Silicon-on-insulating multi-layers for total-dose irradiation hardness

Silicon-on-insulating multi-layer (SOIM) materials were fabricated by co-implantation of oxygen and nitrogen ions with different energies and doses. The multilayer microstructure was investigated by cross-sectional transmission electron microscopy. P-channel metal-oxide-semiconductor (PMOS) transistors and metal-semiconductor-insulator-semiconductor (MSIS) capacitors were produced by these materials. After the irradiated total dose reaches 3 x 10(5) rad (Si), the threshold voltage of the SOIM-based PMOS transistor only shifts 0.07 V, while thin silicon-on-insulating buried-oxide SIMOX-based PMOS transistors have a shift of 1.2V, where SIMOX represents the separated by implanted oxygen. The difference of capacitance of the SOIM-based MSIS capacitors before and after irradiation is less than that of the thin-box SIMOX-based MSIS capacitor. The results suggest that the SOIM materials have a more remarkable irradiation tolerance of total dose effect, compared to the thin-buried-oxide SIMOX materials.

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.

Improvement of the radiation hardness of SIMOX buried layers using nitrogen implantation

An investigation of hardening the buried oxides (BOX) in separation by implanted oxygen (SIMOX) silicon-on-insulator (SOI) wafers to total-dose irradiation has been made by implanting nitrogen into the BOX layers with a constant dose at different implantation energies. The total-dose radiation hardness of the BOX layers is characterized by the high frequency capacitance-voltage (C-V) technique. The experimental results show that the implantation of nitrogen into the BOX layers can increase the BOX hardness to total-dose irradiation. Particularly, the implantation energy of nitrogen ions plays an important role in improving the radiation hardness of the BOX layers. The optimized implantation energy being used for a nitrogen dose, the hardness of BOX can be considerably improved. In addition, the C-V results show that there are differences between the BOX capacitances due to the different nitrogen implantation energies.

Effect of the technology of implanting nitrogen into buried oxide on the radiation hardness of the top gate oxide for partially depleted SOIPMOSFET

The effect of implanting nitrogen into buried oxide on the top gate oxide hardness against total irradiation does has been investigated with three nitrogen implantation doses (8 x 10(15), 2 x 10(16) and 1 x 10(17) cm(-2)) for partially depleted SOI PMOSFET. The experimental results reveal the trend of negative shift of the threshold voltages of the studied transistors with the increase of nitrogen implantation dose before irradiation. After the irradiation with a total dose of 5 x 10(5) rad(Si) under a positive gate voltage of 2V, the threshold voltage shift of the transistors corresponding to the nitrogen implantation dose 8 x 10(15) cm(-2) is smaller than that of the transistors without implantation. However, when the implantation dose reaches 2 x 10(16) and 1 x 10(17) cm(-2), for the majority of the tested transistors, their top gate oxide was badly damaged due to irradiation. In addition, the radiation also causes damage to the body-drain junctions of the transistors with the gate oxide damaged. All the results can be interpreted by tracing back to the nitrogen implantation damage to the crystal lattices in the top silicon.

Improved neutron radiation hardness for Si detectors: Application of low resistivity starting material and or manipulation of N-eff by selective filling of radiation-induced traps at low temperatures

Radiation-induced electrical changes in both space charge region (SCR) of Si detectors and bulk material (BM) have been studied for samples of diodes and resistors made on Si materials with different initial resistivities. The space charge sign inversion fluence (Phi(inv)) has been found to increase linearly with the initial doping concentration (the reciprocal of the resistivity), which gives improved radiation hardness to Si detectors fabricated from low resistivity material. The resistivity of the BM, on the other hand, has been observed to increase with the neutron fluence and approach a saturation value in the order of hundreds k Omega cm at high fluences, independent of the initial resistivity and material type. However, the fluence (Phi(s)), at which the resistivity saturation starts, increases with the initial doping concentrations and the value of Phi(s) is in the same order of that of Phi(inv) for all resistivity samples. Improved radiation hardness can also be achieved by the manipulation of the space charge concentration (N-eff) in SCR, by selective filling and/or freezing at cryogenic temperatures the charge state of radiation-induced traps, to values that will give a much smaller full depletion voltage. Models have been proposed to explain the experimental data.

