摘要:

Process monitoring of borophosphosilicate glass (BPSG) dielectric thin films used in the manufacture of microelectronic devices is currently performed using multivariate calibration models developed from transmission infrared (IR) spectra of the films deposited on undoped monitor Si wafers. It would more be desirable to monitor the BPSG deposition on the actual product or device wafers. Because product wafers are opaque in the IR, reflection rather than transmission spectroscopy must be used to monitor the BPSG films deposited on product wafers. In this article, we demonstrate, for the first time, that IR reflection spectra of product wafers can be used to monitor the boron and phosphorus contents of the film and the film thickness to a precision that is comparable to that found for IR analysis of BPSG deposited on monitor wafers. The cross-validated standard errors of prediction of 0.11 wt %, 0.11 wt %, and 3 nm for B, P, and thickness, respectively, were achieved using multivariate partial least squares (PLS) models applied to the IR reflectance spectra obtained from reference product wafers. The prediction abilities were found to be independent of the position of the infrared spectrum on a given device and independent of which devices of the same structure were examined. The multivariate calibration models could be used to predict the B and P contents and film thickness of BPSG on device structures of different types and even for devices of different feature sizes if the PLS models were adjusted for slope and intercept differences. Therefore, the time and expense of generating calibrations for new device structures can be greatly reduced by the use of a small number of reference samples of the new devices to estimate the required slope and intercept adjustments for the models.

ISSN:0734-2101    

DOI:10.1116/1.581508

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The geometric conductance defined in a normal tube is not useful for describing transmission characteristics of a sticky tube with wall pumping in which the gas throughput is not uniform. To find a proper solution to this problem the concept of transmission conductance is introduced instead of the geometric one. The transmission conductance is expressed as a function of the pressures and the throughputs at the inlet and outlet of the sticky tube. Applying the concept of the transmission conductance to the tubes with wall sorption and/or wall outgassing, then a few selected mathematical expressions of the transmission conductance and adsorption speed are derived. A combination rule of the transmission conductance for constructing a composite tube, equivalent to the Oatley’s principle for normal tubes, is also discussed. Comparison of analytic calculations and Monte Carlo simulations shows good correspondence as long as the sticking coefficient on the tube wall is not much larger than 0.1.

ISSN:0734-2101    

DOI:10.1116/1.581509

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Previous profile evolution studies of plasma-assisted etch processes have shown that ions scattered from sidewalls can lead to microtrench formation on the bottom of an etched feature [see, for example, Dalton et al., J. Electrochem. Soc.140, 2395 (1993)]. In these studies, the ions impacting feature surfaces with incident angles above a critical value were assumed to reflect specularly from the surfaces. In the present article, we describe the energy and angle distributions of reflected atoms obtained from molecular dynamics (MD) simulations. We simulatedAr+andCl+ions impacting model silicon surfaces. The ion incident energiesEiwere 20, 50, and 100 eV. We varied the ion incident anglesθifrom 0° to 85° from the surface normal. The model silicon surfaces had chlorine coverages of 0 monolayers (ML) of Cl, 1 ML Cl, and 2.3 ML Cl. We determined the Ar and Cl reflection probabilities, i.e., the fraction of Ar and Cl atoms scattered from the surfaces during the 1–2 ps MD trajectories. Forθi⩾75°,we found that the reflection probabilities were greater than 90% in most cases. For these large incident angles, we describe the distributions of energiesErand angles (polarθrand azimuthalφr)for the Ar and Cl atoms reflected from the surfaces. The results of the MD simulations are compared with the assumption of specular scattering. In addition, we compare the average energies of the reflected atoms with the predictions of two simple models based on the binary collision approximation. We discuss the effects of incident ion species,Ei,θi,chlorine surface coverage, and surface roughness on these results.

ISSN:0734-2101    

DOI:10.1116/1.580993

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Nickel sulfide catalysts obtained by homogeneous precipitation were prepared by varying the homogenization time and the sulfiding temperature. Structural characterization studies by transmission electron microscopy and x-ray diffraction showed the formation of various metastable crystalline phases at low temperatures of sulfiding(Ni3S2,Ni3S4,Ni7S6,Ni9S8,NiS2,NiS1.03, NiS),depending on the preparation conditions. NiS millerite appears to be the main phase for samples obtained after 4 h homogenization, changing toNiS1.03phase after 36 h. Catalytic tests of these samples for cyclohexanone hydrogenation showed that the intrinsic activity is higher for theNiS1.03phase.

ISSN:0734-2101    

DOI:10.1116/1.581510

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The interaction of gas-phase atomic oxygen with chemisorbed deuterium on Ru(001) has been investigated by means of temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS). Exposure of gas-phase atomic oxygen to thep(1×1)deuterium overlayer at a surface temperature of 80 K results primarily in the adsorption of oxygen atoms. Thermal desorption spectra measured after large atomic oxygen exposures show the desorption ofD2Obetween 150 and 190 K as well as a large decrease in the activation energy for the recombinative desorption of deuterium. HREEL spectra demonstrate the presence ofD2Ofollowing atomic oxygen exposure at 80 K and, together with TPD spectra, suggest the presence of chemisorbed OD. Since OD andD2Oare formed at low surface temperatures, an Eley-Rideal-like mechanism is suggested in which oxygen atoms from the gas phase react with deuterium adatoms prior to being thermally accommodated to the surface.

