摘要:

Inductively coupled plasma (ICP) etching reactors are rapidly becoming the tool of choice for low gas pressure, high plasma density etching of semiconductor materials. Due to their symmetry of excitation, these devices tend to have quite uniform etch rates across the wafer. However, side to side and azimuthal variations in these rates have been observed, and have been attributed to various asymmetries in pumping, reactor structure and coil properties. In this article, a three‐dimensional computer model for an ICP etching reactor is reported whose purposes is to investigate these asymmetries. The model system is an ICP reactor powered at 13.56 MHz having flat coils of nested annuli powering Ar/N2and Cl2plasmas over a 20‐cm diam wafer. For demonstration purposes, asymmetries were built into the reactor geometry which include a wafer‐load lock bay, wafer clamps, electrical feeds to the coil, and specifics of the coil design. Comparisons are made between computed and experimentally measured ion densities and poly‐silicon etch rates in Cl2plasmas. We find that the electrical transmission line properties of the coil have a large influence on the uniformity of plasma generation and ion fluxes to the wafer. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362932

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We present a coupled model for neutral transport and charged species dynamics in high density plasma processing reactors. The model consists of conservation equations for mass, momentum, and energy within a multicomponent, multitemperature framework. The radially averaged one‐dimensional model is applied to an electron cyclotron resonance CF4discharge and results are presented for various pressures and flow rates. The pressure drop in the reactor is found to be significant compared to the pressure itself in high density, low pressure reactors which affects the plasma, and flow characteristics significantly. The nature of the viscous pressure drop in the reactor is also confirmed by two‐dimensional fluid dynamics simulations of only the gas flow. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362933

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Lattice spacing and inclination around cells were investigated precisely for both undoped high etch‐pit‐densities (EPD) liquid‐encapsulated Czochralski (LEC) GaAs crystal of the order of 104cm−2and undoped As‐ambient LEC (As‐LEC) crystal of low EPD of the order of 103cm−2. Measurement of the lattice spacing and the inclination was carried out by the triple crystal method using a 100×100 &mgr;m2size incident beam of high‐intensity synchrotron radiation. It was revealed that the lattice spacing varied by almost &Dgr;d, on the order of 10−4A˚, due to the cellular structure of the high EPD crystal. In addition, the low EPD GaAs crystal grown by the As‐LEC method showed considerably less variation in lattice spacing and inclination than the high EPD LEC GaAs crystal. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362934

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Nanometer‐sized crystalline Ge colloid particles in 9SiO2–1GeO2glasses were formed by implantation of protons at 1.5 MeV without post‐thermal annealing. Although oxygen‐deficient type point defects associated with Ge ions were primarily formed to fluences ≲1×1017cm−2, the formation of Ge fine crystalline particles was observed for fluences ≳5×1017cm−2. No formation of Ge colloids and the Ge‐related point defects were noted for implantation of 1.5 MeV He+to a fluence of 1×1018cm−2. The depth of Ge colloid formation layers was 22–26 &mgr;m from the implanted surface. This depth region agreed well with the peak region of electronic energy deposition. Ge–OH groups were formed preferentially over Si–OH groups upon implantation of protons and the decay curve upon isochronal annealing was close to that of the optical absorption at ∼3 eV, which was attributed to nanometer‐sized Ge. A red photoluminescence peaking at ∼1.9 eV was observed for all the implanted substrates. A tentative formation mechanism of Ge colloids in these glasses was proposed. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362935

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Gallium arsenide (GaAs) which was grown by metallorganic chemical vapor deposition, dopednwith silicon to 2×1015cm−3, and irradiated at room temperature with 1 MeV neutrons in the fluence range 1012cm−2to 3×1015cm−2, has been studied by deep level transient spectroscopy (DLTS) and by far infrared photoluminescence (PL) spectroscopy. We report the effect of annealing at 550 °C for 30 min, which, in irradiated GaAs, is to introduce the gallium vacancy (VGa). The DLTS signal at 780±40 meV, attributed to the EL2 deep level, has an introduction rate of about 3×10−2cm−1in the unannealed case, and 0.19±0.02 cm−1in the annealed case. The PL signal at 702 meV has been attributed to a phonon‐assisted transition of the EL2 defect, a defect which has been identified as the isolated arsenic antisite (AsGa+). The PL peak increases in intensity up to fluences of 3×1013cm−2, before decreasing at higher fluences. After annealing, its intensity increases up to fluences of 1015cm−2, before decreasing at the highest fluence studied. The similar behavior of the DLTS and PL signals with respect to irradiation and annealing confirms that they have the same origin. It also supports the AsGapoint defect model of EL2. The decrease in PL intensity at high fluences is attributed to radiationless transitions involving radiation‐induced complexes such as the U band, EL6, and EL14 observed by DLTS. After annealing, the concentration of these defects is reduced to a large extent, but weaker sharper peaks remain in the DLTS spectrum. We suggest that the U band consists of complexes involving AsGaand acceptors like VGa. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363023

