Reuel B. Liebert

Performance characteristics of the extrion 160-10 ion implantation system

Abstract The Extrion 160-10 ion implanter has been developed to meet the needs of users requiring high dose implants at high throughput over a wide dynamic range of species and energies. A unique three stage acceleration system provides the capability of high transmission transport over the full energy range of 40 to 160 keV. As+ output of 10 mA and B+ output of 5 mA are available over the full range of operation. Post acceleration analysis is utilized to remove molecular breakup contaminants commonly produced in acceleration systems. Dual end stations are provided in the system to give throughputs of 375 wafers per hour in the handling limit for 100 mm wafers while maintaining 160 wafers per hour at a dose of 1 × 1016 atoms/cm2. Wafer processing can be controlled using data logger and implant monitor options, and a host computer link is available to interface with factory automation systems. This paper presents a system description and gives data to characterize the performance of the implanter in beam current, dose uniformity, automated operation and othe rareas of interest.

Dose control system for the Extrion 1000 ion implantation system

Abstract The next generation of ion implantation systems requires more stringent controls on the reproducibility and uniformity of dose accuracy on both a day-to-day and batch-to-batch basis. Integration of process controls, vacuum transient immunity, channelling control, and wafer surface charge neutralization in an automated environment will be assumed. This paper describes a dose measurement and control system for Varians new Extrion 1000 batch process ion implantation system.

New method of solid state wafer cooling in the Extrion 1000 high current ion implantation system

Abstract A new method of wafer cooling during implantation has been developed which meets the process needs of the 1990s. Cooling levels four times better than existing gas cooling techniques are achieved in a clampless, low stress system designed for high beam power. A new antistick technology is described which reduces particle contaminations and wafer breakage.

Planar channeling effects in a batch process ion implanter

Abstract In batch process implantation systems, the presence of platen rotation and the possible use of domed platens produce averaging effects which complicate the design of implant geometries to minimize channeling. Data is presented for both flat and domed platens with different wafer orientation (twist) angles. Evidence is shown that channeling effects can be equivalently reduced for both flat and domed geometries.

Implant dosimetry results for plasma doping

A system for accurate and repeatable implant dose measurement for plasma doping architectures must circumvent a number of possible pitfalls. Such a system must accurately count ions crossing the pulsed plasma sheath to the wafer surface, while that surface is typically at high potential and immersed in the ambient plasma environment of the wafer. The effects of secondary electrons and the capacitive displacement current must be suppressed and the measurement itself must not alter the plasma or be affected by the high potential of the wafer bias. Traditional Faraday systems do not address these requirements. A new dose measurement system has been developed to meet the needs of pulsed plasma doping and the performance of that system for dose accuracy, repeatability, and uniformity is described.

The Extrion 1000: A new high current ion implantation system for automated fabrication environments and intelligent process control

Abstract The next generation of ion implantation systems will require new techniques for intelligent process control while satisfying the increasing need for high reliability and serviceability. The Extrion 1000, a new Varian batch process ion implantation system designed to address these needs, is described. The new implanter features extensive real time process monitoring capability, failure prediction technology, wide dynamic range, and rapid changeover between processes requiring different implant angles or wafer sizes. Adaptive control techniques are used within the framework of an automated fabrication environment to assure high yield and throughput.

Three-stage acceleration system for high energy implanter

Abstract A new, higher voltage front end has been designed for Varians high current ion implanter to upgrade its voltage capability to 160 kV. Beam extraction and acceleration are accomplished in a compact three-gap electrode system in which each gap is designed for 70 kV. At energies above 70 kV the beam is accelerated through all three interelectrode gaps. At 70 keV and below the system can be operated in a deceleration mode which permits beam extraction with the maximum 70 kV voltage across the first gap and subsequent deceleration to implant energy in the next two gaps. Details of the system as well as results of beam current measurements as a function of energy are presented.

A technique for optimizing the dose uniformity of a magnetic scanning high current implanter

Abstract Magnetic scanning high current implanters pose a unique challenge to achieving the wafer doping uniformity that is typical of serial implant, lower current machines. Precise control of the beam centroid location over the spinning disk is essential to the achievement of good wafer uniformity, as evidenced by machine performance and computer simulation. A technique has been developed on the Varian/Extrion 120-10 to obtain this control as well as compensate for any machine aberrations to improve the dose uniformity over a wide range of implant conditions. This technique uses the machine computer system and the actual implanted wafer resistivity data to determine an improved functional dependence of the scan rate with beam location. Subsequent implants are then run with this compensated scan rate information. Successful use of this technique at the 1% level will be demonstrated for 100, 125 and 150 mm wafers.

Contamination control in a pulsed plasma doping tool

Pulsed plasma doping offers a number of compelling benefits for low energy implantation, such as throughput, simplicity and low risk to wafers. The compromise to plasma-based doping systems is the absence of mass selection and increased sensitivity to system contaminants. To quantify the level of contamination present, secondary ion mass spectroscopy (SIMS) measurements of boron and arsenic implantation for sub-keV energies up to 5 keV are presented. Preliminary data show the depth profile of contaminants is consistent with surface contamination from nonionized sputtered material. Initial results for particulate contamination measurements are also described.

Wafer Charge Control in the E1000 Ion Implanter

Wafer charging during high current ion implantation has been one of the major gating items preventing implanter users from utilizing the full benefit of very high beam current capabilities in todays high current ion implanters. Dramatic improvements in charging performance have been achieved recently in the Varian E1000 high current implanter through upgrades to its original electron flood system. The performance has been improved through the admittance of low ionization potential and slow diffusing gas into the Faraday assembly. In addition, a two-dimensional beam profile monitor has been developed to assist in controling peak current density. This paper will present the results of the charging tests with these upgrades and discuss briefly the theory behind the improvements.