Sweet spot is the informal name for the overlapping window where all requirements are met together, for example etch rate high enough, uniformity under 2 percent and selectivity over 20. Engineers find it by overlaying contour plots from a response surface model and shading out where each response fails. A big sweet spot means a forgiving process; a tiny one means tight control on every knob.
Overlay plot shows the sweet spot is tiny, about 5 watts by 2 millitorr. That recipe won't survive tool-to-tool matching.
Also heard as
- process window
- operating window
Related terms
RSM
Response surface methodology: sequential experiments that fit curved models to find the settings that optimize a response.
Robust
Describes a product or process whose output stays on target despite variation in noise factors that cannot be controlled.
Knob
Any adjustable process parameter on a tool, such as RF power, pressure, gas flow, temperature or time.
DOE
Design of experiments: planning a set of runs that vary several factors at once so their effects can be separated.