FinFET Anti-Punchthrough Doping Without Ion Implantation Damage
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Solution Overview
Problem
Existing methods for manufacturing fin field effect transistors suffer from ion implantation damage, which degrades carrier mobility and affects the performance of the device by causing punchthrough and uneven doping distribution in the anti-punchthrough layer.
Innovation Solution
A method involving solid-phase source doping to form a heavily-doped anti-punchthrough layer at the bottom of the channel layer, using a doped dielectric layer to diffuse dopants into the first section of the fin, without affecting the carrier mobility, by forming sacrificial sidewalls and removing them after doping, and then etching to create the bottom portion of the fin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion implantation is used to form the anti-punchthrough layer, then the doping process can be completed, but ion implantation damage occurs which degrades carrier mobility
Solution Approach 1:
The patent replaces the mechanical ion implantation process with a chemical diffusion process. Instead of physically implanting ions into the semiconductor substrate, the dopants are introduced through a doped dielectric layer and diffuse into the fin structure during thermal processing. This substitution eliminates the mechanical damage caused by ion bombardment while achieving the desired doping distribution in the anti-punchthrough layer.
Solution Approach 2:
The patent introduces a doped dielectric layer as an intermediary medium to transfer dopants to the fin structure. The dopants are first incorporated into the dielectric layer, which then serves as a source for controlled diffusion into the anti-punchthrough region. This intermediary approach allows for precise doping without direct ion implantation damage to the channel.
2Quantity of substance
If ion implantation is used to form the anti-punchthrough layer, then doping can be achieved, but uneven doping distribution and punchthrough occur
Solution Approach 1:
The patent changes the doping mechanism from ion implantation to thermal diffusion, fundamentally altering the process parameters. The diffusion process is controlled by temperature, time, and the composition of the doped dielectric layer, allowing for more uniform dopant distribution. The dopant concentration profile is determined by the diffusion parameters rather than implantation energy and dose, achieving better uniformity and preventing punchthrough.
3Shape
If the fin structure is etched to form the channel, then the transistor geometry is created, but the bottom portion is difficult to control for optimal doping
Solution Approach 1:
The patent performs preliminary doping by forming a doped dielectric layer on the fin structure before completing the fin etching process. The dopants are introduced into the bottom portion of the fin during this intermediate stage, allowing precise control over the anti-punchthrough layer formation. The subsequent etching steps then define the final fin geometry while preserving the previously established doping profile.
Solution Approach 2:
The patent segments the fin formation process into distinct stages: first forming the fin structure up to a certain depth, then adding the doped dielectric layer for anti-punchthrough doping, and finally completing the etching to create the channel. This segmentation allows independent optimization of the doping process and the geometric formation, achieving both precise doping control and accurate fin geometry.
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 results in a damage-free anti-punchthrough layer that enhances carrier mobility and improves device performance by preventing punchthrough and maintaining optimal doping levels.
Implementation Method 1
perform a dopant drive process to diffuse dopants in the doped dielectric layer into the first section to achieve doping of the first section
Data Source
AI summary
The present application discloses a method for manufacturing fin field effect transistors, comprising: step 1: performing first time etching to form top portions of fins, each of the top portions is divided into a first section and a second section; step 2: forming sacrificial sidewalls on the side surfaces of the second section but not on the side surfaces of the first section; step 3: forming a doped dielectric layer to coat the side surfaces of the first section; step 4: performing a dopant drive process to diffuse dopants of the doped dielectric layer into the first section; step 5: removing the doped dielectric layer and the sacrificial sidewalls; step 6: performing second time etching to form bottom portions of the fins; and step 7: forming a dielectric isolation layer between adjacent fins.