Electrostatic Chuck De-Chucking Using Swing Voltage Sequence
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Solution Overview
Problem
The existing two-step voltage sequence used for de-chucking wafers from electrostatic chucks is often insufficient, leading to potential wafer breakage due to residual electrostatic charges and varying de-chuck times, especially with complex structures like VNAND memory, which can result in prolonged processing times and chamber faults.
Innovation Solution
A method employing a multi-step pulsing swing voltage sequence with decreasing voltage amplitudes, combined with gentle helium gas pressure applied to the backside of the wafer, to actively control the de-chucking process, monitoring helium leak rates to determine when the wafer is released, and repeating the sequence if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a two-step voltage sequence is used to de-chuck the wafer, then the electrostatic charge is discharged to release the wafer, but residual electrostatic charges remain causing wafer breakage and prolonged processing times
Solution Approach 1:
The voltage sequence is divided into multiple discrete steps (first voltage pulse, second voltage pulse, third voltage pulse) rather than using a simple two-step sequence. Each pulse serves a specific function in progressively reducing the electrostatic charge, ensuring complete discharge without residual charges that could cause wafer breakage.
Solution Approach 2:
The de-chucking process uses periodic voltage pulses applied in sequence to progressively discharge the electrostatic charge. The multi-step pulsing approach with helium gas pressure applied during specific pulses creates a periodic action that efficiently removes charges while monitoring helium leak rates to determine when release is complete.
2Reliability
If a multi-step pulsing swing voltage sequence is applied, then residual electrostatic charges are eliminated, but the process complexity increases
Solution Approach 1:
The system monitors helium leak rates during the de-chucking process to provide feedback on whether the wafer has been successfully released. This feedback mechanism allows the controller to determine when to stop the voltage pulsing sequence, ensuring reliable release while avoiding unnecessary additional steps that would increase complexity.
Solution Approach 2:
The multi-step voltage sequence automatically adjusts the de-chucking process based on the electrostatic charge conditions. The controller applies voltage pulses and monitors helium leak rates, allowing the system to self-regulate and complete the release process without requiring external intervention or complex manual control.
3Reliability
If voltage pulses are applied to discharge electrostatic charge, then the wafer can be released, but varying de-chuck times occur especially with complex structures like VNAND memory
Solution Approach 1:
The system continuously monitors helium leak rates during the voltage pulsing sequence to determine when the wafer has been successfully released. This feedback approach allows the process to adapt to different wafer structures (including complex VNAND memory structures) and automatically adjust the duration of each voltage pulse, ensuring consistent release times regardless of wafer complexity.
Solution Approach 2:
The voltage pulses are applied with varying parameters (different voltage levels, different durations) depending on the detected electrostatic charge conditions. The controller adjusts the voltage pulse characteristics based on helium leak rate monitoring, allowing the system to handle different wafer types and structures with optimized parameters that reduce de-chuck time variability.
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 approach effectively reduces the risk of wafer breakage and variability in de-chuck times, ensuring reliable and efficient release of wafers from the electrostatic chuck, even with complex structures, by actively managing electrostatic forces and mechanical pressure.
Implementation Method 1
The ESC uses an electrostatic force to grip the wafer during plasma and during other types of processes.
Implementation Method 2
At the end of a process or when the wafer is to be transferred to a different carrier, the electrostatic charge is discharged so that the wafer can be released from the ESC.
Implementation Method 3
The voltage sequence may be combined with a gentle helium gas pressure against the back side of the wafer to push it away from the chuck.
Data Source
AI summary
A method and apparatus for de-chucking a workpiece is described that uses a swing voltage sequence. One example pertains to a method that includes applying a mechanical force from an electrostatic chuck against the back side of a workpiece that is electrostatically clamped to the chuck, applying a sequence of voltage pulses with a same polarity to the electrodes, each pulse of the sequence having a lower voltage than the preceding pulse, each pulse of the sequence having a lower voltage than the preceding pulse, and determining whether the workpiece is released from the chuck after the sequence of additional voltage pulses and if the workpiece is not released then repeating applying the sequence of voltage pulses.