Showing papers in "Journal of Vacuum Science & Technology B in 2018"

Future prospects of fluoride based upconversion nanoparticles for emerging applications in biomedical and energy harvesting

Abstract: Rare earth doped/codoped phosphors have been extensively studied for different types of applications based on their intense luminescence features. For this, researchers have tried to choose the inorganic host matrices having both a low phonon cut-off frequency and a high refractive index. Many articles have been published on oxide based phosphor materials, but due to their high cut-off phonon frequency, use of these materials is restricted for optical based applications. This is why additional research has been carried out on fluoride based host materials because of their low phonon frequencies, low composition degradation, and high quantum efficiency. In this paper, the authors review the rare earth fluoride based host nano- and micromaterials for different applications and discuss possible mechanisms.Rare earth doped/codoped phosphors have been extensively studied for different types of applications based on their intense luminescence features. For this, researchers have tried to choose the inorganic host matrices having both a low phonon cut-off frequency and a high refractive index. Many articles have been published on oxide based phosphor materials, but due to their high cut-off phonon frequency, use of these materials is restricted for optical based applications. This is why additional research has been carried out on fluoride based host materials because of their low phonon frequencies, low composition degradation, and high quantum efficiency. In this paper, the authors review the rare earth fluoride based host nano- and micromaterials for different applications and discuss possible mechanisms.

Reactive sputter deposition of piezoelectric Sc0.12Al0.88N for contour mode resonators

Abstract: Substitution of Al by Sc has been predicted and demonstrated to improve the piezoelectric response in AlN for commercial market applications in radio frequency filter technologies. Although cosputtering with multiple targets have achieved Sc incorporation in excess of 40%, industrial processes requiring stable single target sputtering are currently limited. A major concern with sputter deposition of ScAl is the control over the presence of non-c-axis oriented crystal growth, referred to as inclusions here, while simultaneously controlling film stress for suspended microelectromechanical systems (MEMS) structures. This work describes 12.5% ScAl single target reactive sputter deposition process and establishes a direct relationship between the inclusion occurrences and compressive film stress allowing for the suppression of the c-axis instability on silicon (100) and Ti/TiN/AlCu seeding layers. An initial high film stress, for suppressing inclusions, is then balanced with a lower film stress deposition to control total film stress to prevent Euler buckling of suspended MEMS devices. Contour mode resonators fabricated using these films demonstrate effective coupling coefficients up to 2.7% with figures of merit of 42. This work provides a method to establish inclusion free films in ScAlN piezoelectric films for good quality factor devices.Substitution of Al by Sc has been predicted and demonstrated to improve the piezoelectric response in AlN for commercial market applications in radio frequency filter technologies. Although cosputtering with multiple targets have achieved Sc incorporation in excess of 40%, industrial processes requiring stable single target sputtering are currently limited. A major concern with sputter deposition of ScAl is the control over the presence of non-c-axis oriented crystal growth, referred to as inclusions here, while simultaneously controlling film stress for suspended microelectromechanical systems (MEMS) structures. This work describes 12.5% ScAl single target reactive sputter deposition process and establishes a direct relationship between the inclusion occurrences and compressive film stress allowing for the suppression of the c-axis instability on silicon (100) and Ti/TiN/AlCu seeding layers. An initial high film stress, for suppressing inclusions, is then balanced with a lower film stress deposition to c...

Self-assembly of (111)-oriented tensile-strained quantum dots by molecular beam epitaxy

Abstract: The authors report on a comprehensive study of the growth of coherently strained GaAs quantum dots (QDs) on (111) surfaces via the Stranski–Krastanov (SK) self-assembly mechanism. Recent reports indicate that the long-standing challenges, whereby the SK growth mechanism could not be used to synthesize QDs on (111) surfaces, or QDs under tensile strain, have been overcome. However, a systematic study of the SK growth of (111)-oriented, tensile-strained QDs (TSQDs) as a function of molecular beam epitaxy growth parameters is still needed. Here, the authors explore the effects of deposition amount, substrate temperature, growth rate, and V/III flux ratio on the SK-driven self-assembly of GaAs(111)A TSQDs. The authors highlight aspects of TSQD SK self-assembly on (111) surfaces that appear to differ from the SK growth of traditional compressively strained QDs on (100) surfaces. The unique properties of (111) QDs and tensile-strained QDs mean that they are of interest for various research areas. The results discussed here offer a practical guide for tailoring the size, shape, density, uniformity, and photon emission wavelength and intensity of (111) TSQDs for future applications.

