Jerald Paul Dykstra

Overview of the Eaton NV-8200P high beam purity, parallel scanning implanter

Eaton has developed a medium current ion implanter to meet the requirements of emerging advanced semiconductor processes. Hybrid scanning with a novel electrostatic scan angle correction lens is used to control beam incidence. To insure repeatability of processes requiring true beam incidence control, in-situ beam profiling and two axis divergence measurement provide input to the auto-tuning system. The direction of the mechanical axis of scan is always parallel to the wafer surface so that the distance from the wafer to the various optical elements is constant for all wafer tilt and twist combinations. This feature reduces variation in beam spot size and divergence across the surface of the wafer. Specific techniques for addressing all the various forms of beam and wafer contamination are also discussed. Two beam energy filters are utilized, including one immediately before the target, to maximize energy purity when multi-charged, decelerated, or molecular beam species are implanted. The vacuum system is designed to enhance beam purity and for ease of maintenance. The system provides useful beams over the energy range of 3 to 750 keV. The control system and ion source technology are based on that used in the companys high current implantation systems.

Beam incidence variations in spinning disk ion implanters

Abstract Recent trends in high density semiconductor processing technology are resulting in increasingly stringent requirements for spatial uniformity of beam incidence upon the wafer, as well as greater versatility in controlling the angles of wafer tilt and twist. These requirements have resulted in the production of a new generation of spinning disk mechanical scanning implanters capable of easily varying wafer tilt, including repositioning during implant. Greater versatility has also increased the difficulty in visualizing beam incident angle (tilt and twist) variations. A generalized model for calculating these variations is derived and presented. Graphs generated by the model may be used to evaluate various configurations of commercially available spinning disk mechanically scanned batch ion implanters.

NV-6208: A midcurrent ion implanter with constant beam angle of incidence

Abstract Several ion implantation applications achieve superior yields when the ion beam strikes the wafer with a constant angle of incidence across the entire surface of the wafer. Batch end stations with mechanically scanned disks provide implants with constant incident angle, but may not be economical for low dose implants. A midcurrent implanter having a pick-and-place serial endstation has been designed to provide constant implant angle. The equipment utilizes a novel combination of electrostatic X – Y raster scanning with small mechanical movements of the target to achieve a constant beam incident angle. Scanning and target motion are servoed to beam current variations. Wafers of 200 mm diameter can be implanted at a rate of 250 per hour. A system description and performance measurement results are presented.

Process and equipment considerations in the implantation of GaAs

Ion implantation of GaAs presents process requirements differing from standard silicon processing. Different implant species having differing source requirements are commonly used. GaAs devices may be susceptible to different contaminants, including some which are common construction materials in implanters intended for silicon implant applications. Because of its physical characteristics, GaAs poses different handling challenges. In some situations, implantation of GaAs at elevated temperatures is preferred. We examine some of these differences between silicon and GaAs processing and describe standard features and optional adaptations of a medium current ion implanter that facilitates processing of GaAs. These include source adaptations, wafer clamping and sensing adaptations, and a capability to implant at elevated substrate temperatures.

Enhanced ionization freeman ion source

Abstract We developed modifications to a standard Freeman ion source which increased the plasma electron temperature and density by minimum factors of 1.5 and 1.1, respectively. The improvement in these fundamental plasma parameters resulted in a greater than 40% increase in B+ currents from boron trifluoride gas and substantial usable beam current increases in B2+, P2+, and As2+. A large increase in triple charge currents was also present in the extracted beam. Ion source lifetime tests were performed at 1 mA scanned B+ wafer current with a 125 mm aperture on an Eaton NV-6200 Ion Implanter. Filament lifetime was observed to be in excess of 50 h. Further, erosion was more uniformly distributed along the filament length and tests indicate that the extracted ion beam uniformity was increased along the extraction slit. Therefore, we conclude that our modifications to the standard Freeman ion source also increased discharge uniformity.

A versatile ion implanter for planar and 3D device construction

Abstract The ever increasing demand for smaller devices is creating a new set of performance and reliability problems. Overcoming these problems requires sophisticated device structures incorporating advanced knowledge of device physics coupled with improved process uniformity and precision. Fabrication of such structures in silicon and compound semiconductors is generating demands for new process technology. An ion implanter has been designed specifically for improvement of process control and construction of advanced three-dimensional device structures. The instrument uses a programmable goniometer as the target positioning system. This versatile end station, combined with a sophisticated automation and control system, is designed to meet the emerging requirements for flexible target positioning and repositioning for both planar and 3D structures. Details of the design of this new ion implanter are described and performance specifications are presented.

Versatile ion implanter for submicron and 3-D device engineering

Device scaling trends have resulted in smaller devices having new performance and reliability problems. Hot electron effects and difficulties in obtaining precise device structures and performance are among the most severe. Sophisticated and novel device structures incorporating advanced knowledge of device physics combined with better process uniformity and precision are required to overcome these problems. Fabrication of such structures demands new process technology to form the desired structures. An ion implanter has been designed specifically for submicron applications and for construction of advanced three-dimensional (3D) device structures. The instrument used a programmable goniometer as the target positioning system. This versatile endstation is designed to meet the emerging requirements for flexible target positioning and repositioning in submicron applications and other 3D devices. Some contributions of these new implanter features to device performance will be discussed. Specific examples of source-drain engineering applications (LATID - Large Angle Tilt Implanted Drain and LATIPS - Large Angle Tilt Implanted Punch-through Stopper devices), 3D structure applications (trenches), and channeling control applications are identified and discussed. The implanter is described together with some of its performance specifications.