As the FinFET technology is state-of-art CMOS platform at 14nm node and beyond, the embedded non-volatile memory (NVM) technologies need to be fully compatible at front-of-line (FEOL) or back-of-line (BEOL), e.g. Phase-Change-RAM (PCRAM), Resistive-RAM (RRAM), Magnetic-RAM (MRAM), and Nanotube-RAM (NRAM). Each NVM technology at BEOL has its own challenges in program power/energy/speed, thermal stability, read/write stability, endurance, scalability, read/write margins, and degradation by Oxidation, thus, a combination of the NVM technologies at BEOL may offer new applications with capability of stacking-up into 3D array. The CNT-based logic and spin-based logic circuits can be integrated in BEOL and lead to powerful 3D-monolithic integration for new applications with high performance and low power.

The improved scheme of data recording process on an optical disc based on a substrate made of high-stable materials has been proposed. Information layer with depth of 115nm and width of 600nm has been obtained on sapphire substrate by ion-beam etching using improved scheme. These experimental results allow to create the sapphire optical discs for long-term data storage.

Superlattic-like phase-change films are considered a promising phase-change material because it provides more controllable degree of freedoms for the simultaneous optimization of multiple parameters of phase-change films. However, the mechanism on the effect of superlattice-like structure on parameters of phase-change films is still controversial. At present there are two opinions: interfacial effect and the reduction of thermal conductivity. Here four superlattice-like phase-change films, [Ge₈Sb₉₂(15 nm)/Ge (x nm)]₃, are fabricated. Their behaviors of crystallization are investigated using the measurements of sheet resistance and coherent phonon spectroscopy. Two measurements show the crystallization temperature of the four superlattice-like films increases with the thickness of Ge layers. However, this increase cannot be explained by both the interfacial effect and the reduction of thermal conductivity. It is proposed that true superlattice effect should be considered to explain the effect of superlattice-like structure. Electron diffusion between two different constituent layers should be considered, as done in semiconductor superlattice structures. Electron diffusion can lead to the establishment of built-in electric field inside the superlattice-like films, which causes the change of band structures of two constituent materials and long-range coupling of superlattice-like films, further change of physical parameters. Based on this long-range coupling, the effect of cycle number in superlattice-like films on crystallization temperature can be explained. Some primary evidence on electric field effect on crystallization temperature of phase-change films is provided.

A photopolymer system doped with gold nanoparticles (Au NPs) was studied using Surface Enhanced Raman Scattering (SERS) technique in this work. In the system, polyvinyl alcohol is a binder, acrylamide and methylene-bisacrylamide are two monomers, methylene blue (MB) is a photosensitizer and triethanolamine is an initiator. Two types of Au NPs--- bare Au NPs with 13nm and 25nm diameter, and their corresponding SiO₂ shell-isolated Au (Au@SiO₂) NPs with ~2nm shell thickness, were prepared and doped into the photopolymer for reducing the shrinkage of holograms. The shield of SiO₂ shell avoids the dark reaction originating from electron transfer between Au NPs and MB molecules. More importantly, under 633nm laser excitation, the resonance Raman scattering of MB can be triggered, and the Raman signal of MB can be enhanced greatly due to the local enhanced electromagnetic field by Au@SiO₂ NPs. Both of them made the in-situ Raman detection of the photopolymer more feasible. The experimental results not only show the excitation process of MB but also display the polymerization process of the photopolymer. In addition, the excitation rate of MB and the polymerization rate of monomers can also be obtained using their time Raman spectra. This provides an experimental tool for detecting the photochemical kinetics process of the photopolymer.

Since the invention of 3-D ROM in 1996, three-dimensional memory (3D-M) has been under development for nearly two decades. In this presentation, we'll review the 3D-M history and compare different 3D-Ms (including 3D-OTP from Matrix Semiconductor, 3D-NAND from Samsung and 3D-XPoint from Intel/Micron).

A novel standby mode scheme with light load efficiency improvement is proposed in this paper, which is especially suitable for modern boost dc-dc converters powered by Li-ion battery. The proposed output load estimator is able to accurately reflect the output load current under light load condition once inductor current enters in the discontinuous conduction mode (DCM). Our experimental results show that the proposed boost dc-dc converter can automatically select approximate PWM switching frequency according to the detected information of the proposed output load estimator, regardless of power supply and inductor value.

