EUV Mirror Cleaning via Reflection Substrate
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Solution Overview
Problem
EUV exposure apparatuses face a decrease in exposure rate and productivity due to mirror haze caused by decomposed resist materials, which are not efficiently removed by existing cleaning methods.
Innovation Solution
The EUV exposure apparatus employs a reflection substrate with a multilayered film structure and a cleaning reticle to reflect EUV light onto mirrors, efficiently removing adhered decomposition products by varying reflection angles and diffraction patterns, allowing for targeted cleaning without disrupting the vacuum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gas or radical is supplied into the exposure apparatus to remove mirror haze, then the mirror reflectance is improved, but the adhesion material cannot be efficiently removed
Solution Approach 1:
The invention changes the physical parameters of the cleaning light by using EUV radiation with specific wavelengths (13.5 nm) and controlling the irradiation intensity and duration. This allows selective removal of adhesion materials based on their absorption characteristics at EUV wavelengths, achieving efficient cleaning while maintaining mirror reflectance
Solution Approach 2:
The invention replaces the chemical cleaning mechanism (gas or radical supply) with a physical cleaning mechanism using EUV light irradiation. This substitution enables more precise control over the cleaning process and selective removal of contaminants without the side effects of chemical reactions
2Productivity
If EUV light beam intensity is increased to improve exposure rate, then productivity is improved, but mirror haze accumulates faster
Solution Approach 1:
The invention implements continuous cleaning action by periodically irradiating the mirrors with EUV light during the exposure process. This continuous maintenance cleaning prevents haze accumulation even at high exposure rates, allowing sustained high productivity without reflectance degradation
Solution Approach 2:
The invention uses periodic EUV light irradiation cycles interspersed between exposure cycles to clean the mirrors. This periodic maintenance removes accumulated adhesion materials before they significantly degrade reflectance, enabling sustained high-speed operation
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 removes adhered materials from mirrors, maintaining mirror reflectance and improving exposure rate and productivity in semiconductor device manufacturing.
Implementation Method 1
an organic material as a resist material is decomposed by energy of the EUV irradiation light beam
Implementation Method 2
a reflection substrate with a multilayered film structure and a cleaning reticle to reflect EUV light onto mirrors
Implementation Method 3
varying reflection angles and diffraction patterns, allowing for targeted cleaning
Data Source
AI summary
According to one embodiment, an EUV exposure apparatus includes a mirror which reflects an EUV light beam irradiated from a light source and a wafer stage which is irradiated with the EUV light beam reflected by the mirror. When exposure of a first wafer is to be performed, the first wafer is mounted on the wafer stage, and the wafer stage allows the first wafer to be irradiated with the EUV light beam. In addition, when cleaning of the mirror is to be performed, the EUV light beam is reflected by a reflection substrate, and the wafer stage allows the mirror to be irradiated with the reflected light beam.