Edge Handling Chuck Topography for Wafer Stability
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Solution Overview
Problem
Current edge handling chucks face challenges in maintaining a stable surface for semiconductor wafers at high rotation speeds above 1500 rpm, leading to increased airflow requirements that result in wafer deformation and excessive particle contamination.
Innovation Solution
The design incorporates a cylindrical plate with a varied topography on its surface, reducing the fluid flow rate needed to support the wafer during rotation, which significantly decreases wafer shape distortion and contamination by optimizing airflow dynamics and reducing air gap height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If airflow rate is increased to support wafer at high rotation speeds, then wafer support stability is improved, but particle contamination increases
Solution Approach 1:
The chuck surface is modified with localized features including a depression region and protrusion features that create regions of different air pressure. The depression region generates higher air pressure to support the wafer center, while the protrusion features create lower pressure regions at the edges, optimizing support without requiring high overall airflow that causes contamination.
Solution Approach 2:
The invention changes the pressure distribution parameters across the chuck surface by creating varied topography features. This transforms the uniform pressure field into a non-uniform field with specific high-pressure and low-pressure zones, enabling effective wafer support at reduced airflow rates and thus reducing particle contamination.
2Manufacturing precision
If airflow rate is increased to maintain wafer flatness at high rotation speeds, then wafer flatness control is improved, but wafer deformation increases
Solution Approach 1:
The depression region and protrusion features create localized pressure zones that differentially support various regions of the wafer. The high-pressure region under the depression supports the wafer center to prevent sagging, while the low-pressure regions at the edges allow the wafer to maintain its natural curvature, preventing deformation caused by excessive uniform pressure.
Solution Approach 2:
The depression region in the chuck surface is designed with a curved geometry that matches the natural curvature of the wafer. This curved surface allows the wafer to conform naturally while receiving support, preventing the flatness control methods that use high uniform pressure from causing wafer deformation.
3Productivity
If rotation speed is increased to improve inspection throughput, then productivity is improved, but particle contamination increases
Solution Approach 1:
The invention changes the airflow parameter from high flow rate to optimized low flow rate by utilizing pressure distribution through surface topography features. This allows the system to achieve stable wafer support at high rotation speeds without the high airflow rates that generate particle contamination, thus enabling increased productivity without the harmful side effect.
4Device complexity
If uniform air pressure is applied across the chuck surface, then wafer support is simplified, but wafer flatness control deteriorates
Solution Approach 1:
Instead of uniform pressure, the invention implements localized pressure zones through surface features. The depression region creates a high-pressure zone for central support while protrusion features create low-pressure zones at the edges. This non-uniform pressure distribution, achieved through geometric features rather than complex pressure control systems, actually improves wafer flatness control while maintaining reasonable design simplicity.
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
This solution allows for stable wafer support at rotation speeds up to 3000 rpm or higher with reduced airflow, minimizing particle contamination and enhancing chuck damping capabilities, thus improving the overall performance of wafer inspection systems.
Implementation Method 1
Air flows through a center opening in the cylindrical plate and across a top surface of the plate having a varied topography to a periphery of the plate in a gap space between the top surface and a back surface of the substrate supported by the chuck
Implementation Method 2
The design incorporates a cylindrical plate with a varied topography on its surface, reducing the fluid flow rate needed to support the wafer during rotation, which significantly decreases wafer shape distortion and contamination by optimizing airflow dynamics and reducing air gap height
Data Source
AI summary
An edge-handling chuck, a system for holding and rotating a test substrate at a high speed and a method for chucking a rotating substrate are disclosed. The Chuck includes a plate having a central axis, a fluid opening and a top surface with a varied topography characterized by symmetry about the central axis. The topography is such that a volume flow rate of fluid between the fluid opening and a periphery of the top surface sufficient to counteract substrate sagging is significantly less than a volume flow rate needed for a similar but flat-surfaced chuck to similarly counteract such sagging. The system may further include a spindle motor and a gas system that supplies gas through the fluid opening to a gap between the top surface and a back surface of the substrate. A radial velocity of the fluid through the gap is approximately constant.