摘要:

Spinodal decomposition of ternary semiconductor alloys during lattice-matched heteroepitaxy is considered here. It has been previously demonstrated that a perfectly flat surface (with no step) would forbid alloy demixing. The case of a rough surface is the purpose of this article. How the possibility of a better strain relaxation introduced by the surface roughness can favor alloy demixing is analyzed first. The present results are exemplified by the AlInAs lattice matched to the InP case. Second, a step-by-step model is proposed to simulate the growth process on a rough surface. This model leads to a description of the strain and alloy demixing during this growth. This study clearly shows how and why the atoms corresponding to binary materials with lower surface tension naturally tend to segregate towards bumped areas.

ISSN:1071-1023    

DOI:10.1116/1.590185

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The electronic states for normally stacked and faultily stacked layers on the GaAs{111}A, Bsurfaces are calculated by use of the discrete variationalXα cluster method and the plane wave nonlocal pseudopotential method. The results show that chemical bondings between atoms are not as ionic in the faultily stacked layer of (111)Bas they are in the (111)Acase, and that on the (111)Asurface more attractive Coulomb interaction energy is gained in the faulty stacking layer than in the normal stacking one. These results explain well the more frequent emergence of in-plane faults in the (111)Asurface, which is well known in GaAs{111}A, Bgrowth experiments. The total energy calculations also provide quantitative interpretation of such growth features.

ISSN:1071-1023    

DOI:10.1116/1.590186

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

An approach for nanofabrication using de Broglie wave has been developed. Line and dot patterns with 100-nm periodicity were delineated on a PMMA resist by electron-beam holography with a thermal field-emitter gun and an electron biprism. This technique allows us to produce nanoscale periodic patterns simultaneously. Furthermore, the possibility of nanostructure fabrication by atomic-beam holography has been demonstrated by using a laser-trap technique and a computer-generated hologram made by electron-beam lithography.

ISSN:1071-1023    

DOI:10.1116/1.590187

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

For more than a decade, technical arguments have been used to predict the demise of optical lithography. Recently economic arguments are being used, dramatically increasing the likelihood of the predictions coming true. Presently four technologies are competing to replace optical lithography. This article will describe the current state-of-the-art in ion projection lithography, and contrast its advantages and disadvantages with respect to the other nonoptical technologies. An argument will be made that ion projection lithography, uniquely, offers the possibility of reducing the dramatically escalating costs of lithography, resulting in overall lower integrated circuit production costs. This potential for reduced production costs is the prime motivator to consider ion projection lithography as a production lithography candidate.

ISSN:1071-1023    

DOI:10.1116/1.590188

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Focused ion beams (FIBs) have been previously used as tools for such diverse tasks as high-resolution lithography, where their sub-10 nm spot sizes enable the patterning of diverse nanostructures, and surface compositional analysis, where their ability to sputter material in a localized area allows discrete components of a device or circuit to be characterized. Recently, the authors have capitalized on the FIB’s versatility by using it for microelectromechanical sensor fabrication as well as post-processing device characterization. The HRL FIB nanoprobe system has been used in the fabrication of high-performance surface-micromachined accelerometers operating on the principle of tunneling between a cantilevered beam and a sub-0.1-μm-diam tip lying beneath it on a Si substrate. The 8-nm-diam FIB has been used to pattern small dots in a bilevel negative-positive resist layer which are then transferred into a Au layer to form pyramid-shaped tunneling tip structures whose narrow dimensions are essential to high device performance and stability. High-purity, contamination-free Au on both the tunneling tip and cantilever underside is also critical to high-sensitivity tunneling devices. Because the undersides of the beams cannot be viewed with a scanning electron microscopy, even at high mechanical tilt angles, the cantilevers must be physically peeled back in order to expose their bottom surfaces and analyze them for cleanliness. Depending on the material used for fabricating the cantilevers, the rigidity of the structures can render them difficult to bend. We have used a commercial FIB milling system to cut through a portion of the cantilever width, thus creating a hinge, which facilitates the subsequent peeling back of the structure. Comparison of Auger spectroscopy data on peeled-back beams with and without a FIB-milled hinge shows similar surface contamination levels, indicating that redeposited material due to ion milling is localized enough to not affect the compositional analysis of the tunneling region.

