Film Stack Structure Research Articles

CMP characteristics of IGZO thin film with a variety of process parameters

Recently, amorphous indium gallium zinc oxide (a-IGZO) has been studied in the field of 3D transistors as a channel material for high mobility, good uniformity, and low leakage current performance. The CMP process needs to be applied to fully remove surface IGZO in a multilayer film stack structure and achieve the purpose of planarization. As we all know, the CMP characteristics of the desired removal rate with stability and within-wafer non-uniformity (WIWNU%) play an important role in the CMP process. In this paper, the variation of the removal rate and the non-uniformity for IGZO thin film were studied with various process parameters (such as polishing time, slurry flow rate, slurry dilution, head pressure, head and table speed). The results mean that the removal rate and the non-uniformity of IGZO thin film can be tuned by changing process parameters, which can enhance the confidence about the feasibility of IGZO-CMP in the application of advanced technology.

Bend‐Resistant and Energy‐Friendly GO‐PVA/PVA Polymer Electret Synaptic Transistors for Neuromorphic Computations

AbstractPolymer electret synaptic transistor is a promising three‐terminal artificial synaptic device. In this work, the electrical characteristics of the composite insulator and transistor are enhanced by modulating the concentration of the 2D nanofiller graphene oxide (GO) and the stacked film structure based on a polyvinyl alcohol (PVA) matrix. The GO‐PVA/PVA polymer electret synaptic transistors before and after dynamic/static bending exhibit typical synaptic characteristics, including short‐term plasticity, long‐term plasticity, pair‐pulse facilitation, spike‐timing‐dependent plasticity, and “learning–forgetting–relearning” features. Importantly, the device exhibits good cycling stability, uniformity and linearity in the potentiation‐depression cycling test, which is beneficial for improving the accuracy of neuromorphic computations. Also, it shows extremely low energy consumption (≈0.32 fJ). The recognition accuracy of images is simulated based on the constructed artificial neural network, which achieves 86.8% for the MNIST dataset. In addition, the devices maintain high recognition accuracy after dynamic/static bending, indicating that the devices are extremely bend‐resistant. The GO‐PVA/PVA polymer electret synaptic transistor is expected to be a potential candidate for neuromorphic computations and electronic skin.

Electrical characteristics investigation of ferroelectric memories using stacked and mixed hafnium zirconium oxides

• Ferroelectric characteristics of mixed and stacked HfZrO devices were investigated. • Stacked HfZrO device showed a much stronger ferroelectricity than mixed one. • A surface nitrogen plasma treatment can alleviate ferroelectric domain pinning. • Nitrogen incorporation into stacked HfZrO further improved the endurance cycling. In this work, we investigate ferroelectric characteristics of hafnium zirconium oxide (HfZrO) metal-ferroelectric-metal (MFM) devices with mixed and stacked film structure. The experimental results reveal that the stacked HfZrO MFM device has a lower dynamic leakage and stronger ferroelectric polarization value of approximately 27.3 μC/cm 2 , which is much higher than 17.5 μC/cm 2 measured from mixed HfZrO MFM device. From endurance cycling test, we also confirm that the stacked HfZrO MFM capacitor with a remote nitrogen plasma treatment featuring a large initial hysteresis window can achieve a stable operation up to 10 8 cycles at an operating voltage of 2.5 V, which is even longer than that of mixed HfZrO MFM capacitor by one order of magnitude. Therefore, the stacked MFM structure with proper interface engineering provides a promising approach for the process integration of ferroelectric memory under the comprehensive consideration of device performance and endurance.

Visible-infrared (0.4–20 μ m) ultra-broadband absorber based on cascade film stacks

In this paper, we present a glass-based double-side cascade film stack structure for visible-infrared ultrabroadband absorption. The proposed structure demonstrates an average absorption as high as ∼95% over an ultrawide range of wavelengths from 0.4 μm to 20 μm. The high absorption feature of the different bandgap materials is applied in this absorption device to realize the ultrabroadband absorption, combining with the metal-dielectric-like configuration for those unmatched-admittance wavelengths and the graded index profile arrangement for the 0.4–2.5 μm band. The proposed ultrabroadband absorber shows a great angular tolerance up to 60° with the average absorption of 90% remaining. The proposed approach can have tremendous potential in fields of optical sensing, camouflage, optical imaging, passive cooling, and sustainable power generation, profiting from the good mechanical characteristics of this compact multilayer film structure and the low manufacture costs with the simple physical vapor deposition.

