Radiant energy – Electron energy analysis
Patent
1991-11-07
1994-06-07
Berman, Jack I.
Radiant energy
Electron energy analysis
H01J 4944
Patent
active
053191978
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a process for monitoring ion-assisted processing procedures on wafers in a process chamber and an apparatus for carrying out the same.
BACKGROUND OF THE INVENTION
Ion-assisted processing procedures are employed both for the removal of material as well as for the application of material, respectively the coating of semiconductor, metal, glass or plastic substrates. The aforementioned materials are summarily referred to hereinafter as "wafer".
Processing procedures in which materials are removed may be, by way of illustration, reactive ion etching "RIE", magnetically enhanced RIE "MERIE", triode etching, reactive ion beam etching "RIBE", chemically assisted reactive ion beam etching "CAIBE", ion milling or sputtering.
In all ion-assisted processing procedures it is essential for conducting the processing to know the energy of the ions and the divergence of the ion beam. Furthermore, in a number of cases it is of importance to determine the possible charging of the wafer as, in particular, with thin insulating layers even minimal charging can cause voltage breakdowns. Furthermore, by way of illustration, in the case of RIE it is necessary to determine the etching rate "in situ", respectively to have an "endpoint control" of the processing procedure.
Determination of the aforementioned values, respectively processing parameters, is only possible in accordance with the state of the art by means of a number of different measuring processes, which, under circumstances, have to be employed simultaneously in a process chamber. Thus presently the divergence of the ion beam is usually measured (measurement of current) with "conductive cups". The arrangement of the measuring devices in a process chamber necessary for this purpose however "disturbs" the ion beam and therefore the processing procedure. The thickness of the layer, on the other hand, is usually measured interferometrically so that the process chamber has to be designed in such a manner that, by way of illustration, a laser interferometer may be utilized, cf. e.g. the PCT application WO 88/07261. The use of an optical spectrometer for the chemical identification of reaction products of the surface of a wafer is also described in this printed publication.
SUMMARY OF THE INVENTION
The present invention provides a process for monitoring ion-assisted processing procedures on wafers in a process chamber with which magnitudes, i.e., processing parameters, essential for conducting the processing may be determined practically simultaneously with a minimal amount of time, effort and cost.
In the invented process it was recognized that the magnitudes, i.e. process parameters, of importance for the ion-assisted processing procedures on wafers can be determined by means of emission spectography of the operational gases present in the process chamber. Operational gases mean all the gases present in the process chamber, thus, by way of illustration, the ions or fast neutral particles) supplied by the ion source, the background gas present in the chamber (typical pressure in the operation chamber.apprxeq.10.sup.-6 -10.sup.-7 mbar), additional operational gas present in the process chamber as is the case in CAIBE processes or coating, or reaction products of the surface.
On the way between the ion source and the wafer surface, a part of the ions collides with neutral particles in the process chatter. With a certain degree of probability, these collision processes result in electronic excitation of the colliding ions and particles. The light generated in "neutralizing" the electronic excitation is "Doppler shifted" toward longer wavelengths, that is "red-shifted", compared to thermal particles due to the velocity of the colliding particles and ions.
From the distance between, e.g., the red-shifted maximum and the unshifted maximum, which occurs with thermal Particles, therefore the velocity and thus the energy of the particles can be calculated.
Moreover, with a certain degree of probability, the particles refl
REFERENCES:
Heinrich et al., Applied Physics Letters, vol. 55, No. 14, Oct. 2, 1989, 1474-1476.
Burrell et al., Review of Scientific Instruments, vol. 5, No. 11, Nov. 1980, pp. 1451-1462.
Dzioba et al., Journal of Applied Physics, vol. 53, No. 6, Jun. 1982, pp. 4389-4390.
Berman Jack I.
Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung
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