AlOx钝化非晶InGaZnO薄膜晶体管的高温稳定研究

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本文主要探讨了采用AlOx层钝化的非晶态Indium-Gallium-Zinc-Oxide (a-IGZO)薄膜晶体管（thin-film transistor, TFT）的热稳定性。作者们在国家工程实验室——上海交通大学电子工程系的 TFT-LCD 材料与技术国家重点实验室进行了一系列实验，通过对a-IGZO TFT 的研究，他们着重考察了不同厚度的AlOx钝化层（0-60纳米）以及测量温度范围（298-573K）对器件性能的影响。实验结果显示，在高温下，a-IGZO TFT 的阈值电压(VT)会呈现出负向漂移，这是由于在高温下发生了内激发（intrinsic excitation），即由于热能促使载流子（空穴和电子）的活性增强，导致电流增益降低和阈值电压上升。这种现象对于电子设备的可靠性和寿命具有重要意义，因为在许多应用中，如显示器、传感器和功率器件，工作温度的稳定性和长期耐热性是关键性能指标。通过调控AlOx钝化层的厚度，研究者试图找到最佳的保护层参数，以减小温度对器件性能的负面影响。理论上，一个适当的钝化层可以有效地阻挡或减少热载流子的迁移，从而提高TFT在高温环境下的稳定性和一致性。然而，实际效果可能会受到材料生长过程、制备工艺以及基底材料等因素的影响。此外，该研究还可能涉及到对温度依赖性的机理分析，包括热激发载流子的迁移率变化、氧化铝钝化层的热膨胀系数与a-IGZO材料之间的匹配问题，以及可能的界面缺陷或氧化行为。这些研究对于优化a-IGZO TFT的热稳定性设计和制造过程至关重要，有助于提升下一代微电子器件在高温条件下的性能表现。本文为理解和改善非晶InGaZnO薄膜晶体管的热稳定性提供了一种方法，通过精确控制钝化层的特性，以期达到在高温环境下保持稳定性能的目标，这对于开发能在恶劣工作环境中的高可靠性电子设备具有重要的实践意义。

Thermal stability of amorphous InGaZnO thin ﬁlm transistors

passivated by AlO

layers

Zhe Hu, Daxiang Zhou, Ling Xu, Qi Wu, Haiting Xie, Chengyuan Dong

⇑

National Engineering Lab for TFT-LCD Materials and Technologies, Department of Electronic Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

article info

Article history:

Received 12 July 2014

Received in revised form 12 October 2014

Accepted 28 October 2014

The review of this paper was arranged by

Prof. S. Cristoloveanu

Keywords:

Amorphous indium gallium zinc oxide

(a-IGZO)

Thin ﬁlm transistor (TFT)

Thermal stability

Passivation-layer

Intrinsic excitation

abstract

Thermal stability of amorphous InGaZnO thin ﬁlm transistors (a-IGZO TFTs) passivated by AlO

layers was

investigated in this paper. The passivation-layer thickness (0–60 nm) and measurement temperature

(298–573 K) were intentionally controlled to study the temperature dependent performance of a-IGZO

TFTs with sputtered AlO

passivation-layers. Generally, there was a negative shift in threshold voltage

under higher temperatures, which was due to thermally excited carriers through intrinsic excitation

and oxygen vacancy formation. A qualitative model was proposed to effectively ascertain the aforemen-

tioned two physical mechanisms. With passivation-layer thickness decreasing oxygen vacancy formation

became more and more evident while intrinsic excitation could apparently worsen the characteristics of

a-IGZO TFTs under the temperature higher than 473 K. In addition, the ‘‘passivation-layer thickness

effect’’ for thermal stability of a-IGZO TFTs was theoretically explained by the variation of defect forma-

tion energy with the device passivation-layer thickness.

1. Introduction

Transparent amorphous oxide thin ﬁlm transistors (TFTs) have

been attracting considerable attention for applications in mobile

displays, televisions, and other consumer electronics. In particular,

amorphous In–Ga–Zn–O (a-IGZO) TFTs have been regarded as one

of the most promising candidates for the addressing devices in

next-generation ﬂat-panel displays including active-matrix liquid

crystal display (AMLCD) and active-matrix organic light-emitting

diode (AMOLED) due to their outstanding features such as high

ﬁeld-effect mobility, low-temperature fabrication ability and good

large-area uniformity [1–5]. However, some critical issues such as

environmental instabilities of a-IGZO TFTs still remain to be solved

[6–10]. Especially, the characteristic variations of a-IGZO TFTs,

such as the threshold voltage (V

) variation, often occur under

temperature stresses and hence seriously limit the actual applica-

tions of this novel technology [6]. So far several reports about the

temperature inﬂuence on transistor characteristics of a-IGZO TFTs

have been published [7–9]. For the n-type oxide semiconductors, it

is well known that oxygen vacancy (V

) plays an important role in

the electrical performances of the thin ﬁlms and the corresponding

TFT devices. In fact, V

s in oxide semiconductors create additional

states near the conduction band and hence generate carriers, as

may induce a negative shift in the device threshold voltage [8].

Therefore, any factors inﬂuencing the concentration of V

s in oxide

semiconductors might lead to instabilities of the oxide thin ﬁlm

transistors. Naturally the free carriers in a-IGZO mainly originate

from point defects (oxygen vacancies) which closely relate the

temperature-dependent characteristics of oxide thin ﬁlm materials

and devices [10–12]. Therefore it is important to investigate how

the ambient temperature affects the concentration of point defects

in a-IGZO as well as the performance of the corresponding TFT

devices. On the other side, passivation layers are often used to

improve the stability of oxide TFTs by isolating the ambience and

the device back-channels [13–16]. However, how passivation lay-

ers exactly affect the thermal stability of a-IGZO TFTs has not yet

been covered, although it is apparently the essential knowledge

for the mass production of this novel technology.

In this article, the temperature dependence of the electrical char-

acteristics of a-IGZO TFTs with variously thick AlO

passivation-lay-

ers was investigated. A qualitative model was proposed to ascertain

the two physical mechanisms relating thermal stability of a-IGZO

TFTs with passivation layers. We believe the experimental and the-

oretical results in this paper could beneﬁt application of a-IGZO

TFTs, especially for choice of passivation-layers and working tem-

peratures in mass production.

http://dx.doi.org/10.1016/j.sse.2014.10.012

⇑

Corresponding author at: 800 DongChuan Rd., Shanghai 200240, China.

Tel.: +86 21 34207894.

E-mail address: cydong@sjtu.edu.cn (C. Dong).

Solid-State Electronics 104 (2015) 39–43

Contents lists available at ScienceDirect

Solid-State Electronics

journal homepage: www.elsevier.com/locate/sse

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