Hybrid Optical Electron Beam Lithography Co-Alignment
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Solution Overview
Problem
Current technologies face challenges in aligning optical and electron beam lithographic fabrication levels, as electron beam lithographic systems cannot register to current optical alignment structures, hindering the integration of both technologies for advanced semiconductor processing.
Innovation Solution
The method involves forming an electron beam alignment target with an electron back-scattering layer and a capping layer in a trench, along with an optical alignment target, allowing for co-alignment using a photomask with clear and opaque regions, and exposing a resist layer to both actinic radiation and electron beams to create patterns on a substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electron beam lithography is used to print images on very small pitches, then manufacturing precision is improved, but productivity deteriorates due to slow processing speed
Solution Approach 1:
The patent combines optical lithography and electron beam lithography into a hybrid fabrication process. Optical lithography is used for forming large-area alignment targets and initial patterns, while electron beam lithography is used for forming high-precision alignment marks on the same substrate. This merging allows the process to leverage the high productivity of optical lithography for bulk patterning while utilizing the high precision of electron beam lithography for critical alignment features, thereby resolving the contradiction between manufacturing precision and productivity.
2Productivity
If optical lithography is used for fast processing, then productivity is improved, but manufacturing precision deteriorates due to inability to print on very small pitches
Solution Approach 1:
The patent segments the lithographic fabrication process into distinct functional stages: optical lithography is used for forming the alignment target structure and initial device patterns where high speed is prioritized, while electron beam lithography is selectively applied for forming the alignment marks where high precision is critical. This segmentation allows each lithographic technique to be applied to the specific task for which it is most suitable, resolving the contradiction between productivity and manufacturing precision.
3Adaptability or versatility
If electron beam lithographic systems are made to register to optical alignment structures, then adaptability is improved, but device complexity increases due to system integration requirements
Solution Approach 1:
The patent introduces a dual alignment mark structure as an intermediary that bridges optical and electron beam lithographic systems. The alignment marks are formed with specific characteristics (high-Z material in trenches) that make them detectable by electron beam systems while being formed through a process that integrates with optical lithography workflows. This intermediary structure enables electron beam systems to register to optical alignment structures without requiring complex system-level integration, thereby improving adaptability while minimizing the increase in device complexity.
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 enables precise co-alignment of optical and electron beam lithographic levels, enhancing the capabilities of semiconductor processing by allowing for the registration of electron beam lithography to optical structures, thereby improving the merging of both technologies.
Implementation Method 1
the electron beam alignment target comprising an electron back-scattering layer in a bottom of a trench
Implementation Method 2
the opaque regions substantially blocking the actinic radiation and the clear regions substantially transmitting the actinic radiation
Data Source
Figure 1A~1C
Figure 1D~1F
Figure 1G~1I
AI summary
A method for aligning a first set of features of a fabrication level of an integrated circuit chip to an electron beam alignment target including a high atomic weight layer formed in a substrate and forming the first set of features using electron beam lithography and for aligning a second set of features of the same fabrication level of the integrated circuit chip to an optical alignment target formed in the substrate and forming the second set of features using photolithography, the optical alignment target itself is aligned to the electron beam alignment target. Also a method of forming and a structure of the electron beam alignment target.