Abstract: As a rotating spoked substrate wheel passes across a beam stop during a scan cycle, a series of pulses are generated by the beam stop. These pulses are analysed to determine characteristics about the ion bam in an implanter. A digital signal processor (DSP) samples the beam stop current at regular intervals. By comparing the magnitude of successive samples, a dose uniformity map may be generated, so that identification of particular substrates on the wheel which have been dosed incorrectly is possible. The time taken for the beam to move between two points during the scan can also be measured from the sampled beam stop current. This provides a measurement of ion beam width. Similarly, by measuring, from the sample beam stop current, the time taken for the ion beam to pass between the middle of two adjacent substrates, the beam height may be ascertained.

Abstract: A performance parameter for an ion implanter is obtained by monitoring vacuum pressure in a vacuum chamber of the implanter to identify pulses of said pressure caused by outgassing from the wafer surfaces during respective scans or groups of scans of the wafer through the ion beam. The pressure values are integrated during the identified pulses to provide a series of pulse pressure integral values which provide the performance parameter. An increase in the integral values indicates deterioration in vacuum system performance.

Abstract: A charged particle filter provides a curved through path and has both magnetic poles for applying a magnetic field normal to the plane of curvature of the path and electrodes for applying a radial electric field. The filter is used as an energy filter downstream of an accelerator in an ion implanter. The filter can be set to provide a range of energy dispersions, to operate as an achromatic bend, or to reject lower charge state ions.

Abstract: The correct handover position between the gripper and the e-chuck is located using a light source and a 2-D photosensor. As the e-chuck is in the loading position it can be driven forwards or backwards in the beam direction by rotating the main whisper scan rotor. The line drawn across the 2-D array by a spot of light from the light source passing through a hole in a flag attached to the e-chuck is recorded. Similarly, the line drawn by a spot of light from the same source passing through a hole in the flag attached to the gripper is also recorded. The point of intersection is the ideal transfer point. For transfer the e-chuck is then driven to this point which can be checked from the 2-D sensor. The gripper is then also driven to the same point and alignment can be checked using the light source and sensor.

Abstract: The invention relates to an ion implantation apparatus comprising a vacuum chamber, an ion beam generator generating an ion beam in the vacuum chamber and an implant wheel in the vacuum chamber. The wheel has a plurality of circumferentially distributed wafer support elements. A scanning arm is mounted for reciprocal movement about a scan axis and has a free end supporting the implant wheel for rotation about a wheel axis, so that rotation of the implant wheel about the axis brings the wafer support elements successively to intercept the ion beam and reciprocation of the scanning arm about the scan axis scans the ion beam across the wafer support elements. A motor drives the scanning arm, the motor having a drive shaft connected directly to a cycloid type gearbox, the output of which directly drives the scanning arm.

Abstract: An ion implanter, the total return current between the substrate holder and flight tube is measured. Measuring the total current returned to the flight tube provides a useful indication of the total ion current in the ion beam leaving the flight tube as well as any electrons travelling back to, and being absorbed by, the flight tube. This in turn permits the quality of the ion beam post mass selection to be monitored, continuously if desired. The total current returned to the flight tube can be compared with the current measured by the beam, the latter varying rapidly with time as the beam stop is periodically occluded by the rotating substrate wheel. In order to general a potential difference between the substrate holder and the flight tube, either a power supply or an active resistance such as an FET chain can be employed.

Abstract: A beam/wafer alignment arrangement has a laser and sensor mounted on the scanning magnet. Direct alignment of the wafer relative to the scanning magnet is determined by reflecting the beam in a specular surface on the wafer holder back to the sensor. Correct alignment of the wafer translation direction is also confirmed from any movement of the reflected light spot on the sensor as the wafer holder is translated up and down. A further sensor is mounted on the beam stop to monitor any misalignment of the process chamber to the collimator magnet, and for checking the location of the travelling Faraday.

