Cu/SiO2/Si(111)体系中Cu和Si的扩散及界面反应

室温下利用磁控溅射在p型Si(111)衬底上沉积了Cu薄膜.利用X射线衍射和卢瑟福背散射分别对未退火以及在不同温度点退火后样品的结构进行了表征.在此基础上,研究了Cu/SiO2/Si(111)体系的扩散和界面反应.实验结果表明:当退火温度高于450 ℃时出现明显的扩散现象,并且随着温度的升高,体系扩散现象会更加显著.当退火温度低于450 ℃时没有铜硅化合物生成,当温度达到500 ℃时才有铜硅化合物生成.     

Poole-Frenkel conduction in Al/ZrO2 /SiO 2 /Si structures

Leakage currents through Al/ZrO₂/SiO₂/n-Si metal-insulator-semiconductor (MIS) capacitors were studied. Thin SiO₂ films were chemically grown on monocrystalline phosphorous doped silicon wafers. Zirconia films with thicknesses of 15 and 50 nm were deposited by radio frequency (rf) magnetron sputtering and, then, annealed in oxygen ambient at 850 ^○C, for 1 h. The dielectric constant of the sputtered and annealed ZrO₂ layer was of about 17.8. The equivalent oxide thickness (EOT) of the stack 15 nm and 50 nm-ZrO₂/SiO₂ structure was estimated to be 3.2 nm and 10.7 nm, respectively. The temperature dependence of the leakage currents was explained by Poole-Frenkel (PF) conduction mechanism. Shallow trap levels in the studied structure of about 0.2 eV and 0.46 eV were calculated. The existence of A and D-defects, due to the sputtering and high temperature annealing in oxygen, was suggested.     

Physical and mechanical properties of silicon near the SiO2/Si interface

The influence of an oxide coating on the strength characteristics of single-crystal silicon surface layers is investigated by the microindentation method. It is shown experimentally that a strengthened layer with a thickness of 0.2–0.4 μm and a microhardness of 20–35 GPa, which is two or three times as much as the microhardness of bulk single-crystal silicon, is present near the SiO₂/Si interface. The thickness and microhardness of this layer depends on the growth conditions of the oxide. The formation of this layer is most probably caused by interstitial silicon atoms formed near the SiO₂/Si interface during silicon oxidation.     

New structural model for Si/SiO2 interfaces derived from spherosiloxane clusters: implications for Si 2p photoemission spectroscopy

In this Letter, we investigate the Si/SiO(2) interface structure formed by the chemisorption of H8Si8O12 and other spherosiloxane clusters on Si(100). Using transition state calculations, we clearly demonstrate that the clusters do not bond to the Si(100) surface via single vertex attachment as proposed previously, but rather attach via Si-O bond cleavage. This alternative cracked cluster geometry allows us to predict the photoemission features of spherosiloxane clusters on Si(100) without invoking second nearest neighbor effects.     

Electronic properties of the Si/SiO2 interface from first principles

Unoccupied oxygen p-projected densities of states, calculated from first principles in a model Si/SiO(2) interface, are found to reproduce trends in recent atomic resolution electron energy-loss spectra [D. A. Muller et al., Nature (London) 399, 758 (1999)]. The shape of the unoccupied states and the magnitude of the local energy gap are explicitly related to the number of O second neighbors of a given oxygen atom. The calculated local energy gaps of the oxide become considerably smaller within 0.5 nm of the interface, suggesting that the electronic properties do not change abruptly at the interface.     

Electrical characteristics of the rf-excited oxygen plasma-cathodization-grown SiO2/Si interface

The electrical properties of the SiO₂/n-type Si(100) interface, where the silicon-oxide layer was grown by an electrodeless rf oxygen-plasma-cathodization technique, were investigated usingC-V and DLTS methods. Interface traps with high density in the range of 10¹² eV^–1 cm^–2 and a capture cross section as large as 10^–18 cm² were found in the upper region of the silicon forbidden gap. After a post-annealing process, typically at 400°C for 30 min in dry N₂ atmosphere, their densities and capture cross sections were reduced to the range of 1–2 × 10¹¹ eV^–1 cm^–2 and 10^–19 cm^–2, respectively. Apparant differences in DLTS curves before and after thermal annealing were also observed. Results are qualitatively explained by considering the specific oxidation and annealing mechanism of this low-temperature silicon-oxidation technique.     

