Carbon Dopant Diffusion Control in Semiconductor Fin Structures
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Solution Overview
Problem
In semiconductor fin fabrication, particularly for finFETs, controlling dopant diffusion is challenging due to non-uniform carbon doping caused by conventional ion implantation methods, especially in three-dimensional structures at smaller technology nodes, leading to issues like drain-induced barrier lowering and device isolation problems.
Innovation Solution
A method involving depositing a carbon-containing layer on a semiconductor fin, followed by annealing to diffuse carbon, removing the layer, and growing a dopant-containing epitaxial layer, with subsequent annealing to control dopant diffusion, ensuring uniform carbon doping and limiting dopant spread.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional ion implantation is used to introduce carbon dopant, then carbon doping can be performed, but non-uniform carbon doping occurs across the fin structure leading to non-uniform dopant out-diffusion
Solution Approach 1:
The patent replaces the mechanical ion implantation process with a chemical deposition process (CVD or PECVD) to introduce carbon-containing material. This substitution allows conformal coverage of the fin structure surfaces, achieving uniform carbon doping that was not possible with directional ion implantation, especially for features below 10 nanometers.
Solution Approach 2:
The patent changes the physical and chemical parameters of the carbon introduction process by using vapor-phase deposition instead of solid-phase ion implantation. This parameter change enables the carbon-containing material to conformally deposit on all surfaces of the fin structure, including top and side surfaces, resulting in uniform carbon distribution.
2Quantity of substance
If ion implantation is used for carbon doping, then carbon can be introduced into the fin, but the implant beam is blocked by non-planar structures at smaller technology nodes
Solution Approach 1:
The patent replaces the mechanical ion implantation process with a chemical vapor deposition process that can access and deposit material on complex three-dimensional surfaces. The vapor-phase carbon-containing material can conformally coat the fin structures even at 10 nanometer and below technology nodes where ion implantation beams are blocked by the non-planar geometry.
Solution Approach 2:
The patent transitions from a line-of-sight deposition method (ion implantation) to a vapor-phase deposition method that can reach all surfaces from the gas phase. This dimensional change allows carbon-containing material to deposit on top surfaces, side surfaces, and other complex geometries of the fin structure uniformly.
3Manufacturing precision
If non-uniform carbon doping occurs, then carbon doping is achieved, but non-uniform dopant out-diffusion causes drain-induced barrier lowering and device isolation issues
Solution Approach 1:
The patent performs carbon doping before forming the dopant-containing epitaxial layer and before the dopant diffusion anneal. By introducing carbon dopant early in the process when the fin surfaces are accessible, uniform carbon distribution is established throughout the fin structure, which then uniformly limits dopant diffusion during subsequent processing steps.
Solution Approach 2:
The patent uses carbon dopant as an intermediary substance that mediates the dopant diffusion process. The uniformly distributed carbon atoms act as diffusion barriers that limit and control the out-diffusion of dopants from the epitaxial layer, preventing both drain-induced barrier lowering and ensuring proper device isolation.
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 achieves more uniform carbon doping and better control over dopant diffusion, addressing non-uniformity issues and enabling effective modulation of short channel effects and on-resistance in finFETs, even at smaller technology nodes where conventional ion implantation is not viable.
Implementation Method 1
first annealing to diffuse carbon from the carbon-containing layer into at least the second portion of the semiconductor fin
Implementation Method 2
second annealing to diffuse dopant from the dopant-containing epitaxial layer into at least the second portion of the semiconductor fin, the carbon in the second portion of the semiconductor fin limiting diffusion of the dopant
Data Source
AI summary
Methods of forming a semiconductor fin and methods for controlling dopant diffusion to a semiconductor fin are disclosed herein. The methods provide alternative ways to incorporate a carbon dopant into the fin to later control out-diffusion of dopants from a dopant-including epitaxial layer. One method includes depositing a carbon-containing layer over a portion of the fin adjacent to the gate and annealing to diffuse carbon from the carbon-containing layer into at least the portion of the semiconductor fin. This method can be applied to SOI or bulk semiconductor substrates. Another method includes epitaxially growing a carbon dopant containing semiconductor layer for later use in forming the fin.