Reflective EUV Mask Placement Correction
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Solution Overview
Problem
Current methods struggle to accurately determine the placement of pattern elements on reflective photolithographic masks, particularly in extreme ultraviolet (EUV) wavelength ranges, due to internal stresses and rear-side unevennesses, which affect overlay precision and semiconductor component production yields.
Innovation Solution
A device and method that include means to determine surface unevenness data of the rear and front sides of reflective photolithographic masks, as well as their mounts, in a measurement environment. This data is then used to calculate the accurate placement of pattern elements in the operating environment, accounting for the effects of unevenness and internal stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If reflective photolithographic masks are used in EUV wavelength range, then imaging precision of critical structure elements is improved, but internal stresses and rear-side unevennesses cause placement errors that worsen overlay accuracy
Solution Approach 1:
The patent measures rear-side unevenness and pattern element placements before the mask enters operation, and computes correction values in advance. This preliminary measurement and computation of correction data allows the system to compensate for placement errors caused by internal stresses and rear-side unevennesses before they affect production overlay accuracy.
Solution Approach 2:
The patent implements a feedback mechanism where measured rear-side unevenness data and placement data from the measurement environment are used to compute correction values that are then applied to improve placement accuracy in the operating environment. This closed-loop approach continuously refines placement precision based on actual measured deviations.
2Ease of operation
If measurement is performed in a different environment than operation, then measurement accessibility is improved, but environmental differences cause errors that worsen placement determination accuracy
Solution Approach 1:
The patent introduces correction values as an intermediary that bridges the measurement environment and operating environment. By measuring in the accessible measurement environment and then computing correction values that account for environmental differences, the system transfers accurate placement information to the operating environment where the mask actually functions.
Solution Approach 2:
The patent accounts for parameter changes between measurement and operating environments by computing correction values that compensate for differences in mounting conditions, gravitational effects, and environmental parameters. This allows accurate placement determination despite performing measurements in a different environment than operation.
3Device complexity
If conventional optical measurement methods are used, then measurement simplicity is improved, but inability to account for rear-side unevennesses worsens placement measurement accuracy
Solution Approach 1:
The patent segments the measurement process into two independent parts: measuring rear-side unevenness separately from measuring pattern element placements. This segmentation allows each measurement to be optimized independently and enables the computation of correction values that specifically address rear-side unevenness effects on placement accuracy.
Data Source
AI summary
The present application relates to a device for determining placements of pattern elements of a reflective photolithographic mask in the operating environment thereof, wherein the device comprises: (a) at least one first means configured for determining surface unevenness data of a rear side of the reflective photolithographic mask and/or surface unevenness data of a mount of the reflective photolithographic mask in a measurement environment that does not correspond to the operating environment; (b) at least one second means configured for determining placement data of the pattern elements in the measurement environment; and (c) at least one computing unit configured for calculating the placements of the pattern elements of the reflective photolithographic mask in the operating environment from the determined surface unevenness data of the rear side and/or of the mount and the determined placement data.