Specific Process Knowledge/Direct Structure Definition

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Direct Structure Definiton

By direct structure definition we mean that you form the structures for you device directly in the material that the device consist of without any masking steps. Some of the techniques may require a master.

Choose method of structuring/equipment

• UV Lithography
• 2-Photon Polymerization Lithography
• Nano Imprint Lithography
• Polymer Injection Molder
• Laser Micromachining Tool/ablation
• Dicing saw

Comparison of equipment/material

	UV Lithography	2-Photon Polymerization Lithography	Nano Imprint Lithography	Polymer Injection Molder	Laser Micromachining Tool	Dicing saw
General description	The device is typical made in a thick film (10-100µm thick) of a polymer (SU-8) that is spun on a carrier (silicon wafer). This film is exposed through a mask and then developed and possible cured to make the polymer harder.	The device is typical made in a thick film (1-10µm thick) of a polymer (SU-8) that is spun on a carrier (silicon wafer). This film is exposed by two intersecting laser beams in the system. Where the beams intersect the film polymerize and becomes less solvable. It is possible to form very small 3D structures	The device is typical made in a thick film (1-10µm thick) of a polymer that is spun on a carrier (silicon wafer). A master with the desired pattern is pressed into this film and the film is hardened by heating or UV-exposure. A residual layer has to be etched away by dry etching. It is possible to form very small 2½D structures over large areas relative fast.	The device is typical made in TOPAS or a similar polymer/plastic. A master disk of e.g. Nickel, called a shim, with the desired pattern is mounted in the tool of the machine and they form together a void where the melted plastic is injected into. It is possible to form small and large 2½D structures on the chosen shape (determined by the tool) relative fast. As an example Lego building blocks are made by polymer injection molding.	The device is made using a series of short, high intensity light pulses to engrave a pattern in almost any material. Since the light pulses are very short (100ns or 10ps) the heating of the sample can be minimized, and material can be removed without any further sample deformation/melting.	The dicing saw is mostly used to seperate a silicon/glass wafer into individual chips. It can however also be used to make straight channels in glass/fused silica for e.g. fluidic components.
Typical used for	Optical waveguides, fluidic systems (master for PDMS/soft lithography)	Photonic bandgap structures	??	Fluidic devices, optical waveguides, surface modification.	Cutting Silicon and glass wafers in odd shapes, shim cutting, shim patterning, surface modification, hole drilling in glass/silicon etc.	Cutting Silicon and glass wafers in rectangular shapes, making straight channels in glass wafers.
Processable materials	SU8 AZ resists	SU8 AZ resists	TOPAS PMMA	TOPAS	Silicon Metal sheets Graphene (on silicon) Glass (Pyrex, fused silica) TOPAS PMMA ...	Silicon Glass (Pyrex, fused silica)
Prerequisites	Sample with resist. A glass mask with desired pattern. For mask layout software see Mask design	Sample with resist. A 3D CAD model file in GWL format. Included software can convert 3D model in STL (Standard Tessellation Language) format to GWL files.	Sample with polymer. A stamp with the wanted pattern, usually in Si or SiO\rm{_2} however other materials could also be used.	A stamp/shim with the wanted pattern, usually in Ni og Al.	A 2D CAD model file in DXF or CONX format. Clewin5 can convert GDS and CIF files to DXF format.	Number of lines and pitch in each direction. Your wafer.
Throughput (when mask/stamp/pattern available)	medium: 5-10 wafers/hour depending on exposure time	slow: 1 sample/day	medium: 5-10 wafers/hour depending on imprint time	fast: 10-100/hour	medium-slow: 0.1-1 wafers/hour depending on pattern complexity	medium: ½-3 wafers/hour depending on material and # of cuts (Si cuts at 5mm/s, SiO2 at 0.5-1 mm/s)
Min/max featuresize	1µm - wafer size	100nm - mm	100nm - µm	nm - mm	100µm - wafer size	saw blade width 60µm or 200µm. Has to cut full diameter of wafer.
Min/max aspect-ratio	NA	2-Photon Polymerization Lithography ??	Nano Imprint Lithography ??	Polymer Injection Molder ??	50-100µm width/~1mm depth, sloping walls	60µm width/2mm depth, vertical walls
Post-treatment	resist developing/baking	resist developing/baking, ?? 2-Photon Polymerization Lithography	Dry Etch back (RIE), ?? Nano Imprint Lithography	None, ??Polymer Injection Molder	Sample cleaning with Ultrasound etc.	None
Patterning degree of freedom	2D	3D	2D. different depths possible	2D. different depths possible	2D. different depths possible	1D. different depths possible
Sample sizes	small samples 50 mm wafers 100 mm wafers 150 mm wafers	small samples 50 mm wafers 100 mm wafers 150 mm wafers	small samples 50 mm wafers 100 mm wafers	flat disk tool: , luer tool:	small samples 50 mm wafers 100 mm wafers 150 mm wafers larger samples	small samples 50 mm wafers 100 mm wafers 150 mm wafers
Allowed materials	UV Lithography	2-Photon Polymerization Lithography	Nano Imprint Lithography	Polymer Injection Molder	Laser Micromachining Tool	Dicing saw