Electrostatic Chuck Step-Down Dechucking Method
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Solution Overview
Problem
Existing dechucking methods for electrostatic chucks are inefficient in releasing wafers quickly, leading to increased throughput limitations and potential damage due to uncontrolled gas release, which requires costly modifications to the chuck structure and electronic connections.
Innovation Solution
A method involving a multi-stage process where the electrostatic chucking voltage is gradually reduced and then increased to control the escape of gas, ensuring the repulsive force from residual gas is less than the attractive force, allowing for controlled wafer release without damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the chucking voltage is reduced quickly to increase dechucking velocity, then throughput is improved, but uncontrolled gas release may push the wafer away causing damage or loss of robotic control
Solution Approach 1:
The dechucking process is divided into multiple sequential stages: first reducing voltage to allow controlled gas escape, then increasing voltage to re-establish attraction, and finally removing the wafer. This segmentation prevents uncontrolled gas release while maintaining fast throughput by systematically managing the gas pressure buildup that would otherwise push the wafer away.
Solution Approach 2:
The voltage is applied periodically in cycles of reduction and increase during the dechucking process. This periodic action allows the system to repeatedly create controlled conditions for gas escape followed by re-establishment of wafer holding force, ensuring safety while maintaining speed.
2Reliability
If sophisticated measurements and complicated mechanisms are used to control dechucking, then wafer safety is improved, but device complexity and cost increase
Solution Approach 1:
The electrostatic chuck uses its own voltage control capability to manage the dechucking process without requiring external measurement devices or additional control mechanisms. By simply modulating the chucking voltage in a controlled sequence, the system achieves safe dechucking using its inherent functionality, avoiding added complexity.
Solution Approach 2:
The method controls dechucking by changing the voltage parameter in a specific sequence - first reducing it to allow gas escape, then increasing it to re-establish attraction. This parameter-based control achieves reliable wafer release without requiring sophisticated measurement or control hardware.
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 enables faster and more controlled gas release, increasing dechucking velocity while minimizing the risk of wafer damage and maintaining robotic control, all without requiring structural modifications to the electrostatic chuck.
Implementation Method 1
The principle used for an electrostatic chuck is to apply a voltage to one or more electrodes in the chuck so as to induce opposite polarity charges in the workpiece and electrode(s). The electrostatic attractive force between the opposite charges attracts the workpiece against the chuck
Implementation Method 2
The electrostatic attractive force between the opposite charges attracts the workpiece against the chuck, thereby holding the workpiece
Implementation Method 3
a gas may be applied to the back surface of the wafer 13 via conduits 16 for controlling the wafer temperature (or for removing heat from the wafer)
Data Source
AI summary
A method and an apparatus for dechucking an electrostatic chuck are disclosed. The gas escapes through an opening between a wafer and a chuck in each stage of a multi-stages process. In each stage, during at least a portion of the stage, the chucking voltage is reduced to a value less than the least threshold voltage needed for holding the wafer, so that the wafer is pushed away from the chuck by the gas. Hence, the gas can escape from an opening between the wafer and the chuck, thereby increasing the dechucking rate. By controlling the decrement and/or the duration of the reduced voltage, any potential damages due to the pushed-away wafer can be minimized.