Beyond equilibrium thermodynamics in the low temperature plasma processor

Abstract: Low temperature plasmas are open driven thermodynamic systems capable of increasing the free energy of the mass that flows through them. An interesting thing about low temperature plasmas is that different species have different temperatures at the same location in space. Since thermal equilibrium cannot be assumed, many of the familiar results of equilibrium thermodynamics cannot be applied in their familiar form to predict, e.g., the direction of a chemical reaction. From the perspective of classical processing governed by thermal equilibrium, examples of highly unexpected gas-phase chemical reactions (CO2 dissociation, NO, N2H4, O3 synthesis) and solid material transformations (surface activation, size-focusing, and hyperdoping) promoted by low temperature plasmas are presented. The lack of a known chemical reaction equilibrium criterion prevents assessment of predictive kinetics models of low temperature plasmas, to ensure that they comply with the laws of thermodynamics. There is a need for a general method to predict chemical reaction equilibrium in low temperature plasmas or an alternative method to establish the thermodynamic admissibility of a proposed kinetics model. Toward those ends, two ideas are explored in this work. The first idea is that chemical reactions in low temperature plasmas proceed toward a thermal equilibrium state at an effective temperature intermediate between the neutral gas temperature and the electron temperature. The effective temperature hypothesis is simple, and surprisingly is adequate for elucidation in some systems, but it lacks generality. The general equation for nonequilibrium reversible–irreversible coupling (GENERIC) is a general beyond equilibrium thermodynamics framework that can be used to rigorously establish the thermodynamic admissibility of a set of dynamic modeling equations, such as a kinetic model, without knowledge of the final state that the system is tending toward. The use of GENERIC is described by way of example using a two-temperature hydrodynamic model from the literature. The conclusion of the GENERIC analysis presented in this work is that the concept of superlocal equilibrium is thermodynamically admissible and may be applied to describe low temperature plasmas, provided that appropriate terms are included for exchange of internal energy and momentum between different species that may have different temperatures and bulk velocities at the same location in space. The concept of superlocal equilibrium is expected to be of utility in future work focused on deriving equilibrium criteria for low temperature plasmas.

Fabrication and replication of re-entrant structures by nanoimprint lithography methods

Abstract: In this work, the authors present and demonstrate a simple method to fabricate and mass replicate re-entrant structures. The method consists of the direct imprinting of polymer mushroomlike microstructures produced by a combination of photolithography and nickel up-plating process. In particular, they have studied the conditions to generate highly robust mushroomlike topographies and their topographical impact on the replication process. They discuss all the imprinting conditions suitable to replicate such topographies using both ultraviolet light assisted nanoimprint lithography (UV-NIL) and thermal NIL methods in two polymer films, poly(methyl methacrylate) and polypropylene, and a hybrid (organic–inorganic) UV light curable photoresist, namely, Ormocomp. Re-entrant topographies have been widely studied for liquid/oil repelling and dry adhesive properties, whereas in their experiments, they have proved evidence for their amphiphobic potential.In this work, the authors present and demonstrate a simple method to fabricate and mass replicate re-entrant structures. The method consists of the direct imprinting of polymer mushroomlike microstructures produced by a combination of photolithography and nickel up-plating process. In particular, they have studied the conditions to generate highly robust mushroomlike topographies and their topographical impact on the replication process. They discuss all the imprinting conditions suitable to replicate such topographies using both ultraviolet light assisted nanoimprint lithography (UV-NIL) and thermal NIL methods in two polymer films, poly(methyl methacrylate) and polypropylene, and a hybrid (organic–inorganic) UV light curable photoresist, namely, Ormocomp. Re-entrant topographies have been widely studied for liquid/oil repelling and dry adhesive properties, whereas in their experiments, they have proved evidence for their amphiphobic potential.

