Reaction Mechanism of Area-Selective Atomic

Transcription

1 Supporting Information Reaction Mechanism of Area-Selective Atomic Layer Deposition for Al 2 O 3 Nanopatterns Seunggi Seo 1, Il-Kwon Oh 1, Byung Chul Yeo 1, 2, Sang Soo Han 2, Chang Mo Yoon 1, JOON YOUNG YANG 3, Jonggeun Yoon 3, Choongkeun Yoo 3, Ho-jin Kim 3, Yong-baek Lee 3, Su Jeong Lee 4, Jae-Min Myoung 4, Han-Bo-Ram Lee 5, Woo-Hee Kim 6, and Hyungjun Kim 1 * 1 School of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemungu, Seoul 03722, Rep. of Korea 2 Center of Computational Science, Korea Institute of Science and Technology (KIST), Hwarangno 14-gil 5, Seoul, 02792, Rep. of Korea 3 LG Display Co., Ltd., 245, LG-ro, Wollong-myeon, Paju-si, Gyeonggi-do 10845, Rep. of Korea 4 Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Rep. of Korea 5 Department of Materials Science and Engineering, Incheon National University, Incheon, Rep. of Korea 6 Division of Advanced Materials Engineering, Chonbuk National University, Jeonbuk 54896, Republic of Korea * Corresponding author. hyungjun@yonsei.ac.kr S-1

2 Blocking properties of ODPA at various growth temperatures The general recipe of our laboratory for ALD of Al 2 O 3 consists a 8.9 Torr TMA with an injection time of 100 ms, 1.3 Torr Ar with a purging time of 12 s, 8.9 Torr H 2 O with an injection time of 100 ms, and 1.3 Torr Ar with a purging time of 12 s at a growth temperature of 150 C. We performed 150 ALD cycles for Al 2 O 3 on ODPA-coated Ti substrates at various growth temperatures (50, 100, 150, and 200 C). After the deposition, we measured the WCA of the samples. All of the samples showed hydrophilic properties, with WCA values of 44.7, 44.5, 44.7, and 44 for samples deposited at 50, 100, 150, and 200 C, respectively. This results means that growth temperature does not affect the deposition of the ALD Al 2 O 3 film on ODPAcoated Ti substrates. Figure S1. WCA after 150 ALD cycles for Al 2 O 3 on ODPA at various temperatures (50, 100, 150, and 200 C). S-2

3 Blocking properties of three kinds of SAMs Figure S2(a) shows the WCA values as a function of ALD cycles on three kinds of SAM-coated Ti substrates. At 0 cycles, the WCA values of the ODTS-, DDPA-, and ODPA-coated Ti substrates were 104, 106, and 110, respectively. Up to 150 ALD cycles, the WCA values of ODTS-coated Ti continuously decreased to 44.7, which means that an Al 2 O 3 film was continuously deposited on the ODTS surfaces. In contrast, a much slower change in the WCA value was observed for the DDPA-coated Ti substrate. At 0 cycles, bare DDPA on the Ti substrate showed hydrophobic properties with a WCA of 106. After 20 cycles, the WCA value decreased to 103, which is a much smaller change than observed for the ODTS-coated Ti substrates, which indicates the DDPA is able to block the formation of Al 2 O 3 layers more effectively than ODTS. Further ALD cycles from 20 to 150 leads result in a continuous decrease of WCA to 44.8, which means that DDPA could block ALD of Al 2 O 3 for the first 20 cycles. The ODPA-coated Ti substrate showed a slow change in the WCA values, as shown in Figure 2(a). At 0 cycles, bare ODPA on the Ti substrate showed hydrophobic properties with a WCA of 110. After 20 cycles, the WCA value decreased to 109, which is a much smaller than those for ALD Al 2 O 3 on SiO 2 and HF-treated Si substrates. This result indicates ODPA can block the formation of Al 2 O 3 layers much more easily than ODTS or DDPA. The WCA gradually decreases with further cycles, finally reaching a similar WCA value of 44.7 after 150 cycles. Figure S2(b) shows the root-mean-squared (RMS) surface roughness derived from the AFM measurements as a function of ALD cycle on ODPA-, DDPA-, and ODPA-coated Ti substrates. During the transient region when island growth occurs on substrates, the surface roughness increased to a maximum and then decreased to a plateau around saturation. 1 This result indicates that film growth occurs after the ALD cycles with maximum of RMS roughness. The RMS S-3

