The current techniques used for the fabrication of nanosteps are normally done by layer growth and then ion beam thinning. There are also extra films grown on the step surfaces in order to reduce the roughness. So the...The current techniques used for the fabrication of nanosteps are normally done by layer growth and then ion beam thinning. There are also extra films grown on the step surfaces in order to reduce the roughness. So the whole process is time consuming. In this paper, a nanoscale step height structure is fabricated by atomic layer deposition （ALD） and wet etching techniques. According to the traceable of the step height value, the fabrication process is controllable. Because ALD technology can grow a variety of materials, aluminum oxide （Al2O3） is used to fabricate the nanostep. There are three steps of Al2O3 in this structure including 8 nm, 18 nm and 44 inn. The thickness of Al2O3 film and the height of the step are measured by anellipsometer. The experimental results show that the thickness of Al2O3 film is consistent with the height of the step. The height of the step is measured by AFM. The measurement results show that the height is related to the number of cycles of ALD and the wet etching time. The bottom and the sidewall surface roughness are related to the wet etching time. The step height is calibrated by Physikaliseh-Technische Bundesanstalt （PTB） and the results were 7.5±1.5 nm, 15.5±2.0 nm and 41.8±2.1 nm, respectively. This research provides a method for the fabrication of step height at nanoscale and the nanostep fabricated is potential used for standard references.展开更多
Nonpolar （1120） GaN films are grown on the etched a-plane GaN substrates via metalorganic vapor phase epitaxy. High-resolution X-ray diffraction analysis shows great decreases in the full width at half maximum of th...Nonpolar （1120） GaN films are grown on the etched a-plane GaN substrates via metalorganic vapor phase epitaxy. High-resolution X-ray diffraction analysis shows great decreases in the full width at half maximum of the samples grown on etched substrates compared with those of the sample without etching, both on-axis and off-axis, indicating the reduced dislocation densities and improved crystalline quality of these samples. The spatial mapping of the E2 （high） phonon mode demonstrates the smaller line width with a black background in the wing region, which testifies the reduced dislocation densities and enhanced crystalline quality of the epitaxial lateral overgrowth areas. Raman scattering spectra of the E2 （high） peaks exhibit in-plane compressive stress for all the overgrowth samples, and the E2 （high） peaks of samples grown on etched substrates shift toward the lower frequency range, indicating the relaxations of in-plane stress in these GaN films. Furthermore, room temperature photoluminescence measurement demonstrates a significant decrease in the yellow-band emission intensity of a-plane GaN grown on etched templates, which also illustrates the better optical properties of these samples.展开更多
The etching and passivation processes of very long wavelength infrared(VLWIR)detector based on the InAs/GaSb/AlSb type-II superlattice have been studied.By studying the effect of each component in the citric acid solu...The etching and passivation processes of very long wavelength infrared(VLWIR)detector based on the InAs/GaSb/AlSb type-II superlattice have been studied.By studying the effect of each component in the citric acid solution(citric acid,phosphoric acid,hydrogen peroxide,deionized water),the best solution ratio is obtained.After comparing different passivation materials such as sulfide+SiO_(2),Al_(2)O_(3),Si_(3)N_(4) and SU8,it is found that SU8 passivation can reduce the dark current of the device to a greater degree.Combining this wet etching and SU8 passivation,the of VLWIR detector with a mesa diameter of 500μm is about 3.6Ω·cm^(2) at 77 K.展开更多
Diamond films have great potential for micro-electro-mechanical system（MEMS） application.For device realization,precise patterning of diamond films at micrometer scale is indispensable.In this paper,simple and facil...Diamond films have great potential for micro-electro-mechanical system（MEMS） application.For device realization,precise patterning of diamond films at micrometer scale is indispensable.In this paper,simple and facile methods will be demonstrated for smart patterning of diamond films,in which two etching techniques,i.e.,plasma dry etching and chemical wet etching（including isotropic-etching and anisotropic-etching） have been developed for obtaining diamond microstructures with different morphology demands.Free-standing diamond micro-gears and micro-combs were achieved as examples by using the experimental procedures.It is confirmed that as-designed diamond structures with a straight side wall and a distinct boundary can be fabricated effectively and efficiently by using such methods.展开更多
