Low Temperature Tungsten CVD for Void-Free High Aspect Ratio Fill
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional chemical vapor deposition (CVD) techniques face challenges in filling high aspect ratio features in semiconductor devices, leading to voids and increased resistance, especially as devices scale to sub-32 nm technology nodes, due to issues with step coverage and fluorine migration.
Innovation Solution
A reduced temperature CVD process is employed, maintaining temperatures below 350°C, combined with a low resistivity treatment and high temperature CVD, to achieve void-free tungsten fill and improved barrier properties, allowing for effective filling of high aspect ratio features and maintaining low resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CVD techniques are used to deposit tungsten films, then the process can achieve standard deposition rates, but voids and large seams form within high aspect ratio device features
Solution Approach 1:
The patent changes the deposition temperature parameter from conventional high temperatures to reduced temperatures (below 350°C). This parameter change modifies the deposition kinetics and step coverage characteristics, enabling void-free fill in high aspect ratio features while maintaining acceptable deposition rates and film quality.
Solution Approach 2:
The patent employs a dynamic, multi-stage deposition process that adjusts process conditions during deposition. The process includes a nucleation stage, a fill stage with reduced temperature, and optional subsequent stages, allowing the system to adapt to the specific requirements of high aspect ratio features at different deposition phases.
2Productivity
If the wafer is heated to conventional process temperatures, then standard CVD deposition can proceed, but fluorine migration occurs into underlying layers
Solution Approach 1:
The patent reduces the deposition temperature parameter to below 350°C, which simultaneously achieves two benefits: (1) suppresses fluorine migration into underlying layers by reducing thermal energy available for diffusion, and (2) maintains acceptable deposition rates through optimized process conditions and chemistry.
Solution Approach 2:
The patent introduces a tungsten nucleation layer as an intermediary barrier between the CVD tungsten deposit and the underlying layers. This nucleation layer, deposited at reduced temperature, provides improved barriers to fluorine migration while enabling subsequent bulk tungsten deposition.
3Ease of manufacture
If high aspect ratio features are filled using conventional CVD, then standard process conditions are maintained, but step coverage becomes insufficient
Solution Approach 1:
The patent modifies the temperature parameter to reduced conditions (below 350°C) which fundamentally changes the deposition mechanism and step coverage characteristics. This enables conformal coating on complex high aspect ratio geometries that cannot be achieved with conventional high temperature processes.
Solution Approach 2:
The patent divides the deposition process into distinct segments: a nucleation layer deposition stage, a reduced temperature fill stage, and optional subsequent stages. Each segment is optimized for specific requirements, with the reduced temperature fill stage specifically addressing step coverage challenges in high aspect ratio features.
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 results in improved step coverage, reduced fluorine attack, and comparable resistivity to standard CVD processes, enabling reliable and efficient tungsten deposition in advanced semiconductor nodes.
Implementation Method 1
the deposition of tungsten films using chemical vapor deposition (CVD) techniques
Implementation Method 2
the tungsten bulk layer is formed by the reduction of tungsten hexafluoride (WF6) with hydrogen (H2) on the growing tungsten layer
Data Source
AI summary
Provided are methods of void-free tungsten fill of high aspect ratio features. According to various embodiments, the methods involve a reduced temperature chemical vapor deposition (CVD) process to fill the features with tungsten. In certain embodiments, the process temperature is maintained at less than about 350° C. during the chemical vapor deposition to fill the feature. The reduced-temperature CVD tungsten fill provides improved tungsten fill in high aspect ratio features, provides improved barriers to fluorine migration into underlying layers, while achieving similar thin film resistivity as standard CVD fill. Also provided are methods of depositing thin tungsten films having low-resistivity. According to various embodiments, the methods involve performing a reduced temperature low resistivity treatment on a deposited nucleation layer prior to depositing a tungsten bulk layer and/or depositing a bulk layer via a reduced temperature CVD process followed by a high temperature CVD process.