摘要:

Self‐development of poly(methylmethacrylate) (PMMA) resist was done by irradiating various rare‐gas ions at 50 keV in a mixed gas atmosphere of XeF2and O2to enhance the self‐development rate, and the effects of various exposure parameters, including gas pressure, mixing ratio, dose, current density, pulse repetition period for pulsed beam irradiation, and ion mass, have been investigated. It was observed that the self‐developing rate of PMMA for exposure without gas was very low at high doses of ≥1015/cm2, while the rate with the gas increased almost linearly with increasing dose. This is because the irradiated surface is carbonized and has a low sputtering rate after the high‐dose exposure, while the ion assisted chemical process also occurs on the carbonized surface, almost independent of the surface state. It was also found that the self‐developing rate depends on the current density and pulse repetition rate. This suggests that the reaction process has a decay time of a few ms.

ISSN:1071-1023    

DOI:10.1116/1.584294

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Exposure characteristics of 75‐layer ω‐tricosenoic acid Langmuir–Blodgett (LB) films on Al film deposited on a Si substrate have been investigated with 100‐kV Be++, Si++, and Au++focused ion beams. The dependence of the remaining film thickness on the ion dose has a peak because of the etching of the LB film at high ion doses. The sensitivity and contrast show the highest values for Au++exposure and are 2.1×1012cm−2and 0.91, respectively. The etch depth at nominal ion dose is negligibly small compared with the initial and the remaining film thicknesses. The LB film pattern fabricated by exposure with the focused ion beam can be used as the mask in dry etching and in phosphoric acid etchant. From the above results, it is found that the LB film can be used as a negative resist in 100‐kV Be++, Si++, and Au++focused beam lithography.

ISSN:1071-1023    

DOI:10.1116/1.584295

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Annealing behavior of structure, nature, and two‐dimensional depth distributions of secondary defects in one‐line‐scan, 70‐keV focused ion beam B‐implanted (100) Si have been investigated mainly using cross‐sectional transmission electron microscopy observations. In as‐implanted layers for doses above 3×1015/cm2, triangular amorphous regions are formed with a two‐dimensional spread on the order of a 0.2 μm, which is approximately an ion beam diameter. Secondary defects generated by annealing above 800 °C are confined within these triangular regions. By contrast, when 8×1014/cm2implanted layers are annealed at 1000 °C, two‐dimensional spreads of the grown defects vary from 0.2 to 0.6 μm in each implanted layer. However, in annealing at 800 °C, these defects remain near the projected range of boron and their lateral spread is confined to a beam diameter. Some results are discussed in comparison with two‐dimensional impurity distributions, 140‐keV P++implantation, and Monte Carlo simulations.

ISSN:1071-1023    

DOI:10.1116/1.584296

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

The characteristics of defects induced by Si and Ga focused ion beam (FIB) implantation inn‐GaAs have been investigated by means of deep‐level transient spectroscopy (DLTS),C–Vcarrier profiling, and resistance measurements. The DLTS spectra of Si and Ga FIB implanted samples annealed at temperatures up to 500 °C are apparently identical to one another and show three different electron traps with an activation energy between 0.25 and 0.6 eV. The resistance increases by more than five orders of magnitude by Si and Ga FIB implantation due to the induced defects. However, it is restored to initial values after annealing at 600 °C, except for a sample of Ga implantation with a dose higher than 1014/cm2. For annealing of induced defects, there are no intrinsic problems for FIB implantation with a dose lower than 1013/cm2.

ISSN:1071-1023    

DOI:10.1116/1.584335

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

We report the fabrication of lateralpnpbipolar transistors using focused ion beam (FIB) implants of boron and phosphorus for the collector and base, respectively. The implants of B+, P+, and P++were all at a dose of 1×1013/cm2and a beam voltage of 75 kV. These implants defined spaces between the emitter and collector regions of 0.5–1.50 μm; which, after diffusion and zero voltage depletion width effects were considered, produced effective on‐wafer device basewidths of ∼0.2 μm. For the best devices, values ofhFEnear 100 were obtained with good junction characteristics and at peak collector currents of 10 μA/μm of device width.

