Hitoshi Tamura

Atomic mixing in ion probe microanalysis

The atomic mixing due to a knock-on cascade has much influence on the depth resolution of ion probe microanalysis. The preliminary experimental results support the assumption that the depth resolution due to this effect is determined by the competition of sputtering rate and creation rate of atomic displacement.

Comment on “On the mechanism of liquid metal electron and ion sources”

The electric field near the anode of an electrohydrodynamic ion source is analytically discussed. For the field at the anode apex a rigorous analytical treatment results in the simple expressionE0≅VAC/(P0R0)1/2 differing by a factor of 1/2/32 from that by Gomer. Here,VAC is the applied potential to the cathode with regard to the anode,R0 the cathode distance from the anode center, andP0 the radius of curvature at the apex of the anode surface. The analytical forms for the radius of curvature and the electric field direction as well as the electric field itself at arbitrary points on the anode are derived.

Production of highly uniform electron cyclotron resonance plasmas by distribution control of the microwave electric field

We have developed the apparatus that can measure the three-dimensional distribution of microwave electric field intensity in electron cyclotron resonance (ECR) plasmas to investigate production and control of ECR plasmas. The relationship between the plasma properties of ECR plasmas and the microwave electric field intensity in plasmas is studied. We have confirmed that the pattern of the radial distribution of the ion saturation current at the electrode is the same as that of the microwave electric field intensity at the ECR zone. If the distribution of microwave electric field intensity at the ECR zone is uniform, the distribution of plasma density on the electrode becomes uniform, even if the distribution of microwave electric field intensity of the other zone is not uniform. Therefore, in order to obtain the optimum distribution of plasma density on the electrode, the distribution of microwave electric field intensity at the ECR zone must be controlled.

Slant Slot Antenna-Type Electron Cyclotron Resonance Plasma Source

A new compact electron cyclotron resonance (ECR) plasma source, which is termed slant-slot antenna-type ECR plasma source, is presented. Using this plasma source an ion saturation current density Iis of 6.2 mA/cm2±5.2% was obtained over a diameter of 300 mm under ambient conditions of Cl2 gas at 0.7 Pa. The features of the plasma source are an independent circular TM011 mode cavity resonator and slot antennas mounted in the shape of a ring at a constant slant angle to the surface current flowing at the bottom of the cavity resonator. As the result, microwaves of TE01 mode and others having a ring-shaped the electric field distribution can be introduced into the reaction chamber with high stability. This plasma source can generate a plasma with a ring-shaped Iis distribution stably, and it can control the Iis distribution by means of both the configuration of the magnetic field and the pattern of slot antennas. Therefore, the plasma source can generate a uniform plasma under a wide range of discharge conditions.

Measurement of a Three-Dimensional Distribution of Microwave Electric Field in Electron Cyclotron Resonance Plasmas

We have developed an apparatus that can measure the three-dimensional distribution of microwave electric field intensity in electron cyclotron resonance (ECR) plasmas. The reflection edge of the incident microwaves depends on the plasma density in the etching chamber: it is the ECR zone when the electron density (n e ) is above 1 x 10 11 cm -3 and the electrode when n e is below 1 x 10 11 cm -3 . The spatial distribution of the ion saturation current density at the electrode is the same as that of the microwave electric field intensity at the ECR zone. Therefore, in order to obtain uniform ion saturation current density, the intensity of the microwave electric field at the ECR zone must be kept uniform.

Evaluation of Charge Passed through Gate-Oxide Films Using a Charging Damage Measurement Electrode

A charging damage measurement electrode was used to model device structures. The charge passed through gate-oxide films (Qp) was measured in a cavity-resonator-type electron cyclotron resonance (ECR) plasma etcher for 12-inch wafers and the reduction of charging damage was investigated. Parallel circuits composed of resistors and condensers were modeled after the current–voltage (I–V) characteristics of the gate-oxide film. The electron shading effect was introduced by mounting a Si chip with line and space (L&S)-patterned photoresist on the probe, which corresponded to the gate electrode. The reduction of charging damage using the time modulation (TM) bias was determined by evaluating Qp and the damaged test element group (TEG) wafer. This charging damage measurement electrode is effective for investigating the reduction of charging damage in particular, of the etcher used for 12-inch wafers.

Study on the Distribution Control of Etching Rate and Critical Dimensions in Microwave Electron Cyclotron Resonance Plasmas for the Next Generation 450 mm Wafer Processing

A newly designed microwave electron cyclotron resonance (ECR) plasma etching reactor has been developed for 450 mm wafer processing. The etching rates of polycrystalline silicon (poly-Si) and SiO2 across the wafer were evaluated as a function of ECR position. Two-dimensional (radial and vertical) distributions of the ion flux in the reactor were also investigated using a movable single probe system. A ring-shaped region of high-density plasma along the ECR plane was observed. This reveals the mechanism that the etching-rate distribution could be controlled by the ECR position. As a result, a polycrystalline silicon etching rate uniformity of 1.5% across a wafer was successfully obtained. Furthermore, the uniformity control of critical dimensions (CDs) based on wafer temperature was also investigated, and CD uniformity below 3 nm across the wafer was obtained in the optimum temperature distribution.

Knock-on Effect in Surface Analysis

A knock-on effect during ion bombardment was studied from computer simulation. The preliminary results obtained for the bombardment of argon ions with energies of 5 keV and 10 keV on silicon a target having a random lattice are described.