Method and apparatus for extending equipment uptime in ion implantation

Abstract

The service lifetime of an ion source is enhanced or prolonged by the source having provisions for in-situ etch cleaning of the ion source and of an extraction electrode, using reactive halogen gases, and by having features that extend the service duration between cleanings. The latter include accurate vapor flow control, accurate focusing of the ion beam optics, and thermal control of the extraction electrode that prevents formation of deposits or prevents electrode destruction. An apparatus comprised of an ion source for generating dopant ions for semiconductor wafer processing is coupled to a remote plasma source which delivers F or Cl ions to the first ion source for the purpose of cleaning deposits in the first ion source and the extraction electrode. These methods and apparatus enable long equipment uptime when running condensable feed gases such as sublimated vapor sources, and are particularly applicable for use with so-called cold 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

FIELD OF THE INVENTION [0001] The present invention relates to producing ion beams in which one or more gaseous or vaporized feed materials is ionized in an ion source. It also relates to a method and apparatus for operating an ion source 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. BACKGROUND [0002] Ion beams are produced from ions extracted from an ion source. An ion source typically employs an ionization chamber connected to a high voltage power supply. The ionization chamber is associated with a source of ionizing energy, such as an arc discharge, energetic electrons from an electron-emitting cathode, or a radio frequency or microwave antenna, for example. A source of desired ion species is introduced into the ionization chamber as a feed material in gaseous or vaporized form where it is ex...

AI Technical Summary

Benefits of technology

[0014] It is an object of this invention to provide a method and apparatus for producing an ion beam which increases service lifetime and reduces equipment down time.

[0015] The invention features in-situ cleaning procedures and apparatus for an ion source and associated extraction electrodes and similar components of the ion-beam producing system, which periodically chemically remove deposits, increasing service lifetime and performance, without the need to disassemble the system.

[0016] The invention also features an actively heated ion extraction electrode which consists of a material which reduces the frequency and occurrence of electrical discharges, preferably this material being a metal.

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.

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