Ion Beam Diameter Research Articles

The Basic Physical Principles of Ion, Electron, and X-Ray Detectors and Their Application to Microanalysis

An integral and of prime importance of any microtopography and microanalysis instrument system is its electron, x-ray and ion detector(s). The resolution and sensitivity of the electron microscope (TEM, SEM, STEM) and microanalyzers (SIMS and electron probe x-ray microanalyzers) are closely related to those of the sensing and recording devices incorporated with them.Table I lists characteristic sensitivities, minimum surface area and depth analyzed by various methods. Smaller ion, electron and x-ray beam diameters than those listed, are possible with currently available electromagnetic or electrostatic columns. Therefore, improvements in sensitivity and spatial/depth resolution of microanalysis will follow that of the detectors. In most of these methods, the sample surface is subjected to a stationary, line or raster scanning photon, electron or ion beam. The resultant radiation: photons (low energy) or high energy (x-rays), electrons and ions are detected and analyzed.

A reactive ion beam etching and coating system

A reactive ion beam etching system, which can be used for reactive ion beam milling and ion beam coating, has been developed. The effective ion beam diameter is 10 cm with nonunifonnity in beam density less than ± 5%. The etching target is cooled by a semiconductor refrigerator so that the temperature of samples can be kept below 100°C under working conditions. The ion beam energy, density and incident angle can be changed continuously from 200 to 1000 eV, 0 to 1.0 mA/cm 2 and 0° to 90°, respectively. With the help of an improved Kaufman type ion source which is made of graphite and a unique ion beam current feedback system, the stability of the reactive ion beam current using CF 4 gas is up to 0.4% per hour. For ion beam coating spherically dished grids are used, current densities of Ar + up to 18 mA/cm 2 at 1000 eV are achieved at a focal distance of 23 cm. Using CF 4 gas, the etch ratio of SiO 2 to Si is 9, and some other materials such as LiNbO 3 and Bi 12GeO 20 can be etched with good results as well.

Focused Ga+ beam direct implantation for Si device fabrication

A focused ion beam (FIB) has been used for Si submicron device fabrication. p-n junctions and two terminal resistors were fabricated using a 60 keV Ga+ ion beam of diameter as small as 0.2 μm. Typical resistor dimensions were 50–160 μm in length and 0.2–0.5 μm in width. The Ga+ dose ranged from 5E13 to 5E14 Ga/cm2. I–V measurements showed the correct dependence of resistance on resistor length, width, and impurity concentration. We have studied the broadening of lines implanted in Si and SiO2 using a fixed ion beam diameter as a function of dose level. Selective etch (H3PO3 at 180 °C for Si and HF for SiO2) and SEM analysis showed an increase of 50%–75% in linewidth as the dose was increased by an order of magnitude.

Computor control of maskless ion implanter with AuSiBe LM ion source for III–V compound semiconductors

We have developed a microcomputer control system to operate a 100 kV maskless ion implanter for III-V compound semiconductors. The performances of various functions of this computer-controlled ion implanter has been tested. Ion species switching by an E × B mass filter, ion beam diameter monitoring, ion beam mark detection, and ion beam writing by controlling E × B mass separator, electrostatic deflector and sample stage, have been working well, precisely and reproducibly enough to indicate prospects for a production oriented system. Using this technology, we have demonstrated a simple opto-electronic device fabrication process, which cannot be done so easily by any other process technology.

Sputter‐depth profiling in AES: Dependence of depth resolution on electron and ion beam geometry

AbstractThe precise geometrical relationship between the ion and electron beams and the sample affects the depth resolution of sputter‐depth profiles in AES. A theory is presented which predicts this instrumental depth resolution by considering the shape of the ion‐eroded crater and the corresponding orientation of the electron beam. The variation in depth resolution is analysed for a range of conditions including (a) varying ion and electron beam diameter (b) the angular orientation of the electron and ion beam and (c) the effect of misalignment of the two beams.

