Wafer Chip Thickness Measurement Excluding Dicing Groove Zones
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Solution Overview
Problem
Existing methods for measuring chip thickness from wafers inaccurately incorporate thickness data from outer peripheral portions, leading to discrepancies in calculated chip thickness due to variations along projected dicing lines.
Innovation Solution
A measuring method and apparatus that holds chips on a holding surface with a protective member, measures thickness at multiple points, captures images of the reverse side to identify central lines of dicing grooves, and sets a thickness data unreferencing zone around these lines, excluding data from this zone in calculations to minimize the impact of outer peripheral thickness variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thickness data from all measurement points including those near projected dicing lines is used to calculate chip thickness, then the measurement process is simple and comprehensive, but the calculated chip thickness becomes inaccurate due to thickness variations along the dicing lines
Solution Approach 1:
The patent divides the measurement data into two segments: measurement points within a predetermined distance from projected dicing lines (excluded zone) and measurement points outside this distance (included zone). By segmenting the data based on spatial location relative to dicing lines, the patent excludes inaccurate thickness data from the calculation while maintaining a systematic approach to data processing.
Solution Approach 2:
The patent applies different quality standards to different regions of the wafer. Measurement points near projected dicing lines are treated differently (excluded) from those farther away (included). This local quality approach recognizes that thickness measurements near dicing lines have different reliability characteristics and handles them accordingly to improve overall measurement accuracy.
2Measurement precision
If thickness measurements are taken at all points on the wafer including outer peripheral portions, then the data coverage is complete, but the outer peripheral thickness variations negatively affect the accuracy of chip thickness calculations
Solution Approach 1:
The patent extracts and removes measurement data points that fall within the excluded zone (predetermined distance from projected dicing lines) from the dataset used for chip thickness calculation. This extraction process eliminates the harmful influence of outer peripheral thickness variations while retaining the beneficial data from the central regions of the wafer.
Solution Approach 2:
Instead of using all available measurement data points, the patent deliberately uses only a partial subset of the data - specifically, those points outside the excluded zone. This partial action approach sacrifices some data quantity (points within the excluded zone) to achieve higher measurement precision, recognizing that not all collected data is equally useful.
Data Source
AI summary
A measuring method includes storing thickness data of each of chips held on a holding surface of a holding table, the thickness data being obtained by measurement of thicknesses of portions of the chip at a plurality of measurement points and representing the thicknesses measured at the measurement points in association with positions of the measurement points in a predetermined plane corresponding to a reverse side of the wafer, storing positions of central lines of dividing grooves in the predetermined plane in captured images of reverse sides of the chips, setting, in a periphery of each of the chips, a thickness data unreferencing zone including measurement points where the thickness data will not be referenced in calculating the thickness of the chip, and calculating, for each of the chips, an average value of thicknesses at the measurement points except for the measurement points included in the thickness data unreferencing zone.