Plasma Implantation Of Oxygen Research Articles

The effects of oxygen plasma implantation on bipolar resistive-switching properties of copper nitride thin films

Copper nitride (CuxN) thin films were prepared by plasma ion immersion implantation (PIII) then post-processed with oxygen plasma implantation at a voltage of −1.5kV. The resistive-switching properties of the CuxN:O-based RRAM devices were studied with different oxygen implantation time from 0 to 20min. The memory cells processed with oxygen plasma implantation for 5min showed longest endurance performances, largest resistance window and highest yield. Linear fitting results of the electrical measurements indicated the formation of copper oxide (CuO) is benefit for prolonged cycle life of the CuxN based RRAM devices, while increasing Cu2O species will lead to severe performance degradation.

In vivo stimulation of bone formation by aluminum and oxygen plasma surface-modified magnesium implants

A newly developed magnesium implant is used to stimulate bone formation in vivo. The magnesium implant after undergoing dual aluminum and oxygen plasma implantation is able to suppress rapid corrosion, leaching of magnesium ions, as well as hydrogen gas release from the biodegradable alloy in simulated body fluid (SBF). No released aluminum is detected from the SBF extract and enhanced corrosion resistance properties are confirmed by electrochemical tests. In vitro studies reveal enhanced growth of GFP mouse osteoblasts on the aluminum oxide coated sample, but not on the untreated sample. In addition to that a small amount (50 ppm) of magnesium ions can enhance osteogenic differentiation as reported previously, our present data show a low concentration of hydrogen can give rise to the same effect. To compare the bone volume change between the plasma-treated magnesium implant and untreated control, micro-computed tomography is performed and the plasma-treated implant is found to induce significant new bone formation adjacent to the implant from day 1 until the end of the animal study. On the contrary, bone loss is observed during the first week post-operation from the untreated magnesium sample. Owing to the protection offered by the Al2O3 layer, the plasma-treated implant degrades more slowly and the small amount of released magnesium ions stimulate new bone formation locally as revealed by histological analyses. Scanning electron microscopy discloses that the Al2O3 layer at the bone-implant interface is still present two months after implantation. In addition, no inflammation or tissue necrosis is observed from both treated and untreated implants. These promising results suggest that the plasma-treated magnesium implant can stimulate bone formation in vivo in a minimal invasive way and without causing post-operative complications.

Surface modification of polymeric materials by plasma immersion ion implantation

Polymer surfaces typically have low surface tension and high chemical inertness and so they usually have poor wetting and adhesion properties. The surface properties can be altered by modifying the molecular structure using plasma immersion ion implantation (PIII). In this work, Nylon-6 was treated using oxygen/nitrogen PIII. The observed improvement in the wettability is due to the oxygenated and nitrogen (amine) functional groups created on the polymer surface by the plasma treatment. X-ray photoelectron spectroscopy (XPS) results show that nitrogen and oxygen plasma implantation result in C–C bond breaking to form the imine and amine groups as well as alcohol and/or carbonyl groups on the surface. The water contact angle results reveal that the surface wetting properties depend on the functional groups, which can be adjusted by the ratio of oxygen–nitrogen mixtures.

Control of implantation area in direct-current plasma immersion ion implantation (DC-PIII)

In plasma immersion ion implantation (PIII) of planar samples such as silicon wafers in the PIII-ion-cut as well as separation by plasma implantation of oxygen (SPIMOX) processes, the only important ions are the ones arriving at the top surface. Ions implanted into the other surfaces are, in fact, undesirable as they reduce the efficiency of the power supply and plasma source and give rise to metallic contamination. We have demonstrated direct-current PIII (DC-PIII) by using a grounded grid to separate the vacuum chamber for planar sample implantation. The advantages include lower equipment cost, higher power and time efficiency, larger impact energy, and last but not least, smaller instrument footprint. In this paper, we investigate the control of the implantation area by adjusting the radius of the extraction hole, the distance between the conducting grid and the sample, and the radius of the wafer stage. Theoretical simulation is conducted using particle-in-cell and experiments are also carried out. Our results indicate that the implanted area increases with the radius of the extraction hole and wafer stage, but decreases with a larger distance between the grid and sample. The effects of the extraction hole radius G/sub r/ are the largest, followed by the placement of the sample to the conducting grid H. The wafer stage poses the least influence in this respect, but a proper wafer stage dimension improves the lateral implant dose and incident angle homogeneity. Our simulation and experimental results suggest optimal ratios of these parameters for each wafer size.

