CHF3双频电容耦合放电等离子体特性研究

研究了用于SiCOH 低介电常数薄膜刻蚀的CHF₃气体在1356 MHz/2 MHz,2712 MHz/2 MHz和60 MHz/2 MHz双频电容耦合放电时的等离子体性质.发现2 MHz低频源功率的增大主要导致F基团密度的增大;而高频频率从1356,2712增大到60 MHz,导致CF₂基团的密度增大和电极之间F基团密度的轴向空间不均匀性增加.根据电子温度的分布规律及离子能量随高频源频率的变化关系,提出CF₂基团的产生主要通过电子-中性气体碰撞,而F基团的产生是离子-中性气体碰撞的结果. 关键词： 双频电容耦合放电 3等离子体')" href="#">CHF₃等离子体     

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.     

N_2-H_2容性耦合等离子体电非对称效应的particle-in-cell/Monte Carlo模拟

H_2-N_2混合气体电容性耦合射频放电在有机低介电系数材料刻蚀中具潜在研究意义.采用paxticle-incell/Monte Carlo模型模拟了双频(13.56 MHz/27.12 MHz)电压源分别接在结构对称的两个电极上的H_2-N_2容性耦合等离子体特征,研究了其电非对称效应.模拟结果表明,通过调节两谐波间的相位角θ,可以改变其电场、等离子体密度、离子流密度的轴向分布及离子轰击电极的能量分布.当相位角θ为0°时,低频电极(晶片)附近主要离子(H_3~+)的密度最小,离子(H_3~+,H_2~+,H~+)轰击低频电极的流密度及平均能量最高;当θ从0°变化90°时,低频电极的自偏压从-103V到106V近似线性增加,轰击电极的离子流密度变化约±18%,H~+离子轰击低频电极的最大能量约减小2.5倍,轰击电极的平均能量约变化2倍,表明氢离子能量和离子流几乎能独立控制.     

Low-temperature PECVD of silicon dioxide on polymeric hydrogels

In this work, a complex investigation of the film surface composition and nanoscale mechanical properties, i.e. hardness and elastic modulus, of plasma-modified and silica-coated hydrogel thin films was carried out. Plasma treatment was performed in a reactive ion etching chamber (SF₆, CHF₃) at radio frequency (rf, 13.56 MHz) and in a plasma-enhanced chemical vapor deposition chamber (SiH₄/N₂, NH₃, N₂O) at radio frequency and dual frequency (13.56 MHz/100 kHz), respectively. The use of the dual-frequency configuration comprising two power supplies and operated in a switched mode enabled the investigation of the ion-bombardment influence on the polymer properties. For the application in silicon micromachined sensors best results were obtained by using a NH₃ or SiH₄/N₂ low-pressure plasma modification and a silica coating of the sensitive hydrogel film. PACS 81.05.Lg; 81.15.Gh; 81.65.Cf; 81.70.Bt     

Theoretical investigation on kinetics and thermochemistry of reaction of CHF2CF2OCH2CF3 with OH radicals and global warming potentials

Theoretical investigation has been carried out on the mechanism, kinetics and thermochemistry of the gas-phase reactions between CHF₂CF₂OCH₂CF₃ and OH radical using a new hybrid density functional M06-2X/6-31+G(d,p) and G2(MP2)//M06-2X/6-31+G(d,p) methods. The most stable conformer of CHF₂CF₂OCH₂CF₃ is considered in our study and the possible H-abstraction reaction channels are identified. Each reaction channel shows an indirect H-abstraction reaction mechanism via the formation of pre-reactive complex. The rate coefficients are determined for the first time over a wide range of temperature 250–1000 K. At 298 K, the calculated total rate coefficient of k_OH = 1.01×10^?14 cm³ molecule^?1 s^?1 is in good agreement with the experimental results. The heats of formation for CHF₂CF₂OCH₂CF₃ and CF₂CF₂OCH₂CF₃ and CHF₂CF₂OCHCF₃ radicals are estimated to be -1739.25, -1512.93 and -1523.94 kJ mol^?1, respectively. The bond dissociation energies of the two C-H bonds are C(-H)F₂CF₂OCH₂CF₃: 423.34 kJ mol^?1 and CHF₂CF₂OC(-H)HCF₃: 411.87 kJ mol^?1. The atmospheric lifetime of CHF₂CF₂OCH₂CF₃ is estimated to be around 4.5 years and the 100-year time horizon global warming potentials of CHF₂CF₂OCH₂CF₃ relative to CO₂ is estimated to be 601.     

