High quality high current ion beam generation and transport systems including plasma-based space charge neutraliser

This thesis discusses the development of an ion beam generation and transport system for the purpose of high current ion implantation and presents a method toachieve high quality beam generation and high transport efficiency. An advanced method of achieving ideal space charge neutralization of an ion beam as well ascharge neutralization of implanted targets has also been developed and presented. This study was carried out in five main categories as described below.1. Beam optics: The optical properties of the ion beam have to be well controlled through various beam transport devices. Beam transfer matrix calculation and Poisson's equation solver were used to determine beam optics.2. Plasma generation: The ion beam is extracted from a plasma generated in the ion source. Therefore, thequality of ion beams depends largely on the characteristics of the source plasma. Plasma diagnostic tools were used to understand the desired plasma conditions.3. Space charge neutralisation: Space charge neutralisation is essential to transport high perveance beams because a beam without neutralisation develops a high electric potential in itself that would scatter beam ions away. A plasma based charge neutraliser "Plasma Flood System" was developed to maintain space charge neutrality during implantation.4. Low energy beam extraction and transport: Beam extraction and transport become difficult at lower energy due to growth of emittance and space charge. Beam divergence had to be minimized by tight opticalcontrol. 5. Microwave plasma sources as ultimate ion source: A microwave source was developed to obtain high current, ultra clean ion beams and long source life. The characteristics of microwave plasmas differ significantly from whose generated by other methods such as DC excitation. The source achieved the highest recorded beam currents for various species.All the technology and the methods described above were combined to develop a state-of-the-art high current ion implanter that has achieved world leading beamperformance.

Level dc:type.qualificationlevel

Doctoral (Level 8)

Year dc:date.issued

2003

Author dc:creator

• Ito, H

Language dc:language

en

Identifier

oai:salford-repository.worktribe.com:1389654

OAI identifier oai:identifier

oai:salford-repository.worktribe.com:1389654