Design and development of low activation energy based nonchemically amplified resists (n-CARs) for next generation EUV lithography

• n-CARs, EUV resists for NGL
• Low activation energy
• High resolution isolated, dense and complex patterns
• Peak force QNM technique.
• Nano-mechanical analysis of dense line patterns

The rendition of EUV resists is one of the major challenges for high volume production and cost-effective realization of next generation (NG) EUV technology. EUV lithography (EUVL) is a promising technique which has been predicted to print 16 nm line patterns and beyond. Thus EUV resists must have exceptionally higher sensitivity and resolution than current resists, because IC technology scaling of isolated resist lines and LWR have been set to ~ 15 nm and ~ 1.5 nm, respectively. There is everlastingly, contest to meet photosensitivity and resolution simultaneously with the traditional chemically amplified resists (CARs) due to random walk nature of photo-acid diffusion and minimal control over critical dimension (CD), which eventually confines its adeptness to be front end EUV resists. The present study demonstrates the development of a new non-chemically amplified negative tone resist (n-CARs), MAPDST–i-PrMA [Mw = 14,000 g/mol] using suitable monomer, bearing radiation sensitive trifluoromethanesulfonate functionality. EUV sensitivity (E0) and optimum exposure dose (Eox) for this newly designed and developed resist have been experimentally calculated to be 11.3 mJ/cm2 and 26.6399 mJ/cm2 respectively. Similarly, EBL sensitivity (E'0), contrast (γ) and reactive ion etching (RIE) selectivity (S) (CHF3/O2 @35/4 SCCM) of the developed resist formulation are computed as 2.14 μC/cm2, 0.66 ± 0.04 and 1.77, respectively. The Derjaguin-Muller-Toporov (DMT) modulus and adhesion for EUV exposed line patterns of 20, 25, 30, 35, 40, 45 & 50 nm with various L/S characteristics are ~ 3.2 ± 0.16 GPa and ~ 33 ± 4 nN, respectively. Thus, the significantly low activation energy (11.3 mJ/cm2) of the newly developed resist formulation and manifestation of all the polarity switching during radiation exposure avoid acid diffusion, blurring of resist patterns and anticipated to meet the stringent requirements of EUVL for sub-20 nm node.

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