Thanks for the responses.

>
> Are you using BOE with surfactant?

Shay - I'm not using any surfactant. Can you explain how the surfactant would
affect the diffusion-limiting conditions? Or do you suspect that my problem is
instead due to poor wetting of the surfaces in these deep pits, which
surfactants would definitely address.

Would you recommend any particular surfactants - would something like Tween or
Triton X-100 be suitable, or is a specialized surfactant necessary?

Also to address the potential wetting problem, I'm considering wetting the wafer
with IPA before putting it into the BOE bath.

Best regards,
Ken