FinFET Doping via Solid Phase Diffusion

Solution Overview

Problem

The manufacture of FinFET devices faces challenges in achieving uniform dopant concentrations along the vertical length of high-aspect-ratio fins, leading to variations in mobility and leakage current due to limitations in dopant implantation processes.

Innovation Solution

The method involves forming first and second dopant layers with specific concentration profiles over the fins, followed by solid phase diffusion to achieve uniform dopant distribution within the non-tip portions of the fins, eliminating the need for ion implantation and enhancing control over structural dimensions affecting resistance and mobility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If dopant implantation is used to form anti-punch through regions in FinFET fins, then dopant regions can be created, but the dopant concentration varies along the vertical length of the fins due to high aspect ratio, adversely affecting mobility and leakage current

Engineering Contradiction:

Improvedopant concentration uniformityVSAvoidmobility and leakage current performance

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The patent replaces the mechanical ion implantation process with a chemical diffusion process. Instead of physically implanting dopants through high-energy ion bombardment, the invention uses solid-phase diffusion where dopants are introduced via a dopant source layer that chemically diffuses into the fin structure during thermal processing. This substitution eliminates the angle-dependent penetration issues inherent in mechanical implantation methods.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the fundamental process parameters from ion implantation (energy, angle, dose) to diffusion-controlled parameters (temperature, time, dopant source concentration). By controlling the thermal diffusion process, uniform dopant distribution along the vertical fin length is achieved, as diffusion naturally progresses perpendicular to the surface regardless of fin aspect ratio, thereby improving both manufacturing precision and device performance.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If maximum attainable implant angle is used for dopant implantation in high aspect ratio fins, then some dopant regions are formed, but dopant concentration still varies along the vertical length, limiting process effectiveness

Engineering Contradiction:

Improvedopant region formation capabilityVSAvoiddopant concentration uniformity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent replaces the mechanical ion implantation process with a chemical diffusion process. Instead of physically implanting dopants through high-energy ion bombardment, the invention uses solid-phase diffusion where dopants are introduced via a dopant source layer that chemically diffuses into the fin structure during thermal processing. This substitution eliminates the angle-dependent penetration issues inherent in mechanical implantation methods.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the fundamental process parameters from ion implantation (energy, angle, dose) to diffusion-controlled parameters (temperature, time, dopant source concentration). By controlling the thermal diffusion process, uniform dopant distribution along the vertical fin length is achieved, as diffusion naturally progresses perpendicular to the surface regardless of fin aspect ratio, thereby improving both manufacturing precision and device performance.

Inventive Principle:

Principle #35Parameter changes

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 improved uniformity of dopant concentrations, reduced resistance, and increased mobility by tuning structural dimensions, allowing for better control over FinFET performance without the limitations of traditional implantation methods.

Implementation Method 1

followed by solid phase diffusion to achieve uniform dopant distribution within the non-tip portions of the fins

Methodology Applied

Scientific EffectSolid phase diffusion: Diffusion

Data Source

PatentUS9659776B2Doping for FinFET

Publication Date: 2017.05.23 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

First and second fins are formed extending from a substrate. A first layer is formed over the first fin. The first layer comprises a first dopant. A portion of the first layer is removed from a tip portion of the first fin. A second layer is formed over the second fin. The second layer comprises a second dopant. One of the first and second dopants is a p-type dopant, and the other of the first and second dopants is an n-type dopant. A portion of the second layer is removed from a tip portion of the second fin. A solid phase diffusion process is performed to diffuse the first dopant into a non-tip portion of the first fin, and to diffuse the second dopant into a non-tip portion of the second fin.