Evaluation of electron optics with an offset cylindrical lens: Application to a monochromator or energy analyzer

Abstract: Electron beam monochromators (MCs) and energy analyzers (EAs), which are equivalent optical units with energy filtering capabilities, are of importance in electron microscopy and surface analysis instruments. The authors report the evaluation results for electron optics with an offset cylindrical lens (CL) and an additional transfer lens (TL) for application to an MC or EA. The offset CL deflects beams and generates energy dispersions, and the TL enhances their performance through collimating and retarding the beams. Following the previous theoretical studies, the authors have designed and manufactured the optics with a high mechanical accuracy at the micrometer level and integrated it with electronics with low noise and high stability. The authors adopt two methods for evaluating the energy-resolving performance. First, the authors treat the optics as an EA and evaluate the resolution through comparing the measured total energy distributions of Schottky emitters with the results from the theory. The energy resolution dE is estimated to be 88 meV at a beam energy E0 of 3.1 keV, and the index of performance dE/E0 reaches 2.7 × 10−5. Second, the authors treat the optics as an MC and evaluate directly the energy resolution or the energy spread of the monochromatic beams with an additional EA on the downstream side. The energy resolution dE is 73 meV. Both methods show similar energy resolutions, which enhance the credibility of the evaluation results. Charged particle simulation confirms the results and reveals that the resolution is limited by the width of the energy selection slit. As a total measurement system, the accuracy and stability are better than 3 meV. The MC with the optics exhibits high potential and a simple structure and is suitable for practical use. Advantages of the EA are band-pass filtering type, linear optics, compact size, and easy integration into analytical systems. The MC or EA using the optics will open new possibilities in the research fields of materials science, biology, and electronic devices, where advanced EMs or surface analytical instruments play essential roles.Electron beam monochromators (MCs) and energy analyzers (EAs), which are equivalent optical units with energy filtering capabilities, are of importance in electron microscopy and surface analysis instruments. The authors report the evaluation results for electron optics with an offset cylindrical lens (CL) and an additional transfer lens (TL) for application to an MC or EA. The offset CL deflects beams and generates energy dispersions, and the TL enhances their performance through collimating and retarding the beams. Following the previous theoretical studies, the authors have designed and manufactured the optics with a high mechanical accuracy at the micrometer level and integrated it with electronics with low noise and high stability. The authors adopt two methods for evaluating the energy-resolving performance. First, the authors treat the optics as an EA and evaluate the resolution through comparing the measured total energy distributions of Schottky emitters with the results from the theory. The ener...

Monolithic integration of patterned BaTiO3 thin films on Ge wafers

Abstract: Titanates exhibit electronic properties highly desirable for field effect transistors such as very high permittivity and ferroelectricity. However, the difficulty of chemically etching titanates hinders their commercial use in device manufacturing. Here, the authors report the selective area in finestra growth of highly crystalline BaTiO3 (BTO) within photolithographically defined openings of a sacrificial SiO2 layer on a Ge (001) wafer by molecular beam epitaxy. After the BaTiO3 deposition, the sacrificial SiO2 can be etched away, revealing isolated nanoscale gate stacks circumventing the need to etch the titanate thin film. Reflection high-energy electron diffraction in conjunction with scanning electron microscopy is carried out to confirm the crystallinity of the samples. X-ray diffraction is performed to determine the out-of-plane lattice constant and crystal quality of the BTO film. Electrical measurements are performed on electrically isolated Pt/BaTiO3/SrTiO3/Ge capacitor devices.Titanates exhibit electronic properties highly desirable for field effect transistors such as very high permittivity and ferroelectricity. However, the difficulty of chemically etching titanates hinders their commercial use in device manufacturing. Here, the authors report the selective area in finestra growth of highly crystalline BaTiO3 (BTO) within photolithographically defined openings of a sacrificial SiO2 layer on a Ge (001) wafer by molecular beam epitaxy. After the BaTiO3 deposition, the sacrificial SiO2 can be etched away, revealing isolated nanoscale gate stacks circumventing the need to etch the titanate thin film. Reflection high-energy electron diffraction in conjunction with scanning electron microscopy is carried out to confirm the crystallinity of the samples. X-ray diffraction is performed to determine the out-of-plane lattice constant and crystal quality of the BTO film. Electrical measurements are performed on electrically isolated Pt/BaTiO3/SrTiO3/Ge capacitor devices.

