Phase-Shifting Photomask Thermal Oxidation Patterning
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Solution Overview
Problem
The process of forming phase-shifting photomasks is not stable, leading to difficulties in practical application due to misalignment and pattern accuracy issues.
Innovation Solution
A method involving a thermal oxidation process to form a hard-shielding layer and thermal oxide layer on a phase-shifting photomask, where the hard-shielding layer is used as a mask to expose and remove portions of the light shielding layer, maintaining pattern accuracy and avoiding misalignment by ensuring consistent width exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photomask formation processes are used, then manufacturing complexity is reduced, but manufacturing precision and pattern accuracy deteriorate
Solution Approach 1:
The photomask structure is divided into multiple layers: a first photomask layer with phase-shifting regions and light shielding regions, a second photomask layer with pattern regions, and intermediate thermal oxide layers. This segmentation allows each layer to be formed and patterned separately with high precision, then combined to achieve overall pattern accuracy while managing process complexity through systematic layer-by-layer fabrication.
Solution Approach 2:
Thermal oxide layers are formed on the substrate and photomask layers before final patterning operations. These preliminary oxide layers serve as protective and defining structures that enable subsequent precise pattern formation. The thermal oxidation process is performed in advance to establish reference surfaces and protective barriers that facilitate accurate pattern transfer in later steps.
2Measurement precision
If phase-shifting photomask processes are implemented, then exposure resolution is improved, but process stability deteriorates
Solution Approach 1:
The invention utilizes thermal oxidation parameters (temperature, time, atmosphere) to precisely control the formation of thermal oxide layers with specific thicknesses and properties. By carefully adjusting these oxidation parameters, the process achieves stable and reproducible results. The phase-shifting layer's optical parameters (thickness, material composition) are also optimized to provide consistent phase shifts, thereby improving exposure resolution while maintaining process stability through controlled parameter variations.
3Manufacturing precision
If thermal oxidation process is used to form hard-shielding layer, then manufacturing precision is improved, but use of energy increases
Solution Approach 1:
The thermal oxidation process is designed to proceed continuously without interruption, forming the thermal oxide layer uniformly across the entire substrate surface. This continuous action ensures consistent oxidation throughout the layer, improving pattern accuracy by eliminating variations that might arise from intermittent processing. The continuous thermal field maintains stable reaction conditions, reducing energy fluctuations and improving overall process efficiency despite the high energy requirements of thermal oxidation.
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 method improves the stability and accuracy of the phase-shifting photomask process, preventing misalignment and maintaining pattern accuracy, thus enhancing the resolution of exposure processes.
Implementation Method 1
A thermal oxidation process is performed on the second layer photomask pattern to form a thermal oxide layer and a hard-shielding layer pattern
Data Source
AI summary
The present disclosure provides a method of manufacturing a phase-shifting photomask, which includes following steps. A mask pattern provides on a transparent substrate and includes a first layer photomask pattern including a phase-shifting layer and a light shielding layer sequentially stacked on the transparent substrate and a second layer photomask pattern stacked on the transparent substrate in sequence. A thermal oxidation process is performed on the second layer photomask pattern to form a thermal oxide layer and a hard-shielding layer pattern exposed a portion of a top surface of the light shielding layer, and the thermal oxide layer covers the hard-shielding layer pattern and the portion of the top surface of the light shielding layer. The thermal oxide layer is removed. A portion of the light shielding layer is removed by using the hard-shielding layer pattern as a mask to form a patterned light shielding layer exposed the phase-shifting layer.