Film thickness measurement using electron-beam induced x-ray microanalysis

A method for measuring at least one characteristic of a film stack on a sample, the method comprising:

• directing a charged particle beam towards the sample such that the charged particle beam completely penetrates at least two layers of the film stack, the charged particle beam causing X-rays to emanate from the sample;
• detecting X-rays at a first characteristic emission level that represents an emission level for a top layer of the film stack using at least a first wavelength dispersive X-ray detector that is positioned above the sample;
• detecting X-rays at a second characteristic emission level that represents an emission level for an underlying layer of the film stack using at least a second wavlength dispersive X-ray detector that is positioned above the sample, the underlying layer being a layer of material underneath the top layer;
• collecting data resulting from the detected X-rays, wherein the data that is collected is raw data;
• and
• comparing predicted data derived from one or more equations that model the film stack against the raw data.

An apparatus for measuring the thickness of two or more layers within a film stack sample, the apparatus comprising:

• a beam generator configurable to direct an electron beam towards the sample such that the electron beam completely penetrates at least two layers of the film stack, the electron beam causing X-rays to emanate from the sample;
• at least a first and a second wavelength dispersive X-ray detector positioned above the sample wherein each detector is configured to detect a respective portion of the X-rays emanating from the sample, whereby material characteristics of the at least two layers can be measured simultaneously;
• and
• an analysis unit that collects data resulting from the detected X-rays, wherein the data that is collected is raw data, the analysis unit also configured to compare predicted data derived from one or more equations that model the film stack against the raw data.