This paper presents a 2X/1.5X switched-capacitor charge pump for phase change memory (PCM). For a 16-bitparallelism PCM, the set/reset time is more than 100 ns, and the charge pump should output a minimum 60 mA load current. The proposed charge pump can supply 4.1 V voltage and 0-60 mA current for PCM, with an input voltage range of 2.2-3.5 V. It can also automatically change the power conversion ratio between the 2X/1.5X modes according to input voltage. For the improvement of efficiency and load transient response, an auto-adjustable output regulation scheme is employed. In this scheme, two new reference voltages are introduced and compared with output voltage. Average lasting time of the enable signal changes under different load conditions. The Enable signal then controls booster’s power transistors switching to regulate output voltage. In this way, output voltage was controlled within a permissible range. The charge pump has been designed and simulated in a 40nm CMOS process. The results show maximum power efficiency in 30 mA load current is 90.73%, and conversion ratio control increases the efficiency by 23.06% in 3 V.

Phase change memory is regarded as one of the most promising candidates for the next-generation non-volatile memory. Zr₉(Ge₂Sb₂Te₅)₉₁ film was investigated as storage material for phase-change memory application. The crystallization temperature (T_c) and 10 years data retention temperature of the Zr₉(Ge₂Sb₂Te₅)₉₁ film are about 195 and 106.7°C, respectively, and both higher than that of Ge₂Sb₂Te₅ (GST). The sheet resistance ratio between amorphous and crystalline states is up to four orders of magnitude. The crystalline resistance of Zr₉(Ge₂Sb₂Te₅)₉₁ film is higher than GST for one order of magnitude, which contribute to reduce the power consumption for PCM device. Zr₉(Ge₂Sb₂Te₅)₉₁ film exhibit larger optical band gap in comparison with GST. Zr₉(Ge₂Sb₂Te₅)₉₁ is considered to be a promising material for phase change memory.

The amorphous-to-crystalline transitions of N-doped GeTe films are investigated by in situ film resistance measurements. Both the crystallization temperature and resistance of the N-doped films increase. The analysis of X-ray diffraction (XRD) measurement indicates that the grain size of the films with more nitrogen content can be refined, leading to the improvement in the resistance and thermal stability of the phase change films. The N-doped GeTe films have higher activation energy for crystallization. The 10-year lifetime is raised from 90°C of undoped GeTe film to 138°C of the N-doped GeTe film. The better surface roughness is confirmed by atomic force microscopy. The phase change speed is evaluated by the picosecond laser pump-probe technology.

The resolution of conventional optical microscope is intrinsically limited by the optical diffraction, therefore it cannot be used in the measurement of sub-100nm shape and structural detection. Non-optical imaging techniques are not limited by the optical diffraction. For example, scanning tunneling microscopy (STM) and atomic force microscopy (AFM), but both of them have the weakness of narrow view field, low efficiency, and excessive cost. To detect nanoscale material, a new microscopic imaging technique is introduced in this paper, i.e. the polarization parameter indirect microscopic imaging technique. A conventional reflection microscopic system is used as the basic optical system, with polarization-modulation mechanics being inserted into it. The near-field structural characteristics can be delivered by optical wave and material coupling. According to coupling and conduction physics, changes of the optical wave parameters can be calculated, and then curves of the image intensity can be obtained. By analyzing the near-field polarization parameters in nanoscale, indirect polarization parameter imaging can be established.

The crystallization process and crystal structure of the phase change material TiSbTe alloy have been successfully established, which is essential for applying this alloy in phase change memory. Specifically, transmission electron microscopy (TEM) analyses of the film annealed in situ were used in combination with selected-area electron diffraction (SAED) and radial distribution function (RDF) analyses to investigate the structural evolution from the amorphous phase to the polycrystalline phase. Moreover, the presence of structures with medium-range order in amorphous TST, which is beneficial to high-speed crystallization, was indicated by the structure factors S(Q)s. The crystallization temperature was determined to be approximately 170°C, and the grain size varied from several to dozens of nanometers. As the temperature increased, particularly above 200°C, the first single peak of the rG(r) curves transformed into double shoulder peaks due to the increasing impact of the Ti–Te bonds. In general, the majority of Ti atoms enter the SbTe lattice, whereas the remainder of the Ti atoms aggregate, leading to the appearance of TiTe₂ phase separation, as confirmed by the SAED patterns, high-angle annular dark field scanning transmission electron microscopy (HAADFSTEM) images and the corresponding energy-dispersive X-ray (EDX) mappings.

