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Zinc Oxide Thin-Film Transistors for 3D Microelectronic Applications.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Zinc Oxide Thin-Film Transistors for 3D Microelectronic Applications./
Author:	Yoo, Sang Ha.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2021,
Description:	145 p.
Notes:	Source: Dissertations Abstracts International, Volume: 83-03, Section: B.
Contained By:	Dissertations Abstracts International83-03B.
Subject:	Silicon. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28841638
ISBN:	9798460448333

Zinc Oxide Thin-Film Transistors for 3D Microelectronic Applications.
Yoo, Sang Ha.

Zinc Oxide Thin-Film Transistors for 3D Microelectronic Applications. - Ann Arbor : ProQuest Dissertations & Theses, 2021 - 145 p.

Source: Dissertations Abstracts International, Volume: 83-03, Section: B.

Thesis (Ph.D.)--The Pennsylvania State University, 2021.

This item must not be sold to any third party vendors.

As the current semiconductor industry trend deviates from Moore's Law due to quantum limits discovered upon further scaling of technology nodes, efforts are being put into three-dimensional (3D) stacking of semiconductor devices in integrated circuits (ICs). Since its conduction band pathway arises from its spherically shaped s-orbital, zinc oxide (ZnO) is a promising material for technological advancement towards 3D-stacked devices since it can theoretically retain its bulk mobility even if it is processed at a low temperature. Plasma-enhanced atomic layer deposition (PEALD) system using weak oxidants was utilized to deposit ZnO at a low temperature (< 200 °C), and ZnO thin-film transistors (TFTs) were fabricated based on this system for this study. This dissertation presents efforts to develop ZnO TFTs that are suitable for 3D electronics applications, focusing on high mobility, high current, and scalability aspects of the device. The relationship between the ZnO TFT mobility and the morphology of PEALD ZnO films is studied with emphasis on the grain size variation of the ZnO films. For the nanocrystalline PEALD ZnO films, no direct relationship between grain size and mobility was discovered from the study. On the other hand, a simple N2O-based PEALD Al2O3 passivation layer that enhances the performance of ZnO TFTs by an order of magnitude is developed. The passivated ZnO TFTs exhibit field-effect mobility >90 cm2/Vs and drive current >450 mA/mm. Multiple mobility extraction methods confirm that the high mobility value calculated for the passivated TFTs is not from measurement artifacts. The high current and mobility of the N2O PEALD passivated ZnO TFTs remain even when the passivation layer is selectively removed. The cause of the mobility boost is postulated to be hydrogen incorporation during the passivation process. The high performance of these devices is of interest for 3D ICs and other applications. Metals of different reactivity and work function are explored to overcome the Schottky barrier present in ZnO TFTs. Oxygen vacancies and zinc interstitials generated from the reaction between contact metal and ZnO semiconductors are believed to serve as the source of increased charge carriers to mimic a doping effect at TFT contacts. In addition, doped contact ZnO TFTs are demonstrated as well. We use PEALD ZnO films as the active layer and ALD ZnO films as the doped layer. The fabrication process of PEALD ZnO TFTs with ALD ZnO doped layer resembles that of back-channel-etched a-Si: H TFTs. An acetic acid-based ZnO etchant is used to controllably back etch the channel layer at a rate of 2 nm/sec to etch away the conductive ALD ZnO layer. The fabricated devices exhibit less dominance by the Schottky barrier at contacts. Ferroelectric field-effect transistors (FeFET) using low-temperature processed boron-doped aluminum nitride (Al1-xBxN; AlBN for simplicity) as the gate dielectric are also developed to serve as memory devices combined with ZnO TFT logic devices. With the help of a stable PEALD Al2O3 layer to prevent gate leakage, fabricated ZnO-AlBN FeFETs demonstrated counter-clockwise hysteresis, which is one of the indications of ferroelectricity present in the device. Double-gated ZnO-AlBN FeFETs are also fabricated to further establish that the devices exhibit polarization behavior with known field line terminations. ZnO TFTs and AlBN FeFETs are of interest to the future 3D microelectronics and ICs.

