Silicon Oxide Recess Etch Uniformity via Plasma Conditioning
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Solution Overview
Problem
Existing silicon oxide dry etch processes lack uniformity in etch rates across varying patterns on substrates, leading to trench recess variations within and between trenches.
Innovation Solution
A method involving sequential exposure of gapfill silicon oxide to local plasma treatment followed by remote-plasma dry etch, producing salt by-products that are then sublimated, ensuring a more even etch rate across trenches and between them, while maintaining a rectilinear profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dry etch processes are used on silicon oxide, then etching can proceed, but uniformity of etch rate across varying patterns is poor leading to trench recess variations
Solution Approach 1:
A plasma treatment step is performed before the main etch process to prepare the silicon oxide surface. This preliminary plasma exposure modifies the surface properties uniformly across different trench patterns, ensuring consistent etch rates during the subsequent etching step and eliminating the need for pattern-specific process adjustments.
Solution Approach 2:
The process uses specific parameter combinations including plasma power, pressure, and gas flow rates that are optimized to achieve uniform etching across varying trench geometries. By carefully controlling these parameters, the etch rate becomes independent of trench width and pattern density, resolving the uniformity issue.
2Object-affected harmful factors
If remote plasma dry etch is used, then plasma damage is avoided, but salt by-products are produced on the surface requiring additional cleaning
Solution Approach 1:
The salt by-products formed during remote plasma etching are converted into a beneficial cleaning mechanism. The sublimation process that removes these salts also simultaneously cleans the trench walls and surfaces, turning a previously harmful residue into a useful self-cleaning feature that eliminates the need for separate cleaning steps.
Solution Approach 2:
The process utilizes the phase transition of salt by-products from solid to gas through sublimation. By controlling temperature and pressure conditions, the salts sublime and are removed from the surface, providing an effective cleaning mechanism that works in conjunction with the remote plasma etching process.
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 significantly reduces inter-trench and intra-trench variability in silicon oxide thickness, achieving unprecedented uniformity and avoiding material erosion on trench walls.
Implementation Method 1
The gapfill silicon oxide is exposed to a local plasma treatment prior to a remote-plasma dry etch
Implementation Method 2
combining a hydrogen-containing precursor and a fluorine-containing precursor in a remote plasma region while forming a remote plasma in the remote plasma region to form plasma effluents
Implementation Method 3
The salt by-product may be removed by raising the temperature in a subsequent sublimation step
Data Source
AI summary
A method of etching silicon oxide from a trench is described which allows more homogeneous etch rates across a varying pattern on a patterned substrate. The method also provides a more rectilinear profile following the etch process. Methods include a sequential exposure of gapfill silicon oxide. The gapfill silicon oxide is exposed to a local plasma treatment prior to a remote-plasma dry etch which may produce salt by-product on the surface. The local plasma treatment has been found to condition the gapfill silicon oxide such that the etch process proceeds at a more even rate within each trench and across multiple trenches. The salt by-product may be removed by raising the temperature in a subsequent sublimation step.