4 roughness values of the ODTS-coated Ti substrate do not change as a function of ALD cycles. This result means that Al 2 O 3 on could be deposited on ODTS surface by ALD without nucleation delay or island growth. Further, the RMS roughness values of the DDPA-coated Ti substrate increased until about 20 ALD cycles. In subsequent cycles, the RMS roughness value decreased and reached saturation. In addition, RMS roughness values of the ODPA-coated Ti substrate gradually increased with ALD cycles until 90 cycles. In subsequent cycles, the RMS roughness values decreased. These trends revealed that ALD of Al 2 O 3 on ODPA has the longest nucleation delay and island growth region. Thus, ODPA is best candidate for blocking ALD of Al 2 O 3 on Ti substrates. S-4

5 Figure S2. (a) WCA values as a function of ALD Al 2 O 3 cycles (TMA injection pressure of 8.9 Torr and TMA injection time of 100 ms, Ar purging pressure of 1.3 Torr and Ar purging time of 12 s) at 150 C on three different SAM-coated Ti substrates (ODPA, ODTS, and DDPA). The black line with closed squares indicates the WCA values as a function of ALD cycles on ODTScoated Ti substrates, whereas the blue and red lines are the WCA values of DDPA- and ODPAcoated Ti substrates, respectively. (b) RMS roughness as a function of ALD cycles for three different SAM-coated Ti substrates (ODPA, ODTS, and DDPA). S-5

6 H 2 O single dose test To examine why the WCA decreased after deposition of the ALD Al 2 O 3 film, we injected H 2 O on ODPA-coated Ti substrates. As shown in Table 1 of manuscript, the WCA was affected by the conditions of TMA exposure, especially the injection pressure. Then, we exposed ODPAcoated Ti substrates to H 2 O under various pressure and time conditions. As shown in Table S1, the WCA values were not affected by the H 2 O injection conditions. Thus, we concluded that the changes in WCA are caused by TMA molecules on the ODPA surface. Table S1. WCA before and after H 2 O injection under various partial pressure and time conditions. After H 2 O injection, the sample was removed from the chamber and WCA was measured immediately. No injection condition corresponds to the WCA of the bare ODPAcoated Ti substrate. Langmuir Pressure (Torr) Time (s) (10-6 Torr s) WCA ( ) Sample A No injection Sample B Sample C H 2 O injection Sample D S-6

7 Investigation on the formation of ALD Al 2 O 3 on ODPA before etching We performed XPS analysis of the Al 2p spectra to investigate the amount of Al after 370 ALD cycles on both ODPA and Ti substrates. The atomic concentration of Al is about 3.6 % for the ODPA substrate after 370 ALD cycles, while it is about 33.2 % for the Ti substrate. A previous study showed that 3 nm thick Al 2 O 3 film has a low atomic concentration of Al of about 5 %. Thus, after 370 cycles, the thickness of the Al 2 O 3 film on ODPA was probably less than 3 nm. 2 Intensity (Arb. Units) Al 2p ALD Al 2 O 3 on Ti ALD Al 2 O 3 on ODPA Binding Energy (ev) Figure S3. The Al 2p spectra from XPS of 370 cycles ALD Al 2 O 3 on Ti substrate and ODPA coated Ti substrates. S-7

8 Investigation on the Thermal stability of ODPA SAM Previous studies showed that SAM defects can be formed by external energy, such as UV light irradiation, 3 plasma treatment, 3,4 and heat treatment (above 350 C). 3 Exposure to such treatments caused the decomposition of the alkyl chains of ODPA. 3,4 In our study, among them, thermal energy from the chamber could only generate the defect of SAM. We evaluated the thermal stability of the ODPA SAM, and measured the WCA change of the ODPA-coated Ti sample in a vacuum chamber at 150 C. Figure S4 shows the WCA change as a function of exposure time. The WCA value remained unchanged within the error throughout the heating time. This indicates that the ODPA SAM was not degraded by thermal energy during the ALD process. Figure S4. WCA values as a function of heating time at 150 C for ODPA-coated Ti substrates. S-8

9 Selection of SAM coverage condition in MD simulation We conducted the MD simulation with two kinds of SAM packing. Figure S5(a) and (b) show the simulation results for the placement of the ODPA SAM on the Ti (100) surface with 1 1 and 2 2 coverage, respectively. A previous study showed that the SAM molecules adopt conformations that minimize the free energy, 5 and that in order to minimize the free energy, SAM molecules are adsorbed on surface with tilted and twisted structures. 5 In Figure S5(a), we observed that with 1 1 coverage, the ODPA SAM adsorbed on the Ti substrate oriented in the normal direction of the surface. There was no penetration of the TMA molecules into the ODPA film. However, this structure is energetically unstable. Thus, we chose the 2 2 coverage to represent a structure comparable to the real SAM. Figure S5. The side view of initial MD simulation cell, where ODPA SAMs are aligned through VDW inter action each other, with the coverage (a) 1 1 grid/molecules without TMA molecules and (b) 2 2 grid/molecules without TMA molecules. S-9