Based on the self-terminating thermal oxidation-assisted wet etching technique,two kinds of enhancement mode Al_(2)O_(3)/GaN MOSFETs(metal-oxide-semiconductor field-effect transistors)separately with sapphire substrat...Based on the self-terminating thermal oxidation-assisted wet etching technique,two kinds of enhancement mode Al_(2)O_(3)/GaN MOSFETs(metal-oxide-semiconductor field-effect transistors)separately with sapphire substrate and Si sub-strate are prepared.It is found that the performance of sapphire substrate device is better than that of silicon substrate.Comparing these two devices,the maximum drain current of sapphire substrate device(401 mA/mm)is 1.76 times that of silicon substrate device(228 mA/mm),and the field-effect mobility(μ_(FEmax))of sapphire substrate device(176 cm^(2)/V·s)is 1.83 times that of silicon substrate device(96 cm^(2)/V·s).The conductive resistance of silicon substrate device is 21.2Ω-mm,while that of sapphire substrate device is only 15.2Ω·mm,which is 61%that of silicon substrate device.The significant difference in performance between sapphire substrate and Si substrate is related to the differences in interface and border trap near Al_(2)O_(3)/GaN interface.Experimental studies show that(i)interface/border trap density in the sapphire substrate device is one order of magnitude lower than in the Si substrate device,(ii)Both the border traps in Al_(2)O_(3) dielectric near Al_(2)O_(3)/GaN and the interface traps in Al_(2)O_(3)/GaN interface have a significantly effect on device channel mobility,and(iii)the properties of gallium nitride materials on different substrates are different due to wet etching.The research results in this work provide a reference for further optimizing the performances of silicon substrate devices.展开更多
We present large-scale molecular dynamics(MD)simulations based on a neural network potential(NNP)to investigate alkaline wet etching of GaN,a process critical to nitride-based semiconductor fabrication.A Behler–Parri...We present large-scale molecular dynamics(MD)simulations based on a neural network potential(NNP)to investigate alkaline wet etching of GaN,a process critical to nitride-based semiconductor fabrication.A Behler–Parrinello-type NNP is trained on extensive DFT datasets to capture chemical reactions between GaN and KOH.Using temperature-accelerated dynamics,our NNP-MD simulations accurately reproduce experimentally observed structural modifications of GaN nanorods during etching.The etching simulations reveal surface-specific morphological evolution:pyramidal pits on the−c plane,truncated pyramids on the+c plane,and planar morphologies on non-polar m and a surfaces.We also identify key chemical reactions governing the etching mechanisms.Enhanced-sampling simulations provide free-energy profiles for Ga dissolution,which critically influences the etching rate.The−c,a,and m planes exhibit moderate activation barriers,confirming their etchability,while the+c surface shows a significantly higher barrier,indicating strong resistance.Wealso observe the formation of Ga-O-Ga bridges on etched surfaces,which may act as carrier traps.This work provides atomistic insights into the mechanisms and kinetics of GaN wet etching,offering guidance for the fabrication of nanostructures in advanced GaN-based electronic and display applications.展开更多
A 3-dB paired interference （PI） optical coupler in silicon-on-insulator （SOI） based on rib waveguides with trapezoidal cross section was designed with simulation by a modified finite-difference beam propagation me...A 3-dB paired interference （PI） optical coupler in silicon-on-insulator （SOI） based on rib waveguides with trapezoidal cross section was designed with simulation by a modified finite-difference beam propagation method （FD-BPM） and fabricated by potassium hydroxide （KOH） anisotropic chemical wet etching. Theoretically, tolerances of width, length, and port distance are more than 1, 100, and 1 μm, respectively. Smooth interface was obtained with the propagation loss of 1.1 dB/cm at the wavelength of 1.55 μm. The coupler has a good uniformity of 0.2 dB and low excess loss of less than 2 dB.展开更多
