Evaluation of local CD and placement distribution on EUV mask and its impact on wafer

Vaenkatesan, Vidya; Adrichem, Paul van; Kooiman, Marleen; Kubis, Michael; Look, Lieve Van; Frommhold, Andreas; Gallagher, Emily; Nam, DS; Mulkens, Jan

doi:10.1117/12.2538243

Cited by 7 publications

(7 citation statements)

References 5 publications

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“…For Stochastic modeling, the Analysis of variance (ANOVA) is applied. [7] Firstly, we collected the CD data on the four corners of a design pad as shown in Figure 4. Therefore, for each contact hole, we can map its location exactly to the location on the photomask.…”

Section: Sec21 Experimental Lithography Process Setup and Modeling Flowmentioning

confidence: 99%

EUV SRAFs printing modeling and verification in 2D hole array

Tan

Wei

Yin

et al. 2023

Optical and EUV Nanolithography XXXVI

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The requirement of larger common overlap process window in EUV patterning is getting stronger when the design pitch continues to shrink. The reflective optics in EUV generate various imaging issues due to mask 3-dimensional (M3D) effects. Therefore, sub-resolution assistant features (SRAFs) insertion is preferred for the resolution enhancement technology. SRAFs insertion can create a dense optical environment that will prevent strong best focus shift between semi-isolated and isolated features. From the previous study, SRAFs insertion and stochastic printing can be modeled and verified with a flow utilizing a compact resist 3D model (R3D) in conjunction with stochastic model. In this work, additional SRAFs investigations and studies extend to a better choice of alternative EUV mask absorbers that can mitigate M3D effects and have better lithography performance. In this paper, a low-n dark field EUV mask with regular hole grid design and positive tone development (PTD) is considered. The SEM (scanning electron microscope) images of through pitches with various SRAFs sizes and combination of SRAF to main space are collected. The SRAFs printing pixels can be captured and modeled with compact resist stochastic modeling. The results can be verified using average printed area (APA) metric with a R3D model and the simulation studies have proved the SRAFs printing sensitivity to the photomask biases.

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Section: Sec21 Experimental Lithography Process Setup and Modeling Flowmentioning

confidence: 99%

EUV SRAFs printing modeling and verification in 2D hole array

Tan

Wei

Yin

et al. 2023

Optical and EUV Nanolithography XXXVI

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“…The area of each contact is calculated and the square root is taken to arrive at an area-based-CD measurement. Previous studies [4,5] have shown that using an area-derived CD value instead of a measurement box averaged cutline CD (as is standard for conventional CDSEM measurements) provides a better metric for studying LCDU. The mask LCDU can then be computed and Figure 6 shows the result in 1-sigma 4X scale nanometers for each of the 4 pitches examined.…”

Section: Mask Lcdu From Direct Measurementmentioning

confidence: 99%

“…Once this is done the LCDU and its components can be calculated. The ANOVA or Linear Nested Model approach for calculating the LCDU decomposition is described in detail in the work of Vaenkatesan and Van Look et al [4,7]. Figures 8, 9, 10 above shows the results of the decomposition for the 6 mask location of the three pitches that were well resolved on the wafer.…”

Section: Reticle Lcdu From Wafer Data Decompositionmentioning

confidence: 99%

Extreme ultraviolet lithography reticle local CD uniformity correlation to wafer local CD uniformity

Lyons¹,

Wallow²,

Nam³

et al. 2022

Photomask Technology 2022

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In this contribution we describe an experimental study measuring local CD uniformity (LCDU) of DRAM contact arrays on both an EUV reticle and corresponding exposed wafer. Direct measurement of LCDU from reticle SEM images is compared to the reticle component of wafer level LCDU determined by decomposition of wafer level only data. The goal of this study is to better understand the contribution of reticle LCDU to wafer LCDU and the degree of accuracy to which the reticle component can be determined without reticle metrology. In addition to comparing the two methods of determining mask LCDU we use the measured mask contours as input to ASML Tachyon lithography simulation software and compare the simulated and experimental wafer CDs, CD distributions, and local MEEF. This gives some insight on the proportion of the mask variability coming from the variation of absorber edge placement. Three different DRAM contact array pitches are examined 36, 38 and 40nm. Each array contains a registration mark to allow each individual contact to be reliably identified. Reticle SEM images are collected for 20 locations for each pitch and the three highest and three lowest LCDU locations are selected. These six selected reticle locations (per pitch) are measured by SEM in resist at 117 die across a CDU wafer (i.e. a wafer where all die have the same focus and exposure dose). Each wafer location is measured twice. With this dataset the reticle and wafer LCDU, CD and placement can all be measured and correlated, and the reticle, metrology and stochastic components of the wafer LCDU can be determined. Metrology is performed using ASML Brion’s MXP to extract contours from both the reticle and wafer SEM images.

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“…Mask fabrication errors are also a major contributor to the total Edge placement error (EPE) budget and thus accurate mask metrology [12,13] is an important input to EPE budgeting and control. Since the mask, optical and resist processing effects cumulatively contribute to the wafer feature geometry, it is difficult to decompose the individual contributions from wafer metrology.…”

Section: Introductionmentioning

confidence: 99%