A comparative study of metal-ferroelectric-metal devices using doped- and stacked-hafnium zirconium oxides

To understand the effect of deposition sequence of ferroelectric HfZrO, we investigated the ferroelectric polarization characteristics of a 50%-zirconium-doped HfZrO and a stacked HfZrO metal-ferroelectric-metal capacitors. Based on experimental results, we find that the leakage current can be effectively suppressed in stacked HfZrO film. The film stack structure is favorable for simultaneously stabilizing the ferroelectric polarization and minimizing the generation of interface defect traps during the post-metal annealing process with a thermal budget of 600–800 °C, which is favorable for complementary-metal-oxide-semiconductor frond- and back-end process integration with various thermal budget requirement.

Novel Exploration of Flat-Band Voltage Manipulation by NPT for Advanced High-k/Metal-Gate CMOS Technology

Threshold voltage (VT) modulation is crucial for high performance (HP) and low power (LP) applications in the state-of-the-art FinFET and NanowireFET devices with gate-last HKMG integration scheme. Conventional metal-gate work function modulation normally requires a complicated film stack structure and a precise film thickness control in RMG (Replaced Metal Gate) process. As the physical gate length of RMG scaling down to below 14nm for sub-7nm technology node, the gap filling volume becomes rigorous and the VT tuning capability and turns inadequate for CMOS IC applications. This work presents a novel exploration of flat-band voltage (VFB) manipulation scheme with the nitrogen plasma treatment (NPT) in the high-k/metal-gate (HKMG) Metal-Oxide-Semiconductor Capacitor (MOSCAP) for the shrinking scaling of the further CMOS fabrication technology. HKMG formation is performed via ALD (Atomic Layer Deposition) and CVD (Chemical Vapor Deposition). The gate stacks of fabricated P- and N-MOSCAPs are ALD-HfO2(High-k layer, HK)/ALD-TiN(Capping layer)/ALD-TaN(Etch-stop layer, ESL)/CVD-TiN(Work-function layer, WFM)/ALD-W(Contacted metal) and ALD-HfO2(High-k layer, HK)/ALD-TiN(Capping layer)/ALD-TiAlC(Work-function layer, WFM)/ALD-TiN(Barrier layer)/ALD-W(Contacted metal), respectively. The critical NPT process is developed in chamber of EnduraTM (Applied Materials, Inc) and compatible to the mainstream gate-last HKMG technology. NPT process is applied in the first ALD-TiN capping layer both for P- and N-MOSCAPs. The developed NPT process on the first ALD-TiN capping layer demonstrates significant VFB modulation capability and causes a controllable effective work function of metal gate: 1) shifting to band center with increasing of the radio frequency powers both for P-/N-MOSCAPs; 2) shifting to opposite directions (P- to band edge, N- to band center) with reduced nitrogen flow ratio for P-/N-MOSCAPs; 3) shifting from -220mV to +60mV and from +130mV to +420mV for P-/N-MOSCAPs, respectively. Compared to the samples without NPT, the gate leakage current of both P- and N-MOSCAPs are improved with the NPT process. Based on the different gate stacks of P-/N-MOSCAPs and plasma effect, one unique physical model including N-vacancy/Al-trap effect is successfully proposed to illustrate the complicated shift behaviors both for HKMG P-/N-MOSCAPs. VFB shift for P-MOSCAP is mostly determined by N-vacancies, for the same layer of first capping layer(TiN) and work-function layer(TiN). The VFB shift for N-MOSCAP needs to consider both N-vacancies and Al-traps effect, for the difference between first capping layer(TiN) and the upper work-function layer(TiAlC). In conclusion, the technology of NPT in the first ALD-TiN capping layer of HKMG MOSCAPs for gate work function modulations is systematically investigated. Significant VFB shift values, such as -220mV/+130mV with different RF powers and +60mV/+420mV with different nitrogen flow ratios are achieved for P-/N-MOSCAPs, respectively. One simple theoretical model by employing the function of N-vacancy in ALD-TiN capping layer with the corresponding Al-trap effect by different WFM atoms in metal-gate is presented, which gives a unique physical explanation to the complex VFB manipulation behaviors with different device types and process conditions. The results demonstrate NPT process is one of the most promising technologies for the VT manipulation in future scaling CMOS technology nodes with less process cost. Figure 1

