Amorphous Silicon Nucleation Layer for Tungsten ALD Conformality
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for depositing amorphous silicon films face challenges in achieving conformality and gap-fill performance in high aspect-ratio features, and atomic layer deposition of tungsten films exhibits poor nucleation and adhesion on silicon and silicon oxide substrates, leading to high resistivity and substrate damage.
Innovation Solution
The method involves forming an amorphous silicon layer as a glue layer or nucleation layer on a substrate, using a silicon precursor like disilane, and depositing a metal layer such as tungsten or molybdenum on top, with a thin titanium nitride glue layer to improve adhesion and conformality, while minimizing substrate damage and resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional LPCVD process is used to deposit amorphous silicon, then deposition can be performed at high temperature and low pressure, but step coverage and gap-fill performance are poor
Solution Approach 1:
The patent changes the deposition method from LPCVD to ALD, fundamentally altering the process parameters and mechanism. ALD operates at lower temperatures with self-limiting surface reactions, enabling conformal deposition in high aspect-ratio features while maintaining amorphous silicon phase
Solution Approach 2:
The patent replaces the thermal field-driven LPCVD process with a chemical field-driven ALD process using sequential precursor exposure. This substitution of the deposition mechanism enables precise control over film thickness and conformality that cannot be achieved with conventional thermal CVD
2Temperature
If PECVD process is used to deposit amorphous silicon, then deposition can be performed at lower temperature, but step coverage and gap-fill performance are poor
Solution Approach 1:
The patent changes from PECVD to ALD, altering the fundamental deposition mechanism from plasma-enhanced chemical vapor deposition to atomic layer deposition. This enables conformal coverage while maintaining low temperature processing through self-limiting surface reactions
Solution Approach 2:
The patent replaces the plasma field mechanism with a sequential chemical precursor exposure mechanism. This substitution eliminates the line-of-sight deposition limitation of PECVD and enables conformal gap-fill performance at low temperatures
3Reliability
If ALD WSix or WBx nucleation layer is deposited using WF6/Si2H6 or WF6/B2H6, then nucleation performance is improved, but substrate damage occurs due to direct exposure to WF6
Solution Approach 1:
The patent introduces an amorphous silicon layer as an intermediary between the substrate and the WF6 exposure. This intermediate layer protects the substrate from direct contact with the damaging WF6 precursor while still enabling effective nucleation of the subsequent metal layer
Solution Approach 2:
The patent performs preliminary deposition of an amorphous silicon layer before exposing the substrate to WF6. This preliminary action creates a protective barrier that prevents substrate damage in subsequent processing steps while maintaining the desired nucleation functionality
4Strength
If titanium nitride glue layer and WSix/WBx nucleation layer are used to improve adhesion, then adhesion is improved, but resistivity of the stack becomes very high
Solution Approach 1:
The patent extracts and removes the high-resistivity WSix/WBx nucleation layer from the stack, retaining only the essential TiN glue layer for adhesion. This elimination of the problematic intermediate layer reduces overall stack resistivity while maintaining adequate adhesion through the TiN layer alone
Solution Approach 2:
The patent optimizes the thickness of the TiN glue layer to provide sufficient adhesion locally without adding excessive resistivity. By controlling the TiN layer thickness in the range of 5-30 Å, the patent achieves the necessary mechanical bonding while minimizing electrical resistance
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 enhances the conformality and adhesion of metal films on silicon and silicon oxide substrates, improving the step coverage and gap-fill performance, and reducing the resistivity of the metal film stack.
Implementation Method 1
exposing a substrate surface to a silicon precursor to form an amorphous silicon layer
Implementation Method 2
A titanium nitride glue layer is used to improve the adhesion
Data Source
AI summary
Methods for depositing a metal film comprising forming an amorphous silicon layer as a nucleation layer and/or glue layer on a substrate. Some embodiments further comprise the incorporation of a glue layer to increase the ability of the amorphous silicon layer and metal layer to stick to the substrate.