Improving the resolution and throughput of achromatic Talbot lithography

Abstract: High-resolution patterning of periodic structures over large areas has several applications in science and technology. One such method, based on the long-known Talbot effect observed with diffraction gratings, is achromatic Talbot lithography (ATL). This method offers many advantages over other techniques, such as high resolution, large depth-of-focus, and high throughput. Although the technique has been studied in the past, its limits have not yet been explored. Increasing the efficiency and the resolution of the method is essential and might enable many applications in science and technology. In this work, the authors combine this technique with spatially coherent and quasimonochromatic light at extreme ultraviolet (EUV) wavelengths and explore new mask design schemes in order to enhance its throughput and resolution. They report on simulations of various mask designs in order to explore their efficiency. Advanced and optimized nanofabrication techniques have to be utilized to achieve high quality and efficient masks for ATL. Exposures using coherent EUV radiation from the Swiss light source have been performed, pushing the resolution limits of the technique for dense hole or dot patterning down to 40 nm pitch. In addition, through extensive simulations, alternative mask designs with rings instead of holes are explored for the efficient patterning of hole/dot arrays. They show that these rings exhibit similar aerial images to hole arrays, while enabling higher efficiency and thereby increased throughput for ATL exposures. The mask designs with rings show that they are less prone to problems associated with pattern collapse during the nanofabrication process and therefore are promising for achieving higher resolution.

Fabrication of long range surface plasmon waveguide biosensors in a low-index fluoropolymer

Abstract: The authors report the fabrication of long-range surface plasmon polariton biosensors consisting of thin narrow Au stripes embedded in a low refractive index fluoropolymer with etched fluidic channels. The fabrication process incorporates a sacrificial SiO2 channel etch stop layer to avoid waveguide damage and prevent channel over-etching, and an Al etch mask to minimize thermal cracking of the fluoropolymer during channel etching. Process details are reported along with fabrication results, and the optical and biosensing performance of the fabricated devices are demonstrated. The biosensors were tested for bulk sensitivity and bovine serum albumin (BSA) protein adsorption producing notable changes for solutions with different refractive indices (increment of 2 × 10−3) and a change in insertion loss of 0.1 dB as a monolayer of BSA forms on the device.The authors report the fabrication of long-range surface plasmon polariton biosensors consisting of thin narrow Au stripes embedded in a low refractive index fluoropolymer with etched fluidic channels. The fabrication process incorporates a sacrificial SiO2 channel etch stop layer to avoid waveguide damage and prevent channel over-etching, and an Al etch mask to minimize thermal cracking of the fluoropolymer during channel etching. Process details are reported along with fabrication results, and the optical and biosensing performance of the fabricated devices are demonstrated. The biosensors were tested for bulk sensitivity and bovine serum albumin (BSA) protein adsorption producing notable changes for solutions with different refractive indices (increment of 2 × 10−3) and a change in insertion loss of 0.1 dB as a monolayer of BSA forms on the device.

Broadband UV-assisted thermal annealing of low-k silicon carbonitride films using a C-rich silazane precursor

Abstract: Low-k dielectric silicon carbonitride (SiCxNy) films are deposited by plasma-enhanced chemical vapor deposition using a carbon-rich silazane precursor, N-methyl-aza-2,2,4-trimethylsilacyclopentane (SiC7NH17), at 100 °C. The post-treatments of SiCxNy films are carried out by thermal annealing and a broadband UV-assisted thermal annealing (UV-annealing) at 400 °C for 5 min. Compared to the thermal annealing treatment, UV-annealing can improve both dielectric and mechanical properties of low-k SiCxNy films. Under thermal annealing, SiCxNy films show great thermal stability, but little structural change. In contrast, upon UV-annealing, most of the Si–H and N–H bonds are broken up, which induces more Si–N cross-linking and converts Si–C matrix into Si–N matrix. The ethylene bridges in Si–(CH2)2–Si also remain intact, but the unbridged hydrocarbons in Si–(CH2)2–N and Si–CH2–CH3 bonds decompose completely during the UV-annealing process. These account for the reduced dielectric constant to k = 3.2 from 3.6 and a...