With the ever-increasing amount of data being stored via social media, mobile telephony base stations, and network devices etc. the database systems face severe bandwidth bottlenecks when moving vast amounts of data from storage to the processing nodes. At the same time, Storage Class Memory (SCM) technologies such as Phase Change Memory (PCM) with unique features like fast read access, high density, non-volatility, byte-addressability, positive response to increasing temperature, superior scalability, and zero standby leakage have changed the landscape of modern computing and storage systems. In such a scenario, we present a storage system called FLEET which can off-load partial or whole SQL queries to the storage engine from CPU. FLEET uses an FPGA rather than conventional CPUs to implement the off-load engine due to its highly parallel nature. We have implemented an initial prototype of FLEET with PCM-based storage. The results demonstrate that significant performance and CPU utilization gains can be achieved by pushing selected query processing components inside in PCM-based storage.

An improved sense amplifier with speed-up pre-charge scheme is introduced in this paper. What’s more, in order to avoid unexpected fatal damage while reading operation, clamp voltage is adopted. Distinguished with the conventional current sense amplifier, the proposed sense amplifier shortens not only the read access time by reducing the charging time due to parasite capacitor of storage cells but also the delay time because of the RC delay on wire by using two branches of pre-charge circuit at the both ends of bit lines. The simulation result taken in SMIC 28nm process shows that, with 1Kb PCM array, the proposed sense amplifier can efficiently reduce the access time from 33.7ns to 16.5ns.

This paper presents a fully digital-control soft start mechanism with coefficients Ki optimization for DC-DC power converters. During the soft start phase, a ladder reference voltage steps up gradually to make inductor current ramp up smoothly and overshoot voltage is minimized with the proposed coefficients Ki distribution. Simulation results show that massive inductor current can be well avoided during the soft start process with the proposed soft start mechanism, which only occupies a chip area of 300um×120um.

Recently, numerous efforts have been made on NVM-based Field Programmable Gate Arrays (FPGAs) because the emerging non-volatile memory (NVM) technologies have the advantages of lower leakage power and higher density than Static Random Access Memory (SRAM) technology. However, the cost and the scale of FPGAs are so high and large that they can’t be applied in the consumer electronics field and Internet of Things (IoT). Due to the small scale and low cost, Programmable Logic Array (PLA) is an ideal option for these fields. However, up to now there are few researches on non-volatile PLA based on emerging NVMs. In this paper, a power-efficient non-volatile PLA based on Phase Change Memory (PCM) is proposed. The proposed non-volatile PLA architecture has been evaluated using the 40 nm Complementary Metal Oxide Semiconductor (CMOS) technology, and the simulation results show the correct functionality of the PLA. After the PLA reads the configuration bits from the non-volatile programmable elements (PEs), the power of the programmable elements can be OFF. Therefore, the standby power of the programmable elements is much smaller than that of the commonly SRAM-based PLAs. The simulation results also show that the total power of nvPLA is reduced by about 53.6% when the supply power of Programmable Element is OFF.

Emerging memory technologies such as Phase change memory (PCM) tend to offer fast, random access to persistent storage with better scalability. It’s a hot topic of academic and industrial research to establish PCM in storage hierarchy to narrow the performance gap. However, the existing file systems do not perform well with the emerging PCM storage, which access storage medium via a slow, block-based interface. In this paper, we propose a novel file system, RAFS, to bring about good performance of PCM, which is built in the embedded platform. We attach PCM chips to the memory bus and build RAFS on the physical address space. In the proposed file system, we simplify traditional system architecture to eliminate block-related operations and layers. Furthermore, we adopt memory mapping and bypassed page cache to reduce copy overhead between the process address space and storage device. XIP mechanisms are also supported in RAFS. To the best of our knowledge, we are among the first to implement file system on real PCM chips. We have analyzed and evaluated its performance with IOZONE benchmark tools. Our experimental results show that the RAFS on PCM outperforms Ext4fs on SDRAM with small record lengths. Based on DRAM, RAFS is significantly faster than Ext4fs by 18% to 250%.

