Specific Process Knowledge/Etch/OES: Difference between revisions
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The section below describes the principle behind the optical endpoint detection system. | The section below describes the principle behind the optical endpoint detection system. | ||
== Optical Emission Spectroscopy == | == Using Optical Emission Spectroscopy as endpoint detection == | ||
'''The etch process:'''<br> | '''The etch process:'''<br> | ||
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'''The plasma:'''<br> | '''The plasma:'''<br> | ||
Inside the process chamber, the RF field will | Inside the process chamber, the RF field will ionize the gas molecules to form ions, radicals and free, fast moving electrons. Much lighter and hence more mobile, the fast moving electrons collide with the gas constituents, the latter are pushed into excited states from which they may decay under emission of photons. This is what makes the plasma glow as these photons typically have an energy in the visible range. As each component in the plasma has a unique set of allowed excited states one can extract the information about composition of the plasma by analyzing the light coming out of it. | ||
'''The OES hardware:'''<br> | |||
On a viewport preferably directly facing the plasma above the wafer, a lens is mounted to focus the emitted light onto an optical fiber. | |||