Nanometer-Scale Investigation of Al-Based Alloy Films for Thin-Film Transistor Liquid Crystal Display Arrays

Takatsuji, H.; Iiyori, Hideo; Tsuji, S.; Tsujimoto, K.; Kuroda, Kotaro; Saka, Hiroyasu

doi:10.1557/proc-471-99

Cited by 19 publications

(7 citation statements)

References 3 publications

(1 reference statement)

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“…Previously, the alloying of Al with such rare-earth metals had been widely studied with the aim of controlling the formation of hillocks and whiskers under thermal stressing [6,[11][12][13][14][15]. Our films were deposited by sputtering on 5-in.-square LCD-grade glass substrates.…”

Section: Preparation Of Samplesmentioning

confidence: 99%

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Aluminum-based gate structure for active-matrix liquid crystal displays

Arai¹,

Iiyori²,

Hiromasu³

et al. 1998

IBM J. Res. & Dev.

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This paper describes the development of an Al-based thin-film gate structure for use in large, high-resolution active-matrix liquid crystal displays (AMLCDs). Aluminum films are suitable for forming the data lines of such displays, but they are not suitable for forming the gate lines because of the hillock-induced shorts that can occur to overlying metal lines during the heating necessary for insulator deposition. Alloying with yttrium, gadolinium, and neodymium was examined with the aim of reducing hillock and whisker formation during such heating. Although Al films alloyed with 2 at.% of those metals exhibited low hillock densities (10-100 mm""^), the densities were not low enough for the fabrication of SXGA (1280 X 1024 pixels) panels. After investigation of several means to further reduce the formation of hillocks and whiskers, the most effective approach was found to be anodization of the Al-alloy gate lines, suitably patterned for anodization, followed by photoresist application and laser-cutting steps. Illustratively, by use of an anodized Al-Nd (2 at.%) thin-film gate structure, the shortcircuit defect rate and contact defect rate for an 11.3-in.-diagonal experimental SVGA (800 X 600 pixels) display could be effectively reduced to zero. IntroductionThin-film transistors having an inverted structure (gate beneath) have been studied extensively because of their use in active-matrix liquid crystal displays (AMLCDs) [1,2]. In the 1990s, the panel size and resolution of AMLCDs were increased dramatically, and much effort was devoted to developing low-resistivity gate lines [3-6], The aperture of displays with resolutions higher than SXGA has been significantly reduced by the use of gate alloys such as molybdenum-tantalum or molybdenum-tungsten. To achieve this, low-resistivity films are required (see Tabic 1). As shown in Figure L the use of a conventional MoW alloy with a resistivity of 16.5 /liO-cm results in an aperture ratio of less than 30% for a 12-15-in.-diagonal panel. This is unacceptable for a mobile computer display, because a small aperture requires a bright backlight and consumes a large amount of batterj' power. On the other hand, the use of an aluminum alloy film with a resistivity of 6 /j,ft-cm results in an aperture of more than 50% for a

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Section: Preparation Of Samplesmentioning

confidence: 99%

“…To reduce hillock and whisker formation, use has been made of anodization [3], capping with refractory metals [6], and alloying [8][9][10][11][12][13][14][15][16]. We have found that anodization can adequately suppress the formation of hillocks and whiskers, but it requires the use of several additional processing steps.…”

Section: Introductionmentioning

confidence: 99%

Aluminum-based gate structure for active-matrix liquid crystal displays

Arai¹,

Iiyori²,

Hiromasu³

et al. 1998

IBM J. Res. & Dev.

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“…In the past, a number of studies have focused on the binary aluminum alloys with transition elements and rare-earth elements as alloying additions for potential usage in the TFT-LCDs [6][7][8][9][10][11][12] . While some of the transition element containing binary aluminum alloys showed improved hillock resistance and low resistivity properties, they failed to offer completely hillock-free films in annealed state.…”

Section: Introductionmentioning

confidence: 99%

A combinatorial approach of developing alloy thin films using co-sputtering technique for displays

Sarkar¹,

Huang

Wang

et al. 2009

Sci. China Ser. E-Technol. Sci.

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In this study we have used a combinatorial approach for producing binary and ternary alloy thin film libraries using a lab-scale RF co-sputtering system. Initially we used two elemental sputtering targets, i.e. aluminum (Al) target and neodymium (Nd) target, to produce a film library of varying composition and successfully identified a suitable composition range (1.95-2.38 at% Nd) in which resistance to hillock formation and resistivity of the film spots were found to be satisfactory in annealed state (350℃, 30 min). In another case, in order to form ternary alloy composition library we have used two sputtering targets, i.e. an Al-0.5 at% Nd alloy target and an elemental Ni target. Though, co-sputtered Al-0.6 at% Nd-0.9 at% Ni alloy films showed satisfactory resistance to hillock formation and low resistivity after annealing, film deposited from a ternary alloy target with the same composition failed to show satisfactory resistance to hillock formation during annealing. In case of Al-0.6 at% Nd-0.9 at% Ni alloy target, 250 nm thick film showed poor resistance to hillock formation than the 500 nm thick film. This clearly showed thickness-dependent hillock performance of Al-0.6 at% Nd-0.9 at% Ni alloy. In this study it was found that, in addition to the process variables, metallurgical microstructure of the alloy sputtering targets had significant effect on the film properties which was not obvious from the results of films deposited using co-sputtering of the individual elemental targets.co-sputtering, thin films, aluminum alloys, displays

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“…It is widely recognized that aluminum alloys are very useful materials for the interconnection lines of amorphous-silicon (a-Si) thin film transistors (TFTs) in liquid crystal displays (LCDs) [1,2] as well as low temperature polycrystalline silicon (LTPS)-TFT LCDs [3]. For instance, thin films of aluminum-neodymium (Al-Nd) alloy are widely used for the gate lines of a-Si TFT, and source and drain lines of LTPS-TFT, because of its stability at high temperature processes such as chemical vapor deposition (CVD) of silicon nitride (SiN) or silicon oxide (SiO x ), and sintering.…”

Section: Introductionmentioning

confidence: 99%

24.2: Single Layer Al‐Ni‐La‐Si Interconnections for Source and Drain of LTPS‐TFT LCDs Using Direct Contacts with both ITO and poly‐Si

Kugimiya¹,

Yoneda²,

Kusumoto³

et al. 2008

Symp Digest of Tech Papers

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It was demonstrated for the first time that the use of Al‐Ni‐La‐Si alloy films for the direct contacts of interconnection lines with both ITO and poly‐Si was feasible for the LTPS‐TFTs. Measured contact resistivity was in the order of 10−4 Ω.cm2 for ITO and Al‐0.6 at.% Ni‐0.1 at.% La‐0.5 at.% Si. The Al alloy films patterned on poly‐Si were found to be stable below 350 °C. It was also found that Al alloy has good dry etching characteristics such as a high etching rate and good selectivity to photo‐resist, suitable for high‐resolution LTPS‐TFT LCDs.

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Nanometer-Scale Investigation of Al-Based Alloy Films for Thin-Film Transistor Liquid Crystal Display Arrays

Cited by 19 publications

References 3 publications

Aluminum-based gate structure for active-matrix liquid crystal displays

Aluminum-based gate structure for active-matrix liquid crystal displays

A combinatorial approach of developing alloy thin films using co-sputtering technique for displays

24.2: Single Layer Al‐Ni‐La‐Si Interconnections for Source and Drain of LTPS‐TFT LCDs Using Direct Contacts with both ITO and poly‐Si

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