Phase Change Memory (PCM) is regarded as one of the most promising candidates for the next-generation nonvolatile memory. Its storage medium, phase change material, has attracted continuous exploration. Sb₂Te₃ is a high-speed phase change material matrix with low crystallization temperature. Cr-doped Sb₂Te₃ (CST) films with suitable composition have been studied and proved to be a promising novel phase change material with high speed and good thermal stability. In this paper, detailed R_s-T characteristics and Hall characteristics of the CST films are studied. We find that, when more parts of the film crystallizes into the ordered structure, the activation energy for electrical conduction (Eσ) decreases, indicating that the semiconductor property is weakened. And with the increase of Cr-dopants, Eσ of the As-deposited (As-de) amorphous CST films decreases, thus the thermal stability of resistance is improved. Hall results show that Sb₂Te₃ and CST films are all in P-type. For As-de amorphous films, with the increase of Cr-dopants, the carrier mobility decreases all along, while the carrier density decreases at first and then increases. For the crystalline films, with the increase of Cr-dopants, the carrier mobility decreases, while the carrier density increases.

The stability of TiN which is the preferred bottom electrode contact (BEC) of phase change memory (PCM) due to its low thermal conductivity and suitable electrical conductivity, is very essential to the reliability of PCM devices. In this work, in order to investigate the effect of high aspect ratio process (HARP) SiO₂ on the performance of TiN, both TiN/SiO₂, TiN/SiN thin films and TiN BEC device structures are analyzed. By combining transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS), we found that the TiN would be oxidized after the deposition of HARP SiO₂ and there exist a thin (~4 nm) oxidation interfacial layer between TiN and SiO₂. Electrical measurements were performed on the 1R PCM test-key die with 7 nm and 10 nm BEC-only cells. The statistical initial resistances of BEC have wide distribution and it is confirmed that the non-uniform oxidation of TiN BEC affects the astringency of the resistance of TiN BEC. The experimental results help to optimize the process of TiN BEC, and SiN is recommended as a better choice as the linear layer.

As the process technology is continuously shrinking, low power consumption is a major issue in VLSI Systems-on-Chip (SoCs), especially for standby-power-critical applications. Recently, the emerging CMOS-compatible non-volatile memories (NVMs), such as Phase Change Memory (PCM), have been used as on-chip storage elements, which can obtain non-volatile processing, nearly-zero standby power and instant-on capability. PCM has been considered as the best candidate for the next generation of NVMs for its low cost, high density and high resistance transformation ratio. In this paper, for the first time, we present a diode-selected PCM based non-volatile flip-flop (NVFF) which is optimized for better power consumption and process variation tolerance. With dual trench isolation process, the diode-selected PCM realizes ultra small area, which is very suitable for multi-context configuration and large scale flip-flops matrix. Since the MOS-selected PCM is hard to shrink further due to large amount of PCM write current, the proposed NVFF achieves higher power efficiency without loss of current driving capability. Using the 40nm manufacturing process, the area of the cell (1D1R) is as small as 0.016 μm². Simulation results show that the energy consumption during the recall operation is 62 fJ with 1.1 standard supply voltage, which is reduced by 54.9% compared to the previous 2T2R based NVFF. When the supply voltage reduces to 0.7 V, the recall energy is as low as 17 fJ. With the great advantages in cell size and energy, the proposed diode-selected NVFF is very applicable and cost-effective for ULP systems.

