Method and apparatus for identifying the chemical composition of a gas
Embodiments of the present invention relate to the analysis of the components of one or more gases, for example a gas mixture sampled from a semiconductor manufacturing process such as plasma etching or plasma enhanced chemical vapor deposition (PECVD). Particular embodiments provide sufficient power to a plasma of the sample, to dissociate a large number of the molecules and molecular fragments into individual atoms. With sufficient power (typically a power density of between 3-40 W/cm 3 ) delivered into the plasma, most of the emission peaks result from emission of individual atoms, thereby creating spectra conducive to simplifying the identification of the chemical composition of the gases under investigation. Such accurate identification of components of the gas may allow for the precise determination of the stage of the process being performed, and in particular for detection of process endpoint.
1. A method comprising:
etching a silicon-containing dielectric film at sub-atmospheric pressure;
detecting an optical emission only from an atomic silicon associated with gas sampled after the etching of the silicon-containing dielectric; and
determining, using a processor associated with a computer system, an end point of the etching by monitoring a change in intensity of a wavelength of the optical emission only from the atomic silicon associated with the sampled gas.
2. The method of claim 1 , wherein a first plasma is utilized to perform the etching.
3. The method of claim 1 , wherein a second plasma is generated remote from the gas sampled after the etching in a processing chamber.
4. The method of claim 3 , wherein a power density of about 20 W/cm 3 is applied to the sampled gas to generate the second plasma.
5. The method of claim 1 , wherein the wavelength is 243.589 nm, 250.766 nm, 251.508 nm, 251.6870 nm, 251.9960 nm, 252.4867 nm, 252.9269 nm, 288.2424 nm, 390.6629 nm, 729.1181 nm, 740.7814 nm, or 742.5542 nm.
6. The method of claim 1 , wherein the change in intensity of the wavelength comprises a decline in intensity.
7. The method of claim 1 , wherein the change in intensity of the wavelength is 0.1% or greater.
8. The method of claim 1 , wherein the endpoint is determined based upon a change of intensity of a plurality of wavelengths associated with atomic silicon.
9. The method of claim 1 , wherein the dielectric film also contains oxygen.
10. The method of claim 9 wherein the endpoint is determined by also detecting a change in intensity of optical emission of atomic oxygen.