Two-dimensional sample temperature modeling in separation by plasma implantation of oxygen (SPIMOX) process

Plasma immersion ion implantation (PIII) offers high throughput and efficiency in the synthesis of silicon-on-insulator (SOI) materials. In the separation by plasma implantation of oxygen (SPIMOX) process, the spatial and time variation of the sample temperature must be known and well controlled to ensure uniform buried oxide and silicon overlying layer thicknesses over the entire silicon wafer. In this paper, we describe a two-dimensional model and derive the temperature distribution on the silicon wafer with respect to time and other process parameters. Our results show laterally nonuniform heating by the incoming ions and the local temperature is influenced more by the sample voltage and thermal irradiation coefficient of the target than the pulse duration and plasma density. The model provides a simple and quick means to determine whether external heating will be needed to maintain the sample temperature at 600/spl deg/C during the SPIMOX process.

Novel approaches for low cost fabrication of SOI

Two trials for low cost manufacture of silicon-on-insulator (SOI) wafers were implemented. Low dose separation by implantation of oxygen (SIMOX) procedure has been conducted on a beam-line ion implanter with mass analyzer. The energy dependence of the formed SOI structure was studied at varied implant dosages. The integrity of the buried oxide (BOX) layer was examined by transmission electron microscopy (TEM) and the threading dislocation in the top silicon layer was evaluated by Secco technique. The results indicated that not only the implanted oxygen dose but also the oxygen ion energy plays an important role in the formation of SOI structure with good crystallinity of top silicon, sharp Si/SiO2 interfaces and highly integrated BOX layer free of silicon inclusion. For separation by plasma implantation of oxygen (SPIMOX) approach, water plasma, rather than oxygen plasma, was employed to avoid oxygen spread in the implant depth profile. The SPIMOX process using water plasma was carried out on a beam-line ion implanter without mass selector to simulate the plasma implantation procedure. Cross-sectional TEM study revealed that uniform BOX layer was formed under single crystal silicon superficial layer with the present approach. The interfaces between silicon superficial layer, BOX layer and bulk silicon were smooth and sharp. An implant dose window has been identified for fabricating the desirable SOI structure.

Formation of silicon on insulator using separation by implantation of oxygen with water plasma

Separation by plasma implantation of oxygen (SPIMOX) was developed to fabricate silicon-on-insulator (SOI) wafers based on separation by implantation of oxygen technology, however, it suffers from the coexistence of O+ and O2+ ions in the oxygen plasma, which gives rise to nonuniformity of the formed buried oxide layer. In the present work, water plasma was used as a source of oxygen (H2O+, HO+, and O+) for achieving small spread in the oxygen implant depth profile. The feasibility of SPIMOX with water plasma to form SOI wafers was explored at an ion implanter without mass separator. Cross-sectional transmission electron microscopy revealed that a uniform buried oxide layer was formed under a single crystal silicon overlayer with the present process. The interfaces between the silicon overlayer, buried oxide layer, and bulk silicon were smooth and sharp. An implant dose window has been identified for producing a desirable SOI structure.

Direct temperature monitoring for semiconductors in plasma immersion ion implantation

In situ temperature monitoring is extremely important in plasma immersion ion implantation (PIII) of semiconductors. For instance, the silicon wafer must be heated to 600 °C or higher in separation by plasma implantation of oxygen, and in the PIII/ion-cut process, the wafer temperature must remain below 300 °C throughout the experiment. In this article, we present a thermocouple-based direct temperature measurement system for planar samples such as silicon wafers. In order to ensure reliable high-voltage operation and overall electrical isolation, the thermocouple assembly and wires are integrated into the sample chuck and feedthrough. Hydrogen plasma immersion ion implantation is performed in silicon to demonstrate the effectiveness and reliability of the device. Our experimental results indicate that instrumental parameters such as implantation voltage, pulse duration, and pulsing frequency affect the sample temperature to a different extent. The measured temperature rise is higher than that predicted by a theoretical model based on the Child–Langmuir law. The discrepancy is attributed to the finite-sample size and the nonplanar, conformal plasma sheath.

