Substrate Holding Device Flatness Control
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Solution Overview
Problem
Conventional substrate mounting apparatuses cause contamination and sagging of semiconductor wafers due to contact with the rear surface, leading to impaired flatness, which obstructs processing and inspection.
Innovation Solution
A substrate holding device that maintains the flatness of semiconductor wafers by controlling pressure on the rear surface using concavity-convex structures, gas supply, and temperature control, with piezo elements to adjust the convexity and concavity, ensuring non-contact handling and precise flatness measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rear surface of the substrate is supported by a projecting pin or rim, then the substrate can be held during rotation, but the rear surface becomes contaminated and the front surface flatness is impaired
Solution Approach 1:
A liquid medium (gas or liquid) is introduced as an intermediary between the substrate rear surface and the support structure. This medium transmits the supporting force while preventing direct contact, thereby eliminating contamination and flatness impairment while maintaining holding stability
Solution Approach 2:
The patent applies pneumatic or hydraulic pressure through a liquid medium to support the substrate from the rear surface. By controlling the pressure of this medium, the substrate is held stably during rotation without direct mechanical contact, solving both the holding stability and contamination problems
2Object-affected harmful factors
If the side surface of the wafer substrate is supported to prevent contact with projecting pins, then contamination is avoided, but the wafer substrate sags due to its own weight and flatness is impaired
Solution Approach 1:
The liquid medium serves as a mediator that distributes the supporting force uniformly across the substrate rear surface, preventing both direct contact contamination and localized sagging that would compromise front surface flatness
Solution Approach 2:
By adjusting the pressure parameters of the liquid medium, the system optimizes the balance between preventing contamination and maintaining substrate flatness, allowing the substrate to be held without sagging while avoiding contact contamination
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 solution ensures the flatness of the substrate's front surface without contaminating the rear surface, enabling stable inspection and processing by maintaining the substrate's flatness through controlled pressure and convexity adjustments.
Implementation Method 1
a piezo element 14 that changes its shape according to the applied voltage
Implementation Method 2
controlling pressure on the rear surface using concavity-convex structures
Data Source
AI summary
Non-contact type displacement sensors which measure the height of a substrate surface are installed above the substrate in order to hold the upper surface of the substrate at a desired height or to maintain the flatness of the substrate. A substrate mounting device is such that a plurality of grooves and of barriers are provided on the upper surface of a table and air is supplied between the substrate and the table to enable the pressure of air to displace the substrate. In addition, the substrate mounting device has such a structure as to make it possible to deform the substrate into an arbitrary convex-concave shape or to make the substrate flat by feeding back the output of the displacement sensor.