Dry etch damage in n-type crystalline silicon wafers assessed by deep-level transient spectroscopy and minority carrier lifetime

Abstract: This paper compares the electrically active damage in dry-etched n-type float-zone silicon, using NF3/Ar or H2-plasma exposure and assessed by deep-level transient spectroscopy (DLTS) and recombination lifetime analysis. It is shown that the NF3/Ar-plasma damage consists of at least four different types of electron traps in the upper half of the band gap, which can be associated with vacancy- and vacancy-impurity-related complexes. In the case of H2-plasma damage, it is believed that the accumulation of point defects results in a gradual disordering of the near-surface layer. These defect levels also act as recombination centers, judged by the fact that they degrade the minority carrier lifetime. It is finally shown that lifetime measurements are more sensitive to the etching-induced damage than DLTS.This paper compares the electrically active damage in dry-etched n-type float-zone silicon, using NF3/Ar or H2-plasma exposure and assessed by deep-level transient spectroscopy (DLTS) and recombination lifetime analysis. It is shown that the NF3/Ar-plasma damage consists of at least four different types of electron traps in the upper half of the band gap, which can be associated with vacancy- and vacancy-impurity-related complexes. In the case of H2-plasma damage, it is believed that the accumulation of point defects results in a gradual disordering of the near-surface layer. These defect levels also act as recombination centers, judged by the fact that they degrade the minority carrier lifetime. It is finally shown that lifetime measurements are more sensitive to the etching-induced damage than DLTS.

In situ voltage-application system for active voltage contrast imaging in helium ion microscope

Abstract: In this study, the authors present a new method for electrical potential observation in which helium ion microscope (HIM) observations can be performed while applying a selected voltage (up to approximately +5 V) to a sample. The in situ voltage-application system is operated in a high vacuum HIM chamber and consists of a transfer rod, tilt joint, x-, y-, and z-axis mechanisms, and two probes at the end of the transfer rod. The new system was used to acquire a secondary electron (SE) images of the cross-sectional surfaces of a multilayer ceramic capacitor (MLCC) with voltages (from 0.5 to 5 V) applied to the internal electrodes of the MLCC. The active voltage contrast corresponding to the electrical potential in the SE images could be observed when the applied voltage was less than or equal to 1.5 V. This technique enables any voltage to be applied to the samples from outside the chamber and can be used to measure the nanometer-scale electrical potential distribution of Li-ion rechargeable batteries, solar cells, etc.In this study, the authors present a new method for electrical potential observation in which helium ion microscope (HIM) observations can be performed while applying a selected voltage (up to approximately +5 V) to a sample. The in situ voltage-application system is operated in a high vacuum HIM chamber and consists of a transfer rod, tilt joint, x-, y-, and z-axis mechanisms, and two probes at the end of the transfer rod. The new system was used to acquire a secondary electron (SE) images of the cross-sectional surfaces of a multilayer ceramic capacitor (MLCC) with voltages (from 0.5 to 5 V) applied to the internal electrodes of the MLCC. The active voltage contrast corresponding to the electrical potential in the SE images could be observed when the applied voltage was less than or equal to 1.5 V. This technique enables any voltage to be applied to the samples from outside the chamber and can be used to measure the nanometer-scale electrical potential distribution of Li-ion rechargeable batteries, sola...

Degradation of AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors under off-state electrical stress

Abstract: In this paper, the authors have fabricated AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors employing the low-pressure chemical vapor deposition (LPCVD) SiNx as the gate insulator with field plate structure and the long-term degradation was investigated under off-state stress with degradation process monitoring. The gate leakage and drain leakage under off-state electrical stress showed different change rules while the former was expected to be effectively suppressed by LPCVD-SiNx dielectric. The output and transfer characteristics between the stress were obtained periodically to investigate the degradation process. Through the analysis of the degradation of the parameters and the shifts of the Raman spectra, the inverse piezoelectric effect is believed to be the dominant degradation mechanism.

Effects of slow highly charged ion irradiation on metal oxide semiconductor capacitors

Abstract: Measurements were performed to characterize and better understand the effects of slow highly charged ion (HCI) irradiation, a relatively unexplored form of radiation, on metal oxide semiconductor (MOS) devices. Si samples with 50 nm SiO2 layers were irradiated with ion beams of ArQ+ (Q = 4, 8, and 11) at normal incidence. The effects of the irradiation were encapsulated with an array of Al contacts forming the MOS structure. High frequency capacitance–voltage (CV) measurements reveal that the HCI irradiation results in stretchout and shifting of the CV curve. These changes in the CV curve are attributed to dangling Si bond defects at the Si/SiO2 interface and trapped positive charge in the oxide, respectively. Charge state dependencies have been observed for these effects with the CV curve stretchout having a dependence of Q∼1.7 and the CV curve shifting with a dependence of Q∼1.8. These dependencies are similar to the results of previous studies focused on the Q-dependence of the stopping power of HCIs.

