Patent FR-2805925-A1 (FR)
Title: Method and equipment for controlling uniformity of treatment of substrate surface by action of particle beam, which includes measuring emitted photons, for use in microelectronics
Inventor: BORSONI GILLES
IPC: H01J37/304
Filed: 2000-03-01
Abstract: The method for the control of uniformity of treatment of the surface layer (101) of a semiconductor wafer (100) with substrate (102) by particle beam (F) of e.g. Argon ions includes an instantaneous measurement of the number of photons (1) emitted due to the interaction of particles with the surface and is carried out in connection with the detection by imaging in each elementary zone of the surface as defined on the basis of the resolution of formed image and in the course of all treatment. A variation in measurement is determined as a function of the position of emission zones in order to determine an average of the spatial distribution of the emission intensity and to measure a fault in the uniformity of treatment proportionally to the difference with respect to the average.  A step of adjustment or stop of treatment to set off when the fault in uniformity is greater than a predetermined critical value. A step of measuring the energy of photons detected locally is provided in order to follow the advance of treatment and to adjust or stop the treatment when the energy variation exceeds a predetermined difference in a given period. A step of measuring the total number of photons for at least one energy level is provided. An analysis of spatial distribution of emission intensity determines the local fault of uniformity and a modulation of beam scanning required to correct the fault. The means for selecting particles in velocity and direction are subjected to the analysis of spatial distribution, and comprise collimation which selects particles in direction. The measurement of uniformity of treatment is recorded for historic tracing of parameters in successive applications to each wafer passing in the production line. The equipment comprises a photon detector (103) which forms a digital image and is connected to a signal processing and data management unit (104). The photon detector is a digital camera or photo-digital apparatus equipped with a charge-coupled device (CCD) for intensity measurements, where the wavelength of light emitted from each elementary zone of treated surface corresponds to each pixel, and after calibration, to the number of photons received by each pixel. An evolution of intensity of dominant colors is determined in order to follow the evolution of treatment. The photon detector is cooled by a device operated by the Peltier effect, or by a cryogenic fluid. The means for selecting particles are controlled by the unit (104) as a function of measurements and comprises a set of adjustable caches for local adjustments of particle flux in order to compensate the uniformity fault. The photon detector is zoom-focused on a part of treated surface in order to increase the resolution, and the scanning by photon detector is synchronized with the scanning by ion beam. The photon detector is mounted on a motorized platform and is subjected to successively irradiated zones. Several monochromatic photon detectors are utilized in combination with a wavelength separator.