High resolution secondary ion mass spectrometry analysis of hydrogen behavior in SiO2/SiN/SiO2 films with thermal treatment

The distribution and behavior of hydrogen in a SiO2/SiN/SiO2 (ONO) film stack structure with thermal treatment were investigated by high-resolution secondary ion mass spectrometry analysis. Hydrogen atoms were present in the poly-Si/top-SiO2 interface, SiN layer, and bottom-SiO2/Si-substrate interface. These hydrogen atoms decreased in number with annealing (1000 °C, 60 s) and spike annealing (1000 °C, about 1 s). However, when a SiN cap layer with hydrogen atoms was formed on a poly-Si/ONO film structure, hydrogen atoms in the ONO film did not decrease in number with spike annealing. It was considered that the SiN cap layer mainly performed a supply source of hydrogen into the ONO film during spike annealing, and that hydrogen atoms interdiffused between the SiN cap layer and the SiN layer of the ONO film. These results indicate that the amount of hydrogen in the ONO film can be controlled by annealing and the formation of a SiN cap layer.

(AlCrTaTiZr)N/(AlCrTaTiZr)N 0.7 bilayer structure of high resistance to the interdiffusion of Cu and Si at 900 °C

In this study, a multi-component (AlCrTaTiZr)N/(AlCrTaTiZr)N 0.7 bilayer structure of about 15 nm thick was developed as a diffusion barrier material for Cu interconnects. The as-deposited (AlCrTaTiZr)N 0.7 layer was characterized to be an amorphous structure, and the (AlCrTaTiZr)N layer was a nanocomposite structure. After annealing at a high temperature of 900 °C, the Si/(AlCrTaTiZr)N/(AlCrTaTiZr)N 0.7/Cu film stack structure with the bilayer diffusion barrier remained stable. Only a slight amount of Cu penetrated into the top (AlCrTaTiZr)N 0.7 layer. However, neither interdiffusion of Cu and Si through the (AlCrTaTiZr)N layer occurred, nor did any silicides form, indicating the excellent diffusion resistance of the bilayer structure.

Characteristics of Ni–Ir and Pt–Ir hard coatings surface treated by pulsed Nd:YAG laser

The subjects of the presented paper are to develop a laser surface treatment technology for the protective coatings of glass-molding dies and to better understand the interaction between laser beam and materials coated on the die surface. A variety of alloy films, including Ir-25 at.% Pt, Ir-50 at.% Pt, Ir-75 at.% Pt, Ir-25 at.% Ni, Ir-50 at.% Ni, and Ir-75 at.% Ni compositions are deposited by the ion source assisted magnetron sputtering system (ISAMSS). A Cr layer that functioned as a buffer layer is deposited between the alloy film and die surface. After an alloy film and the buffer Cr layer were sequentially coated on tungsten carbide (WC) surface, Nd:YAG laser was directly applied in the writing process. The temperature profile of the film stack structure is simulated by ANSYS software. The surface roughness was analyzed by atomic force microscopy (AFM) to compare the coating surface roughness before and after the laser surface treatments. The treated coatings for oxidation prevention test were examined by energy dispersive x-ray spectrometry (EDS). Nanoindentation instrument was performed to evaluate microhardness and reduced modulus of the coatings. The cross-sectional structures between the hard coating layer and buffer layer were also inspected by a scanning electron microscope (SEM). The Pt–Ir and Ni–Ir film coatings are unable to withstand the working temperature over 1500°C, which is considered for quartz molding process and hot embossing process. The films showed high roughness, low microhardness and low reduced modulus because the film oxidation occurred in a high working temperature process.

Microfabrication of coupled fluid–structure systems with applications in acoustic sensing

A fabrication process for manufacturing coupled fluid–structure microsystems is described. This process allows production of a novel class of trapped-fluid acoustic sensors. The systems consist of wafer-thick fluid chambers bounded by arbitrarily shaped membranes. A stacked film structure of silicon nitride and boron doped polysilicon is used to reduce residual stresses in the membranes. Tin–gold fluxless solder bonding is used to fabricate capacitive structures which allow electrical sensing of membrane vibrations. An acoustic sensor fabricated using this process is demonstrated. An equivalent acoustic circuit model for the system is described, and models the low-frequency system response accurately. Experimental measurements of sensitivity, noise density, and linearity are presented.