The appropriate wet etch process for the selective removal of TaN on the HfSiON dielectric with an amorphous-silicon（a-Si） hardmask is presented.SCI（NH4OH：H2O2：H2O）,which can achieve reasonable etch rates for me...The appropriate wet etch process for the selective removal of TaN on the HfSiON dielectric with an amorphous-silicon（a-Si） hardmask is presented.SCI（NH4OH：H2O2：H2O）,which can achieve reasonable etch rates for metal gates and very high selectivity to high-k dielectrics and hardmask materials,is chosen as the TaN etchant. Compared with the photoresist mask and the tetraethyl orthosilicate（TEOS） hardmask,the a-Si hardmask is a better choice to achieve selective removal of TaN on the HfSiON dielectric because it is impervious to the SC1 etchant and can be readily etched with NH4OH solution without attacking the TaN and the HfSiON film.In addition,the surface of the HfSiON dielectric is smooth after the wet etching of the TaN metal gate and a-Si hardmask removal,which could prevent device performance degradation.Therefore,the wet etching of TaN with the a-Si hardmask can be applied to dual metal gate integration for the selective removal of the first TaN metal gate deposition.展开更多
The wet etching properties ofa HfSiON high-k dielectric in HF-based solutions are investigated. HF-based solutions are the most promising wet chemistries for the removal of HfSiON, and etch selectivity of HF-based sol...The wet etching properties ofa HfSiON high-k dielectric in HF-based solutions are investigated. HF-based solutions are the most promising wet chemistries for the removal of HfSiON, and etch selectivity of HF-based solutions can be improved by the addition of an acid and/or an alcohol to the HF solution. Due to densification during annealing, the etch rate of HfSiON annealed at 900℃ for 30 s is significantly reduced compared with as-deposited HfSiON in HF-based solutions. After the HfSiON film has been completely removed by HF-based solutions, it is not possible to etch the interfacial layer and the etched surface does not have a hydrophobic nature, since N diffuses to the interface layer or Si substrate formation of SiN bonds that dissolves very slowly in HF-based solutions. Existing Si-N bonds at the interface between the new high-k dielectric deposit and the Si substrate may degrade the carrier mobility due to Coulomb scattering. In addition, we show that N2 plasma treatment before wet etching is not very effective in increasing the wet etch rate for a thin HfSiON film in our case.展开更多
Wet-etch etchants and the TaN film method for dual-metal-gate integration are investigated. Both HF/HN O3/H2O and NH4OH/H2O2 solutions can etch TaN effectively, but poor selectivity to the gate dielectric for the HF/H...Wet-etch etchants and the TaN film method for dual-metal-gate integration are investigated. Both HF/HN O3/H2O and NH4OH/H2O2 solutions can etch TaN effectively, but poor selectivity to the gate dielectric for the HF/HNO3/H2O solution due to HF being included in HF/HNO3/H2O, and the fact that TaN is difficult to etch in the NH4OH/H2O2 solution at the first stage due to the thin TaOxNy layer on the TaN surface, mean that they are difficult to individually apply to dual-metal-gate integration. A two-step wet etching strategy using the HF/HNO3/H2O solution first and the NH4OH/H2O2 solution later can fully remove thin TaN film with a photo-resist mask and has high selectivity to the HfSiON dielectric film underneath. High-k dielectric film surfaces are smooth after wet etching of the TaN metal gate and MOSCAPs show well-behaved C-V and Jg-Vg characteristics, which all prove that the wet etching of TaN has little impact on electrical performance and can be applied to dual-metal-gate integration technology for removing the first TaN metal gate in the PMOS region.展开更多
A novel wet etching method for AlGaN/GaN heterojunction structures is proposed using thermal oxidation f ollowed by wet etching in KOH solution.It is found that an AlGaN/GaN heterostructure after high temperature oxid...A novel wet etching method for AlGaN/GaN heterojunction structures is proposed using thermal oxidation f ollowed by wet etching in KOH solution.It is found that an AlGaN/GaN heterostructure after high temperature oxidation above 700℃could be etched off in a homothermal（70℃） KOH solution while the KOH solution had no etching effects on the region of the AlGaN/GaN heterostructure protected by a SiO_2 layer during the oxidation process.A groove structure with 150 nm step depth on an AlGaN/GaN heterostructure was formed after 8 h thermal oxidation at 900℃followed by 30 min treatment in 70℃KOH solution.As the oxidation time increases,the etching depth approaches saturation and the roughness of the etched surface becomes much better.The physical mechanism of this phenomenon is also discussed.展开更多
