Some parts of the chip (5x5mm) are ~70nm deep, whereas other parts are ~470nm deep. Details:
ST-cut quartz was etched in BOE HF (1:1) solution for 10min at room temperature. Prior to etching some samples were rinsed in DI water to improve wetting. Cr/Au structures served as hard mask during etching. Target trench depth is 100-150nm.
What could be the reason for non-uniform etching? What is the etch rate of ST-cut quartz in HF (or other solutions) in your experiments?
Hello Aidar, how do you rinse your sample when you stop the etching ? maybe the convection was not good enough
Hi Laura,
Thanks for your reply. I rinse (just dip) my samples in water for 10 min. I have suspended structures after ecthing, so I can not really agitate the water.
Hi Aidar,
Quartz etch rates in HF contained solution are strongly depended on its crystal orientation, so the bottom of the etched structures is not at the same height if the opened windows are not identical.
Please see Figure 4 from this article for what I meant.
http://robotics.eecs.berkeley.edu/~pister/147fa15/Resources/anisotropic%20Quartz%20etching%20in%20HF.pdf
So make sure that you measure the etch depths at identical structures (same opened dimensions and same orientations).
Hien
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