In an etch process, there is a finite amount of purely chemical etching without any ion bombardment (i.e., spontaneous chemical etching).
In addition, ion bom-bardment greatly increases the etch rate by facilitating the breaking up of the etch precursor.
At high ion flux the etch rate saturates.
No etching occurs when there ts only ion bombardment with no chemical component.
a. Write a generalized etch rate equation that can describe this behavior.
b. Sketch an etch rate versus ion flux curve for this process for some nonzero chemical flux.
c. Sketch what the etch profile might look like for this process through a window in a mask).
Si+HNO3+6HF H2SiF6+HNO2+H2O+H2