I'm wire bonding from gold pads (typically 30 - 100 nm thickness) that are patterned on a 300nm thermal oxide (silicon oxide) substrate. The force that I typically use in wire-bonding is ~200 - 350 mN for a few hundred ms. I'm noticing some possible shorting between my gold pads which are separated by 100um to nearly 1cm. Is it possible to short through 300nm of silicon oxide at
Yes it'is indeed a possibilty. To avoid this you dhould try smoother wirebonding paramaters and use a bonding wire of the same material thanl the bonding pad.
Hope that help...
Dan
Even if shorting due to wedge bonding is very common, the effect is usually observed in transverse geometry (i.e. between top and bottom electrodes, isolated by a thin oxide layer). If I understand properly the question, the short you describe occurs between well-separated planar electrodes. In this case, I would rather: (1) check the quality of the silicon oxide layer. Sometime, oxygen plasma treatment (performed before patterning the electrodes) helps; (2) check the lithography steps, in particular in the case of chemical etching (skip this steps if Au pads are grown following a liftoff process); (3) If steps (1) and (2) are not conclusive, I would use a different wire bonding scheme, called ball bonding. Modern wire bonding machines allows for switching easily between wedge and ball bonding methods. The latter is known to be less aggressive, and it solves in most cases s/c problems.
Best of luck! S.
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