IWLPC (Wafer-Level Packaging) Conference Proceedings

High Speed 3D Inspection of Advanced Package Interconnect Uniformity

Authors: Zonghu He Ph.D. and John Schaefer B.E.E.
Company: Rudolph Technologies, Inc.
Date Published: 10/23/2018   Conference: IWLPC (Wafer-Level Packaging)

Abstract: Industry trend toward devices with higher bump densities is driving a need for advances in test equipment for measuring the uniformity of bump height across a device. As bump height decreases, accuracy requirements become tighter. As bump lateral size decreases, resolution required to inspect those bumps increases. Inspecting at higher resolution typically results in decreased throughput so the equipment must be faster.

A new generation laser triangulation (LT) 3D inspection sensor was developed to address these needs. The high resolution is achieved by using a laser line projector positioned 45 degrees from the wafer normal to generate a very narrow line of light on the wafer. The line is viewed with a proprietary, custom-designed, state-of-the-art CMOS camera and high-end microscope optics. Distance to over 1,000 points along the line is measured for each camera frame. Inspection rates three to five times faster than the previous technology can be achieved with improved accuracy and repeatability.

Tests show that a 300mm wafer with 16 million pillar bumps can be inspected in as little as three minutes at resolutions appropriate to achieve 0.15µm 3sigma height repeatability. Bump heights ranging from 2µm to 350µm can be measured in a single pass. This technology enables precise measurement performance and excellent throughput, making it ideal for today's high-volume production environment.

Key Words: 

3D inspection, micro-bump, bump height, bump coplanarity, copper pillar, laser triangulation

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