Bottom-Up Molybdenum Gapfill for Void-Free High-Aspect Features
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Solution Overview
Problem
Conventional deposition methods struggle to defect-free fill narrow and deep substrate features due to excessive material deposition on the substrate surface, requiring additional etching steps that lower throughput and introduce defects like seams.
Innovation Solution
A cyclic deposition-etch process using molybdenum precursors and halides to form and remove gapfill within substrate features, primarily focusing on the bottom surface to achieve defect-free filling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional chemical vapor deposition methods are used to fill substrate features, then material is deposited on the substrate surface, but excessive material accumulates on the surface rather than within the features
Solution Approach 1:
The patent employs a cyclic deposition-etch process where deposition and etching steps are repeated alternately. During deposition, molybdenum material is deposited preferentially at the bottom of features; during etching, material on the substrate surface is removed. This periodic alternation enables precise gapfill within features while controlling surface material accumulation.
Solution Approach 2:
The deposition process exhibits spatially selective material deposition, with preferential deposition at the bottom of substrate features compared to the substrate surface. This local quality difference allows material to accumulate where needed (in features) while minimizing unwanted surface deposition, resolving the contradiction between gapfill precision and material quantity control.
2Manufacturing precision
If conventional deposition methods are used, then gapfill can be formed, but additional etching steps are required to remove surface material
Solution Approach 1:
The patent merges the gapfill deposition process with selective surface removal by integrating etching steps within the deposition cycle. The cyclic deposition-etch process combines material deposition and surface cleaning in a unified workflow, eliminating the need for separate post-deposition etching steps and improving throughput while maintaining gapfill precision.
Solution Approach 2:
The cyclic process maintains continuous productive action by alternating between deposition (building gapfill) and etching (removing surface material). This continuous alternation prevents idle time between separate deposition and etching operations, maximizing equipment utilization and throughput while achieving precise gapfill formation.
3Manufacturing precision
If atomic layer deposition is used for gapfill, then conformal films are formed on all surfaces, but seams appear where films meet in the middle
Solution Approach 1:
Instead of forming gapfill from the top down (as in conventional ALD where films deposit conformally on all surfaces), the patent inverts the approach by using cyclic deposition-etch to build material preferentially from the bottom up. This inversion prevents the formation of seams in the middle of features, as material is deposited and removed in cycles that favor bottom accumulation, thereby improving reliability by eliminating defect formation.
4Manufacturing precision
If material is deposited on the substrate surface during gapfill, then throughput decreases, but the cost of manufacture increases
Solution Approach 1:
The cyclic deposition-etch process selectively discards material deposited on the substrate surface during etching steps while retaining and accumulating material within substrate features during deposition steps. This selective discarding recovers the useful gapfill material while removing wasteful surface deposition, reducing manufacturing costs by minimizing material waste and process rework.
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 enables efficient, defect-free filling of high aspect ratio features without pinching off openings, reducing manufacturing costs by eliminating unnecessary etching steps and seam formation.
Implementation Method 1
Conventional deposition methods, especially chemical vapor deposition methods, deposit more material on the substrate surface than within the feature
Implementation Method 2
The substrate surface is exposed to a second molybdenum halide precursor to remove a portion of the first gapfill
Data Source
AI summary
Embodiments of the disclosure relate to methods for molybdenum gapfill. Additional embodiments provide a method of forming a molybdenum gapfill without substantial voids. Some embodiments of the disclosure are relevant for higher aspect ratio features including DRAM memory cells.