Separation By Implantation Of Oxygen Research Articles

Engineering Strain in Silicon Using SIMOX 3-D Sculpting

Separation by IMplantation of OXygen (SIMOX) 3-D sculpting is considered as a new method for 3-D strain engineering in buried silicon waveguides. A model capable of analyzing the stress distribution and strain gradient of buried silicon waveguides is developed. The modeled stress shows agreement with experimental measurements obtained using Raman spectroscopy. Our method not only provides a new way to engineer strain in silicon but allows for the integration of strained-silicon-based devices with other optical and/or electronic devices on the same substrate as well, improving the device density and enhancing the functionality of the optical chip.

Effective Hole Mobility in SiGe Buried-Channel Quantum Well MOSFETs on SOI by Low-Pressure CVD

The effective hole mobility of buried-channel SiGe quantum well metal-oxide-semiconductor field-effect-transistors (MOSFETs) on silicon-on-insulator (SOI) was verified. The buried-channel structures consisted of a single quantum well and triple quantum wells which were deposited on a SIMOX (separation by implantation of oxygen) substrate at 550°C by low-pressure chemical vapor deposition (CVD). The growth apparatus was built based on ultra-clean technology. The Ge fraction of the alloy was 0.2 and 0.4 and a MOSFET with a 5.9 nm-thick gate oxide was fabricated on the well layers. The effective hole mobility versus effective electric field for the devices was obtained at room temperature. The mobility of triple Si0.8Ge0.2 quantum well device was enhanced by nearly 2 times compared to the single quantum well device. This enhancement which depended upon the ground energy level of the triple quantum wells was caused by the increase of holes trapped in the buried channel. The enhancement of single Si0.6Ge0.4 quantum well device was 60%, although the hole mobility was promoted as the Ge fraction in the alloy increased. The reason was due to the crystalline quality degradation.

Carbon redistribution in nanometric Si1−xCx layers upon ion beam synthesis of SiC by C implantation into SIMOX(1 1 1)

Nanometric 3C SiC layers (∼40 nm) between amorphous zones, i.e. SiO2/SiC/SiO2/Si, have been obtained using separation by implantation of oxygen (SIMOX) structures on bulk Si(1 1 1) as the starting material, i.e. Si(65 nm)/SiO2/Si(1 1 1) structures. We report mechanisms of carbon redistribution in the starting 65 nm silicon overlayer (SOV) upon SiC ion beam synthesis (IBS). Sequential C implantation steps (sample held at 600 °C), with 1250 °C annealing in between, have allowed us to register the evolution of the carbon composition (previously and after annealing) in the SOV under conversion when increasing the implantation fluence. Rutherford backscattering spectrometry (RBS) and transmission electron microscopy (TEM) reveal a two-sublayer structure of about the same thickness for the layer under conversion. The composition evolution of the sublayers (Si1−xCx) was monitored by evaluating Si composition changes measured by RBS analysis. High resolution TEM has demonstrated major differences in the structural quality of sublayers. We suggest that the observed structural differences are the main driving force for the observed C migration.

ChemInform Abstract: A Review of the Electrical Properties of SIMOX Substrates and Their Impact on Device Performance

Recent results are discussed in relation to the electrical properties of thin SIMOX (separation by implantation of oxygen) films and the specific mode of operation of SOI transistors. Various sources of SIMOX contamination are described, including the formation of oxygen donors. Interface coupling effects are illustrated by experimental results of transconductance, subthreshold swing, charge pumping, and noise. It is shown that SIMOX offers the possibility of engineering the interface quality and achieving a variety of quantum transport effects. Parasitical edge‐induced and transient phenomena are described and used to characterize sidewall defects and carrier lifetime. Finally, hot carrier injection is found to substantially degrade the buried oxide interface.

Oil-Filled Isolated High Pressure Sensor for High Temperature Application

In order to solve pressure measurement problems in the fields of aerospace, petroleum and chemical industry, mobile and military industry, a oil-filled isolated piezoresistive high pressure sensor has been developed with the range of 0~100 MPa, and was able to work reliably under high temperature of above 200 °C. Based on MEMS (Micro Electro-Mechanical System) and SIMOX (Separation by Implantation of Oxygen) technology, the piezoresistive sensor chip has been developed. By high temperature packaging process, the oil-filled isolated high pressure sensor was fabricated with the sensor chip and corrugated diaphragm. The experimental results showed that the oil-filled isolated high pressure sensor had good performances under high temperature of 200 °C, such as linearity error of 0.07%FS, repeatability error of 0.04%FS, hysteresis error of 0.03%FS.

