Wet trimming process for critical dimension reduction

Abstract

Plasma trimming is a method widely used to achieve small feature sizes beyond the capability of photolithography. Plasma processes reduce the dimensions of photoresist, anti-reflective coating, hardmask, or device substrate patterns with varying degrees of anisotropy. The vertical trim rate is higher than or equal to the lateral trim rate. As a result, much of the line-edge roughness from the resist pattern remains. High aspect-ratio resist patterns are subject to necking and collapse during this process. However, by using a developer-soluble hardmask in place of traditional anti-reflective layers, it is possible to achieve controllable, anisotropic trim rates, as well as reduced roughness. Moreover, the process benefits from a very thin resist, or imaging layer, instead of relying on a thicker mask with a high aspect-ratio. The hardmask is patterned during a standard resist develop step, and the resist may be stripped prior to substrate etching due to the high etch resistance of the hardmask. Many other advantages have been discovered from this wet trimming process, including high resolution, extended depth of focus, controllable trim rate, and lower cost than traditional methods.

SADP for BEOL using chemical slimming with resist mandrel for beyond 22nm nodes

“…Plasma based resist trimming tends to taper the top profile of the resist causing problems later on in the SADP processing. 8 A relatively new approach to trimming the resist CD is track based wet chemical slimming. As compared with plasma trimming, this process can be done within the litho cluster before moving to the spacer deposition step, eliminating the need for an extra etch processing step.…”