Isotopically selective infrared multiphoton dissociation of 2-chloro-1,1,1-trifluoroethane: 13C selectivity and mechanism

13 C-selective infrared multiphoton dissociation of CF₃CH₂Cl has been studied by analyzing the distribution of ¹³C concentrations of the main products CF₂=CHCl, CF₂=CH₂, CF₂=CHF, C₂F₆, and the trace products CF₃CH₂CF₃ and CF₃CH=CHF₃. The mechanism mainly concerns the dissociation of energized CF₃CH₂Cl, the collisional stabilization of excited CF₃CH and CF₃CH₂ and the recombination of the nascent radicals. No significant radical–molecule reactions degrade the intrinsic ¹³C dissociation selectivity. High ¹³C production yield and ¹³C concentration can be attained at a laser fluence of 1.6 J/cm². Such low fluence can be used to improve focus condition and enhance photon utilization efficiency for practicable ¹³C separation. Received: 10 March 1998/Revised version: 17 September 1998     

Characteristics of a dual‐radio‐frequency cylindrical inductively coupled plasma

The plasma parameters such as electron density, effective electron temperature, plasma potential, and uniformity are investigated in a new dual‐frequency cylindrical inductively coupled plasma (ICP) source operating at two frequencies (2 and 13.56 MHz) and two antennas (a two‐turn high‐frequency antenna and a six‐turn low‐frequency (LF) antenna). It is found that the electron density increases with 2 MHz power, whereas the electron temperature and plasma potential decrease with 2 MHz power at a fixed 13.56 MHz power. Moreover, the plasma uniformity can be improved by adjusting the LF power. These results indicate that a dual‐frequency synergistic discharge in a cylindrical ICP can produce a high‐density, low‐potential, low‐effective‐electron‐temperature, and uniform plasma.     

Laser-induced etching of polycrystalline Al2O3TiC in KOH aqueous solution

Laser-induced etching of polycrystalline Al₂O₃TiC material by a tightly-focused cw Ar ion laser has been investigated in a KOH solution with different concentrations. It is found that the KOH concentration can strongly affect the etching quality where low KOH concentration can result in rough and irregular patterns. Laser-induced etching of polycrystalline Al₂O₃TiC in a KOH solution is found to be a photothermal reaction in which a threshold laser power exists. With an appropriate set of etching parameters, well-defined grooves can be obtained with clean side walls and with an etching rate up to several hundred micrometers per second. The etching behavior is also found to depend on laser scanning direction. It is also found that the grains in the polycrystalline Al₂O₃TiC material play an important role in the etching dynamics and etching quality. This etching process is believed to be applicable to the formation of a slider surface of magnetic heads in the future.     

Influence of oxygen plasma treatment on boron carbon nitride film composition

Variations in the composition and bonds of boron carbon nitride (BCN) film caused due to an oxygen (O₂) plasma ashing process are investigated for a low dielectric constant (low-k) insulating film for next generation LSI devices. The O₂ plasma treatment is preformed for BCN samples with various C compositions. The etching rate of BCN films with an O₂ plasma decreases with increasing C composition. The reaction of O atoms is suppressed in the BCN film with a high C composition. B-N and B-C bonds with lower bond energies are easily broken by the O₂ plasma and replaced by the generation of B-O, N-O, and C-O bonds. The B-atom concentration for all samples is decreased significantly by the O₂ plasma treatment. Ion bombardment may play a more dominant role than the O-atom reaction in the etching of the BCN film. The existence of C-N bonds with a high bonding energy may suppress etching and incorporation of O atoms.     

