Ruthenium Interconnect Patterning for Straight Sidewall Etching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor manufacturing, copper's resistivity increases at smaller scales due to photon scattering, and ruthenium etching processes suffer from insufficient fidelity and profile control issues, such as undercutting and corner rounding, which hinder further scaling of semiconductor devices.
Innovation Solution
A method involving iterative N2 plasma passivation, H2 plasma reduction, and O2 plasma etching of a ruthenium layer through a hard mask, forming a ruthenium nitride layer with specific power, pressure, and duration settings to prevent undercutting and corner rounding, and achieving a straight sidewall angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If O2 plasma etching is used to etch ruthenium layer, then etching speed is improved, but profile control deteriorates due to undercutting and corner rounding
Solution Approach 1:
A nitrogen plasma passivation layer is formed on the ruthenium surface before the O2 plasma etching process. This preliminary action creates a protective barrier that prevents direct O2 exposure to the ruthenium, thereby avoiding undercutting and corner rounding while maintaining etching speed through the controlled removal of the passivation layer during etching.
Solution Approach 2:
The nitrogen plasma passivation layer acts as an intermediary between the O2 plasma and the ruthenium layer. It mediates the interaction by providing a controlled interface that allows vertical etching while preventing lateral undercutting, thus improving profile control without sacrificing etching speed.
2Productivity
If O2 plasma etching is used on ruthenium layer, then material removal efficiency is improved, but fidelity deteriorates due to isotropic etching and layer undercutting
Solution Approach 1:
The nitrogen plasma passivation is performed before O2 plasma etching to create a protective layer that enables anisotropic etching behavior. This preliminary step allows the subsequent O2 plasma to remove ruthenium efficiently while maintaining vertical sidewalls and preventing undercutting, thus preserving etching fidelity.
Solution Approach 2:
The process changes the chemical state of the ruthenium surface by forming a nitrogen-passivated layer, which alters how the O2 plasma interacts with the material. This parameter change enables the O2 plasma to etch vertically without the isotropic undercutting that would occur on bare ruthenium, maintaining both productivity and fidelity.
3Ease of manufacture
If copper is used for metal interconnect lines, then ease of manufacture is improved due to electroplating capability, but electrical performance deteriorates at smaller scales due to increased resistivity
Solution Approach 1:
The patent uses ruthenium as a temporary replacement for copper in critical interconnect applications where size matters. While ruthenium requires more complex etching processes, it provides the necessary electrical performance at small scales, accepting the additional manufacturing complexity as a necessary trade-off for maintaining reliability in scaled devices.
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 method enhances the fidelity and profile control of ruthenium etching, preventing undercutting and corner rounding, thereby enabling more precise and scalable semiconductor device manufacturing.
Implementation Method 1
N2 plasma passivation, through an opening in a hard mask, of a ruthenium layer on a substrate including transistors. The N2 plasma passivation task forms a ruthenium nitride layer on the ruthenium layer
Implementation Method 2
The N2 plasma passivation task forms a ruthenium nitride layer on the ruthenium layer
Implementation Method 3
performing an H2 plasma reduction task on the ruthenium nitride layer after the N2 plasma passivation task. The H2 plasma reduction task removes the first portion of the ruthenium nitride layer
Implementation Method 4
The H2 plasma reduction task removes the first portion of the ruthenium nitride layer
Implementation Method 5
O2 plasma etching the ruthenium layer after the H2 plasma reduction task
Implementation Method 6
O2 plasma etching the ruthenium layer
Data Source
AI summary
A method of manufacturing an interconnect in a metal layer in a back-end-of-line of a semiconductor device includes N2 plasma passivation, through an opening a hard mask, of a ruthenium layer on a substrate. The N2 plasma passivation forms a ruthenium nitride layer on the ruthenium layer. The ruthenium nitride layer includes a first portion aligned with the opening and a second portion underneath the hard mask. The method also includes H2 plasma reduction of the ruthenium nitride layer after the N2 plasma passivation. The H2 plasma reduction removes the first portion of the ruthenium nitride layer. The method also includes O2 plasma etching the ruthenium layer after the H2 plasma reduction. The method also includes repeatedly performing the N2 plasma passivation, the H2 plasma reduction, and the O2 plasma etching to remove the ruthenium layer down to the substrate.