Electrostatic Chuck Discharging Element for Wafer Protection
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Solution Overview
Problem
Conventional electrostatic chucks face issues with charge accumulation in the isolating substrate, which can damage the wafer during unloading due to residual charge, causing attraction to the chuck and potential breakage.
Innovation Solution
Incorporating a discharging element between the electrodes and the wafer-contacting protrusions, connected to a discharging circuit that operates in a floating potential during chucking mode and grounds during discharge mode to manage charge accumulation and prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an isolating substrate is used to surround the electrodes, then electrical insulation is improved, but charge accumulation occurs in the isolating substrate which can damage the wafer
Solution Approach 1:
A discharging element is introduced as an intermediary component between the isolating substrate and the wafer. This discharging element selectively discharges accumulated charge in the isolating substrate while maintaining electrical insulation during normal operation, thereby preventing charge-related wafer damage without compromising the insulating function.
Solution Approach 2:
The electrical properties of the discharging element are specifically designed to change based on charge accumulation conditions. The element has a threshold behavior where it transitions from an insulating state during normal operation to a conductive state when charge exceeds a certain level, enabling dynamic parameter adjustment to prevent damage while maintaining insulation.
2Force
If the isolating substrate accumulates charge, then the wafer is attracted to the chuck, but the wafer cannot be easily detached during unloading
Solution Approach 1:
The discharging element acts as a mediator that controls the interaction between the charged isolating substrate and the wafer. During normal operation, it maintains the attractive force by allowing charge accumulation. During unloading, it discharges the substrate to eliminate residual attraction, enabling easy wafer detachment without mechanical force.
Solution Approach 2:
The discharging element operates periodically - accumulating charge during the chucking phase to maintain attraction, then discharging during the unloading phase to facilitate detachment. This periodic charge accumulation and discharge cycle enables both strong holding force and easy release.
3Force
If residual charge is present in the isolating substrate, then wafer holding is maintained, but wafer breakage can occur during unloading
Solution Approach 1:
The discharging element serves as a protective intermediary that monitors and controls charge levels in the isolating substrate. It prevents charge accumulation from reaching levels that would cause wafer breakage during unloading, while maintaining sufficient charge for proper wafer holding during operation.
Solution Approach 2:
The discharging element provides beforehand cushioning by preemptively discharging excessive charge before it can cause wafer damage. It acts as a protective mechanism that prevents harmful charge levels from developing, cushioning the wafer against potential electrostatic damage during the unloading process.
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
Effectively discharges accumulated charge, preventing wafer damage and facilitating easy unloading by controlling electrical discharges between the wafer and the chuck, thereby enhancing the operational reliability of the electrostatic chuck.
Implementation Method 1
The conductivity of the discharging element may be selected to limit electrical discharges between the wafer and the electrostatic chuck
Implementation Method 2
The voltage differences between the wafer 10 and each of the electrodes 31 and 32 attract the wafer 10 towards the chuck 60
Data Source
AI summary
An electrostatic chuck includes an isolating substrate that surrounds at least one electrode; multiple protrusions having upper portions arranged to contact a wafer; and at least one discharging element positioned between the at least one electrode and the upper portions of the multiple protrusions; which discharging element, once coupled to a discharging circuit, is arranged to discharge charge accumulated in the isolating substrate.