ISSN:1071-1023    

DOI:10.1116/1.590189

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Protrusions of 1 nm dimensions have been grown on single-crystal tips of tungsten and iridium of about 100 nm size. With positive bias the tip can be operated as an intense ion source and with reversed bias intense electron beams can be obtained. In both cases, specific brightness values of up to1 TA/cm2 srd eVhave been recorded under optimized conditions. As for gases, tungsten can be used only for less reactive species, such as hydrogen and rare gases, whereas iridium is also useful for aggressive gasses, such as oxygen. Both metals are excellent electron emitters. Thus, a powerful multipurpose source is realized with supertips of tungsten and iridium, as will be demonstrated by a variety of experimental results on their relevant properties.

ISSN:1071-1023    

DOI:10.1116/1.590190

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

We discussed a two lens optical system focused ion beam (FIB) employing a Ga-emitter (LMIS), whose acceleration voltageVaccis ranged 30–100 kV, which will be used for milling and secondary ion microscope observation purposes. On such an optical system, we investigated the relation between minimum obtainable beam diameter and chromatic aberration coefficient againstVacc,and studied the possibility of improving FIB resolution by increasing theVacc.The beam diameter is mainly determined by the size of a Gaussian image and the chromatic aberration, especially that of objective lens, if the beam current is very low. From this fact, we showed that the magnification optimization method which is one of the optical optimization methods can be greatly simplified at a lower beam current region. Using this simplified method, we summarized a guide line for evaluating anVaccvalue from the standpoint of realizing a finer beam. Also given is information useful for designing a FIB column in consideration of optimized optical column design for realizing the optimized magnification. Finally, calculating the attainable minimum beam diameter and optimum column length againstVaccvalues, we discussed the limitation of beam diameter by increasing theVacc.

ISSN:1071-1023    

DOI:10.1116/1.590191

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Direct write implants are usually made in registration with pre-existing features on the wafer surface. The accuracy of the registration is a critical component of the error budget for a given device, just as it is for optical lithography layers. We present a scheme for creating alignment marks in field oxide on a silicon wafer. These alignment marks can be applied near the beginning of the process, are robust in a silicon processing environment, and can be reused for multiple layers of maskless implantation. We also present our method of measuring overlay accuracy, and data showing that an accuracy of 62 nm one sigma can be achieved by our system.

ISSN:1071-1023    

DOI:10.1116/1.590192

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

We constructed an ion and electron dual focused beam apparatus to develop a novel three-dimensional (3D) microanalysis technique. In this method, a Ga focused ion beam (Ga FIB) is used as a tool for successive cross sectioning of the sample in the “shave-off” mode, while an electron beam (EB) is used as a primary probe for Auger mapping of the cross sections. Application of postionization with EB to Ga-FIB secondary ion mass and two-dimensional (2D) elemental mapping with Ga-FIB-induced Auger electrons are also in the scope of the apparatus. The 3D microanalysis was applied to a bonding wire on an integrated circuit (IC). A series of EB-induced sample current images of the successive cross sections were obtained as a function of the cross-sectioning position. This result showed the capability to realize the 3D Auger microanalysis. Two-dimensional elemental mapping with Ga-FIB-induced Auger electrons was realized for the first time on the IC surface. Its applicability to surface analysis was evaluated.

ISSN:1071-1023    

DOI:10.1116/1.590193

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

A focused ion beam (FIB) system was remodeled specially to realize single ion implantation (SII) by which we intended to implant an accurate number of ions one by one into ultrafine semiconductor regions. In the SII, single ions are extracted by chopping the ion beam, and one-by-one extraction of ions have become possible by installing an ultrahigh speed amplifier for chopping. In order to achieve accurate detection of each single ion incidence in the SII, detection of SEs emitted upon ion incidence with a high sensitivity and a high signal to noise (S/N) ratio is essential. Signals from the SE detector which synchronize to an instance of chopping are selectively counted to achieve high S/N ratio. Contaminant particles originating from neutralization and scattering of the ion beam are eliminated by sliding the ion source off the beam axis and cutting off the ion beam at the entrance of the FIB’s mass separator.

ISSN:1071-1023    

DOI:10.1116/1.590194

出版商:American Vacuum Society    

年代:1998

数据来源: AIP