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Plasma cleaning by use of hollow-cathode discharge, where RF voltage was supplied with the same phase on both electrodes, was investigated in a CHF3-SiO2parallel-plate-type dry-etching system. The plasma cleaning by use of the hollow-cathode discharge has achieved a high plasma-cleaning rate, because the electrons were confined by the opposite ion sheaths' electric field and high-density plasma was generated between the electrodes. With the heating of the reaction chamber wall, the plasma-cleaning rate was increased and the deposition rate of the plasma-polymer was decreased. The temperature of the reaction chamber wall was found to be one of the important parameters affecting the etching characteristics, such as the SiO2/poly-Si selectivity.

A thermally controllable quartz bell jar with a SnO2transparent thin-film heater was developed. The heating effect of the quartz bell jar on plasma cleaning and etching was investigated in a CHF3-SiO2microwave etching system. By means of quartz bell jar heating, plasma polymer deposition on the inside wall of the quartz bell jar was decreased, the plasma-cleaning time was shortened and the SiO2/poly-Si selectivity was increased. In the reaction chamber, etching and plasma polymerization take place on the reaction chamber wall as well as on the wafer. The concentration distribution of radicals and ions in the plasma is dependent on these reactions. Accordingly, control of the reaction chamber wall temperature is important both to improve the etching characteristics and to prevent time fluctuation of the etching characteristics.

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 (ne) is above 1×1011cm-3and the electrode when neis below 1×1011cm-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.