High device performance of unique ALD-IGZO TFTs to look forward to expanding application area to semiconductor

Amorphous In-Ga-Zn-O (IGZO) materials have been mainly employed as channel materials for the backplane TFTs of flat panel displays (FPDs) owing to their superior characteristics of excellent uniformity, high on/off current ratio, and superior carrier mobility to other amorphous oxide semiconductors. Recently, IGZO thin films have been actively researched for high-end future electronic applications such as TFTs of DRAM and NAND which are typical semiconductor memory devices as well as transparent flexible displays, sensors and logic architectures.

Especially, considering indispensable three dimension architectures of the memory devices for high functional AI semiconductors, the interest in application of IGZO TFTs has been rapidly increased because they are satisfied with the requirement of low power consumption and low operation temperature.

The atomic layer deposition (ALD) method is resulting in better film quality even at a lower deposition temperature. Furthermore, the film thickness and composition can always be precisely controlled at the atomic scale with excellent conformality and higher film density. However, ALD process for IGZO as multi-component materials has the difficulty of control between metal precursors and oxidants.

Variations in transfer curves with the lapse of stress time for 104 s under PB(T)S conditions for Dev. (a) A(1:1:1) and B(1:1:3) at RT and for Dev. (c) A and (d) B at 60℃. (VGS= +20V, VDS= 10.5 V)*


The targeted atomic compositions (In:Ga:Zn) of ALD-IGZO films were acquired by controlling the ALD cycle ratios using the unique ALD method to clear this issue. The device employing (1:1:3) composition exhibited the most desirable characteristics from the viewpoint of excellent bias stability, and they were found to be superior to those by the conventional sputtered-deposited IGZO TFTs.

Therefore, this method to control the compositions of IGZO could be a core technology to guarantee high performance and robust stability for various future ALD-IGZO thin film applications.

Si wafer based batch ALD cluster system

NCD has been developing high throughput batch ALD-IGZO system using the unique technology capable of controlling the designed atomic compositions of IGZO for etch applications. This system could provide the excellent quality competiveness and functional stability as well as high throughput in production of 3D complex architectures such as future Logic, DRAM and NAND devices expected to apply ALD-IGZO thin films.

*Journal of Materials Chemistry C, 2019, 7, 6059, Cationic compositional effects on the bias-stress stabilities of thin film transistors using In-Ga-Zn-O channels prepared by atomic layer deposition, Seung-Bo Ko, Nak-Jin Seong, Kyujeong Choi, So-Jung Yoon, Se-Na Choi, and Sung-Min Yoon. DOI: 10.1039/c9tc01164a

Link : http://www.ncdtech.co.kr/2018/bbs/board.php?bo_table=eng_board_05&wr_id=45

Hydrogen diffusion barrier using thermal ALD Al2O3 encapsulation for IGZO TFTs

Amorphous phase In-Ga-Zn-O(IGZO), the typical oxide TFT compositions, has 20 to 50 times higher of field-effect mobility than that of a-Si TFTs and excellent SS (Sub-Threshold Voltage Swing) properties as well as has been very promising to apply for high performance and large area displays and for transparent displays due to their superior properties and good uniformity.

But IGZO TFTs with PECVD SiNx as an encapsulation layer have degraded their superb properties because hydrogen included in SiNx from 20% to 30% has passed through OLED layers and then diffused into IGZO layers.

Comparison of I-V characteristic of a-IGZO TFTs with and without hydrogen diffusio

If this performance degradation by hydrogen diffusion showed in typical I-V graph, SS slop would be decreased, Ioff increased and Vth shifted to negative direction from the original I-V curve.

In case of applying to OLED display with IGZO TFTs using SiNx encapsulation layers including hydrogen, Al2O3 layers would be the very excellent barriers not to degrade IGZO TFTs properties by diffusion of hydrogen from SiNx.

