Residual Stress Relaxation and Microstructure in ZnO Thin Films

Stability under normal environmental conditions over a long period of time is crucial for sustainable thin-film device performance. Pure ZnO films with thicknesses in the 140 - 450 nm range were deposited on amorphous glass microscope slides and (100)-oriented single crystal silicon wafers by radio frequency magnetron sputtering. The depositions were performed at a starting temperature of 200 oC. ZnO films had a columnar microstructure strongly textured along the <0002> direction. XRD peak-shift analysis revealed that the films were under residual, compressive, in-plane stress of -5.46 GPa for the glass substrate and -6.69 GPa for the Si substrate. These residual stresses could be completely relaxed by thermal annealing in air. When left under normal environmental condition over an extended period of time the films failed under buckling leading to extensive cracking of the films. The XRD and SEM results indicated different mechanisms of stress relaxation that were favored in the ZnO thin films depending on the energy provided. Although thermal annealing eliminated residual stresses, serious micro-structural damage upon annealing was observed. Thermal annealing also led to preferential growth of some ZnO crystals in the films. This kind of behavior is believed to be indicative of stress-induced directional diffusion of ZnO. It appears that for the extended stability of the films, the stresses have to be eliminated during deposition.

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Rapid Thermal Annealing for Residual-Stress Relaxation in Undoped or Doped Polysilicon Thin Films

MRS Proceedings ◽

10.1557/proc-546-27 ◽

1998 ◽

Vol 546 ◽

Author(s):

Xin Zhang ◽

Tong-Yi Zhang ◽

Yitshak Zohar

Keyword(s):

Thin Films ◽

Residual Stress ◽

Stress Relaxation ◽

Residual Stresses ◽

Thermal Annealing ◽

Rapid Thermal Annealing ◽

Stress Evolution ◽

Before And After ◽

Polysilicon Films ◽

Compressive Residual Stresses

AbstractThe residual stress in doped and undoped polysilicon films, before and after rapid thermal annealing (RTA), is investigated using both wafer-curvature and micro-rotating structures techniques. Microstructure characterization has been conducted as well to understand the mechanism of the stress evolution. The results show that the compressive residual stresses in undoped polysilicon films can be reduced or eliminated within a few seconds RTA. Surface nitridation and grain growth are identified as the mechanisms responsible for the stress evolution.

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Structural Properties of Sputter-Deposited ZnO Thin Films Depending on the Substrate Materials

Materials Science Forum ◽

10.4028/www.scientific.net/msf.475-479.1825 ◽

2005 ◽

Vol 475-479 ◽

pp. 1825-1828

Author(s):

Ju Hyun Myung ◽

Nam Ho Kim ◽

Hyoun Woo Kim

Keyword(s):

Thin Films ◽

Thermal Annealing ◽

Room Temperature ◽

Zno Thin Films ◽

Zno Films ◽

X Ray Diffraction ◽

Axis Orientation ◽

X Ray ◽

Sapphire Substrates ◽

Sputter Deposited

We have demonstrated the growth of ZnO thin films with c-axis orientation at room temperature on various substrates such as Si(100), SiO2, and sapphire by the r.f. magnetron sputtering method. X-ray diffraction (XRD) and scanning electron microscopy altogether indicated that the larger grain size and the higher crystallinity were attained when the ZnO films were deposited on sapphire substrates, compared to the films on Si or SiO2 substrates. The c-axis lattice constant decreased by thermal annealing for the ZnO films deposited on Si or SiO2 substrates, while increased by the thermal annealing for the ZnO films grown on sapphire substrates.

