Phase-Shift Blank Mask Thermal Stability for Fine Patterns
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Solution Overview
Problem
The miniaturization of semiconductor device circuit patterns is hindered by light diffraction issues in binary masks and the need for precise control of phase shift masks to achieve refined patterns, particularly due to thermal variations affecting the phase shift and light shielding films during exposure processes.
Innovation Solution
A blank mask design with a transparent substrate, phase shift film, and light shielding film, where thermal variation values (TFT1 and TFT2) are controlled through magnetic field adjustment during sputtering to minimize thermal expansion and maintain precise phase difference and transmittance, enhancing resolution and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a binary mask is used for pattern formation, then the structure is simple and manufacturing is easier, but light diffraction at the edge of the transmissive portion causes problems in developing minute patterns
Solution Approach 1:
The patent employs a composite mask structure combining a transmissive region with a phase shift film in the reflective region. This composite design integrates materials with different optical properties (transmissive and reflective phases) to simultaneously achieve simple manufacturing processes and high pattern resolution by eliminating diffraction effects through phase modulation.
Solution Approach 2:
The patent changes the optical parameter of the mask by introducing a phase shift film that modulates the phase of reflected light. This parameter change from purely transmissive to phase-modulated reflective transmission resolves the diffraction problem while maintaining manufacturing feasibility through established sputtering techniques.
2Manufacturing precision
If a phase shift mask is used to form refined patterns, then pattern resolution is improved, but thermal variations during exposure affect the phase shift and light shielding films
Solution Approach 1:
The patent applies different thermal compensation strategies to different regions: the phase shift film in the reflective region is designed with specific thermal expansion characteristics to maintain phase stability, while the light shielding film in the pattern formation region is optimized for thermal stability. This local optimization resolves thermal variation issues while preserving high pattern resolution.
Solution Approach 2:
The patent converts the harmful thermal expansion effect into a beneficial control mechanism by carefully selecting film materials and thicknesses whose thermal expansion characteristics collectively compensate for each other, maintaining overall mask stability during exposure while enabling refined pattern formation.
3Strength
If the thickness of the transparent substrate is increased to improve durability, then mechanical strength is improved, but thermal expansion and position change of films increase
Solution Approach 1:
The patent optimizes the substrate thickness parameter to a specific range that balances mechanical strength and thermal expansion. By changing the thickness parameter and compensating with adjusted film thicknesses and material selections, the patent achieves both improved durability and maintained film position stability during thermal cycles.
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 controlled thermal variation values stabilize the phase shift and light shielding films, improving pattern resolution and durability under high-temperature exposure conditions, enabling more precise semiconductor circuit pattern formation.
Implementation Method 1
a phase shift film, and a light shielding film disposed on the phase shift film
Implementation Method 2
thermal variation values (TFT1 and TFT2) are controlled through magnetic field adjustment during sputtering
Implementation Method 3
thermal variation values (TFT1 and TFT2) are controlled through magnetic field adjustment during sputtering
Data Source
AI summary
The present disclosure relates to a blank mask and the like, and comprises a transparent substrate, a phase shift film disposed on the transparent substrate, and a light shielding film disposed on the phase shift film. The blank mask has a TFT1 value of 0.25 μm/100° C. or less expressed by Equation 1 below:TFT1=ΔPMT2-T1[Equation1]where, when the thermal variation of the processed blank mask, which is formed by processing the thickness of the transparent substrate of the blank mask to be 0.6 mm and removing the light shielding film, is analyzed in a thermomechanical analyzer, the measuring temperature of the thermomechanical analyzer is increased from T1 to T2, and ΔPM is a position change of the upper surface of the phase shift film in the thickness direction at T2, based on a position of the upper surface of the phase shift film at T1.