Patent FR-2792455-A1 (FR)
Title: Method and apparatus for correction of integrated circuit by use of focused ion beam system controlled by temporal variation in detected rate of secondary particles emission
Inventor: BENTEO BRUNO
IPC: H01L21/20
Filed: 1999-04-16
Abstract: The method and apparatus is for the conduct of deposition or etching in a correction zone of a layer of conducting material in an integrated circuit mounted on a support (3) by use of a focused ion beam (FIB) generated in a column (2) comprising means for the beam scanning.  The process includes an application of a sequence of electric signals to the integrated circuit input which produce erroneous and corrected output signal, a detection of thee rate of secondary particles emission in the measurement zone by a photomultiplier (4) connected to the column (2), an evaluation and recording of the measured temporal profile of the rate of secondary particles emission in an interval corresponding to at least a part of the sequence, and a comparison of the measured temporal profile too a reference profile for the control of operation of deposition or etching. The evaluation of the measured profile is carried out by scanning the measurement zone by the focused ion beam in a window corresponding to that zone, the sampling of the detected rate of secondary particles emission, and by carrying out a set of measurements each giving a digital value stored in an acquisition unit (19). The sampling frequency is greater than 1 MHz, and is of an order of 10 MHz. The sampling frequency is not less than the scanning frequency. The direction of the focused ion beam is substantially perpendicular to the direction of propagation of electric signals in the measurement track, and the scanning window has a width which is less than that of the measurement track. The control includes a possibility of periodical switching of two configurations of the focused ion beam, the first corresponding to the operation of deposition of the operation. The minimum energy of the beam is of an order of 3 keV. The etching operation for cutting a track includes a selection of two measurement zones on opposite sides of the etching zone, and a use of the second measured profile as a reference profile. The etching operation for cutting a track can include a selection of the first measurement zone on the etching zone, and use of the measured profile obtained before the start of etching operation as a reference profile. The deposition operation for connecting two conducting zones includes a selection of first and second measurement zones, and a use of the second measured profile as a reference profile. The process can comprise a preliminary stage of exposition of a conducting zone by etching a dielectric material, and includes an application of a sequence of electric signals producing a predetermined output profile, the detection of the rate of secondary particles emission above the etching zone, the evaluation and storage of measured temporal variations, the comparison of measured to predetermined profiles, and interrupting the operation when the two profiles become similar. The apparatus comprises the means (1) for the generation of the focused ion beam and its application to the surface of the integrated circuit, the means (4) for the detection of the rate of secondary particles emission, the means (9,10) for electric stimulation of integrated circuit by the application of the sequence of electric signals, and the means (19) for the evaluation and storage of measured profiles of the rate of secondary particles emission.