Patent ID: 7939812

Claim:
An ion source assembly for ion implantation apparatus, comprising: a vacuum chamber; an arc chamber in said vacuum chamber, said arc chamber having a linear dimension and walls including a front wall extending along said linear dimension; a source of gas containing a species to be ionized in the ion source to provide ions required for implantation; at least one electrode in the arc chamber suitable, when electrically biased, to provide a source of electrons for ionizing said species; an ion extraction slit in said front wall aligned with said linear dimension, wherein said extraction slit is at least 100 mm in length; and a magnetic field device to provide a magnetic field along said linear dimension of the arc chamber to constrain electrons to spiral along said field within said chamber, said magnetic field having a flux density which has a non-uniformity less than 5% along said linear dimension over the length of said extraction slit.