Abstract: A homogeneous marker is formed, possibly by the adsorption of trace amounts of an ambient material such as carbon monoxide gas, at a surface of a deposited material when the plasma in momentarily interrupted during plasma enhanced chemical vapor deposition or other deposition processes involving the presence of a plasma. When the deposited material is etched, the resulting crystal dislocations or adsorbed gas is detected as a marker by optical emission spectroscopy techniques. The accuracy of an end point determination of the etching process can be increased by providing a sequence of such markers within the bulk or volume of the deposited material. The markers, being merely an interface such as a slight crystal dislocation in otherwise homogeneous material, do not affect the electrical, chemical or optical properties of the remainder of the predetermined deposited material and thus the homogeneity of the deposited material is not significantly affected.

Abstract: A back end of the line dry etch method is disclosed. Etching of a mask oxide and temporary (sacrificial) silicon mandrel occurs following the formation of gate stacks and tungsten studs. The mask oxide is etched selectively to tungsten and silicon through the use of a polymerizing oxide etch. The silicon is etched selectively to both silicon nitride, silicon oxide, and tungsten. The process removes the silicon mandrel and associated silicon residual stringers by removing backside helium cooling, while using HBr as the single species etchant, and by adjusting the duration, the pressure, and the electrode gaps during the silicon etch process. The silicon may be undoped polysilicon, doped polysilicon, or single crystal silicon.