Hadamard Targets for Charged Particle Beam Alignment
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Solution Overview
Problem
Current charged particle beam lithography and inspection systems face challenges in achieving precise alignment and registration of patterns on semiconductor wafers, leading to increased pattern overlay errors and reduced yield rates due to beam positioning drift and thermal distortions.
Innovation Solution
The use of Hadamard targets distributed across the substrate surface allows for superior beam alignment and registration, enabling improved resolution, accuracy, and yield rates by providing unique patterns for calibration and column performance metrics, and allowing for rapid recalibration and precise positioning of beam columns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional alignment and registration methods are used, then the system structure remains simple, but beam positioning accuracy deteriorates due to beam positioning drift and thermal distortions
Solution Approach 1:
The alignment and registration system is segmented into multiple independent Hadamard targets distributed across the substrate surface, each providing localized alignment information. This segmentation allows the complex alignment problem to be divided into multiple simpler, independent measurements that can be processed separately and combined to achieve high overall accuracy without requiring a monolithic complex alignment system
Solution Approach 2:
Hadamard targets are written onto the substrate in advance before the actual lithography or inspection process. These pre-written targets serve as reference markers that enable rapid alignment and registration without requiring complex real-time adjustments during the main process, thereby improving beam positioning accuracy while keeping the operational system relatively simple
2Measurement precision
If multiple Hadamard targets are distributed across the substrate surface, then alignment and registration accuracy improves, but the substrate preparation complexity increases
Solution Approach 1:
The Hadamard targets serve multiple functions: they provide alignment references, registration markers, and calibration standards all in a single integrated pattern. This multi-functionality reduces the need for separate alignment structures and simplifies substrate preparation compared to using multiple different types of alignment features
Solution Approach 2:
The Hadamard transform converts alignment information into a specific mathematical pattern format that is highly sensitive to positional and rotational changes. By encoding alignment data in this transformed parameter space rather than simple geometric shapes, the system achieves high measurement precision through parameter analysis rather than through physically complex alignment structures
3Productivity
If rapid recalibration is performed using Hadamard targets, then productivity improves, but measurement precision may deteriorate due to increased processing speed
Solution Approach 1:
The Hadamard target system provides immediate feedback on beam positioning and alignment status through the unique correlation properties of Hadamard patterns. When the beam scans the target, the system rapidly detects positional deviations and generates correction signals, enabling fast iterative recalibration that maintains high precision through feedback control rather than through slow manual adjustment
Solution Approach 2:
Recalibration is performed periodically at strategically chosen intervals during the lithography or inspection process using the pre-written Hadamard targets. This periodic action allows the system to maintain high productivity by performing quick alignment checks and corrections only when necessary, rather than continuously, while still ensuring measurement precision is maintained throughout the process
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
Hadamard targets enhance beam alignment and registration accuracy, reduce pattern overlay errors, and improve yield rates by enabling precise calibration and column performance optimization, thus improving the overall fidelity and throughput of charged particle beam lithography and inspection processes.
Implementation Method 1
When writing a wafer (or other substrate), the columns emit electron beams at a power level sufficient to change certain properties of a resist layer coated on the substrate
Implementation Method 2
When inspecting a wafer, the columns emit electron beams (generally at a lower power level than when writing) and detect an image of the substrate surface caused by the resulting scattered electrons
Data Source
AI summary
The present application discloses methods, systems and devices for using charged particle beam tools to pattern and inspect a substrate. The inventors have discovered that it is highly advantageous to use patterns generated using the Hadamard transform as alignment and registration marks (Hadamard targets) for multiple-column charged particle beam substrate processing and inspection tools. Hadamard targets can be written to a substrate using charged particle beams performing, for example, resist-based lithography or resist-less direct processing. High-order Hadamard targets can also be patterned and imaged to obtain superior column performance metrics for applications such as super-rapid beam calibration DOE, column matching, and column performance tracking. Hadamard target blocks can be written highly locally to electrically functional pattern portions, or integrated into said pattern portions, thereby enabling re-registration local and contemporaneous to writing and improving beam targeting accuracy following re-registration. Superior alignment and registration, and column parameter optimization, allow significant yield gains.