ALD2019 Session AA2-WeM: ALD for ULSI Applications I

Wednesday, July 24, 2019 10:45 AM in Grand Ballroom H-K

Wednesday Morning

Session Abstract Book
(276KB, May 5, 2020)
Time Period WeM Sessions | Abstract Timeline | Topic AA Sessions | Time Periods | Topics | ALD2019 Schedule

Start Invited? Item
10:45 AM AA2-WeM-12 The Journey of ALD High-k Metal Gate from Research to High Volume Manufacturing
Dina Triyoso, Robert Clark, Steven Consiglio, Kandabara Tapily, Cory Wajda, Gert Leusink (TEL Technology Center, America, LLC)

In the early days of the search to find a replacement for SiO2-based gate oxides the goal was to find a material with a very high k value which could be incorporated into CMOS production for multiple technology nodes. A historical overview of the many promising high k materials considered for SiO2 replacement leading to the selection of ALD HfO2 as “the winner” will be presented. ALD HfO2 has successfully been implemented in CMOS production for over a decade, starting at the 45nm node. There are two general integration approaches for implementing ALD High-k/Metal Gate stacks (HKMG) in production: gate first and gate last. Challenges with each integration approach, leading to the wider adoption of gate last will be discussed. Furthermore, as the dielectric constant of HfO2 is only ~20 and a thin SiO2-base interface was still required to maintain mobility and reliability, HfO2 provided essentially a one-time scaling benefit. Further thinning of HfO2 resulted in unacceptable leakage and thus to continue transistor scaling fully depleted devices such as FINFET and Ultra Thin Planar SOI (FDSOI) were pursued. High volume manufacturing flows for FINFET (with gate last integration) and FDSOI (with gate first integration) come with their own unique challenges. For example, with FINFET maintaining gate height uniformity is crucial for Vt targeting and control. With FDSOI, maintaining gatestack stability at high temperature is key. To continue future scaling, new device architectures (e.g. GAA, Vertical FETs, etc.) will pose further challenges for gate stack integration. Recent and historical progress in HfO2 growth, interface control, selective deposition, morphology and etching will be discussed with respect to the possibility for future gate stack engineering.

References:

R.D. Clark, Materials, 7(4), 2913-2944, https://doi:10.3390/ma7042913 (2014).

D.H. Triyoso et al., ECS Transactions, 69 (5) 103-110 (2015).

R.J. Carter et al., ECS Transactions, 85(6) 3-10 (2018).

R.D. Clark et al., ECSarXiv. October 3. https://doi:10.1149/osf.io/qtxnd (2018).

R.D. Clark et al., APL Materials 6, 058203; https://doi.org/10.1063/1.5026805 (2018).

11:15 AM AA2-WeM-14 Effects of Er Doping on Structural and Electrical Properties of HfO2 Grown by Atomic Layer Deposition.
Soo Hwan Min, Bo-Eun Park, Chang Wan Lee (Yonsei University, Republic of Korea); Wontae Noh (Air Liquide Laboratories Korea, South Korea); Il-Kwon Oh (Yonsei University, Republic of Korea); Woo-Hee Kim (Hanyang University, Republic of Korea); Hyungjun Kim (Yonsei University, Republic of Korea)

Gate dielectric materials with high-k are required for further scaling down in future years. As an alternative of conventional high-k materials such as HfO2, the addition of elements to host high-k materials has attracted attention. Among various elements, rare-earth elements, such as Y, La, Dy, or Er has been known to transform the crystal structure of HfO2 from the first-principles study. The theoretical study showed that the doping into HfO2 can energetically stabilize the cubic or tetragonal phase at lower temperature than thermodynamic conditions of pure HfO2. Since cubic (k~29) or tetragonal (k~70) HfO2 has much higher dielectric constant than that of amorphous (k~16-19) and monoclinic (k~20-25) phases, it is noteworthy that the structural modulation by doping of rare-earth elements can enhance the electrical properties of HfO2.

In this work, Er doping into HfO2 was experimentally carried out using atomic layer deposition (ALD) super-cycle process with Er(MeCp)2(N-iPr-amd), HfCl4, and H2O co-reactant. ALD Er-doped HfO2 with a variety of Er/(Er+Hf) compositions were systematically examined, mainly focusing on structural and electrical properties. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were utilized to investigate the film composition and crystal structure. In addition, MOS capacitors were fabricated with various compositions to evaluate the electrical properties from capacitive-voltage (C-V) and current-voltage (I-V) measurements. In specific ratio, the dielectric constant and the interface trap density of Er-doped HfO2 were found to have significantly improved compared to undoped HfO2. Structural and electrical characterization revealed that the addition of Er to HfO2 induces phase transformations from the monoclinic to the cubic or tetragonal phases, even at low post-annealing temperatures of 600°C. This study identifies optimum conditions to improve the electrical properties of Er-doped HfO2 films which have potential applications in future nanoscale devices. View Supplemental Document (pdf)
11:30 AM AA2-WeM-15 Improvement of Electrical Performances of Atomic Layer Deposited ZrO2 MIM Capacitors with Ru Bottom Electrode
Jaehwan Lee, Bo-Eun Park (Yonsei University, Republic of Korea); Wontae Noh (Air Liquide Laboratories Korea, South Korea); Il-Kwon Oh (Yonsei University, Republic of Korea); Woo-Hee Kim (Hanyang University, Republic of Korea); Hyungjun Kim (Yonsei University, Republic of Korea)

With accelerated scaling down and three-dimensional structuring of integrated circuits, it becomes very challenging to fabricate metal-insulator-metal (MIM) capacitors with low leakage current and high capacitance density. Specifically, the introduction of high-k dielectrics in conjunction with TiN electrodes has improved electrical properties in sub-100 nm processes. Various high-k dielectrics layers combined with TiN electrodes in MIM capacitors were studied for further improvement of MIM capacitors. Controlling an interfacial layer formation between dielectric layer and metal electrode is essential for depositing high-k dielectric thin film on a TiN electrode. When high-k dielectric films were placed on the TiN, interfacial layer was formed due to high reactivity of TiN. The interfacial layer acts as charge traps causing degradation of electrical properties. Surface treatment like plasma treatment on the TiN has been known to help suppress formation of an interfacial layer, but it would be hard to apply for mass-production of DRAM process due to difficulty of uniform treatment without damage caused by energetic species such as ions and radicals on the devices formed inside deep trenches with high aspect ratio.

