Wafer Retesting Using Smart Sifting and Multiple Probe Sets
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Solution Overview
Problem
Current wafer testing methods often misclassify usable dice as unqualified, leading to waste and reduced production capacity, as the test conditions remain the same for both initial and retesting, resulting in inefficient use of resources.
Innovation Solution
A method for retesting wafers involves using multiple probe sets to classify dice based on thresholds, employing a smart sifting operation to identify optimal probes or standard probe sets that maximize qualified product identification, thereby dividing the wafer into blocks for targeted retesting, which increases the yield of qualified products and reduces waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the same test conditions are used for both initial and retesting, then the testing process is simple and consistent, but many usable dice are mistakenly classified as unqualified, leading to waste of cost and reduced production capacity
Solution Approach 1:
The patent applies parameter changes by modifying test conditions for retesting compared to initial testing. Specifically, it uses different probe sets, adjusts testing parameters, and changes test paths between initial and retesting phases. This allows the system to reclassify dice that were initially misclassified, thereby improving the accuracy of qualified product identification without requiring completely new testing equipment.
Solution Approach 2:
The patent segments the testing process into distinct phases: initial testing with first probe sets, classification into first dice and retesting dice, and retesting with second probe sets. It also segments the wafer into different regions and uses different test paths for initial and retesting. This segmentation allows targeted retesting of only those dice that need reevaluation, improving accuracy while controlling process complexity.
2Productivity
If multiple probe sets and smart sifting operations are used to improve classification accuracy, then more usable dice can be identified, but the testing process becomes more complex and time-consuming
Solution Approach 1:
The patent applies partial action by performing smart sifting operations only on dice classified as retesting dice, rather than retesting all dice. It uses multiple probe sets but applies them selectively to specific dice groups. This approach identifies more usable dice through targeted retesting while avoiding the time penalty of comprehensive retesting of the entire wafer.
Solution Approach 2:
The patent performs preliminary classification after initial testing to identify which dice require retesting. By pre-sorting dice into first dice (pass) and retesting dice (fail) categories, and then further classifying retesting dice into second dice and third dice groups, the system prepares the testing sequence in advance. This preliminary action reduces overall testing time by avoiding unnecessary retesting of clearly qualified dice.
3Productivity
If the industry increases production area to elevate production capacity, then more wafers can be processed, but the cost of manufacturing increases significantly
Solution Approach 1:
The patent changes testing parameters and conditions between initial and retesting phases, using different probe sets, test paths, and classification thresholds. This allows the same production area to effectively process more wafers by improving the yield through better classification accuracy, thereby increasing production capacity without requiring additional manufacturing area or proportional cost increases.
Data Source
AI summary
A method for retesting a wafer is provided, including following steps of: providing a wafer having dice; providing a plurality of probe sets each including probes used to test the dice; on the basis of a first threshold, the probe sets respectively test the dice so as to classify the dice into first dice and retesting dice, each value obtained from testing each of the first dice being higher than the first threshold, each value obtained from testing each of the retesting dice being lower than the first threshold; conducting a smart sifting operation to classify the retesting dice of the wafer into second dice and third dice, wherein value obtained from testing each of the second dice is higher than a second threshold, and value obtained from testing each of the third dice is lower than the second threshold.