However it is not good choice to apply PEALD Al2O3 using plasma to the first encapsulation layer because oxygen plasma could cause the side effect such as cathode oxidation during the process. So IGZO TFTs and thermal ALD Al2O3 encapsulation layers without plasma damage could be optimum combination.

NCD Lucida GD Series that is thermal ALD batch equipment for mass production to deposit on large substrates up to 6th generation glasses could provide superior Al2O3 hydrogen barriers preventing diffusion into IGZO TFTs from PECVD SiNx encapsulation layers including hydrogen as well as expect to apply to transparent fordable OLED displays by using Al2O3/Polymer/Al2O3 encapsulation layers.

NCD’s LucidaTM GD Series ALD

NCD’s ALD IGZO TFTs exhibit remarkable stabilities

NCD Co., Ltd, a global equipment and technology provider of ALD (Atomic Layer Deposition), has developed oxide Thin Film Transistors (TFTs) using In-Ga-Zn-O (IGZO) channels.

IGZO oxide TFTs have rapidly been increased interest in these days, as LTPO oxide TFTs have been adapted for state of the art displays like apple watches as well as IGZO is the most applicable for future transparent flexible devices due to its high mobility and optical transparency. However, IGZO thin films are required to meet the various properties such as higher resolution, large-area uniformity, and better device stability with ultra-thin and flexible structures. Atomic layer deposition (ALD) has recently been reported as a replacement for the conventional sputtering method for fabricating IGZO thin films. The sputtering deposition has some problems such as uniformity issues in thickness and composition, degradation of properties by plasma damages and non-uniformity in the magnetic field, and stability issue of the sputtering target. While ALD-IGZO could show film thickness and composition control in atomic scale, high film conformity and excellent thickness uniformity on large area substrates because ALD is dominated by a self-limiting growth mechanism.

Figure 1: (a) Structure of IGZO TFT and microscopic cross-sectional view of IGZO TFT by Lucida GD Series ALD

Figure 2: a) Comparisons of the IDS–VGS transfer characteristics and IGS gate leakage currents between the devices using ALD IGZO channels with thicknesses of 6 and 10 nm. (b) IDS–VDS output characteristics for the TFT using 6 nm-thick IGZO channel.(*)

NCD has developed oxide TFTs using very thin In-Ga-Zn-O channels, and the excellent device characteristics and the reliable bias temperature stabilities can be successfully obtained. Such a remarkable device stabilities of TFTs with the IGZO channel prepared by the ALD process can help extend the employment of IGZO TFTs for various applications.(*)



NCD’s Lucida GD Series ALD which can run up to 6th generation substrates (1500x1850mm2) could be the best ALD coating solutions for IGZO channels since it’s very compatible, reliable, and producible on large area applications. NCD could provide the most advanced ALD-IGZO technology with its technological knowledge and experience to the customers who are seeking competitive ALD-IGZO systems for current LTPO applications or large-area OLED displays as well as for future flexible transparent displays.

Figure 3: Lucida™ GD Series ALD


* RSC Adv., 2018, 8, 25014, Investigations on the bias temperature stabilities of oxide thin film transistors using In–Ga–Zn–O channels prepared by atomic layer deposition, So-Jung Yoon, Nak-Jin Seong, Kyujeong Choi, Woong-Chul Shin, and Sung-Min Yoon. DOI: 10.1039/c8ra03639j

NCD launch new updated website for ALD technology and equipment

Updated website NCD for ALD technology and equipment: www.ncdtech.co.kr

NCD updated its website with re-formation and company promotional video clip for the introduction and main equipment.

NCD contracted to supply new ALD equipment for production of µ-OLED with LG Display

Korean ALD equipment manufacturer, NCD reports new order of µ-OLED ALD equipment from LG Display

"NCD has recently contracted with LGD to supply µ-OLED manufacture equipment which is new Lucida GuD Series for Al2O3-ALD encapsulation to avoid OLED degradation induced water and oxygen. Newly introduced Lucida GuD is high volume batch-type ALD equipment based on the process and hardware of OLED encapsulation technology of Lucida GD Series.

