2. Etch Process Input and Output Parameters

3. Process Modeling how to use input parameters to achieve desired output parameters Process Model Quality parameter1 Quality parameter2 Control parameter1 Control parameter2 Control parameter3 InputsProcess Outputs Relation between inputs and outputs

4. Input Parameters Pressure RF power Gas Flow Rates Temperature Gap distance

5. Output Parameters Etch rate Uniformity Vertical profile Selectivity

6. Etch Rate How fast the film material is etched per minute. Unit: nm/min

7. Uniformity Center vs. Edge Etch rate is not the same everywhere. Desire uniformity, all features finish etching at the same time, else some will be under-retched while others are already over-etcher. Center to edge difference: caused by electric field strength difference, gas flow rate difference. Etcher rate sampled at sites across the wafer. Stand deviation is used to measure variation. The larger the variation the worse the uniformity.

8. Uniformity small vs. large features Small feature vs. large feature difference; a deep and narrow feature can be difficult to etch—slower than wider features.

9. Vertical Profile Isotropic vs. anisotropic: isotropic means same etch rate in all directions. higher density circuits make deep and narrow features desirable. Anisotropic Isotropic

10. Selectivity Selectivity: etching only the target material not others. For example, if my etch rate for SiO2 is much larger than SiN4, then it will only etch the SiO2 film not the layer underneath. SiO2 Si3N4—etch stop layer