Texas Instruments Corporation

Other

Simon C Garth

Denis F Spicer

William C Nixon

John N Sackett

Electron beam apparatus for use in testing integrated circuits uses a magnetic electron objective lens having a first end adjacent the circuit under test and a second end remote from the circuit. The magnetic field of the lens increases steeply to a maximum near the first end and falls gradually towards the second end. Secondary electrons emitted from the circuit are accelerated strongly by an electrostatic field into the first end of the lens and are retarded abruptly to speeds of the same order as their emission speeds in the region of maximum magnetic field. Further gradual retardation of the electrons takes place so that the electrons approach the second end of the lens parallel to the axis of the lens at substantially their emission speeds. A filter grid located at the second end of the lens and a collector of electrons passing through the filter grid enable the emission speeds of the secondary electrons to be measured.

Electron beam apparatus and method for detecting secondary electrons

Apparatus for producing a pulsed electron beam, particularly adapted for inspecting integrated circuits, includes a beam scanner (10) for causing a continuous electron beam to scan a circle, which beam may emerge from the second of three electrostatic lenses of an electron beam microscope. The beam then passes a deflecting means (12) on the circle for deflecting the beam in a radial direction at selected locations, before being collected by means (14) for collecting the electron pulses from alternate locations to provide a pulsed electron beam.

Production of pulsed electron beams

An electron beam apparatus in which the electron beam is directed to a sample and secondary electrons from the sample return in the direction of the beam and are deflected sideways to a collector by a first electrostatic deflection means. To compensate for distortion of the spot produced by the beam as a result of the first electrostatic deflection means, a similar deflection means is placed above the first means to correct the distortion and is so biased as to reflect secondary electrons which might otherwise pass the first means. The deflection means are 4-pole electrostatic stigmators. A threshold grid is biased to allow to pass to the first means only those secondary electrons having release speeds from the sample above a certain value.

Electron beam apparatus

Electron detector apparatus and method for detecting secondary electrons released from a body, of particular utility in testing integrated circuits in an operational state. The apparatus utilizes a magnetic lens having an axis of symmetry, for producing a magnetic field that progressively weakens along the axis, so that the secondary electrons travel through the magnetic lens in progressively elongated helical paths and approach an electron retarding means, for example a planar grid, at approach angles to the direction of the axis such that their approach speeds along the axis are substantially equal to their actual speeds. The secondary electrons are collected after passage through the retarding means. Alternatively, the secondary electrons may be directed through a magnetic lens having an axis of symmetry to focus them at a small region at one end of the lens on which a part spherical electron retarding electrode is centered, such that the focussed secondary electrons proceed along radial paths to the retarding electrode, such that their approach speeds are substantially equal to their actual speeds.

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Cambridge, United Kingdom

Simon C Garth