Height measurement of wafer bumps


Computer chips are manufactured in large quantities on a wafer. On the chips there are countless small, spherical contact surfaces, so-called bumps. These must be of a uniform height in order to function properly when stacked later. Confocal sensors from Micro-Epsilon determine the height of the wafer bumps with micrometer precision in the production line.

Confocal chromatic sensors from Micro-Epsilon measure precisely on the shiny and structured surfaces of the computer chips. Thanks to the focused light spot, a high lateral resolution of around 4 µm is also achieved. For inline monitoring, three confocalDT IFS2405 sensors are positioned slightly offset above the wafer. This generates three tracks on one bump. From the three tracks, both the spherical shape and the height can be calculated exactly. The controllers are connected via Ethernet and trigger input and perform a synchronous measurement. Therefore, the height of the wafer bumps can be measured with micrometer accuracy. The encoder value is also fed into the motion unit.

In order to be able to measure the large number of chips and thus also the bumps in the shortest possible time,confocal sensors from Micro-Epsilon offer an extremely high measuring rate up to 70 kHz.

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