Wafer-level Test and Burn-in (WLB) - Page 3 of 3

Challenges in Wafer Level Test and Burn-in

Aside from the high up-front costs of developing and setting up the equipment, especially if full-wafer contact technology is involved, another serious challenge posed by WLTBI is the achievement of highly reliable and excellent electrical contact between each of the probes and its corresponding bond or test pad (or bump) on the die. 

Poor contact or loss of contact in the middle of test or burn-in may result in a multitude of problems: over-rejection, insufficient burn-in, and even electrical overstress (EOS). Contact failure involving even just a single pad or bump of the device will cause the test or burn-in to fail.  A wafer probing system with excellent and reliable contact capability will eliminate yield losses due to contact failures - a necessity in the ever-competitive semiconductor industry. 

Ensuring high contact integrity and reliability for a large number of probe tips is not easy though. At the very least, it entails a sound maintenance routine that consists of monitoring probe tip life, replacing worn-out tips, and continuous tip-to-pad alignment checks and realignment. 

Achieving the bandwidth required by electrical testing and burn-in of high-speed devices is also another consideration that needs to be addressed by an engineer setting up WLTBI capability. Excellent engineering design and material selection for the probe needles to be used are a 'must' if high bandwidth test and burn-in capability is desired. 

The initial steps toward viable wafer-level test and burn-in systems have already been taken. Still, the journey toward industry-standard WLTBI methods and equipment will be long and arduous. Obstacles in the way of standardized WLTBI processes include the large diversity of wafer-level packaging solutions; the continuous reduction in wafer size and die interconnection pitches; and the wide availability of conventional test and burn-in solutions for applications that are not yet ready for WLTBI. 

Just the same, many companies will try to be at the forefront of WLTBI technology because, to most of them, an integrated wafer-level manufacturing approach would make the best sense for the future of semiconductor manufacturing.

Figure 1. Example of a Handler for

Wafer-Level Burn-in

<Back to Page 1 - Intro to Wafer Level Test and Burn-in>

<Back to Page 2 - Achieving Full Wafer Contact>

See Also:  Electrical Testing;  Burn-in;  Probe/Trim; 

Wafer-Level Packaging;  IC Manufacturing

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