Halftone Phase Shift Film Sputtering Uniformity
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Solution Overview
Problem
Current methods for depositing halftone phase shift films face challenges in achieving stable and uniform optical properties, particularly in the transition mode of reactive sputtering, leading to variations in phase shift and transmittance, which affect the verticality of the cross-sectional shape of the pattern formed in halftone phase shift masks.
Innovation Solution
A method involving the use of a sputtering gas containing a rare gas and a nitrogen-containing gas, with multiple silicon targets and different power applications, and substrate rotation to achieve a halftone phase shift film with constant or continuously graded composition, ensuring high in-plane uniformity of optical properties and full verticality in the pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If reactive sputtering is used to deposit halftone phase shift film, then the film can be formed with desired composition, but the optical properties (phase shift and transmittance) show in-plane variations affecting pattern verticality
Solution Approach 1:
The patent divides the sputtering process into multiple sequential steps with different gas flow rates and power conditions. The deposition is segmented into stages: initial deposition with low nitrogen flow rate, intermediate deposition with increased nitrogen flow rate, and final deposition with adjusted parameters. This segmentation allows control over film composition and optical properties at different locations, reducing in-plane variations and improving both optical property uniformity and pattern verticality.
Solution Approach 2:
The patent dynamically adjusts sputtering parameters during the deposition process. The nitrogen gas flow rate and applied power are changed at different stages of film formation. This dynamic parameter adjustment enables real-time control of film composition and optical properties, ensuring uniformity across the film plane while maintaining reliable pattern verticality after etching.
2Ease of manufacture
If single silicon target is used for sputtering, then the process is simple, but the film shows poor in-plane uniformity of optical properties
Solution Approach 1:
Instead of using a single silicon target, the patent employs multiple silicon targets (at least two) arranged in a specific configuration. Each target contributes to different regions of the film deposition. The segmented target arrangement, combined with substrate rotation, ensures more uniform material distribution and optical properties across the film plane while maintaining a relatively simple overall process.
Solution Approach 2:
The patent incorporates substrate rotation during the sputtering process. The periodic rotation of the substrate ensures that all regions of the film receive equivalent exposure to sputtered material from the stationary multiple silicon targets. This periodic action compensates for the fixed target positions and achieves excellent in-plane uniformity of optical properties.
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
The approach results in a halftone phase shift mask with consistent phase shift and transmittance properties, enhancing the in-plane uniformity and verticality of the pattern, suitable for advanced photolithography processes using ArF excimer laser.
Implementation Method 1
depositing the phase shift film using a sputtering gas containing an inert gas and nitrogen-containing gas
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A halftone phase shift mask blank comprising a transparent substrate and a halftone phase shift film thereon is prepared through the step of depositing the halftone phase shift film on the substrate (S) by using a sputtering gas containing rare gas and nitrogen gas, and plural targets (T) including two or more silicon targets in a particular arrangement, applying powers of different values to the silicon targets (T), effecting reactive sputtering in the transition mode, and rotating the substrate on its axis in a horizontal direction. The plural targets are arranged so that, considering the target closest (horizontally) to the substrate rotation axis, the horizontal distance between the rotation axis and another target is 1 to 3 times that closest distance, also the maximum included angle in a horizontal plane between lines extending from the rotation axis to the various targets has a maximum value of 70° to 180°.