Mark:

It's to see that people are finally starting to admit that the free acid in cupric chloride
causes problems with dry film. It also causes problems with undercutting and irregular sidewalls.
The solution to the problem is to use a controller and compatible chemistry that works with ZERO
free acid, etching only with pure cupric chloride. While I know that no one wants any ads placed
here, if any are interested in an off-line discussion of this topic, please contact me by e-mail
at:

[log in to unmask]

Automatic digest processor wrote:

> Date:    Tue, 13 Jan 1998 19:43:30 EST
> From:    Dryfilm <[log in to unmask]>
> Subject: Re: Organic residue in cupric chloride fina
>
> Ted,
> I wholeheartedly agree with the suggestions given so far.  I've experienced
> this very problem in production; it can be difficult to resolve.
>
> The problem is caused by acid attack on the photoresist.  While I don't
> usually see it unless normality is run very high (>2.8), it is possible for
> the "scum" to build up over time.  All of the suggestions so far (reduce
> antifoam in developer, maximize developer rinsing, dry layers between develop
> and etch, carbon filtration) will help reduce the buildup.  If the problem is
> severe, you may need to completely dump the etcher, clean the machine, and
> start over with fresh solution.
>
> It is also helpful to maximize your developing process.  Do some SEM studies
> of the sidewall.  Soft, partially polymerized resist left on the sidewall is
> susceptible to attack in the etcher.  Optimizing development can help make up
> for less than perfect rinsing and drying.
>
> One other thing to check is the ventilation system on the DES line.  In some
> shops, I have seen vent pipes from the etcher and the stripper join together
> at a main duct.  Sometimes, condensed vapors build up in the ducts, and
> polymer laden material drips back down the sides and into the process
> equipment.  You are then adding back the very material you want to remove.
> Good luck.
>
> Mark Dowding
> Regional Technical Service Manager
> INSULECTRO
>

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