Mesa etching technology is considerably important in the Gunn diode fabrication process. In this paper we fabricate InP Gunn diodes with two different kinds of chlorine-based etchants for the mesa etching for comparat...Mesa etching technology is considerably important in the Gunn diode fabrication process. In this paper we fabricate InP Gunn diodes with two different kinds of chlorine-based etchants for the mesa etching for comparative study. We use two chlorine-based etchants, one is HCl-based solution （HC1/H3PO4）, and the other is Cl2-based gas mixture by utilizing inductively coupled plasma system （ICP）. The results show that the wet etching （HCl-based） offers low cost and approximately vertical sidewall, whilst ICP system （C12-based） offers an excellent and uniform vertical sidewall, and the over-etching is tiny on the top and the bottom of mesa. And the fabricated mesas of Gunn diodes have average etching rates of 0.6 p.m/min and 1.2 pm/min, respectively. The measured data show that the current of Gunn diode by wet etching is lower than that by ICP, and the former has a higher threshold voltage. It provides a low-cost and reliable method which is potentially applied to the fabrication of chip terahertz sources.展开更多
In this article, a detailed analysis of the wet- etching technique for AIGaN/GaN heterostructure using dry thermal oxidation followed by a wet alkali etching was performed. The experimental results show that the oxida...In this article, a detailed analysis of the wet- etching technique for AIGaN/GaN heterostructure using dry thermal oxidation followed by a wet alkali etching was performed. The experimental results show that the oxida- tion plays a key role in the wet-etching method and the etching depth is mainly determined by the oxidation tem- perature and time. The correlation of etching roughness with oxidation time and temperature was investigated. It is found that there exists a critical oxidation temperature in the oxidation process. Finally, a physical explanation of the oxidation procedure for A1GaN layer was given.展开更多
Wet etching characteristics of cubic GaN (c GaN) thin films grown on GaAs(001) by metalorganic vapor phase epitaxy (MOVPE) are investigated.The samples are etched in HCl,H 3PO 4,KOH aqueous solutions,and molten KOH...Wet etching characteristics of cubic GaN (c GaN) thin films grown on GaAs(001) by metalorganic vapor phase epitaxy (MOVPE) are investigated.The samples are etched in HCl,H 3PO 4,KOH aqueous solutions,and molten KOH at temperatures in the range of 90～300℃.It is found that different solution produces different etch figure on the surfaces of a sample.KOH based solutions produce rectangular pits rather than square pits.The etch pits elongate in 1 0] direction,indicating asymmetric etching behavior in the two orthogonal <110> directions.An explanation based on relative reactivity of the various crystallographic planes is employed to interpret qualitatively the asymmetric etching behavior.In addition,it is found that KOH aqueous solution would be more suitable than molten KOH and the two acids for the evaluation of stacking faults in c GaN epilayers. direction,indicating asymmetric etching behavior in the two orthogonal <110> directions.An explanation based on relative reactivity of the various crystallographic planes is employed to interpret qualitatively the asymmetric etching behavior.In addition,it is found that KOH aqueous solution would be more suitable than molten KOH and the two acids for the evaluation of stacking faults in c GaN epilayers.展开更多
The surface of a commercial Y3Al5O12：Ce^3＋ phosphor was modified by 99% NH_4F＋CH_3COOH solution in a supersonic bath with water temperature of 80 oC for 4 h. The scanning electron microscopy（SEM） results showed t...The surface of a commercial Y3Al5O12：Ce^3＋ phosphor was modified by 99% NH_4F＋CH_3COOH solution in a supersonic bath with water temperature of 80 oC for 4 h. The scanning electron microscopy（SEM） results showed that the edge angles were not as sharp as the unmodified particles and the flat surfaces turned rough with many micro-structures covered. Positron lifetime measurements quantitatively showed that surface defects were removed away by more than 50%. As a result, the photoluminescence determinations showed that the backscatter loss was reduced by 4.2% and the emission power was enhanced by 5.6% after the surface modification. The conversion efficiency was greatly improved from 47.3% to 51.1%, as presented by the fluorescence images. Therefore, it would be greatly helpful for the improvement of efficiency, transparency and stability of pc-LED. Moreover, this method was significantly suitable for mass production due to its easy operation and low cost.