Design of Multi-States Storage Medium for Phase Change Memory

A method has been introduced to realize multi-states storage in phase change memory (PCM) by using stacked phase change films with different amorphous resistivity. The amorphous resistivity of each phase change layer was selected to make the stacked films crystallize successively with the increase of current, and so obtain four resistance states. The thickness of each phase change layer was also optimized to ensure enough resistance difference between neighboring storage state. The thermal conduction simulation was performed, and the results indicate that the stacked Si–Sb–Te films with suitable composition, resistivity and thickness in each layer can crystallize successively with the increase of current and realize multi-states storage in PCM. A memory cell with stacked film structure (Si16Sb33Te51/Si4Sb46Te50/Si11Sb39Te50) was prepared. The film thicknesses of Si16Sb33Te51, Si4Sb46Te50 and Si11Sb39Te50 were optimized to be 40, 80, and 20 nm, respectively. The current–voltage (I–V) characteristics and the resistance–current (R–I) characteristics were measured. The results confirmed the four-state storage capability of the memory cell with this stacked film structure.

Study of SiOxNy as a bottom antireflective coating and its pattern transferring capability

To meet such challenges for the controlling of critical feature dimension at sub-50–100‐nm, it has been a general industrial trend to employ shorter wavelength (193nm, for example) lithography for better resolution and to use bottom antireflective coating (BARC) for a reduced standing wave formation and thus, a better critical dimensional control. Matching the optical constants (n,k) between the BARC, photoresist, and the underlayer to be patterned is critical for the elimination of such standing waves. SiOxNy and SiOxCy are two attractive inorganic BARC candidates in view of their easily adjustable optical constants by varying the deposition parameters and their etching compatibility with standard semiconductor plasma processes. In this article, SiOxNy films were prepared by plasma enhanced chemical vapor deposition approach. These films have been further characterized using x-ray photoelectron spectroscopy for chemical composition depth profile, Fourier transform infrared spectroscopy for local chemical bonding, and ellipsometry for optical constants. It has been demonstrated that the refractive indices of SiOxNy can be tuned from 1.6 to 2, while the absorption constants k can be adjusted from 0.1 to 0.9 by changing the process parameters, such as SiH4 flow rate, NH3 flow rate, and SiH4∕N2O ratio. To integrate the SiOxNy BARC film into the storage device manufacturing, the pattern transferring capability of SiOxNy has been discussed. A film stack structure of photoresist∕SiOxNy∕carbon or SiC hard mask∕magnetic device layer has been used to evaluate the performance of the SiOxNy BARC. SiOxNy film was opened via inductively coupled plasma etching with CHF3+O2 chemistry, while carbon and SiC hard masks were opened using He–O2 and SF6–He–O2 chemistries, respectively. SiF emission line at 388nm wavelength was used for end point during the SiOxNy etching, while the 778nm O peak and 685nm F peak have been used for carbon and SiC end pointing. The profiles of the etched SiOxNy and carbon∕SiC were analyzed by cross-section transmission electron microscopy.

Multiple-State Storage Capability of Stacked Chalcogenide Films(Si16Sb33Te51/Si4Sb45Te51/Si11Sb39Te50) for Phase Change Memory

The multiple-state storage capability of phase change memory (PCM) isconfirmed by using stacked chalcogenide films as the storage medium.The current–voltage characteristics and the resistance–currentcharacteristics of the PCM clearly indicate that four states can bestored in this stacked film structure. Qualitative analysis indicatesthat the multiple-state storage capability of this stacked filmstructure is due to successive crystallizations in different Si–Sb–Telayers triggered by different amplitude currents.

Fabrication and characterization of granular-type (FePt∕Fe3Pt)- and (FePt∕fcc FePt)-tilted magnetic recording media

The magnetic properties of tilted media with a film stack structure of [(fccFePtxnm) or (Fe3Ptynm)]∕FePt∕MgO∕FePt∕MgO4nm∕SiO24nm∕glass were investigated. The angular dependence of coercivity from the film normal to the in plane exhibits a broad peak in the case of Fe3Pt, implying the tilt of the easy axis from the film normal. The coercivity of the media with a hard layer decreases by about 50% from its initial value with an increase in Fe3Pt layer thickness. However, the media with fcc FePt exhibit about a 70% decrease in coercivity for layer thickness up to 3 nm. There is not much change in the α[=4π(dM∕dH)H=Hc] value (α∼2–3) with an increase in the Fe3Pt layer thickness.

