Critical Dimension Uniformity Tuning via Mask Density Flare Correction
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Solution Overview
Problem
Existing photolithography techniques face challenges in achieving uniform critical dimensions (CDs) due to flare, which results from unwanted radiation exposure, leading to variations in feature sizes and potential defects.
Innovation Solution
The method involves generating a mask density map, a flare map, and a critical dimension modification map based on the photomask design. These maps are used to adjust the exposure patterns, allowing for a second exposure process to correct for flare and ensure uniform CDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single exposure process is used, then the process is simple and fast, but critical dimension uniformity deteriorates due to flare
Solution Approach 1:
The exposure process is divided into two separate exposure steps: a first exposure that applies a first pattern of radiation, and a second exposure that applies a second pattern of radiation. This segmentation allows each exposure to be optimized for different purposes, with the second exposure specifically targeting flare correction in regions where the first exposure caused excessive radiation accumulation, thereby improving critical dimension uniformity while managing process complexity
Solution Approach 2:
The method performs preliminary mapping of the photomask to identify regions with high feature density that are prone to flare, generates a flare map predicting excessive radiation areas, and creates a correction pattern before the actual exposure. This preliminary analysis and pattern generation enable the second exposure to precisely target and correct flare issues, improving manufacturing precision while maintaining reasonable process complexity
2Manufacturing precision
If exposure energy is increased to ensure complete pattern transfer, then pattern transfer completeness is improved, but flare effects worsen causing CD variations
Solution Approach 1:
The correction pattern applied in the second exposure is spatially varying, with different radiation doses applied to different regions of the substrate based on the generated flare map. Regions predicted to receive excessive radiation during the first exposure receive reduced or no additional exposure, while other regions receive appropriate exposure doses. This local quality adjustment ensures complete pattern transfer where needed while preventing flare-induced CD variations in sensitive regions
Solution Approach 2:
The method converts the harmful flare radiation effect into a beneficial correction mechanism by using the same radiation source to both create and correct the problem. The second exposure uses controlled radiation to deliberately overexpose certain regions, which compensates for and corrects the unwanted flare effects from the first exposure, thereby improving critical dimension uniformity and pattern transfer completeness
3Manufacturing precision
If multiple exposure patterns are applied, then critical dimension uniformity is improved, but total exposure energy increases
Solution Approach 1:
The second exposure applies radiation selectively and partially, only to regions identified in the flare map as needing correction. Rather than applying a uniform additional exposure across the entire substrate, the method concentrates the second exposure energy only where flare correction is needed, based on the spatially varying correction pattern. This partial action approach improves critical dimension uniformity while minimizing the increase in total exposure energy
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 enhances the precision of feature development, improves critical dimension uniformity, and reduces the total exposure energy, thereby minimizing defects and maintaining a smaller process window.
Implementation Method 1
coating a first surface of the substrate with a photosensitive resist; exposing the first surface of the substrate to a first pattern of radiation at the predetermined wavelength
Implementation Method 2
generating a mask density map based on a photomask, the mask density map spatially mapping transparent regions of the photomask and blocking regions of the photomask that block radiation at a predetermined wavelength
Data Source
AI summary
A method of processing a substrate, including generating a mask density map based on a photomask, the mask density map spatially mapping transparent regions of the photomask and blocking regions of the photomask that block radiation at a predetermined wavelength; generating a flare map based on the mask density map, the flare map spatially indicating a projected amount of received radiation in excess of a desired amount of radiation at each coordinate location on the photomask; and generating a critical dimension modification map based on the flare map, the critical dimension modification map including a modification energy dosage for each coordinate location on the photomask.