Theoretical study on defect risks of chemically amplified resists used for extreme ultraviolet lithography

Abstract

In lithography, resist patterns are fabricated through chemical reactions induced by radiation. In the highly resolving lithography such as extreme ultraviolet (EUV) lithography, the stochastically generated defects (stochastic defects) are a serious concern. In this study, the variation of resist polymer caused by stochastic effects was investigated, assuming line-and-space resist patterns to assess the defect risks. Using a half pitch HP, a thermalization distance r 0, a total sensitizer concentration C s, and an initial standard deviation of the number of protected units per polymer molecule σ i as variables, the resist pattern formation was simulated on the basis of the reaction mechanisms of chemically amplified EUV resists. The frequency distribution of polymer molecules with the given number of protected units was calculated at the centers of lines and spaces. By defining a total defect risk (the sum of pinching and bridging risks), its dependences on HP, r 0, C s, and σ i were clarified.

Defect risks at interfaces of chemically amplified resists in extreme ultraviolet lithography process

“…This suggests that the interfacial effect related to low-energy secondary electrons is small at the half-depth of the resist film when the film thickness is larger than 32 nm, as reported previously. 26) For BC VR = 0, the pinching risk ranged from 1.2 × 10 −2 to 7.4 × 10 −3 , with 8.8 × 10 −3 as the average. For BC VR = 1, the pinching risk ranged from 1.4 × 10 −2 to 2.0 × 10 −2 , with 1.8 × 10 −2 as the average.…”

“…The obtained histogram was fitted (the solid lines in the graph) in accordance with a previously reported procedure. 26) The fitting equations for N m (N p , 0) are ´--…”

“…However, the short-range backexposure effects of low-energy secondary electrons [22][23][24][25] should be taken into account to control the vertical profiles of resist patterns in addition to the factors described previously. In this study, the sensitization and reaction processes induced in chemically amplified EUV resists were calculated for eight combinations of boundary conditions using a Monte Carlo method to estimate the dependence of defect risks 26) on the conditions of resist interfaces. Figure 1 shows schematics of the assumed boundary conditions for low-energy secondary electrons.…”

Effects of photoacid generator decomposition on dissolution kinetics of poly(4-hydroxystyrene) in tetraalkylammonium hydroxide aqueous solutions

“…1 In the case of chemically amplified resists which is most popular in industry, the increase of sensitizer concentration is essentially required to suppress the stochastic effects. 2 So, the effects of decomposition products from sensitizers on the dissolution dynamics of resist films become an issue to be cared. In this study, we investigated the effects of PAG decomposition on dissolution dynamics of PHS films in tetraalkylammonium hydroxide (TAAH) aqueous solutions to clarify the relationship between the decomposition products of photoacid generator (PAG) and the alkyl chain length of tetraalkylammonium hydroxide.…”

Sensitization of polymethacrylate resist with adding acid-generating promoters upon exposure to EUV light

“…Therefore, these factors are among the greatest concerns for the realization of next-generation EUV resists. [15][16][17][18][19][20][21][22] For example, in the case of shot noise, we should consider the number of absorbed photons, because the energy of EUV photons is 14 times higher than that of ArF excimer laser photons, and the profile of absorbed photons becomes correspondingly sparse when the same dose is irradiated. 23) To mitigate shot noise, the reaction efficiency between the secondary electrons and the PAG is increased by increasing PAG loading, which further increases the quantum yield of the acid.…”