[mems-talk] KOH etching

[LSujatha]

Dear friends,
When I am doing KOH etching of Silicon with silicon dioxide mask in 30% 
solution I am getting the black color in the place of silicon to be etched 
and hence the etching starts very late. the etching time becomes almost 
twice.Can anyone tell the reason for this black color formation? How to 
avoid?
Temperature is 75 degrees Centigrade.
Suggestions please.