Tungsten Nucleation Layer Deposition for High Aspect Ratio Plug Fill
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional tungsten deposition methods, such as CVD, face limitations in producing low resistivity tungsten films with good step coverage for small features with high aspect ratios, particularly in forming conformal nucleation layers that support high-quality bulk deposition.
Innovation Solution
A combined pulsed nucleation layer (PNL) and chemical vapor deposition (CVD) process is used to form a tungsten nucleation layer, involving sequential pulses of reducing agents and tungsten precursors, followed by simultaneous exposure to these agents in CVD, without the use of borane, to achieve low resistivity and conformality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional CVD method is used to deposit tungsten nucleation layer, then deposition speed is improved, but film uniformity and conformality deteriorate
Solution Approach 1:
The nucleation layer deposition process is segmented into multiple sequential pulses of reducing agent and tungsten precursor, rather than using continuous CVD. This pulsed approach allows better control over film formation, improving conformality and uniformity while maintaining reasonable deposition speed.
Solution Approach 2:
The invention employs periodic pulsing of reducing agent and tungsten precursor gases into the reaction chamber. This periodic action enables precise control of the deposition process, allowing the formation of highly conformal nucleation layers that follow complex substrate topographies uniformly.
2Productivity
If conventional CVD method is used for tungsten deposition, then deposition speed is improved, but step coverage in high aspect ratio features deteriorates
Solution Approach 1:
The deposition process is divided into sequential pulses that allow the reducing agent to penetrate into high aspect ratio features before tungsten precursor is introduced. This segmentation ensures excellent step coverage by enabling reducing agents to reach deep into narrow features uniformly.
Solution Approach 2:
The reducing agent is pulsed into the reaction chamber first, before the tungsten precursor. This preliminary action ensures that reducing agents are already present and distributed uniformly in high aspect ratio features when the tungsten precursor arrives, enabling complete and uniform tungsten deposition throughout the feature depth.
3Length of moving object
If thinner tungsten films are deposited to meet scaling requirements, then device size is reduced, but electrical resistance increases
Solution Approach 1:
The invention changes the deposition parameters by using pulsed sequences with specific timing, temperatures, and gas flow rates that promote low-resistivity tungsten phase formation. These parameter changes enable the deposition of thin films with unusually low electrical resistance, breaking the typical thickness-resistance relationship.
Solution Approach 2:
The pulsed deposition process promotes specific phase transitions in tungsten during growth, favoring the formation of low-resistivity crystalline phases even in thin films. The controlled pulsing allows atoms to arrange into favorable crystal structures that minimize electrical resistance.
4Manufacturing precision
If sequential pulsed method is used to improve conformality, then deposition time increases
Solution Approach 1:
The pulsed deposition process is designed with minimal idle time between pulses, maintaining continuous useful action. The reducing agent and tungsten precursor pulses are tightly coupled with short or zero purge times, ensuring that the deposition process remains efficient while achieving superior conformality.
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 results in tungsten films with improved resistivity and uniformity, achieving low resistivity and good conformality, which is not achievable with CVD or PNL processes alone, and allows for the deposition of tungsten in high aspect ratio features with reduced roughness.
Implementation Method 1
the bulk layer is formed by the reduction of tungsten hexafluoride (WF6) with hydrogen (H2) on the growing tungsten layer
Implementation Method 2
In a CVD technique, the WF6 and reducing gas (e.g., SiH4 and/or H2) are simultaneously introduced into the reaction chamber. This produces a continuous chemical reaction of mixed reactant gases that continuously forms tungsten film on the substrate surface
Data Source
AI summary
The methods described herein relate to deposition of low resistivity, highly conformal tungsten nucleation layers. These layers serve as a seed layers for the deposition of a tungsten bulk layer. The methods are particularly useful for tungsten plug fill in which tungsten is deposited in high aspect ratio features. The methods involve depositing a nucleation layer by a combined PNL and CVD process. The substrate is first exposed to one or more cycles of sequential pulses of a reducing agent and a tungsten precursor in a PNL process. The nucleation layer is then completed by simultaneous exposure of the substrate to a reducing agent and tungsten precursor in a chemical vapor deposition process. In certain embodiments, the process is performed without the use of a borane as a reducing agent.