TiOx/Ti MIS Contact Resistance Reduction via ALD Stoichiometry Control
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Solution Overview
Problem
As semiconductor devices shrink to smaller technology nodes, the deposition of low resistance materials like titanium becomes challenging due to increasing aspect ratios, leading to incomplete step coverage and poor barrier performance in semiconductor devices.
Innovation Solution
A method for forming sub-stoichiometric titanium oxide on a semiconductor substrate by depositing titanium using titanium tetraiodide and subsequent plasma exposure, followed by treatment with an oxidant to achieve a conformal and low-resistance layer, which can be used in MIS contact schemes to reduce contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional deposition methods are used to deposit low resistance materials, then contact resistance is reduced, but step coverage becomes incomplete due to increasing aspect ratios
Solution Approach 1:
The patent changes the deposition parameters by using atomic layer deposition (ALD) with titanium tetraiodide precursor and controlled plasma exposure, transitioning from conventional deposition to a method that achieves both low resistance and complete step coverage through precise control of deposition conditions
Solution Approach 2:
The patent creates a composite titanium oxide layer with controlled stoichiometry (TiOx where x<2) that combines the low resistance properties of metallic titanium with the insulating properties of titanium oxide, achieving both electrical performance and conformal coverage
2Length of moving object
If feature dimensions are shrunk to smaller technology nodes, then device scaling is achieved, but deposition of low resistance materials becomes more challenging
Solution Approach 1:
The patent segments the deposition process into discrete atomic layers through ALD cycles, allowing precise control of film thickness and composition even at nanoscale dimensions, making deposition feasible at smaller technology nodes
Solution Approach 2:
The patent replaces conventional physical vapor deposition with chemical vapor deposition using ALD, where surface chemistry reactions enable conformal deposition on high aspect ratio structures that cannot be achieved by line-of-sight physical deposition methods
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
The method results in highly conformal and pure titanium layers with low contamination, achieving lower contact resistance and high step coverage, suitable for front-end of line (FEOL) applications and reducing energy consumption in semiconductor devices.
Implementation Method 1
exposing the substrate to an ignited plasma
Implementation Method 2
treating the substrate includes exposing the substrate to the titanium-containing precursor and an oxidant
Data Source
AI summary
Methods of depositing and tuning deposition of sub-stoichiometric titanium oxide are provided. Methods involve depositing highly pure and conformal titanium on a substrate in a chamber by (i) exposing the substrate to titanium tetraiodide, (ii) purging the chamber, (iii) exposing the substrate to a plasma, (iv) purging the chamber, (v) repeating (i) through (iv), and treating the deposited titanium on the substrate to form sub-stoichiometric titanium oxide. Titanium oxide may also be deposited prior to depositing titanium on the substrate. Treatments include substrate exposure to an oxygen source and/or annealing the substrate.