Characteristics of SiO2 etching by using pulse-time modulation in 60 MHz/2 MHz dual-frequency capacitive coupled plasma

60 MHz pulsed radio frequency (rf) source power and 2 MHz continuous wave rf bias power, were used for SiO₂ etching masked with an amorphous carbon layer (ACL) in an Ar/C₄F₈/O₂ gas mixture, and the effects of the frequency and duty ratio of the 60 MHz pulse rf power on the SiO₂ etch characteristics were investigated. With decreasing duty ratio of the 60 MHz pulse rf power, not only the etch rate of SiO₂ but also the etch rate of ACL was decreased, however, the etch selectivity of SiO₂ over ACL was improved with decreasing the duty ratio. On the other hand, when the pulse frequency was varied at a constant duty ratio, no significant change in the etch rate and etch selectivity of both materials could be observed. The variation of the etch characteristics was believed to be related to the change in the gas dissociation characteristics caused by the change in the average electron temperature for different pulsing conditions. The improvement in the etch selectivity with the decrease of duty ratio, therefore, was related to the decreased gas dissociation of C₄F₈ by the decrease of average electron temperature and, which resulted in a change in composition of the fluorocarbon polymer on the etched materials surface from C–C rich to CF₂ rich. With decreasing the duty ratio, not only the etch selectivity but also the improvement in the SiO₂ etch profile could be observed.     

Ferrite-Enhanced U-Shaped Internal Antenna for Large-Area Inductively Coupled Plasma System

A Ni–Zn ferrite-enhanced U-shaped internal inductive antenna (240 mm $times$ 2300 mm) operated at 2 MHz was used as a linear plasma source for an ultralarge-area plasma, and its plasma and electrical characteristics were investigated and compared with those of the antenna operated at 13.56 MHz without the ferrite. By the magnetic field enhancement, the operation of the source showed higher power transfer efficiency, lower antenna impedance, and lower RF rms voltage compared to that operated at 13.56 MHz without the ferrite. When photoresist etch uniformity was measured by etching the photoresist using a 40-mtorr $hbox{Ar/O}_{2} (7:3)$ mixture at 2 MHz by locating three U-shaped antennas in parallel, the etch uniformity less than 11% could be obtained on the substrate size of 2300 mm $times$ 2000 mm.      

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.     

Fabrication of Nanoimprint Stamp Using Interference Lithography

Interference lithography is used to fabricate a nanoimprint stamp, which is a key step for nanoimprint lithography. A layer of chromium in thickness of about 20 nm is deposited on the newly cleaned fused silica substrate by thermal evaporation, and a layer of positive resist in thickness of 150nm is spun on the chromium layer. Some patterns, including lines, holes and pillars, are observed on the photoresist film by exposing the resist to interference patterns and they are then transferred to the chromium layer by wet etching. Fused silica stamps are fabricated by reactive ion etching with CHF3/O2 as etchants using the chromium layer as etch mask. An atomic force microscope is used to analyse the pattern transfer in each step. The results show that regular hole patterns of fused silica, with average full width 143nm at half maximum （FWHM）, average hole depth of 76nm and spacing of 450nm, have been fabricated. The exposure method is fast, inexpensive and applicable for fabrication of nanoimprint stamps with large areas.     

Carbon-13 enrichment by IR laser chemistry of CHF3-Cl2

IR laser chemistry of CHF₃ is investigated in both neat form and in the presence of Cl₂ for carbon-13 enrichment. Infrared multiple-photon dissociation of CHF₃ is an order of magnitude more efficient in the scavenged system compared to the neat case. The photolysis of CHF₃/Cl₂ mixture results in two products, viz., CF₂Cl₂ and C₂F₄Cl₂ but with different enrichment factors. The parametric studies show that C₂F₄Cl₂ arises due to MPD of CF₂Cl₂ in secondary photolysis.     

Structural and electrical properties of high-k HfO2 films modified by CHF3 and C4F8/O2 plasmas

