Cavity-Based Diffusion Barrier for Lateral Dopant Control
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Solution Overview
Problem
Diffusion of dopant atoms in integrated circuit structures leads to adverse effects on electrical characteristics, such as shifted N+/P+ junctions and increased sub-threshold leakage, which existing methods like shallower implants and reduced dopant doses fail to fully mitigate without introducing additional issues like gate-induced drain leakage and dopant activation problems.
Innovation Solution
Formation of a diffusion barrier with cavities in the polysilicon layer or substrate to reduce the diffusion of elements between regions, achieved by implanting a gas such as helium and subsequent annealing to create barriers that limit dopant diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If shallower n+ pre-doped implant and smaller N+ implanted area are adopted, then lateral diffusion of dopant is reduced, but substantial diffusion still occurs during subsequent thermal processing
Solution Approach 1:
A diffusion barrier is formed in the polysilicon layer before dopant implantation occurs. This preliminary barrier prevents dopant atoms from diffusing laterally during subsequent thermal processing steps, eliminating the need to rely on shallower implants or smaller implanted areas to control diffusion.
Solution Approach 2:
The diffusion barrier acts as an intermediary layer between the dopant source (n+ pre-doped region) and the channel region. This intermediate structure blocks the harmful lateral diffusion of dopant atoms while allowing the device to function normally, resolving the contradiction between maintaining electrical characteristics and preventing dopant migration.
2Reliability
If reduced dose of dopant is applied when forming halo region, then diffusion into channel region is reduced, but gate induced drain leakage and lack of dopant activation occur
Solution Approach 1:
The diffusion barrier is formed before halo region dopant implantation. This allows the halo region to be doped with sufficient dopant dose to ensure proper dopant activation and eliminate GIDL issues, while the barrier simultaneously prevents this dopant from diffusing into the channel region and affecting threshold voltage.
Solution Approach 2:
The diffusion barrier serves as a mediator that decouples the halo region doping process from the channel region. This enables independent optimization of halo region dopant dose without compromising channel electrical characteristics, resolving the contradiction between adequate dopant activation and threshold voltage stability.
3Manufacturing precision
If lower temperature is employed in rapid thermal annealing, then dopant diffusion is reduced, but dopant activation is insufficient
Solution Approach 1:
The diffusion barrier is formed in advance before the rapid thermal annealing process. This preliminary barrier enables the use of higher annealing temperatures that provide sufficient dopant activation, while the barrier prevents the thermally-induced dopant diffusion that would otherwise occur at these temperatures.
Solution Approach 2:
The diffusion barrier mediates between the requirements for high-temperature annealing (for dopant activation) and low-temperature processing (to prevent diffusion). By introducing this intermediate structure, the system can undergo high-temperature annealing to activate dopant without suffering from harmful lateral diffusion, resolving the contradiction between activation and diffusion control.
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
The diffusion barriers effectively reduce dopant diffusion, improving the electrical properties of transistor devices by minimizing the degradation of device performance and preventing issues like gate-induced drain leakage.
Implementation Method 1
Diffusion of dopant atoms and other atoms in integrated circuit (IC) structures is responsible for a number of problems
Implementation Method 2
achieved by implanting a gas such as helium and subsequent annealing to create barriers
Implementation Method 3
subsequent annealing to create barriers that limit dopant diffusion
Data Source
AI summary
A method of forming a device is presented. The method includes providing a structure having first and second regions. A diffusion barrier is formed between at least a portion of the first and second regions. The diffusion barrier comprises cavities that reduce diffusion of elements between the first and second regions.