Performance evaluation of nonchemically amplified negative tone photoresists for e-beam and EUV lithography

Abstract

Abstract. Although extreme ultraviolet (EUV) lithography is being considered as one of the most promising nextgeneration lithography techniques for patterning sub-20 nm features, the development of suitable EUV resists remains one of the main challenges confronting the semiconductor industry. The goal is to achieve sub-20 nm line patterns having low line edge roughness (LER) of <1.8 nm and a sensitivity of 5 to 20 mJ∕cm 2 . The present work demonstrates the lithographic performance of two nonchemically amplified (n-CARs) negative photoresists, MAPDST homopolymer and MAPDST-MMA copolymer, prepared from suitable monomers containing the radiation sensitive sulfonium functionality. Investigations into the effect of several process parameters are reported. These include spinning conditions to obtain film thicknesses <50 nm, baking regimes, exposure conditions, and the resulting surface topographies. The effect of these protocols on sensitivity, contrast, and resolution has been assessed for the optimization of 20 nm features and the corresponding LER/line width roughness. These n-CARs have also been found to possess high etch resistance. The etch durability of MAPDST homopolymer and MAPDST-MMA copolymer (under SF 6 plasma chemistry) with respect to the silicon substrate are 7.2∶1 and 8.3∶1, respectively. This methodical investigation will provide guidance in designing new resist materials with improved efficiency for EUVL through polymer microstructure engineering.

EUV photofragmentation study of hybrid nonchemically amplified resists containing antimony as an absorption enhancer

“…3) revealed typical signals corresponding to the aliphatic and aromatic contributions (C-C/C-H), C-O, C-S, COO, and CF 3 functionalities, which agree with the data previously obtained for the MAPDST homopolymer and MAPDST-MMA copolymers. 15,21,[35][36][37] The S 2p spectrum of the untreated 2.15% MAPDSA-MAPDST surface shows four spinorbit split doublets, having binding energies that are characteristic of S-C, 38,39 S]O, SO 3 , and SO 4 . 40 The presence of four contributions in the S 2p envelope was necessary to t the experimental signal, which probably could be caused by a possible partial oxidation/degradation of the resists.…”

“…In the last years we have studied the photofragmentation of several n-CAR homopolymers and co-polymers under EUV synchrotron radiation (SR) excitation. 4,9,15,16,21 The obtained results showed that the photodegradation processes affected mainly the triate group but also the carbon backbone of the resists. In those works it was hypothesized that the neutral sulde Ar-S-CH 3 is formed aer irradiation rendering the irradiated area insoluble in the developer.…”

“…The sizing dose used for high resolution line patterns when the SbF 6 À units were incorporated in the 1.5% and 2.15% resists resulted in the improvement of the resists' sensitivity by 2.5 and 10 times, respectively, compared to the poly-MAPDST resist. 15,21,23 Therefore, herein it is presented the photofragmentation investigation of hybrid 2.15% MAPDSA-MAPDST resist incorporating EUV absorbing metals such as antimony. The resist structure incorporates a radiation sensitive sulfonium triate and the inorganic moiety SbF 6 À acting as a sensitivity enhancer for 13.5 nm photons.…”

Selective Fragmentation of Radiation-Sensitive Novel Polymeric Resist Materials by Inner-Shell Irradiation

“…In our previous work, it was hypothesized that the copolymer may develop a rearrangement during irradiation that finally kept the S−C and SO x functional groups almost intact. 7 We have also observed that in copolymers of MMA and poly(MAPDST-co-MMA), the former acts as a dissolution inhibitor, whereby patterning can be achieved at lower doses versus the MAPDST homopolymer. From this, we can infer that the MMA unit in the polymer microstructure provides photostability.…”

Studying the mechanism of hybrid nanoparticle EUV photoresists

“…Research in short wavelength lithography, especially for extreme ultraviolet lithography (EUVL), is attracting considerable attention [1][2][3][4][5][6][7][8][9][10] . The next generation EUV photoresists should combine high etch resistance, high imaging quality and appropriate light absorption.…”