VHF RF Sputtering for High Aspect Ratio Metal Coverage
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Solution Overview
Problem
Conventional DC sputtering methods fail to provide adequate coverage of the bottom surface in high aspect ratio features, leading to void formation and increased costs due to long deposition times and elevated substrate temperatures.
Innovation Solution
A method involving RF power at VHF frequency to form a plasma, combined with DC power to direct the plasma and maintain sufficient chamber pressure for ionization, along with additional RF power to redistribute metal atoms, ensures continuous metal layer deposition on all surfaces of high aspect ratio features without exposing the substrate to high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional DC sputtering is used to deposit metal in high aspect ratio features, then the deposition process can be performed, but adequate coverage of the bottom surface cannot be achieved
Solution Approach 1:
The patent changes the sputtering parameters by applying RF power at VHF frequency (e.g., 60 MHz) instead of conventional DC power, and maintains elevated chamber pressure (e.g., 10-100 mTorr) to increase ionization of metal atoms. These parameter changes enable adequate bottom surface coverage in high aspect ratio features while maintaining continuous layer formation.
2Manufacturing precision
If DC PVD process conditions are modified to achieve acceptable bottom surface coverage, then coverage can be improved, but deposition time increases and substrate temperature rises
Solution Approach 1:
The patent uses RF power at VHF frequency combined with elevated chamber pressure to increase ionization of metal atoms. This enables adequate bottom surface coverage while maintaining reasonable deposition times and preventing excessive substrate temperature rise, thus resolving the contradiction between coverage quality and productivity.
3Manufacturing precision
If DC PVD process conditions are modified to achieve acceptable bottom surface coverage, then coverage can be improved, but substrate temperature increases causing undesirable diffusion
Solution Approach 1:
The patent employs RF power at VHF frequency with elevated chamber pressure to enhance ionization of metal atoms during sputtering. This approach achieves adequate bottom surface coverage while maintaining substrate temperature at levels that prevent undesirable material diffusion, thus resolving the contradiction between coverage quality and temperature control.
4Reliability
If conventional sputtering is used, then the process can be performed, but ionization of metal atoms is insufficient leading to poor coverage
Solution Approach 1:
The patent maintains elevated chamber pressure (e.g., 10-100 mTorr) during RF sputtering at VHF frequency. This increased pressure enhances the ionization of metal atoms in the plasma, ensuring adequate bottom surface coverage and formation of continuous metal layers 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 achieves continuous metal coverage in high aspect ratio features while maintaining high throughput and low substrate temperature, preventing void formation and reducing costs associated with extended processing times and thermal exposure.
Implementation Method 1
applying a first RF power at a VHF frequency to a target comprising a metal disposed above the substrate to form a plasma from a plasma-forming gas
Implementation Method 2
sputtering metal atoms from the target using the plasma
Implementation Method 3
maintaining a first pressure in the PVD chamber sufficient to ionize a predominant portion of the metal atoms sputtered from the target
Implementation Method 4
applying a second RF power to a first electrode disposed beneath the substrate to redistribute at least some of the first plurality of metal atoms from the bottom surface to a lower portion of a sidewall of the opening
Data Source
AI summary
Methods for depositing metal in high aspect ratio features formed on a substrate are provided herein. In some embodiments, a method includes applying first RF power at VHF frequency to target comprising metal disposed above substrate to form plasma, applying DC power to target to direct plasma towards target, sputtering metal atoms from target using plasma while maintaining pressure in PVD chamber sufficient to ionize predominant portion of metal atoms, depositing first plurality of metal atoms on bottom surface of opening and on first surface of substrate, applying second RF power to redistribute at least some of first plurality from bottom surface to lower portion of sidewalls of the opening, and depositing second plurality of metal atoms on upper portion of sidewalls by reducing amount of ionized metal atoms in PVD chamber, wherein first and second pluralities form a first layer deposited on substantially all surfaces of opening.