A three-dimensional finite element model for Phase-Change Random Access Memory (PCRAM) is established to simulate thermal and electrical distribution during RESET operation. The establishment of the model is highly in accordance with the manufacture of PCRAM cell in the 40nm process and the model is applied to simulate the RESET behaviors of 35 nm diameter of titanium nitride (TiN) bottom electrode in the conventional mushroom structure (MS). By the simulations of thermal and electrical distribution, the highest temperature is observed in TiN bottom electrode contactor and meanwhile the voltage of the TiN bottom electrode accounts for as high as 65 percent of the total voltage. It induces high RESET current which suggests that the thermoelectric conductivity of MS is crucial in improving the heating efficiency in RESET process. Simulation results of RESET current and high resistance distribution during RESET operation are close to the data from the actual measurement. However those two values of low resistance are slightly different, probably due to the interface resistance between Ge₂Sb₂Te₅ (GST) and other materials and the resistance caused by microstructural defects. This work reveals the importance of the thermoelectrical properties of materials in PCRAM cells and improves the quality of PCRAM simulations in industrial application.

The widely used traditional Flash memory suffers from its performance limits such as its serious crosstalk problems, and increasing complexity of floating gate scaling. Phase change random access memory (PCRAM) becomes one of the most potential nonvolatile memories among the new memory techniques. In this paper, a 1M-bit PCRAM chip is designed based on the SMIC 40nm CMOS technology. Focusing on the read and write performance, two new circuits with high-speed read operation and highly reliable reset operation are proposed. The high-speed read circuit effectively reduces the reading time from 74ns to 40ns. The double-mode reset circuit improves the chip yield. This 1M-bit PCRAM chip has been simulated on cadence. After layout design is completed, the chip will be taped out for post-test.

Recently, carbon-doped Ge₂Sb₂Te₅ (CGST) has been proved to be a high promising material for future phase change memory technology. In this article, reactive ion etching (RIE) of phase change material CGST films is studied using CF₄/Ar gas mixture. The effects on gas-mixing ratio, RF power, gas pressure on the etch rate, etch profile and roughness of the CGST film are investigated. Conventional phase change material Ge₂Sb₂Te₅ (GST) films are simultaneously studied for comparison. Compared with GST film, 10 % more CF₄ is needed for high etch rate and 10% less CF₄ for good anisotropy of CGST due to more fluorocarbon polymer deposition during CF₄ etching. The trends of etch rates and roughness of CGST with varying RF power and chamber pressure are similar with those of GST. Furthermore, the etch rate of CGST are more easily to be saturated when higher RF power is applied.

Phase change random access memory (PCM) appears to be the strongest candidate for next-generation high density nonvolatile memory. The fabrication of ultrahigh density PCM depends heavily on the thin film growth technique for the phase changing chalcogenide material. In this study, TiSb₂Te₄ (TST) thin films were deposited by thermal atomic layer deposition (ALD) method using TiCl₄, SbCl₃, (Et₃Si)₂Te as precursors. The threshold voltage for the cell based on thermal ALD-deposited TST is about 2.0 V, which is much lower than that (3.5 V) of the device based on PVD-deposited Ge2Sb2Te5 (GST) with the identical cell architecture. Tests of TST-based PCM cells have demonstrated a fast switching rate of ~100 ns. Furthermore, because of the lower melting point and thermal conductivities of TST materials, TST-based PCM cells exhibit 19% reduction of pulse voltages for Reset operation compared with GST-based PCM cells. These results show that thermal ALD is an attractive method for the preparation of phase change materials.

In this work, we discuss about the formation of recessed hole in the manufacturing process of phase change memory (PCM). Three recessed holes with different slope angle and depth were obtained by changing the NF₃/O₂ gas mixing ratio. The recessed holes upon bottom electrode contact (BEC) were achieved by etch back process after the formation of BEC. The etching process takes advantage of the etch rate of TiN which is faster than that of SiN. With increasing content of O₂ gas, the decrease in the etch rate of SiN was larger than that of TiN, and this increases the selectivity of TiN to SiN. Oxidation layer can be found upon the SiN layer in the energy dispersive X-ray (EDX) elemental mapping profile after the recessed etching step. It is the existence of oxidation layer that suppressed the etching of SiN.

In this work, we make reduced graphene oxide (rGO) solution via chemical way and use it to fabricate Field-effect transistor (FET) channel by spin coating for investigating the performance of grapheme-based devices. An inductively coupled plasma (ICP) with very low plasma density is applied to etch the surface of rGO. It has been confirmed that residues and contaminations can be removed through etching and proper etching parameters can lead to better electrical properties more like the pristine graphene without creating defects. Considering the application of graphene added to silicon-based electronic devices, such a cleaning method can be used due to its advantages of being a low-temperature, large-area, high-throughput, and Si-compatible process.