Radiation hardness characteristic of N-implanted and F-implanted SIMOX/NMOSFET

Radiation hardness of SIMOX(separation by implanted oxygen)/NMOSFET by implanting N and F ion has been carefully studied in this paper.Both N and F ion implantation can reduce hole traps in the buried oxide and the interfacial regions,which consequently improves the radiation hardness,especially under high dose radiation conditions.Moreover,experimental data show that the higher dose of the N and F ion implantation is,the better radiation hardness is achieved.In order to minimize the influence on the threshold voltage of devices,it is important to choose suitable implantation dose and energy of N or F implantation that have smaller impact on the preradiation device performance.

Sensitivity of Total-Dose Radiation Hardness of SIMOX Buried Oxides to Doses of Nitrogen Implantation into Buried Oxides

In order to improve the total-dose radiation hardness of the buried oxides(BOX) in the structure of separa tion-by-implanted-oxygen(SIMOX) silicon-on-insulator(SOI), nitrogen ions are implanted into the buried oxides with two different doses,2 × 1015 and 3 × 1015 cm-2 , respectively. The experimental results show that the radiation hardness of the buried oxides is very sensitive to the doses of nitrogen implantation for a lower dose of irradiation with a Co-60 source. Despite the small difference between the doses of nitrogen implantation, the nitrogen-implanted 2 × 1015 cm-2 BOX has a much higher hardness than the control sample (i. e. the buried oxide without receiving nitrogen implantation) for a total-dose irradiation of 5 × 104rad(Si), whereas the nitrogen-implanted 3 × 1015 cm-2 BOX has a lower hardness than the control sample. However,this sensitivity of radiation hardness to the doses of nitrogen implantation reduces with the increasing total-dose of irradiation (from 5 × 104 to 5 × 105 rad (Si)). The radiation hardness of BOX is characterized by MOS high-frequency (HF) capacitance-voltage (C-V) technique after the top silicon layers are removed. In addition, the abnormal HF C-V curve of the metal-silicon-BOX-silicon(MSOS) structure is observed and explained.

Improved neutron radiation hardness for Si detectors: Application of low resistivity starting material and or manipulation of N-eff by selective filling of radiation-induced traps at low temperatures

Radiation-induced electrical changes in both space charge region (SCR) of Si detectors and bulk material (BM) have been studied for samples of diodes and resistors made on Si materials with different initial resistivities. The space charge sign inversion fluence (Phi(inv)) has been found to increase linearly with the initial doping concentration (the reciprocal of the resistivity), which gives improved radiation hardness to Si detectors fabricated from low resistivity material. The resistivity of the BM, on the other hand, has been observed to increase with the neutron fluence and approach a saturation value in the order of hundreds k Omega cm at high fluences, independent of the initial resistivity and material type. However, the fluence (Phi(s)), at which the resistivity saturation starts, increases with the initial doping concentrations and the value of Phi(s) is in the same order of that of Phi(inv) for all resistivity samples. Improved radiation hardness can also be achieved by the manipulation of the space charge concentration (N-eff) in SCR, by selective filling and/or freezing at cryogenic temperatures the charge state of radiation-induced traps, to values that will give a much smaller full depletion voltage. Models have been proposed to explain the experimental data.

