Market forecasts suggest that demand for hard disk recording media will soon reach one billion units. Fabrication of patterned media to meet this demand will require a large supply of imprint templates: The lifetime of a single imprint template is anticipated to be approximately ten thousand imprints, suggesting that two hundred thousand templates will be required to meet the demand for double-sided disk media. It is not feasible to employ electron-beam patterning directly to create this volume of templates. Instead, a “master” template – created by directly patterning with an electron-beam tool – will be replicated many times to produce the required supply of “working” templates for patterning disk media.
The master and working templates are fabricated using six inch diameter synthetic quartz substrates by applying conventional pattern transfer techniques. In the case of the working templates the master is used to imprint the working template and the pattern transfer is performed by conventional means.
Photographs of a template master with the hard mask layer still in tack. The master template was written using direct e-beam exposure on a rotary stage system. The substrate is synthetic quartz which is 6 inches is diameter.
The replication of templates can be fabricated using the same imprinting process as described above. After imprinting, a plasma-based etch process is employed to transfer the relief pattern into the fused silica. The master template was used to create a resist pattern on a template substrate. The resist pattern was etch-transferred into the underlying fused silica and the etch mask residues were stripped, thus creating a working template. Finally, the working template was used to form a DTR pattern array on a disk.
Schematic of the template replication process flow, step “1” is the master template, step “2” is a schematic of the working or replica substrate and step “3” is a schematic of the result achieved by imprinting the master template onto the working template substrate and transferring the imprinted pattern. The replication is achieved using the Perfecta™ TR1100 imprint tool which aligns the master to the working template substrate prior to imprinting. The alignment specification is 10µm.
In the SEM images below an example of two successive template replication steps for a DTR pattern with track pitch of 100nm are presented. Here, the progression from master template (top photo) to sub-master template (middle photo) to working template (bottom photo set) is demonstrated with cross-section and top-down SEM images of imprinted resist patterns. Note that the quality of the imprinted lines is essentially constant through the successive iterations of replication. The replication process has been extended below 50nm feature sizes.
SEM images of imprints of a master template (top), a first replica (middle) and a second replica made from the first replica (bottom). The feature fidelity is good through the two replication steps and the change in duty cycle associated with the each imprint step is preserved through the processing.
SEM images of 50nm pitch BPM master template imprints (left photo) and 50nm pitch working template imprints (right photo). The master template had pillars while after replication the working template had holes.
Template replication is critical for the introduction of pattern media in to manufacturing because it is the lowest cost of ownership approach to template supply for the manufacturing line.
