Clear sub-resolution assist features for EUV

Burkhardt, Martin; McIntyre, Greg; Schlief, Ralph E.; Sun, Lei

doi:10.1117/12.2048311

Cited by 3 publications

(5 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…(a) Without an assist feature the Bossung curve is symmetric around the best focus (+ 40 nm). (b) Inserting a 10 nm width center assist feature causes the bossing tilt which is consistent with the experimental result in reference[3].…”

supporting

confidence: 87%

“…Foundries and integrated device manufacturers have started to conduct experiments on applying SRAFs for EUV and reported their findings and issues. Experimental results from Burkhardt et al is shown in figure 3.1 ( Figure 2 in the reference [3]) from the NXE:3300B scanner for 18 nm trench CD at 72 nm pitch without (left) and with (right) 10 nm wide assist features slot [3]. For the Bossung curves with assist features, strong tilt and best focus shift are clearly observable.…”

Section: The Need For Assist Features For Euv Lithographymentioning

confidence: 83%

“…Aggressive design rules using the state-of-the-art NA of 0.33 of the NXE:3300B and its successor tools can have imaging below k1 = 0.4, which can extend the current process capabilities for single exposure high volume manufacturing (HVM). Burkhardt et al reported in a previous study that inserting a sub-resolution assist feature (SRAF) within semi-isolated features introduces strong Bossung tilts and best focus shifts, and a general solution for random pitches is not apparent [3]. Kang observed the same issues and proposed to introduce spherical aberrations to correct these effects while having a global impact on the full-chip [4].…”

mentioning

confidence: 98%

“…(a) experimental results from reference[3] show Bossung curves from 18 nm trench, 72 nm pitch without (left) and with (right) 10 nm wide assist features slot. For the Bossung with assist feature, assist feature width = 10 nm, strong Bossung tilt and best focus shift appears.First, two rigorous RCWA simulations were run using an NA of 0.33 and a Y-dipole with 90° pole angle and inner/outer sigma = 0.52/0.92.…”

mentioning

confidence: 99%

See 3 more Smart Citations

EUV resolution enhancement techniques (RETs) for k₁0.4 and below

Hsu¹,

Howell²,

Jia³

et al. 2015

SPIE Proceedings

View full text Add to dashboard Cite

Due to the exponential growth of mobile wireless devices, low-power logic chips continue to drive device scaling. To enable sub-10 nm device scaling at an affordable cost, there is a strong need for single exposure advanced lithography. Extreme ultraviolet lithography (EUVL) is one of the most promising candidates to support the design rules for sub-10 nm. The aggressive mobile device design rules continue to push the critical dimension (CD) and pitch and put very stringent demands on the lithography performance such as pattern placement control, image contrast, critical dimension uniformity (CDU), and line width roughness (LWR).In this paper we report the latest advances in resolution enhancement techniques to address low k1 challenges in EUV lithography, specifically: minimizing the pattern placement error, enhancing the through-focus contrast, and reducing the impact of stochastic effects. We have developed an innovative source-mask optimization (SMO) method to significantly reduce edge placement errors (EPE) [1] [2]. Aggressive design rules using the state-of-the-art NA of 0.33 of the NXE:3300B and its successor tools can have imaging below k1 = 0.4, which can extend the current process capabilities for single exposure high volume manufacturing (HVM). Burkhardt et al. reported in a previous study that inserting a sub-resolution assist feature (SRAF) within semi-isolated features introduces strong Bossung tilts and best focus shifts, and a general solution for random pitches is not apparent [3]. Kang observed the same issues and proposed to introduce spherical aberrations to correct these effects while having a global impact on the full-chip [4]. In this work we introduce a new methodology to apply SRAFs to improve contrast, reduce best focus shift, and improve process window. Finally, the lower number of photons of EUV and the small feature size brings serious issue of the stochastic effect that causes the line-edge-roughness (LER) and local CD uniformity (LCDU). Source power, photoresist, mask bias, and feature size all impact the stochastic effects that can result in large LER for low-k1 patterning. We incorporate an empirical LER model in the SMO NXE frame work to study how the pupil, mask, dose, and target CD can be optimized to reduce stochastic edge placement errors (SEPE). We believe that these advanced EUV RET techniques can support imaging k1 below 0.4 and extend single exposure for an NA of 0.33, as is used in the NXE:3300B and its successor tools.

show abstract

supporting

confidence: 87%

Section: The Need For Assist Features For Euv Lithographymentioning

confidence: 83%

mentioning

confidence: 98%

mentioning

confidence: 99%

See 2 more Smart Citations

EUV resolution enhancement techniques (RETs) for k₁0.4 and below

Hsu¹,

Howell²,

Jia³

et al. 2015

SPIE Proceedings

View full text Add to dashboard Cite

show abstract

“…Foundries started to apply SRAF in EUV and lithographers reported EUV SRAF study and evaluation. 2,3,4,5 The early published works are mostly based on the simulation and experiments with larger assist sizes, i.e., 10-14 nm, for the larger insert pitches of 72 nm above for the minimum pitch of 36 nm application.…”

