Dynamic Clamping Voltage Modulation for Workpiece Backside Protection
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Solution Overview
Problem
The thermal expansion and contraction of workpieces during semiconductor fabrication processes can cause damage to the back surface due to relative movement with the platen, leading to scratches and reduced device yield.
Innovation Solution
A system that modulates clamping voltage and backside gas pressure during thermal transitions to minimize workpiece damage, using a controller to adjust the clamping force and gas flow frequency to reduce contact with particles on the platen while maintaining thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the workpiece is tightly clamped to the platen during thermal transitions, then thermal conductivity between the platen and workpiece is improved, but the workpiece backside is damaged by particles on the platen due to relative movement from expansion/contraction
Solution Approach 1:
The patent applies a dynamic clamping force that varies during the thermal transition process. The clamping force is reduced when the workpiece undergoes expansion or contraction to minimize contact with particles on the platen, and increased when thermal conductivity is prioritized. This dynamic adjustment resolves the contradiction between maintaining good thermal contact and preventing backside damage during dimensional changes.
Solution Approach 2:
The system employs periodic modulation of the clamping force in sync with the thermal transition cycles of the workpiece. By applying lower clamping force during expansion/contraction phases and higher clamping force during stable phases, the system periodically adjusts the contact between workpiece and platen to prevent damage while maintaining thermal efficiency overall.
2Object-affected harmful factors
If the clamping force is reduced to minimize backside damage, then particle contact is decreased, but thermal conductivity between the platen and workpiece deteriorates
Solution Approach 1:
Rather than maintaining a static low clamping force, the system dynamically adjusts the clamping force to be low only during specific phases of thermal transition when expansion/contraction occurs, and high during phases when thermal conductivity is critical. This temporal differentiation allows the system to achieve both protection and thermal efficiency.
Solution Approach 2:
The clamping force is periodically modulated to match the thermal transition cycle of the workpiece. During periods when the workpiece is expanding or contracting, the clamping force is reduced to prevent damage. During periods when the workpiece is thermally stable, the clamping force is increased to ensure good thermal contact, thus achieving both objectives through periodic variation.
3Object-affected harmful factors
If the workpiece is allowed to expand/contract freely during thermal transitions, then backside damage is minimized, but the time to bring the workpiece to desired temperature increases
Solution Approach 1:
The system dynamically controls the clamping force rather than leaving it static or completely releasing it. By maintaining moderate to high clamping force during stable thermal phases, the system ensures good thermal contact and efficient heating/cooling. During expansion/contraction phases, the clamping force is temporarily reduced to allow free dimensional change without damage, thus minimizing both damage and time loss.
Solution Approach 2:
The periodic modulation of clamping force synchronizes with the thermal transition process. During phases when rapid temperature change occurs and expansion/contraction is expected, the clamping force is reduced to allow free movement. During phases when thermal equilibrium is approached and dimensional stability increases, the clamping force is increased to maintain thermal contact, thereby optimizing both protection and heating/cooling efficiency.
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 damage to the backside of the workpiece during thermal transitions, maintaining efficient temperature control and reducing production costs by preventing scratches and gouges.
Implementation Method 1
one or more electrodes disposed in the platen to create a clamping force to hold the workpiece to the top surface
Implementation Method 2
the modulation of the backside gas pressure still permits good thermal conductivity between the platen and the workpiece
Data Source
AI summary
A system and method for minimizing the damage to the backside of a workpiece disposed on a platen during thermal transitions is disclosed. The system includes a controller that modulates the clamping voltage and backside gas pressure during the thermal transition. By modulating the clamping voltage, the workpiece may not be as tightly held to the platen at certain times, thus minimizing damage that may be caused by particles resident on the top surface of the platen. Furthermore, the modulation of the backside gas pressure still permits good thermal conductivity between the platen and the workpiece.