Effect of F doping on capacitance－voltage characteristics of SiCOH low-k films metal－insulator－semiconductor structure

This paper investigates the capacitance--voltage ($C$--$V$) characteristics of F doping SiCOH low dielectric constant films metal--insulator--semiconductor structure. The F doping SiCOH films are deposited by decamethylcyclopentasiloxane (DMCPS) and trifluromethane (CHF7755, 6855http://cpb.iphy.ac.cn/CN/10.1088/1674-1056/19/5/057701https://cpb.iphy.ac.cn/CN/article/downloadArticleFile.do?attachType=PDF&id=111779F-SiCOH, low-k dielectrics, capacitance--voltage characteristicProject supported by the National Natural Science Foundation of China (Grant No.~10575074).2/4/2009 12:00:00 AMThis paper investigates the capacitance--voltage ($C$--$V$) characteristics of F doping SiCOH low dielectric constant films metal--insulator--semiconductor structure. The F doping SiCOH films are deposited by decamethylcyclopentasiloxane (DMCPS) and trifluromethane (CHF$_{3})$ electron cyclotron resonance plasmas. With the CHF$_{3}$/DMCPS flow rate ratio from 0 to 0.52, the positive excursion of $C$--$V$ curves and the increase of flat-band voltage $V_{\rm FB}$ from $-6.1$~V to 32.2~V are obtained. The excursion of $C$--$V$ curves and the shift of $V_{\rm FB}$ are related to the change of defects density and type at the Si/SiCOH interface due to the decrease of Si and O concentrations, and the increase of F concentration. At the CHF$_{3}$/DMCPS flow rate ratio is 0.12, the compensation of F-bonding dangling bond to Si dangling bond leads to a small $V_{\rm FB}$ of 2.0~V.半导体结构;电压特性;电容电压;绝缘体;薄膜;金属;电子回旋共振等离子体;兴奋剂This paper investigates the capacitance-voltage （C-V） characteristics of F doping SiCOH low dielectric constant films metal-insulator-semiconductor structure. The F doping SiCOH films are deposited by decamethylcyclopentasilox-ane [DMCPS） and trifluromethane （CHF3） electron cyclotron resonance plasmas. With the CHF3/DMCPS flow rate ratio from 0 to 0.52, the positive excursion of C-V curves and the increase of fiat-band voltage VFB from -6.1 V to 32.2V are obtained. The excursion of C-V curves and the shift of VFB are related to the change of defects density and type at the Si/SiCOH interface due to the decrease of Si and O concentrations, and the increase of F concentration. At the CHF3/DMCPS flow rate ratio is 0.12, the compensation of F-bonding dangling bond to Si dangling bond leads to a small VFB of 2.0V.     

CHF3 Dual-Frequency Capacitively Coupled Plasma by Optical Emission Spectroscopy

We investigate the intermediate gas phase in the CHFs 13.56 MHz/2 MHz dual-frequency capacitively couple plasma （CCP） for the SiCOH low dielectric constant （low-k） film etching, and the effect of 2MHz power on radicals concentration. The major dissociation reactions of CHF3 in 13.56MHz CCP are the low dissociation bond energy reactions, which lead to the low F and high CF2 concentrations. The addition of 2MHz power can raise the probability of high dissociation bond energy reactions and lead to the increase of F concentration while keeping the CF2 concentration almost a constant, which is of advantage to the SiCOH low-k films etching. The radical spatial uniformity is dependent on the power coupling of two sources. The increase of 2 MHz power leads to a poor uniformity, however, the uniformity can be improved by increasing 13.56 MHz power.     

Si—OH基团对SiCOH低k薄膜性能的影响与控制

研究了十甲基环五硅氧烷(D5)的电子回旋共振等离子体沉积的SiCOH薄膜中Si—OH基团对介电性能和漏电流的影响.结果表明Si—OH含量的增大会导致介电常数k的增大、漏电流的降低和介电色散的增强.由于Si—OH结构的强极化补偿了薄膜密度减小带来的介电常数降低，导致总的介电常数k增大.高Si—OH含量下漏电流的降低是由于封端的Si—OH基团降低了薄膜中Si—O网络的连通概率p而导致网络电导下降的缘故.介电色散的增强与Si—OH封端结构的快极化过程有关.改变放电参数以提高电子能量，从而提高源的电离程度，使更多的Si—OH基团断裂并通过缩合反应形成Si—O—Si网络，可以进一步降低薄膜的介电常数. 关键词： SiCOH薄膜 Si—OH结构 介电性能 ECR放电等离子体     

Room-Temperature Ferromagnetic ZnMnO Thin Films Synthesized by Plasma Enhanced Chemical Vapour Deposition Method

