Specific Process Knowledge/Direct Structure Definition

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Direct Structure Definiton

Define the structure directly on your sample

By direct structure definition is meant a technique by which you create structures directly in the device material. Some of the techniques may require a master.

Choose method of structuring/equipment

• UV Lithography
• Nano Imprint Lithography
• Polymer Injection Molder
• Hot Embosser
• Laser Micromachining Tool/ablation
• Dicing saw

Comparison of equipment/material

	UV Lithography	Nano Imprint Lithography	Polymer Injection Molder	Hot Embosser	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 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 typically made in Topas, PP, PE, PS or a similar polymer. A master disk, called a shim, is usually fabricated in nickel or special aluminium alloys with the desired structures to be replicated. It is mounted in the tool of the injection moulding machine. Together they form a cavity into which molten polymer is injected. It is possible to replicate both small and large 2½D structures relatively fast. Many plastic items are made by injection molding, ranging from e.g. toothbrushes to LEGO bricks.	øø	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.
Typically used for	Optical waveguides, fluidic systems (master for PDMS/soft lithography)	??	Fluidic devices, optical waveguides, surface modification.	øø	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	TOPAS PMMA	Topas 5013L-10 Topas 8007S-04 PS (BASF 158k) Others available upon request and approval	øø	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 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 or Al, cut out to fit in the injection moulding machine.	øø	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	medium: 5-10 wafers/hour depending on imprint time	Fast: Typically 10-300 samples/hour	øø	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 - µm	nm - mm	øø	100µm - wafer size	saw blade width 60µm or 200µm. Has to cut full diameter of wafer.
Post-treatment	resist developing/baking	Dry Etch back (RIE), ?? Nano Imprint Lithography	Sprue/runner has to be broken or cut off.	øø	Sample cleaning with Ultrasound etc.	None
Patterning degree of freedom	2D	2D. different depths possible	2D. Different depths possible.	øø	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	Flat disk tool: ø50mm disc Luer tool: ø50mm disc with 12 Luer connectors Microscope slide tool: 26x76 mm2	øø	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	Depending on tool used	Nano Imprint Lithography	Nickel, aluminium, steel, FDTS	øø	Almost any	Silicon, glass, GaN, bonded wafers, LiNbO3