Electrode Pad Inspection With 2D Screening and 3D Verification
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Solution Overview
Problem
Existing semiconductor inspection methods face challenges in accurately and efficiently determining the quality of electrode pads due to difficulties in distinguishing between brightness/darkness caused by wafer surface shape and material differences, leading to potential misclassification of defects, and time-consuming three-dimensional shape measurements that are prone to accuracy issues from air disturbances.
Innovation Solution
A combined inspection device and method using a 2D camera for tentative quality determination followed by a 3D shape measuring machine for formal determination, with alignment and measurement field of view optimization to enhance accuracy and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a 2D camera is used for visual inspection of the wafer, then the inspection speed is improved, but the measurement precision deteriorates due to inability to distinguish brightness/darkness caused by surface shape from material differences
Solution Approach 1:
The patent transitions from 2D image-based inspection to 3D shape measurement by introducing a focus variation method that captures images at multiple focal depths. This dimensional change enables differentiation between surface shape variations (which cause focus changes) and actual defects (which maintain consistent focus), thereby resolving the ambiguity in 2D brightness/darkness interpretation while maintaining inspection efficiency
Solution Approach 2:
The patent performs preliminary 2D image capture and analysis to identify regions of interest before conducting detailed 3D shape measurement. This preliminary action filters out obvious defects and prepares the measurement data in advance, allowing the focus variation method to concentrate computational resources on ambiguous cases, thus improving overall inspection speed while maintaining precision
2Measurement precision
If a three-dimensional shape measuring machine is used for formal determination, then the measurement precision is improved, but the inspection time increases and accuracy is reduced due to air disturbances
Solution Approach 1:
The patent performs preliminary 2D image-based screening to identify only those regions requiring formal 3D determination. This preliminary filtering reduces the number of targets subjected to time-consuming 3D measurement, thereby significantly reducing total inspection time while ensuring that all critical defects undergo precise formal determination
Solution Approach 2:
The patent replaces traditional mechanical contact-based 3D measurement systems with a non-contact optical focus variation method. This substitution eliminates mechanical vibrations and air disturbances that affect conventional measuring machines, achieving high measurement precision without the associated time losses and environmental sensitivity
3Productivity
If the measurement field of view is enlarged to inspect multiple electrode pads, then the productivity is improved, but the alignment precision between camera and three-dimensional shape measuring machine becomes more critical and difficult to maintain
Solution Approach 1:
The patent uses 3D shape information obtained through focus variation to establish precise spatial relationships between multiple electrode pads in the measurement field. By utilizing the depth dimension data, the system can accurately register and align measurements across a larger field of view, overcoming the alignment difficulties that would otherwise limit multi-pad inspection efficiency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed method allows for rapid and accurate inspection of needle marks on electrode pads, reducing inspection time and minimizing errors by leveraging both 2D imaging and 3D shape measurement techniques.
Implementation Method 1
an image (two-dimensional image) of the wafer captured by a camera
Implementation Method 2
a three-dimensional shape measuring machine capable of contactless measurement of a three-dimensional shape
Data Source
AI summary
An inspection device includes: a camera configured to capture an image of an inspection object on a wafer; a first determining unit configured to detect the inspection object from the image captured by the camera and make a tentative determination of quality of the inspection object; a three-dimensional shape measuring machine configured to measure a three-dimensional shape of the inspection object determined to be abnormal by the tentative determination; and a second determining unit configured to make a formal determination of the quality of the inspection object based on the three-dimensional shape of the inspection object measured by the three-dimensional shape measuring machine and the image captured by the camera or based on the three-dimensional shape of the inspection object measured by the three-dimensional shape measuring machine.