摘要:

The mixing of GaAs/GaAlAs quantum wells by low energy gallium focused ion beam implantation and thermal annealing, was characterized by low‐temperature photoluminescence spectroscopy. The depth extension of the induced disordering as well as the lateral resolution of interdiffused lines generated by line‐and‐space scan of the ion beam, was evaluated. On a multiple quantum well structure, no significant channeling of the ions, impinging on the target normally to the surface, could be evidenced, and the mixing was found to affect only the first quantum well located near the surface. On the other hand, the width of the interdiffused region observed laterally to the implanted lines is much larger than the spot diameter of the ion beam. It is concluded that the defects which activate the Ga–Al exchange at the interfaces, diffuse more rapidly in the aluminum rich layers. The influence of a rapid thermal annealing and the aluminum content in the barriers, on the lateral selectivity of the induced disordering is discussed.

ISSN:0734-211X    

DOI:10.1116/1.585671

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The disordering and compositional change of the InGaAs/InP superlattice by the Ga ion beam was investigated, and using the effect, quantum wires were fabricated by focused Ga ion beam. The analysis of Raman scattering shows that in the implanted region intermixing, i.e., alloying takes place in such a way that the intermixed In1−xGaxAsyP1−yalloy has the compositions of alloy with the lattice constant nearly equal to that of InP, although at higher doses the compositionsxandybecome smaller due to larger interdiffusion. Focused Ga ion beam of 100 kV was irradiated in lines onto InP (350 Å)/InGaAs (50 Å)/InP (500 Å) single quantum well at doses of 1×1013–1×1014cm−2. Implanted samples were annealed at 650–670 °C for 60 min. The photoluminescence measurements at 30 K for wires with various widths show that with decreasing wire width the luminescence peak energy increases nearly following the change of the quantum levels in the potential well calculated by taking into account lateral straggling of implanted Ga ions. The implanted and alloyed regions are confirmed to act as potential barriers by which carriers are confined.

ISSN:0734-211X    

DOI:10.1116/1.585672

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

This paper deals with the formation, growth kinetics, and some electrical properties of palladium silicide formed by using the direct implantation of palladium ions into (100) and (111) Si using a focused ion beam machine. The activation energy for growth of the silicide formed has been determined by two different techniques and has been found to be significantly lower than normally reported values for thermal formation by thin‐film annealing of the same silicide. Results from an extensive microstructural study have been presented for a variety of implantation and follow‐up anneal conditions. Finally, some data for Schottky diodes made using this novel technique have been presented.

ISSN:0734-211X    

DOI:10.1116/1.585673

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Focused ion beam milling is an important tool for LSI modification and failure analysis. For both of these applications, the depth control in milling is a major requirement. The FIB machine we used was equipped with an ion impact photoemission detector for use with both Si and Al. We studied the photoemission change mechanism during LSI milling by altering the acquisition area of the photoemission, and by chemical analysis on the side walls of the milled holes. Si emission varies with the surface area of SiO2. Al emission originates in the edge lines of Al and SiO2at the bottom of the hole, and from the Al redeposited on SiO2of the side walls. On the edge lines and the side walls, ion mixing of SiO2and Al enhances the Al photoemission. We demonstrated that an almost 100% modifying yield in both Al wire cutting and contact hole milling is possible by observing the variance of both emissions.

ISSN:0734-211X    

DOI:10.1116/1.585674

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Single‐crystalline silicon films on insulator (SOI) were formed by using lateral solid‐phase epitaxy (LSPE) induced by irradiation of a focused Si ion beam (beam‐induced LSPE). When the irradiation was done with the beam scanned over a few microns width, it was found that the beam‐induced LSPE was hindered by the beam‐induced polycrystallization in SOI regions. In order to avoid the polycrystallization and to obtain long LSPE, a pseudolinear beam was used so that only the area near the amorphous/crystalline interface was irradiated without unnecessary irradiation to SOI regions. To continue the LSPE, the sweep velocity of the beam should be carefully selected to match with the enhanced LSPE rate, which depends on the dose rate. The maximum LSPE rate obtained was 30 nm/s for the dose rate of 3×1015cm−2 s−1at 500 °C and the LSPE has been extended to 20 μm from the seed.

