Air-Supported Linear Gauge for Contactless Wafer Height Measurement
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Solution Overview
Problem
Existing linear gauges for measuring wafer surfaces face issues with wear at the contact member's lower tip, leading to inaccurate height measurements.
Innovation Solution
A linear gauge design featuring a contact member supported by an air slider with a cylinder and communication channel, allowing air to create a clearance between the contact member and the workpiece for contactless measurement, preventing wear and enabling adjustable distance control through air flow rate adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the contact member is brought into contact with the wafer for measurement, then the height of the upper surface can be measured, but the lower tip of the contact member is worn and measurement accuracy deteriorates
Solution Approach 1:
The patent introduces an air bearing mechanism where air is supplied through communication channels in the contact member to form an air film between the lower tip and the wafer surface. This pneumatic cushion prevents direct contact, eliminating wear while maintaining measurement capability through the scale that detects contact member position.
Solution Approach 2:
The patent uses air as an intermediary substance between the contact member and the wafer surface. The air film acts as a mediator that transmits measurement information without causing direct mechanical contact, thereby preventing wear of the contact member's lower tip while enabling continuous height measurement.
2Reliability
If air is ejected from the inner supporting wall to support the contact member, then wearing is avoided, but the structure becomes more complex with additional components
Solution Approach 1:
The patent combines the air bearing support function with the contact member structure itself. The communication channels are integrated into the contact member, and the air slider mechanism is merged with the existing measurement components, reducing overall system complexity while maintaining the wear-prevention benefit.
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, contactless measurement of surface displacements without wear on the contact member, allowing for precise measurement of wafer surfaces while maintaining a consistent clearance for reliable data collection.
Implementation Method 1
an air slider including a cylinder having an inner supporting wall that surrounds an outer side wall of the contact member with a clearance left between the inner supporting wall and the outer side wall, and configured to eject air from the inner supporting wall such that the contact member is supported movably in a vertical direction
Implementation Method 2
a communication channel communicating an inlet formed in an upper portion of the contact member and an outlet formed in the lower tip of the contact member with each other inside the contact member. The air evacuated from the evacuation portion into the casing is introduced from the inlet into the communication channel and is allowed to blow out from the outlet to provide a clearance between the lower tip of the contact member and the surface of the workpiece
Data Source
AI summary
A linear gauge includes a contact member having a lower tip to be positioned facing a workpiece; an air slider including a cylinder surrounding the contact member with a clearance left between them, and configured to eject air such that the contact member is supported movably in a vertical direction; a scale that detects a height position of the contact member; a casing accommodating therein the contact member, the air slider, and the scale; an evacuation portion formed in an upper portion of the cylinder such that the ejected air is evacuated into the casing; and a communication channel communicating an inlet, which is formed in an upper portion of the contact member, and an outlet, which is formed in the lower tip of the contact member, with each other inside the contact member.