Masahiro Sumiya

Energy control of incident ions to the chamber-wall by using Push-Pull bias (phase-controlled bias) in UHF-ECR etching system

The effect of Push–Pull bias (phase-controlled bias) on the plasma potential and sputtering at the chamber-wall was investigated. It was found that the plasma potential could be controlled unrelated to the geometrical configuration of the chamber by using phase-controlled bias. The reason is that by using phase-controlled bias in the plasma with a magnetic field, the earth function of both electrodes facing each other can be controlled. Specifically, with the phase difference set to 180 degrees, the plasma potential was minimized and the decreased energy of incident ions to the chamber-wall reduced sputtering at the chamber-wall. Therefore, a stable process performance without particles caused by a sputtering at the chamber-wall, was expected by using Push-Pull bias in the dielectric UHF-ECR etching system.

Mechanism of the Reduction of Electron Shading Charge Build-up Using Pulsed Plasma

The effect of reduction of the electron shading charge buildup using pulsed microwave plasma was evaluated. The gate oxide voltage due to the electron shading effect was measured directly using a charging current measurement electrode on which a Si chip with a line-and-space (L&S)-patterned photoresist was mounted. The ratio of the electron saturation current to the ion saturation current (Ies/Iis ratio) in the open area and in the L&S area were also measured. In continuous wave (CW) plasma, the Ies/Iis ratio in the open area was larger than that in the L&S area, which causes the electron shading charge buildup. In pulsed plasma, the Ies/Iis ratio in the open area is equal that in the L&S area during the off-time period. This is the mechanism of the reduction of the electron shading effect by using pulsed plasma.

Particle Transport in Etching Chamber Influenced by Coulomb Force

Particle transport under Coulomb force during plasma on and off periods was studied in a plasma of mixed gases of Ar, O2, and N2 generated by a microwave electron cyclotron resonance plasma etching system. The relationship between the number of particles attached to the wafer and the wafer potential was studied, where the wafer potential was supplied by radio frequency (RF) and direct current biases during the plasma on and off periods, respectively. During plasma on periods, the particle counts decreased when a self-bias voltage on the wafer was large in the negative by increasing RF bias power. During plasma off periods, the particle counts decreased when the wafer potential was positive. These results show that particles charge negatively during plasma on periods and particles charge positively during plasma off periods. In this paper, it is found that controlling particle transport with the Coulomb force from the wafer potential is effective for particle attachment prevention.

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.

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.