An Introduction to mems (Micro-electromechanical Systems)

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weakened.  On developing, the rinsing solution removes either the exposed areas or the 

unexposed areas of photoresist leaving a pattern of bare and photoresist-coated oxides on the 

wafer surface.  The resulting photoresist pattern is either the positive or negative image of the 

original pattern of the photomask. 

 

Figure 17.  Photoresist and silicon dioxide patterns following photolithography [28]. 

A chemical (usually hydrochloric acid) is used to attack and remove the uncovered oxide 

from the exposed areas of the photoresist.  The remaining photoresist is subsequently 

removed, usually with hot sulphuric acid which attacks the photoresist but not the oxide layer 

on the silicon, leaving a pattern of oxide on the silicon surface.  The final oxide pattern is 

either a positive or negative copy of the photomask pattern and serves as a mask in 

subsequent processing steps. 

At this point MEMS diverges from traditional IC fabrication.  In processing IC devices, the 

or phosphorous) that alter the local conduction necessary for microelectronic devices.  In 

MEMS, the oxide serves as a subsequent mask for either further additional chemical etching 

creating deeper 3D pits or new layers on which to build further layers, resulting in an overall 

3D structure or device.