Room-temperature ferromagnetic Mn-doped ZnO films are grown on Si （001） substrates by plasma enhanced chemical vapour deposition （PECVD）. X-ray diffraction measurements reveal that the Znl-xMn.O films have the single-phase wurtzite structure. X-ray photoelectron spectroscopy indicates the existence of Mn^2＋ ions in Mndoped ZnO films. Furthermore, the decreasing additional Raman peak with increasing Mn-doping is considered to relate to the substitution of Mn ions for the Zn ions in ZnO lattice. Superconducting quantum interference device （SQUID） measurements demonstrate that Mn-doped ZnO films have ferromagnetic behaviour at room temperature.     

improvement of electrical properties of Cu/SiCOH low-k film integrated system by O2 plasma treatment

This paper investigates the effect of O2 plasma treatment on the electric property of Cu/SiCOH low dielectric constant （low-k） film integrated structure. The results show that the leakage current of Cu/SiCOH low-k integrated structure can be reduced obviously at the expense of a slight increase in dielectric constant k of SiCOH films. Bythe Fourier transform infrared （FTIR） analysis on the bonding configurations of SiCOH films treated by O2 plasmar it is found that the decrease of leakage current is related to the increase of Si-O cages originating from the linkage of Si dangling bonds through O, which makes the open pores sealed and reduces the diffusion of Cu to pores.     

Defects in Si-Rich SiO2 Films Prepared by Radio-Frequency Magnetron Co-sputtering Using Variable Energy Positron Annihilation Spectroscopy

Si-rich SiO2 films prepared by rf magnetron co-sputtering method are studied by slow positron beams. The nega- tively charge point defects （probably Pb centres or peroxy radicals） at the silicon nanocluster （nc-Si）/SiO2 interface are observed by Doppler broadening spectra. Coincidence Doppler-broadening spectra show that positrons have a higher annihilation probability with core electrons nearby oxygen atoms than silicon atoms. The formation of N-related bonds may be the reason for the prevention of the migration reaction of Si and 0 atoms, hence nc-Si formation is inhibited by annealing in nitrogen compared to in vacuum.     

Temperature Dependence of Elastic Properties for Amorphous SiO2 by Molecular Dynamics Simulation

Large-scale and long-time molecular-dynamics simulations are used to investigate the temperature dependences of elastic properties for amorphous SiO2. The elastic moduli increase in a temperature range up to 1600 K and decrease thereafter. The anomalous behaviour in elasticity is explained by analysing the changes of atomic-scale structure with respect to increment of temperature. The mechanism originates predominantly from distortion of the SiO4 tetrahedra network in low-temperature ranges. At an elevated temperature range, thermal-induced Si-O bond stretching dominates the process and leads to normal temperature dependence of elastic properties.     

Oxygen Recovery in Hf Oxide Films Fabricated by Sputtering

The chemical structure of ultrathin Hf oxide films （〈 10 nm） fabricated by a standard sputtering method is investigated using x-ray spectroscopy and Rutherford backseattering spectroscopy. According to the experiments, oxygen species are impacted to the HfO2/Si interface during the initial sputtering, and then released back to the upper HfO2 region driven by the oxygen concentration grads. A vacuum annealing can greatly enhance this recovery process. Additionally, significant SiO2 reduction in the interface is observed after the vacuum annealing for the thick HfO2 films in our experiment. It might be an effective method to confine the interracial layer thickness by sputtering thick HfO2 in no-oxygen ambient.     

Measurement and Analysis of Composition and Depth Profile of H in Amorphous Si1-xCx:H Films

Composition in amorphous Si1-xCx：H heteroepitaxial thin films on Si （100） by plasma enhanced chemical vapour deposition （PECVD） is analysed. The unknown x （0.45-3.57） and the depth profile of hydrogen in the thin films are characterized by Rutherford backscattering spectrum （RBS）, resonance-nuclear reaction analysis （R-NRA） and elastic recoil detection （ERD）, respectively. In addition, the depth profile of hydrogen in the unannealed thin films is compared to that of the annealed thin films with rapid thermal annealing （RTA） or laser spike annealing （LSA） in nitrogen atmosphere. The results indicate that the stoichiometric amorphous SiC can be produced by PECVD when the ratio of CH4/SiH4 is approximately equal to 25. The content of hydrogen decreases suddenly from 35% to 1% after 1150℃ annealing. RTA can reduce hydrogen in SiC films effectively than LSA.     