We report a new method, polarization parameters indirect microscopic imaging with a high transmission infrared light source, to detect the morphology and component of human skin. A conventional reflection microscopic system is used as the basic optical system, into which a polarization-modulation mechanics is inserted and a high transmission infrared light source is utilized. The near-field structural characteristics of human skin can be delivered by infrared waves and material coupling. According to coupling and conduction physics, changes of the optical wave parameters can be calculated and curves of the intensity of the image can be obtained. By analyzing the near-field polarization parameters in nanoscale, we can finally get the inversion images of human skin. Compared with the conventional direct optical microscope, this method can break diffraction limit and achieve a super resolution of sub-100nm. Besides, the method is more sensitive to the edges, wrinkles, boundaries and impurity particles.

In this paper, current density-voltage (J-V) characteristic of dual trench diode array have been investigated by both TCAD model and experimental method. It is shown that the arsenic concentration in buried N+ layer (BNL), epitaxial (EPI) layer thickness, and the dosage of P region in PN junction are expected to be the prominent factors responsible for both of the leakage and drive current performance according to TCAD simulation. By introducing the optimal siliconbased results, the 4×4 diode arrays were successfully manufactured by 40nm CMOS technology. The median values of drive and reverse leakage current densities are ~7.30×10^-2 A/μm² and 5.61×10^-9 A/μm², respectively. The breakdown voltages (BVDs) of diode array are exceeding 6V, and the J_on/J_off ratios of ~10⁹, which can satisfy the requirements of phase change memory (PCM) applications.

Phase Change Memory (PCM) has great potential for commercial applications of next generation non-volatile memory (NVM) due to its high operation speed, high endurance and low power consumption. Sb₂Te (ST) is a common phase-change material and has fast crystallization speed, while thermal stability is relatively poor and its crystallization temperature is about 142°C. According to the Arrhenius law, the extrapolated failure temperature is about 55°C for ten years. When heated above the crystallization temperature while below the melting point, its structure can be transformed from amorphous phase to hexagonal phase. Due to the growth-dominated crystallization mechanism, the grain size of ST film is large and the diameter of about 300 nm is too large compared with Ge₂Sb₂Te₅ (GST), which may deteriorate the device performance. High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) were employed to study the microstructures and the results indicate that the crystal plane is {110}. In addition, device cells were manufactured and their current–voltage (I–V) and resistance–voltage characteristics were tested, and the results reveal that the threshold voltage (V_th) of ST film is 0.87 V. By researching the basic properties of ST, we can understand its disadvantages and manage to improve its performance by doping or other proper methods. Finally, the improved ST can be a candidate for optical discs and PCM.

Environmental friendly Te-free phase change material of Ti_xSb_2.19Se was investigated for PCM application. As the important thermal properties, the crystallization temperature (Tc) and data retention for ten years for the best selected composition Ti_0.34Sb_2.19Se (TSS) are 234°C and 160‡C, respectively. Detection of the crystal structure of TSS by means of XRD, TEM and XPS reveals that the grains are more uniform compared with Ge₂Sb₂Te₅ (GST). The Set and Reset operation voltages for TSS-based phase change memory devices are much lower than those of conventional GST-based ones. Remarkably, the TSS device exhibits an extremely high phase change speed of 10 ns.

The reliability and operation speed have long been two great obstacles in phase change memory technology. Thus (SiC)_0.85-Sb₃Te alloy was proposed to be a new-type phase change material due to its high crystallization temperature (199.7°C) and good data retention ability (118.9°C for 10-year archival life) in this work. The stress accompanying the phase transition in (SiC)_0.85-Sb₃Te is smaller than those in pure Sb₃Te and the traditional material, Ge₂Sb₂Te₅. This is attributed to the fine crystal grain size due to SiC doping, which contributes to the ultrafast reversible operation (5 ns) and good endurance (2.3 × 10⁴ cycles) of (SiC)_0.85-Sb₃Te based phase change memory cells.