GaN-based microdisk light emitting diodes on (111)-oriented nanosilicon-on-insulator templates

InGaN/GaN microdisk light emitting diodes (LEDs) on (111)-oriented nanosilicon-on-insulator (nano-SOI) substrates are demonstrated. The (111)-oriented thin SOI substrates are prepared by separation by implantation of oxygen (SIMOX) method. The InGaN/GaN LED structures are grown on these SIMOX templates by metal-organic chemical vapor deposition. The circular mesa patterns are created by standard LED processing steps including photolithography, inductively coupled plasma etching, and contact metallization. Due to the reflectivity changes at the bottom Si/SiO2 interfaces beneath AlN buffer, an improved light extraction from these LEDs has been observed. The room-temperature electroluminescence (EL) spectrum of the microdisk LEDs on SOI shows multiple interference peaks due to the reflections at the Fabry-Pérot boundaries and such effect resulted in an increased integrated EL intensity. For a comparative analysis of light extraction with respect to similar LED structures grown on bulk Si(111), a detailed reflectivity analysis has been carried out to verify the LED structures and to model the EL lineshapes.

Micro machining process of high temperature pressure sensor gauge chip based on SIMOX SOI wafer

The successful batch fabrication of a piezoresistive pressure sensor chip is described based on separation by implantation of oxygen (SIMOX) SOI wafer. The micro machining process mainly includes SIMOX, homoepitaxy silicon, and heavy dose of boron ion implantation doping, thermal oxidation, passivation layer of silicon nitride and standard optical lithography, Inductively Coupled Plasma (ICP), multi-layer metallisation and Au sputtering and so on. The sensor packaged with this kind of sensing chip is presented with high accuracy and a good long-term stability in high temperature testing experiments up to 250?C.

Defect Engineering for SIMOX Processing

SIMOX (Separation-by-Implantation-of-Oxygen) is an established technique to fabricate silicon-on-insulator (SOI) structures by oxygen ion implantation into silicon. The main problem of SIMOX is the very high oxygen ion fluence and the related defects. It is demonstrated that vacancy defects promote and localize the oxide growth. The crucial point is to control the distribution of vacancies. Oxygen implantation generates excess vacancies around RP/2 which act as trapping sites for oxide growth outside the region at the maximum concentration of oxygen at RP. The introduction of a narrow cavity layer by He implantation and subsequent annealing is shown to be a promising technique of defect engineering. The additional He implant does not initiate oxide growth in the top-Si layer of SOI.

Second Harmonic Generation for Noninvasive Metrology of Silicon-on-Insulator Wafers

We report experimental results from noninvasive second harmonic generation (SHG) measurements applied to characterize separation by implantation of oxygen (SIMOX) and bonded thin film silicon-on-insulator (SOI) wafers. Results demonstrate that the SHG response of the SOI structure can provide an indication of the quality of the buried oxide interfaces, including roughness, charge states, and detection of the presence of metallic contamination. The potential application of SHG as a noncontact metrology tool for process control is described

Photoluminescence in crystalline silicon quantum wells

Crystalline silicon single quantum wells (QWs) with a minimum Si layer thickness of around 1nm were fabricated by high temperature thermal oxidation of separation by implantation of oxygen (SIMOX) and epitaxial layer transfer (ELTRAN®) silicon-on-insulator (SOI) wafers. Not only Si thickness but also defect-free SOI materials may be important factors for observation of quantum-confined transition in the Si QWs. Si QWs fabricated from SIMOX SOI wafers showed strong interface-mediated luminescence, which is independent of Si thickness, at 1.63 and 1.49eV in the Si thickness range from 1to7nm. On the other hand, Si QWs fabricated from ELTRAN SOI wafers showed very strong thickness dependent luminescence in the range of 1.36–1.77eV without interface-mediated luminescence, where the Si thickness range was 3–1nm. The ability to detect quantum-confined luminescence seems to arise from the use of high-quality defect-free ELTRAN SOI wafers, from suppressed interface state luminescence by high temperature oxidation, and, possibly, from interface matching by crystalline silicon oxide. Hydrogen passivation suggests luminescence from a weak SiO state at around 1.59eV, but luminescence due to quantum confinement is more predominant in the ELTRAN Si QWs.

Low-Frequency-Noise Spectroscopy of SIMOX and Bonded SOI Wafers

Pseudo-MOSFET structures with metal source, drain, and guard electrodes are used to measure the low-frequency-noise characteristics of Separation by IMplantation of OXygen (SIMOX) and bonded silicon-on-insulator (SOI) wafers. The noise power spectra in the devices made from bonded SOI wafers are almost an order of magnitude lower than those made from SIMOX wafers. This is attributed to the lower interface trap density in the bonded wafers, which is extracted using the unified correlated model. The proposed method can be used to determine the 1/f noise characteristics of SOI wafers prior to circuit fabrication.

