VHF Plasma PVD Metal Deposition for High Aspect Ratio TSV
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Solution Overview
Problem
Conventional direct current (DC) sputtering in physical vapor deposition (PVD) processes face limitations in depositing metal on vertical sidewalls of high aspect ratio features, leading to incomplete coverage and excessive resputtering, which can result in void formation and overhangs or facets in high aspect ratio features like through silicon via (TSV) structures.
Innovation Solution
The method involves using radio frequency (RF) power at a very high frequency (VHF) to form a plasma and ionize metal atoms in a PVD chamber, followed by applying RF bias power to redistribute deposited metal atoms from the bottom surface to the sidewalls, ensuring continuous coverage and minimizing overhangs or facets by controlling the deposition and redistribution processes.
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 is simple and fast, but the metal coverage on vertical sidewalls is incomplete and excessive resputtering occurs
Solution Approach 1:
The patent changes the sputtering parameters by using RF power at VHF frequency instead of DC power, and maintains a higher pressure in the PVD chamber. These parameter changes enable ionization of metal atoms and improve sidewall coverage while reducing resputtering, resolving the contradiction between coverage completeness and process simplicity
Solution Approach 2:
The patent employs periodic alternation between deposition mode and redistribution mode. During deposition mode, metal atoms are deposited on the substrate; during redistribution mode, RF bias power is applied to redistribute metal atoms to sidewalls. This periodic action ensures complete coverage while managing process complexity
2Productivity
If high bias power is applied in DC PVD to improve deposition rate, then productivity increases, but excessive resputtering occurs causing overhangs and facets
Solution Approach 1:
The patent changes the power application method by using RF bias power instead of DC bias power, and by controlling the timing of bias power application. The RF bias is applied periodically after deposition rather than continuously during deposition, which prevents resputtering while still enabling metal redistribution to sidewalls, thus maintaining both productivity and geometric accuracy
Solution Approach 2:
The patent uses periodic application of RF bias power in a redistribution step following the deposition step. This periodic action allows metal atoms to be redistributed to sidewalls without causing excessive resputtering that would create overhangs and facets, resolving the contradiction between deposition rate and geometric accuracy
3Manufacturing precision
If metal atoms are deposited on the bottom surface of high aspect ratio features, then coverage is achieved, but metal accumulation on the bottom creates voids on the sidewalls
Solution Approach 1:
The patent employs periodic alternation between deposition and redistribution steps. During deposition, metal atoms are supplied to the feature; during redistribution, RF bias power redistributes metal atoms from the bottom surface to the sidewalls. This periodic action prevents metal accumulation on the bottom that would create voids, ensuring uniform metal distribution throughout the feature
Solution Approach 2:
The patent implements a feedback mechanism where the redistribution step responds to the deposition step. The RF bias power is applied after deposition to redistribute metal atoms that have accumulated on the bottom surface, preventing void formation. This feedback control ensures uniform metal distribution while managing the quantity of metal atoms in different locations
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 provides continuous metal coverage on high aspect ratio features, reducing void formation and overhangs, and is suitable for applications like through silicon via (TSV) fabrication, ensuring reliable electrical connectivity and structural integrity.
Implementation Method 1
applying a first RF power to redistribute at least some of the deposited metal atoms from the bottom surface and upper surface to sidewalls of the opening
Implementation Method 2
depositing the ionized metal atoms on a bottom surface of the opening and on the first surface of the substrate
Implementation Method 3
sputtering metal atoms from the target using the plasma
Data Source
AI summary
Methods of depositing metal in high aspect ratio features are provided herein. In some embodiments, a method of processing a substrate includes applying RF power at VHF frequency to a target comprising metal disposed in the PVD chamber above the substrate to form a plasma from a plasma-forming gas, sputtering metal atoms from the target using the plasma while maintaining a first pressure in the PVD chamber sufficient to ionize a predominant portion of the sputtered metal atoms, depositing the ionized metal atoms on a bottom surface of the opening and on a first surface of the substrate, applying a first RF power to redistribute at least some of the deposited metal atoms from the bottom surface and upper surface to sidewalls of the opening, and repeating the deposition the redistribution processes until a first layer of metal is deposited on substantially all surfaces of the opening.