ISSN:0734-211X    

DOI:10.1116/1.585675

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Insitupattern formation of GaAs by focused‐ion‐beam (FIB)‐assisted Cl2etching followed by overgrowth by molecular‐beam epitaxy (MBE) has been studied.InsituAuger electron spectroscopy (AES) measurements of the etched samples showed that preferential sputtering of As, which was observed on a GaAs surface processed by ion sputtering, did not take place on a GaAs surface processed by FIB‐assisted Cl2etching. The surface morphology of the overgrown AlGaAs layer on theinsitupatterned substrates were excellent. Observations of the cross‐sectional view in the etched region of an overgrowth sample showed that the interface between the etched surface and the overgrown layer was flat, and that no undulations caused by etching were observed. A 1‐μm linewidth with a 2‐μm pitch line‐and‐space pattern of GaAs covered with an AlGaAs layer was obtained by a combination of FIB‐assisted Cl2etching and subsequent MBE overgrowth.

ISSN:0734-211X    

DOI:10.1116/1.585676

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Ion current densities in focused‐ion‐beam (FIB) implantations are several orders of magnitude greater than those of conventional broad‐beam implantations. The corresponding increase in dose rate during implantation is shown to affect parameters of interest in device fabrication. FIB and broad‐beam Si implants into GaAs at energies from 70 to 280 keV and at doses from 3×1012to 1014cm−2are characterized using secondary ion mass spectroscopy (SIMS) and Hall‐effect measurements. Reduced straggle, decreased activation, and modified carrier profiles are observed for FIB implants, particularly at higher energies and doses. These effects are attributed to dose‐rate‐dependent lattice damage.

ISSN:0734-211X    

DOI:10.1116/1.585677

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The clocking frequency of long channel CCDs is limited by the time taken to transfer charge from one well to the next. The bulk of the charge transfers rapidly by Coulomb repulsion but residual charge has to transfer by thermal diffusion, which is a slow process. If then‐type dopant density has a gradient in the direction of current flow, a built‐in electric field is created, speeding up the charge transfer process. The focused ion beam system is uniquely suited to implant such a gradient of doping and has been used to implant buried‐channel CCDs with 26‐μm‐long storage gates. The devices built to demonstrate this concept were shallow‐buried‐channel CCDs driven by 2‐phase 5‐V clocks. Arsenic ions were implanted at an energy of 220 keV and a gradient of doping increasing from 0 to 1.5×1011ions/cm2was superimposed on a uniform phosphorus implant. The challenge here was to get alow, monotonically increasing implant dose. Defocusing of the 25‐pA As+ +beam to a diameter of ∼1 μm was found to be necessary. The maximum operating (clocking) frequency of the graded‐implant devices was 41 MHz compared to a maximum frequency of 2.5 MHz for the same devices with uniformly doped channels. Such long‐channel CCDs are of interest in 2‐dimensional imaging applications and signal processing applications where high well charge capacity is needed without compromising speed or charge transfer efficiency.

ISSN:0734-211X    

DOI:10.1116/1.585678

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Diodes have been fabricated by on‐axis Ga+focused ion beam (FIB) implantation at 4–25 keV inton‐Si 〈100〉 wafers doped to 2×1015/cm3. Post‐implantation anneal was performed at 600 °C for 30 s to electrically activate the Ga and to regrow the implanted layer. SIMS measurements performed to obtain the Ga concentration depth profile indicate good agreement withtrimsimulation even at low energies. At 4 keV an electrical junction depth of 15 nm is obtained from spreading resistance profiling (SRP). The junction depth was found to vary linearly with energy over the range explored. The electrical properties of the diodes were obtained fromI‐Vcharacteristics. The leakage current density of the 5 keV diode was measured to be 1 and 20 nA/cm2at a reverse bias of 1 and 5 V, respectively. The corresponding leakage current density values for the 10 and 15 keV diodes were between 25% and 50% lower than those reported for 5 keV. The reverse bias breakdown voltage was between 105 and 110 V for all diodes. The combination of nanometer‐scale junction depth, low leakage current density, and high breakdown voltage indicate that low energy Ga FIB implantation is a promising technology for ultrashallowp+‐njunction fabrication.

ISSN:0734-211X    

DOI:10.1116/1.585679

出版商:American Vacuum Society    

年代:1991

数据来源: AIP