Hi,

I have a multilayerstructure 5nm Cr / 50 nm Au / 100 nm SiO2 / 5 nm Cr / 50
nm Au on the nitridized silicon substrate.
I'm trying to wet etch through all layers using PMMA-mask.
Au-layer is etched with (4g KI : 1g I2 : 20 ml H2O) and Cr with (50g NaOH :
90 g K3Fe(CN)6 : 400 ml H2O) solution.
These steps seems to work almost fine, except a little undercutting (or PMMA
stripping in edges).

Something bad is happening during BHF etching of SiO2-layer, because it
seems (with microscope) like the ething solution goes somewhere
between the layers. Could it be the adhesion problem in SiO2 attaching to
underlying Au-surface. Should I use Cr also after first Au-layer?


Regards,

Sampo Tuukkanen