlled to better than 1% and temperature coefficients ≲10−4/K can be achieved by proper choice of doping concentration.