The Sn₁₅Sb₈₅ alloy is characterized by its rapid phase transition. However, its poor thermal stability hinders its application as phase change memory material. After nitrogen doping, the crystallization temperature and 10-year data retention temperature of Sn₁₅Sb₈₅ thin films even reach 235‡C and 173°C, respectively. Both the crystallization activation energy and the amorphous resistance of the thin films increase as well. As a result, the material thermal stability is significant improved. The surface roughness of the films is evaluated by atomic force microscope (AFM). The phase change speed of the thin films, measured by the picosecond laser technique, remains fast.

With Phase-change memory (PCM), information can be stored as different resistance states even when not powered. In order to accurately characterize the reliability of PCM devices, data retention has to be tested carefully. In this paper, a new test method is applied to measure the data retention of T-shaped PCM devices. This method makes it possible to accelerate crystallization in the amorphous area by using current bias. The new method works based on the field-induced crystallization theory, and could be able to gather fast and detailed information about high-resistance state’s failure process, and at the same time, it could avoid issues related to high temperature. Experimental data for T-shaped PCM devices based on Ge₂Sb₂Te₅ are presented and analyzed. An exponential trend-line of failure time t versus reciprocal bias current 1/I shows only negligible deviation of the measured data points, enabling the extrapolation of the retention behavior for ten-year lifetime. A maximum disturb current value of 5.08 μA is extracted to guarantee the ten years data retention requirement for PCM applications.

In this paper, the development of a new chemical mechanical planarization (CMP) slurry for phase change material GeSbTe (GST) and its application in the manufacturing process of phase change memory based on GST is presented. The basic abrasive of the slurry was special colloid silica which was chosen from several kinds of colloid silica with different surface treatment and stable pH range. Oxidizer, chelator, inhibitor and protective agent were added to the colloid silica to accelerate the polishing rate and protect the surface. A series of CMP experiments were carried out on a 4-inch experimental platform to confirm and optimize the performance of the slurry with different ratio of reagents. After the recipe was frozen, the slurry was used in the CMP process of manufacturing the phase change memory on 12-inch wafers. The results on blanket wafers show that the remove rate, endurance life, residue control is at the same level with those of the old slurry, while the scratch control is much better than that of the old one. The final results on both metal line structure and blade structure show that the new slurry has much better performance than the old one on oxide loss, scratch and erosion control.

Fabrication of high-resolution micro-structures is essential for DOEs and MEMS and has attracted increasing attention. In this study, several high-resolution micro-structures have been fabricated on AgInSbTe phase-change films by laser thermal lithography, and the minimum linewidth of these structures is about 200 nm, which is smaller than the size of the focused spot. The results indicate that laser thermal lithography is a simple and effective technique for the fabrication of micro-structures on AgInSbTe phase-change thin films.

In this work, an optical system with large diameter off-axis parabolic lenses was adopted to achieve diffraction gratings by laser interference exposure. The diffraction wavefront aberration caused by temperature variations was simulated using ZEMAX. Through theoretical analysis and optical simulation, it is proved that the diffraction wavefront aberration of holographic grating caused by the pinhole’s location errors (it is assumed that when the displacement of pinhole exists along one axis, the locations of the pinhole along the other two orthogonal axes are in a state of precise adjustment ) is much larger when the displacement occurs along z axis than along the other two axes, and the diffraction wavefront aberration is the smallest when the displacement occurs along x axis. If the ambient temperature changes by 1 degree, the PV value is 0.0631λ when the location of the pinhole changes by 0.121mm along z axis, 0.0034λor 0.0672λ when the location of the pinhole changes by 0.002mm along x axis or 0.03mm along y axis. To reach the diffraction limit (that means the PV value is 0.25λ), the decentering value of the pinhole along z axis should be less than 0.0341mm. In conclusion, the position error along z axis is an important factor to influence the PV value of diffraction grating, and the effect of temperature on the PV value of diffraction grating can be neglected.