Design and Fabrication of a Piezoresistive Pressure Sensor for Ultra High Temperature Environment

In order to solve the pressure measurement problem in the harsh environment, a piezoresistive pressure sensor has been developed, which can be used under high temperature above 200°C and is able to endure instantaneous ultra high temperature (2000°C, duration≦2s) impact. Based on the MEMS (Micro Electro-Mechanical System) and integrated circuit technology, the piezoresistive pressure sensor's sensitive element was fabricated and constituted by silicon substrate, a thin buried silicon dioxide layer, four p-type resistors in the measuring circuit layer by boron ion implantation and photolithography, the top SiO2 layer by oxidation, stress matching Si3N4 layer, and a Ti-Pt-Au beam lead layer for connecting p-type resistors by sputtering. In order to decrease the leak-current influence to sensor in high temperature above 200°C, the buried SiO2 layer with the thickness 367 nm was fabricated by the SIMOX (Separation by Implantation of Oxygen) technology, which was instead of p-n junction to isolate the upper measuring circuit layer from Si substrate. In order to endure instantaneous ultra high temperature impact, the mechanical structure with cantilever & diaphragm and transmitting beam was designed. By laser welding and high temperature packaging technology, the high temperature piezoresistive pressure sensor was fabricated with range of 120MPa. After the thermal compensation, the sensor's thermal zero drift k0 and thermal sensitivity drift ks were easy to be less than 3×10−4FS/°C. The experimental results show that the developed piezoresistive pressure sensor has good performances under high temperature and is able to endure instantaneous ultra high temperature impact, which meets the requirements of modern industry, such as aviation, oil, engine, etc.

High temperature and frequency pressure sensor based on silicon-on-insulator layers

Based on silicon on insulator (SOI) technology, a novel high temperature pressure sensor with high frequency response is designed and fabricated, in which a buried silicon dioxide layer in the silicon material is developed by the separation by implantation of oxygen (SIMOX) technology. This layer can isolate leak currents between the top silicon layer for the detecting circuit and body silicon at a temperature of about 200 °C. In addition, the technology of silicon and glass bonding is used to create a package of the sensor without internal strain. A structural model and test data from the sensor are presented. The experimental results showed that this kind of sensor possesses good static performance in a high temperature environment and high frequency dynamic characteristics, which may satisfy the pressure measurement demands of the oil industry, aviation and space, and so on.

Radiation hardness improvement of separation-by-implantation-of-oxygen/silicon-on-insulator material by nitrogen ion implantation

In our work, nitrogen ions were implanted into separation-by-implantation-of-oxygen (SIMOX) wafers to improve the radiation hardness of the SIMOX material. The experiments of secondary ion mass spectroscopy (SIMS) analysis showed that some nitrogen ions were distributed in the buried oxide layers and some others were collected at the Si/SiO2 interface after annealing. The results of electron paramagnetic resonance (EPR) suggested the density of the defects in the nitrided samples changed with different nitrogen ion implantation energies. Semiconductor-insulator-semiconductor (SIS) capacitors were made on the materials, and capacitance-voltage (C-V) measurements were carried out to confirm the results. The super total dose radiation tolerance of the materials was verified by the small increase of the drain leakage current of the metal-oxide-semiconductor field effect transistor with n-channel (NMOSFETs) fabricated on the materials before and after total dose irradiation. The optimum implantation energy was also determined.

Relaxed silicon–germanium-on-insulator fabricated by oxygen implantation and oxidation-enhanced annealing

The application of separation-by-implantation-of-oxygen (SIMOX) for silicon–germanium-on-insulator (SGOI) fabrication is always limited by the Ge loss caused by the high temperature annealing. A unique SIMOX method was introduced to fabricate SGOI and resolve the problem of Ge loss. During the process, a SiO2 layer was formed pre-annealing to block the Ge out-diffusion. As the x-ray rocking curve and Raman spectra studies show, the Ge fraction of the SGOI was improved to 17 at.%. The final sample exhibits a planar and continuous buried oxide layer, sharp interfaces and a defect free top SiGe layer as the cross-sectional transmission-electron- microscopy (XTEM) and secondary-ion-mass-spectrometry studies show. The Rutherford backscattering spectroscopy demonstrated that the superficial SiGe layer was superior in quality (derived channelling yield of 10%). The results indicate that the additional step of thermal oxidation pre-annealing is vital to resolve the problem of Ge loss and the modified SIMOX process is applicable for SGOI fabrication.