ISSN:1071-1023    

DOI:10.1116/1.584336

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Miniature Hall sensors with half‐micron sensing areas have been fabricated with maskless Si ion implantation into semi‐insulating GaAs. It is shown that maskless ion implantation is a very efficient and productive technique for fabrication of small Hall sensors with practical performance, in that it achieves, with minimum process steps, accurate pattern definition and variation in the in‐plane doping profile. The former is required to minimize the misalignment voltage and the latter is to realize high sensitivity and low input resistance. The maximum sensitivity obtained is 48 mV/T and is independent of the carrier concentration if the device structure is properly designed and fabricated. This agrees with the theoretical consideration that the high field effect determines the performance.

ISSN:1071-1023    

DOI:10.1116/1.584337

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Novel, simple techniques were developed to fabricate very narrow GaAs conducting wires by utilizing direct focused ion beam (FIB) implantation. We employed two methods for fabrication of the wires. The first method makes use of high‐resistivity (HR) regions formed by FIB implantation without successive annealing to define a very narrow conducting wire (HR method). In the second one, focused Si ions are line implanted intop‐type GaAs, forming ann‐type conducting wire in thep‐type region. Then, reverse‐bias is applied across thepnjunction in order to make the wire narrower by expanding the depletion layer (PN method). This structure has an advantage that the thickness of the wire can be varied by bias voltage. Magnetoconductances measured in all the fabricated wires show evidences of weak electron localization and conductance fluctuations due to a quantum interference effect. The minimum widths of the wires are evaluated to be ∼20 nm (HR method) and ∼100 nm (PN method) by fitting the theory of one‐dimensional weak localization to the experimental data. The phase coherent length of the electronic waves in the wires is also derived to be ∼120 nm at 1.3 K.

ISSN:1071-1023    

DOI:10.1116/1.584338

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Two aspects of the material property modifications of the GaAs/AlGaAs system induced by Ga focused ion beam implantation have been studied. One is the formation of a highly resistive region in ann‐type GaAs layer, and the other is the enhanced interdiffusion of GaAs/AlGaAs heterointerfaces. Both modifications enable us to change material properties with a minimum dimension of<100 nm. Quantum‐well‐wire structures were successfully fabricated by using the latter technique.

ISSN:1071-1023    

DOI:10.1116/1.584339

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Previous work has demonstrated that silicon implanted into Si3N4at doses above 1017cm−2can render the insulator conducting. This has been proposed as a means of making planar vias. Here we report on the use of a focused ion beam to make such planar vias in Si3N4, thus avoiding the need for resist or mask. Implants were carried out at a single energy, 160 keV, using Si++ions or sequentially at two energies, 80 and 160 keV, using Si+and Si++ions, respectively. Films of 0.25‐μm‐thick Si3N4over Al metal were implanted. Then the upper layer was deposited, patterned, and the structure was sintered at 425 °C for 30 min. The dose threshold for conduction was between 2×1017and 5×1017cm−2and depended on whether the 160 keV or the two‐energy implants were carried out. Interconnects formed in areas 1.6×1.6 μm had resistances as low as 0.15 Ω, while the minimum dimension implants, made with an unscanned beam in 6–12 s, had resistances of 1.5 to 5 Ω. For vias exposed with doses below threshold permanent conduction could be induced by breakdown at voltages well below those needed to break down unimplanted Si3N4. Even with the present state of technology, focused ion beam implantation appears to be a useful technique for making level‐to‐level interconnects through Si3N4in limited, critical areas of devices.

ISSN:1071-1023    

DOI:10.1116/1.584340

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

A scanning ion microscope has been applied to the examination of microcircuits. Highly localized sputtering with the ion beam can be used for cutting microsections, positioned with submicrometer accuracy, across selected features of semiconductor devices and integrated circuits. These sections can subsequently be examined with the ion beam in the same instrument. The secondary electron signal resulting from ion impact can depend on the voltage distribution over the specimen. Combination of voltage contrast imaging with sectioning gives voltage information from buried features of circuits.

ISSN:1071-1023    

DOI:10.1116/1.584341

出版商:American Vacuum Society    

年代:1988

数据来源: AIP