The present invention relates to a method of analyzing data obtained from a semiconductor etching apparatus for micromachining a semiconductor wafer using plasma, and this semiconductor etching apparatus.
In order to acquire the microscopic shape of a semiconductor device formed on a wafer, the following etching processing is performed: Namely, a substance is brought into its ionized state (i.e., its plasma state). Moreover, the substances existing on the wafer are removed by the action (i.e., reaction on the wafer surface) performed by this plasma-state substance.
An ionization phenomenon based on plasma is accompanied by the resultant light-emission phenomenon. Accordingly, an optical emission spectroscopy unit (:OES) is mounted on a plasma-used etching processing apparatus so that the light emitted from the plasma can be monitored. The data measured and acquired using this optical emission spectroscopy unit, hereinafter, will be referred to as “OES data”. Also, the following control technique is applied to this etching processing apparatus: Namely, in this control technique, the etching processing result is stabilized by measuring the OES data, and adjusting the etching processing condition in accordance with the measurement result of the OES data.
The OES data is configured from the values of the light-emission intensities at a plurality of wavelengths and times. The adjustment of the etching processing condition requires that a wavelength and a time be selected out of this OES data. Here, it has become a problem that a suitable combination of the wavelength and the time be selected from among these plurality of wavelengths and times. As the method for selecting the wavelength to be used for the control over the etching processing, there have been known methods disclosed in JP-B-3732768. Here, the methods disclosed in JP-B-3732768 are as follows: The method of predicting the etching processing result by selecting the wavelength of the plasma light-emission using the aperture ratio, and the method of adjusting the etching processing condition in accordance with the prediction result.
In the methods disclosed in JP-B-3732768, however, no consideration is given to the fact that a variation occurs in the OES data if the etching processing condition is adjusted. On account of this, depending on the wavelength and time selected, a variation occurs in the OES data if the etching processing condition is adjusted. As a result, it has become a problem that the etching processing condition cannot be adjusted suitably.