Dual-Stage PEB Heating for EUV Resist Acid Diffusion
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Solution Overview
Problem
Conventional photolithography methods for EUV resist patterns face challenges in acid diffusion and chemical reaction progression due to low EUV light intensity, leading to reduced throughput in wafer processing.
Innovation Solution
A substrate processing method involving a dual heating process, where the substrate is first heated at a high temperature to promote acid diffusion, followed by a lower temperature heating step to enhance chemical reactions in the resist film, with a temperature difference of 20° C. to 60° C. and heating times of 10 to 30 seconds, to improve resist sensitivity and pattern formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional single-stage PEB heating is used, then processing simplicity is maintained, but acid diffusion and chemical reaction progression are insufficient due to low EUV light intensity
Solution Approach 1:
The heating process is divided into two distinct stages: a first heating process at a first heating temperature and a second heating process at a second heating temperature. This segmentation allows each stage to perform a specific function - the first stage promotes acid diffusion while the second stage enhances chemical reactions, thereby resolving the contradiction between improving productivity through better acid diffusion and chemical reaction progression and maintaining processing simplicity.
Solution Approach 2:
The first heating process is performed preliminarily to promote acid diffusion before the second heating process enhances chemical reactions. This preliminary action ensures that the acid is adequately distributed throughout the resist film before the chemical reaction enhancement stage, thereby improving overall productivity without excessive complexity.
2Temperature
If higher heating temperature is used, then acid diffusion is promoted, but chemical reaction progression may be insufficient
Solution Approach 1:
The heating process is segmented into two stages with different temperature levels. The first heating process uses a higher first heating temperature to promote acid diffusion, while the second heating process uses a lower second heating temperature (but still higher than process atmosphere temperature) to enhance chemical reactions. This segmentation resolves the contradiction by assigning different temperature optimization goals to different stages.
Solution Approach 2:
The heating temperature parameter is changed between two distinct stages. The first heating temperature is set higher to maximize acid diffusion, then changed to a lower second heating temperature optimized for chemical reaction progression. This parameter change strategy allows each stage to operate at its optimal temperature, resolving the contradiction between promoting acid diffusion and ensuring chemical reaction progression.
3Reliability
If longer heating time is used, then chemical reaction progression improves, but throughput of wafer process decreases
Solution Approach 1:
The heating process is segmented into two shorter stages rather than one long stage. Each stage is optimized for its specific function and can be completed in a shorter time period. The first heating process promotes acid diffusion while the second heating process enhances chemical reactions, both in reduced time frames. This segmentation resolves the contradiction by achieving both acid diffusion and chemical reaction progression through multiple shorter heating cycles rather than a single prolonged heating process.
Solution Approach 2:
The two heating processes are performed in continuous sequence without interruption. The first heating process immediately transitions into the second heating process, maintaining continuous useful action on the resist film. This continuity ensures that both acid diffusion and chemical reaction progression occur without idle time, thereby improving throughput while maintaining reliable chemical reaction progression.
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 resist sensitivity and prevents Line Width Roughness (LWR) deterioration, thereby increasing the throughput of forming EUV resist patterns on substrates while maintaining efficient processing and minimizing system footprint.
Implementation Method 1
a first heating process for heating the substrate at a first heating temperature and a second heating process for heating the substrate at a second heating temperature lower than the first heating temperature and higher than a temperature of a process atmosphere
Implementation Method 2
the acid produced from the resist for EUV is not easily diffused and therefore the chemical reaction in the resist does not easily progress
Data Source
AI summary
A PEB unit has a first heat plate and a second heat plate. After an exposure process for a resist film for EUV on a wafer and before a development process, the PEB unit heats the wafer through the first heat plate at a first heating temperature. A heating time through the first heat plate is not less than 10 seconds and not more than 30 seconds. Thereafter, the PEB unit heats the wafer through the second heat plate at a second heating temperature lower than the first heating temperature. A temperature difference between the first heating temperature and the second heating temperature is not less than 20° C. and not more than 60° C.