Research Academics  
 
   
 

High Precision V-Groove Etching in {100} Silicon:
 

Contact Person : Dr.-Ing. Ha-Duong Ngo

 

Introduction

Due to the non-zero etch rate of the {111} planes the effective side wall angle g deviates from the crystallographic 54.74°. For precise V-groove etching (e.g. in microoptics) a stable anisotropy ratio of 150 can be achieved by inert gas bubbling of very pure KOH, precise process control and <110> alignment of a thin LPCVD-Si3N4 etchmask.

  

Precise KOH etched V-grooves for wave guide devices (left, schematic) and SEM cross section photograph (right). An angle deviation Dg of 0.02° leads to a fibre shift of 0.05 µm causing considerable performance losses in optical coupling.

Double wall etch vessel (fused silica) with reflux condensor and N2 inlet to protect the KOH from atmospheric oxygen. DT = +/- 0.01 K