STS APS DGRIE/Processes/Fused silica etch

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About this Process
Process Details
Technology DRIE
Material Fused silica, Pyrex
Mask Materials KMPR, SU-8, polysilicon
Gases Used C4F8, He, H2
Date Created 7/1/2012
Authored By Kevin Owen

The Fused silica etch is designed for deep etching of fused silica and quartz substrates. Etch rate up to 5000 Å/min, depending on feature size. The etch has been tested up to 50 μm depth in 20 μm and larger features. This process generates a tremendous amount of heat and cannot be used with standard photoresist. KMPR and polysilicon are the recommended mask materials.


Follow the SOP as shown on the STS APS DGRIE page using the Fused Silica Etch and the Extended Etch Batch.


Etch/Dep Rate

Etch rate is feature size and depth dependent. Smaller features will etch slower than larger ones and higher aspect ratios will also etch slower. Bulk etch rate is approximately 5000 Å/min. The etch exhibits minimal loading effect.



Mask selectivity

The selectivity of fused silica to KMPR is approximately 4:1 for shallower etches, decreasing with depth.


Etch time

The etch may be run for a maximum of 2 hours before an extended O2 clean must be run on the chamber.

Etch depth

A 2 hour etch will yield approximately 45-50 μm depth depending on feature size on a fused silica substrate. The etch has been tested for up to 8 hours, but due to challenging lithography and the necessary extended cleans we do not recommend this process.

Substrate material

The above etch rate is based on a fused silica substrate. Glass and pyrex substrates may etch slower and produce a rougher surface due to impurities in the material.