III-V Semiconductor Layers for Low-Resistance MOS Contacts
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Solution Overview
Problem
Conventional transistor contact structures exhibit high parasitic resistance due to silicon or SiGe valence band alignment with metal, limiting current performance, particularly in p-type transistor structures where typical industry approaches with higher bandgap materials are not effective.
Innovation Solution
Incorporating an intermediate III-V semiconductor material layer with a small bandgap (less than 0.5 eV) between source/drain regions and contact metals, which can be doped to enhance conductivity, thereby reducing contact resistance across both p-type and n-type regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional metal contacts are used directly on silicon or SiGe source/drain regions, then the contact structure is simple, but the parasitic contact resistance is high due to valence band alignment issues
Solution Approach 1:
An intermediate III-V semiconductor material layer is inserted between the metal contact and the silicon/SiGe source/drain region. This intermediate layer acts as a mediator that facilitates better band alignment and reduces the contact resistance barrier, enabling lower parasitic resistance without requiring complex multi-layer structures or special processing conditions
Solution Approach 2:
The invention changes the material parameter (bandgap) by selecting III-V semiconductor materials with small bandgaps (less than 0.5 eV) such as InSb, InAs, or GaSb. This parameter change enables the intermediate layer to provide optimal band alignment with both the silicon/SiGe source/drain regions and the metal contact, significantly reducing contact resistance compared to conventional direct metal-to-silicon contacts
2Reliability
If higher bandgap materials are used for contacts in p-type transistor structures, then the contact structure follows industry standards, but the contact resistance remains high and current performance is limited
Solution Approach 1:
The invention fundamentally changes the material selection criterion from conventional high-bandgap materials to small-bandgap III-V semiconductor materials (bandgap less than 0.5 eV). This parameter change enables effective contact formation in p-type transistor structures where conventional materials fail, as the small bandgap allows for better carrier transport and lower contact resistance
Solution Approach 2:
The intermediate III-V semiconductor layer provides universal applicability across different transistor types (n-type and p-type) and different source/drain materials (silicon, SiGe, germanium). The same small-bandgap III-V material can be used in various contact configurations, making the solution versatile and adaptable to different device architectures including planar, finFET, and nanowire transistors
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 small bandgap III-V semiconductor material layer significantly decreases contact resistance, enabling higher drive current and improved performance in transistor structures, applicable to various architectures including planar, finned, and nanowire transistors.
Implementation Method 1
Incorporating an intermediate III-V semiconductor material layer with a small bandgap (less than 0.5 eV) between source/drain regions and contact metals
Implementation Method 2
which can be doped to enhance conductivity, thereby reducing contact resistance across both p-type and n-type regions
Data Source
AI summary
Techniques are disclosed for forming transistor devices having reduced parasitic contact resistance relative to conventional devices. In some example embodiments, the techniques can be used to implement the contacts of MOS transistors of a CMOS device, where an intermediate III-V semiconductor material layer is provided between the p-type and n-type source/drain regions and their respective contact metals to significantly reduce contact resistance. The intermediate III-V semiconductor material layer may have a small bandgap (e.g., lower than 0.5 eV) and/or otherwise be doped to provide the desired conductivity. The techniques can be used on numerous transistor architectures (e.g., planar, finned, and nanowire transistors), including strained and unstrained channel structures.