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.51175418)Major Research Program on Nanomanufacturing of National Natural Science Foundation of China(Grant No.91323303)+1 种基金Fund of the State Key Laboratory of Precision Measuring Technology and Instruments(Tianjin University and Tsinghua University)of China(Grant No.PIL1403)Collaborative Innovation Center of Suzhou Nano Science and Technology of China
文摘The current techniques used for the fabrication of nanosteps are normally done by layer growth and then ion beam thinning. There are also extra films grown on the step surfaces in order to reduce the roughness. So the whole process is time consuming. In this paper, a nanoscale step height structure is fabricated by atomic layer deposition （ALD） and wet etching techniques. According to the traceable of the step height value, the fabrication process is controllable. Because ALD technology can grow a variety of materials, aluminum oxide （Al2O3） is used to fabricate the nanostep. There are three steps of Al2O3 in this structure including 8 nm, 18 nm and 44 inn. The thickness of Al2O3 film and the height of the step are measured by anellipsometer. The experimental results show that the thickness of Al2O3 film is consistent with the height of the step. The height of the step is measured by AFM. The measurement results show that the height is related to the number of cycles of ALD and the wet etching time. The bottom and the sidewall surface roughness are related to the wet etching time. The step height is calibrated by Physikaliseh-Technische Bundesanstalt （PTB） and the results were 7.5±1.5 nm, 15.5±2.0 nm and 41.8±2.1 nm, respectively. This research provides a method for the fabrication of step height at nanoscale and the nanostep fabricated is potential used for standard references.
基金Project supported by the National Natural Science Foundation of China(Grant No.61204006)the Fundamental Research Funds for the Central Universities,China(Grant No.K50511250002)the National Key Science & Technology Special Project,China(Grant No.2008ZX01002-002)
文摘Nonpolar （1120） GaN films are grown on the etched a-plane GaN substrates via metalorganic vapor phase epitaxy. High-resolution X-ray diffraction analysis shows great decreases in the full width at half maximum of the samples grown on etched substrates compared with those of the sample without etching, both on-axis and off-axis, indicating the reduced dislocation densities and improved crystalline quality of these samples. The spatial mapping of the E2 （high） phonon mode demonstrates the smaller line width with a black background in the wing region, which testifies the reduced dislocation densities and enhanced crystalline quality of the epitaxial lateral overgrowth areas. Raman scattering spectra of the E2 （high） peaks exhibit in-plane compressive stress for all the overgrowth samples, and the E2 （high） peaks of samples grown on etched substrates shift toward the lower frequency range, indicating the relaxations of in-plane stress in these GaN films. Furthermore, room temperature photoluminescence measurement demonstrates a significant decrease in the yellow-band emission intensity of a-plane GaN grown on etched templates, which also illustrates the better optical properties of these samples.
基金supported by the National Basic Research Program of China(Grant Nos.2018YFA0209102 and 2019YFA070104)the National Natural Science Foundation of China(Grant Nos.61790581 and 61274013)the Key Research Program of the Chinese Academy of Sciences(Grant No.XDPB22)。
文摘The etching and passivation processes of very long wavelength infrared(VLWIR)detector based on the InAs/GaSb/AlSb type-II superlattice have been studied.By studying the effect of each component in the citric acid solution(citric acid,phosphoric acid,hydrogen peroxide,deionized water),the best solution ratio is obtained.After comparing different passivation materials such as sulfide+SiO_(2),Al_(2)O_(3),Si_(3)N_(4) and SU8,it is found that SU8 passivation can reduce the dark current of the device to a greater degree.Combining this wet etching and SU8 passivation,the of VLWIR detector with a mesa diameter of 500μm is about 3.6Ω·cm^(2) at 77 K.
