a-IGZO Memory Channel Fluorine Doping for Stable Normally-Off Operation
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Solution Overview
Problem
Oxide semiconductors, such as a-IGZO, suffer from low stability under external stress and a normally-on characteristic due to negative threshold voltage, hindering their performance in memory devices.
Innovation Solution
A manufacturing method involving the formation of an amorphous indium-gallium-zinc-oxide (a-IGZO) thin film with fluorine doping, utilizing initiated chemical vapor deposition (iCVD) and atomic layer deposition (ALD) processes to enhance stability and mobility, including a polymer layer with perfluorodecanoic acid (PFDA) and an aluminum oxide (Al2O3) layer to stabilize fluorine doping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If oxide semiconductor (a-IGZO) is used to improve mobility compared to hydrogenated amorphous silicon, then mobility characteristics are improved, but stability under external stress deteriorates and negative threshold voltage causes normally-on characteristic
Solution Approach 1:
The patent changes the chemical composition parameters of the oxide semiconductor by introducing fluorine doping into the a-IGZO layer. This parameter change transforms the threshold voltage from negative to positive, achieving normally-off characteristic while maintaining high mobility. The fluorine doping concentration is controlled to optimize both mobility and stability characteristics.
Solution Approach 2:
The patent creates a composite structure by combining a-IGZO with fluorine-containing polymer layers (such as PFDA) and aluminum oxide layers. This composite approach allows the oxide semiconductor to benefit from both the high mobility of a-IGZO and the stability provided by the fluorine doping and protective oxide layers.
2Reliability
If fluorine doping is introduced to improve stability and achieve positive threshold voltage, then reliability is improved, but manufacturing process complexity increases
Solution Approach 1:
The patent uses a fluorine-containing polymer layer (such as perfluorodecanoic acid or PFDA) as an intermediary material to deliver fluorine to the a-IGZO layer. This intermediary approach simplifies the manufacturing process compared to direct fluorine gas doping, as the polymer can be deposited using standard spin-coating or iCVD techniques followed by thermal treatment to release fluorine.
Solution Approach 2:
The fluorine-containing polymer layer is deposited in advance before the final oxide semiconductor layer formation. This preliminary action allows fluorine to be pre-positioned in the structure, and subsequent thermal treatment releases the fluorine into the a-IGZO layer, achieving doping without complex in-situ doping equipment.
3Manufacturing precision
If multiple layers (polymer layer with PFDA and Al2O3 layer) are deposited to stabilize fluorine doping, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent applies different materials with specific local functions: the fluorine-containing polymer layer provides fluorine source for doping, while the aluminum oxide layer provides protective and stabilizing properties. Each layer has optimized thickness and composition tailored to its specific function, achieving precise control over fluorine doping profile and stability.
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 method improves the threshold voltage to a positive value, achieving a normally-off characteristic and increased on-current performance, while reducing oxygen vacancies and passivating bulk traps.
Implementation Method 1
performing a drive-in process of applying heat to the oxide channel
Implementation Method 2
depositing an aluminum oxide (Al2O3) layer on the polymer layer
Implementation Method 3
the polymer layer containing the perfluorodecanoic acid may be deposited by an initiated chemical vapor deposition (iCVD) process
Implementation Method 4
the aluminum oxide layer may be deposited by an atomic layer deposition (ALD) process
Implementation Method 5
performing a drive-in process of applying heat to the oxide channel
Data Source
AI summary
The present disclosure relates to an oxide semiconductor memory device and a manufacturing method thereof, and more particularly, to an oxide semiconductor memory device forming an amorphous indium-gallium-zinc-oxide (hereinafter, referred to as a-IGZO) thin film and a manufacturing method thereof. The present disclosure is to solve a problem of oxide semiconductor forming an a-IGZO thin film having a negative threshold voltage and improve mobility characteristics.