Original Date: 01/24/1994
Revision Date: 01/18/2007
Best Practice : Storage Life Reliability Test Vehicle
The Harris reliability group has innovatively addressed difficulties associated with conducting unbiased storage life tests. Unbiased storage life tests are performed during process evaluations, qualifications, or process changes and evaluate the susceptibility of the product for stress induced voids in the product’s metallization lines. Typically the storage life test involves the storage of product for 3000 hours at 180 degrees C. Its inherent time consuming nature has a negative impact on product to market and cycle times. Harris has developed a test vehicle with a six-meter long meandering line with provisions for several widths (1.0, 1.4, and 1.8 microns). The structure is designed with several bond pads to evaluate different lengths of the long meandering metal lines. This new approach allows reliability evaluation in substantially shorter time.
A test was recently conducted to evaluate a technology with a 2.0micron line width. At the 672 hour test point, more than 50% of the 1.0 micron line had voids, and 6% of the 1.4 micron line had voids while the 1.8 micron line had no voids. These results in effect validated the process in 22% of the typical test time.
This test vehicle now permits the stress induced void evaluation to be completed in 672 hours as opposed to the traditional 3000 hour storage life test. Savings in time and money are key elements of this process, allowing Harris to further improve its IC processes.
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