Front-to-Back Overlay Standard for In-Line Dual-Side Lithography
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Solution Overview
Problem
Current manufacturing processes for Advanced Integrated Circuit Substrates (AICS) lack a means to correlate and calibrate lithographic tools on opposite sides of a substrate, leading to misalignment of features on the front and back sides.
Innovation Solution
A metrology-standard panel (MSP) with patterned holes is used to calibrate two in-line lithographic tools, allowing for precise alignment of features on both sides of the substrate by measuring and adjusting overlay errors using a flipper unit and measurement tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If two in-line lithographic tools are used to pattern opposite sides of a substrate, then productivity is improved by enabling simultaneous front-side and back-side processing, but manufacturing precision deteriorates due to inability to correlate and calibrate the tools, leading to overlay misalignment
Solution Approach 1:
A metrology standard panel (MSP) with through-substrate holes serves as an intermediary reference object. The MSP is processed by both lithographic tools and measured by a metrology tool to establish correlation data. This mediator enables precision calibration between the two independent tools without requiring direct interaction between them, resolving the overlay alignment problem while maintaining high productivity
Solution Approach 2:
A feedback loop is established where the metrology tool measures actual hole locations in the MSP, compares them to intended locations, and generates overlay error data. This feedback is used to adjust and calibrate the lithographic tools' grids and alignment systems, ensuring that future processing achieves the required overlay precision while maintaining continuous production capability
2Manufacturing precision
If a metrology standard panel with through-substrate holes is used for calibration, then manufacturing precision is improved by enabling accurate overlay measurement, but device complexity increases due to additional calibration equipment and procedures
Solution Approach 1:
The metrology standard panel serves multiple functions: it acts as a calibration reference for both lithographic tools, provides measurement targets for the metrology tool, and validates the entire front-to-back overlay process. This multi-functionality reduces the need for separate calibration artifacts for each tool, simplifying the overall system despite the added calibration capability
Solution Approach 2:
The calibration system is designed to be self-calibrating through the MSP. The through-substrate holes provide inherent geometric references that automatically establish coordinate transformations between front and back sides. The system uses its own measurement data to generate correction factors, reducing dependence on external calibration services or complex manual adjustment procedures
Data Source
AI summary
Various examples herein describe an apparatus and related method to calibrate two in-line lithographic tools used as part of in-line, panel-production equipment. The two lithographic tools are used to expose opposing sides of a panel or substrate, such as, for example, an Advanced Integrated Circuit Substrates (AICS) panel or another type of panel or substrate, such as a copper-clad laminate (CCL) panel). The panel may be, for example, a flat-panel display or another substrate type. Other systems, apparatuses, and methods are also disclosed.