CHx掺杂SiCOH 低介电常数薄膜的物性热稳定性分析

研究了真空热处理对掺CH₄的SiCOH低介电常数薄膜的电流-电压(I-V)特性、电容-电压(C-V)特性、疏水性能以及微结构的影响. 结果表明：在热处理过程中,热稳定性较差的碳氢基团发生了热解吸,使薄膜的漏电流减小、绝缘性能改善,并使薄膜的导电行为更趋于空间电荷限流过程. 碳氢基团的热解吸使SiCOH/Si界面的界面态发生改变,导致SiCOH薄膜MIS结构的平带电压V_FB发生漂移. 封端的碳氢 关键词： SiCOH薄膜 热处理 结构与性能     

SiCOH低介电常数薄膜的性质和键结构分析

以十甲基环五硅氧烷为反应源、采用电子回旋共振等离子体化学气相沉积（ECR_CVD）方法制备了具有低介电常数，且电绝缘性能和热稳定性优良的SiCOH薄膜. 通过对富氏变换红外光谱(FTIR)的分析，比较了反应源和薄膜键结构的差异，证实薄膜中一方面保持了源中由Si—O—Si键构成的环结构，另一方面形成了由大键角Si—O—Si键构成的鼠笼式结构，在沉积过程中失去的主要是侧链的—CH3基团. 薄膜经过400℃热处理后，其介电常数由385降低到285，对其FTIR谱的分析指出，薄膜中鼠笼式结构比例的增加可能是薄膜介电常数降低的原因. 关键词： 低介电常数 SiCOH薄膜 化学键结构     

Atomic Diffusion in Cu/Si （111） and Cu/SiO2/Si （111） Systems by Neutral Cluster Beam Deposition

The Cu films are deposited on two kinds of p-type Si （111） substrates by ionized duster beam （ICB） technique. The interface reaction and atomic diffusion of Cu/Si （111） and Cu/SiO2/Si （111） systems are studied at different annealing temperatures by x-ray diffraction （XRD） and Rutherford backscattering spectrometry （RBS）. Some significant results are obtained： For the Cu/Si （111） samples prepared by neutral dusters, the interdiffusion of Cu and Si atoms occurs when annealed at 230℃. The diffusion coefficients of the samples annealed at 230℃ and 500℃ are 8.5 ×10^-15 cm^2.s^-1 and 3.0 ×10^-14 cm^2.s^-1, respectively. The formation of the copper-silicide phase is observed by XRD, and its intensity becomes stronger with the increase of annealing temperature. For the Cu/SiO2//Si （111） samples prepared by neutral dusters, the interdiffusion of Cu and Si atoms occurs and copper silicides are formed when annealed at 450℃. The diffusion coefficients of Cu in Si are calculated to be 6.0 ×10^-16 cm^2.s^-1 at 450℃, due to the fact that the existence of the SiO2 layer suppresses the interdiffusion of Cu and Si.     

Characteristics of low-temperature-grown GaN films on Si(111)

In this paper, we report on the characteristics of GaN films grown on Si(111) at a low temperature (200 °C) by electron cyclotron resonance (ECR) plasma-assisted metalorganic chemical vapor deposition (PA-MOCVD). Structural analysis of the GaN films was performed by using scanning electron microscopy (SEM), atomic force miscroscopy (AFM), X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX), and Rutherford backscattering spectrometry (RBS). Post deposition analysis revealed high quality crystalline GaN was obtained at this low temperature. Electrical analysis of the GaN films was done by using current-voltage (I-V) measurements where electrical characterizations were carried on GaN/Si heterojunction and Schottky barrier diodes. Rectification behaviour was observed for the isotype GaN/Si (n-n) heterojunction. Ideality factors and Schottky barrier heights for Ni and Cr Schottky barriers on GaN, were deduced to be 1.4 and 1.7; and 0.62 and 0.64 eV, respectively.     

Hydrocarbon film growth by energetic CH3 molecule impact on SiC (0 0 1) surface

Classic molecular dynamics (MD) calculations were performed to investigate the deposition of thin hydrocarbon film. SiC (1 0 0) surfaces were bombarded with energetic CH₃ molecules at impact energies ranging from 50 to 150 eV. The simulated results show that the deposition yield of H atoms decreases with increasing incident energy, which is in good agreement with experiments. During the initial stages, with breaking Si-C bonds in SiC by CH₃ impacting, H atoms preferentially reacts with resulting Si to form Si-H bond. The C/H ratio in the grown films increases with increasing incident energy. In the grown films, CH species are dominant. For 50 eV, H-Csp3 bond is dominant. With increasing energy to 200 eV, the atomic density of H-Csp2 bond increases.     

