Use Of Si-Ge Alloys For Thin Resistors
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
In lightly doped polysilicon needed for high resistance structures, the resistivity principally arises from majority carrier barriers which occur at the grain boundaries. The resistivity takes the form, p approximately e/E/b//kT/, where E(b) is energy barrier created by band bending at the boundries. The temperature coefficient of resistance, (TCR), thus has a strong (exponential) dependence on E(b), and even a relatively small reduction in E(b) could substantially reduce the TCR. Diminishing the magnitude and consequently the influence of E will result in resistivities which are more controllable; i.e., resistivities will depend more on intentional doping and less on grain size. The quantity E(b) is related to the band gap E(g), such that lowering E(g) will also lower E(b).