ESR observation of phosphorus pile-up at the Si/SiO2 interface in boron-doped Si

It is shown that dry thermal oxidation of B-doped (p-type) CZ-grown Si wafers may create P-rich near-interfacial Si layers. Thermal treatments were mostly carried out at T_ox=950±20°C for times 3 ≲ t_ox ≲ 7 h in either a 0.11 MPa high-purity O₂ ambient or strongly-reduced O₂ pressure (p_o2 ≲ 13 mPa). The existence of such layers was discovered by sensitive low T ESR observations, revealing the typical P³¹-in-(n-type) Si spectrum. These measurements in combination with selective etching experiments and number-of-spins determinations showed these surface layers to be actually semiconductor-type reversed. It is argued that the P atoms collected at the Si/SiO₂ interface during thermal treatments are inherently present as bulk impurities in the as-received Si.     

First-principles calculations of the hole-induced depassivation of SiO2/Si interface defects

The holes induced by ionizing radiation or carrier injection can depassivate saturated interface defects. The depassivation of these defects suggests that the deep levels associated with the defects are reactivated, affecting the performance of devices. This work simulates the depassivation reactions between holes and passivated amorphous-SiO₂/Si interface defects (HP_b+h→ P_b+H⁺). The climbing image nudged elastic band method is used to calculate the reaction curves and the barriers. In addition, the atomic charges of the initial and final structures are analyzed by the Bader charge method. It is shown that more than one hole is trapped by the defects, which is implied by the reduction in the total number of valence electrons on the active atoms. The results indicate that the depassivation of the defects by the holes actually occurs in three steps. In the first step, a hole is captured by the passivated defect, resulting in the stretching of the Si-H bond. In the second step, the defect captures one more hole, which may contribute to the breaking of the Si-H bond. The H atom is released as a proton and the Si atom is three-coordinated and positively charged. In the third step, an electron is captured by the Si atom, and the Si atom becomes neutral. In this step, a P_b-type defect is reactivated.     

Band offsets at the Si/SiO2 interface from many-body perturbation theory

We use many-body perturbation theory, the state-of-the-art method for band-gap calculations, to compute the band offsets at the Si/SiO2 interface. We examine the adequacy of the usual approximations in this context. We show that (i) the separate treatment of band structure and potential lineup contributions, the latter being evaluated within density-functional theory, is justified, (ii) most plasmon-pole models lead to inaccuracies in the absolute quasiparticle corrections, (iii) vertex corrections can be neglected, and (iv) eigenenergy self-consistency is adequate. Our theoretical offsets agree with the experimental ones within 0.3 eV.     

Confined micro-explosion induced by ultrashort laser pulse at SiO2/Si interface

Ultrashort laser pulses tightly focused inside a transparent material present an example of laser interaction with matter where all the laser-affected material remains inside the bulk, thus the mass is conserved. In this paper, we present the case where the high intensity of a laser pulse is above the threshold for optical breakdown, and the material is ionised in the focal area. We consider in detail a special case where a micro-explosion is formed at the boundary of a silicon surface buried under a 10-micron-thick oxidised layer, providing the opportunity to affect the silicon crystal by a strong shock wave and creating new material phases from the plasma state. We summarise the main conclusions on ultrafast laser-induced material modifications in confined geometry and discuss the prospects of confined micro-explosion for forming new silicon phases.     

Oxidation at the Si/SiO2 interface: influence of the spin degree of freedom

We show, using first-principles spin-polarized total-energy calculations, that depending on the spin configuration of the system, the reaction of an O2 molecule with a Si-Si bond in a suboxidized region might result either in a peroxy linkage defect (for a singlet spin state) or in a perfect Si-O-Si bond plus an interstitial O atom (for a triplet spin state). Even though the singlet has a lower energy than the triplet configuration, we find a rather small probability for triplet to singlet conversion. Therefore, as the O2 in an SiO2 interstitial site has a triplet configuration, this reaction spin dependence may have a strong influence on the high quality of the Si/SiO2 interface.     

