Photosensitivity and line-edge roughness of novel polymer-bound PAG photoresists

Substantially improved photoresist material designs, which can provide higher photosensitivity and precise critical dimension and edge roughness control, will be required to enable the application of next generation lithography technology to the production of future sub-65 nm. node IC device generations. The development and characterization of novel material platforms that solve the aforementioned basic problems with chemically amplified resists (CARs) is essential and is already one of the major subjects of modem lithography research. In that regard, we have pursued development of a variety of 193 nm and EUV CARs that contain photoacid generator (PAG) units covalently bonded directly to the resin polymer backbone. However, the detailed structure-property relationships that result from this direct attachment of the PAG functional group to the polymer have previously not yet been rigorously characterized. In this work, the lithographic properties of a polymer-bound PAG CAR (GBLMwA-co-EAMA-co-F4-MBS.TPS) and its blended-PAG analog resist (GBLMA-co-EAMA blend F4-IBBS.TPS) were studied and compared. The direct incorporation of PAG functionality into the resist polymer, where the resulting photoacid remains bound to the polymer, showed improved photosensitivity, resolution, and lower LER as compared with the analogous blended-PAG resist. The improved resolution and LER were expected due to the restricted photoacid diffusion and uniform PAG distribution provided by direct incorporation of the PAG into the polymer backbone to make a single-component resist material. The ability to load higher levels of PAG into the resist provided by this PAG incorporation into the polymer, as compared to the low PAG concentrations attainable by traditional blending approaches, overcomes the sensitivity loss that should result from reduction in photoacid diffusivity and concomitant smaller acid-catalytic chain lengths. In fact, the polymer-bound PAG resist achieves a faster photospeed than the blended-PAG analog material under DUV radiation in the case of the materials reported here while still providing all of the aforementioned improvements such as the improved line edge roughness.