Stacked chalcogenide layers used as multi-state storage medium for phase change memory

The multi-state storage capability of phase-change memory (PCM) was confirmed by using stacked chalcogenide layers as storage medium. The stacked films were prepared by stacking a pure Ge2Sb2Te5 (GST) layer, a tungsten layer and a silicon-doped GST layer. The electrical properties of the stacked films were also investigated. The results show that there are two negative differential resistance areas in the current-voltage (I–V) curve and three steps with three relatively stable resistance values in the resistance-voltage (R–V) curve, which indicate that the multi-state storage of PCM can be realized by using this stacked film structure. Qualitative analysis reveals that the multi-state storage capability of this stacked film structure is due to the successive crystallizations in a silicon-doped GST layer and a pure GST layer.

High-Power, Double-Sided Drive Type Electrostatic Motor with Stacked-Film Structure

高出力な両面駆動形積層静電モータを開発した. 従来研究におけるフィルム形静電モータの移動子・固定子フィルムは, それぞれの表面同士を対向させた場合にのみ推力を得ることが可能であったが, 本研究では裏面でも推力を生成可能なフィルムを新たに設計・試作し, その有用性を確認した. 試作したフィルムを積層した静電モータの推力は駆動電圧1.4kV0-p印加時に約3.5Wの出力を生成し, 効率は最大約46%を得た.

Hydrogen-related mobile charge in the phosphosilicate glass–SiO2–Si structure

This article demonstrates that mobile charge, Qm, of a nonsodium nature may exist in the thin film stack structure of phosphosilicate glass–SiO2–Si. The behavior of the Qm in this structure has been investigated using noncontact corona charging of the dielectric surface and measurement of the surface potential with a contact potential difference, probe. Qm levels greater than 1012 cm−2 have been measured in as-deposited samples whereas high temperature anneal reduced this level by half. The nonsodium nature of Qm was confirmed by surface analysis measurement. A model based on hydrogen cycling between the two interfaces of a buried oxide layer is used to explain the observed results. The experimental data suggest that charge traps exist at each interface of the buried oxide and that they control the charge release allowing it to move to the opposite interface. The activation energy for charge release from these traps depends on the nature of the interface with the lowest energy estimated near 0.22 eV.

The use of experimental design techniques to meet reflected color targets in pyrolytic low emissivity coatings

Low emissivity coatings are common in architectural applications and the marketplace dictates an increasingly complex set of process and optical requirements. The coatings must reflect infrared light, and, simultaneously, must have little or no visible reflected color. The first step in commercializing a new coated product is to develop a theoretical thin film stack that meets the target optical requirements while incorporating real-world materials and production requirements. The experimental design process requires a definition of the input or control factors (determined by the process and economics) and a clearly defined target response (determined by the marketplace). In the application of experimental design to thin film modeling, the control factors are the refractive indices and thicknesses of the various coating layers. The target responses are gross properties of the coated glass product, such as its reflected color and emissivity. The infinite combination of layer thicknesses and refractive indices are represented by a simple empirical model that quantifies the responses with minimal test cases or experiments. The models can then be used to find a workable solution for the design problem and provide insight into the macroscopic behavior of the color as a function of the film stack structure.

Heterodyne mixing with a sandwich-type Josephson junction using a Bi-based high- oxide superconductor

A sandwich-type high- Josephson junction coupled with a coplanar-type transmission line was fabricated and heterodyne mixing characteristics were investigated. The junction was fabricated from a stacked film structure of (BSCCO/BSNCO/BSCCO) and the transmission line was made of sputter-deposited Pt film. The junction had a rectangular shape of . Current - voltage (I - V) curves of the junction showed weak-link-type characteristics. Two microwave sources of a frequency synthesizer and a sweep oscillator were used as a local oscillator (LO: 20 GHz) and a radio frequency signal source (RF: 19 GHz) for heterodyne mixing experiments. Intermediate signal (IF: 1 GHz) was transmitted through the transmission line and detected by a power meter. The conversion efficiency of -44 dB was estimated for an LO oscillator level of -23 dB m at 5.7 K when the junction was biased at the point below the first Shapiro step.