Ichiro Kanomata

Microwave ion source for high-current implanter.

A long-life, high-current, microwave ion source for an electromagnetic mass separator is described. Ionization takes place due to the 2.45-GHz microwave discharge at a magnetic field intensity which is higher than the electron cyclotron resonance magnetic field. The discharge chamber is a ridged circular waveguide. The discharge region is restricted to a rectangular volume between the ridged electrodes by filling the remaining portions with dielectric. This source operates under low pressure (10(-2)-10(-3) Torr) and with high power efficiency. The incident microwave power is only several hundred watts at maximum output. When PH(3) gas is introduced, the total extracted current is about 40 mA with a 2x40-mm extraction slit. A P(+) ion implantation current of more than 10 mA is obtained by combining the source with a 40-cm radius, 60 degrees deflection magnetic mass separator.

Collision-induced dissociation of water cluster ions at high pressure

Abstract Water cluster ions are reduced to H3O+ by collision-induced dissociation at ca 1 torr. The cluster ion abundance changes drastically with the electric field strength in the collision region. Collision-induced dissociation takes place through a multiple collision process. The critical field strength for the dissociation is closely related to cluster ion dissociation energy.

High‐current ion implanter using a microwave ion source

A new ion implanter has been designed for high‐dose predeposition in a semiconductor production line. It incorporates a microwave ion source, a 90° magnetic mass separator, and a rotating disk target chamber. Mass peak variations of PH3 gas are shown as a function of the incident microwave power. The ion energy level can be varied from 10 to 50 keV. It makes 10 mA P+ implantation (maximum 15 mA) possible. After beam adjustment, implantation is automatically carried out with a microcomputer. The operation rate of the implanter is remarkably improved due to the long lifetime of the modified microwave ion source and the low gas consumption. The dose nonuniformity of a 3‐in. wafer implanted with this implanter has a standard deviation (σ) of 0.5%. This small nonuniformity results in a small σ in the transistor current gain (less than 3.5%).

A stigmatic, second-order, double-focusing mass spectrometer

Abstract A double-focusing mass spectrometer of second order was constructed and the focusing property was examined. The ion optical system was determined by computer calculations in order to correct all second-order image aberrations. In the calculations the influences of the fringing field were taken into account. This ion optical system has velocity focusing, radial focusing and axial focusing properties. The instrument is composed of an electric toroidal sector ( r e = 212 mm, φ e = 85.2°, c = 0.5, ρ′ = −106 mm), and a uniform magnetic sector of non-zero entrance and exit angles ( r m = 200 mm, φ m = 90°, ϵ′ = 30°, ϵ″ = −10°). In experimental results, a maximum resolving power of 83 000 at 10% valley separation, and a total transmission of 43% were obtained. Axial focusing action and correction of the crescent shape resulting from second-order aberrations were observed from the shape of spectral lines taken on photographic plates.

Mass spectrometric study of ions produced in oxygen at atmospheric pressure by a collisional dissociation method

Abstract Ions such as O4+, O5+, O6+, O2+H2O, H3O+OH · O2, H3O+H2O · OH, H3O+H2O · OH · O2, and H+(H2O)n, (n = 1, 2, ... ) are produced by ion —molecule reactions initiated by a corona discharge at atmospheric pressure in moist oxygen. The ions are identified by a collisional dissociation technique at ca. 1 torr. Dissociation energies of clusters are compared with critical drift voltages for cluster dissociation and cluster energy levels are estimated. In addition to dissociation reactions, endothermic reactions such as H3O+ + O2 → O2H+ + H2O or O2+ + H + H2O are observed through this collisional excitation technique. The presence of an endothermic switching reaction, H3O+OH + O2 → O2+H2O + H2O, in the drift region is also suggested.

A triple focusing mass separator

Abstract A new type of a mass separator having a large transmission rate was constructed. It is composed of a Wien filter with a magnetic entrance angle ( L w = 36 cm, α 1 = 28°, G m = 6 cm, G e = 3 cm) and an electric spherical sector ( ϕ e = 30°, r e = 18 cm, G s = 6 cm). This separator has radial, axial and velocity focusing, i.e. simultaneous triple focusing properties. An optinum resolution of 120 and transmission rate of 68% are obtained at the ion source and collector slit widths of S i = 3 mm, S c = 1 mm.

Analyses of silicon wafers by a high-resolution secondary ion mass spectrometer

Abstract A high-resolution secondary ion mass spectrometer (SIMS) was constructed for solid surface analyses. The instrument is composed of a Hitachi IMA-2 ion probe and a stigmatic, second-order, double focusing mass spectrometer. Commercially available silicon wafers (p-type, 20 Ω cm) were analyzed as test samples. The highest mass resolving power was 11,000 (10% valley). The analytical sensitivity of this SIMS permits detection of boron to silicon at an ion ratio of 10 −7 . The inorganic and hydrocarbon element ions were accurately resolved.

In-Depth Analysis in Selected Area with Ion Microprobe Analyzer

In-Depth analysis is one of the most important application fields of ion microprobe analyzer. Various attempts have been already made and some of them have been used in practical applications. Conventional in-depth analysis includes the following problems. 1) In-depth analysis of a selected microscopic area. 2) In-depth analysis of thin surface layers. In this paper, the new technique to solve these problems are discussed. With reference to item 1), scan-stop method is developed. With reference to item 2), cancellation of the secondary ion yield change due to the transformed surface layers is achieved by taking a ratio of the specific ion current to total ion current.

New ion implant technique for low-cost solar cell fabrication

A new implant technique, in which a single magnet carries out mass separation and ion beam scanning, is described. Dose uniformity and energy conversion efficiency of a solar cell fabricated using this technique are investigated.

Sputtered neutral mass spectrometry using post-ionization in a microwave plasma

An experimental system for mass spectrometry of sputtered neutral particles using a microwave plasma operated in Ar gas at several 10−2 Pa is described. Preliminary experiments demonstrate that there is not a great deal of difference in the elemental sensitivities of GaAs and AgAu samples.