Endpoint detection in low open area and/or high aspect ratio etch applications

A non-transitory computer readable storage medium comprising a program product which, when executed, is configured to perform an operation for detecting an endpoint for an etch operation of semiconductor substrates, the operation comprising:

• obtaining a reference emission from a first etch operation of a first layer of material of a first substrate of a first type of pattern, the first layer of material having a first thickness;
• performing an second etch operation on a second layer of material of a second substrate of the first type of pattern, the second layer of material having a second thickness, wherein the first thickness is greater than the second thickness;
• measuring a plasma optical emission during the etch operation of the second substrate;
• calculating, using a processor, a differential curve between the reference emission and the plasma optical emissions;
• determining an endpoint for the second etch operation on the second substrate based on a detection of a pattern in the differential curve for stopping the etch operation;
• and
• stopping the second etch operation based on the determination that the endpoint for the etch operation has been reached.

A system, comprising:

• a central processing unit (CPU);
• memory communicately coupled to the CPU;
• and
• a program operable to provide instructions to the CPU controlling an etch operation in a plasma processing system, wherein the program is stored in the memory and configurable to be executed by the CPU, the program including:
• instructions for obtaining a reference emission from a first etch operation of a first layer of material of a first substrate of a first type of pattern, the first layer of material having a first thickness;
• instructions for performing an second etch operation on a second layer of material of a second substrate of the first type of pattern, the second layer of material having a second thickness, wherein the first thickness is greater than the second thickness;
• instructions for measuring a plasma optical emission during the etch operation of the second substrate;
• instructions for calculating, using the CPU, a differential curve between the reference emission and the plasma optical emissions;
• instructions for determining an endpoint for the second etch operation on the second substrate based on a detection of a pattern in the differential curve for stopping the etch operation;
• and
• instructions for stopping the second etch operation based on the determination that the endpoint for the etch operation has been reached.