Tungsten Silicide Ohmic Layer for Semiconductor Interface Resistance
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Solution Overview
Problem
Conventional semiconductor devices face high resistance issues due to the silicidation reaction between polysilicon and metal layers, leading to increased resistance and void formation at the interface, which hampers the performance of gate electrodes and metal wiring.
Innovation Solution
A tungsten silicide layer with a specific atomic ratio of tungsten to silicon (1:5 to 1:15) is introduced as an ohmic layer to reduce interface resistance between polysilicon and metal layers, preventing silicidation and maintaining the integrity of the metal layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a tungsten silicide layer with atomic ratio 1:2 to 1:3 is formed between polysilicon and tungsten layers, then interface resistance is reduced, but the diffusion barrier layer decomposes in thermal processes causing silicidation of the tungsten layer and void formation
Solution Approach 1:
The patent changes the atomic ratio parameter of tungsten to silicon in the silicide layer from the conventional 1:2 to 1:3 range to a new range of 1:4 to 1:6. This parameter modification prevents the decomposition of the diffusion barrier layer during thermal processes while maintaining low interface resistance, thereby resolving the contradiction between reducing interface resistance and preventing structural degradation.
Solution Approach 2:
The patent creates a composite structure consisting of a polysilicon layer, a tungsten silicide layer with specific composition (1:4 to 1:6 atomic ratio), and a tungsten layer. This composite material system achieves both low interface resistance and prevention of silicidation reactions by optimizing the intermediate silicide layer's composition to act as both a resistance-reducing element and a protective barrier.
2Manufacturing precision
If a metal film is formed on a polysilicon film to reduce resistance, then conductive performance is improved, but silicidation reaction occurs between the metal film and polysilicon film
Solution Approach 1:
The patent introduces a tungsten silicide layer with atomic ratio 1:4 to 1:6 as an intermediary between the polysilicon layer and the tungsten layer. This intermediate layer serves as a mediator that prevents direct contact and harmful silicidation reactions between the metal film and polysilicon film, while simultaneously maintaining low interface resistance for improved conductive performance.
Solution Approach 2:
The patent develops a composite material system with three distinct layers: polysilicon, tungsten silicide (with optimized 1:4 to 1:6 atomic ratio), and tungsten. This composite structure enables both low resistance and prevention of harmful silicidation reactions by carefully selecting the composition of the intermediate silicide layer.
3Manufacturing precision
If a tungsten layer is formed to reduce resistance, then electrical characteristics are improved, but the tungsten layer is converted into silicide layer pattern due to thermal process
Solution Approach 1:
The patent forms the tungsten silicide layer with atomic ratio 1:4 to 1:6 before the thermal process that would otherwise cause silicidation. This preliminary action of creating a stable silicide layer with optimized composition prevents the subsequent conversion of the tungsten layer into silicide, maintaining both electrical characteristics and compositional stability throughout the manufacturing process.
Solution Approach 2:
The patent modifies the silicon content parameter in the tungsten silicide layer, setting the atomic ratio of tungsten to silicon in the range of 1:4 to 1:6. This parameter change creates a composition that is stable under thermal processing conditions, preventing the unwanted conversion of the tungsten layer while maintaining low electrical resistance.
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 use of a tungsten silicide layer with the specified atomic ratio effectively reduces the contact resistance and prevents silicidation, resulting in improved electrical characteristics and reliability of semiconductor devices by maintaining low resistance and preventing void formation.
Implementation Method 1
a metal film of a conductive pattern may be easily silicided in a formation of the metal film on a polysilicon film
Data Source
AI summary
In an ohmic layer and methods of forming the ohmic layer, a gate structure including the ohmic layer and a metal wiring having the ohmic layer, the ohmic layer is formed using tungsten silicide that includes tungsten and silicon with an atomic ratio within a range of about 1:5 to about 1:15. The tungsten silicide may be obtained in a chamber using a reaction gas including a tungsten source gas and a silicon source gas by a partial pressure ratio within a range of about 1.0:25.0 to about 1.0:160.0. The reaction gas may have a partial pressure within a range of about 2.05 percent to about 30.0 percent of a total internal pressure of the chamber. When the ohmic layer is employed for a conductive structure, such as a gate structure or a metal wiring, the conductive structure may have a reduced resistance.