Contact Edge Roughness In The Etching Of High Aspect Ratio Contacts In Sio2

As the pattern density increases and critical dimensions decrease to the nanometer scale in microelectronics fabrication, contact edge roughness (CER) in high aspect ratio contacts (HARCs) becomes a major lithographic challenge. CER consists of striations or other roughness in the sidewalls of features etched in wafers. The origin of CER is the randomness of lithography that produces the photoresist (PR) mask as the feature size shrinks and mechanical stresses on the PR. CER appears as the PR is eroded and the roughness in the mask is transferred to the underlying material being etched. This results in pattern distortion such as scalloped and elliptic profiles which degrade the device performance.