End-point detection in plasma etching or phosphosilicate glass

A method for detecting end-point in the plasma etching of a phosphorous doped silicon dioxide layer coated on a substrate of single crystal silicon comprising the steps of;

• etching the phosphorous doped silicon dioxide from the substrate within an etching chamber with gas from the fluorinated hydrocarbon family,
• spectroscopically observing the gases in the etching chamber over a time interval covering the beginning and end of the etching process and within a predetermined wavelength interval,
• observing the presence of the phosphorous atomic line straddled by two argon atomic lines at the beginning of the etching process,
• observing the disappearance of said phosphorous atomic line from between said two argon atomic lines as an indication of the end of the etching process.