Plasma immersion ion implantation for SOI synthesis: SIMOX and ion-cut

We have demonstrated feasibility to form silicon-on-insulator (SOI) substrates using plasma immersion ion implantation (PIII) for both separation by implantation of oxygen and ion-cut. This high throughput technique can substantially lower the high cost of SOI substrates due to the simpler implanter design as well as ease of maintenance. For separation by plasma implantation of oxygen wafers, secondary ion mass spectrometry analysis and cross-sectional transmission electron micrographs show continuous buried oxide formation under a single-crystal silicon overlayer with sharp Si/SiO2 interfaces after oxygen plasma implantation and high-temperature (1300°C) annealing. Ion-cut SOI wafer fabrication technique is implemented for the first time using PIII. The hydrogen plasma can be optimized so that only one ion species is dominant in concentration and there are minimal effects by other residual ions on the ion-cut process. The physical mechanism of hydrogen induced silicon surface layer cleavage has been investigated. An ideal gas law model of the microcavity internal pressure combined with a two-dimensional finite element fracture mechanics model is used to approximate the fracture driving force which is sufficient to overcome the silicon fracture resistance.

Instrumental and process considerations for the fabrication of silicon-on-insulators (SOI) structures by plasma immersion ion implantation

Plasma immersion ion implantation (PIII) has recently been shown to be a viable method to fabricate silicon-on-insulator (SOI) materials using either the SPIMOX (separation by plasma implantation of oxygen) or the ion cut/wafer bonding method. We have recently modified and characterized a new generation plasma immersion ion implanter for SOI fabrication, and this paper will discuss some of the instrumental and processing issues, including the plasma source, mean free path consideration, and dc sheath characteristics.

Separation of plasma implantation of oxygen to form silicon on insulator

Separation by plasma implantation of oxygen (SPIMOX) is an economical method for silicon-on-insulator (SOI) wafer fabrication. This process employs the plasma immersion ion implantation (PIII) for the implantation of oxygen ions. The implantation rate, which is independent of the wafer size, is considerably higher than that of conventional implantation. The simpler implanter set-up is lower in cost and easier to maintain. The feasibility of SPIMOX has been demonstrated with successful fabrication of SOI structures implementing this process. The operational phase space on implantation condition, oxygen dose, and annealing requirement are identified. Secondary ion mass spectrometry analysis and cross-sectional transmission electron microscopy micrographs of the SPIMOX sample showed continuous buried oxide under single crystal overlayer with sharp silicon/oxide interfaces.

Separation by plasma implantation of oxygen (SPIMOX) operational phase space

Separation by plasma implantation of oxygen (SPIMOX) has been suggested as an economic alternative for separation by implantation of oxygen (SIMOX) to form the silicon-on-insulator (SOI) structure. The chief advantage of SPIMOX is the high throughput and low-cost implanter. The operation regime of implantation for SPIMOX, which uses dc plasma immersion ion implantation (PIII) for the oxygen implantation, has been studied in the phase space of implantation time and chamber pressure during implantation. The phase space is developed for a definite implantation voltage and dose which are dependent on the dimensions of the SOI structure to be fabricated. The effects of dose, implantation voltage, and fractional ionization on the phase space have been discussed. SPIMOX can achieve high throughputs for thin-SOI structure fabrications using high fractional ionization plasmas. The phase space developed for SPIMOX implantation ran also be used for other high-dose dc implantations with PIII which require a peaked implant profile below the surface.

Nucleation mechanism of SPIMOX (separation by plasma implantation of oxygen)

Buried oxide layers in Si were fabricated using the SPIMOX (separation by plasma implantation of oxygen) technique. The implantation was carried out by applying a negative bias to a Si substrate wafer immersed in an oxygen plasma. An implantation time of 2–3 min was required to implant the oxygen at doses ranging from 1 × 1017 atoms cm−2−3 × 1017 atoms cm−2. At a lower ion dose (1 × 1017 atoms cm−2), buried oxide precipitates were observed. At a higher dose (3 × 1017 atoms cm−2), a continuous buried oxide layer could be obtained, as indicated by cross section transmission electron microscopy (XTEM) and Rutherford backscattering spectrometry (RBS). By optimizing the concentration ratio of O+ and O2+ in the plasma and the implantation fluence, a double oxide layer (Si/oxide/Si/oxide/Si) structure could be produced in a single implantation step.

