The TMAH in the developer is what attacks the metal. Almost all developers
including the ones from AZ developers contain TMAH. TMAH is the active
ingredient; and most developers contain 3-4% TMAH.  I seem to remember pure
Al etches about 10 times faster than Al-Cu. That is one reason why pure Al
is not usually used for metal layers in semiconductors.

Robert

-----Original Message-----
From: galindo818@aol.com
Subject: Re: [mems-talk] 319 developer while protecting Al

Zhaoyan,

Have you tried using AZ developer? there's also a company called Clariant.