Polysilicon Hardmask Removal for Precise Multi-Layer Substrate Patterning
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Solution Overview
Problem
The semiconductor industry faces challenges in creating fine patterns on substrates with desirable profiles using traditional lithographic techniques, particularly due to the limitations of hardmask layers in providing chemical, thermal, and etching resistance during various etching processes.
Innovation Solution
A substrate processing method involving the formation of a polysilicon hardmask on an insulative layer, followed by etching and deposition of metal and passivation films, with specific removal processes using gas mixtures like BCl3, Cl, CF4, and HBr to form channels and remove the hardmask in situ, reducing contamination and processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional lithographic technique with hardmask is used, then pattern transfer capability is improved, but processing time increases and contamination risk increases due to multiple removal steps
Solution Approach 1:
The patent segments the hardmask removal process into three distinct etching steps with different gas chemistries: first step removes organic contaminants using oxygen plasma, second step removes polysilicon hardmask using BCl3/Cl2 plasma, and third step removes remaining residues using CF4/O2 plasma. This segmentation allows each step to be optimized for its specific function, improving overall efficiency while maintaining pattern transfer quality.
Solution Approach 2:
The patent implements continuous in-situ processing where the hardmask removal steps are performed sequentially without breaking vacuum or exposing the substrate to ambient conditions. The substrate remains in the processing chamber throughout all removal steps, eliminating transfer time and reducing contamination risk while maintaining continuous productive action.
2Manufacturing precision
If traditional lithographic technique with hardmask is used, then pattern transfer capability is improved, but contamination increases due to multiple removal steps
Solution Approach 1:
The patent maintains an inert vacuum environment throughout the entire hardmask removal process. All three etching steps are performed in-situ within the vacuum chamber, preventing exposure to ambient contaminants. The use of controlled plasma chemistry in each step further ensures a clean environment that prevents contamination while achieving complete hardmask removal.
Solution Approach 2:
The patent replaces mechanical removal methods (such as CMP or lift-off) with plasma-based chemical etching processes. This substitution allows for more precise control over the removal process, reduces mechanical stress on the substrate, and minimizes particle generation and contamination while maintaining pattern fidelity.
3Reliability
If hardmask layer is used during etching, then etching resistance is improved, but chemical resistance requirements increase the complexity of removal processes
Solution Approach 1:
The patent changes the chemical parameters of the etching environment across three sequential steps to selectively remove the hardmask while preserving the underlying structure. Step 1 uses oxygen plasma for organic removal, step 2 uses BCl3/Cl2 plasma for polysilicon etching, and step 3 uses CF4/O2 plasma for residue removal. Each parameter change is tailored to the specific material being removed, simplifying the overall process compared to using a single aggressive chemistry.
Solution Approach 2:
The patent introduces intermediate processing steps with specific gas chemistries that act as mediators between the hardmask formation and final pattern transfer. The oxygen plasma step serves as an intermediary to remove organics before the main hardmask removal, and the CF4/O2 step acts as an intermediary to clean residues after the main etching, making the overall process more controlled and less complex than direct aggressive 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 method enables the precise patterning of substrates with multiple layers, improving the hardmask's durability and allowing for in situ removal, thus enhancing pattern quality and reducing processing time while minimizing contamination.
Implementation Method 1
etching the insulative layer and the sacrificial layer exposed through a plurality of openings of the polysilicon hardmask
Implementation Method 2
depositing a metal film on the polysilicon hardmask and in the channels
Implementation Method 3
depositing a passivation film on the metal film
Implementation Method 4
The first removal process uses a process gas that comprises a mixture of boron trichloride (BCl3), chlorine (Cl) and carbon tetrafluoride (CF4)
Implementation Method 5
The second removal process uses boron trichloride (BCl3) and chlorine (Cl) as reaction gases
Implementation Method 6
The third removal process uses chlorine (Cl), oxygen (O2) and carbon tetrafluoride (CF4) as reaction gases
Data Source
AI summary
The present application provides a method for process a substrate. The method includes steps of providing a substrate having a sacrificial layer and an insulative layer, forming a polysilicon hardmask on the insulative layer, etching the insulative and sacrificial layers through multiple openings in the polysilicon hardmask to thus form multiple channels, depositing a metal film and a passivation film on the polysilicon hardmask and in the channels, performing a first removal process to remove portions of the passivation film and the metal film above the polysilicon hardmask, performing a second removal process to remove portions of the polysilicon hardmask exposed through the passivation film and the metal film, and performing a third removal process to remove the polysilicon hardmask and portions of the passivation film and the metal film surrounding the polysilicon is hardmask.