Process Margin Improvement and Cost Saving from a New Plasma Oxide Etch Process with Endpoint Algorithm During Photolithography Positive- to Negative-Tone Develop Conversion

A DRAM contact oxide dry etch process had severe yield loss and inline parameter deviation when the photo process was changed from legacy positive tone develop (PTD) to negative tone develop (NTD) for cost saving. A new contact oxide etch with a new peak and valley algorithm has been developed to improve the process margin by >50% depth of focus (DOF). The results from the implementation of this new contact etch process together with the PTD to NTD conversion improve the contact oxide etch process window for better chamber to chamber matching and inline critical dimension (CD) uniformity.