Influence of nitrogen implantation into the buried oxide on the radiation hardness of silicon-on-insulator wafers

摘要: In order to improve the total-dose radiation hardness of the buried oxide of separation by implanted oxygen silicon-on-insulator wafers, nitrogen ions were implanted into the buried oxide with a dose of 10(16)cm(-2), and subsequent annealing was performed at 1100 degrees C. The effect of annealing time on the radiation hardness of the nitrogen implanted wafers has been studied by the high frequency capacitance-voltage technique. The results suggest that the improvement of the radiation hardness of the wafers can be achieved through a shorter time annealing after nitrogen implantation. The nitrogen-implanted sample with the shortest annealing time 0.5 h shows the highest tolerance to total-dose radiation. In particular, for the 1.0 and 1.5 h annealing samples, both total dose responses were unusual. After 300-krad(Si) irradiation, both the shifts of capacitance-voltage curve reached a maximum, respectively, and then decreased with increasing total dose. In addition, the wafers were analysed by the Fourier transform infrared spectroscopy technique, and some useful results have been obtained.

Theoretical analysis of the relationships between hardness, elastic modulus, and the work of indentation for work-hardening materials

In our previous paper, the expanding cavity model (ECM) and Lame solution were used to obtain an analytical expression for the scale ratio between hardness (H) to reduced modulus (E-r) and unloading work (W-u) to total work (W-t) of indentation for elastic-perfectly plastic materials. In this paper, the more general work-hardening (linear and power-law) materials are studied. Our previous conclusions that this ratio depends mainly on the conical angle of indenter, holds not only for elastic perfectly-plastic materials, but also for work-hardening materials. These results were also verified by numerical simulations.

Influence of Contact Geometry on Hardness Behavior in Nano-indentation

In this paper the influence of contact geometry, including the round tip of the indenter and the roughness of the specimen, on hardness behavior for elastic plastic materials is studied by means of finite element simulation. We idealize the actual indenter by an equivalent rigid conic indenter fitted smoothly with a spherical tip and examine the interaction of this indenter with both a flat surface and a rough surface. In the latter case the rough surface is represented by either a single spherical asperity or a dent (cavity). Indented solids include elastic perfectly plastic materials and strain hardening elastic-plastic materials, and the effects of the yield stress and strain hardening index are explored. Our results show that due to the finite curvature of the indenter tip the hardness versus indentation depth curve rises or drops (depending on the material properties of the indented solids) as the indentation depth decreases, in qualitative agreement with experimental results. Surface asperities and dents of curvature comparable to that of the indenter tip can appreciably modify the hardness value at small indentation depth. Their effects would appear as random variation in hardness.

Bulk ultrafine binderless (W0.4Al0.6)C prepared by high pressure sintering

Pure (W0.4Al0.6)C powder of about 1 mu m in diameter was sintered by the high pressure sintering (HPS) process without the addition of any binder phase. The microstructure, Vickers micro hardness and density versus the sintering time and temperature are well described. The most suitable sintering condition under pressure of 4.5 GPa is 1873 K for 8 min. Under this sintering condition, the hardness can reach 2295 kg mm(-2) and the relative density can reach 98.6%.

High-pressure sintering study of a novel hard material (W0.5Al0.5)C-0.5 without binder metal

A novel hard material of (W0.5Al0.5)C-0.5 has been successfully sintered under high-pressure (4.5 GPa). The influence of sintering time and temperature on the microstructure, Vickers microhardness and density of the as-prepared specimens are well described. Interestingly, sintering temperature has an amazing influence on the hardness, density and microstructure of the specimen while the sintering time does not. It is found that the most suitable sintering condition from our work is 1600 degrees C and 10 min under pressure of 4.5 GPa. The hardness and relative density of the as-prepared sample can reach 2340 kg mm(-2) and 98.62%, respectively. The cell parameters of the sintered specimen is found to be little smaller than that of the powder, which we propose is related to the high pressure.

Hardness of covalent crystals

Based on the idea that the hardness of covalent crystal is intrinsic and equivalent to the sum of the resistance to the indenter of each bond per unit area, a semiempirical method for the evaluation of hardness of multicomponent crystals is presented. Applied to beta-BC2N crystal, the predicted value of hardness is in good agreement with the experimental value. It is found that bond density or electronic density, bond length, and degree of covalent bonding are three determinative factors for the hardness of a polar covalent crystal. Our method offers the advantage of applicability to a broad class of materials and initializes a link between macroscopic property and electronic structure from first principles calculation.