Dual-Sided Moiré Wafer Analysis for Thickness Variation
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Solution Overview
Problem
Existing defect detection technologies for silicon wafers used in integrated circuit manufacturing are inadequate in determining thickness variations and detecting various types of defects, leading to inefficient fabrication of defective chips.
Innovation Solution
A dual-sided Moiré fringe acquisition system that integrates wafer flatness measurement with surface defect detection, using phase shifting reflective Moiré wafer analysis on both sides of the wafer to generate thickness variation maps and detect defects such as adhesion, slip line, and edge defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If prior defect detection technologies are used, then defect detection capability is provided, but thickness variation determination and comprehensive defect detection are inadequate
Solution Approach 1:
The patent combines flatness measurement and surface defect detection into a single dual-sided Moiré fringe acquisition system. The system simultaneously captures Moiré fringes from both front and back sides of the wafer, integrating multiple measurement functions (thickness variation, surface topography, defect detection) into one unified apparatus, thereby resolving the contradiction between measurement precision and reliability.
Solution Approach 2:
The Moiré fringe acquisition system is designed to perform multiple functions: measuring thickness variations, mapping surface topography, detecting adhesion defects, slip line defects, and edge defects. This multi-functional capability allows the system to address comprehensive defect detection while maintaining high measurement precision for thickness variations.
2Area of stationary object
If conventional single-sided measurement systems are used, then simpler system design is achieved, but measurement area coverage and defect detection completeness are limited
Solution Approach 1:
The system transitions from single-sided measurement to dual-sided simultaneous measurement, adding the dimension of wafer thickness by capturing fringes from both front and back surfaces. This enables comprehensive coverage of the entire wafer volume for defect detection while maintaining manageable system complexity through integrated optical design.
Solution Approach 2:
The system divides the measurement task into two simultaneous acquisitions (front side and back side) and processes them together to generate comprehensive thickness variation maps. By segmenting the measurement into manageable components that are then integrated, the system achieves complete area coverage without excessive complexity.
3Reliability
If standard Moiré fringe acquisition is used, then basic flatness measurement is provided, but dynamic range for wafers with large bows is insufficient
Solution Approach 1:
The system employs phase shifting technology that varies the phase of projected fringes to capture multiple interferograms. By changing phase parameters and processing multiple acquisitions, the system extends its dynamic range to accurately measure wafers with large bows while maintaining measurement reliability through computational integration of the phase-shifted data.
4Reliability
If existing defect detection methods are used, then some defect types are detected, but comprehensive defect detection including adhesion, slip line, and edge defects is not achieved
Solution Approach 1:
The system performs comprehensive defect detection on wafers before etching integrated circuits onto them. By identifying adhesion defects, slip line defects, and edge defects in advance using dual-sided Moiré fringe analysis, the system prevents defective chips from being fabricated, thereby improving overall fabrication efficiency and productivity.
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 provides faster throughput, lower cost, reduced sensitivity to vibration and air turbulence, and a larger dynamic range, enabling accurate detection of defects and thickness variations on wafers with large bows and extending measurement area closer to the wafer edge.
Implementation Method 1
A Moiré pattern is projected across a first side of the wafer in multiple fringe acquisition iterations
Implementation Method 2
Multiple slope maps are computed by phase shifting the fringe patterns
Implementation Method 3
phase shifting reflective Moiré wafer analysis
Data Source
AI summary
The invention provides a new dual-sided Moiré wafer analysis system that integrates wafer flatness measurement capability with wafer surface defect detection capability. The invention may be, but is not necessarily, embodied in methods and systems for simultaneously applying phase shifting reflective Moiré wafer analysis to the front and back sides of a silicon wafer and comparing or combining the front and back side height maps. This allows wafer surface height for each side of the wafer, thickness variation map, surface nanotopography, shape, flatness, and edge map to be determined with a dual-sided fringe acquisition process. The invention also improves the dynamic range of wafer analysis to measure wafers with large bows and extends the measurement area closer to the wafer edge.