EUV Exposure Apparatus Wafer Thermal Control
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Solution Overview
Problem
The increased output of EUV light exposure in semiconductor manufacturing leads to insufficient cooling of wafers in vacuum chambers, causing deformation and reduced alignment accuracy due to thermal effects, which existing cooling mechanisms struggle to address effectively.
Innovation Solution
An exposure apparatus with a wafer stage and temperature sensors on a silicon plate, where the exposure light is applied to both the wafer and the silicon plate, allowing the control apparatus to set an exposure order that minimizes wafer deformation by managing back surface temperatures and using cooling gases and coolants to maintain thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the output of EUV light source is increased to improve productivity, then exposure efficiency is improved, but wafer deformation occurs due to insufficient cooling
Solution Approach 1:
The patent applies preliminary cooling action by cooling the back surface of the wafer before exposure and between shots. The cooling mechanism is activated in advance to prevent thermal accumulation, and cooling continues between exposure shots to maintain wafer temperature within acceptable ranges, thereby preventing deformation while allowing high-output EUV exposure
Solution Approach 2:
The patent introduces a cooling gas (such as helium or nitrogen) as an intermediary substance between the wafer back surface and the cooling mechanism. This cooling gas acts as a thermal mediator that efficiently transfers heat from the wafer back surface to the cooling system, enabling effective heat dissipation during high-power EUV exposure without direct contact between the cooling mechanism and the wafer
2Temperature
If cooling gas flow is increased to improve cooling effectiveness, then wafer temperature control is improved, but vacuum environment is compromised due to particle attachment
Solution Approach 1:
The patent applies local quality by providing cooling only at the back surface of the wafer, which is the specific location where heat accumulation occurs. The cooling gas is introduced into the gap between the wafer back surface and the electrostatic chuck, creating a localized cooling zone that does not affect the overall vacuum environment. This localized approach allows effective temperature control without requiring high volumes of cooling gas that would compromise vacuum integrity
Solution Approach 2:
The patent uses inert cooling gases such as helium or nitrogen that are compatible with vacuum environments. These gases have low outgassing rates and do not react with vacuum chamber components, allowing them to be used for cooling while maintaining the vacuum environment. The inert nature of these gases prevents particle generation and contamination, enabling effective cooling without compromising vacuum quality
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 solution effectively suppresses wafer deformation during exposure processes, maintaining alignment accuracy and reducing the need for increased cooling gas, thus preserving the vacuum environment and preventing particle attachment on the electrostatic chuck.
Implementation Method 1
gas such as H2 is passed between the back surface of the wafer and the electrostatic chuck to release the heat of the wafer to the electrostatic chuck side
Implementation Method 2
a wafer is provided with energy from the EUV light and the like to generate heat
Data Source
AI summary
According to one embodiment, an exposure apparatus includes a wafer stage, an irradiation optical system, and a projecting optical system. The wafer stage includes a wafer clamp, and a plate clamp configured to hold a silicon plate having a predetermined film formed on a silicon substrate. A plurality of sensors configured to measure a back surface temperature of the silicon plate is placed on an upper surface side of the plate clamp. The projecting optical system applies exposure light to the silicon plate on the plate clamp upon exposure of the silicon plate.