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SUMMARY:Selective ablation of Titanium-Tungsten (TiW) thin film using Nd:Y
 AG laser for prototyping of MEMS devices - Ibraheem Haneef\, High Voltage 
 Microelectronics (HVM) Group\, CAPE\, Department of Engineering
DTSTART:20080129T160000Z
DTEND:20080129T170000Z
UID:TALK10247@talks.cam.ac.uk
CONTACT:Joshua En-Yuan Lee
DESCRIPTION:Low volume fabrication of MEMS structures by using conventiona
 l photolithography is expensive\, tedious and time consuming.  In initial 
 design and prototyping phase of MEMS devices\, laser micromachining provid
 es a much faster\, flexible and easier alternative that has a significantl
 y low operating cost. Laser ablation may not only be used to cut through t
 hick support layers (e.g. silicon nitride with thickness of the order of m
 icro-meters) to shape MEMS structures\, but also to selectively remove thi
 n metal films (with thickness of the order of nano-meters) from these stru
 ctures for formation of electrodes.\n\n      This talk will focus on explo
 itation of laser micromachining for selective removal of Titanium-Tungsten
  (TiW) thin film from Silicon Nitride (SiN) support layer for fabrication 
 of MEMS thermal flow sensors.  Micromachining performance was evaluated in
  terms of patterning quality and the ability to remove TiW with minimal da
 mage to an underlying SiN layer.  Two types of samples were micromachined 
 using single shots of UV (355nm) and green (532nm) radiation of a Nd:YAG l
 aser.  One type of samples had only a 3 µm SiN layer on Si substrate whil
 e the others had another layer of 500 nm DC magnetron sputtered TiW on top
  of SiN.  The effect of laser fluence and number of shots on the laser-mac
 hined features was investigated using surface profilometry\, 3D optical in
 terferometry and scanning electron microscopy.  The average and maximum re
 moval depths of both TiW and SiN layers at various numbers of laser pulses
  and fluence levels were characterized to find an optimum laser fluence ra
 nge and laser fluence value for selective removal of TiW layer without dam
 aging the underlying SiN layer.  To determine the point of complete select
 ive removal of TiW film from SiN\, in-situ electric resistance was measure
 d during single shot laser ablation of TiW film on dog-bone structures.  M
 eander shape micro-patterns on Ti-W film on free standing SiN micro-bridge
 s have been successfully fabricated using this technique. These structures
  have their application as micro-heaters and MEMS thermal flow sensors.   
LOCATION:CAPE building seminar room 21-23. 9 JJ Thomson Ave. CB3 0FA
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