Electrostatic Reticle Clamp with Thermoelectric Cooling
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Solution Overview
Problem
Lithographic apparatuses face challenges in preventing heat-induced deformation of patterning devices due to EUV radiation, which can lead to loss of contrast and heat damage, and conventional coolant-based cooling systems are prone to leaks and poor thermal conductivity.
Innovation Solution
An electrostatic clamp with cooling elements aligned with burls is used to secure the reticle, employing thermoelectric or thermo-tunneling cooling to dissipate heat and maintain the reticle at a stable temperature, while an intermediate layer enhances adhesion to the chuck, and the clamp can be formed from materials like cordierite for improved thermal conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If coolant-based cooling systems are used to dissipate heat from the reticle, then heat dissipation is achieved, but the system becomes prone to leaks and has poor thermal conductivity
Solution Approach 1:
The patent replaces the mechanical coolant-based cooling system with an electrostatic cooling system. The electrostatic clamp generates an electrostatic field that directly cools the reticle through dielectric heating and heat conduction, eliminating the need for physical coolant circulation and associated mechanical components, thereby eliminating leaks while improving thermal conductivity.
Solution Approach 2:
The patent changes the cooling mechanism from thermal conduction through coolant to electrostatic field interaction. By applying high voltage to the electrostatic clamp, the system creates strong electric fields that induce dielectric heating in the reticle and facilitate direct heat conduction to the clamp, fundamentally changing the thermal management approach.
2Temperature
If conventional coolant systems are used for cooling, then heat dissipation is provided, but thermal conductivity is poor
Solution Approach 1:
The patent replaces the mechanical coolant system with an electrostatic field-based cooling system. The electrostatic clamp creates strong electric fields that directly interact with the reticle's dielectric material, inducing efficient heat conduction pathways without the thermal resistance inherent in coolant systems.
Solution Approach 2:
The electrostatic clamp incorporates dielectric materials with high thermal conductivity properties in direct contact with the reticle. This composite structure combines the insulating properties needed for electrostatic operation with high thermal conductivity pathways for efficient heat dissipation.
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 heat-induced deformation of the reticle, maintains precise temperature control, and eliminates the drawbacks of conventional coolant systems by ensuring reliable and efficient heat dissipation without leaks, enhancing the stability and accuracy of the lithographic process.
Implementation Method 1
The cooling elements are configured to cause electrons to travel from the second surface of the first substrate to the first surface of the second substrate
Implementation Method 2
employing thermoelectric or thermo-tunneling cooling to dissipate heat and maintain the reticle at a stable temperature
Implementation Method 3
an electrostatic clamp configured to releasably hold the reticle
Data Source
AI summary
A lithographic apparatus is provided. The lithographic apparatus includes a reticle and an electrostatic clamp configured to releasably hold the reticle. The electrostatic clamp includes a first substrate having opposing first and second surfaces, a plurality of burls located on the first surface and configured to contact the reticle, a second substrate having opposing first and second surfaces. The first surface of the second substrate is coupled to the second surface of the first substrate. A plurality of cooling elements are located between the first surface of the second substrate and the second surface of the first substrate. The cooling elements are configured to cause electrons to travel from the second surface of the first substrate to the first surface of the second substrate. Each cooling element is substantially aligned with a respective burl.