Daniel Sullivan, Thomas Boonstra, Mark Kief, Lily Youtt, Sethuraman Jayashankar, Carolyn Van Dorn, Harold Gentile, Sriram Viswanathan, Dexin Wang, Dion Song, Dongsung Hong, Sung-Hoon Gee
The lithographic requirements for the thin film head industry are comparable to the semiconductor industry for certain parameters such as resolution and pattern repeatability. In other aspects such as throughput and defectivity, the requirements tend to be more relaxed. These requirements match well with the strengths and weaknesses reported concerning nanoimprint lithography (NIL) and suggest an alternative approach to optical lithography. We have demonstrated the proof of concept of using NIL patterning, in particular Jet and FlashTM Imprint Lithography (J-FILTM) 1 , to build functional thin film head devices with performance comparable to standard wafer processing techniques. An ImprioTM 300 tool from Molecular Imprints, Inc. (MII) was modified to process the AlTiC ceramic wafers commonly used in the thin film head industry. Templates were produced using commercially viable photomask manufacturing processes and the AlTiC wafer process flow was successfully modified to support NIL processing. Future work is identified to further improve lithographic performance including residual layer thickness uniformity, wafer topography, NIL→NIL overlay, and development of a large imprint field that exceeds what is available in optical lithography.
Daniel Sullivan, Thomas Boonstra, Mark Kief, Lily Youtt, Sethuraman Jayashankar, Carolyn Van Dorn, Harold Gentile, Sriram Viswanathan, Dexin Wang, Dion Song, Dongsung Hong, Sung-Hoon Gee
The lithographic requirements for the thin film head (TFH) industry are comparable to the semiconductor industry for certain parameters such as resolution and pattern repeatability. In other aspects such as throughput and defectivity, the requirements tend to be more relaxed. These requirements match well with the strengths and weaknesses reported concerning nanoimprint lithography (NIL) and suggest an alternative approach to optical lithography. We demonstrate the proof of concept of using NIL patterning, in particular Jet and Flash™ Imprint Lithography (J-FIL™) (Imprio, Jet and Flash Imprint Lithography, and J-FIL trademarks are the property of Molecular Imprints, Inc.), to build functional TFH devices with performance comparable to standard wafer processing. An Imprio™ 300 tool from Molecular Imprints, Inc. (MII) was modified to process the AlTiC ceramic wafers commonly used in the TFH industry. Templates were produced using commercially viable photomask manufacturing processes and the AlTiC wafer process flow was successfully modified to support NIL processing. Future work is identified to further improve lithographic performance including residual layer thickness uniformity, wafer topography, NIL→NIL overlay, and development of a large imprint field that exceeds what is available in optical lithography.
As the tolerances for photomask Critical Dimension (CD) become smaller, more focus has been placed on all processes
and their contribution to final mask CD. One key contributor to final mask feature dimensions is the resist develop
process and it is the focus of this work. We have studied different resist develop methods to determine optimum process
conditions for 45 nm critical photomasks. In searching for the optimum conditions, special consideration was made to
study the influence of pattern density effects. We focused on variations in the develop nozzle. Results of the nozzles'
impact on pattern density and long range pattern density effects will be presented, for both positive and negative
chemically-amplified resists. A characterization of the repeatability of the processes will be presented as well.
As critical dimension uniformity requirements tighten for advanced technology nodes, it becomes increasingly important
to characterize and correct for systematic sources of critical dimension error in mask manufacturing. A long range
proximity effect has been previously reported in the industry to occur in chemically amplified resists that appears to be
related to the develop process and we call this phenomenon chemical flare. Several attempts to modulate this effect have
been characterized and at least one develop nozzle modification has been found to reduce chemical flare by ~50%. In
addition, develop time, develop and rinse processes, and top anti-reflective coatings have been evaluated as methods of
minimizing chemical flare effects in e-beam lithography applications. Positive and negative chemically amplified ebeam
resists have been evaluated and characterized for this effect.
Critical dimension (CD) requirements are continually tightening for mask manufacturing for mean to target and uniformity control as advanced technology nodes are introduced. In addition, the CD repeatability of structures relevant to optical proximity correction is also becoming more critical with each advancing node. Chemically amplified resists commonly in use in the mask industry are sensitive to post coat delay (PCD), storage and handling conditions, and environmental contaminants. In this paper, the CD sensitivity of a commonly used photoresist is characterized as a function of post coat delay. The impact to average CD, uniformity, linearity, thru pitch, clear to dark, and e-beam proximity effect are all examined. An analysis of post develop resist thickness loss is presented to
supplement the understanding of CD uniformity behavior. In addition, the impact of several storage scenarios is evaluated including storage in a sealed foil bag, an unsealed dry nitrogen environment, and storage boxes made from two different materials. The impact of storage conditions on CD uniformity is critical and is shown to be strongly influenced by the choice of material for the containers and the storage environment.
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