Backside Epitaxial Source/Drain Growth for Lower Contact Resistance
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Solution Overview
Problem
Reduced contact area in semiconductor devices due to smaller sizes leads to increased resistance and slower switching speeds, and existing processes only partially expose contact structures, increasing resistance further.
Innovation Solution
The formation of backside epitaxial source or drain regions is implemented to increase contact area by growing additional regions on the backside of the semiconductor device, which can be more heavily doped to reduce resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If integrated circuits are scaled downward in size, then device density is improved, but contact area is reduced leading to increased resistance
Solution Approach 1:
The patent applies dimensionality change by transitioning from a single-sided contact structure to a dual-sided contact structure. Backside contacts are formed on the rear surface of the substrate, creating a new spatial dimension for electrical connection. This allows current to flow through multiple paths (frontside and backside), effectively increasing the total contact area without increasing the planar footprint, thus maintaining device density while reducing contact resistance.
Solution Approach 2:
The patent implements nesting by integrating backside contacts within the existing substrate structure. The backside contact regions are formed by removing substrate material and filling with conductive material, nesting the contact structure within the substrate's thickness dimension. This nested approach increases contact area without requiring additional lateral space, resolving the contradiction between device density and contact resistance.
2Ease of manufacture
If existing processes are used to form contacts, then manufacturing simplicity is maintained, but only a portion of the structure is exposed resulting in increased contact resistance
Solution Approach 1:
The patent applies segmentation by dividing the contact formation process into distinct regions: frontside contact regions and backside contact regions. The backside contacts are formed in separate recesses on the rear surface of the substrate, allowing independent optimization of each contact region. This segmentation enables the use of standard frontside contact processes while adding backside contacts through a similar but separate process flow, maintaining manufacturing simplicity while reducing contact resistance through increased total contact area.
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 reduces backside contact resistance and enhances switching speeds by increasing the contact area and using higher dopant concentrations in the backside regions.
Implementation Method 1
a backside source or drain region is grown within the recess and merged with the given source or drain region
Data Source
Figure 1A
Figure 1B~1C
Figure 2A~2B
AI summary
Techniques are provided to form an integrated circuit having backside epaxially grown source or drain regions in addition to the frontside source or drain regions to reduce backside contact resistance. A semiconductor device includes a gate structure around or otherwise on a semiconductor region. The gate structure includes a gate dielectric and a gate electrode. The substrate beneath the semiconductor device may be removed from the backside to expose a subfin region beneath the semiconductor region. The subfin region may be removed using a backside etch to open a backside recess that exposes a bottom surface of a given frontside source or drain region. A backside source or drain region may be grown on a bottom surface of the given frontside source or drain region and remain within the backside recess or extend out of the backside recess.