Block copolymer selectivity: A new dry etch approach for cylindrical applications

Abstract: A critical challenge for directed self-assembly of block copolymers is the selectivity between the two polymer phases. Polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) is one of the most studied block-copolymers to reach sub-20 nm patterns. A very high PMMA/PS selectivity (>10:1) is required to conserve a sufficient PS pattern thickness allowing pattern transfer to sublayers. In this paper, the authors propose to develop a chemistry allowing a full PMMA removal without PS consumption. It is based on CO and CO-H 2 cycles allowing to get a very high etch control. The proposed etch mechanisms have been understood thanks to x-ray photoelectron spectroscopy analyses performed on blanket wafers. Finally, this new etch process has been validated on the cylindrical PS-b-PMMA patterned structure. Published by the AVS.

In situliquid cell crystallization and imaging of thiamethoxam by helium ion microscopy

Abstract: Pest insect control is an essential component for crop protection and public health Neonicotinoids are a relatively new class of insecticides developed in the last four decades Thiamethoxam, a member of the neonicotinoid class, has shown outstanding potency for crop protection against a variety of piercing-sucking pests However, its use in industrial-volume packing and transportation is complicated by crystallization dynamics In this work, a helium ion microscope (HIM) with a Protochips liquid cell was utilized to crystallize and image thiamethoxam in situ The results of the study illustrate the growth and morphology of the thiamethoxam crystals at different He+ exposure doses, which is markedly different from what has been typically observed Energy-dispersive x-ray spectroscopy results confirm the presence of the thiamethoxam on the liquid cell membrane This imaging study illustrates the HIM ability to image and induce the crystallization in soft materials in liquid environments, and attempts to shed light onto the key processes involved in liquid imagingPest insect control is an essential component for crop protection and public health Neonicotinoids are a relatively new class of insecticides developed in the last four decades Thiamethoxam, a member of the neonicotinoid class, has shown outstanding potency for crop protection against a variety of piercing-sucking pests However, its use in industrial-volume packing and transportation is complicated by crystallization dynamics In this work, a helium ion microscope (HIM) with a Protochips liquid cell was utilized to crystallize and image thiamethoxam in situ The results of the study illustrate the growth and morphology of the thiamethoxam crystals at different He+ exposure doses, which is markedly different from what has been typically observed Energy-dispersive x-ray spectroscopy results confirm the presence of the thiamethoxam on the liquid cell membrane This imaging study illustrates the HIM ability to image and induce the crystallization in soft materials in liquid environments, and attempts to s

Integration of microwave-annealed oxidation on germanium metal-oxide-semiconductor devices

Abstract: In this paper, a method that entails using microwave thermal oxidation to form a high-quality gate dielectric on Ge through surface passivation at considerably low temperatures (<400 °C) is presented. Formation of the GeOx layer was confirmed by x-ray photoelectron spectroscopy. To reduce the bulk trap density and interface trap density (Dit), microwave thermal oxidation was employed for postdeposition microwave thermal oxidation after the deposition of Al2O3 through atomic layer deposition. Tiny frequency dispersion in capacitance measurement and a low Dit value of 5.9 × 1011 cm−2 eV−1 near the midgap confirmed a desirable passivation effect, which was favorable in mitigating the formation of dangling bonds on the Ge surface. A small hysteresis in capacitance was also observed, suggesting that the bulk dielectric was of high quality. On the basis of these characteristics, microwave-activated GeOx is a promising passivation layer material for aggressively scaled Ge-related metal oxide semiconductor devices.In this paper, a method that entails using microwave thermal oxidation to form a high-quality gate dielectric on Ge through surface passivation at considerably low temperatures (<400 °C) is presented. Formation of the GeOx layer was confirmed by x-ray photoelectron spectroscopy. To reduce the bulk trap density and interface trap density (Dit), microwave thermal oxidation was employed for postdeposition microwave thermal oxidation after the deposition of Al2O3 through atomic layer deposition. Tiny frequency dispersion in capacitance measurement and a low Dit value of 5.9 × 1011 cm−2 eV−1 near the midgap confirmed a desirable passivation effect, which was favorable in mitigating the formation of dangling bonds on the Ge surface. A small hysteresis in capacitance was also observed, suggesting that the bulk dielectric was of high quality. On the basis of these characteristics, microwave-activated GeOx is a promising passivation layer material for aggressively scaled Ge-related metal oxide semiconductor devices.