Dropping ECD’s heavy baggage

By Debra Vogler

WaferNews Technical Editor

NuTool engineers have shown that overburden associated with conventional electrochemical deposition (ECD) can be reduced from 500 to 2,000nm to 100 to 500nm using the company’s electrochemical mechanical deposition (ECMD).

As a result of the significant decrease in unneeded copper deposition, the company expects the associated cost-of-ownership (COO) of CMP to be reduced $7 to $15 from its typical range of $12 to $35 per wafer. In addition to having less material to remove, the savings would come from improved yield due to reduced erosion and dishing.

“The ECMD process provides a greater level of planarity before the CMP process even begins,” stated Brian Stickney, director of sales and marketing at NuTool. “It achieves global planarity and local planarity. In many cases, the user of the ECMD process starts out with better planarity before CMP than could be obtained after CMP if conventional ECD had been used. Customers typically see equal or superior electrical performance of the die with a reduction in CMP COO that ranges from 40 to 60% before process optimization. At a minimum, ECMD provides equal results to ECD copper deposition with a significant cost reduction for copper CMP.”

Because dishing and erosion add variation to the electrical performance of a device, achieving a highly planar film enables uniformity of performance. Interestingly enough, NuTool believes its ECMD process could be a market buster for CMP. “If the overburden is low enough, a wet process can be used instead of CMP,” commented Stickney.


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