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I have been trying to plate Copper on Copper sputtered Electronic grade Silicon Substrate which has been patterned and developed using UV photolithography. The patterns measure about 50-100microns in width and are about 1600microns long. I have tried plating 10micrometer thick Cu using a stock solution of CuSO4. Even several hours after my estimated plating time,no deposits are formed. I estimated the required plating time using Faradays law of electrolysis [t=mFZ/IM]. My last try was with a fixed voltage of 0.03V and the current steadily rose from 0.01mA up to approximately 0.025mA. However when I use large current, tens of mA approximately, flaky deposits form instantly (I want a smooth firm deposit). I have two deposition modes available, constant current and constant voltage. Both of which I can specify down to the nano range. I tried the following to solve the problem they all didnt work out.
1)Coat the sides of the Silicon substrate with photoresist to prevent any prefrential plating on the edges.
2) Ensured that there was connectivity between electrodes and clips.
3) Ensured that the circuit was closed when the substrate was immersed in the electrolyte.
4)Provided adequate agitation.
5)Checked the resistivity of the electrolyte to ensure that the chosen current, in the region of 20mA can flow through the solution at a selected voltage in accordance with Ohms law.
6)Calculated the required plating area and subsequently the current density.
7)I have diluted my electrolyte infinitely to plate at a higher voltage and lower current (didnt work out solution was still highly conductive).I still can't seem to figure out where I have gone wrong.Any suggestions please.
1)Coat the sides of the Silicon substrate with photoresist to prevent any prefrential plating on the edges.
2) Ensured that there was connectivity between electrodes and clips.
3) Ensured that the circuit was closed when the substrate was immersed in the electrolyte.
4)Provided adequate agitation.
5)Checked the resistivity of the electrolyte to ensure that the chosen current, in the region of 20mA can flow through the solution at a selected voltage in accordance with Ohms law.
6)Calculated the required plating area and subsequently the current density.
7)I have diluted my electrolyte infinitely to plate at a higher voltage and lower current (didnt work out solution was still highly conductive).I still can't seem to figure out where I have gone wrong.Any suggestions please.