Controlling crystal quality and orientation of pulsed-laser-deposited BaTiO3 thin films by the kinetic energy of the film-forming particles

The deposition of BaTiO₃ thin films by pulsed excimer laser radiation (248 nm) on Pt/Ti/Si(111) and Pt/Ti/Si(100) substrates is investigated as a function of the processing variables laser fluence, processing gas pressure, and target-to-substrate distance under conditions of temporal and spatial properties of the involved vapour and plasma states. The kinetic energy of the species in the laser-generated plasma, as measured by time-of-flight optical emission spectroscopy and time-of-flight quadrupole mass spectrometry, is described as a function of the pressure of the processing gas, the distance from the target, and the laser fluence. The influence of the kinetic energy of the film-forming particles on the crystalline structure, defects, and orientation, and on the resulting electrical properties of the films is investigated. X-ray diffraction measurements and polarisation-dependent micro-Raman measurements reveal a c-axis orientation normal to the substrate surface, in the case of high particle energy (>50 eV), whereas at low kinetic energies (<30 eV) a [111]_pc or [110]_pc orientation is preferred. The ferroelectricity and the dielectric constant of the films, determined by impedance measurements, decrease with increasing kinetic energy of the film-forming particles from )_r=1000-2200 to )_r=200-700. This decrease correlates with the change of the orientation and with an increasing lattice constant of the films, indicating that particles with high kinetic energies produce crystal defects and stress in the growing film.     

Growth of SiNx and SiCx thin films by pulsed reactive crossed-beam laser ablation

SiN_x and SiC_x films were grown on Si(001) and Si(111) using pulsed reactive crossed-beam laser ablation of Si with N₂ and CH₄. The scattering processes in the ablation plasma and the reactive gas pulse were investigated using time-of-flight quadrupole mass spectroscopy. The film crystallinity was determined by FTIR spectroscopy, X-ray diffraction, and reflection high-energy electron diffraction, while the stoichiometry and chemistry were investigated using XPS. SiN_x was amorphous over the investigated temperature range of 25-850 °C, and x increased monotonically with temperature from 0.67 to 0.94. SiC_x films grown at 850 °C consisted of oriented large #-SiC crystallites embedded in a Si matrix.     

Influence of Different Substrates on Laser Induced Damage Thresholds at 1064nm of Ta2O5 Films

Ta2O5 films are prepared on Si, BK7, fused silica, antireflection （AR） and high reflector （HR） substrates by electron beam evaporation method, respectively. Both the optical property and laser induced damage thresholds （LIDTs） at 1064 nm of Ta2O5 films on different substrates are investigated before and after annealing at 673 K for 12 h. It is shown that annealing increases the refractive index and decreases the extinction index, and improves the O/Ta ratio of the Ta2O5 films from 2.42 to 2.50. Moreover, the results show that the LIDTs of the Ta2O5 films are mainly correlated with three parameters： substrate property, substoichiometry defect in the films and impurity defect at the interface between the substrate and the films. Details of the laser induced damage models in different cases are discussed.     

Organic contaminants removal by oxygen ECR plasma

Recently electron cyclotron resonance (ECR) plasma have been explored for wafer cleaning applications, since it is known to do less damage to silicon surface than conventional plasma. Organic contaminants removal efficiency and plasma radiation damage of the ECR plasma cleaning have been investigated. In oxygen ECR plasma cleaning, the plasma exposure time needed to remove the organic contaminants on the silicon surface down to the detection limit is 40 s, but the one to reach the lowest surface roughness is 10 s. The leakage current level of the MOS capacitor made using the Si substrate exposed to oxygen ECR plasma for 40 s is 8 × 10⁻⁹ A. The optimum exposure time determined by considering the contaminants removal efficiency and the plasma radiation damage (or the leakage current level) is 40 s. Organic contaminants seem to be removed through both sputter-off mechanism by oxygen ion bombardment and evaporation mechanism by chemical reactions with excited oxygen atoms.     

Realization of Ultraviolet Electroluminescence from ZnO Homojunction Fabricated on Silicon Substrate with p-Type ZnO:N Layer Formed by Radical N2O Doping

ZnO homojunction light-emitting diodes are fabricated on Si（100） substrates by plasma assisted metal organic chemical vapour deposition. A p-type layer of nitrogen-doped ZnO film is formed using radical N2O as the acceptor precursor. The n-type ZnO layer is composed of un-doped ZnO film. The device exhibits desirable rectifying behaviour with a turn-on voltage of 3.3 V and a reverse breakdown voltage higher than 6 V. Distinct electrolumineseence emissions centred at 395nm and 490nm are detected from this device at forward current higher than 20mA at room temperature.     

Transport Behaviour of La0.8Sr0.2AlO3 Thin Film on Oxygen Deficient SrTiO3 Substrate

La_0.8Sr_0.2AlO₃ (LSAO) thin films are grown on SrTiO₃ (STO) and MgO substrates by laser molecular beam epitaxy. The LSAO thin film on oxygen deficient STO substrate exhibits metallic behaviour over the temperature range of 80--340K. The optical transmittance spectrum indicates that theLSAO thin films on MgO substrate are insulating at room temperature. The transport properties of LSAO thin films on STO substrates deposited in different oxygen pressure are compared. Our results indicate that oxygen vacancies in STO substrates should be mainly responsible for the transport behaviour of LSAO thin films.