Simulation of range profiles for boron implantation into SiO2/Si and Si3N4/SiO2/Si targets

The simple method of profile combination is shown to be applicable to the simulation of boron profiles in SiO₂/Si and Si₃N₄/Si layered targets. This is demonstrated by comparison with range distributions calculated by more sophisticated theoretical methods, i.e. TRIM Monte Carlo simulations and the algorithm of Christel et al., and with experimental data. The method of profile combination can also be applied to layered targets with a crystalline silicon substrate.     

Acoustic spectroscopy and electrical characterization of SiO2/Si structures with ultrathin SiO2 layers formed by nitric acid oxidation

Ultrathin silicon dioxide (SiO₂) layers formed on Si substrate with nitric acid have been investigated using both acoustic deep-level transient spectroscopy (A-DLTS) and electrical methods to characterize the interface states. The set of SiO₂/Si structures formed in different conditions (reaction time, concentrations of nitric acid (HNO₃), and SiO₂ thickness [3–9 nm]) was prepared. The leakage current density was decreased by post-oxidation annealing (POA) treatment at 250°C in pure nitrogen for 1 h and/or post-metallization annealing (PMA) treatment at 250°C in a hydrogen atmosphere for 1 h. All structures of the set, except electrical investigation, current-voltage (I - V), and capacitance — voltage (C - V) measurements, were investigated using A-DLTS to find both the interface states distribution and the role of POA and/or PMA treatment on the interface-state occurrence and distribution. The evident decreases of interface states and shift of their activation energies in the structures with PMA treatment in comparison with POA treatment were observed in most of the investigated structures. The results are analyzed and discussed.      

The optically detected magnetic resonance of dangling bonds at the Si/SiO2 interface

The optically detected magnetic resonance (ODMR) observation of dangling bonds at the Si/SiO₂ interface (P_b centers) is reported in this Communication. A luminescence quenching signal is identified as arising from the P_b center through its axially symmetry g tensor along the <1 1 1#62; direction. The negative sign observed for both the P_b center and the neutral phosphorus donor resonances allows us to interpret the recombination mechanism as a spin dependent electron transfer from the phosphorus donor to the P_b center.     

掺杂Si/SiO_2界面电子结构与光学性质的第一性原理研究

采用基于密度泛函理论的第一性原理方法,在局域密度近似(LDA)下研究了B掺杂Si/SiO_2界面及其在压强作用下的电子结构和光学性质.能带的计算结果表明:掺杂前后Si/SiO_2界面均属于直隙半导体材料,但掺B后界面带隙由0. 74 eV减小为0. 57 eV,说明掺B使材料的金属性增强;对B掺杂Si/SiO_2界面施加正压强,发现随着压强不断增大,Si/SiO_2界面的带隙呈现了逐渐减小的趋势,并且由直隙逐渐转变为间隙.光学性质的计算结果表明:掺B对Si/SiO_2界面在低能区(即红外区)的介电函数虚部、吸收系数、折射率以及反射率等光学参数有显著影响,且在红外区出现新的吸收峰;对B掺杂Si/SiO_2界面施加正压强,随着压强增大,红外区的吸收峰逐渐消失,而在紫外区出现了吸收峰.上述结果表明,对Si/SiO_2界面掺B及施加正压强均可调控Si/SiO_2界面的电子结构与光学性质.本文的研究为基于Si/SiO_2界面的光电器件研究与设计提供一定的理论参考.     

Formation of defects in the oxide layer of ion-irradiated Si/SiO2 structures

Electroluminescence and high-frequency voltage-capacitance methods are used to study Si/SiO₂ structures obtained by thermal oxidation of KéF-5 (100)Si wafers at 950°C in wet oxygen (oxide thickness 250 nm). The structures are irradiated by 130-keV argon ions with doses in the range of 10¹³−3.2×10¹⁷ cm⁻². A correlation between the origin, properties, and formation mechanism of implantation-induced defects in the oxide layer is established, and a model of defect formation is proposed.