Exposure Method Aberration Control for Semiconductor Focal Depth
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Solution Overview
Problem
Current semiconductor manufacturing techniques face challenges in maintaining dimensional control and production yield due to focal depth loss and exposure margin reduction caused by sparse and dense best focus differences and standing waves, which are not effectively addressed by existing countermeasures.
Innovation Solution
An exposure method that adjusts the aberration of a projection lens based on the optical characteristics of a lower-layer film and photoresist to ensure the best focus positions for both sparse and dense patterns fall within a predetermined range, using a multilayer film system to minimize reflectivity and optimize exposure conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the exposure is performed with conventional methods, then the exposure process can be completed, but the dimensional control is lowered due to loss of focal depth and exposure margin
Solution Approach 1:
The patent applies preliminary action by pre-calculating and setting the spherical aberration amount before exposure based on the film structure (photoresist thickness and lower-layer film reflectivity). This allows the best focus positions for both dense and isolated patterns to be optimized in advance, ensuring dimensional control is maintained without requiring real-time adjustments during exposure, thus improving both precision and yield.
Solution Approach 2:
The patent changes the spherical aberration parameter of the projection lens to compensate for the inter-pattern best focus difference. By adjusting the spherical aberration amount according to the specific film structure, the system optimizes the exposure conditions to maintain consistent best focus positions across different pattern densities, thereby improving dimensional control and reducing focus shift variations.
2Manufacturing precision
If the spherical aberration is adjusted to optimize best focus positions, then the focal depth is improved, but the device complexity increases
Solution Approach 1:
The patent changes the spherical aberration parameter of the projection lens to compensate for the inter-pattern best focus difference. By adjusting the spherical aberration amount according to the specific film structure, the system optimizes the exposure conditions to maintain consistent best focus positions across different pattern densities, thereby improving dimensional control and reducing focus shift variations.
Solution Approach 2:
The patent replaces complex mechanical focus adjustment mechanisms with optical aberration control. Instead of physically adjusting focus positions for different patterns, the system uses spherical aberration to optically compensate for focus differences, simplifying the control system while maintaining precision.
3Manufacturing precision
If a multilayer antireflection film is used to reduce standing waves, then the exposure margin is improved, but the manufacturing cost increases
Solution Approach 1:
The patent optimizes the exposure process by adjusting the spherical aberration parameter based on the existing film structure, including the lower-layer film's reflectivity. This allows the system to compensate for standing wave effects and inter-pattern focus differences through optical parameter adjustment rather than requiring additional expensive multilayer antireflection films, thereby maintaining exposure margin improvement while controlling manufacturing costs.
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 reduces the best focus difference between sparse and dense patterns, enhancing focal depth and production yield by adjusting the aberration of the projection lens and optimizing the multilayer film system, thereby improving the precision and efficiency of semiconductor device manufacturing.
Implementation Method 1
projecting images of the first mask pattern and second mask pattern onto a wafer through a projection lens
Implementation Method 2
exposure light reflected at an interface on a lower side of the photoresist
Implementation Method 3
interference between exposure light incident to the photoresist and exposure light reflected at an interface on a lower side of the photoresist
Data Source
AI summary
An exposure method has irradiating a mask with light based on an exposure performing condition, a first mask pattern and a second mask pattern being formed in the mask, and projecting images of the first mask pattern and second mask pattern onto a wafer through a projection lens, a lower-layer film material and a photoresist being sequentially laminated on the wafer, wherein the exposure performing condition is a condition on which, when exposure is performed on a predetermined exposure condition, the predetermined exposure condition is adjusted such that a difference between a wafer position at which a best focus is obtained for the image of the first mask pattern and a wafer position at which a best focus is obtained for the image of the second mask pattern falls within a predetermined range, the wafer position of the first mask pattern and the wafer position of the second mask pattern being predicted using film thicknesses and optical characteristics of the photoresist and the lower-layer film material.