Charge Collection Measurements for Energetic Ions in Silicon

Measurements of charge collection efficiency have been performed using 4He and proton beams from a Van de Graaff accelerator incident on test structures fabricated in MOS and diffused junction versions on nominal 1, 4 and 100 ohm-cm silicon. The purpose of these measurements is to determine the importance of the funnel effect in charge collection under a variety of conditions. The relevant dimensions of the three rectangular structural elements used in this study are approximately 2, 10, and 100 μm in width by 100 μm in length. The diameter of the incident ion beam was reduced by passing it through a 2.5 μm diameter pinhole aperture. Data on the 2 μm by 100μm diffused junction element on 4 and 100 ohm-cm silicon show evidence of charge funneling in the diffused junction version. No evidence for funneling was observed in 1 and 100 ohm-cm silicon MOS structures with a 1000 Å thick gate oxide, but funneling may occur in 4 ohm-cm silicon MOS structures with a 500 Å thick gate oxide, an important result for VHSIC-type devices.

走査型イオン顕微鏡によるイオンプローブの形成と二次電子像

Making use of a liquid metal gallium ion source, a scanning ion microscope (SIM) has been developed which produces ion-induced secondary electron images. The gallium ion source was very stable in operation at 30 kV and its mass spectrum and energy distributions were measured. A probe diameter of the gallium ion beam was verified to be less than 0.1 μm by SEM images of a evaporated Cr film which was line-etched in the SIM. The ion-induced secondary electron images were compared with SEM images. The former more strongly reflect surface structure of specimens.

Monitoring secondary ions during ion etching

Impurity contamination on etched surfaces and controllability of ion etching are important for the application of ion beam etching. In this paper, the feasibility of detecting and monitoring secondary ions emitted from the etched surface during ion etching are investigated. The experimental apparatus is composed of an improved mass filter of the quadrupole type together with a conventional ion beam etching system equipped with a Kaufman-type ion source. Experiments are carried out to detect secondary ions, examine impurity contamination, and monitor layer interfaces. A collimator and an energy filter are placed in front of the conventional quadrupole mass filter because of the large diameter ion beam. Consequently, redeposition of sputtered atoms on the sample surface is clearly observed, and the layer interfaces are monitored.

Intense Neutron Source Target Test Facility: A 200 kV, 200 mA dc, Deuterium Ion Accelerator

A 200 kV, 200 mA dc, deuterium ion accelerator has been constructed to evaluate high-temperature hydride materials such as scandium and erbium for use as targets in D-T neutron generators. The metal hydride film is deposited on a water-cooled, copper substrate designed to handle power densities of 40 MW/M2 while maintaining a surface temperature of ? 450°C. The goal of this program is to develop a target for a D-T neutron generator capable of producing 101 neutrons/s for use in cancer therapy. The accelerator employs a small duopigatron ion source which is capable of delivering a 200 mA deuterium ion beam that is composed of 60% atomic ions. The ion source is held at positive high voltage and a beam is formed with a single stage accel gap. An extractor electrode is biased negative about 2 kV to suppress secondary electrons and to define the point along the beam axis where the beam is space-charge neutralized by the trapped secondary electrons. The distance from the plasma expansion cup to the target is 0.6 m. Ion beam diameters at the target have been determined from measured infrared radiance profiles of the target due to beam heating. Data are presented on ion beam diameters for several operating conditions and accelerator geometries. D-D neutron output rates of 6 x 1010 neutrons/s have been measured with a 200 kV, 180 mA beam on erbium and a 180 kV, 160 mA beam on scandium.

A combined ion probe/spark source analysis system

Spark source mass spectrometry and secondary ion mass spectrometry have complementary advantages in the elemental analysis of solids. The AEI IM20 ion probe and MS702R mass spectrometer form a composite instrument incorporating both techniques; the design and different operating modes are described. A primary ion beam diameter as low as 2 μm can be obtained under favourable circumstances; the minimum detectable concentration of a typical element is derived as a function of this diameter. The mass resolution is greater than 5000 (10% valley definition) with electrical detection and 10,000 (50% density definition) with photographic detection; this resolution is much higher than that obtained with other secondary ion mass spectrometers. Two typical applications illustrate that such high mass resolution is a necessary prerequisite to quantitative interpretation in secondary ion mass spectrometry: precise isotopic analysis of titanium is demonstrated and the concentrations of impurity transition elements derived from ion probe and spark source analyses of a geological olivine are compared.