Ion Extractor for Local Plasma Density in IC Fabrication
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Solution Overview
Problem
Conventional IC fabrication processes face challenges in resputtering without damaging dielectric layers, particularly due to microtrenching, which occurs when dielectric layers are exposed to high-energy ions during the removal of diffusion barrier materials, leading to reduced adhesion and increased line-to-line leakage.
Innovation Solution
The method involves generating a high-density, low-energy plasma with an ion flux of at least 5·10^15 ions/cm²s and mean energy of less than 250 eV, achieved by using a positively biased ion extractor to transfer electrons from a high-density donor plasma region to a lower-density acceptor plasma region near the wafer, increasing plasma density to at least 5·10^11 electrons/cm³ and improving uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional sputter etching is performed to remove diffusion barrier materials, then material removal efficiency is improved, but dielectric layers become damaged due to microtrenching from high-energy ion exposure
Solution Approach 1:
The invention changes the plasma parameters by creating a high-density plasma environment with increased ion flux (greater than 10^16 ions/cm²s) while controlling ion energy to be less than 200 eV. This parameter transformation allows efficient material removal through high ion flux while preventing dielectric damage by maintaining low ion energy, thereby resolving the contradiction between productivity and reliability
Solution Approach 2:
The invention introduces a dynamically controllable ion extractor that can adjust its positive bias voltage to optimize the transfer of electrons from the donor plasma region to the acceptor plasma region. This dynamic control enables real-time adjustment of plasma density and ion flux, allowing the system to maintain high material removal rates while protecting dielectric layers from damage
2Productivity
If high-energy ions are used for sputter etching, then etch rates are improved, but microtrenching occurs in exposed dielectric layers
Solution Approach 1:
The invention fundamentally changes the ion energy parameter from conventional high-energy ions to low-energy ions (less than 200 eV) while compensating for the reduced etching power through dramatically increased ion flux. This parameter substitution eliminates microtrenching damage while maintaining high etch rates through the high flux of low-energy ions
Solution Approach 2:
The ion extractor acts as an intermediary device that mediates between the high-density donor plasma region and the acceptor plasma region near the wafer. By applying a positive bias to the ion extractor, electrons are transferred from the donor to the acceptor region, which indirectly increases the ion flux to the wafer while keeping ion energy low, thus preventing microtrenching
3Quantity of substance
If plasma density is increased near the wafer, then ion flux is improved for better etching, but plasma uniformity across the wafer surface deteriorates
Solution Approach 1:
The invention segments the plasma into two distinct regions: a high-density donor plasma region and a lower-density acceptor plasma region near the wafer. The ion extractor is positioned to selectively transfer electrons from the donor region to the acceptor region, creating a controlled high ion flux environment that maintains uniformity across the wafer surface by localized electron transfer rather than global plasma density increase
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 effectively eliminates microtrenching, enhances etch rates, and improves the quality of deposited films by maintaining high plasma density and uniformity near the wafer, thereby increasing throughput and reliability of IC devices.
Implementation Method 1
applying a positive bias to an ion extractor to transfer electrons from a high-density donor plasma region to a lower-density acceptor plasma region near the wafer, increasing plasma density
Implementation Method 2
positively charged inert gas ions or metal ions impinge on a negatively biased substrate, removing or redistributing portions of exposed material residing on a wafer substrate
Implementation Method 3
A plasma having a first plasma density at a first elevation above the substrate and a second plasma density at a second elevation above the substrate, both within a magnetically shaped or confined plasma region
Data Source
AI summary
Local plasma density, e.g., the plasma density in the vicinity of the substrate, is increased by providing an ion extractor configured to transfer ions and electrons from a first region of magnetically confined plasma (typically a region of higher density plasma) to a second region of plasma (typically a region of lower density plasma). The second region of plasma is preferably also magnetically shaped or confined and resides between the first region of plasma and the substrate. A positively biased conductive member positioned proximate the second region of plasma serves as an ion extractor. A positive bias of about 50-300 V is applied to the ion extractor causing electrons and subsequently ions to be transferred from the first region of plasma to the vicinity of the substrate, thereby forming higher density plasma. Provided methods and apparatus are used for deposition and resputtering.