Article posted on Aug 16, 2018

Inspecting Unpatterned Wafers

from Semiconductor Engineering

Unpatterned wafer inspection, which has flown well under the radar for most of the semiconductor industry, is becoming more critical amid the need to find defects earlier in the manufacturing process flow.

Finding those defects is getting harder as critical dimensions shrink. It’s more difficult to actually detect smaller defects on bare wafers, there is more data to process, and there is more pressure to process and inspect more quickly. And while there are solutions to all of these problems, there is a cost associated with each of them.

Generally, wafer inspection is split into two categories—unpatterned and patterned. In simple terms, unpatterned wafer inspection looks for defects on unprocessed or bare silicon wafers. Patterned inspection detects defects on processed wafers. Hitachi High-Technologies, KLA-Tencor, Rudolph and others compete in the unpatterned wafer inspection equipment market in one form or another.

Unpatterned wafer inspection tools are used in various parts of the IC production flow, including the initial stages of the semiconductor process. In the early stages, silicon wafer makers produce and sell bare or unprocessed silicon wafers to chipmakers, who process them into chips in the fab.

But before silicon wafer makers ship the substrates to chipmakers, the bare wafers must have few or no defects. Intrinsic defects on bare wafers eventually can lead to killer defects on the final chips.

That’s where unpatterned wafer inspection fits in. 

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