Abstract: An ion beam generation apparatus comprising an ion source (20) for generating ions, and a tetrode extraction assembly (11) comprising four electrodes for extracting and accelerating ions from the ion source. The extraction assembly comprises a source electrode (22) at the potential of the ion source, an extraction electrode (23) adjacent to the source electrode to extract ions from the ion source (20), a ground electrode (25), and a suppression electrode (24) between the extraction electrode and the ground electrode. Each electrode has an aperture to allow the ion beam to pass therethrough. The gap between the extraction (23) and suppression (24) electrodes is variable in the direction of ion beam travel.

Abstract: An ion implanter having a scanning arm which can pass vertically through ion beam, having a wafer loading/unloading position above the beam. The scanning arm also has capability for movement of wafer in its own plane when tilted relative to the beam, and there is also disclosure of a double scanning arm arrangement generating to/from a single wafer loader/unloader.

Abstract: A back scattered ion receiver is mounted on the process chamber of an ion implanter to receive beam ions back scattered from a wafer mounted on the wafer holder in the chamber. Minima in the intensity of back scattered ions as the wafer on the holder is moved relative to the beam direction, can be used to obtain an accurate calibration of the true beam direction. Beam direction error can then be compensated for when operating holder tilt and twist mechanisms so as to bring a process wafer accurately into the required orientation relative to the true beam. If the crystallographic alignment and orientation of process wafers has been precharacterised, this data can be used to control the wafer holder to align process wafers crystallographically to the process beam.

Abstract: A beam stop (23) has a charge collecting member (40) which extends in the direction of scanning of a scanned beam by less than the total distance scanned, so that variation in the charge signal derived from the collecting member can provide a timing signal for use in monitoring alignment of the scanned beam. In a preferred embodiment, the beam stop plate (42) has slits (65-69) leading to apertures (60-64) containing charge collecting rods (73-75) located within the thickness of the beam stop plate (42).

Abstract: A source of thermionic electrons is provided inside the flight tube of a magnet, especially an analysing magnet, and extends along the beam flight path. This allows space charge to be neutralised along the beam's axis in spite of severely restricted electron mobility in this direction owing to the presence of substantially transverse magnetic field. Thermionically emitted electrons may contribute directly to the neutralisation of space charge in positive ion beams, or, in the case of negative ion beams, indirectly by ionizing residual or deliberately introduced neutral gas atoms or molecules. Examples are described and claimed in which the source is arranged outside the nominal beam envelope in the flight tube, but linked to the beam by magnetic flux generated in the flight tube. This reduces erosion of the source by the beam and so reduces beam contamination. In these examples, an important feature is the provision of electron repellers to reflect electrons back and forth across the beam.

Abstract: A vacuum bearing structure comprises a combination of a planar gas bearing with a differentially-pumped vacuum seal. The bearing surface and the vacuum seal surfaces are formed of a porous material divided into a first outer region through which bearing gas can percolate to provide support and an inner second region providing the vacuum seal. An exhaust groove separates the two regions so that bearing gas can flow to atmosphere. The resulting structure can operate at a lower fly height to reduce loading on the differentially-pumped vacuum seal. The structure is particularly useful for motion feedthroughs into vacuum processes such as ion implantation.

Abstract: An ion electrode extraction assembly comprising an ion source 20 and at least one electrode 50 having a gap through which a beam of extracted ions passes in use. An electrode manipulator assembly 55 is provided to move the electrode so as to vary the width of the gap transversely to the ion beam, move the electrode transversely to the ion beam, and move the electrode in the direction of the ion beam. The three degrees of movement being carried out independently of one another.

Abstract: An electron flood apparatus for neutralizing positive charge build up on a substrate during ion implantation comprises a tube through which the ion beam passes to the substrate. Inert gas is supplied to the plasma chamber and a cathode in the plasma chamber is heated to emit electrons. An accelerating electrical supply is connected between a cathode and an accelerating electrode in the plasma chamber to accelerate electrons emitted by the cathode to produce a plasma in the chamber. A separate cathode bias electrical supply is connected directly between the cathode and the substrate common terminal to set a desired bias potential on the cathode relative to the substrate independently of the acceleration potential.

