Wet Clean Process for High Aspect Ratio STI Pattern Collapse
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Solution Overview
Problem
The fabrication of semiconductor devices with high aspect ratio trenches often results in pattern collapse during wet clean processes, leading to distortion, bending, and increased defects, which can cause leakage and short circuiting, particularly in advanced semiconductor manufacturing with dimensions below 50 nm.
Innovation Solution
A wet clean process involving dry etching with a fluorine-containing gas like C2F6, followed by cleaning with diluted hydrofluoric acid (HF) or an ammonia-HF solution, and subsequent vapor etching with HF vapor to form pattern collapse-free high aspect ratio shallow trench isolation (STI) features on a substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet strip processes are used to remove polymer residues, then cleaning effectiveness is improved, but pattern collapse and trench boundary distortion occur
Solution Approach 1:
The harmful polymer residues are selectively extracted and removed using oxygen plasma treatment, separating the cleaning function from the pattern structure to prevent collapse while maintaining effectiveness
Solution Approach 2:
The mechanical wet strip process is replaced with a chemical plasma-based cleaning method, substituting physical liquid immersion and rinsing with controlled plasma chemistry that eliminates capillary forces causing pattern collapse
2Productivity
If conventional cleaning methods are used, then polymer residue removal is effective, but yield decreases due to leakage and short circuiting
Solution Approach 1:
Oxygen plasma treatment is applied as a preliminary cleaning step before subsequent processing, proactively removing polymer residues and preventing potential leakage and short circuiting issues before they can occur in later device operation
Solution Approach 2:
The plasma process converts the potentially harmful strong cleaning action into a beneficial selective removal mechanism that targets only polymer residues while leaving the pattern structure intact, transforming a risk into a reliability improvement
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 process significantly reduces or eliminates pattern collapse in semiconductor devices, thereby increasing the yield by maintaining the integrity of high aspect ratio features and preventing defects such as leakage and short circuiting.
Implementation Method 1
dry etching the substrate to form multiple high aspect ratio shallow trench isolations (STI) on the substrate and to simultaneously remove the oxide layer from the substrate
Implementation Method 2
cleaning the substrate in a single wafer cleaner (SWC) with diluted hydrofluoric acid (HF) or in a solution of ammonia and HF to remove polymer residues left behind by the dry-etching step and the pad oxide layer from the substrate
Implementation Method 3
vapor etching the substrate with an HF vapor to form a substrate with multiple-pattern collapse-free high aspect ratio STI features
Data Source
AI summary
The disclosure provides a pattern collapse free wet clean process for fabricating semiconductor devices. By performing post reactive ion etching (RIE) using a fluorine-containing gas such as C2F6, followed by cleaning in a single wafer cleaner (SWC) with diluted hydrofluoric acid (HF) or in a solution of ammonia and HF, a substrate with multiple pattern collapse free high aspect ratio shallow trench isolation (STI) features can be obtained.