Method and apparatus for extracting ions from an ion source for use in ion implantation

Abstract

Thermal control is provided for an extraction electrode of an ion-beam producing system that prevents formation of deposits and unstable operation and enables use with ions produced from condensable vapors and with ion sources capable of cold and hot operation. Electrical heating of the extraction electrode is employed for extracting decaborane or octadecaborane ions. Active cooling during use with a hot ion source prevents electrode destruction, permitting the extraction electrode to be of heat-conductive and fluorine-resistant aluminum composition. The service lifetime of the system is enhanced by provisions for in-situ etch cleaning of the ion source and extraction electrode, using reactive halogen gases, and by having features that extend the service duration between cleanings, including accurate vapor flow control and accurate focusing of the ion beam optics. A remote plasma source delivers F or Cl ions to the de-energized ion source for the purpose of cleaning deposits in the ion source and the extraction electrode. These techniques enable long equipment uptime when running condensable feed gases such as sublimated vapors, and are particularly applicable for use with so-called cold ion sources and universal ion sources. Methods and apparatus are described which enable long equipment uptime when decaborane and octadecaborane are used as feed materials, as well as when vaporized elemental arsenic and phosphorus are used, and which serve to enhance beam stability during ion implantation.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation-in part of International Patent Application No. PCT / US2004 / 041525, filed on Dec. 9, 2004, which, in turn, claims priority to and claims the benefit of U.S. Patent Application No. 60 / 529,343, filed on Dec. 12, 2003.FIELD OF THE INVENTION [0002] The present invention relates to producing ion beams in which one or more gaseous or vaporized feed materials is ionized in an ion source from which the ions are extracted by an extraction electrode. It also relates to a method and apparatus for operating an ion source and extraction electrode to produce an ion beam for ion implantation of semiconductor substrates and substrates for flat panel displays. In particular the invention concerns extension of the productive time (i.e. the “uptime”) of systems that produce ion beams and to maintaining stable ion-extraction conditions during the productive time. BACKGROUND [0003] Ion beams are produced from ions extracted...

AI Technical Summary

Benefits of technology

[0015] Objects of this invention are to provide a method and apparatus for producing ions beams without disturbance in the stability of the ion beam by electric discharges at the extraction electrode and to provide a method and apparatus for producing an ion beam which increases service lifetime and reduces equipment down time.

Problems solved by technology

The precise qualities of the ion beam can be severely affected by condensation and deposit of the feed material or of its decomposition products on surfaces of the ion beam-producing system, and in particular surfaces that affect ionization, ion extraction and acceleration.

Such a condition is called “cross-contamination” and is undesirable.

A serious contamination effect occurs when feed materials accumulate within the ion source so that they interfere with the successful operation of the source.

Such a condition invariably has called for removal of the ion source and the extraction electrode for cleaning or replacement, resulting in an extended “down” time of the entire ion implantation system, and consequent loss of productivity.

With other feed materials, however, detrimental deposits have formed in hot ion sources.

Cold ion sources suffer more from the deposition of feed materials than do hot sources.

The use of these gases and vapors in cold ion sources has resulted in significant materials deposition and has required the ion source to be removed and cleaned, sometimes frequently.

These ion sources suffer from cross-contamination (between N— and P-type dopants) and also from particle formation due to the presence of deposits.

When transported to the substrate, particles negatively impact yield.

Cross-contamination effects have historically forced FPD manufacturers to use dedicated ion implanters, one for N-type ions, and one for P-type ions, which has severely affected cost of ownership.

Boron hydrides such as decaborane and octadecaborane present a severe deposition problem when used to produce ion beams, due to their propensity for readily dissociating within the ion source.

Eventually, depending on the design of the ion source, the buildup of condensed material interferes with the operation of the source and necessitates removal and cleaning of the ion source.

Contamination of the extraction electrode has also been a problem when using these materials.

Such instabilities affect the precision quality of the ion beam and can contribute to the creation of contaminating particles.

Images