What's the simplest way to etch Nickel and Chromium sputtered layers? I have to etch a very thin film (50 nm) of Nickel ($\ce{Ni}$) on a 100 nm $\ce{SiO2}$/$\ce{Si}$ substrate. Additionally, there is a ~5 nm adhesion layer of $\ce{Cr}$ under the $\ce{Ni}$ that I'd also like to etch.

So I found this page which has a fairly long list of etches for $\ce{Ni}$ and $\ce{Cr}$.

Ni:


1 : 1 : 1 - HNO3 : HAc : Acetone
1 : 1 - HF : HNO3
30% FeCl3
3 : 1 : 5 : 1 - HNO3 : H2SO4 : HAc : H2O 85 C 10 microns/min
3 : 7 - HNO3 : H2O
1 : 1 - HNO3 : HAc
10% g/ml Ce(NH4)2(NO3)6 : H2O
HF, concentrated – slow etchant
H3PO4 – slow etchants
HNO3 – rapid etchant
HF : HNO3 – etch rate determined by ratio, the greater the amount of HF the slower the reaction
4 : 1 - HCl : HNO3 – increase HNO3 concentration increases etch rate
30% FeCl3
5g : 1ml : 150ml - 2NH4NO3.Ce(NO3)3.4(H2O) : HNO3 : H2O – decreasing HNO3 amount increases the etch rate
3 : 3 : 1 : 1 - H3PO4 : HNO3 : CH3COOH : H2O ~15min/micron @ RT with air exposure every 15 seconds



Cr:


  2 : 3 : 12  KMnO4 : NaOH : H2O
  3 : 1   H2O : H2O2
  concentrated and dilute     HCl
  3 : 1   HCl : H2O2
  2 : 1   FeCl : HCl
      Cyantek CR-7s (Perchloric based)    7 min/micron (24A/s new)
  1 : 1   HCl : glycerine     12min/micron after depassivation
  1 : 3   [50gNaOH+100mlH2O] : [30g K3Fe(CN)6+100mlH2O]   1hr/micron 


I'd really like to avoid HF if I can (it terrifies me!), but I have pretty much everything else at my disposal.

So far, everything I've done has been at room temperature.

First I tried concentrated $\ce{FeCl3}$. No bubbling or signs of anything after ~20min.

Then I tried weak $\ce{H3PO4}$. Nothing.

Today I tried strong (98%) $\ce{H3PO4}$, nothing.

Then I tried concentrated fuming $\ce{HNO3}$. Nothing after ~1hr.

Then I tried about 1:1 $\ce{HNO3}$:$\ce{HCl}$, nothing.

Am I missing something here? Do the solutions need to be heated up or something?
Nickel can be etched using diluted (1:1 V) $HCl$. 50 nm will be dissolved within seconds. 

The etching solution for the chromium layer contains $\ce{Ce(NH4)2(NO3)6}$+$\ce{CH3COOH}$+$\ce{H2O}$
in ratio 165g : 45 ml (con.) :100 ml DI water. The chromium layer is dissolved within 5 minutes of etching.