摘要:

A focused ion beam (FIB) system, fully computer controlled and containing a mounting stage with a laser interferometer, is used to investigate the accuracy of resist exposure fabrication and the mark detection. Fabricated patterns in poly(methylmethacrylate) (PMMA) and chloromethylated polystyrene (CMS) resists on both Si and SiO2substrates showed good pattern width accuracy. This appears to be because of the absence of the proximity effect in ion beam exposure and the stability of both the Au–Si–Be liquid metal ion source and the FIB system itself. The authors examine the use of Si, Be, and Au FIB’s for the detection of alignment marks covered with PMMA and CMS resists. Detection of marks covered with PMMA resist was possible because of the resist sputter etching produced by the FIB irradiation. For marks covered with CMS resist, the addition of a differential amplifier enabled successful detection here as well.

ISSN:0734-211X    

DOI:10.1116/1.584297

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

The surface electric field distribution along the axis of a wetted needle type liquid metal ion source has been determined by numerical methods and is shown to exhibit a secondary maximum at the intersection of the cylindrical and conical sections. It is shown that the volume flow rate of the liquid metal film along the cylindrical portion of the emitter is adequate to resupply the ionized portion at the needle apex. However, a pressure minimum in the liquid film, which decreases with increasing apex cone angle, occurs at the cone/cylinder intersection and the pressure gradient formed on the conical section of the emitter opposes flow to the apex region. It is shown that, by chemically roughening the conical section of the emitter, liquid film flow via microcapillary action occurs in such a way as to provide a low flow impedance to the apex.

ISSN:0734-211X    

DOI:10.1116/1.584298

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Modifications to a standard Freeman ion source were made which increased11B+scanned wafer current by a minimum factor of 1.4, and11B2+,31P2+, and75As2+scanned wafer currents by a factor of 4.2. Order of magnitude increases in31P3+and75As3+scanned wafer currents were also measured in the extracted ion beam. Ion source feed materials were BF3gas and elemental phosphorus and arsenic. Filament lifetime using BF3gas has been observed to be in excess of 50 mA h. The apparent increased ionization efficiency was verified by a measured increase in electron density and temperature. In addition, at high extraction current densities (∼30 mA cm−2), the modifications resulted in a symmetric extracted ion beam and uniform filament erosion characteristics. Thus, it was concluded that the plasma uniformity has increased.

ISSN:0734-211X    

DOI:10.1116/1.584299

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

The use of reactive ion etching (RIE ) with fluorinated gas plasmas, such as SF6, CF4, CBrF3, and CHF3mixed with oxygen, to achieve selective patterning of tungsten films is reported. The etch rates of W, Si, and SiO2were measured as a function of oxygen percentage in fluorinated gas plasmas under various conditions. Experiments on selectivity indicate that a CHF3/70%O2mixture under 20 sccm, 200 W, 20 mTorr etching conditions results in W:Si and W:SiO2etch rate ratios of 1.6:1 and 1.8:1, respectively. Optimized W:Si and W:SiO2selectivity ratios 4:1 and 4.8:1 have been obtained at 60 mTorr/150 W and 260 mTorr/200 W plasma conditions. For reverse selectivity, the optimum W:SiO2etch rate ratio measured is 1:4.6 in pure CHF3gas. The optimum W:Si reverse selectivity of 1:11.6 is obtained with an SF6/5%O2mixture plasma. A vertical‐to‐lateral etch ratio of 4:1 was measured with CHF3/70%O2, 200 W, 10 mTorr, 20 sccm. The etching mechanisms of tungsten due to chemical and physical processes in various fluorocarbon gases under the RIE mode have been investigated and the role of etching species such as fluorine, bromine, and oxygen is discussed.

ISSN:0734-211X    

DOI:10.1116/1.584300

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

A major problem is encountered in characterizing the surfaces at the bottom of submicrometer holes formed by plasma etching operations in the fabrication of submicrometer circuitry. Using monochromated x rays to excite photoemission spectra, surface charge buildup can occur on insulating surfaces causing the spectra to shift relative to the spectra of electrically conductive surfaces. In the case of silicon dioxide on Si, the oxide surface can charge up to a significant voltage relative to the silicon substrate making the two regions spectroscopically resolvable. When an electron flood gun is used in conjunction with monochromatic x rays, the insulated regions can be made to shift in kinetic energy relative to the substrate thereby allowing precise identification of various electrically different regions. In this initial study, residues at the bottoms of 0.75‐μm‐wide paths etched in 0.9‐μm‐thick silicon dioxide were identified. Patterns were etched in silicon dioxide using Freon‐based plasma etching and various final cleaning procedures. The residue layers observed are similar to those observed on CHF3etched silicon.