Synthesis of Soi Materials Using Plasma Immersion Ion Implantation

AbstractAs the dimensions of integrated circuits shrink towards the deep sub-micromeLer regime, silicon-on-insulator is regarded to be more favorable than silicon substrates. The biggest drawback of SOI is cost which will become more critical for next generation 300-nm silicon wafers. Plasma immersion ion implantation (PIII) provides a viable alternative for the fabrication of SOI wafers as the processing time is very short and independent of wafer size. Pill is being employed to synthesize two types of SOI materials, SPIMOX (Separation by Plasma IMplantation of OXygen) and bonded SOL. In SPIMOX fabrication, both oxygen and water plasmas have been attempted and the results indicate that a discrete buried oxide layer can indeed be formed. In the case of wafer bonding, PIII is utilized for smart-cutting, a process in which implanted hydrogen or helium causes the bonded wafer to crack along the plane thereby making one side of the wafer recyclable. This article reviews the work done and current status of SOI fabrication by PIII.

Formation of buried oxide in silicon using separation by plasma implantation of oxygen

Plasma immersion ion implantation (PIII) is used to fabricate buried oxide layers in silicon. This ‘‘separation by plasma implantation of oxygen’’ (SPIMOX) technique can achieve a nominal oxygen atom dose of 2×1017 cm−2 in implantation time of about 3 min. SPIMOX is thus presented as a practical high-throughput process for manufacturing silicon-on-insulator. In the SPIMOX samples prepared, three distinct modes of buried oxide microstructure formation are identified and related to the as-implanted oxygen profiles. A first-order model based on oxygen transport and oxide precipitation explains the formation mechanisms of these three types of SPIMOX layers.

Competitive Oxidation During Buried Oxide Formation Using Separation by Plasma Implantation of Oxygen (Spimox)

AbstractWe have recently demonstrated a new implantation technique called SPIMOX (separation by plasma implantation of oxygen) to synthesize silicon-on-insulator structures using plasma immersion ion implantation (PIII) process. the implantation is performed by applying a large negative bias to a Si wafer immersed in an oxygen plasma created by an ECR source. Since the technique has no mass analysis, coexistence of O+ and O2+ ions in oxygen plasma can cause a non-Gaussian profile of the as-implanted oxygen distribution. We observed that during post-implantation annealing, the ripening process of the oxide precipitates depends on depth and concentration of the oxygen peaks. IN addition, implanted oxygen can migrate towards the Si surface during annealing, preventing a continuous buried oxide layer formation. IN this paper, we report our observation on the effect of the implantation profile on the competitions between internal oxidation at different depths and between internal and surface oxidation processes. With an additional He implantation, we demonstrate that the nucleation of oxide precipitation can be enhanced.

Formation of Silicon on Insulator (Soi) With Separation by Plasma Implantation of Oxygen (Spimox)

AbstractBuried oxide layers in Si were fabricated using non-mass analyzed plasma immersion ion implantation (PHI). We call this process of making separation by implantation of oxygen (SIMOX) with implantation by PIII as separation by plasma implantation of oxygen (SPIMOX). The implantation was carried out by applying a large negative bias to a Si wafer immersed in an oxygen plasma and a nominal dose of 2 × 1017 cm”2 of oxygen was obtained in less than three minutes. Cross section transmission electron microscopy (XTEM) and Rutherford backscattering spectrometry (RBS) were used to characterize the wafers. Three distinct modes of microstructure development were observed after post implantation annealing. With a low oxygen dose (< 1 × 1017 cm”2 ), isolated silicon dioxide precipitates did not grow large enough to form a continuous oxide layer. With a high oxygen dose ( > 3 × 1017 cm”2 ), however, a single buried oxide layer was observed. By optimizing the concentration ratio of 0+ and 02+ in the plasma and the implant dose, a double oxide layer (Si/oxide/Si/oxide/Si) structure, was produced in a single implantation step.