Wafer Bow Metrology Using Pinhole Dot Projection
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Solution Overview
Problem
Current wafer bow metrology systems face challenges in efficiently mapping out-of-plane wafer bow across an entire wafer, leading to reduced throughput and increased costs, which is critical for ensuring the quality of hybrid bonding and other semiconductor manufacturing processes.
Innovation Solution
A metrology system that includes a wafer support, a light source with a pinhole mask, and cameras to capture images of dots projected onto the wafer, allowing for rapid measurement of wafer bow by comparing target and reference dot images, and optionally flipping the wafer to correct for gravity effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of measurement points per wafer is increased to improve measurement precision, then measurement precision is improved, but throughput decreases
Solution Approach 1:
The patent divides the wafer surface into multiple discrete measurement zones, each with its own set of measurement points. The wafer is segmented into regions (e.g., center, intermediate, edge zones) that are measured independently and simultaneously using multiple cameras, allowing comprehensive coverage without sequential scanning that would reduce throughput.
Solution Approach 2:
The patent transitions from traditional single-point or line-based measurement to a two-dimensional array of measurement points across the entire wafer surface. Multiple cameras capture dot patterns projected onto the wafer from different angles, creating a spatial dimensionality that enables simultaneous measurement of numerous points across the full wafer area, achieving both high precision and throughput.
2Measurement precision
If traditional optical interferometers are used to achieve accurate wafer bow measurement, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex optical interferometric systems with a simpler projection-based measurement system. Instead of using interferometers that require precise mechanical alignment and complex optical paths, the system projects dot patterns using straightforward optics and captures them with standard cameras, significantly reducing system complexity while maintaining measurement capability.
Solution Approach 2:
The patent creates a simplified optical copy of the wafer surface topography by projecting dot patterns that map the physical surface onto a 2D image plane. The dot positions in the captured images serve as copies of the actual measurement points, allowing reconstruction of the wafer bow map without requiring complex direct measurement optics.
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 system achieves high throughput by mapping wafer bow in under 30 seconds, compares favorably with standard optical interferometric systems, and offers a lower cost solution while maintaining accuracy, thereby enhancing semiconductor manufacturing efficiency.
Implementation Method 1
a first pinhole mask disposed between the first light source and the wafer support. The first pinhole mask can include a plurality of first pinholes that are arranged to pass first light from the first light source and project onto the first side of the wafer a plurality of first dots that correspond to the first pinholes in the first pinhole mask
Implementation Method 2
a first camera arranged to capture an image of the first dots from the first side of the wafer during the wafer bow measurement
Data Source
AI summary
Aspects of the present disclosure provide a metrology system for measuring wafer bow of a wafer. For example, the metrology system can include a wafer support configured to position a wafer for wafer bow measurement, a first light source configured to illuminate a first side of the wafer during the wafer bow measurement, and a first pinhole mask disposed between the first light source and the wafer support. The first pinhole mask can include a plurality of first pinholes that are arranged to pass first light from the first light source and project onto the first side of the wafer a plurality of first dots that correspond to the first pinholes in the first pinhole mask. The metrology system can also include a first camera arranged to capture an image of the first dots from the first side of the wafer during the wafer bow measurement.