ISBN: 9798460448333Subjects--Topical Terms:

669429
Silicon.
Subjects--Index Terms:

Zinc oxide

Zinc Oxide Thin-Film Transistors for 3D Microelectronic Applications.
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245 1 0 $a Zinc Oxide Thin-Film Transistors for 3D Microelectronic Applications.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2021
300 $a 145 p.
500 $a Source: Dissertations Abstracts International, Volume: 83-03, Section: B.
500 $a Advisor: Jackson, Tom.
502 $a Thesis (Ph.D.)--The Pennsylvania State University, 2021.
506 $a This item must not be sold to any third party vendors.
520 $a As the current semiconductor industry trend deviates from Moore's Law due to quantum limits discovered upon further scaling of technology nodes, efforts are being put into three-dimensional (3D) stacking of semiconductor devices in integrated circuits (ICs). Since its conduction band pathway arises from its spherically shaped s-orbital, zinc oxide (ZnO) is a promising material for technological advancement towards 3D-stacked devices since it can theoretically retain its bulk mobility even if it is processed at a low temperature. Plasma-enhanced atomic layer deposition (PEALD) system using weak oxidants was utilized to deposit ZnO at a low temperature (< 200 °C), and ZnO thin-film transistors (TFTs) were fabricated based on this system for this study. This dissertation presents efforts to develop ZnO TFTs that are suitable for 3D electronics applications, focusing on high mobility, high current, and scalability aspects of the device. The relationship between the ZnO TFT mobility and the morphology of PEALD ZnO films is studied with emphasis on the grain size variation of the ZnO films. For the nanocrystalline PEALD ZnO films, no direct relationship between grain size and mobility was discovered from the study. On the other hand, a simple N2O-based PEALD Al2O3 passivation layer that enhances the performance of ZnO TFTs by an order of magnitude is developed. The passivated ZnO TFTs exhibit field-effect mobility >90 cm2/Vs and drive current >450 mA/mm. Multiple mobility extraction methods confirm that the high mobility value calculated for the passivated TFTs is not from measurement artifacts. The high current and mobility of the N2O PEALD passivated ZnO TFTs remain even when the passivation layer is selectively removed. The cause of the mobility boost is postulated to be hydrogen incorporation during the passivation process. The high performance of these devices is of interest for 3D ICs and other applications. Metals of different reactivity and work function are explored to overcome the Schottky barrier present in ZnO TFTs. Oxygen vacancies and zinc interstitials generated from the reaction between contact metal and ZnO semiconductors are believed to serve as the source of increased charge carriers to mimic a doping effect at TFT contacts. In addition, doped contact ZnO TFTs are demonstrated as well. We use PEALD ZnO films as the active layer and ALD ZnO films as the doped layer. The fabrication process of PEALD ZnO TFTs with ALD ZnO doped layer resembles that of back-channel-etched a-Si: H TFTs. An acetic acid-based ZnO etchant is used to controllably back etch the channel layer at a rate of 2 nm/sec to etch away the conductive ALD ZnO layer. The fabricated devices exhibit less dominance by the Schottky barrier at contacts. Ferroelectric field-effect transistors (FeFET) using low-temperature processed boron-doped aluminum nitride (Al1-xBxN; AlBN for simplicity) as the gate dielectric are also developed to serve as memory devices combined with ZnO TFT logic devices. With the help of a stable PEALD Al2O3 layer to prevent gate leakage, fabricated ZnO-AlBN FeFETs demonstrated counter-clockwise hysteresis, which is one of the indications of ferroelectricity present in the device. Double-gated ZnO-AlBN FeFETs are also fabricated to further establish that the devices exhibit polarization behavior with known field line terminations. ZnO TFTs and AlBN FeFETs are of interest to the future 3D microelectronics and ICs.
590 $a School code: 0176.
650 4 $a Silicon. $3 669429
650 4 $a Integrated circuits. $3 584067
650 4 $a Semiconductor research. $3 3683765
650 4 $a Manufacturing. $3 3389707
650 4 $a Physics. $3 516296
650 4 $a Plasma etching. $3 712111
650 4 $a Zinc oxides. $3 3681737
650 4 $a Hydrogen. $3 580023
650 4 $a Aluminum. $3 735071
650 4 $a Photovoltaic cells. $3 604818
650 4 $a Energy. $3 876794
650 4 $a Transistors. $3 713271
650 4 $a Thin films. $3 626403
650 4 $a Annealing. $2 lcstt $3 3267268
650 4 $a Condensed matter physics. $3 3173567
650 4 $a Low temperature physics. $3 3173917
650 4 $a Electrical engineering. $3 649834
650 4 $a Chemical engineering. $3 560457
653 $a Zinc oxide
653 $a Thin films
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690 $a 0598
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690 $a 0542
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710 2 $a The Pennsylvania State University. $3 699896
773 0 $t Dissertations Abstracts International $g 83-03B.
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792 $a 2021
793 $a English
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