Nanonex developed one of the first thermal imprint tools, and now also sells a combined UV and
thermal imprint system that supports align. For more go to www.nanonex.com
Obducat sells 2 thermal imprint tools for 2.5” and 6” substrates. For more go to www.nanonex.com
EVG sells modified bonders for thermal imprint and modified contact printers for UV imprint research.
The research tools involve manually assembly of the mold and substrate that are then loaded into the
bonder for imprintign. They are developing automated production tools for patterned media and
microfluidics applications that use small substrates. For more go to www.evgroup.com
Suss also sells modified bonders for thermal imprint and modified contact printers for UV imprint. For
more go to www.suss.com
Scifax www.scifax.com, Hitachi www.hitachi.com (Ogino 2004), Litho tech www.lithotech.com,
Jenoptic www.jenoptic.com, are selling thermal imprint tools.
MII has reported on a whole wafer imprint technology, but have not announced a product. For more go
CONFORM AND SEPARATE
The whole wafer tools have different strategies for molding by forcing the desired level of conformality
between mold and substrate, and separation by creating enough peel force. There are many suppliers
who have not published details. For the published solutions there are several strategies;
1) Wafer and mold conform under high pressure applied hydraulically, used by Obducat and Nanonex.
Separation performance has not been reported. Nanonex uses their “Air Cushion Press” which allows
the mold and wafer to conform eliminating any imprint variation caused by nanotopography (Li 2005)
2) Wafer conform at high pressures using a soft press with pressure transmitted through a soft pad.
Separation of 200 mm wafer has been achieved by bending the mold while imprint pressure is
applied, as reported by EVG and a team from LETI (Pelzer 2003). An initial mechanical adjustment is
required to make the wafer and mold coplanar (Islan 2002, Shaefer 2002).
3) Wafer conform at low pressures using vacuum between wafer and mold, as used in contact
printers by EVG and Suss. Supports separation by pressure between wafer and mold but appears
limited to 25 x 25 mm fields (Vratsov 2003). Pressure assistance behind the wafer has been reported
by KIMM (Sola 2004).
4) Mold conform using soft surface molds reported by AMO and others. Supports separation up to at
least 150 mm wafers.
5) Mold conform using thin hard molds reported by MII (Watts 2005) for 100 mm wafers, and VTT
(Ahopelto 2005). Supports automatic separation up to at least 100 mm.
High pressure, high temperature tools are required for thermal imprint use options 1) and 2). UV
imprinters use options 2), 3) and 4). Several suppliers have developed versions that will do both
thermal and UV imprinting by allowing the heater unit to be swapped for a UV light source.
Align is a challenge on thermal systems because the thermal tools all require the mold to be heated,
and Nickel replicas are a popular mold choice. Both factors prevent alignment by direct viewing
through the mold. As a result, in most thermal systems, the align is done offline and the wafer and
mold are vacuum clamped together. The mold and wafer are then loaded into the thermal imprinter for
molding and separation. EVG report using their 620 contact printer to align. Nanonex have developed
a tool with a built in align station. Bonders have some capability for lower performance backside align.
Align for UV tools is much simpler, the contact printer based solutions all use microscopes to directly
align through the mold. The limiting factor is usually the amount of wafer movement when the wafer
vacuum is released to allow it to conform, a well known problem in contact printers. The mold
conforming solutions would be expected to avoid this problem.
Thermal effects dominate overlay because silicon has an expansion coefficient of 10 ppm C-1 that is
10 nm per mm per C. For a 100 mm wafer 1 C produces 1 um error. UV imprint at room temperature
or thermal imprint with wafer and mold of the same material, both depend on the local environmental
control. Contact printers typically achieve low single digit micron overlay.
Nanonex have shown overlay results of 1.3 um 3 sigma over a 100 mm wafer for their imprint system
HP have reported single point align results of 3 nm using correlation of microscope images.
Most applications tools use spin on materials. CSEM have reported using drop dispense of viscous
Sol gel materials for optical functional applications. MII reported that drop dispense of low viscosity
materials can be used with thin hard templates (Watts 2005).
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Whole Wafer Tools