ISSN:0734-2101    

DOI:10.1116/1.580994

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

We report on a structural investigation of the zirconium-based ternary alloy getter “St 707” (from SAES Getters, Milan, Italy) based onin situx-ray diffraction (XRD) measurements at high temperature in inert gas atmosphere accompanied by scanning electron microscopy with energy dispersive x-ray analysis (SEM-EDX) and thermal analysis by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) investigations. The XRD together with SEM-EDX confirms that the getter is biphasic before as well as after activation. Hexagonal Zr and the cubic Laves phaseZr(V1−xFex)2with a narrow compositional range (0.16⩽×⩽0.18) coexist in this material. Upon heating, thein situXRD shows a gradual decrease in the crystallinity of the Laves phase, which is attributed to its disintegration into small particles. DSC measurements under moist Ar exhibit an exothermic irreversible transition at≈675 K which is associated with chemical bulk reactions and indicative of the gettering process. The operation of the gettering process during activation was verified by TGA measurements. It is concluded that the gettering process is correlated with the disintegration of the Laves phase. The sorption kinetics of water vapor were studied at 355 K over a pressure range of101–102Pa using a barometric technique. A change in the rate determining step is detected from an initial diffusion-controlled step to surface adsorption after some sorption cycles.

ISSN:0734-2101    

DOI:10.1116/1.580995

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

In the molecular-beam epitaxy (MBE) process precise control over thickness, composition, and doping profiles are critical for end device performance. This article addresses the problem of accurately modeling and controlling the flux sources (effusion cells) used in MBE. A first-principles nonlinear dynamic model of an effusion cell is derived, investigated, tuned, and used for designing advanced closed-loop feedback schemes. The model is a coupled set of driven nonlinear ordinary differential equations. It provides the transient and steady-state time-dependent response of the cell to a given (heater power) input. Further, it provides output predictions of the produced molecular flux and the temperature read by a thermocouple built into all modern effusion cells. We show how to tune parameters in the model from actual experimental data using a nonlinear least squares identification algorithm. Simulations show excellent agreement with experimental data and empirical experience including reproduction of the well-known shutter transient event when the thermocouple temperature is regulated with a proportional-integral-derivative (PID) controller. The model further can be used to explore interesting effects. For example, the magnitude and duration of a shutter transient under PID regulation is different for gallium versus indium charged cells. This leads to a thin indium rich initial layer in the growth of InGaAs. The tuned model is used to investigate the efficacy of nested PID control designs and, finally, is used in an advanced feedback controller we design using differential geometric design methods of nonlinear control theory. Simulations show our advanced nonlinear controller eliminates flux transients over a wide range of operating conditions without the need for any recalibration or adjustment and provides superior tracking. The latter feature of superior tracking will become increasingly important as future devices call for new growth regimes and methods such as layers with continuously graded composition.

ISSN:0734-2101    

DOI:10.1116/1.580996

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Excellent antiwear diamond-like carbon (DLC) films were prepared on silicon wafers by a novel negative carbon ion beam deposition system. This system does not need any gas in the chamber; deposition occurs under high vacuum. The ion source has good control of theC−beam energy (from 50 to 150 eV) and produces a 0.5-in.-diam ion beam for DLC coating. All coatings showed ultrasmooth surfaces(Ra∼1 nm)and good adhesion. The results of infrared and Raman spectroscopy show that the degree of diamond-like character in the films, thesp3fraction, increases as a function of deposition energy in this particular energy range. The nanoindentation hardness of the films also increases from 15 to 50 GPa as deposition energy increases. The wear rates and friction coefficients against a M-50 steel bearing ball were measured in a pin-on-disk tribometer with a normal load of 9.8 N, calculated nominal Hertzian stress of 0.8–1.8 GPa. The measured wear rates of the DLC films were of the order of10−7and10−8 mm3/N mdepending on the deposition energy of the carbon beam. The friction coefficients in the steady state were found to be around 0.1. These results indicate excellent applications for abrasion resistant DLC coatings. We are developing a rectilinear negative carbon ion beam deposition system (up to 8 in.) for large area application, and many of the process scale-up issues have been solved.

ISSN:0734-2101    

DOI:10.1116/1.580997

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Thermal mass flow controllers are widely used in the semiconductor industry to deliver accurate process gas compositions and concentrations to the processing chamber. The sensor, a stainless-steel capillary tube, is the most critical part of the mass flow controller. We have designed a new sensor using thin-film technology in order to improve its reliability and to decrease its response time. The two temperature sensors are deposited platinum on an electrical insulating layer directly upon the capillary tube (without exposure to the gas stream) whereas the sensor is constantly heated by a resistive wire. The so-obtained sensors are very promising and the new design and technology could give us improvements which the old design and technology (two resistive coils) would not have been able to give us. The physical mechanisms of this new sensor are described by a third-order steady-state analytical thermal model which gives good results when compared with experiments. This fundamental study also includes the evolution of the correction factors as a function of the flow. We present here the thermal model, the new structure of the sensor, and its advantages.

ISSN:0734-2101    

DOI:10.1116/1.580998

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Thin films of hafnium oxide have been prepared by using a dual ion beam sputtering system. A study of their physical properties is reported. In particular, structural and compositional characterization was performed by means of x-ray diffraction and x-ray photoelectron spectroscopy techniques, showing a mixture of amorphous and polycrystalline structure and a substoichiometric composition. The atomic force microscopy results have shown a crater-like morphology probably due to the deposition process. In addition the gas sensing characteristics were analyzed in the presence of carbon monoxide. The variations in the electrical resistance have shown the capability of the films to detect CO and then the possibility to use hafnium oxides as a new sensitive material in the field of gas sensors.

ISSN:0734-2101    

DOI:10.1116/1.580999

出版商:American Vacuum Society    

年代:1998

数据来源: AIP