Reticle Thermal Management for Lithography Overlay Precision
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Solution Overview
Problem
The accuracy of pattern transfer in semiconductor lithography is compromised due to reticle heating, leading to thermal distortion and increased overlay residual values, which affect the precision and yield of the manufacturing process.
Innovation Solution
Implementing a thermal management system in the reticle library that heats reticles to their saturation temperature before use, ensuring consistent thermal expansion and minimizing distortion during the exposure process, and using sample data to adjust parameters like optical unit positions for overlay compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If reticle is used during exposure process without thermal management, then exposure process can be performed, but reticle heating causes thermal distortion and overlay accuracy degradation
Solution Approach 1:
The system performs preliminary heating of the reticle in the reticle library before the reticle is transferred to the exposure area. This preliminary thermal treatment ensures the reticle reaches a stable temperature state in advance, preventing thermal distortion during the actual exposure process and maintaining pattern transfer accuracy.
Solution Approach 2:
A thermal management system comprising heating elements and temperature sensors is introduced as an intermediary between the reticle and its environment. This system actively controls the reticle temperature by providing heating capability and real-time temperature monitoring, thereby preventing thermal distortion without interfering with the exposure process.
2Manufacturing precision
If reticle temperature is controlled to prevent thermal distortion, then overlay accuracy is maintained, but additional thermal management equipment and process complexity are required
Solution Approach 1:
The thermal management functionality is merged into the existing reticle library structure. Heating elements and temperature sensors are integrated within the reticle library housing, combining the thermal management system with the reticle storage and handling infrastructure. This integration approach achieves temperature control while minimizing additional system complexity.
3Stability of the object's composition
If reticle is heated to saturation temperature before use, then thermal expansion is consistent and distortion is minimized, but additional heating time and energy consumption are required
Solution Approach 1:
The system employs temperature sensors to continuously monitor the reticle temperature and provides feedback to the heating elements. This closed-loop control ensures the reticle is heated only to the necessary saturation temperature and maintains it within a controlled range, preventing both under-heating (which would cause distortion) and over-heating (which would waste energy).
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 approach maintains precise pattern transfer accuracy by stabilizing reticle temperature and reducing thermal distortion, thereby improving the process yield and maintaining overlay residual values within acceptable limits.
Implementation Method 1
portions of the reticle absorb energy from the illumination beam
Implementation Method 2
the reticle experiences thermal deformations
Data Source
AI summary
A semiconductor processing method includes: selecting a target state of a reticle based on a given data set, wherein the given data set comprises temperature profiles of the reticle correlated to a target overlay performance, and the target state is a state in which a deformation of the reticle is substantially unchanged; regulating the reticle to reach the target state; and performing an exposure process on a target workpiece by using the reticle.