Metal Fill Nucleation Layers for Line Bending Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenges in semiconductor fabrication include reducing fluorine incorporation, resistance, stress, and line bending during metal fill processes, particularly in features with complex geometries and shrinking dimensions, which affect device performance and yield.
Innovation Solution
A method involving multiple conformal nucleation layers with controlled deposition conditions, including varying reducing agent chemistry, flow sequences, and chamber parameters, is used to mitigate line bending and reduce fluorine incorporation, while ensuring low resistivity and stress in the deposited metal films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single conformal metal nucleation layer is deposited to fill features, then the feature fill is simplified, but line bending occurs due to interatomic forces pulling features together
Solution Approach 1:
The single nucleation layer is segmented into multiple nucleation layers (first nucleation layer and second nucleation layer) with different deposition conditions. The first nucleation layer is deposited at conditions promoting roughness to prevent line bending, while the second nucleation layer is deposited at conditions optimizing for low resistivity and smooth morphology, thereby resolving the contradiction between preventing line bending and maintaining electrical performance.
Solution Approach 2:
Different regions of the nucleation structure are given different properties: the first nucleation layer has increased roughness specifically at the feature bottom where line bending occurs, while the second nucleation layer provides a smooth, low-resistivity interface for the bulk metal layer. This local differentiation allows each layer to perform its specific function without compromising the other.
2Reliability
If deposition conditions are optimized for low resistivity, then electrical performance improves, but line bending increases due to smoother surfaces allowing stronger interatomic forces
Solution Approach 1:
The nucleation layer deposition process is segmented into two distinct stages with different optimization goals. The first stage optimizes for roughness to prevent line bending, while the second stage optimizes for low resistivity. This segmentation allows each stage to achieve its primary objective without compromising the other, as the roughness-function is established in the first layer and the low-resistivity property is established in the second layer.
Solution Approach 2:
The first nucleation layer performs the preliminary action of preventing line bending by creating a rough surface morphology before the second nucleation layer is deposited. This preliminary roughness structure is then preserved while the second layer adds the low-resistivity property, ensuring that the line bending prevention function is established before the resistivity optimization begins.
3Manufacturing precision
If multiple nucleation layers are deposited to prevent line bending, then manufacturing complexity increases, but process time and simplicity are reduced
Solution Approach 1:
The two-nucleation-layer structure serves multiple functions simultaneously: the first nucleation layer prevents line bending through roughness, the second nucleation layer provides low resistivity, and together they create a stable interface for bulk metal deposition. This multi-functionality justifies the increased structural complexity by delivering multiple critical performance benefits in a single integrated approach.
Solution Approach 2:
The deposition parameters are changed between the two nucleation layers to achieve different outcomes. The first layer uses parameters optimized for roughness (such as lower temperature, different precursor flow rates), while the second layer uses parameters optimized for smooth, low-resistivity film (such as higher temperature, different flow sequences). These parameter changes enable the dual-function nucleation structure without requiring fundamentally different deposition techniques.
4Productivity
If fluorine-containing precursors are used for metal deposition, then deposition rate improves, but fluorine incorporation increases causing harmful effects
Solution Approach 1:
The nucleation layers serve as an intermediary between the fluorine-containing bulk metal deposition and the underlying substrate. By depositing the bulk metal layer over the two-nucleation-layer structure, the fluorine incorporation is controlled and managed through the nucleation layers, which act as a buffer that reduces harmful fluorine effects while maintaining the benefits of high-rate fluorine-containing precursor deposition.
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 effectively reduces line bending, fluorine incorporation, and resistivity, improving the uniformity and yield of metal-filled features, particularly in DRAM buried wordlines and other complex structures.
Implementation Method 1
depositing a first conformal metal nucleation layer in the plurality of features under supersaturated conditions by exposing the feature to alternating doses of a reducing agent and a metal precursor
Implementation Method 2
exposing the feature to alternating doses of a reducing agent and a metal precursor
Data Source
AI summary
Methods of mitigating line bending during feature fill include deposition of a nucleation layer having increased roughness. In some embodiments, the methods include depositing two or more metal nucleation layers.