Exposure Parameter Adjustment for Semiconductor Pattern Accuracy
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Solution Overview
Problem
Conventional methods for setting optimal exposure dose and focus in photolithography fail to achieve intended pattern shapes in mass-produced semiconductor wafers due to differences in resist optical constants and coating thickness between test and production wafers, leading to inaccurate measurements and pattern deformation.
Innovation Solution
The exposure method involves measuring and controlling the optical constants and coating thickness of both test and production wafers using spectroscopic ellipsometry, and calculating a relational equation to determine optimal exposure dose and focus through multivariate analysis, ensuring accurate pattern formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional methods use test wafers to determine optimal exposure dose and focus, then exposure parameters can be set efficiently, but the pattern shape deviates in mass-produced wafers due to differences in resist optical constants and coating thickness
Solution Approach 1:
The invention measures and records the optical constants and coating thickness of the resist on production wafers before exposure in advance. This preliminary measurement allows the system to predict and compensate for variations in exposure parameters before actual production exposure occurs, thereby maintaining pattern shape accuracy while preserving production efficiency.
Solution Approach 2:
The invention dynamically adjusts exposure parameters (exposure dose and focus) based on the measured optical constants and coating thickness of the resist. By changing these parameters according to actual resist properties rather than using fixed test-wafer-derived values, the system maintains accurate pattern formation despite variations between test and production wafers.
2Ease of manufacture
If exposure parameters are optimized for test wafers, then the process is simple and fast, but the results cannot be applied accurately to production wafers with different resist properties
Solution Approach 1:
The invention modifies the exposure parameters based on the measured optical constants and coating thickness of the resist on production wafers. This parameter adjustment ensures that the exposure settings are specifically tailored to the actual resist properties, making the process reliable while maintaining simplicity through automated measurement and calculation.
Solution Approach 2:
The system incorporates feedback by measuring the actual resist properties on production wafers and using this information to adjust exposure parameters. This closed-loop approach ensures that the exposure settings are continuously optimized based on real measurements, improving reliability without significantly complicating the manufacturing process.
3Productivity
If the exposure dose and focus are set based on test wafer measurements, then initial exposure can be performed, but pattern deformation occurs in production due to resist property variations
Solution Approach 1:
The invention adjusts the exposure dose and focus parameters based on the measured optical constants and coating thickness of the resist. This parameter modification compensates for resist property variations between test and production wafers, ensuring accurate pattern shape formation while maintaining high exposure throughput.
Solution Approach 2:
The system performs preliminary measurement of resist properties and calculates optimal exposure parameters before production exposure. This advance preparation ensures that the correct exposure settings are ready when production wafers are processed, preventing pattern deformation while maintaining productivity.
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 enables the formation of high-quality, fine patterns by accurately determining and adjusting exposure parameters, overcoming the limitations of conventional methods and ensuring consistent pattern shapes across wafers.
Implementation Method 1
measuring and controlling the optical constants and coating thickness of both test and production wafers using spectroscopic ellipsometry
Implementation Method 2
a projection exposure apparatus that projects and transfers a circuit pattern, which is formed on a reticle (or a mask), onto a wafer, etc. through a projection optical system
Data Source
AI summary
There is provided an exposure method for exposing a pattern on an original form onto an object through a projection optical system. The exposure method includes the steps of obtaining, for each piece of information of resist applied to a first object, a correlation among an exposure dose for exposing the first object, a focus state of the first object in the projection optical system, and a pattern shape formed on the first object exposed with the exposure dose and the focus state, acquiring information of resist applied to a second object different from the first object, determining an exposure dose for exposing the second object, and a focus state of the second object in the projection optical system, based on the correlation obtained by the obtaining step and the information of the resist applied to the second object acquired by the acquiring step, and transferring the pattern formed on the original form onto the second object in accordance with the exposure dose and focus state determined by the determining step.