Embossing Nanotechnology
"Nanoimprinting" uses nanoscale patterns to stamp or print designs on chip surfaces. The technique is being developed to create subwavelength optical elements for use in optical communication devices. The company is also looking at applications in BioMEMS and nanotechnology.
Currently there are three imprint lithography methods for transferring the image of the nanostructures into a polymer layer - embossing, stamping and moulding. These techniques can be used either at wafer level when only a single level is required or at chip or larger area level when several layers with accurate overlay is needed.
One of SUSS MicroTec's tools uses stepper technology and the other two apply different embossing techniques. The tools are the FC 150 device bonder, the MA6 mask aligner and the SB6 substrate bonder.
Hot embossing at the chip or larger area level is called step and print. Cold embossing (also called soft lithography) is referred to as step and flash. These techniques can be implemented using a properly configured device bonder (flip-chip bonder) in a step and print or step and flash method. At wafer level, cold embossing is achieved with an adapted contact printing mask aligner. Hot embossing is achieved with a substrate bonder, which is commonly used for micro-electro-mechanical system (MEMS) manufacturing.
The device bonder is used for a submicron alignment process similar to an optical stepper at the chip or larger area level. The tool uses UV curing technology (a photochemical process by which monomers harden or cure upon exposure to ultraviolet radiation) with a localised exposure area of 15-20mm2, at a wavelength of 365nm and an intensity of more than 100mW/cm2. UV curing can also be replaced by a heating tool to perform hot embossing in a step and print mode.
The mask aligner was designed to produce optimal results for single or double sided embossing of micro-optical elements. This provides aligned single- or multi-layer wafer level cold embossing. The embossing uses a newly developed hybrid inorganic polymer called Omorcer. The MA6 is capable of printing resists from less than 0.1microns to a few 100microns thick at a resolution of less than 0.1micron. Top or bottom side alignment and specific UV curing wavelengths can also be selected.
The substrate bonder can provide hot embossing at low cost. It works in controlled atmospheres with a high bond force of up to 9kN and a temperature range up to 550C. If alignment is needed a transport fixture can provide an interface between the aligner and the substrate bonder.
