Electrostatic Clamp Voltage Frequency Control
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Solution Overview
Problem
Electrostatic clamps in the semiconductor industry often experience 'sticking' issues due to residual electrostatic charges, leading to reduced workpiece throughput and potential breakage, as the nature and distribution of these charges are uncontrolled and unpredictable.
Innovation Solution
A method and system that adjust the clamping voltage and frequency settings on electrostatic clamps from a high voltage/low frequency 'Hi V/low F' condition to a low voltage/high frequency 'Low V/Hi F' condition to facilitate controlled de-clamping, allowing for efficient removal of workpieces regardless of residual charges, while maintaining high throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If high voltage/low frequency clamping is used, then strong clamping force is achieved, but uncontrolled sticking behavior occurs due to residual charges
Solution Approach 1:
The system dynamically adjusts clamping parameters by switching between two distinct operational modes: Hi V/low F mode for strong clamping during processing, and Low V/Hi F mode for controlled de-clamping. This dynamic parameter adjustment allows the system to adapt to different operational requirements and eliminate sticking issues.
Solution Approach 2:
The control system periodically switches between clamping modes based on process requirements. During semiconductor processing, Hi V/low F clamping is applied; when de-clamping is needed, the system transitions to Low V/Hi F mode. This periodic action ensures reliable workpiece holding during processing while enabling controlled release afterward.
2Reliability
If residual electrostatic charges are present, then workpiece sticking occurs, but workpiece throughput is reduced
Solution Approach 1:
The system converts the harmful effect of residual electrostatic charges into a beneficial outcome by using Low V/Hi F clamping parameters. This mode allows residual charges to dissipate while maintaining sufficient clamping force for stable holding, thereby preventing sticking and enabling rapid de-clamping that improves throughput.
Solution Approach 2:
The system changes the electrical parameters of the clamping field by switching from high voltage/low frequency to low voltage/high frequency settings. This parameter change allows the system to maintain clamping stability while facilitating rapid charge dissipation and improving workpiece release speed.
3Productivity
If rapid de-clamping is achieved, then workpiece throughput is improved, but workpiece breakage risk increases
Solution Approach 1:
The system applies Low V/Hi F clamping parameters before the actual de-clamping action occurs. This preparatory step gradually reduces the clamping force and allows residual charges to dissipate in a controlled manner, cushioning the workpiece against sudden force changes that could cause breakage.
Solution Approach 2:
The control system performs a preliminary transition to Low V/Hi F mode before complete de-clamping. This preliminary action prepares the workpiece for release by reducing electrostatic forces while maintaining mechanical support, thereby preventing breakage during the de-clamping 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
This approach effectively minimizes uncontrolled sticking behavior, ensuring reproducible de-clamping and reducing the risk of workpiece breakage by creating a controlled low-clamping force state, thereby improving processing efficiency and throughput.
Implementation Method 1
a clamping voltage is typically applied between the wafer and the electrode, wherein the wafer is clamped against the surface of the ESC by electrostatic forces
Implementation Method 2
sticking of a workpiece to the surface of an ESC is generally attributed to residual electrostatic charges at the interface between the ESC and workpiece not finding a rapid path to electrical ground after removal of power to the electrodes of the ESC
Data Source
AI summary
A system and method for clamping a workpiece to an electrostatic clamp (ESC) comprises placing a first workpiece on a surface of the ESC and applying a first set of clamping parameters to the ESC, therein clamping the first workpiece to the surface of the ESC with a first clamping force. A degree of clamping of the workpiece to the ESC is determined and the application of the first set of clamping parameters to the ESC is halted based on a process recipe. A second set of clamping parameters is applied to the ESC after halting the application of the first set of clamping parameters to the ESC, and the workpiece is removed from the surface of the ESC concurrent with the application of the second set of clamping parameters to the ESC when the degree of clamping of the workpiece to the ESC is less than or approximately equal to a threshold clamping value. The second set of clamping parameters to the ESC is further halted after removing the workpiece from the surface of the ESC.