Methods for minimizing as-deposited stress in tungsten silicide films

A method for minimizing unwanted tungsten-rich deposition on a substrate in a CVD reactor chamber having a gas injection and flow control subsystem providing tungsten hexafluoride gas through a first shut-off valve and flow controller remote from the reactor chamber, and connected by a substantially elongated gas supply manifold to the CVD reactor chamber such that substantial manifold wall surface area is exposed to the reactor chamber, the method comprising steps of:

• (a) providing a second shut-off valve in the substantially-elongated gas supply manifold;
• and
• (b) closing the second shut-off valve for substantially all of the time between the end of deposition steps for one wafer and the beginning of deposition steps on another wafer, thereby isolating the CVD reactor chamber from the substantial wall surface area in the area between the first and second shut-off valves, and preventing outgasing of tungsten hexafluoride gas from the isolated wall surface area into the reactor chamber.

A method for depositing a tungsten silicide film on a substrate in a CVD reactor chamber, comprising steps of:

• (a) introducing WF.sub.6 and reducer gas into the reactor chamber for a first period of time at a first ratio of reducer gas to WF.sub.6 to accomplish deposition of the tungsten silicide film on the substrate;
• and
• (b) establishing a second ratio of reducer gas to WF.sub.6 higher than the first ratio for a second period of time no more than ten percent of the first period of time, ensuring thereby a silicon-rich layer on the tungsten silicide film.