Wafer Surface Measuring Apparatus Non-Contact Handling
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Solution Overview
Problem
Existing wafer surface measuring apparatuses face challenges in supporting large-diameter or thin-thickness wafers without contact between the rear surface and the measuring stage, leading to potential contamination and measurement inaccuracies due to bending and gas turbulence.
Innovation Solution
A wafer surface measuring apparatus that uses a Bernoulli chuck to bend the wafer in an upwardly convex shape, maintaining a non-contact state between the wafer and the stage, and employs a gas ejection system to control the wafer's position and prevent contact during measurement, while also incorporating a rotational position adjusting mechanism and cleanliness features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gas is ejected from the center portion of the stage to correct wafer bending, then the non-contact state between wafer and stage is maintained, but turbulent flow is produced causing wafer vibration and particle generation
Solution Approach 1:
The patent employs a gas ejection system with nozzles positioned at the center portion of the measuring stage to supply gas to the rear surface of the wafer. This pneumatic approach creates a pressure differential that countersacts the downward bending of the wafer center caused by gravity, maintaining the wafer in a non-contact state above the stage surface without requiring mechanical support.
Solution Approach 2:
The patent controls the gas ejection parameters (flow rate, pressure) to optimize the balance between maintaining the non-contact state and avoiding turbulent flow. By adjusting these parameters, the system achieves laminar flow conditions that prevent wafer vibration and particle generation while still providing sufficient upward pressure to counteract gravitational bending.
2Reliability
If the space between wafer rear surface and stage surface is increased to prevent contact, then contact is avoided, but turbulent flow is produced when gas passes through the gap
Solution Approach 1:
The patent introduces gas as an intermediary medium between the wafer rear surface and the stage surface. This gas layer acts as a cushion that prevents direct contact while allowing precise control of the wafer position. The gas flow serves as a mediator that transmits force from the stage to the wafer without requiring mechanical contact.
Solution Approach 2:
The system uses pneumatic principles to control the gas flow through the gap between the wafer and stage. By regulating the gas pressure and flow rate, the system maintains a stable, controlled distance without direct contact, avoiding both turbulence-induced vibration and insufficient support.
3Ease of operation
If manual carrying of wafer to measuring stage is performed, then flexibility is maintained, but working efficiency is low and contamination risk is high
Solution Approach 1:
The patent implements an automated wafer carrying system that transfers wafers from the cassette to the measuring stage without manual intervention. The system uses a robotic arm or automated transfer mechanism that picks up wafers and places them on the measuring stage, allowing the system to serve itself and eliminating the need for operator involvement in the transfer process.
Solution Approach 2:
The patent replaces manual mechanical carrying with an automated mechanical system. The automated transfer mechanism uses controlled motion and positioning systems to move wafers, substituting human operators with machine-based automation that provides consistent, contamination-free handling while significantly improving throughput 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
Enables accurate and contamination-free measurement of large-diameter or thin-thickness wafers by maintaining a non-contact state between the wafer and the stage, preventing contact and vibration, and ensuring high cleanliness and efficiency in wafer handling and measurement.
Implementation Method 1
a chuck that sucks and holds the surface of the wafer in a non-contact manner and bends the wafer in an upwardly convex shape
Implementation Method 2
an ejection hole formed at a center portion of the stage surface to supply gas to a rear surface of the wafer which is loaded on the measuring stage
Implementation Method 3
detecting foreign substances, such as particles or the like, or fine defects existing on the surface of a semiconductor wafer by using light scattering
Data Source
AI summary
A wafer surface measuring apparatus which measures a surface of the wafer by irradiating a laser beam on a wafer comprising a measuring stage that supports the outer edge of the wafer and loads the wafer in a manner not contacting the rear surface of the wafer and the stage surface, a wafer carrying means that moves the wafer over the measuring stage and loads the wafer on the measuring stage from an upward side, a rotary drive unit which rotates the measuring stage, and an ejection hole formed at a center portion of the stage surface to supply gas to a rear surface of the wafer loaded on the measuring stage. The wafer carrying means includes a chuck which sucks and holds the surface of the wafer in a non-contact manner and bends the wafer in an upwardly convex shape.