µ-OLED produced by this system is micro display with high resolution for augmented reality(AR) and virtual reality(VR) and has been expected the huge application and market in the future.

Otherwise, manufacture of µ-OLED requests high productivity like display industry therefore ALD tools with high film quality and low throughput for Semiconductor couldn’t meet the need of the customers and the market. So NCD is more expecting that this µ-OLED is next growth engine market because it has high volume ALD equipment and excellent OLED encapsulation technology.

NCD will lead µ-OLED ALD equipment market with this starting point and continue to make efforts to become the world’s best specialized ALD technology company.”
 

LucidaTM GuD Series

Updated website NCD for ALD technology and equipment

Updated website NCD for ALD technology and equipment: www.ncdtech.co.kr

NCD updated its website with re-formation and the new company promotional video clip for the introduction and main equipment.

NCD to supply a repeat order of Lucida GS Series for Hyundai Heavy Industry Green Energy in Korea

Korean ALD equipment manufacturer NCD reports repeat order for Al2O3 ALD passivation from Hyundai Heavy Industry Green Energy.

"NCD has recently contracted with HHIGE to supply solar cell manufacture equipment which is Lucida GS Series ALD with automation for high efficiency crystalline solar cell using Al2O3-ALD passivation and is upgrade version improving the throughput and wafer handling speed from previous supplied equipment. Lucida GS Series is batch type ALD deposition equipment that forms backside passivation of Al2O3 on multiple wafers and can process more than 4.500 wafers (@ 4nm thickness) of 156mm x 156mm size per an hour.

This repeat order shows that the customer has had confidence in the technology of NCD and the excellence of the equipment."

The Lucida GS Series with Automation is a high throughput atomic layer deposition system for surface passivation of c-Si solar cells (ncdtech.co.kr)

NCD Contracted with TIANMA to supply 6G half ALD equipment for flexible OLED encapsulation

NCD recently signed a contract with TIANMA, one of Chinese leading display manufacturers, to provide 6G half ALD equipment for encapsulation of flexible OLEDs in the next six months to Wuhan TIANMA. This is a follow-up order to purchase NCD's 6G half (1500mmX925mm) ALD equipment, which is based on the superior performance evaluation of earlier installed 5.5G class ALD equipment in Shanghai TIANMA.

The performance of ALD encapsulation by the existing equipment showed excellent film uniformity as well as excellent moisture permeability and step coverage, compared to that by PECVD, and was qualified by the customer's flexible OLED products.

This proves that NCD's ALD core technology and the reliability of equipment have been recognized by its customer.
 

It is challenging to realize device reliability using current encapsulation technology deposited by PECVD for the next generation flexible OLED devices, since it requires bending, folding and rolling, ALD technology will be an essential choice for future flexible OLED products with its excellence and competitiveness.

NCD will make the Lucida GD series become the standard ALD equipment for all flexible OLED encapsulation based on these needs, and continue to grow into the world's most professional ALD Company with new challenges and developments. 

 

 

Cluster system for Lucida™ GD series

NCD announced to provide solar cell ALD equipment to SF-PV

NCD recently shipped the equipment to SF-PV who is a Chinese solar cell manufacturer. This system is (Lucida GS Series + Automation) to increase the efficiency of solar cells by depositing high quality Al2O3 ALD thin films. It will be installed on the site in the end of March and begin production in April.

Lucida GS Series is batch type ALD deposition equipment that forms backside passivation of Al2O3 on multiple wafers and can process more than 4.500 wafers (@ 4nm thickness) of 156mm x 156mm size per an hour. By applying Lucida GS Series in the production of solar cells, customers can dramatically lower the production cost of high efficiency solar cells due to the high-volume productivity, high yield, efficient gas consumption and low maintenance cost compared to competitors. 

(Lucida™ GS series + Automation)