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Using the exact charge density of intrinsic point defects of metal oxides (MOs), the phenomenological electron theory of chemisorption, developed by Volkenstein, is applied to acceptorlike and donorlike chemisorption on MO thin films for the whole &xgr; region (where &xgr;=D/LD,Dis the film thickness, andLDis Debye length). The experimental temperature and oxygen partial pressure dependence of the averaged electron concentration ⟨n⟩(pO2,T)∝e−EA/kTpO2−m(T)for polycrystalline ZnO films are discussed on the bases of three different models: the Schottky‐defect model, the Volkenstein model for electronic equilibrium, and the comprehensive model for complete equilibrium. It turns out that a Schottky‐defect model that uses single‐crystal‐mass action constants will not yield the experimental high temperature limit (T=1000 K:EA=1.6 eV,m=0.26). This limit is obtained using a higher averaged concentration of oxygen vacancies for polycrystalline films (due to the presence of grain boundaries). The comparison between the electronic and complete equilibrium shows that the screening of the surface charge through mobile positively charged oxygen vacancies has a tremendous reducing effect of about 30% of the surface potential in the temperature range considered. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362936

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Numerical calculations are presented on both equilibrium states and switching processes of surface‐stabilized ferroelectric liquid crystal cells. Defect mediated switching by Bloch walls and by disclination lines is studied in particular. Our examinations are based on an idealized bookshelf configuration of the molecules with fixed tilt angle of the director. Numerical solutions for the scalar fields both of the director twist angle and the electric potential have been determined in two spatial dimensions, assuming the fields to be constant along the third dimension. In the bulk we employ the full Frank–Oseen energy (i.e., no one‐constant approximation) with electric terms added represented by a uniaxial dielectric tensor and the spontaneous polarization. On the surface the director is anchored by a Rapini–Papoular potential with medium anchoring strength. The calculations were performed in high precision with a multigrid method on an adaptive grid. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362937

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Experimental and numerical results are presented on the evolution of stresses and the accompanying changes in the overall curvatures due to the patterning of silicon oxide lines on silicon wafers and subsequent thermal loading. The finite element analysis involves a generalized plane strain formulation, which is capable of predicting the wafer curvatures in directions parallel and perpendicular to the lines, for both the patterning and thermal cycling operations. The predictions compare reasonably well with systematic curvature measurements for several different geometrical combinations of the thickness, width and spacing of the patterned lines. The non‐uniform stress fields within the fine lines and the substrate are also analyzed. It is shown both experimentally and theoretically that certain geometries of patterned lines on the substrate induce dramatic shape changes and reversals of curvature in the direction perpendicular to the lines. The mechanistic origin of this effect is identified to be the Poisson effect arising from the anisotropic strain coupling in the patterned structure. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362938

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The vibrational density‐of‐states for various bonding structures ina‐Si1−xCx:H are calculated. The local modes induced by the SiHnand CHngroups are identified. The bending modes of SiHngroup have large variation between thea‐Si1−xCx:H anda‐Si:(H,C) alloys. The bending modes induced by the CHngroups are almost the same in the above two different alloys. The C‐dangling bond has the effect of shifting the Si–C vibrational mode toward lower frequency. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362982

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Stability of the Zn doping profile in InGaAs/InGaAsP modulation‐doped multiple quantum well (MD‐MQW) structures grown by low‐pressure metalorganic vapor‐phase epitaxy (MOVPE) has been investigated by secondary ion mass spectrometry and transmission electron microscope with wedge‐shaped samples. Although excellent stability of Zn profile is confirmed in an as‐grown sample with modulation doping (d=3 nm CZn=1×1018cm−3), the modulation‐doping structure diminishes after the second epitaxial regrowth of ap‐InP layer (CZn=1×1018cm−3) carried out by either liquid phase epitaxy or MOVPE, which is applicable for buried heterostructure lasers. However, the modulation‐doping profile is successfully preserved even after regrowth of thep‐InP layer for 90 min in a sample constructed of an undoped InP clad layer instead of ap‐InP clad layer superposed on the MD‐MQW layers. A Zn diffusion coefficient in the modulation‐doped region is extremely small, having a value of less than 7×10−18cm2/s. The maximum Zn concentration in the modulation‐doped region in barrier layers was found to be 2×1018cm−3for obtaining a stable modulation‐doping structure. It is proposed that the suppression of both interstitial Zn atoms and subsequently produced interstitial group III atoms, which are generated in thep‐InP clad layer via a kick‐out mechanism and diffuse into the MD‐MQW region, is important for preserving modulation‐doping structure. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363029

出版商:AIP    

年代:1996

数据来源: AIP