Abstract
This paper identifies the defect adders, for example, post hard-mask etch residue, post metal etch residue, and blocked etch metal island and investigates the removal characteristics of these defects within the oxide-masked Al etching process sequence. Post hard-mask etch residue containing C atom is related to the hardening of photoresist after the conventional post-RIE ashing at 275∘C. An in situ O2-based plasma ashing on RIE etcher was developed to prevent the photoresist hardening from the high-ashing temperature; followed wet stripping could successfully eliminate such hardened polymeric residue. Post metal etch residue was caused from the attack of the Al sidewall by Cl atoms, and too much CHF3 addition in the Al main etch step passivated the surface of Al resulting in poor capability to remove the Al-containing residue. The lower addition of CHF3 in the Al main etch step would benefit from the residue removal. One possibility of blocked etch metal island creating was due to the micromasking formed on the opening of TiN during the hard-mask patterning. We report that an additional TiN surface pretreatment with the Ar/CHF3/N2 plasmas could reduce the impact of the micromasking residues on blocked metal etch.
Highlights
As the dimension of devices continues to scale down, the Al patterning by dry etching becomes challenging due to insufficient amount of photoresist to leave for etch rate fluctuation [1]
We proposed an in situ O2-based plasma ashing process on MxP+ etcher to prevent the photoresist hardening from the conventional post-RIE ashing at 275◦C
An in situ O2-based plasma ashing on RIE etcher is developed to prevent the photoresist hardening from the high-ashing temperature
Summary
As the dimension of devices continues to scale down, the Al patterning by dry etching becomes challenging due to insufficient amount of photoresist to leave for etch rate fluctuation [1]. This paper describes the identification of the foregoing defect adders Among these defect adders, post hard-mask etch residue is commonly observed after the oxide hardmask patterning followed by resist ashing and wet stripping. Post hard-mask etch residue is commonly observed after the oxide hardmask patterning followed by resist ashing and wet stripping Such defect formation is found strongly related to the ashing process temperature. Blocked metal etch resulting in metal island during the Al etching The reduction of these defect adders optimizing O2 plasma ashing sequence, moderating the addition of CHF3 gas in the Al etching, and using additional TiN surface pretreatment prior to the TiN/Ti breakthrough step was reported
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