ISSN:0734-211X    

DOI:10.1116/1.584301

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

GaAs surface cleaning prior to molecular‐beam epitaxy (MBE) using a new hydrogen radical beam produced by an electron cyclotron resonance plasma in an ultrahigh‐vacuum system is investigated. Residual oxygen and carbon on the GaAs surface after cleaning are monitoredinsituwith Auger electron spectroscopy. Oxygen and carbon, which are hard to remove by conventional thermal cleaning, can be removed by hydrogen radical (H*) beam irradiation at a substrate temperature of<400 °C. It is verified that the plasma‐dissociated radicals are much more reactive in the gas phase–solid phase surface chemical interaction than the nondischarged molecules. Ga and As stoichiometry is kept after H* beam cleaning. Good crystallinity is obtained according to reflection high‐energy elecron diffraction. By carrier concentration measurement at the interface between the cleaned surface and theinsituMBE‐regrown layer, it is found that H* beam cleaning reduces the interface state concentration. This cleaning technique makes clean GaAs surfaces available for MBE pretreatment.

ISSN:0734-211X    

DOI:10.1116/1.584302

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

We studied the influence of process parameters on the composition and the electrical properties of thin SiO2films nitrided in a plasma reactor of a novel design. The process parameters investigated include pressure, temperature, reactant gas species and flow rate, plasma frequency and power, and process duration. The structure and morphology of these films were examined by cross‐sectional transmission electron microscopy. Their composition was analyzed using Auger electron spectroscopy, secondary ion mass spectroscopy, and etch rate measurements. Metal–oxide–semiconductors capacitors were fabricated and electrically characterized byC–V, time‐dependent breakdown, and charge trapping measurements. Our results show that more nitrogen is incorporated in films treated in a NH3plasma than in a N2plasma. Yet, the latter films present better electrical properties. Compositional variations between different films are not sufficient by themselves to explain their electrical properties. It appears that the effect of ion bombardment in the plasma plays an important role. By properly optimizing process parameters, the charge to breakdown of nitrided films can be enhanced over that of SiO2. This improvement is ascribed to a lower electron trapping rate.

ISSN:0734-211X    

DOI:10.1116/1.584303

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

We present an analysis, based on control theory, of the transients in flux from a molecular‐beam epitaxy source cell which occur after opening the shutter and also after changing the set point of the cell temperature controller. This analysis permits the calculation of the variation of this set point with time which produces a transient equal and opposite to that following shutter operation. Experimental results show that use of this set point variation results in a beam flux constant to within 1%, and that the parameters in this analysis do not change significantly over at least 100 h of cell operation. In addition we show that simple manual control of the set point based on this analysis can reduce the flux transient by a factor of 5.

ISSN:0734-211X    

DOI:10.1116/1.584304

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

The high‐energy Auger spectra were measured for a large number of molecular‐beam epitaxial (Al, Ga)As layers, and analyzed for Al composition using electron microprobe and reflection electron diffraction oscillations for calibration. A simple analysis employs this calibration and avoids assumptions of column III/V stoichiometry. Thus the bulk composition can be established to within a few percent from the Auger peak heights, in spite of a large variation in the As surface coverage. An effort is made to account for differences between Auger sensitivity factors determined for as‐grown surfaces (this study) and those obtained from measurements performed during Ar+ion sputtering. Our measurements support recent measurements of the band gap of AlxGa1−xAs which place the direct/indirect crossover composition betweenx=0.37 and 0.39.

ISSN:0734-211X    

DOI:10.1116/1.584305

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

High reflectivity of aluminum alloy layers causes degradation to occur in photoresist images through reflective light scattering. Titanium nitride used normally as a diffusion barrier under aluminum silicon contacts, can also be applied as an efficient antireflection layer on top of AlSi. Processing advantages over other antireflective layers (ARL) such as hillock suppression and enhanced electromigration resistance are also discussed. Process flow parameters from ARL deposition to wire attach are reviewed as applied to megabit dynamic random access memory development.

ISSN:0734-211X    

DOI:10.1116/1.584306

出版商:American Vacuum Society    

年代:1988

数据来源: AIP