Method of preparing high-temperature-stable thin-film resistors

DETAILED DESCRIPTION The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 1.
A chemical vapor deposition method for the preparation of high temperature stable thin film resistors having a predetermined temperature coefficient of resistance (TCR) and bulk resistivity comprising: placing a substrate having an electrically insulative surface in a reactor; flowing a reducing carrier gas through the reactor at a pressure of about 0.
1 to 10 Torr to remove the ambient gas; heating the substrate to a controlled temperature between 500.
degree.
C.
and 900.
degree.
C.
; introducing a reactant gas into the flowing carrier gas, the reactant gas comprising a mixture of at least one decomposable compound of tungsten and at least one decomposable compound of silicon in a controlled ratio; and contacting the flowing reactor and carrier gases with the heated surface of the substrate to decompose the reactant gas to deposit a thin film of tungsten silicide on the substrate, the controlled ratio of tungsten to silicon in the reactant gas being in part determinative of the tungsten to silicon ratio in the thin film which is determinative of the bulk resistivity and TCR of the film, and the controlled temperature of the substrate being determinative of the crystallinity of the film which is determinative of the TCR of the film, whereby for a tungsten to silicon ratio in the range of 1:3 to 3:1 a low substrate temperature will produce an essentially amorphous film having a TCR nearly equal to 0 ppm/.
degree.
C.
and increasing the substrate temperature will produce a more crystalline film having a more positive TCR, and whereby for tungsten to silicon ratios outside the limits of 1:3 to 3:1 the tungsten to silicon ratio will also affect the value of the TCR.
2.
The method of claim 1 wherein the ratio of tungsten to silicon in the thin film is controlled within the range of 3:1 to 1:3 whereby as the ratio approaches 3:1 the bulk resistivity approaches about 100