Hybrid Electrostatic Chuck for Reticle Flatness Control
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Solution Overview
Problem
Existing electrostatic chucks in extreme ultraviolet lithography (EUVL) systems may not generate sufficient force to flatten the reticle surface adequately, leading to surface unevenness and image placement errors on semiconductor wafers due to particles between the reticle and the chuck.
Innovation Solution
An electrostatic chuck design incorporating a Coulomb electrode assembly and a Johnsen-Rahbek (J-R) electrode assembly, with a control system that selectively applies voltages to generate both Coulomb and J-R forces to attract and clamp the reticle, ensuring improved flatness and particle flattening, and reducing power consumption during the exposure process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single electrostatic chuck is used, then the device is held in place, but the chucking surface cannot achieve sufficient flatness when particles are present between the device and the chuck
Solution Approach 1:
The electrostatic chuck is divided into two separate electrode assemblies: a Coulomb electrode assembly and a Johnsen-Rahbek (J-R) electrode assembly. Each assembly generates a different type of electrostatic force that acts on particles in distinct ways. The Coulomb electrode generates long-range attractive forces that pull particles toward the chucking surface, while the J-R electrode generates short-range clamping forces that crush and flatten particles once they are in contact with the surface. This segmentation allows the system to address the particle problem at multiple stages of the particle management process.
Solution Approach 2:
The system changes the parameters of electrostatic force generation by using two different electrode configurations with distinct electrical characteristics. The Coulomb electrode operates at a different voltage and spacing configuration compared to the J-R electrode, creating forces with different ranges and magnitudes. This parameter change enables the system to adapt its force characteristics to match the specific needs of particle removal and flattening at different distances from the chucking surface.
2Manufacturing precision
If higher electrostatic force is applied to flatten the reticle surface, then surface flatness improves, but power consumption and heat generation increase
Solution Approach 1:
The electrostatic force generation is segmented into two distinct functions performed by separate electrode assemblies. The Coulomb electrode assembly handles the initial particle attraction and reticle flattening requiring higher forces, while the J-R electrode assembly maintains the flattened state with lower clamping forces. This segmentation allows the system to apply high force only when necessary for particle removal, rather than continuously applying high force, thereby reducing overall power consumption.
Solution Approach 2:
The control system operates the Coulomb and J-R electrode assemblies in a sequenced manner rather than simultaneously at full power. The Coulomb electrode is activated first to attract and flatten particles, then the J-R electrode takes over for maintenance clamping. This periodic activation pattern reduces the cumulative power consumption compared to continuous high-force application, while still achieving the required surface flatness.
3Object-affected harmful factors
If the Coulomb electrode assembly is positioned closer to the chucking surface, then particle attraction effectiveness improves, but the risk of electrical discharge increases
Solution Approach 1:
The electrode system is segmented into two assemblies with different positioning and function. The Coulomb electrode is positioned closer to the chucking surface to maximize its long-range attractive force on particles, while the J-R electrode is positioned farther away to provide stable clamping without the same discharge risk. This spatial segmentation allows each electrode to operate in its optimal position without compromising system reliability.
Solution Approach 2:
The dielectric chucking surface acts as an intermediary between the Coulomb electrode and the reticle. It provides electrical insulation that prevents direct electrical discharge between the closely-spaced Coulomb electrode and the reticle, while still allowing the electrostatic forces to act on particles. This intermediary layer enables the Coulomb electrode to operate at close proximity without the harmful effects of electrical breakdown.
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 effectively reduces non-flatness of the reticle surface, enhances the quality and density of semiconductor wafers by ensuring better retention and flattening, while minimizing power consumption and heat generation during the exposure process.
Implementation Method 1
the control system directs a first voltage to the Coulomb electrode assembly to generate a Coulomb type force that attracts the device towards the chucking surface
Implementation Method 2
the control system directs a second voltage to the J-R electrode assembly to generate a J-R type force that clamps the device to the chucking surface
Implementation Method 3
the chucking surface is made of a dielectric having a relatively high resistance
Data Source
AI summary
An electrostatic chuck (230) for holding a device (200) includes a chuck body (244), a Coulomb electrode assembly (246), a Johnsen-Rahbek (J-R) electrode assembly (248), and a control system (224). The chuck body (244) includes a chucking surface (250) that engages the device (200), and the chuck body (244) is made of a dielectric having a relatively high resistance. The J-R electrode assembly (248) is positioned spaced apart from the chucking surface (250). The Coulomb electrode assembly (246) is also positioned spaced apart from the chucking surface (250). The control system (224) selectively directs a first voltage to the J-R electrode assembly (248) to generate a J-R type force that attracts the device (200) towards the chucking surface (250), and selectively directs a second voltage to the Coulomb electrode assembly (246) to generate a Coulomb type force that also attracts the device (200) towards the chucking surface (250). With this design, both the J-R type force and the Coulomb type force are used to concurrently attract the device (200) against the chucking surface (2500. As a result thereof, the electrostatic chuck (230) is better able to reduce non-flatness of the device (200), and/or crush any particles positioned between the device (200) and the chucking surface (250).