Confocal Edge Shape Measurement via Rotational Focal Plane Tilt
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Solution Overview
Problem
Existing measurement technologies for semiconductor wafers struggle to accurately and efficiently measure the edge shape, which is crucial for improving chip yield and is affected by crystallization orientation and angle, leading to asymmetric changes in the vertical direction.
Innovation Solution
A measurement apparatus and method using a confocal optical system with an objective lens and detector, where the optical head is moved to change the focal plane inclination relative to the substrate, and the processing unit measures the edge shape based on peak intensity of reflected light, allowing for rotational movement and accurate edge position determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement methods are used to measure edge shape, then measurement can be performed, but measurement accuracy is insufficient due to asymmetric changes in vertical direction caused by crystallization orientation
Solution Approach 1:
The patent introduces a rotational stage to rotate the substrate around its central axis, adding a rotational dimension to the measurement process. This allows the focal plane to intersect different regions of the edge at various rotation angles, enabling accurate measurement of asymmetric edge shapes that vary with crystallization orientation. The rotational movement transforms a single-plane measurement into a multi-angle comprehensive measurement.
2Measurement precision
If the focal plane is fixed relative to the substrate, then the measurement setup is simple, but the edge shape cannot be accurately measured when edge profile changes with orientation
Solution Approach 1:
The patent makes the measurement system dynamic by introducing rotational movement of the substrate. Instead of a fixed focal plane relative to the substrate, the system rotates the substrate to change the relative orientation between the focal plane and different edge regions. This dynamic approach allows the same focal plane to measure different portions of the edge at different rotation angles, capturing the full asymmetric profile.
3Measurement precision
If multiple measurement points around the circumference are measured, then comprehensive edge shape data is obtained, but measurement time increases
Solution Approach 1:
The patent implements continuous rotational measurement where the substrate rotates continuously while the confocal optical system continuously scans the edge. This continuous measurement approach captures data from all circumferential positions in a single rotational cycle, eliminating the need for discrete stopping and repositioning at multiple measurement points. The continuous action maintains measurement quality while significantly reducing total measurement time.
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
Enables speedy and accurate measurement of edge shapes over the entire circumference of semiconductor wafers, improving quality control and chip yield by providing detailed edge profile data and angle-dependent feature value graphs.
Implementation Method 1
an objective lens positioned so that its focal plane cuts across an edge part of a substrate, and configured to concentrate illumination light so that a linear illumination area is formed on the focal plane
Implementation Method 2
a detector including a plurality of pixels arranged along a direction of the linear illumination area, and configured to detect a reflected light from the edge part of the substrate through a confocal optical system
Data Source
AI summary
A measurement apparatus and a measurement method capable of speedily and accurately measuring an edge shape are provided. A measurement apparatus according to an aspect of the present disclosure includes an objective lens positioned so that its focal plane cuts across an edge part of a substrate, a detector including a plurality of pixels and configured to detect a reflected light from the edge part of the substrate through a confocal optical system, an optical head in which the objective lens and the detector are disposed, a moving mechanism configured to change a relative position of the optical head with respect to the substrate so that an inclination of the focal plane with respect to the substrate is changed, and a processing unit configured to measure a shape of the edge part.