Effect of ion-induced defects and oxygen concentration in annealing atmosphere on formation of buried oxide layer in SIMOX materials

Effects of ion-induced defects and oxygen concentration in annealing atmosphere on the formation of the buried oxide (BOX) layer in two-step implanted separation-by-implantation-of-oxygen (SIMOX) materials were investigated. It was found that the extra defects from the second-step oxygen implantation in the damage area promote the diffusion of oxygen in the annealing process. A thicker BOX layer can be obtained by increasing the concentration of oxygen in the annealing atmosphere after defect-induced by the oxygen implantation, which does not need longer annealing time compared to the normal annealing process. The formation mechanism of the BOX layer was discussed. Thus, the fabrication of the BOX layer in SIMOX material can be controlled by intentionally inducing the defects.

SiGe-on-insulator material fabrication by oxygen implantation into SiGe/Si heterostructure and novel two-step annealing

Relaxed SiGe-on-insulator (SGOI) is an attractive material to fabricate strained Si structures. Separation-by-implantation-of-oxygen (SIMOX) is a competing method to synthesize SGOI materials. In this work, pseudomorphic SiGe grown directly on Si substrate without any buffer layer SiGe/Si were implanted with 3 × 10 17 cm −2 oxygen ions at 60 kV followed by thermal treatment. Our results show that the sample structure strongly depends on the thermal history. Ge diffusions mainly occur at the beginning stage of the high temperature process. Oxygen segregation and Ge diffusion during the annealing process were investigated using Rutherford backscattering spectroscopy/channeling, high-resolution X-ray diffraction, and high-resolution transmission electron microscopy. We introduce a novel two-step annealing process to reduce Ge loss during the high temperature annealing. Sharp interfaces and good crystal quality SGOI structure was obtained. Our results indicate that the SIMOX process for silicon-on-insulator (SOI) fabrication can be adopted to produce SGOI.

Hydrogen annealing effects on epitaxy of SOI wafer

Thick silicon on insulator (SOI) wafers have been fabricated by chemical vapor deposition (CVD) after separation by implantation of oxygen (SIMOX) process. The hydrogen annealing effects on epitaxial Si layer were studied. The hydrogen annealing could remove the surface damages of substrate caused by SIMOX process and provide a smoother epitaxial substrate. The number of dislocations and stacking faults in the epitaxial layer decreased remarkably by hydrogen annealing SOI substrate. Meanwhile, compared with other reports, our hydrogen annealing did not degrade the buried oxide layer and top Si layer of SOI substrate.

Effects of buried oxide layer on indium diffusion in separation by implantation of oxygen

The diffusion of indium in both the top silicon and the buried oxide (BOX) layers in separation by implantation of oxygen (SIMOX) is investigated. For all indium-implanted samples, there is a significant redistribution of indium atoms from the top Si-BOX interface toward the bottom BOX-Si interface, thereby affecting the indium concentrations in the two silicon-BOX interfaces. In the case of relatively high-dose and high-energy indium implantation (1×1014cm−2 at 200keV), an anomalous segregation of indium is observed in both the bulk Si and the SIMOX substrates. However, there is a notable transportation of indium atoms from the top Si layer toward the bottom BOX-Si interface in the SIMOX, thereby affecting not only the indium concentrations in the two silicon-BOX interfaces but also the indium distribution in the top silicon layer. The unique indium-diffusion behavior in the SIMOX is believed to be a composite effect of indium trapping by the two Si-BOX interfaces, indium atoms being drawn away from the top silicon layer by the buried oxide, as well as implant damages in the top silicon. The asymmetrical structure of the BOX layer with Si islands accumulating at the bottom BOX-Si interface and the abundance of oxygen-related defects in the BOX layer are also believed to be responsible for the indium-diffusion behavior in the BOX layer.

The formation of thick buried oxide layers using ion implantation from water plasma

An implanter without an ion mass analyzer has been used to successfully fabricate silicon-on-insulator (SOI) materials by H 2O +, HO +, and O + ion implantation using water plasma. Based on the consideration that the masses of those three ions are very close, this fabrication makes it possible to form a single buried oxide (BOX) layer by choosing the appropriate implantation energy and dose. Cross-sectional transmission electron microscopy (XTEM) results indicated that the BOX thickness of the SOI materials fabricated using a water plasma approach is increased more than 50% over that of the conventional separation by implantation of oxygen (SIMOX) process. Secondary ion mass spectroscopy (SIMS) depth profile analysis on the as-implanted wafers showed that there are two hydrogen enrichment peaks around both sides of the projected range R p of oxygen, which correspond to the two interfaces of the BOX layer of the annealed samples. Additional designed experiments revealed that the heavily damaged region with hydrogen-induced defects appears to be the adsorption center for the outside oxygen to diffuse into the silicon during the high-temperature annealing process, and consequently, thicken the BOX layer of the SOI structure. The findings in the present work may provide a possible solution to reduce the cost of the conventional SIMOX–SOI wafers while maintaining a desirable BOX thickness.