Abstract: A method and apparatus for generating an accurate, stable phase shift (b) in a sinusoidal signal employs fast analog multiplication to implement the trigonometric relationship sin(&ohgr;t+b)=sin(&ohgr;t)cos(b)+cos(&ohgr;t) sin(b). Cos(&ohgr;t) is generated by accurately shifting a signal sin(&ohgr;t) through 90° C. using a delay line, for example. Sin(b) and cos(b) are dc signals generated by digital to analog conversion, using a demanded phase shift (b) whose sine and cosine are obtained from look-up tables. A controller for controlling a phase shift in an rf cavity is also disclosed and operates on the basis of the same trigonometrical principle. The amplitude of the signals in the rf cavity is also controllable; fast analog multipliers are again employed to scale the signal amplitude to a nominal fixed value such as 1 volt.

Abstract: In ion implantation processes, secondary electrons are emitted from a substrate in an ion implanter during ion implantation and have the effect of producing excessive negative charge build up on the substrate damaging the substrate. An apparatus and a method is provided in which the negative charge build up on the substrate is restricted by extending a magnetic filter across the ion beam between a substrate holder and a plasma flood source of the ion implanter to deflect the secondary electrons with higher energies above about 15 eV out of the ion beam to be absorbed by a conductive element, preventing re-attachment of the high energy secondary electrons to the substrate and allowing lower energy electrons below about 15 eV, which are necessary for neutralising positive charge build up on the substrate caused by the ion beam, to diffuse across the magnetic filter without being deflected out of the ion beam.

Abstract: An apparatus used to control a workpiece inside a vacuum chamber. The workpiece is supported on a workpiece holder in the vacuum chamber. The workpiece is isolated from the atmosphere outside of the vacuum chamber by differentially pumped vacuum seals and an integral air bearing support. The differentially pumped vacuum seals and integral air bearing support allow for multiple independent motions to be transmitted to the workpiece supported by the workpiece holder. The workpiece holder motions provided are (1) rotation about the X axis, (2) translation back and forth along the Y direction of an X-Y plane on the surface of the workpiece holder, and (3) rotation of the workpiece in the X-Y plane about its Z axis. Concentric seals, oval for the translation motion and circular for the rotational motion, are differentially pumped through common ports to provide successively decreasing pressure and gas flow in order to reduce the gas load into the vacuum vessel to a negligible rate.

Abstract: An ion implanter employs two three gap rf accelerator stages to boost the implant energy after mass selection. The electrodes of the accelerator stages have slit-shaped apertures that accommodate high beam current, when the accelerator is in drift mode. By particular choice of the parameters of the accelerator, each stage of the accelerator produces accelerated ions having a relatively small energy spread, even though the acceptance range of the accelerator stage extends over a substantial phase angle of the applied rf voltage. The resulting accelerator is flexible, permitting a wide variation of output energies with good beam dynamics. Ion bunches from the first three gap stage are caused to have the correct flight time to reach the second stage for acceleration by adjusting the speed of the ions while maintaining the rf phase of the fields in the two stages locked to fixed values.

Abstract: A scan wheel for an ion implanter adapted for carrying a plurality of semiconductor wafers. The scan wheel being rotatable about an axis comprises a central hub, a plurality of separate spoke arms mounted on and extending from the central hub, and a plurality of wafer support elements on the outer ends of respective spoke arms. Each spoke arm has a dimension in the direction of rotation substantially less than the dimension of the corresponding wafer support element, a front face extending generally in the direction of rotation and side faces extending rearwardly from the front face. Each side face does not extend outwards beyond a rearward projection of the corresponding front face which, in a cross section, tapers symmetrically inwards, preferably by 7°, on each side relative to the axis of rotation.