Source/Drain Carbon Implant for Boron Diffusion Control
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Solution Overview
Problem
In CMOS manufacturing, boron out-diffusion from PMOS source/drain regions leads to short channel effects and voltage threshold roll-off, which is not adequately controlled by existing methods, causing damage to the sidewalls and bottom of recessed regions and resulting in reduced device performance.
Innovation Solution
Incorporating a barrier dopant, such as carbon, into the remaining portion of the source and drain regions to retard boron out-diffusion, combined with a reduced pocket implant dose and nitrogen incorporation during annealing to repair damage and passivate interfaces, effectively reducing boron diffusion into the channel region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high concentration boron doping is incorporated into e-SiGe to reduce sheet resistance and contact resistance in source drain regions, then electrical conductivity is improved, but boron out-diffusion into the channel region increases causing short channel effects
Solution Approach 1:
A carbon barrier layer is introduced as an intermediary between the boron-doped e-SiGe source/drain regions and the channel. This carbon layer acts as a diffusion barrier that prevents boron atoms from migrating into the channel region while allowing the high boron concentration to remain in the source/drain regions for low resistance contacts.
Solution Approach 2:
The patent applies different doping concentrations and material compositions to different regions: high boron concentration in the e-SiGe source/drain regions for conductivity, carbon enrichment at the interface for barrier function, and appropriate channel doping. This local differentiation allows each region to optimize its specific function without compromising others.
2Reliability
If high dose pocket implants are used to counteract boron out-diffusion, then short channel effects are reduced, but damage to the sidewalls and bottom of recessed source/drain regions increases
Solution Approach 1:
The carbon barrier layer serves as a mediator that eliminates the need for high-dose pocket implants. By providing a physical barrier to boron diffusion, the carbon layer allows the use of lower, less damaging implant doses while still achieving effective short channel effect control.
Solution Approach 2:
The patent converts the potential harm of boron diffusion into a benefit by using the carbon barrier to control and direct boron distribution. The boron remains confined to where it is needed (source/drain regions) for low resistance, while the carbon barrier prevents its harmful migration into the channel.
3Object-generated harmful factors
If carbon is implanted to form a barrier to retard boron out-diffusion, then boron diffusion is reduced, but implant damage may occur requiring repair annealing
Solution Approach 1:
The carbon implant is performed as a preliminary step before e-SiGe deposition and pocket implants. This preliminary carbon barrier formation protects against subsequent boron diffusion, and any implant damage is addressed through repair annealing processes that restore the crystal structure before final device formation.
Solution Approach 2:
The carbon barrier layer is established beforehand to cushion against boron diffusion. The subsequent rapid thermal annealing process serves to repair any damage from the carbon implant and activate the barrier layer, ensuring it functions effectively before the boron-containing e-SiGe is deposited.
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 a 30% reduction in drain-induced barrier lowering, lower e-SiGe resistance, and reduced gate edge damage, improving short channel effects and device performance by minimizing boron out-diffusion and enhancing the integrity of the source/drain regions.
Implementation Method 1
A barrier dopant is incorporated into a remaining portion of the source and drain regions to retard boron out-diffusion
Implementation Method 2
nitrogen incorporation during annealing to repair damage and passivate interfaces
Implementation Method 3
Boron doping may be incorporated into the e-SiGe for lower sheet resistance and contact resistance in the source drain regions
Implementation Method 4
growing an epitaxial layer of SiGe within recesses in the source/drain regions
Implementation Method 5
lattice mismatch creates a uni-axial compressive stress within the channel region
Data Source
AI summary
A semiconductor device system, structure, and method of manufacture of a source/drain to retard dopant out-diffusion from a stressor are disclosed. An illustrative embodiment comprises a semiconductor substrate, device, and method to retard sidewall dopant out-diffusion in source/drain regions. A semiconductor substrate is provided with a gate structure, and a source and drain on opposing sides of the gate structure. Recessed regions are etched in a portion of the source and drain. Doped stressors are embedded into the recessed regions. A barrier dopant is incorporated into a remaining portion of the source and drain.