Plating uniformity is quite complicated issue. It is related to current
density distribution.
Except plating current and pulse plating( Mike & Patrick' E-mail), there are
many other aspects which will contrubite to uniformity(assume we are talking
about wafer plating).
1. plating type and additive(electrochemical effect), for example, Copper
plating uniformity is better than Nickel. This is because of different
electrochemical polarization. Usually, larger polarization, better uniformity.
So if  there is no special requirement, select plating type with good
uniformity.
2. Geometrical effect, such as plating tank, anode shape and location. In
copper plating for semiconductor interconnect, people are using "Cup" shape
tank for better uniformity.Semitool, Applied Material are making this kind
tool.
3. load effect, this is similar to dry etching. So when you design plating
mask, you need consider this effect. So called "thief plating" is based on
this effect.
4. Seed layer for current conduction.

Message: 1
Date: Wed, 23 Jan 2002 09:40:19 -0600
From: "Mike Mattes" 
To: , 
Subject: Re: [mems-talk] very uniform surface of elctroplated Nickel ?
Reply-To: mems-talk@memsnet.org

sz,

My experience indicates that there are two relatively easy things to do:

1. Lower the current, which will make plating slower, but smoother.
2. Use pulse-plating with a short negative pulse to knock off the peaks.
(This
is probably the same technique that Patrick Cheung called
Reverse-electroplating.)

Finding the optimum settings, however, could take some effort.

Best Regards

>>> pcheung@parc.xerox.com 01/22/02 02:53PM >>>
sz,

I was told about a procedure called Reverse-electroplating that
takes advantage of the properties that high points erode faster
to smooth out a metal coating. However, I have not personally
tried that procedure so I cannot say to what extent it
performs. You can research in that direction to see if you can
use it.

Good luck,

Patrick Cheung, research scientist         PARC, MS 35-1674
(O) 650-812-4338 (FAX) 650-812-4334   3333 Coyote Hill Road
pcheung@parc.xerox.com                  Palo Alto, CA 94304
           "pcheung can mems, and so can you!"
>>                                                       >>

On Sat, 19 Jan 2002, [iso-8859-1] sou zou wrote:

> From: "[iso-8859-1] sou zou" 
> To: "mailing list (MEMS talk)" 
> Date: Sat, 19 Jan 2002 05:00:33 PST
> Subject: [mems-talk] very uniform surface of elctroplated Nickel ?
>
> Hi folks !
>
> I am looking for some advices to get a very uniform surface
> of nickel electroplated layers (especially on silicon).
> Through my bibliography research, it seems that the trick is
> mainly to get an uniform current density across the coated
> surface (parallel current lines). The problem is the resist
> pattern wich does'nt allow to obtain that kind of strictly
> vertical current lines. Does anyone has an ingenious idea or
> a good web address to help me overcoming such a problem,
> please ?
>
> Thank you in advance,
>
> sz