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Residual Stress, Adhesion and Crystallization of Ion-Sputtered and Ibed Processed NiTi Films

MRS Proceedings ◽

10.1557/proc-246-349 ◽

1991 ◽

Vol 246 ◽

Cited By ~ 11

Author(s):

B. Walles ◽

L. Chang ◽

D. S. Grummon

Keyword(s):

Thin Films ◽

Residual Stress ◽

Residual Stresses ◽

Crystallization Behavior ◽

Fine Particles ◽

Ion Beam ◽

Amorphous State ◽

Single Crystal Silicon ◽

Ion Sputtering ◽

Crystal Silicon

AbstractWhen conventional sputtering is used to deposit nickel-titanium thin films at temperatures below ∼623 - 723 Kelvins, the resultant structures are amorphous and the films must be annealed to form the requisite B2 parent ordering. This invites complications related to interface diffusion and chemical reaction with components of the substrate. For the present work, thin films of near-equiatomic NiTi were prepared on potassium chloride, (100) single-crystal silicon, and Si3N4 passivated silicon substrates by ion sputtering and by ion beam enhanced deposition (IBED). We have investigated residual stress levels produced by these processes, evaluated substrate adhesion levels, and explored the crystallization behavior of NiTi films grown under conditions of concurrent low-energy inert gas ion bombardment. Residual stresses of ionsputtered and IBED films were measured using profilometric techniques. Film crystallization behavior was studied by transmission electron microscopy of as-deposited films. Films produced by unassisted ion sputtering showed compressive residual stresses in the as-deposited amorphous state, which became highly tensile after annealing, leading to spontaneous cracking and delamination. Preliminary results from IBED experiments showed a reduction in the asdeposited stress, and improved adhesion. Under certain conditions, ion enhancement of the deposition process promoted film crystallization during deposition at moderate substrate temperature, producing a dispersion of extremely fine particles, indexed as Ni3Ti.

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Effects of Thermal Annealing on the Characteristics of High Frequency FBAR Devices

Coatings ◽

10.3390/coatings11040397 ◽

2021 ◽

Vol 11 (4) ◽

pp. 397

Author(s):

Yu-Chen Chang ◽

Ying-Chung Chen ◽

Bing-Rui Li ◽

Wei-Che Shih ◽

Jyun-Min Lin ◽

...

Keyword(s):

Thin Film ◽

Thin Films ◽

Thermal Annealing ◽

Electromechanical Coupling ◽

Zno Thin Films ◽

Electromechanical Coupling Coefficient ◽

Back Side ◽

Zno Thin Film ◽

Frequency Responses ◽

Sputtering System

In this study, piezoelectric zinc oxide (ZnO) thin film was deposited on the Pt/Ti/SiNx/Si substrate to construct the FBAR device. The Pt/Ti multilayers were deposited on SiNx/Si as the bottom electrode and the Al thin film was deposited on the ZnO piezoelectric layer as the top electrode by a DC sputtering system. The ZnO thin film was deposited onto the Pt thin film by a radio frequency (RF) magnetron sputtering system. The cavity on back side for acoustic reflection of the FBAR device was achieved by KOH solution and reactive ion etching (RIE) processes. The crystalline structures and surface morphologies of the films were analyzed by X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM). The optimized as-deposited ZnO thin films with preferred (002)-orientation were obtained under the sputtering power of 80 W and sputtering pressure of 20 mTorr. The crystalline characteristics of ZnO thin films and the frequency responses of the FBAR devices can be improved by using the rapid thermal annealing (RTA) process. The optimized annealing temperature and annealing time are 400 °C and 10 min, respectively. Finally, the FBAR devices with structure of Al/ZnO/Pt/Ti/SiNx/Si were fabricated. The frequency responses showed that the return loss of the FBAR device with RTA annealing was improved from −24.07 to −34.66 dB, and the electromechanical coupling coefficient (kt2) was improved from 1.73% to 3.02% with the resonance frequency of around 3.4 GHz.

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Effects of the Sputtering Time of AlN Buffer Layer on the Quality of ZnO Thin Films

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.881-883.1117 ◽

2014 ◽

Vol 881-883 ◽

pp. 1117-1121 ◽

Cited By ~ 1

Author(s):

Xiang Min Zhao

Keyword(s):

Thin Films ◽

Buffer Layer ◽

Rf Magnetron Sputtering ◽

Buffer Layers ◽

Zno Thin Films ◽

Zno Films ◽

Si Substrates ◽

Atomic Force ◽

Structure Morphology ◽

Aln Buffer

ZnO thin films with different thickness (the sputtering time of AlN buffer layers was 0 min, 30 min,60 min, and 90 min, respectively) were prepared on Si substrates using radio frequency (RF) magnetron sputtering system.X-ray diffraction (XRD), atomic force microscope (AFM), Hall measurements setup (Hall) were used to analyze the structure, morphology and electrical properties of ZnO films.The results show that growth are still preferred (002) orientation of ZnO thin films with different sputtering time of AlN buffer layer,and for the better growth of ZnO films, the optimal sputtering time is 60 min.

