Semiconductor Contact Stacks for Low-Resistance N/P MOS Interfaces
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Solution Overview
Problem
Existing titanium silicide-based materials for source/drain contacts in semiconductor devices are not optimal for either N-type or P-type transistors and cannot be adjusted based on transistor type, leading to high resistance issues detrimental to smaller scale devices.
Innovation Solution
The method involves forming a low resistance interface between source/drain contact surfaces and metal contacts by depositing an insulating layer with a specific formation energy followed by a conductive layer with a lower formation energy, or by using a non-stoichiometric metal oxide layer to adjust the work function and achieve optimal contact resistance for N-type and P-type transistors separately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If titanium silicide-based materials are applied to source/drain contacts, then contact resistance is reduced for large scale devices, but resistance remains high for smaller scale devices
Solution Approach 1:
The patent applies different material compositions tailored to specific transistor types (N-type vs P-type). For N-type transistors, a first material composition is used, while for P-type transistors, a second material composition is used. This local customization of material properties to match the specific transistor type resolves the contradiction by ensuring optimal contact resistance for each device category rather than using a universal material.
Solution Approach 2:
The patent changes the material composition parameters based on transistor type requirements. By adjusting the chemical composition and stoichiometry of the contact materials, the patent achieves low contact resistance for both N-type and P-type transistors. This parameter adjustment allows the same contact structure to be adapted to different transistor types, resolving the adaptability issue.
2Ease of manufacture
If a single material composition is used for all transistors, then manufacturing is simplified, but optimal contact resistance cannot be achieved for both N-type and P-type transistors
Solution Approach 1:
The patent implements local quality by specifying different material compositions for different transistor types. The contact structure is customized locally to match the electrical characteristics of N-type or P-type transistors, ensuring optimal contact resistance for each case while maintaining a systematic approach to manufacturing.
Solution Approach 2:
The patent creates a universal contact formation methodology that can handle both N-type and P-type transistors through material composition adjustment. The same contact structure design and formation process are used universally, but the material parameters are adjusted based on transistor type, providing both manufacturing simplicity and optimal performance.
3Reliability
If titanium silicide-based materials are used, then contact resistance is acceptable for large scale devices, but device speed is limited
Solution Approach 1:
The patent changes the material composition parameters to achieve lower contact resistance, which directly enables higher transistor speed. By optimizing the material stoichiometry and composition for each transistor type, the contact resistance is reduced to levels that no longer limit device speed, while maintaining reliability.
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 results in highly conductive contacts that enhance device speed, lower operating voltages, and improve performance for both N-type and P-type MOS devices.
Implementation Method 1
depositing an insulating layer that comprises a first material on a contact surface... and depositing a conductive layer that comprises a second material over a surface of the insulating layer
Implementation Method 2
depositing a non-stoichiometric layer that comprises a first material on a contact surface... wherein the first material comprises oxygen and the first material is non-stoichiometrically deficient in oxygen
Data Source
AI summary
The methods of the present disclosure enable formation of highly conductive contacts that facilitate in increasing the device speed and lowering the operating voltages of semiconductor devices such as, but not limited to, metal-on-semiconductor (MOS) transistors and the like. In one embodiment, the methods create the optimal contacts, useful in N type or P type MOS devices, by forming metal-insulator-semiconductor (MIS) contact structure or a non-stoichiometric layer contact structure. It is noted that N type or P type contacts require different work function metals to achieve a low Schottky barrier height (SBH).