Polyhedral Oligomeric Silsesquioxane (POSS) Based Resists:  Material Design Challenges and Lithographic Evaluation at 157 nm

Abstract

In this paper we describe the lithographic behavior and related material properties of a new class of chemically amplified, positive tone, silicon-containing methacrylate photoresists incorporating the polyhedral oligomeric silsesquioxane (POSS) group as the etch-resistant component. POSS-bearing monomers were copolymerized with methacrylic acid (MA), tertbutyl methacrylate (TBMA), tert-butyl trifluoro methacrylate (TBTFMA), itaconic anhydride (IA), and 2-(trifluoromethyl) acrylic acid (TFMA), in various compositions. A perfluorooctylsulfonate-based photoacid generator (PAG) was used to deprotect TBMA (or TBTFMA) to base soluble carboxylic acid by heating after exposure. XPS and angular XPS analysis were used to examine possible surface segregation phenomena. It was proven that POSS surface enrichment occurs for the POSS-TBMA copolymers while surface segregation may be reduced if suitable additional resist components are selected. The POSS-based resists were studied for 157-nm lithographic applications and found to have high sensitivity (<10 mJ/cm 2 under open field exposure), no silicon outgassing, and sub-100-nm resolution capabilities. Ninety nanometer patterns in 100-nm thick films were resolved. At present, their absorbance is high (∼4 µm -1 ) for single-layer lithographic applications at 157 nm; however, high etch resistance in oxygen plasma makes them suitable for bilayer schemes.

One‐Step Direct‐Patterning Template Utilizing Self‐Assembly of POSS‐Containing Block Copolymers

“…[26] POSS molecules are well known to form nanometer size semi-crystalline or crystalline domains, which are thermally and physically more robust than silicones, [27] and are converted to silica on exposure to oxygen plasma. [28][29][30] The high etch contrast between the PMAPOSS and PS/PMMA blocks along with the semi-crystalline nature of the POSS domains, allows the use of self-assembled PS-b-PMAPOSS and PMMA-b-PMAPOSS to fabricate high-resolution patterns. Here, we report the selfassembly of the POSS containing BCPs in thin-films by simple solvent annealing on unmodified substrates to obtain both vertically oriented lamellae and cylinders, and subsequent conversion to a hard mask by a single-step highly selective oxygen plasma etching (Fig.…”

Directly patternable benzocyclobutene and methacrylate silsesquioxanes for microelectronics packaging

“…(11). Samples were prepared from B-staged resins, spun onto silicon wafers and cured at 250°C for one hour under nitrogen.…”

“…7) POSS has seen extensively study as a component of photosensitive nanocomposites for imprint lithography patterned with acrylic, thio-ene and epoxy chemistries. 8)10) POSS has also been incorporated into chemically amplified photoresists 11) and block copolymers to improve etch resistance. 12),13) However, the literature does not describe POSS materials that can be photolithographically patterned that have the thermal stability, CTE, and dielectric properties required for use in modern packaging applications.…”

Photoimaging and Lithographic Processes in Polymers

“…For example, tetrafluoroethylene brings transparency, t-Boc protected groups act as solubility switch, while norbornene bring etch resistance (Chart 12.6). Besides fluorine-containing polymers, polysilanes, polysiloxanes, and polysilsesquioxanes were considered as useful polymers for photoresists at 157 nm due to their low absorbance and resistance to etching conditions [1,[64][65][66].…”