基金supported by National Natural Science Foundation of China(No.60908023)the Open Project of State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials of China(No.Ilzxfkl9)
文摘Diamond films have great potential for micro-electro-mechanical system（MEMS） application.For device realization,precise patterning of diamond films at micrometer scale is indispensable.In this paper,simple and facile methods will be demonstrated for smart patterning of diamond films,in which two etching techniques,i.e.,plasma dry etching and chemical wet etching（including isotropic-etching and anisotropic-etching） have been developed for obtaining diamond microstructures with different morphology demands.Free-standing diamond micro-gears and micro-combs were achieved as examples by using the experimental procedures.It is confirmed that as-designed diamond structures with a straight side wall and a distinct boundary can be fabricated effectively and efficiently by using such methods.
基金Project supported by the Research on Key Techniques in Reliability of Low Power Sensor Chip for IOTIPS and the Technology Project of Headquarters,State Grid Corporation of China(Grant No.5700-202041397A-0-0-00).
文摘Based on the self-terminating thermal oxidation-assisted wet etching technique,two kinds of enhancement mode Al_(2)O_(3)/GaN MOSFETs(metal-oxide-semiconductor field-effect transistors)separately with sapphire substrate and Si sub-strate are prepared.It is found that the performance of sapphire substrate device is better than that of silicon substrate.Comparing these two devices,the maximum drain current of sapphire substrate device(401 mA/mm)is 1.76 times that of silicon substrate device(228 mA/mm),and the field-effect mobility(μ_(FEmax))of sapphire substrate device(176 cm^(2)/V·s)is 1.83 times that of silicon substrate device(96 cm^(2)/V·s).The conductive resistance of silicon substrate device is 21.2Ω-mm,while that of sapphire substrate device is only 15.2Ω·mm,which is 61%that of silicon substrate device.The significant difference in performance between sapphire substrate and Si substrate is related to the differences in interface and border trap near Al_(2)O_(3)/GaN interface.Experimental studies show that(i)interface/border trap density in the sapphire substrate device is one order of magnitude lower than in the Si substrate device,(ii)Both the border traps in Al_(2)O_(3) dielectric near Al_(2)O_(3)/GaN and the interface traps in Al_(2)O_(3)/GaN interface have a significantly effect on device channel mobility,and(iii)the properties of gallium nitride materials on different substrates are different due to wet etching.The research results in this work provide a reference for further optimizing the performances of silicon substrate devices.
基金supported by Samsung Electronics Co., Ltd (IO201214-08143-01)the Nano & Material Technology Development Program through the National Research Foundation of Korea (NRF) funded by Ministry of Science and ICT (RS-2024-00407995). We are grateful to Jisu Jung for the technical discussion.
文摘We present large-scale molecular dynamics(MD)simulations based on a neural network potential(NNP)to investigate alkaline wet etching of GaN,a process critical to nitride-based semiconductor fabrication.A Behler–Parrinello-type NNP is trained on extensive DFT datasets to capture chemical reactions between GaN and KOH.Using temperature-accelerated dynamics,our NNP-MD simulations accurately reproduce experimentally observed structural modifications of GaN nanorods during etching.The etching simulations reveal surface-specific morphological evolution:pyramidal pits on the−c plane,truncated pyramids on the+c plane,and planar morphologies on non-polar m and a surfaces.We also identify key chemical reactions governing the etching mechanisms.Enhanced-sampling simulations provide free-energy profiles for Ga dissolution,which critically influences the etching rate.The−c,a,and m planes exhibit moderate activation barriers,confirming their etchability,while the+c surface shows a significantly higher barrier,indicating strong resistance.Wealso observe the formation of Ga-O-Ga bridges on etched surfaces,which may act as carrier traps.This work provides atomistic insights into the mechanisms and kinetics of GaN wet etching,offering guidance for the fabrication of nanostructures in advanced GaN-based electronic and display applications.
基金This work was supported in part by the National Natural Science Foundation of China (No.60336010)the"973"Plan of China (No.G2000-03-66) the"863"Program of China (No.2002AA312060).
