Multi-Zone Heater Plate for Lithography CD Uniformity
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving uniform critical dimension (CD) control during lithography processes, leading to reliability issues and reduced device yield due to variations in wafer CD across the substrate surface.
Innovation Solution
A method and apparatus for controlling wafer CD uniformity using a multi-zone heater plate, where a CD map is obtained and correlated with the heater geometry, allowing for temperature adjustments based on temperature sensitivity of the photoresist to achieve target CD profiles, thereby ensuring spatial uniformity across the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a uniform temperature is applied across the entire wafer surface, then the heating process is simple to control, but the critical dimension uniformity across the wafer deteriorates
Solution Approach 1:
The heater plate is divided into multiple independently controllable zones (e.g., center zone, inner annular zone, outer annular zone) that can be adjusted to different temperatures. This segmentation allows each zone to compensate for spatial variations in critical dimension, achieving uniform CD across the wafer surface while maintaining manageable control through zoned temperature adjustment.
2Manufacturing precision
If the heater plate is divided into multiple zones with different temperatures, then the critical dimension uniformity is improved, but the control system complexity increases
Solution Approach 1:
Each heater zone is assigned a specific temperature profile optimized for its location on the wafer. The center zone, inner annular zone, and outer annular zone each receive tailored temperature control based on their respective contributions to critical dimension variation. This local quality approach achieves superior CD uniformity while the temperature adjustments remain intuitive and manageable.
3Productivity
If traditional single-temperature heating is used, then the process is fast and simple, but iteration steps to achieve optimal CD profile increase
Solution Approach 1:
The heater zones are pre-configured with optimal temperature profiles based on their spatial positions and their impact on critical dimension. This preliminary setup eliminates the need for multiple iterative adjustments during actual production, as the zoned heating system directly achieves the target CD profile in a single pass, significantly reducing optimization time and increasing throughput.
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 enhances CD uniformity, reduces iteration steps for achieving optimal profiles, and provides a framework for advanced process control, improving both lot-to-lot and wafer-to-wafer consistency while allowing for tailored CD distributions.
Implementation Method 1
a multi-zone heater plate, where a CD map is obtained and correlated with the heater geometry, allowing for temperature adjustments based on temperature sensitivity of the photoresist
Data Source
AI summary
A method of controlling wafer critical dimension (CD) uniformity on a track lithography tool includes obtaining a CD map for a wafer. The CD map includes a plurality of CD data points correlated with a multi-zone heater geometry map. The multi-zone heater includes a plurality of heater zones. The method also includes determining a CD value for a first heater zone of the plurality of heater zones based on one or more of the CD data points and computing a difference between the determined CD value for the first heater zone and a target CD value for the first heater zone. The method further includes determining a temperature variation for the first heater zone based, in part, on the computed difference and a temperature sensitivity of a photoresist deposited on the wafer and modifying a temperature of the first heater zone based, in part, on the temperature variation.