As-deposited HfO₂ films were modified by CHF₃, C₄F₈, and mixed C₄F₈/O₂ plasmas in a dual-frequency capacitively coupled plasma chamber driven by radio frequency generators of 60 MHz as the high frequency (HF) source and 2 MHz as the low frequency source (60/2 MHz). The influences of various surface plasma treatments under CHF₃, C₄F₈, and C₄F₈/O₂ were investigated in order to understand the chemical and structural changes in thin-film systems, as well as their influence on the electrical properties. Fluorine atoms were incorporated into the HfO₂ films by either CHF₃ or C₄F₈ plasma treatment; meanwhile, the C/F films were formed on the surface of the HfO₂ films. The formation of C/F layers decreased the k value of the gate stacks because of its low dielectric constant. However, the addition of O₂ gas in the discharge gases suppressed the formation of C/F layers. After thermal annealing, tetragonal HfO₂ phase was investigated in both samples treated with CHF₃ and C₄F₈ plasmas. However, the samples treated with O-rich plasmas showed monoclinic phase, which indicated that the addition of O plasmas could influence the Hf/O ratio of the HfO₂ films. The mechanism of the t-HfO₂ formation was attributed to oxygen insufficiency generated by the incorporation of F atoms. The capacitors treated with C₄F₈/O₂ plasmas displayed the highest k value, which ascribed that the C/F layers were suppressed and the tetragonal phase of HfO₂ was formed. Good electrical properties, especially on the hysteresis voltage and frequency dispersion, were obtained because the bulk traps were passivated by the incorporation of F atoms. However, the H-related traps were generated during the CHF₃ plasma treatments, which caused the performance degradation. All the treated samples showed lower leakage current density than the as-deposited HfO₂ films at negative bias due to the reduced trap-assisted tunneling by the incorporation of F to block the electrons transferring from metal electrode to the trap level.     

Atomic force microscopy investigation of surface roughness generated between SiO2 micro-pits in CHF3/Ar plasma

The present paper investigates the surface roughness generated by reactive ion etching (RIE) on the location between silicon dioxide (SiO₂) micro-pits structures. The micro-pit pattern on polymethyl methacrylate (PMMA) mask was created by an electron beam lithography tool. By using PMMA as a polymer resist mask layer for pattern transfer in RIE process, the carbon (C) content in etching process is increased, which leads to decrease of F/C ratio and causes domination of polymerization reactions. This leads to high surface roughness via self-organized nanostructure features generated on SiO₂ surface which was analyzed using atomic force microscopy (AFM) technique. The etching chemistry of CHF₃ plasma on PMMA masking layer and SiO₂ is analyzed to explain the polymerization. The surface root-mean-square (RMS) roughness below 1 nm was achieved by decreasing the RF power to 150 W and process pressure lower than 10 mTorr.     

SCF CI calculations of the K-shell ionization potential of carbon in methane and in the fluoromethanes

The vertical ionization potentials of the K-shell of carbon have been calculated in CH₄, CH₃F, CH₂F₂, CHF₃ and CF₄. The ab initio SCF CI approach has been used for the first three compounds with an attempt to rationalize the choice of the atomic orbital basis sets. The ionization potentials of CHF₃ and CF₄ have been extrapolated from the proceeding results. The effect of the CI cannot be neglected in either of these compounds, but it can in CH₄.     

A Time-Dependent Wavepacket Method for Photodissociation Dynamics of Triatomic Molecule

We report a time-dependent quantum wavepacket theory employed to interpret the photoabsorption spectrum of the N20 molecule in terms of the nuclear motion on the upper 21A＇ and 11A＂ potential energy surfaces. The N2-O bond breaks upon excitation leading to dissociation. The total angular momentum is treated correctly taking into account the vector property of the electric field of the exciting radiation.     

Effect of H2 and O2 plasma etching treatment on the surface of diamond-like carbon thin film

In this study, we investigated the surface properties of diamond-like carbon (DLC) films for biomedical applications through plasma etching treatment using oxygen (O₂) and hydrogen (H₂) gas. The synthesis and post-plasma etching treatment of DLC films were carried out by 13.56 MHz RF plasma enhanced chemical vapor deposition (PECVD) system. In order to characterize the surface of DLC films, they were etched to a thickness of approximately 100 nm and were compared with an as-deposited DLC film. We obtained the optimum condition through power variation, at which the etching rate by H₂ and O₂ was 30 and 80 nm/min, respectively. The structural and chemical properties of these thin films after the plasma etching treatment were evaluated by Raman and Fourier transform infrared (FT-IR) spectroscopy. In the case of as-deposited and H₂ plasma etching-treated DLC film, the contact angle was 86.4° and 83.7°, respectively, whereas it was reduced to 35.5° in the etching-treated DLC film in O₂ plasma. The surface roughness of plasma etching-treated DLC with H₂ or O₂ was maintained smooth at 0.1 nm. These results indicated that the surface of the etching-treated DLC film in O₂ plasma was hydrophilic as well as smooth.     

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