Step and flash imprint process integration techniques for photonic crystal patterning: template replication through wafer patterning irrespective of tone
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Photonic crystal structures in for example light emitting diodes (LED) have been demonstrated to improve performance by preferential mode coupling near the surface of the diode.1 Such demonstrations were limited by using direct write e-beam lithography due to long write times, a single tone and only small areas patterned for study. S-FIL technology provides a means to pattern entire wafers in a single imprint step using templates replicated by step and repeat (S&R) imprint2. Large area template replication by S-FIL/R has been described using S&R templates3. Photonic crystal based LED manufacturers prefer holes in substrates requiring pillar tone templates for S-FIL patterning. Pillar tone templates are not easily derived from the preferred e-beam tone for sub-200 nm template fabrication. Therefore step and repeat and/or whole wafer template replication by the combination of S-FIL and/or S-FIL/R can be used to produce the desired working template tone. These processes further enable the desired tone and wafer die layout for fully patterning wafers to their edge with no missing die or edge fields. The advantages of using S-FIL processes for template and wafer patterning are clear in that there is no tone preference required by the original e-beam generated pattern, which allows the preferred positive tone to be used for e-beam patterning of templates. The present work will describe template replication processes for the fabrication of either pillar or hole tone templates and subsequent wafer pattern processes, through oxide hard mask, producing both pillar and hole tone patterns. In summary process flows exist so that any e-beam written template tone can be used to produce either tone in replicated templates and/or patterned wafers.
[1] S. Chou,et al. Nanoimprint Lithography , 2010 .
[2] Dong Li,et al. III-nitride LEDs with photonic crystal structures , 2005, SPIE OPTO.