Electrostatic Clamp Table Unloading With Controlled Charge Dissipation
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Solution Overview
Problem
The use of electrostatic clamps in inspection apparatuses for semiconductor substrates leads to charge buildup on the clamp surface, causing objects to stick and increasing the risk of sparking or discharging during the unloading process, which can damage the object, clamp, or surrounding components, especially in vacuum environments.
Innovation Solution
An object table with a clamping mechanism that includes an electrical conductor to connect the object to a voltage source during unloading, forming a low mechanical stiffness connection to mitigate charge-induced sparking and vibration transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an electrostatic clamp is used to hold the object, then the object can be securely clamped during inspection, but charge builds up on the clamp surface causing the object to stick and increasing the risk of sparking during unloading
Solution Approach 1:
The patent extracts the electrical conductor from the clamp structure, allowing it to be selectively connected only during unloading operations. This separates the clamping function (electrostatic) from the discharge function (electrical conductor), enabling the clamp to hold objects securely during inspection while providing a controlled path for charge dissipation during unloading, thereby reducing sparking risk
Solution Approach 2:
The patent applies preliminary action by connecting the electrical conductor to the clamp surface before the unloading process begins. This pre-connection ensures that the charge buildup is already present on the clamp surface when the conductor is activated, allowing for controlled discharge through the conductor before any sparking can occur to surrounding components
2Object-affected harmful factors
If a rigid electrical connection is used to discharge the clamp, then charge can be effectively removed, but mechanical vibrations and disturbances are transmitted to the object table
Solution Approach 1:
The patent employs a flexible electrical conductor instead of a rigid connection. The flexibility of the conductor allows it to conform to the clamp surface while providing electrical connectivity for charge discharge. This flexible connection mechanically isolates the object table from vibrations and disturbances, as the flexible conductor does not transmit mechanical stresses effectively while maintaining electrical conductivity for charge removal
3Ease of operation
If the clamp is designed for easy unloading, then objects can be quickly removed, but the clamping force may be insufficient to hold the object securely during inspection
Solution Approach 1:
The patent implements a dynamic system where the electrical conductor's connectivity state changes based on operational phase. During inspection, the conductor is disconnected to maintain strong electrostatic clamping. During unloading, the conductor is connected to facilitate easy object removal by providing a charge dissipation path. This dynamic switching allows the system to optimize for either clamping reliability or unloading ease depending on the operational requirement
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
Reduces the risk of sparking and mechanical disturbances during unloading, ensuring safe and efficient removal of objects from the clamp while maintaining accurate positioning.
Implementation Method 1
an electrostatic clamp arranged to clamp the object on the object table
Implementation Method 2
an electrical conductor configured to electrically connect the object to a voltage source or an electrical ground to apply a predetermined voltage to the object during at least part of an unloading sequence
Data Source
AI summary
Disclosed is an object table for holding an object, comprising: an electrostatic clamp arranged to clamp the object on the object table; a neutralizer arranged to neutralize a residual charge of the electrostatic clamp; a control unit arranged to control the neutralizer, wherein the residual charge is an electrostatic charge present on the electrostatic clamp when no voltage is applied to the electrostatic clamp.