EUV Mask Defect Repair With Adaptive Dose Feedback
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Solution Overview
Problem
Existing methods for repairing defects in lithography masks, particularly EUV masks, fail to consider the dynamic changes in defect behavior during the repair process, leading to unpredictable outcomes and potential damage to the mask.
Innovation Solution
A method that involves performing a first repair step, analyzing the resulting topology change, and adjusting subsequent repair doses based on this change to achieve a desired defect topology, using iterative steps if necessary, to ensure accurate and reliable repair.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single repair dose is applied to the defect, then the repair process is simple and fast, but the repair precision and reliability are poor due to unpredictable defect behavior changes
Solution Approach 1:
The repair process transitions from a static single-dose approach to a dynamic multi-step approach where the repair dose is adjusted based on real-time feedback from topology measurements. The system continuously adapts the repair parameters according to the actual defect response, making the process dynamic and responsive to changing conditions.
Solution Approach 2:
The invention implements a feedback loop where the defect topology is measured before and after the repair step, the change is analyzed, and this information feeds back into determining the subsequent repair dose. This closed-loop control ensures that each repair step is optimized based on actual observed effects rather than predetermined fixed parameters.
2Reliability
If a high repair dose is applied to ensure complete defect removal, then the defect removal effectiveness is improved, but the risk of mask damage increases
Solution Approach 1:
Instead of applying a single high repair dose that might exceed the safe threshold and cause mask damage, the invention uses multiple partial repair doses. Each dose is calibrated to achieve a specific topology change without exceeding damage thresholds, and the cumulative effect of multiple controlled partial actions achieves complete defect removal safely.
Solution Approach 2:
The invention cushions against potential mask damage by implementing intermediate topology measurements between repair steps. These measurements serve as safety checks that allow the process to be paused or adjusted if approaching dangerous thresholds, preventing catastrophic mask damage while still achieving the desired repair outcome.
3Manufacturing precision
If multiple repair steps with dose adjustments are implemented, then the repair precision and mask safety are improved, but the repair time and process complexity increase
Solution Approach 1:
The invention performs preliminary action by measuring the defect topology before the repair process begins and using this information to calculate an optimized first repair dose. This preliminary characterization allows subsequent repair steps to be more efficient and targeted, reducing the total time required compared to trial-and-error approaches.
Solution Approach 2:
The repair process uses periodic action by implementing repair steps interspersed with measurement steps. Rather than continuous monitoring which would be time-consuming, the system periodically measures topology at key intervals (before repair, after repair), allowing efficient process control with minimal interruption to the overall repair timeline.
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 allows for precise control of the repair process, minimizing damage to the mask by dynamically adapting to changing conditions, ensuring accurate defect removal or deposition, and achieving the desired mask topology.
Implementation Method 1
A known method of removing dark defects is to use an electron beam directed directly at the defect to be repaired
Implementation Method 2
In conjunction with a precursor gas, also called process gas, which may be guided into the atmosphere of the mask to be repaired, it is possible to induce a reaction akin to a local etching operation by virtue of the incident electron beam
Implementation Method 3
Alternatively, it is also possible to choose the precursor gas used such that a deposition process can be induced on irradiation with the beam
Implementation Method 4
As a result, it is possible to deposit additional material on clear defects in order to locally reduce the transmittance of the mask
Data Source
AI summary
A method, a device and a computer program for repairing a defect of a mask for lithography, in particular an EUV mask, are described.A method of repairing a defect of a mask for lithography, in particular an EUV mask, comprises the following steps: (a.) carrying out a first repair step on the defect using a first repair dose, wherein the defect transitions from an initial topology to a first defect topology as a result; (b.) determining an influence of the first repair step on the topology of the defect; (c.) determining a second defect topology for the defect, which is intended to be achieved by way of a second repair step on the defect; and (d.) determining a second repair dose for the second repair step, at least in part on the basis of the determined influence of the first repair step on the topology of the defect and the second defect topology. The method may further comprise step (e.) of carrying out the second repair step using the second repair dose.