Substrate Resist Stripping Using Ozone Pretreatment and Wet Cleaning
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Solution Overview
Problem
The existing methods for removing hardened layers from substrates, such as semiconductor wafers, require lengthy high-temperature SPM processes, leading to increased sulfuric acid consumption and reduced productivity due to prolonged processing times, and pose environmental concerns.
Innovation Solution
A substrate processing method involving a heating step to 150°C or more, followed by ozone gas supply to generate oxygen radicals for removing the hardened layer, and subsequent wet processing with sulfuric acid to efficiently lift off the resist, reducing processing time and sulfuric acid usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a high-temperature SPM process is performed for a long time to remove the hardened layer, then the hardened layer can be removed, but the processing time increases and sulfuric acid consumption increases
Solution Approach 1:
The resist removal process is divided into two distinct stages: first, an ozone treatment step that selectively attacks and removes the hardened carbonized layer, and second, a wet SPM process that removes the remaining non-hardened resist. This segmentation allows each step to be optimized independently, with the ozone step targeting only the hardened portion and the SPM step handling the rest, thereby reducing overall processing time and chemical consumption while maintaining complete removal effectiveness.
Solution Approach 2:
The ozone treatment is performed as a preliminary step before the main SPM process. By pre-treating the substrate with ozone to remove the hardened layer first, the subsequent SPM process only needs to handle the softer non-hardened resist, which significantly reduces the required SPM processing time and sulfuric acid consumption while ensuring complete resist removal.
2Manufacturing precision
If a high-temperature SPM process is performed for a long time to remove the hardened layer, then the hardened layer can be removed, but the sulfuric acid consumption increases
Solution Approach 1:
The resist removal process is divided into two distinct stages: first, an ozone treatment step that selectively attacks and removes the hardened carbonized layer, and second, a wet SPM process that removes the remaining non-hardened resist. This segmentation allows each step to be optimized independently, with the ozone step targeting only the hardened portion and the SPM step handling the rest, thereby reducing overall processing time and chemical consumption while maintaining complete removal effectiveness.
Solution Approach 2:
The ozone treatment is performed as a preliminary step before the main SPM process. By pre-treating the substrate with ozone to remove the hardened layer first, the subsequent SPM process only needs to handle the softer non-hardened resist, which significantly reduces the required SPM processing time and sulfuric acid consumption while ensuring complete resist removal.
3Productivity
If ozone gas is supplied to heated substrate to generate oxygen radicals, then the hardened layer can be removed quickly, but additional process steps are required
Solution Approach 1:
The invention utilizes a parameter change approach by transforming the chemical state of oxygen through thermal decomposition. Ozone gas (O3) is supplied to the heated substrate (at least 150°C), where it decomposes into oxygen radicals that selectively attack and remove the hardened carbonized resist layer. This parameter-based approach (temperature + ozone concentration) enables rapid hardened layer removal while keeping the process relatively simple.
Solution Approach 2:
The invention converts a potentially harmful process into a beneficial one by using thermal decomposition of ozone. The high temperature required for the SPM process, which could cause damage, is instead utilized to decompose ozone into reactive oxygen radicals that selectively remove only the hardened carbonized layer without damaging the underlying substrate or device structures. This turns the high temperature from a potential harm into a useful mechanism for selective removal.
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 allows for rapid removal of hardened layers with reduced sulfuric acid consumption, enhancing productivity and minimizing environmental impact by shortening processing time and sulfuric acid usage.
Implementation Method 1
The ozone gas receives heat from the front surface of the substrate and is thermally decomposed, and, as a result, an oxygen radical is generated
Data Source
AI summary
A substrate processing method is provided for removing a resist having a hardened layer from a front surface of a substrate. The substrate processing method includes a hardened-layer removing step and a wet processing step. The hardened-layer removing step includes a heating step of heating the substrate to 150° C. or more and an ozone-gas supplying step of supplying an ozone gas to the front surface of the substrate being heated by the heating step, and the hardened-layer removing step removes the hardened layer by generating an oxygen radical near the front surface of the substrate. The wet processing step removes the resist from the front surface of the substrate by supplying a processing liquid including a sulfuric acid to the front surface of the substrate after the hardened-layer removing step.