Raised Source Drain Silicide Contact Resistance Reduction
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Solution Overview
Problem
In current CMOS technology, silicide contact resistance is a significant performance limiting factor, especially with reduced contact length of CMOS transistors due to device pitch scaling, which affects the overall performance of semiconductor devices.
Innovation Solution
The proposed solution involves increasing the silicide contact surface area by recessing the raised source drain structures, allowing for a substantial reduction in contact resistance without altering the device pitch or thermal processing cycles, and applying a layer of field dielectric to impart stress to the channel region, enhancing carrier mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device pitch is scaled down to increase device density, then device density is improved, but contact length is reduced which increases contact resistance
Solution Approach 1:
The patent extends the silicide contact from a two-dimensional surface contact to a three-dimensional structure by forming trenches through the raised source/drain and filling them with silicide material. This vertical extension into the third dimension increases the contact surface area without increasing the lateral footprint, thereby reducing contact resistance while maintaining scaled device pitch.
Solution Approach 2:
The contact structure is segmented into multiple regions: the original surface contact area and additional trench regions extending vertically through the raised source/drain. This segmentation creates multiple parallel current paths through the silicide contact, effectively reducing the overall contact resistance by dividing the current flow into multiple channels.
2Reliability
If contact surface area is increased to reduce contact resistance, then contact resistance is reduced, but device pitch must be increased
Solution Approach 1:
Instead of increasing the lateral dimensions (device pitch) to expand contact area, the patent utilizes the vertical dimension by etching trenches through the raised source/drain structures. This allows the contact area to expand downward into the substrate while maintaining the same lateral footprint, thus reducing contact resistance without increasing device pitch.
3Reliability
If thermal processing cycles are modified to reduce contact resistance, then contact resistance is reduced, but manufacturing complexity increases
Solution Approach 1:
The silicide formation process is made self-aligned, where the silicide automatically forms in the trench regions through standard salicide (self-aligned silicide) processing. The raised source/drain structures and trench geometries guide the silicide deposition and formation without requiring additional alignment steps or modified thermal cycles, thereby reducing contact resistance while maintaining manufacturing simplicity.
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 effectively reduces access resistance by increasing the silicide contact surface area and can be applied to both NFET and PFET devices, improving the performance of semiconductor transistors without requiring changes in the typical thermal processing cycles.
Implementation Method 1
Each trench comprises silicide formed on sidewalls and a bottom surface of at least a portion of the trench
Implementation Method 2
applying a layer of field dielectric to impart stress to the channel region, enhancing carrier mobility
Data Source
AI summary
A structure has at least one field effect transistor having a gate stack disposed between raised source drain structures that are adjacent to the gate stack. The gate stack and raised source drain structures are disposed on a surface of a semiconductor material. The structure further includes a layer of field dielectric overlying the gate stack and raised source drain structures and first contact metal and second contact metal extending through the layer of field dielectric. The first contact metal terminates in a first trench formed through a top surface of a first raised source drain structure, and the second contact metal terminates in a second trench formed through a top surface of a second raised source drain structure. Each trench has silicide formed on sidewalls and a bottom surface of at least a portion of the trench. Methods to fabricate the structure are also disclosed.