Phase Transition Heat Absorption for Wafer Thermal Stability
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Solution Overview
Problem
Modern lithography systems face challenges in heat transfer and stability due to increasing resolution and miniaturization, leading to temperature instability and positioning errors in wafers, especially in high-throughput and vacuum processing environments, where existing heat removal methods are insufficient.
Innovation Solution
A phase transition in a heat-absorbing material, such as hexadecane, is used to absorb heat from the wafer, combined with a heat-conducting material in a porous structure or emulsion, allowing for efficient and compact heat transfer without significant temperature increase, and is applied at room temperature for enhanced operational compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional heat removal methods are used, then the system structure remains simple, but the heat absorption capacity and temperature stability are insufficient
Solution Approach 1:
The patent applies phase transition materials (PCM) that undergo phase change at or near room temperature to absorb heat from the wafer. The phase transition process absorbs latent heat efficiently, providing superior temperature stability compared to conventional cooling methods. The PCM is applied directly to the wafer backside, creating a compact heat management system that maintains temperature without complex active cooling mechanisms.
Solution Approach 2:
The invention uses composite material structures combining phase transition materials with heat conducting materials. The PCM provides latent heat absorption during phase change, while the heat conducting material (such as metal foils or ceramic layers) ensures efficient thermal coupling with the wafer. This composite approach achieves both high heat absorption capacity and effective heat transfer in a compact configuration.
2Productivity
If high-throughput lithography is implemented, then productivity increases, but heat generation increases and temperature stability deteriorates
Solution Approach 1:
The phase transition material provides continuous heat absorption throughout the lithography process. As the wafer moves through the exposure area, the PCM continuously absorbs heat via phase change, maintaining temperature stability even during high-throughput operation. The material remains in place and continues to function throughout the entire processing sequence without requiring active control or replenishment.
Solution Approach 2:
The latent heat absorption during phase transition provides a large heat capacity in a compact form factor, enabling the system to handle the increased heat generation from high-throughput processing. The phase change process absorbs heat at constant temperature, providing passive thermal regulation that maintains stability regardless of processing speed or heat generation rate.
3Manufacturing precision
If vacuum processing is used, then lithography precision improves, but heat transfer capability deteriorates
Solution Approach 1:
The patent replaces conventional convection-based cooling systems with a phase transition-based thermal management system. The PCM absorbs heat through molecular rearrangement during phase change, a process that does not depend on gas molecules or convection currents. This substitution allows effective heat absorption in vacuum conditions where conventional cooling methods fail.
Solution Approach 2:
The phase transition mechanism provides heat absorption through latent heat, a process independent of the surrounding environment's gas pressure. The PCM undergoes phase change at constant temperature, absorbing heat directly from the wafer through thermal conduction, which remains effective in vacuum conditions. This eliminates the need for gas-mediated heat transfer.
4Reliability
If heat absorbing material volume is increased, then heat absorption capacity improves, but device size and complexity increase
Solution Approach 1:
The phase transition material provides exceptional heat absorption capacity per unit volume through latent heat absorption. During phase change, the PCM absorbs large amounts of heat at constant temperature, providing superior heat density compared to conventional cooling materials. This allows compact heat management with minimal material volume.
Solution Approach 2:
The invention exploits the change in thermal parameters during phase transition to achieve high heat absorption capacity. The latent heat of fusion or vaporization provides a large heat capacity in a compact form, and the phase change occurs at a specific temperature that can be selected to match the operating conditions. This parameter exploitation enables compact, high-capacity heat absorption.
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 method effectively limits wafer expansion and maintains temperature stability, reducing positioning errors and enabling high-throughput lithography without compromising system complexity or throughput, even in vacuum conditions.
Implementation Method 1
heat removal is realised by the use of a phase transition in a heat absorbing material that is brought into thermal contact with said target
Implementation Method 2
A phase transition in a heat-absorbing material, such as hexadecane, is used to absorb heat from the wafer
Implementation Method 3
combined with a heat-conducting material in a porous structure or emulsion, allowing for efficient and compact heat transfer
Data Source
Figure 1~2A
Figure 2B~5
Figure 6~7
AI summary
The present invention relates to a lithography system for projecting an image or an image pattern on to a target such as a wafer. Energy that is accumulated in the target by the projection of the image or image pattern is removed from said target, such that expansion by local and/or overall heating is limited to a relevant pre-defined value, and wherein such heat removal is realised by the use of a phase transition in a heat absorbing material that is brought into thermal contact with said target. As a further elaboration, such material may be applied in combination with a further material having a superior coefficient of heat transport, and may be incorporated in an emulsion comprising a material having a superior coefficient of heat transfer. Said material may e.g. be adhered to a bottom face of the target, and may also be included in a frame.