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Effects of Withdrawal Speeds on Properties of ZnO Thin Films Prepared by Sol-Gel Immerse Technique

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.680.124 ◽

2016 ◽

Vol 680 ◽

pp. 124-128 ◽

Cited By ~ 1

Author(s):

Chao Du ◽

Yu Chun Zou ◽

Zhi Qing Chen ◽

Wen Kui Li ◽

Shan Shan Luo

Keyword(s):

Thin Films ◽

Growth Process ◽

Sol Gel ◽

Wavelength Region ◽

Zno Thin Films ◽

Zno Films ◽

Photoelectric Device ◽

Near Ir ◽

Crystal Film ◽

Diffraction Peaks

ZnO thin films have attractive applications in photoelectric device, due to their excellent chemical, electrical and optical properties. In this paper, ZnO thin films with good c-axis preferred orientation and high transmittance are prepared on glass sheets by sol-gel immerse technique. The effects of withdrawal speeds on the growth process of thin film crystal, film crystal orientation and the crystallinity, the optical performance were investigated by XRD, SEM and UV-Vis spectrophotometry. The results show that the thin films were composed of better hexagonal wurtzite crystals with the c-axis prepared orientation. The transmittance of prepared thin films is over 80% in the visible-near IR region from 600 nm - 800 nm. ZnO films have sharp and narrow diffraction peaks, which indicates that the materials exhibit high crystallinity. With the withdrawal speeds increasing, the grain size of ZnO thin films and the intensity for all diffraction peaks were increased gradually. The growth model is changed from the stratified structure into the island structure in the growth process. The transmittance of the thin films decrease in the visible wavelength region, with the withdrawal speeds increasing.

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Tensile Testing of Single-Crystal Silicon Thin Films at 600 oC Using Infrared Radiation Heating

Sensors and Materials ◽

10.18494/sam.2010.619 ◽

2010 ◽

pp. 1

Keyword(s):

Thin Films ◽

Single Crystal ◽

Infrared Radiation ◽

Tensile Testing ◽

Single Crystal Silicon ◽

Radiation Heating ◽

Crystal Silicon ◽

Silicon Thin Films

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Effects of Annealing Atmosphere on the Optoelectrical Properties of ZnO Thin Films Grown by Atomic Layer Deposition

Materials Science Forum ◽

10.4028/www.scientific.net/msf.510-511.670 ◽

2006 ◽

Vol 510-511 ◽

pp. 670-673 ◽

Cited By ~ 2

Author(s):

Chong Mu Lee ◽

Yeon Kyu Park ◽

Anna Park ◽

Choong Mo Kim

Keyword(s):

Thin Films ◽

Atomic Layer Deposition ◽

Atomic Layer ◽

Xrd Analysis ◽

Nitrogen Atmosphere ◽

Zno Thin Films ◽

Zno Films ◽

Annealing Atmosphere ◽

Zno Film ◽

Layer Deposition

This paper investigated the effects of annealing atmosphere on the carrier concentration, carrier mobility, electrical resistivity, and PL characteristics as well as the crystallinity of ZnO films deposited on sapphire substrates by atomic layer deposition (ALD). X-ray diffraction (XRD) and photoluminescence (PL) analyses, and Hall measurement were performed to investigate the crystallinity, optical properties and electrical properties of the ZnO thin films, respectively. According to the XRD analysis results, the crystallinity of the ZnO film annealed in an oxygen atmosphere is better than that of the ZnO film annealed in a nitrogen atmosphere. It was found that annealing undoped ZnO films grown by ALD at a high temperature above 600°C improves the crystallinity and enhances UV emission.

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