Thomas Roy Boonstra

An approach for nanometer trench and hole formation

Patterning trench-hole type of structures with CD in nanometer dimension is very challenging in optical lithography due to limited depth of focus (DOF) and exposure latitude (EL). We have proposed an integration process to convert sub- 100nm line/post type of structure to trench/hole type of structure. The proposed method as well as its variations may have various potential applications, such as formation of plated perpendicular magnetic writer pole, bottom-up nanointerconnect, nano-wires and other out-of-plane nano-structures. We have shown the feasibility for formation of nanotrenches in various sub-100nm dimensions. Magnetic writer pole with 50nm critical dimensions (CD) and wellcontrolled sidewalls was demonstrated by using this approach. The minimum CD of the starting isolated line/post feature determines the minimum CD of the trench/hole structure.

Hard disk drive thin film head manufactured using nanoimprint lithography

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.

Dual freelayer reader for improved linear density

The Bottom Spin Valve (BSV) geometry has been the standard HDD Reader design for well over 10 years [1].

Comparative investigation of CD-SEM carryover effect

Aggressive roadmaps impose stringent requirements not only on the metrology tools but on photoresist properties as well. In this article we investigate the interaction between electron beam in a CD SEM and different photoresists in an attempt to determine appropriate candidates from metrology point of view. We have evaluated sample damage (carryover) in order to find an approach leading to reduction of the sample degradation in the course of the measurement process and improve measurement precision. We have observed various linewidth changes under conditions expected in the case of single-tool repeatability, stability or multiple-tool matching procedures for CD SEM. The experimental data show that while all examined photoresists experienced certain changes some of them demonstrate less sensitivity. For modern CD SEM in addition to electron energy and current as factors defining the carryover, the possible effect of the clean room environment exposure should be considered as well. Recommendations have been made with respect to acceptable compromise based on the current precision requirements.