Ultra-Shallow Dopant Regions via Solid Phase Diffusion
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Solution Overview
Problem
The semiconductor industry faces challenges in forming ultra-shallow dopant regions with uniform doping profiles and high surface concentration, particularly in complex device structures like FinFETs and tri-gate FETs, due to difficulties with ion implantation techniques that result in lattice damage and non-uniform doping.
Innovation Solution
The method involves depositing dopant layers using atomic layer deposition (ALD) and subsequent thermal treatment to diffuse dopants into the substrate, forming ultra-shallow regions with precise control, allowing for conformal doping of 3D structures and reducing dopant dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion implantation is used to form shallow junctions, then dopant atoms can be driven into the substrate, but the path of energized dopant atoms and implant uniformity become difficult to control at low energies
Solution Approach 1:
The patent replaces the mechanical ion implantation process with a chemical deposition process. Dopant atoms are deposited as a thin film layer on the substrate surface using chemical vapor deposition or atomic layer deposition, eliminating the need for high-energy ion bombardment. This substitution allows precise control of dopant placement and concentration without the path control issues inherent in ion implantation.
Solution Approach 2:
The patent changes the fundamental parameters of the doping process by transitioning from high-energy ion implantation to low-energy chemical deposition. The deposition temperature, pressure, and precursor flow rates are controlled to achieve precise dopant placement at shallow depths, replacing the energy and velocity parameters that are difficult to control in ion implantation.
2Manufacturing precision
If ion implantation is used to form ultra-shallow junctions, then dopant atoms can be introduced, but crystal lattice damage occurs which is difficult to repair and causes current leakage
Solution Approach 1:
The patent replaces the mechanical impact of ion implantation with a gentle chemical deposition process. Dopant atoms are deposited in a neutral or low-energy state as a thin film, avoiding the high-velocity bombardment that causes crystal lattice damage. This eliminates the harmful effect of lattice disruption while achieving the desired shallow junction formation.
Solution Approach 2:
The patent converts the potential harm of dopant introduction by using a deposition process that naturally forms a uniform dopant layer without causing lattice damage. The deposition process itself becomes beneficial by providing both the dopant atoms and a damage-free introduction mechanism, eliminating the need for separate damage repair steps.
3Manufacturing precision
If p-type dopants such as boron are implanted, then dopant atoms can be introduced, but excessive dispersion of dopant atoms occurs after introduction making it difficult to form confined concentration
Solution Approach 1:
The patent performs preliminary confinement of dopant atoms by depositing them as a thin film layer with controlled thickness and composition. The dopant atoms are confined within the deposited film structure before any diffusion occurs, preventing excessive dispersion. Subsequent thermal processing is carefully controlled to achieve the desired diffusion while maintaining concentration confinement that would be difficult to achieve with ion implantation.
4Productivity
If ion implantation is used for high device densities, then doping can be achieved, but shadowing effects make uniform doping of fin structures extremely difficult or impossible
Solution Approach 1:
The patent replaces the line-of-sight mechanical ion implantation process with a chemical deposition process that can conform to three-dimensional structures. The deposition chemistry allows dopant atoms to be delivered to all surfaces of fin structures uniformly, eliminating shadowing effects while maintaining high device density. The conformal deposition capability ensures uniform doping across complex 3D geometries.
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 enables the formation of ultra-shallow dopant regions with controlled depth and concentration, improving electrical performance by minimizing current leakage and achieving uniform doping in complex device structures, overcoming limitations of conventional ion implantation methods.
Implementation Method 1
diffusing, by a thermal treatment, the first dopant from the first dopant layer into the substrate to form a first ultra-shallow dopant region in the substrate
Implementation Method 2
depositing, by atomic layer deposition (ALD), a first dopant layer containing a first dopant in direct contact with the substrate
Data Source
AI summary
A method for forming ultra-shallow dopant regions in a substrate is provided. One embodiment includes depositing a first dopant layer containing a first dopant in direct contact with the substrate, patterning the first dopant layer, depositing a second dopant layer containing a second dopant in direct contact with the substrate adjacent the patterned first dopant layer, the first and second dopant layers containing an oxide, a nitride, or an oxynitride, where the first and second dopant layers contain an n-type dopant or a p-type dopant with the proviso that the first or second dopant layer do not contain the same dopant, and diffusing the first dopant from the first dopant layer into the substrate to form a first ultra-shallow dopant region in the substrate, and diffusing the second dopant from the second dopant layer into the substrate to form a second ultra-shallow dopant region in the substrate.