10 ALD Al 2 O 3 on ODPA with longer purge time Further decrease in the TMA pressure and increase in the purging time compared to those of the optimized conditions could lead to reduced ALD growth per cycle (GPC). In the case of TMA pressure, 1.3 Torr of TMA injection pressure was the minimum required for the ALD reaction, since Al 2 O 3 was not deposited at TMA injection pressures lower than 1.3 Torr. In the case of purging time, Figure S6 shows the WCA values as a function of the number of ALD Al 2 O 3 cycles on the ODPA on Ti substrate using different ALD recipes, with two Ar purging times of 12 s and 60 s. Similar values of WCA were observed after the deposition, indicating that 12 s is sufficient to purge excess gas molecules on the surface. In spite of the optimized ALD process conditions, we observed that the WCA decreased slightly, by about 5, after 370 cycles. The reason for the slight decrease in the WCA from 110 to 105 might be the existence of a small amount of AlO x on the ODPA substrate, corresponding to a 3.6% atomic concentration of Al on ODPA, as shown in Figure S3. In addition, the error range of the WCA value is about 3.2, and thus the measurement error might be included. Figure S6. WCA values as a function of ALD Al 2 O 3 cycles by using developed process with longer purging time (12 s, 60 s) until 370 cycles at 150 C. S-10

11 Coating properties of ODPA with dipping and microcontact printing methods Previous studies showed that the microcontact printing method could be used to coat the SAM layer with comparable quality to liquid or vapor deposition. 6 9 We also evaluated packing density of microcontact printed ODPA using WCA measurements. The WCA values of the dipped and stamped substrates were similar, indicating that the quality of the microcontact printed SAM is comparable to that of the SAM coated by the dipping method. Figure S7. WCA values of ODPA coated by dipping and stamping. S-11

12 Investigation on parasitic addition of GPC by ODPA The GPC of this study was slightly higher than that of generally reported studies. We have performed ALD Al 2 O 3 on Ti substrate with and without ODPA in ALD reactor to investigate the SAM effect on parasitic addition of GPC. The results are shown in Figure S8. The GPC of both conditions are same as 1.6 Å/cycle. Based on the results, we think that the diffused TMA molecules in ODPA SAMs did not release during H 2 O pulse. 60 ALD Al2O3 with decreased TMA and increased Ar pressure Thickness (nm) with ODPA without ODPA ALD cycles Figure S8. Thickness deposited by ALD Al 2 O 3 process with (red line with open circle) and without (blue line with open triangle) ODPA in chamber S-12

13 Supporting reference (1) Geidel, M.; Junige, M.; Albert, M.; Bartha, J. W. In-Situ Analysis on the Initial Growth of Ultra-Thin Ruthenium Films with Atomic Layer Deposition. Microelectron. Eng. 2013, 107, (2) Dechana, A.; Thamboon, P.; Boonyawan, D. Microwave Remote Plasma Enhanced- Atomic Layer Deposition System with Multicusp Confinement Chamber. Rev. Sci. Instrum. 2014, 85 (10), (1) (7). (3) Kanta, a.; Sedev, R.; Ralston, J. The Formation and Stability of Self-Assembled Monolayers of Octadecylphosphonic Acid on Titania. Colloids Surfaces A Physicochem. Eng. Asp. 2006, 291 (1 3), (4) Lee, H.-B.-R. Degradation of the Deposition Blocking Layer during Area-Selective Plasma-Enhanced Atomic Layer Deposition of Cobalt. J. Korean Phys. Soc. 2010, 56 (1), (5) Love, J. C.; Estroff, L. a.; Kriebel, J. K.; Nuzzo, R. G.; Whitesides, G. M. Self-Assembled Monolayers of Thiolates on Methals as a Form of Nanotechnology; 2005; Vol (6) Jiang, X.; Bent, S. F. Area-Selective ALD with Soft Lithographic Methods: Using Self- Assembled Monolayers to Direct Film Deposition. J. Phys. Chem. C 2009, 113 (41), (7) Mackus, A. J. M.; Bol, A. A.; Kessels, W. M. M. The Use of Atomic Layer Deposition in Advanced Nanopatterning. Nanoscale 2014, 6, (8) Jiang, X.; Chen, R.; Bent, S. F. Spatial Control over Atomic Layer Deposition Using Microcontact-Printed Resists. Surf. Coatings Technol. 2007, 201 (22 23 SPEC. ISS.), S-13

14 (9) Wilbur James, L.; Kumar, A.; Biebuyck, H. A.; Kim, E.; Whitesides, G. M. Microcontact Printing of Monolayers : Applications in Microfabrication. Nanotechnology 1996, 7 (4), S-14