Conformal Doping via Plasma-Activated ALD for 3D Gate Structures
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Solution Overview
Problem
Conventional ion implantation techniques are inadequate for doping 3D gate structures due to directional limitations, leading to variability in dopant dose retention and diffusion, especially in high aspect ratio structures, and plasma doping faces challenges with sputter erosion and process control.
Innovation Solution
The method involves forming conformal film layers using atomic layer deposition (ALD) and conformal film deposition (CFD) techniques to create a dopant source on the substrate, allowing for precise doping of 3D structures by driving dopants into the substrate through thermally mediated diffusion processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion implantation techniques are used for doping 3D gate structures, then doping can be performed, but directional limitations cause variability in dopant dose retention and diffusion especially in high aspect ratio structures
Solution Approach 1:
Instead of directing ions onto the substrate surface (conventional ion implantation), the patent inverts the approach by first depositing a conformal dopant-containing film layer over the entire 3D structure, then driving the dopant from the film into the substrate. This inversion eliminates directional limitations and enables uniform doping of high aspect ratio structures including sidewalls and top surfaces.
Solution Approach 2:
The patent introduces a conformal film layer containing dopant species as an intermediary between the doping source and the substrate. This film layer serves as a mediator that delivers dopants uniformly to all surfaces of 3D structures, including those inaccessible to direct ion implantation, thereby resolving the adaptability issue while maintaining precision.
2Area of stationary object
If ion implantation tilt angle is changed to dope lateral and vertical surfaces, then coverage can be improved, but considerable variability in dopant dose retention and diffusion range occurs especially on sidewalls
Solution Approach 1:
Rather than tilting the ion beam to achieve coverage (which causes shadowing and dose variability), the patent inverts the approach by depositing a conformal film that coats all surfaces vertically, then driving dopants horizontally into the substrate. This achieves complete surface coverage while maintaining uniform dopant distribution.
Solution Approach 2:
The patent transitions from a single-directional ion implantation approach to a multi-dimensional conformal film deposition followed by dopant diffusion. The conformal film deposits in all directions simultaneously, and the subsequent dopant drive-in diffuses dopants into the substrate from all surfaces, achieving uniform doping across complex 3D geometries without tilt-angle variability.
3Ease of manufacture
If plasma doping technique is used, then doping can be performed, but simultaneous sputter erosion occurs due to high energy ions in the plasma
Solution Approach 1:
The patent replaces the mechanical sputtering process (physical bombardment by high energy plasma ions) with a chemical deposition process (ALD or CFD) followed by thermal dopant diffusion. This substitution eliminates substrate erosion while maintaining doping capability, as the conformal film deposition and dopant drive-in occur without high energy ion bombardment.
Solution Approach 2:
The patent changes the energy parameter of the doping process from high energy (plasma doping with energetic ions causing sputtering) to low energy (thermal diffusion from conformal film). By controlling the dopant drive-in temperature and time rather than ion energy, the process achieves doping without substrate material loss.
4Ease of manufacture
If plasma doping technique is used, then doping can be performed, but dopant dose and conformality sensitively depend on ion to radical density ratio in the plasma leading to difficulties in process control
Solution Approach 1:
The patent replaces plasma-based doping (which requires control of ion to radical density ratios) with conformal film deposition followed by thermal dopant diffusion. This substitution eliminates the complex plasma parameter interdependencies, replacing them with simpler, more controllable thermal diffusion parameters (temperature and time).
Solution Approach 2:
The patent changes the controlling parameters from plasma chemistry (ion to radical density ratio) to thermal diffusion (temperature and time). This parameter transformation simplifies process control, as thermal diffusion is governed by well-understood Fick's laws with fewer sensitive interdependencies compared to plasma doping.
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 effective doping of 3D structures with improved uniformity and reduced series resistance, increasing current density by 10% to 25% and offering better control over dopant concentration and distribution.
Implementation Method 1
adsorbing the dopant precursor directly onto the surface of the patterned substrate or onto a material adhered to the surface under conditions whereby the dopant precursor forms an adsorption-limited layer
Implementation Method 2
driving some of the dopant from the first film layer into the substrate to form a conformal doping profile in the substrate
Data Source
AI summary
Disclosed herein are methods of doping a patterned substrate in a reaction chamber. The methods may include forming a first conformal film layer which has a dopant source including a dopant, and driving some of the dopant into the substrate to form a conformal doping profile. In some embodiments, forming the first film layer may include introducing a dopant precursor into the reaction chamber, adsorbing the dopant precursor under conditions whereby it forms an adsorption-limited layer, and reacting the adsorbed dopant precursor to form the dopant source. Also disclosed herein are apparatuses for doping a substrate which may include a reaction chamber, a gas inlet, and a controller having machine readable code including instructions for operating the gas inlet to introduce dopant precursor into the reaction chamber so that it is adsorbed, and instructions for reacting the adsorbed dopant precursor to form a film layer containing a dopant source.