Low-Temperature FinFET Doping via Inclined Ion Implantation
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Solution Overview
Problem
Current methods for doping and activating N- or P-type dopants in finFET transistors face challenges, particularly at low temperatures, as they result in incomplete recrystallization and degradation of lower layer transistors due to heat treatments, making it difficult to achieve high-quality transistors for 3D circuits.
Innovation Solution
A method involving inclined ion implantation and subsequent recrystallization annealing on both sides of the fin, allowing for complete recrystallization and dopant activation without high-temperature processes, which includes rendering amorphous and doping portions of the fin using beams directed at specific angles, followed by solid-phase epitaxial recrystallization at temperatures below 600°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high temperature heat treatment is used for doping and activation, then dopant activation is improved, but lower layer transistors are degraded by heat
Solution Approach 1:
The patent utilizes solid-phase epitaxial recrystallization, a phase transition process, to activate dopants at low temperatures. By transforming the amorphous silicon region back into crystalline silicon through controlled recrystallization, the dopants are activated without requiring high-temperature thermal processes that would damage lower layer transistors
Solution Approach 2:
The patent replaces thermal diffusion mechanisms with ion implantation followed by solid-phase recrystallization. This substitution allows dopant introduction and activation without relying on high-temperature thermal fields, thereby avoiding heat-induced degradation of underlying transistor structures
2Ease of manufacture
If diffusion mechanism is used for doping, then doping is achieved, but temperature constraint below 600°C cannot be respected
Solution Approach 1:
The patent replaces thermal diffusion with ion implantation followed by solid-phase epitaxial recrystallization. This mechanism substitution enables doping at temperatures below 600°C by using physical ion bombardment for dopant introduction and phase transition for activation, rather than thermally-driven diffusion
3Temperature
If vertical implantation is used for low-temperature doping, then doping is achieved, but recrystallization is incomplete and facets form
Solution Approach 1:
The patent introduces inclined implantation angles (non-vertical) to enable dopant penetration and amorphization from the side of the fin structure. This dimensional change in implantation direction allows the recrystallization front to propagate completely through the fin without forming facets, achieving high-quality recrystallization at low temperatures
4Object-affected harmful factors
If low temperature process is used, then heat degradation is reduced, but doping and activation effectiveness decreases
Solution Approach 1:
The patent employs solid-phase epitaxial recrystallization, a phase transition from amorphous to crystalline silicon, to achieve effective dopant activation at low temperatures. This phase transition mechanism provides sufficient activation effectiveness without requiring high-temperature processes that would cause heat degradation
Solution Approach 2:
The patent changes the physical state parameter of the silicon material by creating an amorphous region through ion implantation, then utilizing solid-phase recrystallization to restore the crystalline structure with activated dopants. This parameter change enables effective doping and activation at low temperatures
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 and activation of finFET transistors at low temperatures, reducing crystal defects and allowing for more complete recrystallization, suitable for 3D circuits with abrupt junctions and improved transistor performance.
Implementation Method 1
rendering amorphous and doping a first portion of a fin made of crystalline semiconductor material using at least a first inclined implantation by means of a beam directed towards a first lateral face of the fin
Implementation Method 2
performing at least one recrystallization annealing of said first portion
Implementation Method 3
performing at least one recrystallization annealing of said first portion
Data Source
Figure 1A~2B
Figure 3A~3C
Figure 4A~4D
AI summary
Fabrication of a FinFET transistor device comprising the steps of: a) making amorphous and doping a first portion (31) of a semiconductor fin (24) by means of an inclined beam directed towards a first lateral face (24a) of the fin, while keeping a first crystalline semiconductor block (33) against a second lateral face of the fin (24b), then b) performing at least one recrystallization anneal of said first portion, then c) making amorphous and doping a second portion of the fin (24) by means of an inclined beam directed towards the second lateral face (24b) of the fin, while keeping a second crystalline semiconductor block against said first lateral face (24a) of the fin, then d) performing at least one recrystallization anneal of the second portion (35).