文摘A 3-dB paired interference （PI） optical coupler in silicon-on-insulator （SOI） based on rib waveguides with trapezoidal cross section was designed with simulation by a modified finite-difference beam propagation method （FD-BPM） and fabricated by potassium hydroxide （KOH） anisotropic chemical wet etching. Theoretically, tolerances of width, length, and port distance are more than 1, 100, and 1 μm, respectively. Smooth interface was obtained with the propagation loss of 1.1 dB/cm at the wavelength of 1.55 μm. The coupler has a good uniformity of 0.2 dB and low excess loss of less than 2 dB.
基金Project supported by the Special Funds for Major State Basic Research Project of China(No.2006CB302704)the National Natural Science Foundation of China(No.60776030)
文摘The appropriate wet etch process for the selective removal of TaN on the HfSiON dielectric with an amorphous-silicon（a-Si） hardmask is presented.SCI（NH4OH：H2O2：H2O）,which can achieve reasonable etch rates for metal gates and very high selectivity to high-k dielectrics and hardmask materials,is chosen as the TaN etchant. Compared with the photoresist mask and the tetraethyl orthosilicate（TEOS） hardmask,the a-Si hardmask is a better choice to achieve selective removal of TaN on the HfSiON dielectric because it is impervious to the SC1 etchant and can be readily etched with NH4OH solution without attacking the TaN and the HfSiON film.In addition,the surface of the HfSiON dielectric is smooth after the wet etching of the TaN metal gate and a-Si hardmask removal,which could prevent device performance degradation.Therefore,the wet etching of TaN with the a-Si hardmask can be applied to dual metal gate integration for the selective removal of the first TaN metal gate deposition.
基金supported by the Special Funds for Major State Basic Research Projects(No.2006CB302704)the National Natural Science Foundation of China(No.60776030).
文摘The wet etching properties ofa HfSiON high-k dielectric in HF-based solutions are investigated. HF-based solutions are the most promising wet chemistries for the removal of HfSiON, and etch selectivity of HF-based solutions can be improved by the addition of an acid and/or an alcohol to the HF solution. Due to densification during annealing, the etch rate of HfSiON annealed at 900℃ for 30 s is significantly reduced compared with as-deposited HfSiON in HF-based solutions. After the HfSiON film has been completely removed by HF-based solutions, it is not possible to etch the interfacial layer and the etched surface does not have a hydrophobic nature, since N diffuses to the interface layer or Si substrate formation of SiN bonds that dissolves very slowly in HF-based solutions. Existing Si-N bonds at the interface between the new high-k dielectric deposit and the Si substrate may degrade the carrier mobility due to Coulomb scattering. In addition, we show that N2 plasma treatment before wet etching is not very effective in increasing the wet etch rate for a thin HfSiON film in our case.
基金supported by the Special Funds for Major State Basic Research Projects(No.2006CB302704)the National Natural Science Foundation of China(No.60776030)
文摘Wet-etch etchants and the TaN film method for dual-metal-gate integration are investigated. Both HF/HN O3/H2O and NH4OH/H2O2 solutions can etch TaN effectively, but poor selectivity to the gate dielectric for the HF/HNO3/H2O solution due to HF being included in HF/HNO3/H2O, and the fact that TaN is difficult to etch in the NH4OH/H2O2 solution at the first stage due to the thin TaOxNy layer on the TaN surface, mean that they are difficult to individually apply to dual-metal-gate integration. A two-step wet etching strategy using the HF/HNO3/H2O solution first and the NH4OH/H2O2 solution later can fully remove thin TaN film with a photo-resist mask and has high selectivity to the HfSiON dielectric film underneath. High-k dielectric film surfaces are smooth after wet etching of the TaN metal gate and MOSCAPs show well-behaved C-V and Jg-Vg characteristics, which all prove that the wet etching of TaN has little impact on electrical performance and can be applied to dual-metal-gate integration technology for removing the first TaN metal gate in the PMOS region.
基金supported by the National Natural Science Foundation of China(Nos.60406004,60890193,60736033)the National Key Micrometer/Nanometer Processing Laboratory,China
文摘A novel wet etching method for AlGaN/GaN heterojunction structures is proposed using thermal oxidation f ollowed by wet etching in KOH solution.It is found that an AlGaN/GaN heterostructure after high temperature oxidation above 700℃could be etched off in a homothermal（70℃） KOH solution while the KOH solution had no etching effects on the region of the AlGaN/GaN heterostructure protected by a SiO_2 layer during the oxidation process.A groove structure with 150 nm step depth on an AlGaN/GaN heterostructure was formed after 8 h thermal oxidation at 900℃followed by 30 min treatment in 70℃KOH solution.As the oxidation time increases,the etching depth approaches saturation and the roughness of the etched surface becomes much better.The physical mechanism of this phenomenon is also discussed.
