Improved baking of photomasks by a dynamically zone-controlled process approach

Dress, Peter; Gairing, Thomas M.; Saule, W.; Dietze, Uwe; Szekeresch, Jakob

doi:10.1117/12.438353

Cited by 7 publications

(3 citation statements)

References 6 publications

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“…PEB was carried out on an advanced precision bake system APB5000 (Steag). [2] For puddle development 2,38% TMAH solution developer was used on a ASP5500 (Steag) developer tool. For storage all blanks were kept in SMIF pods and in nitrogen purged stainless steel cabinets (NH 3 < 1ppb).…”

Section: Methodsmentioning

confidence: 99%

Negative Chemically Amplified Resist (nCAR) for DRAM Mask Fabrications

et al. 2002

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In this contribution we will demonstrate how the use of negative tone CAR can significantly improve the CD control of mask layers in which CD is measured on opaque features. A thorough investigation of the individual contributions of sequential process steps in mask making revealed that the final CD uniformity can be improved by 20 % when a negative tone resist is used. In case of 50 keV electron beam (EB) mask writing systems, that employ variable shaped beam (VSB) writing, the writing time can be reduced by 40-50 % when a chemically amplified resist (CAR) is applied. Therefore we have evaluated and characterized a commercially available negative-tone CAR. The resist showed good pattern performance down to 150 nm for isolated and semi-isolated opaque lines thus having the ability to form assist bar features. Vertical profiles have been obtained. Line edge roughness (LER) is more pronounced for this material when compared to standard EB resist ZEP 7000. But analysis of CD uniformity (3σ) of 500 nm opaque lines in local area with negative CAR and with positive tone ZEP 7000 showed 4,8 nm and 6,2 nm, respectively. Thus substantiating that the negative CAR is advantageous in terms of opaque line CD control. Regarding soft bake (SB) and post exposure bake (PEB) latitude, the CAR is stable with respect to soft bake temperature variation (3,7 nm/°C). Much more severe is the steep PEB latitude with respect to dose of 0,7-1,3 (µC/cm 2 )/°C. This requires the use of high precision baking tools for the PEB step. Since all mask blanks have been coated in-house, we have investigated a variety of pre-treatment steps. The influence of each step was characterized by contact angle measurement. We found out that the best results have been achieved when the sequence H 2 SO 4 /H 2 O 2 -cleaning -UV/ozone-clean -dehydration bake is applied to virgin blanks as delivered by the blank supplier.

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Section: Methodsmentioning

confidence: 99%

Negative Chemically Amplified Resist (nCAR) for DRAM Mask Fabrications

et al. 2002

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“…A sensor mask with 17 PT1000 temperature sensors, positioned in the center of the hotplate, is for optimizing and verifying the hotplate performance. [2] The baker has a good temperature control: 0.1℃ range at set-point time and 1℃ range during ramping time. Temperature uniformity during the ramping time may influence CD uniformity if the CARs have strong PEB sensitivity.…”

Section: Resist / Pebmentioning

confidence: 99%

Mask-making study for the 65-nm node

Chen

Lee

et al. 2003

SPIE Proceedings

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The specifications of mask critical dimension (CD) have become much tighter for sub-100nm nodes to satisfy wafer CD uniformity requirements. The small patterns produced by aggressive optical proximity correction compound the difficulty, thereby necessitating the use of e-beam writers in combination with chemical amplified resists (CARs).Challenges of resists include post coating delay (PCD), post exposure delay (PED) in vacuum, and strong post exposure bake (PEB) sensitivity. CD errors are classified into localized area and global ones; machines causing each type of errors are then identified. Focus variation and fogging effect have to be emphasized for the 65-nm requirements. Although the DOF of e-beam systems is larger than that of the optical systems, high current density and/or plate-to-plate deviation may cause focus variation to result in poor CD uniformity. Therefore, dosage optimization is necessary for getting the best focus. The fogging effective level is around 3~10 nm at various pattern loadings. The paper presents, quantitative results and the methodology leading to them.

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“…The algorithm uses feedback of 13 temperature sensors placed on the sensor mask surface in order to minimize the total temperature range which is defined as a difference between maximum of all reference temperature values and minimum of all reference temperature values. The optimization process is described in detail elsewhere [6]. As can be seen in Figure 1, the stable temperature region is reached after approximately 3 min, which depends on the chosen setpoint temperature.…”

Section: Bake Apb-5000 System and Peb Evaluationmentioning

confidence: 99%

Managing effects in CD control from PED and PEB in advanced DUV photomask manufacturing using FEP-171 resist

et al. 2005

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A continuing improvement in resist process is a necessity for high-end photomask fabrication. In advanced chemically amplified resist systems the lithographic performance is strongly influenced by diffusion of acid and acid quencher (i.e. bases). Beside the resist properties, e.g. size and volatility of the photoacid, the process conditions play important roles for the diffusion control. Understanding and managing these properties influences lithographic characteristics on the photomask such as CD uniformity, CD and pitch linearity, resolution, substrate contamination, clear-dark bias and iso-dense bias. In this paper we have investigated effects on the lithographic characteristics with respect to post exposure bake conditions, when using the chemically amplified resist FEP-171. We used commercially available mask blanks from the Hoya Mask Blank Division with NTAR7 chrome and an optimized resist thickness for the 248 nm laser tool at 3200Å. The photomasks were exposed on the optical DUV (248nm) Sigma7300 pattern generator.Additionally, we investigated the image stability between exposure and post exposure bake. Unlike in wafer fabrication, photomask writing requires several hours, making the resist susceptible to image blur and acid latent image degradation.

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Improved baking of photomasks by a dynamically zone-controlled process approach

Cited by 7 publications

References 6 publications

Negative Chemically Amplified Resist (nCAR) for DRAM Mask Fabrications

Negative Chemically Amplified Resist (nCAR) for DRAM Mask Fabrications

Mask-making study for the 65-nm node

Managing effects in CD control from PED and PEB in advanced DUV photomask manufacturing using FEP-171 resist

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