Aluminum Etch Uniformity is critical and difficult to achieve.

In Semiconductor and MEMs manufacturing, aluminum etch generally uses iodine-iodide, basic ferricyanide, aqua regia, or potassium cyanide. Each formulation displays its own strength and weaknesses and they all vary in speed, selectivity, stability, safety, etc. The iodine-iodide etchants are often regarded as a safe method of etching gold in terms of stability, toxicity and the overall handling.

PVD Al Etch uniformity with Spray tools is terrible.  Wafer centers have higher etch rates than edges, and incoming wafer roughness is amplified.
Generally are spaced widely apart to minimize the uniformity problem, resulting in low throughput and inefficient chemical use.

MEI has the solution for Aluminum Etch! (Plated Al Etch)!