Stochastic effects in 11 nm imaging of extreme ultraviolet lithography with chemically amplified resists

Abstract

The resolution of extreme ultraviolet (EUV) lithography with chemically amplified resist processes has reached 16 nm (half-pitch). The development of chemically amplified resists is ongoing toward the 11 nm node. However, the stochastic effects are increasingly becoming a significant concern with the continuing shrinkage of features. In this study, the fluctuation of protected unit distribution caused by the stochastic effects during image formation was investigated assuming line-and-space patterns with 11 nm half-pitch. Contrary to expectations, the standard deviation of the number of protected units connected to a polymer after postexposure baking (PEB) did not differ from that for 16 nm half-pitch. The standard deviation after PEB increased with the effective reaction radius for deprotection and the initial standard deviation before PEB. Because of the severe requirements for resist processes, the stochastic effects in chemical reactions should be taken into account in the design of next-generation resists.

Feasibility study of sub-10-nm half-pitch fabrication by chemically amplified resist processes of extreme ultraviolet lithography: I. Latent image quality predicted by probability density model

“…The simulation results were compared with LER of line-andspace patterns with 11-32 nm half-pitch, that was recalculated on the basis of the results of previous studies. 29,30) The feasibility of sub-10-nm half-pitch fabrication with EUV lithography is discussed from the viewpoint of resolution and LER without assuming any required sensitivities, considering the potential performance of state-of-the-art EUV resists.…”

Dependence of stochastic defect generation on quantum efficiency of acid generation and effective reaction radius for deprotection in chemically amplified resist process using extreme ultraviolet lithography

“…30) The relationships between LER, chemical gradient, and stochastic effect have been discussed in detail elsewhere. [35][36][37][38] On the other hand, stochastic defect generation is related to the protected unit fluctuation at x = «p 1/2 and 0. The dependence of the protected unit fluctuation at x = «p 1/2 and 0 on the half-pitch has also been discussed in detail in a previous study.…”

Relationships between Stochastic Phenomena and Optical Contrast in Chemically Amplified Resist Process of Extreme Ultraviolet Lithography

“…[26] The relationships among LER, the chemical gradient, and the stochastic effect have been discussed in detail. [31][32][33][34] The fluctuation in the number of protected units near the center of the line pattern leads to the generation of pinching. [18] It has been reported that the elimination of pinching is important for the development of chemically amplified resists with sub-15 nm resolution.…”

“…The final standard deviations at ±p 1/2 /2 were 2.80, 2.89, and 3.17, respectively. LER was calculated to be 2.07, 2.14, and 2.34 nm for σ i =0, In our previous studies, [31][32][33][34][35] we have discussed the latent image quality including the protected unit fluctuation mainly assuming an acid generator concentration of 10 wt% in a TPS-Tf equivalent and an effective reaction radius of 0.1 nm for deprotection. The corresponding quantum efficiency was 2.0.…”