The charge build-up in an electron cyclotron resonance (ECR) etcher has been studied experimentally and theoretically. The experimental results show that the charge build-up profiles of the wafer are convex and positive, and are detected only when the RF bias exists. We have derived a simplified equivalent circuit model for the wafer in an ECR etcher. The charge build-up profile predicted with the simplified equivalent circuit model shows a good agreement with the experimental results. It is concluded that the variation of plasma potential caused by the radial RF current across the magnetic field results in the charge build-up.

The effectiveness of a curved lateral magnetic field has been examined in magnetically enhanced reactive ion etching (MERIE). It is demonstrated that both charge build-up and etching nonuniformity are suppressed at the same time when the offset angle of dipole magnets is adjusted to 10°. Theoretical analysis of electron flow in the curved lateral magnetic field suggests that the plasma electron multiplication effect along E×B drift motion is compensated by the divergence of the drift motion at the optimum condition, and it results in uniform plasma generation. Although the definite mechanism of charge build-up is still not clear, this study indicates the importance of plasma uniformity in controlling the charge build-up in a MERIE system.

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The charge buildup in a magnetron etcher has been studied experimentally for two different magnet arrangements and theoretically on the basis of an equivalent circuit model. Wafer charging measured with a metal-Si3N4-SiO2-Si (MNOS) capacitor is negative along the centerline of the magnet poles and positive between the magnets in both cases. Wafer charging is explained either by curtent crowding at the center of the magnet poles or by the nonambipolar diffusion effect.

Wafer charging in barrel etchers, reactive ion etching (RIE) etchers, magnetron RIE (MRIE) etchers and electron cyclotron resonance (ECR) etchers are characterized. The charging voltages were measured by using electrically programmable non-volatile memories. The charging profile for the barrel etchers and the RIE etcher depends critically on the electrode arrangements and wafer locations, while that in the MRIE etchers and the ECR etchers depends on the structure of the magnetic field. Even in the case of a non-divergent magnetic field ECR etcher, wafer charging is built-up when an RF bias is applied to the wafer stage.By analyzing these results, two charging mechanisms are distinguished. One is the plasma nonuniformity around the wafer, which depends on the RF electrode and the wafer location. The other is the anisotropy of the magnetized plasma, which depends on the structure of the magnetic field. Some of the charging profiles due to the former effect is reproduced by using an equivalent circuit model. It is found from the model that even in the uniform density plasma, wafer charging is induced by the RF current which causes a plasma potential variation across the wafer surface.