Angled Ion Implant Pocket Diffusions for Leakage Control
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Solution Overview
Problem
As semiconductor processes shrink, junction leakage currents increase due to misalignment and proximity issues in MOS transistor devices, leading to degraded performance and increased manufacturing costs, with existing solutions requiring additional processing steps and complexity.
Innovation Solution
An additional angled implant of source/drain dopants is performed in the substrate, adjacent to the well or substrate, contemporaneously with existing ion implantation steps, to form source/drain pocket diffusions that prevent excess leakage current without requiring additional masks, photoresist, or etch steps, thus enhancing manufacturing tolerance and device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional processing steps (masks, photoresist, etch) are used to improve junction leakage, then leakage current is reduced, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines the formation of pocket diffusions with the existing source/drain ion implantation step by performing an additional angled implant contemporaneously with the vertical implant. This merging of operations allows leakage reduction without adding separate processing steps, masks, or photoresist cycles.
Solution Approach 2:
The pocket diffusion regions are formed in advance during the source/drain implantation process, before contact formation. This preliminary action ensures that if contacts are misaligned and extend into lightly doped drain regions, the pocket diffusions are already in place to prevent excess leakage current.
2Manufacturing precision
If process tolerances are reduced to improve alignment precision, then manufacturing precision improves, but manufacturing cost and complexity increase
Solution Approach 1:
The patent creates a protective pocket diffusion region that acts as a buffer zone between the contact and the channel. This beforehand cushioning ensures that even if alignment tolerances are exceeded and contacts are formed deeper or misaligned, the pocket diffusion prevents excess leakage, effectively cushioning against manufacturing variations without requiring tighter tolerances.
3Area of moving object
If feature size is reduced to increase device density, then device density increases, but junction leakage current increases
Solution Approach 1:
The patent applies local quality by creating highly doped pocket diffusion regions at specific locations (adjacent to lightly doped drain regions) while maintaining the overall miniaturized device structure. This localized high doping concentration specifically addresses leakage issues in critical areas without requiring overall device enlargement.
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 solution effectively reduces junction leakage current and increases manufacturing tolerance to misalignment, improving the yield and productivity of semiconductor devices without adding complexity or cost, while maintaining device density.
Implementation Method 1
an additional angled implant of source/drain dopants is performed in the substrate
Implementation Method 2
form source/drain pocket diffusions
Data Source
AI summary
A semiconductor device with improved source/drain junctions and methods for fabricating the device are disclosed. A preferred embodiment comprises a MOS transistor with a gate structure overlying a substrate, lightly doped source/drain regions formed in the substrate aligned to the gate structure, sidewall spacers formed on the sidewalls of the gate structure and overlying the lightly doped source/drain regions, deeper source/drain diffusions formed into the substrate aligned to the sidewall spacers and additional pocket implants of source/drain dopants formed at the boundary of the deeper source/drain diffusions and the substrate. In a preferred method, the additional pocket implants are formed using an angled ion implant with the angle being between 4 and 45 degrees from vertical. Additional embodiments include recesses formed in the source/drain regions and methods for forming the recesses.