Residue Testing of Developer-Soluble Bottom Anti-Reflective Coatings

Abstract

Organic developer-soluble bottom anti-reflective coatings (DBARCs) are commonly used in the photolithographic process for implant and high-k/metal gate integration. They provide added reflectivity control over topography compared top anti-reflective coatings (TARCs). DBARCs are coated onto substrates and then removed during the develop step with the resist. Occasionally a thin post-develop residue (PDR) remains after the DBARC removal process. The main drivers of this residue are DBARC bake temperature, followed by develop time. For this investigation the amount of residue was tested using Si, SiO 2 , native SiO 2 , SiN, and HfO 2 substrates at different bake temperatures. In addition, contact and proximity baking are compared and shown to be equivalent in terms of their effect on PDR. This work demonstrates that optimizing the bake process of a DBARC is an effective way to control PDR on a variety of substrates.

Use of DBARCs Beyond Implant

“…A significant amount of research has gone into quantifying and understanding the trends of residue produced by different DBARCs. The residue has been quantified using ellipsometry, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) (9,18,19,20,21,22). Trends through processing conditions have also been evaluated.…”

“…Trends through processing conditions have also been evaluated. For non-photosensitive DBARC, BARC bake temperature emerged as the biggest process control for residue (20). BARC bake temperature was also found to affect certain PS-DBARCs (18).…”

“…The chemistry components, thickness, and exposure dose all affected the post-develop residue (9,21,22). In both PS and non-PS DBARCs, it was found that the substrate also influenced the residue (19,20). With the diverse factors that are involved with residue, it is a challenge that will continue to garner focus, especially as HKMG processes move into production.…”

Comparative Study of Photosensitive Versus Non-Photosensitive Developer-Soluble Bottom Anti-Reflective Coating Systems

“…The PDR left behind can limit the wet-etch or cleaning processes that follow. Again, preference for the non-PS DBARC or PS DBARC will depend on the substrate because the affinity for leaving PDR is driven by the substrate compatibility with the DBARC design and processing conditions (6,11).…”

“…Developing for long periods of time has an effect similar to lower bake temperatures and can produce undercut as shown in Figure 1a (4,5). So both bake temperature and develop time must be balanced to achieve optimum performance (6,7,8).…”