Laser thermal lithography has been proposed for a few years, which has the advantages of breaking through the optical diffraction limit, operation in far-field and in air, and low production cost. In this paper, a new hydrazone metal complex is used as the laser thermal lithography material due to its feature of the one-step fabrication of micro/nano structure without mask and wet-etching process. Based on the laser thermal lithography method, super resolution nano-information pits are directly written on the surface of hydrazone metal complex thin films. Pits with a minimum feature size of about 79 nm are successfully obtained, which is only about 1/7 of the writing spot size. Moreover, the reactive ion etching method can be applied to transfer the pits onto a silica substrate. These results suggest the potential applications of the new material in high density optical data storage and semiconductor industries.

Laser thermal lithography technology based on the optothermal mode is a very promising fabrication approach in high density optical storage and semiconductor industry. SbBi thin film is a typical phase change material which has been deep going studied and widely used as the super-resolution mask layer. Phase transformation of the SbBi material from amorphous to crystalline state can be achieved by vacuum annealing or laser irradiating. In this work, SbBi thin films as a new thermal lithography material are investigated for the first time. The thermal lithography characteristics of SbBi thin films were studied by means of etching in the ammonium sulfide solution. Line-shaped structures were developed using our laser-induced crystallization apparatus, followed by etching in the ammonium sulfide solution. It is found that the etching rate of the amorphous state is greater than that of the crystalline state, which are 17.8 nm/min and 4 nm/min, respectively. The mechanism of the difference in etching rate between the two states is also discussed. These results indicate that SbBi thin film is a potential candidate for thermal lithography materials.

Phase change material Sb₂Te₃ has been proved to possess a strong nonlinear saturation absorption effect, which could produce a dynamic and reversible optical pinhole channel as the origin of breaking through the diffraction limit. In this work, a pump–probe experimental setup is constructed to explore the transient formation process of the dynamic and reversible optical pinhole channel, and the transient transmission and reflection light intensities of the Sb₂Te₃ are measured directly. The results show that Sb₂Te₃ is an appropriate material for the mask layer of super resolution nano-optical fabrication.

The interface which should correspond to Ohmic contact between the TiN bottom electrode and the TiN adhesive layer is investigated. However, from the measured V-I curve, a non-linear relationship is observed. The previous research and the replotted V-I curve using double-logarithmic scale demonstrate that an oxide layer at the interface is the major reason for the non-linear relationship and that the conduction mechanism here follows the Space-Charge-Limited- Current mechanism. To eliminate the interface effect, a pulse current with a compliance is introduced. A phenomenon is observed that negative resistance occurs because of the capture of filament in the oxide layer. As the width of pulse current increases, the interface effect is eliminated due to the formation of a permanent conducting filament. And , the VI curve shows a linear relationship, representing that the interface corresponds to Ohmic contact and the interface effect has been eliminated efficiently.

The thermal transmission process induced by single-shot femtosecond laser pulses in Sb₇₀Te₃₀ phase change thin films with or without a Ag thermal-conductive layer was studied numerically with a two-temperature model. The distribution of electron and lattice temperatures was calculated by a one-dimensional finite difference method. The different temperature evolution characteristics on different time scales (from several picoseconds, to tens of picoseconds and to several nanoseconds) are discussed based on the electron-phonon coupling theory. The influence of a special point in the lattice temperature evolution curves on the crystallization time of phase change thin films is analyzed. The results will be helpful to the deeper understanding of the ultrafast phase transition mechanism of phase change memory materials.

The Femtosecond laser pulse induced phase transition dynamics of Cr-doped Sb₂Te₁ films was studied by real-time reflectivity measurements with a pump-probe system. It was found that crystallization of the as-deposited Cr_xSb₂Te₁ phase-change thin films exhibits a multi-stage process lasting for about 40ns.The time required for the multi-stage process seems to be not related to the contents of Cr element. The durations of the crystallization and amorphization processes are approximately the same. Doping Cr into Sb₂Te₁ thin film can improve its photo-thermal stability without obvious change in the crystallization rate. Optical images and image intensity cross sections are used to visualize the transformed regions. This work may provide further insight into the phase-change mechanism of Cr_xSb₂Te₁ under extra-non-equilibrium conditions and aid to develop new ultrafast phase-change memory materials.

This PDF file contains the front matter associated with SPIE Proceedings Volume 9818 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.