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Difference between Bulk and Surface Micromachining?

written 6.8 years ago by gawanderagini • 50

modified 2.8 years ago by sagarkolekar ★ 11k

mems technology

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written 5.8 years ago by teamques10 ★ 69k

•   modified 5.7 years ago

Sr No	Bulk Micromachining	Surface Micromachining
1	In this mechanical elements are fabricated by etching away the unwanted part in silicon wafer	In this it is fabricated by building layers on layers
2	This creates structures inside a substrate	This creates structures on top of a substrate
3	Larger structures are made with bulk micromachining	It is difficult to build larger structures
4	Limited to low aspect ratio in geometry as surface dimensions are much greater than depth as height is limited by thickness of silicon wafer	Not constraints by thickness of silicon wafer,so high aspect ratio geometries can be fabricated using surface micromachining
5	Straight forward and well documented process	Complex masking design and production
6	Sacrificial layer is not required	Etching of sacrificial layer is required
7	The process is less expensive but material loss is more	The process is expensive but less material loss
8	Mechanical properties are superior	Mechanical properties are good
9	Dimensional control is good	Dimensional control is better
10	CMOS integration is fair	CMOS integration is good
11	It causes a well known phenomenon in the micro electronics industry called undercut	It does not causes undercut problem
12	Size is small	Size is smaller
13	Typically uses wet etching techniques	It uses dry etching techniques
14	Suitable for simple geometry such as thermal sensor,micro machined neuron wells	Suitable for complex geometry such as micro valves and actuators

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