超薄ITO透明導電膜應用在觸控面板之研究

Reliability and Stability in Electrical Properties of Ultra-thin ITO for Touch Panel Application

蔡宗典(Tsung-tien Tsai)

指導教授 ： 李正中

國立中央大學/理學院/光電科學研究所碩士在職專班/碩士(2008年)

摘要

本文使用直流磁控濺鍍在玻璃基板表面沉積ITO透明導電膜，研究超薄的ITO膜厚從2nm到100nm的電阻率、穿透率、微觀結構、表面粗糙度等薄膜特性，以及探討在觸控面板上的環境耐久性與ITO鍍膜製程的關係。

氧化銦錫(ITO)在可見光區擁有高穿透率以及低電阻率的透明導電膜，通常應用在平面顯示器的電阻率約2E-4Ωcm。但是應用在觸控面板的透明導電膜需要較高的電阻率(常見的面阻抗約300 ~1000Ω)，為了得到較高的面電阻，透明導電膜的膜厚需要變得很薄，而膜厚太薄的薄膜會產生許多問題，包括電性的不穩定、面阻抗的不均勻、環境測試能力變差，本論文即要探討研究此改善方向，先針對ITO膜厚對於其結構與光電特性之研究，並且透過調整反應氣體O2的含量以及濺鍍功率密度來改善ITO薄膜特性，以符合觸控面板的透明導電膜之要求。

實驗結果可知，ITO薄膜在膜厚為8nm、濺鍍功率密度為0.38 w/cm2、氧氣含量2.6%，可達到穿透率大於91%，面阻抗值為500Ω/□之ITO導電玻璃，並可符合觸控面板所要求的耐高溫測驗(160℃，30分鐘)、恆溫恆濕測驗(60℃，90%相對濕度，240小時)、以及耐鹼測驗(NaOH 5%，10分鐘)。

關鍵字

觸控面板 ； 氧化銦錫 ； 濺鍍

並列摘要

This study uses DC magnetron sputtering to deposit indium tin oxide(ITO) thin film on a soda-lime glass surface to study thin-film properties of an ultra-thin ITO that have a thin-film thickness of 2nm-100nm,Resistivity, transmittance, thin-film structure morphology and surface roughness were determined. This study also examines the relationship between ITO coating processes and reliability testing.

Indium tin oxide is a transparent conducting thin film that has a highly visible transmission and low resistivity. In Flat Panel Display applications, ITO resistivity is typically 2E-4Ωcm. However, in the touch panel applications, the transparent conductivity oxide (TCO) film requires high resistivity (sheet resistance is approximately 300-1000Ω). To increase sheet resistance, the TCO film should be thin; however, this has many disadvantages, including unstable electrical properties, non-uniform sheet resistance, and poor reliability and durability. This study attempts overcome these problems. This study investigated the effects of various ITO thicknesses on thin-film structure and photoelectric properties, and then fine tuned optimal oxygen gas flow and deposition power density to improve ITO thin-film properties, such that they meet touch panel requirements.

Experiments results demonstrate that an ITO thickness of 8nm was deposited using a coating process with a power density of 0.38 w/cm2 and oxygen gas flow of 2.6%, that has 91% transmittance and a sheet resistance of 500Ω/□, the ITO thin film also passed all reliability tests, including heat testing (160℃, 30 mins), humidity testing (60℃, 90%RH, 240hrs) and alkaline testing (NaOH 5%, 10mins).

並列關鍵字

sputter coating ； Touch Panel ； Indium Tin Oxide

參考文獻

[1] M.Bender, W.Seelig, C.Daube, H.Frankenberger, B.Ocker, J.Stollenwerk “ Dependence of oxygen flow on optical and electrical properties of DC-magnetron”, Thin solid Films 326.72-77, 1998.

[2] C.Choi., W.J. Lee, J.K., S.O. Jung, W.J. Lee, W.S. Kim, S.J. Kim, C. Yoon“ Effects of oxygen partial pressure on the microstructure and electrical properties of indium tin oxide film prepared by d.c. magnetron sputtering”, Thin solid Films 258.274-278, 1995.

[3] A.N.H. Al-Ajili, S.C. Bayliss“ A study of the optical, electrical and structural properties of reactively sputtered InOx and ITOx thin films”, Thin solid Films 305, 116-123, 1997.

[4] S. K. Choi and J. I. Lee “Effect of film density on electrical properties of indium tin oxide films deposited by dc magnetron reactive sputtering”, J. Vac. Sci. Technol. A, Vol. 19, 2043-2047, 2001.

[7] M. Bender, J. Trube, J. Stollenwerk “Deposition of transparent and conducting indium tin oxide films by the r.f.-superimposed DC sputtering technology”, Thin solid films 354 .100-105, 1999.