Main chain decomposable star shaped polymer for EUV resist

Abstract

The Extreme Ultra Violet lithography (EUVL) is expected to be the most promising semiconductor fabrication technology for 22 nm node and beyond. Kozawa and his colleagues have documented that non-constant acid diffusion coefficient have a significant impact on the latent image quality of 22 nm patterns.[1] We prepared a novel main chain decomposable star shaped polymer (STAR polymer) to examine the concept. STAR polymer consists of a core unit and several arm units which connect to the core unit as shown in Fig.1. The arm units are partially protected poly (p-hydroxystyrene) (PHS) base linear polymer. The core unit that attached on the arm units employs easily acid cleavable group. The adoption of living anion polymerization for the arm units of the STAR polymer makes the controlled polymerization of one monomer unit possible.Based on this material design concept, the protecting group on the arm unit is de-protected by the acid generated during exposure and continues its reaction at the Post Exposure Bake (PEB) step and the acid will also cleave the bonding of the core unit which would then result in a lower molecular weight polymer of lower T g .The concept of the novel polymer, which is the decomposition of the core and protecting group of arm units of the STAR polymer, was confirmed with a gel-permeation-chromatography (GPC) study.The thermal property of the exposed and unexposed area was also investigated through a thermal flow method. The T g decrease of the exposed area was observed with the STAR polymer, regardless of increase in T g of the linear polymer.General lithographic performance on EUV exposure for STAR polymer was also discussed.

Chain-Scission Polyethers for EUV Lithography

“…These properties, however, have been found to be inversely related, a relationship commonly referred to as the RLS trade-off [1]. To overcome the RLS trade-off, the lithographic community is investigating alternative resist platforms such as molecular glasses [2][3][4], polymer-bound photoacid generators (PAGs) [5][6][7], and chain-scission polymers [8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”

Characteristics of main chain decomposable star shaped polymer on EUV lithography

“…We have reported the decomposition behavior of the STAR polymer induced by photo acid, the thermal properties of the STAR polymer film in exposed and unexposed area and lithographic performance using Micro Exposure Tool (MET) in previous paper [9]. From these results, it's found that the STAR polymer could work as main chain decomposable polymer and have a possibility to achieve better lithographic performance than the conventional linear polymer.…”

“…TF was determined as the temperature at which a CD shrink of 10% was observed as compared to a wafer without a post bake according to the same manner reported in previous paper. [9][10] Characteristics of the polymers are summarized in Table 1 For TF measurement, two different kinds of TF are investigated. The TF measured using the wafer where 170 nm hole feature is fabricated is Pre-TF.…”

Roughness characterization in the frequency domain and LWR mitigation with post-litho processes

“…To reach the ITRS target, a reduction of 50% is required. Many studies have been doing on both optical equipment (source 5,6 , mask 7,8 , optical system 9 ) and photo materials (resist composition 10,11,12,13,14,15,16,17 , development process chemistry 18 ) in order to reduce LWR. Even combining them, it's not possible to reach the sub-32nm node ITRS targets, yet.…”