基金supported by the Main Direction Program of Knowledge Innovation of the Chinese Academy of Sciences(Grant No.2A2011YYYJ-1123)
文摘Mesa etching technology is considerably important in the Gunn diode fabrication process. In this paper we fabricate InP Gunn diodes with two different kinds of chlorine-based etchants for the mesa etching for comparative study. We use two chlorine-based etchants, one is HCl-based solution （HC1/H3PO4）, and the other is Cl2-based gas mixture by utilizing inductively coupled plasma system （ICP）. The results show that the wet etching （HCl-based） offers low cost and approximately vertical sidewall, whilst ICP system （C12-based） offers an excellent and uniform vertical sidewall, and the over-etching is tiny on the top and the bottom of mesa. And the fabricated mesas of Gunn diodes have average etching rates of 0.6 p.m/min and 1.2 pm/min, respectively. The measured data show that the current of Gunn diode by wet etching is lower than that by ICP, and the former has a higher threshold voltage. It provides a low-cost and reliable method which is potentially applied to the fabrication of chip terahertz sources.
基金financially supported by the National Natural Science Foundation of China (Nos. 60406004, 60890193, and 60736033)the National Key Micrometer/Nanometer Processing Laboratory
文摘In this article, a detailed analysis of the wet- etching technique for AIGaN/GaN heterostructure using dry thermal oxidation followed by a wet alkali etching was performed. The experimental results show that the oxida- tion plays a key role in the wet-etching method and the etching depth is mainly determined by the oxidation tem- perature and time. The correlation of etching roughness with oxidation time and temperature was investigated. It is found that there exists a critical oxidation temperature in the oxidation process. Finally, a physical explanation of the oxidation procedure for A1GaN layer was given.
文摘Wet etching characteristics of cubic GaN (c GaN) thin films grown on GaAs(001) by metalorganic vapor phase epitaxy (MOVPE) are investigated.The samples are etched in HCl,H 3PO 4,KOH aqueous solutions,and molten KOH at temperatures in the range of 90～300℃.It is found that different solution produces different etch figure on the surfaces of a sample.KOH based solutions produce rectangular pits rather than square pits.The etch pits elongate in 1 0] direction,indicating asymmetric etching behavior in the two orthogonal <110> directions.An explanation based on relative reactivity of the various crystallographic planes is employed to interpret qualitatively the asymmetric etching behavior.In addition,it is found that KOH aqueous solution would be more suitable than molten KOH and the two acids for the evaluation of stacking faults in c GaN epilayers. direction,indicating asymmetric etching behavior in the two orthogonal <110> directions.An explanation based on relative reactivity of the various crystallographic planes is employed to interpret qualitatively the asymmetric etching behavior.In addition,it is found that KOH aqueous solution would be more suitable than molten KOH and the two acids for the evaluation of stacking faults in c GaN epilayers.
基金Project supported by National Natural Science Foundation of China(11175049,51177017)
文摘The surface of a commercial Y3Al5O12：Ce^3＋ phosphor was modified by 99% NH_4F＋CH_3COOH solution in a supersonic bath with water temperature of 80 oC for 4 h. The scanning electron microscopy（SEM） results showed that the edge angles were not as sharp as the unmodified particles and the flat surfaces turned rough with many micro-structures covered. Positron lifetime measurements quantitatively showed that surface defects were removed away by more than 50%. As a result, the photoluminescence determinations showed that the backscatter loss was reduced by 4.2% and the emission power was enhanced by 5.6% after the surface modification. The conversion efficiency was greatly improved from 47.3% to 51.1%, as presented by the fluorescence images. Therefore, it would be greatly helpful for the improvement of efficiency, transparency and stability of pc-LED. Moreover, this method was significantly suitable for mass production due to its easy operation and low cost.