Section: Introductionmentioning

confidence: 99%

EUV sub-resolution assist feature impact: experimental and simulation evaluation

Chen

Burkhardt

Sieg

et al. 2023

Optical and EUV Nanolithography XXXVI

View full text Add to dashboard Cite

Aggressive off-axis illumination must be used to resolve line space pitches of 28nm and below. The consequence is that the best focus (BF) shifts a lot and depth of focus shrinks rapidly through pitch. This is mainly due to the mask 3D effects. To reduce the impact the best-known method is to introduce sub-resolution assist features (SRAF). We explored wafer printing with SARF size of 6-8 nm and analyzed BF and DOF impact. Clear SRAF sizes of 6-8 nm do not print with PCAR but some 7-8 nm clear SRAF printed with NTD MOR due to the higher resolution and over exposure preference. Then we validated the experiments with SLITHO simulation tool, and we found a good experiment-simulation match of BF/DOF/EL/MEF w and w/o SRAF through pitch with the three P28 illumination candidates. Overall SRAF can improve the DOF and exposure latitude (EL) for the given pitches with SRAF capable and help shift the BF to the favored focus direction. With the validated model we further study BF/DOF/EL/MEF w and w/o SRAF through pitch with the small/medium/large sigma illuminations designed for 28nm pitch, with traditional TaBN and other three candidate absorbers. We will also discuss the SRAF size and placement sensitivities. Through this work we are confident to implement SRAF to enlarge the common process window for a large range of pitches.

show abstract

Challenges of anamorphic high-NA lithography and mask making

Hsu

Liu

2017

Advanced Optical Technologies

View full text Add to dashboard Cite

Chip makers are actively working on the adoption of 0.33 numerical aperture (NA) EUV scanners for the 7-nm and 5-nm nodes (B. Turko, S. L. Carson, A. Lio, T. Liang, M. Phillips, et al., in ‘Proc. SPIE9776, Extreme Ultraviolet (EUV) Lithography VII’, vol. 977602 (2016) doi: 10.1117/12.2225014; A. Lio, in ‘Proc. SPIE9776, Extreme Ultraviolet (EUV) Lithography VII’, vol. 97760V (2016) doi: 10.1117/12.2225017). In the meantime, leading foundries and integrated device manufacturers are starting to investigate patterning options beyond the 5-nm node (O. Wood, S. Raghunathan, P. Mangat, V. Philipsen, V. Luong, et al., in ‘Proc. SPIE. 9422, Extreme Ultraviolet (EUV) Lithography VI’, vol. 94220I (2015) doi: 10.1117/12.2085022). To minimize the cost and process complexity of multiple patterning beyond the 5-nm node, EUV high-NA single-exposure patterning is a preferred method over EUV double patterning (O. Wood, S. Raghunathan, P. Mangat, V. Philipsen, V. Luong, et al., in ‘Proc. SPIE. 9422, Extreme Ultraviolet (EUV) Lithography VI’, vol. 94220I (2015) doi: 10.1117/12.2085022; J. van Schoot, K. van Ingen Schenau, G. Bottiglieri, K. Troost, J. Zimmerman, et al., ‘Proc. SPIE. 9776, Extreme Ultraviolet (EUV) Lithography VII’, vol. 97761I (2016) doi: 10.1117/12.2220150). The EUV high-NA scanner equipped with a projection lens of 0.55 NA is designed to support resolutions below 10 nm. The high-NA system is beneficial for enhancing resolution, minimizing mask proximity correction bias, improving normalized image log slope (NILS), and controlling CD uniformity (CDU). However, increasing NA from 0.33 to 0.55 reduces the depth of focus (DOF) significantly. Therefore, the source mask optimization (SMO) with sub-resolution assist features (SRAFs) are needed to increase DOF to meet the demanding full chip process control requirements (S. Hsu, R. Howell, J. Jia, H.-Y. Liu, K. Gronlund, et al., EUV ‘Proc. SPIE9048, Extreme Ultraviolet (EUV) Lithography VI’, (2015) doi: 10.1117/12.2086074). To ensure no assist feature printing, the assist feature sizes need to be scaled with λ/NA. The extremely small SRAF width (below 25 nm on the reticle) is difficult to fabricate across the full reticle. In this paper, we introduce an innovative ‘attenuated SRAF’ to improve SRAF manufacturability and still maintain the process window benefit. A new mask fabrication process is proposed to use existing mask-making capability to manufacture the attenuated SRAFs. The high-NA EUV system utilizes anamorphic reduction; 4× in the horizontal (slit) direction and 8× in the vertical (scanning) direction (J. van Schoot, K. van Ingen Schenau, G. Bottiglieri, K. Troost, J. Zimmerman, et al., ‘Proc. SPIE. 9776, Extreme Ultraviolet (EUV) Lithography VII’, vol. 97761I (2016) doi: 10.1117/12.2220150; B. Kneer, S. Migura, W. Kaiser, J. T. Neumann, J. van Schoot, in ‘Proc. SPIE9422, Extreme Ultraviolet (EUV) Lithography VI’, vol. 94221G (2015) doi: 10.1117/12.2175488). For an anamorphic system, the magnification has an angular dependency, and thus, familiar mask specifications such as mask error factor (MEF) need to be redefined. Similarly, mask-manufacturing rule check (MRC) needs to consider feature orientation.

show abstract

Clear sub-resolution assist features for EUV

Cited by 3 publications

References 1 publication

EUV resolution enhancement techniques (RETs) for k₁0.4 and below

EUV resolution enhancement techniques (RETs) for k₁0.4 and below

EUV sub-resolution assist feature impact: experimental and simulation evaluation

Challenges of anamorphic high-NA lithography and mask making

Contact Info

Product

Resources

About

Clear sub-resolution assist features for EUV

Cited by 3 publications

References 1 publication

EUV resolution enhancement techniques (RETs) for k10.4 and below

EUV resolution enhancement techniques (RETs) for k10.4 and below

EUV sub-resolution assist feature impact: experimental and simulation evaluation

Challenges of anamorphic high-NA lithography and mask making

Contact Info

Product

Resources

About

EUV resolution enhancement techniques (RETs) for k₁0.4 and below

EUV resolution enhancement techniques (RETs) for k₁0.4 and below