Alternatively, selection of stable metal electrodes with high work function is required to improve electrical properties. Among several metals, Ru electrode can be appropriate option due to its good thermal and chemical stability, low resistivity, high work function. In this paper, we investigated effects of bottom electrodes on the thin film properties of atomic layer deposited (ALD) ZrO2, concentrating on correlation between interfacial layer formation and electrical properties. Transmission electron microscopy (TEM) showed thinner thickness of the interfacial layer on the Ru electrode than TiN electrode. Chemical composition of the interfacial layer was analyzed by X-ray photoelectron spectroscopy (XPS) analysis, and ZrO2 on Ru was less intermixed with bottom electrode due to good thermal and chemical stability of Ru electrode. Introducing Ru electrode improved symmetry of the normalized C-V characteristics. Simultaneously, the introduction of Ru electrode affects decrease of leakage current density from ~10-5 A/cm2 to ~10-7 A/cm2 in I-V characteristics. These results are very meaningful capacitor with Ru electrode can be a very promising device for MIM capacitor in DRAM production.

View Supplemental Document (pdf)
11:45 AM AA2-WeM-16 Perfecting ALD-Y2O3/GaAs(001) Interface with Ultra-High Vacuum Annealing
Keng-Yung Lin, Yen-Hsun Lin, Wan-Sin Chen, Hsien-Wen Wan, Lawrence Boyu Young (National Taiwan University, Republic of China); Chiu-Ping Cheng (National Chia-Yi University, Republic of China); Tun-Wen Pi (National Synchrotron Radiation Research Center, Republic of China); Jueinai Kwo (National Tsing Hua University, Republic of China); Minghwei Hong (National Taiwan University, Republic of China)

High-performance metal-oxide-semiconductor field-effect transistors (MOSFETs) require the semiconductor/high-κ interface with high-temperature thermal stability and a low interfacial trap density (Dit). Previously, in-situ atomic layer deposition (ALD) or molecular beam epitaxy (MBE) Y2O3 has effectively passivated GaAs(001) surface.1,2 The growth was achieved in an integrated ALD/MBE ultra-high vacuum (UHV) system. Despite the difference in deposition, both Y2O3/GaAs interfaces withstand 900 oC annealing, and the Dit’s lie below 5×1011 eV-1cm-2. MOS capacitors (MOSCAPs) with such interface outperform those with ex-situ deposited Al2O3.3 By in-situ synchrotron radiation photoemission study on ALD-Y2O3/GaAs(001)-4×6, we found that the faulted surface As atoms were removed and lines of Ga-O-Y bonds stabilized the interface.4 The interfacial Ga2O (Ga+)-like state explains the low Dit.

In this work, we have improved the electrical characteristics in ALD-Y2O3/GaAs by in-situ UHV annealing the initial 1-nm Y2O3. The idea is motivated by removing the freed As atoms and hydrocarbons remained in the ALD layer. Note that, an amount of hydrocarbons at such critical interface can degrade the device performances. ALD-Y2O3 was grown by thermal ALD with sequential Y(EtCp)3 and H2O pulses, and in-situ UHV annealing up to 600 oC was conducted in another chamber in our system right after the ALD growth. MBE-Y2O3 is relatively pure and employed as a reference.

Fig. 1 shows the capacitance-voltage (CV) and quasi-static CV (QSCV) curves for MOSCAPs. The UHV-annealed ALD-Y2O3/GaAs was improved with a reduced frequency dispersion (F.D.) in the accumulation/depletion region, and a lowered trap-induced hump in the inversion region. Fig. 2 presents the Dit spectra extracted from QSCVs. The UHV-annealed ALD-Y2O3/GaAs shows a reduced Dit, also hinted by the sharp transition of QSCVs and the narrow gap between QSCVs and CVs. Fig. 3 shows the O 1s core-level spectra, where O-Y is from the stoichiometric Y2O3 and O* is from the interfacial Ga-O-Y and the surface Y-O-H.4 Note that the ratios of O-Y of our 1-nm Y2O3 films are significantly higher than the one reported.5 Upon UHV annealing, the residue O* may be attributed to the interfacial Ga-O-Y with the surface Y-O-H mostly removed. This UHV annealing approach is significant in perfecting ALD-Y2O3/GaAs and is applicable to many other material systems.

References:

1 Y. H. Lin et al., Appl. Phys. Express 9, 081501 (2016).

2 H. W. Wan et al., J. Cryst. Growth 447, 179 (2017).

3 T. Yang et al., Appl. Phys. Lett. 91, 142122 (2007).

4 C. P. Cheng et al., ACS Omega 3, 2111 (2018).

5 P. de Rouffignac et al., Chem. Mater. 17, 4808 (2005).

View Supplemental Document (pdf)
Session Abstract Book
(276KB, May 5, 2020)
Time Period WeM Sessions | Abstract Timeline | Topic AA Sessions | Time Periods | Topics | ALD2019 Schedule