ALD Doping Substrates with Conformal Dielectric Annealing
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Solution Overview
Problem
Current semiconductor doping methods, such as plasma immersion ion implantation, involve harsh conditions that can damage substrates and fail to provide conformal and consistent results, especially for high aspect ratio features like FinFET transistors.
Innovation Solution
A method involving atomic layer deposition of dopants followed by a dielectric layer and annealing to diffuse dopants into the substrate, allowing for precise control of dopant dosage and distribution without substrate damage, using techniques like ALD or PEALD, and selecting suitable dielectric materials like SiN, SiO2, or Al2O3, with optional implantation of silicon or argon to enhance dopant incorporation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If plasma immersion ion implantation is used to achieve desired ion implantation depth profile, then ion energy and implant dose rate are improved, but substrate damage occurs due to harsh conditions
Solution Approach 1:
A dielectric layer is introduced as an intermediary between the dopant source and the substrate. The dopants are first deposited onto the dielectric layer, which then serves as a temporary holding layer during annealing. This mediator allows dopant diffusion into the substrate without requiring direct harsh plasma or ion implantation conditions, thereby achieving the desired depth profile while minimizing substrate damage.
Solution Approach 2:
The patent replaces the mechanical/physical impact mechanism of ion implantation with a thermal diffusion mechanism. Instead of using high-energy ions to force dopants into the substrate (which causes damage), the method uses thermal energy during annealing to enable controlled diffusion of dopants through the dielectric layer and into the substrate, achieving the same doping effect without the harmful mechanical impact.
2Device complexity
If conventional doping methods are used, then doping process is simplified, but conformal and consistent results are not achieved in high aspect ratio features
Solution Approach 1:
The dielectric layer is deposited conformally over the entire substrate surface, including all high aspect ratio features such as FinFET structures. This creates a uniform local environment across different geometries, ensuring that dopants are distributed evenly and consistently throughout all features regardless of their shape or aspect ratio, thereby achieving conformal doping results.
Solution Approach 2:
The patent transitions from direct surface doping to a multi-layer approach where dopants are deposited on a dielectric layer that conforms to three-dimensional features. This adds a dimensional aspect to the doping process, allowing uniform dopant distribution across complex geometries by utilizing the dielectric layer as a conformal template that follows the substrate's topography.
3Length of stationary object
If high RF bias voltage is applied to achieve desired ion energy, then ion implantation depth is improved, but substrate damage increases due to very high voltage conditions
Solution Approach 1:
The patent replaces the high-voltage electrical field mechanism with a thermal field mechanism. Instead of using very high RF bias voltage (10-20 kV) to drive ions into the substrate, the method uses thermal energy during annealing to enable dopant diffusion to the desired depth, eliminating the harmful high-voltage conditions while achieving comparable or superior implantation depth control.
Solution Approach 2:
The patent changes the fundamental parameter used to control dopant depth from electrical field strength (voltage) to thermal energy (temperature and time). By controlling annealing temperature and duration, the desired implantation depth is achieved through controlled diffusion rather than high-energy impact, fundamentally changing the process parameter from electrical to thermal to eliminate substrate damage.
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 conformal doping with high activation and minimal substrate damage, achieving precise dopant distribution and concentration, particularly suitable for FinFET transistors and other compound semiconductors, while avoiding the limitations of conventional ion implantation.
Implementation Method 1
annealing the dielectric layer to diffuse the dopants into the substrate
Implementation Method 2
depositing a layer of dopants onto the substrate, the layer of dopants having a shape conforming to the at least one feature
Data Source
AI summary
Provided are methods of doping substrates and making doped semiconductor features. An exemplary method includes providing a substrate having at least one feature having an aspect ratio; depositing a layer of dopants onto the substrate, the layer of dopants having a shape conforming to the at least one feature. A dielectric layer is deposited onto the layer of dopants, the dielectric layer having a shape conforming to the layer of dopants. The dielectric layer is annealed to diffuse the dopants into the substrate.