Gas Bearing Electrostatic Chuck Frictionless Clamping
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional electrostatic clamps in semiconductor processing face challenges in maintaining proper clamping and temperature control while minimizing particulate contamination, especially during high-power ion implantations and scanned workpiece operations, where increased clamping forces can lead to frictional issues and contamination.
Innovation Solution
An electrostatic clamp with a clamping plate featuring a central region and an annulus region, utilizing a porous plate with gas supply and return orifices to create a cushioning gas flow, which balances electrostatic forces with gas pressure to maintain a frictionless interface and prevent contamination, while differential pumping grooves and seals ensure gas containment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If higher static backside cooling gas pressure is applied to attain higher cooling rate, then thermal performance is improved, but clamping force requirement increases leading to greater particulate contamination
Solution Approach 1:
The patent divides the clamping plate into two distinct regions: a central region with gas supply orifices for cooling and an annulus region for sealing and structural support. This segmentation allows the cooling gas to be delivered precisely where needed (central region) without requiring high pressure across the entire workpiece surface, thereby reducing friction-induced particulate contamination while maintaining effective cooling.
Solution Approach 2:
The patent implements local quality by providing cooling gas flow only in the central region through gas supply orifices, rather than uniformly across the entire workpiece surface. This localized cooling approach allows for effective heat removal with lower gas pressure, reducing the clamping force needed and consequently minimizing particulate contamination from friction.
2Reliability
If increased clamping force is applied to compensate for high gas pressure, then workpiece contact is maintained, but frictional forces increase causing particulate contamination
Solution Approach 1:
The patent utilizes pneumatic principles by introducing gas flow through orifices in the central region to create a cushioning effect between the clamping plate and workpiece. This gas cushion reduces direct mechanical contact and friction in the central region, thereby minimizing particulate contamination while maintaining workpiece contact stability through the combined electrostatic and gas pressure forces.
3Force
If electrostatic clamping is used to hold workpiece, then clamping capability is achieved, but thermal uniformity deteriorates due to contact pressure variations
Solution Approach 1:
The patent implements continuous useful action by maintaining a constant flow of cooling gas through the orifices in the central region. This continuous gas flow ensures uniform heat removal across the central area, compensating for variations in contact pressure and electrostatic clamping force, thereby improving thermal uniformity while maintaining effective clamping.
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
The solution provides improved clamping and thermal uniformity while significantly reducing backside particle contamination by maintaining a balanced force equilibrium between electrostatic attraction and gas pressure, ensuring efficient workpiece processing.
Implementation Method 1
a clamping voltage is typically applied between the wafer and the electrode, wherein the wafer is clamped against the chuck surface by electrostatic forces
Implementation Method 2
a cooling gas is statically presented within a gap between the workpiece and one or more recessed surfaces of the ESC, wherein the pressure of the gas is generally proportional to the heat transfer coefficient thereof within the gap
Data Source
AI summary
An electrostatic clamp is provided having a clamping plate, wherein the clamping plate has a central region and an annulus region. A plurality of gas supply orifices are defined in the central region of the clamping plate, wherein the plurality of gas supply orifices are in fluid communication with a pressurized gas supply, and wherein the pressurized gas supply is configured to provide a cushion of gas between the clamping surface and the workpiece in the central region of the clamping plate via the plurality of gas supply orifices. One or more gas return orifices defined in one or more of the central region and annulus region of the clamping plate, wherein the one or more gas return orifices are in fluid communication with a vacuum source, therein generally defining an exhaust path for the cushion of gas. A seal is disposed in the annulus region of the clamping plate, wherein the seal is configured to generally prevent a leakage of the cushion of gas from the central region to an environment external to the annulus region. One or more electrodes are further electrically connected to a first voltage potential to provide a first clamping force.