Polymer structure modifications for immersion leaching and watermark control

Abstract

Immersion materials have to overcome immersion-issues for successful wet process introduction to semiconductor mass production. Component-leaching issue is one of the most influential wet process huddles, which is related to immersion-liquid and projection lens contamination as well as resist patterning performances. In this paper, we will introduce our experimental results of leaching blocking effects resulted from the modification of polymer and additive structures and from the application of top surface blocking layers. PAG-leaching level of resist film formed of low Tg resin shows the highest meanwhile that of high Tg resin is the smallest leaching value. The interaction forces between additives and resin platforms are the most important to prevent additives leaching to immersion liquid.We have tested 3 different types of resin structures to modify the interaction forces between resin platform and resist components especially PAG molecules and photo-generated acid molecules. We changed 2-hydroxyethyl methacrylate(2-HEMA) contents to be 5, 10, 15% in our base resin, COMA-acrylate hybrid system to modify the hydrophilicity of resist platforms. By mimicking immersion process to obtain wet-performance of their resists we have obtained relative value of component-leaching. Interaction-force between resist platform and PAG was seemed to be largest when resist component-leaching is least so that the pattern profiles become to be vertical. It was appeared that the 5% 2-HEMA containing resin and TPS-Nonaflate PAG system showed the best performance because of its low leaching resulted from their strong interaction forces.Another polymer parameter to determine the component-diffusivity is glass transition temperature, Tg. Low Tg means high mobility of resin by small thermal energy due to high free volume contents inside of the resist film which can act as diffusion pathways of resist components. 10% MA resin system shows the lowest Tg, around 140 • C and the most serious T-topping profiles.Defectivity issue becomes more important in immersion process, which is most related to the partial leaching by residual water and resulted in watermark defects. We evaluated the relative easiness of watermark formation on different resist films by correlations between static and dynamic contact angles. We made 2 different resist films composed of 2 different water-repellent functional group monomers. Static contact angles of developer as well as DI water were measured. It was found indirectly that amphiphilicity of resist film surface makes positive effect on watermarks formation, that is, more hydrophobic and more developer-philic resist film remains less residual water droplets.

Synthesis of Narrow Molecular Weight Distribution Norbornene-Lactone Functionalized Polymers by Nitroxide-Mediated Polymerization: Candidates for 193-nm Photoresist Materials

“…P-acetoxystyrene (AcOST), which has been employed in the past as a key component in 248-nm photoresists [68], exhibited the best controlling ability based on the lowest dispersity ( � � ⁄ ~ 1.29) at a concentration as low as 5 mol% in the feed. Pentafluorostyrene (PFS), also offering relatively good control ( � � ⁄ ~ 1.47 and 1.31 for 5 and 10 mol% in the feed, respectively), is of interest, because fluorinated polymers have been shown to be good candidates for both 157-nm and 193-nm photoresists, due to their low absorption, good etch resistance properties [69][70][71][72][73] and high hydrophobicity [74,75], which is especially important in immersion lithography. 2-vinyl naphthalene (VN) was also an effective co-monomer in being able to produce copolymers with low dispersities ( � � ⁄~ 1.3) with as low as 5 mol% in the feed.…”