Method for measurement of beam emittance in a charged particle transport system

#Not Applicable

#The methods and systems relate to charged particle transport and more specifically to measuring beam emittance in a charged particle transport system.

#Ion implantation is a standard technique generally used for modifying surface properties of materials. In the semiconductor industry, ion implantation techniques are used for introducing conductivity-altering dopant materials into semiconductor wafers. In a conventional ion implantation system, a desired dopant material is ionized in an ion source, the ions are accelerated to form an ion beam of prescribed energy, and the ion beam is directed at the surface of the wafer. The energetic ions in the beam penetrate into the bulk of the semiconductor material and are embedded into the crystalline lattice of the semiconductor material.

#The following figures depict certain illustrative embodiments in which like reference numerals refer to like elements. These depicted embodiments are to be understood as illustrative and not as limiting in any way.

#FIG. 1 shows a schematic representation of an ion implantation device having a mechanism that can be moved within the ion beam;

#FIGS. 2a and 2b are sample current profiles for an ion implantation device; and

#Ion implantation equipment currently in use typically may be capable of providing measurements of beam current at one or more positions along the beam path. In some instances, these current measuring components, i.e., current sensors or Faradays, may be designed to measure the entire beam current, and in other instances a small Faraday or sample cup with a narrow slot for an aperture may be used to sample the beam at one particular coordinate with respect to the beamline axis. It can be understood that current sensors having a variety of shapes and sensing means may be used. The description herein with reference to a Faraday, or sample cup, may provide a known example of a current sensor, but the method and system may not be limited thereto.

#When the beam upstream of such a sample cup is traversed by an aperture or obstacle moving perpendicular to the long dimension of the sample cup, ion beam emittance, i.e., the beam current density as a function of position and direction, may be determined from variations in the current measured at the sample cup as the aperture or obstacle traverses the beam, for positions of the leading and/or trailing edges of the aperture or obstacle intercepting the beam and directions (angles with respect to the beamline axis) along a line in the position-angle emittance plane.

#If the beam is directed primarily along its axis in the z direction, with the aperture or obstacle moving across the beam in the x direction, and the sample cup slot long dimension oriented in the y direction, the current density as a function of position (x,z) of the leading and trailing edges of the aperture or obstacle and direction (θ) from the leading and trailing edges to the sample cup may be determined. The angle θ is the angle between an element of beam and the z-axis in the x-z plane. At different x positions in its travel, different corners of the aperture or obstacle, at different z coordinates, may define the leading and trailing edges intercepting the beam. Beam current density data for these different z coordinates may be transformed to a common x-y plane (common z-coordinate), where the data points will fall on a nearly straight line in the position-angle (x-θ) emittance plane.