Selective Oxidation of Silicon in Semiconductor Devices
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Solution Overview
Problem
Existing selective oxidation techniques are ineffective in protecting titanium or titanium nitride structures from oxidation, leading to increased resistance and potential destruction of metal or metal nitride components in semiconductor devices, as they often result in unwanted nitridation or oxidation of silicon oxides.
Innovation Solution
A method for selective oxidation involving a partially-fabricated integrated circuit with exposed silicon and metal-containing portions, where the silicon is oxidized in an atmosphere containing an oxidant and a reducing agent at concentrations of 10 vol % or less, maintaining low oxygen content in metal nitrides and preventing nitridation of silicon oxides, thereby achieving low sheet resistance and preserving the integrity of metal-containing parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional oxidation methods are used to form silicon oxide, then silicon oxidation is achieved, but metal or metal nitride structures are oxidized leading to increased resistance and potential destruction
Solution Approach 1:
A reducing agent is introduced as an intermediary substance in the oxidation atmosphere. This reducing agent selectively protects metal and metal nitride structures from oxidation by creating a chemical environment that preferentially oxidizes silicon while reducing oxidants near metal surfaces, thereby maintaining metal structure integrity during silicon oxide formation
Solution Approach 2:
The oxidation process parameters are modified by adding a reducing agent to the oxidation atmosphere and controlling the temperature within a specific range (600°C to 900°C). This parameter change creates a chemically selective environment where silicon oxidizes preferentially while metal structures are protected, achieving both silicon oxide formation and metal structure preservation
2Reliability
If reducing agent concentration is increased to protect metal structures, then metal oxidation is reduced, but silicon oxide formation is inhibited
Solution Approach 1:
The concentration of the reducing agent is precisely controlled within the range of 0.1 to 10 vol% in the oxidation atmosphere. This optimized parameter range allows sufficient protection of metal structures from oxidation while maintaining adequate oxidizing conditions for complete silicon oxide formation, resolving the trade-off between metal protection and oxide quality
3Manufacturing precision
If oxidation is performed to form thick silicon oxide layers, then dielectric properties are improved, but metal conductivity is degraded
Solution Approach 1:
The reducing agent acts as a protective intermediary during the oxidation process, creating a chemical barrier that prevents oxidants from attacking metal structures. This allows the oxidation to proceed to form thick silicon oxide layers (sufficient for dielectric properties) while the reducing agent continuously protects the metal films from oxidation-induced conductivity degradation
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 effectively reduces oxygen content in metal nitrides to 2 atomic % or less, achieving low sheet resistance and preventing unwanted oxidation or nitridation, allowing for the formation of thick silicon oxide layers while maintaining the conductivity of metal films.
Implementation Method 1
The exposed silicon and metal-containing portions are exposed to a reducing agent during oxidizing. After oxidizing, an oxygen concentration in the exposed metal-containing portion is about 2 atomic % or less
Implementation Method 2
The exposed silicon portion is oxidized by exposing the partially-fabricated integrated circuit to an atmosphere containing an oxidant
Data Source
AI summary
Silicon is selectively oxidized relative to a metal-containing material in a partially-fabricated integrated circuit. In some embodiments, the silicon and metal-containing materials are exposed portions of a partially-fabricated integrated circuit and may form part of, e.g., a transistor. The silicon and metal-containing material are oxidized in an atmosphere containing an oxidant and a reducing agent. In some embodiments, the reducing agent is present at a concentration of about 10 vol % or less.