Immersion Lithography Laser Pulse Stretcher for Compact Footprint
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Solution Overview
Problem
High-power pulsed DUV lasers used in integrated circuit manufacturing require improved pulse stretching to meet increasing energy demands for new lithography processes, while maintaining a compact footprint and minimizing optical damage from high peak intensities.
Innovation Solution
A pulsed gas discharge laser system with a pulse stretcher module that increases the number of peaks in the output pulse and reduces peak intensity by passing the output pulses through a pair of optical delay paths in series, using unequal length delay paths and imaging relay mirrors to achieve enhanced Time Integral Squared (TIS) magnification and maintain system compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If pulse stretching is improved to meet higher energy requirements, then pulse length is extended and peak intensity is reduced, but the system footprint tends to increase
Solution Approach 1:
The patent combines two delay paths into a single shared optical tower structure, where mirrors and optical components are共用 between the two delay paths. This merging of resources allows the pulse stretcher to achieve the required pulse length extension while occupying less physical space than would be required with completely separate delay paths.
Solution Approach 2:
The patent employs a three-dimensional optical tower configuration where delay paths are arranged in multiple levels and directions. By utilizing vertical and lateral spatial dimensions within the tower structure, the system achieves long optical path lengths without proportionally increasing the horizontal footprint, effectively packing more optical path length into a compact volumetric space.
2Object-affected harmful factors
If pulse stretching is increased to reduce peak intensity, then optical damage is mitigated, but device complexity increases
Solution Approach 1:
The pulse stretching function is divided into two separate delay paths that operate in sequence. Each delay path contributes to the overall pulse length extension and peak intensity reduction, allowing the system to achieve the required damage mitigation through distributed stretching rather than requiring a single complex delay mechanism.
Solution Approach 2:
The optical tower structure serves multiple functions simultaneously: it houses mirrors for both delay paths, provides structural support, enables compact packaging, and facilitates alignment. This multi-functionality reduces the need for additional specialized components, thereby managing device complexity while achieving the pulse stretching required to mitigate optical damage.
3Manufacturing precision
If unequal length delay paths are used to enhance TIS magnification, then performance is improved, but alignment precision requirements increase
Solution Approach 1:
The patent deliberately employs unequal length delay paths within the optical tower, where the first and second delay paths have different optical path lengths. This asymmetric configuration is designed to achieve specific TIS magnification characteristics required for the application, accepting that it will impose stricter alignment requirements compared to symmetric equal-length paths.
Solution Approach 2:
The shared optical tower structure acts as an intermediary framework that accommodates both unequal delay paths and provides a stable reference frame for alignment. The tower's rigid structure and predefined mirror mounting positions serve as intermediaries that help manage and control the alignment precision requirements imposed by the asymmetric path lengths.
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
The solution effectively extends pulse length and reduces peak intensity, mitigating optical damage and enhancing the laser system's performance to meet higher energy requirements while maintaining a compact footprint, thus supporting advanced lithography processes.
Implementation Method 1
a pulse stretcher increasing the number of peaks in the output pulse and decreasing the average peak intensity of each of the output pulses by passing the output pulses through a pair of optical delay paths in series
Implementation Method 2
a first beam splitter operatively connected with the first delay path and a second pulse stretcher operatively connected with the second delay path
Implementation Method 3
a plurality of mirrors defining the respective optical delay path including mirrors located in the first tower and in the second tower
Data Source
AI summary
An apparatus and method which may comprise a pulsed gas discharge laser which may comprise a seed laser portion; an amplifier portion receiving the seed laser output and amplifying the optical intensity of each seed pulse; a pulse stretcher which may comprise: a first beam splitter operatively connected with the first delay path and a second pulse stretcher operatively connected with the second delay path; a first optical delay path tower containing the first beam splitter; a second optical delay path tower containing the second beam splitter; one of the first and second optical delay paths may comprise: a plurality of mirrors defining the respective optical delay path including mirrors located in the first tower and in the second tower; the other of the first and second optical delay paths may comprise: a plurality of mirrors defining the respective optical delay path including mirrors only in one of the first tower and the second tower.