Method for monitoring self-aligned contact etching

A method for monitoring self-aligned contact (SAC) etching process, said method comprising the steps of:

• providing a wafer with an oxide layer as an oxide control wafer;
• performing a SAC etching process in an etching chamber to etch said oxide control wafer and a SAC wafer by a first gas CH3F and a second gas, said CH3F having a variable flow rate, wherein the flow rate variation of said CH3F changes said depth of etching profile transition, thereby a depth of etching profile transition and a depth of etching stop are generated in said oxide control wafer and said SAC wafer;
• and
• measuring said depth of etching profile transition and said depth of etching stop in said oxide control wafer to monitor an etching chamber condition of said SAC etching process.

A method for monitoring an etching process using CH3F and C4F8 as reactants, said method comprising the steps of:

• providing a wafer with an oxide layer as an oxide control wafer;
• performing said etching process in an etching chamber using said CH3F and said C4F8 as reactants to etch said oxide control wafer and a wafer with semiconductor devices, thereby a depth of etching profile transition and a depth of etching stop are generated in said oxide layer, said CH3F having a variable flow rate, wherein the flow rate variation of said CH3F changes said depth of etching profile transition;
• and
• measuring said depth of etching profile transition and said depth of etching stop in said oxide control wafer to monitor an etching chamber condition.