Photolithography Focus and Dose Correction via Dual Test Patterns
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Solution Overview
Problem
Photolithography machines face challenges in accurately adjusting focus and dose settings, especially at low critical dimensions, leading to uncertainty in pattern edge slope and width, which complicates the transfer of patterns to resin layers, particularly on complex layers like transistor gates or Shallow Trench Isolation layers.
Innovation Solution
A method involving the use of two test patterns on a photolithography mask with different optical paths, allowing for the measurement of critical dimensions to determine focus and dose correction values using specific equations, thereby simplifying the adjustment of focus and dose settings without adding manufacturing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single test pattern is used to measure critical dimension, then the measurement process is simple, but the focus setting determination is ambiguous due to two possible focus values
Solution Approach 1:
The single test pattern is segmented into two separate test patterns with different optical path lengths. This segmentation allows each pattern to be sensitive to different focus conditions, enabling unambiguous determination of the focus setting by comparing the critical dimension measurements from both patterns.
2Manufacturing precision
If focus setting is made more sensitive to achieve lower critical dimension, then the resolution is improved, but the pattern edge slope becomes uncertain
Solution Approach 1:
The two test patterns act as intermediaries that translate the focus setting into measurable critical dimension differences. By comparing the critical dimensions of these two patterns, the focus setting can be determined accurately without directly measuring the uncertain pattern edge slope of the actual circuit patterns.
3Manufacturing precision
If dose setting is adjusted to improve pattern width accuracy, then the pattern transfer accuracy is improved, but the measurement process becomes more complex
Solution Approach 1:
The determination of both focus and dose settings is merged into a single measurement process using the two test patterns. By simultaneously measuring the critical dimensions of both patterns and comparing them, both focus and dose errors can be determined together through the provided equations, avoiding separate complex measurement procedures.
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 method enables precise adjustment of focus and dose settings for photolithography machines, improving pattern accuracy and reducing uncertainty, even on complex layers, by using equations to calculate correction values from measured critical dimensions.
Implementation Method 1
Photolithography is currently used in microelectronics to transfer patterns present on a mask to a resin layer deposited on a substrate. To that end, a photolithography exposure machine is used, configured to project a photon beam focused on the resin layer through the mask.
Data Source
AI summary
In one or more embodiments, the disclosure relates to a method of setting a photolithography exposure machine, comprising: forming on a photolithography mask test patterns and circuit patterns, transferring the patterns to a resin layer covering a wafer, measuring a critical dimension of each test pattern transferred, and determining a focus setting error value of the photolithography machine from the measure of the critical dimension of each pattern, the test patterns formed on the mask comprising a first reference test pattern and a second test pattern forming for a photon beam emitted by the photolithography machine and going through the mask, an optical path having a length different from an optical path formed by the first test pattern and the circuit patterns formed on the mask.