ADVANCING REAL-TIME DRY SILICON TRENCH ETCH-DEPTH MONITORING IN MEMS APPLICATIONS

ADVANCING REAL-TIME DRY SILICON TRENCH ETCH-DEPTH MONITORING IN MEMS APPLICATIONS

ABSTRACT:

This article discusses the TDM-200 polarimetric camera from Jobin yvon, Horiba group(longjumeau,France),which performs in situ control of DRIE silicon trench etch depth in MEMS manufacturing.

After morethan 20 years of development by a host of R&D laboratories around the world, microelectro- mechanical systems(MEMS) have evolved to support a maturing, commercially successful industry. Mems have finally achieved their long promised potential as a disruptive technology.

A key process used to fabricate many Mems devices is deep reactive-ion etching(DRIE) of silicon, which enables the creation of vertical trenches or holes that are typically in the 10 to 750 micrometers range.These deep trenches define the three dimensional micro structures comprising the Mems device. A widely used DRIE method is the bosch process which was patented by Robert bosch,Germany in 1994 and then licensed to surface technology systems(STS) in imperial park, Newport ,U.K.

To improve production yields in Mems fabrication, it is essential to etch 3-D Mems structures to a consistent depth of wafer after wafer ,requiring a high level of contol.However, after the event ex situ control of etch depth is expensive.To achieve adequate real time depth control without the need for ex situ metrology,Advanced in situ metrology,fed back into processing software is required to terminate the etch process at the correct depth and hence obtain the required featured profile.

Depth monitoring becomes ever more challenging as the structures required for Mems devices deepen and their aspect ratios increase.

This article also gives the details of the tests that were performed by STS to characterize the camera, demonstrating its ability to improve process control in a range of applications.


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