1. Technical Field
This invention relates to an ion implanting apparatus for performing ion implantation by irradiating a substrate such as a semiconductor substrate, a substrate for a flat panel, etc. (in other words, workpiece or a processed body. The same goes for the following description). More particularly, this invention relates to an ion implanting apparatus which is appropriately adaptable to up-sizing of the substrate (in other words, large-scaling. The same goes for the following description). Incidentally, the ion implanting apparatus defined herein includes an apparatus called an ion doping apparatus.
2. Background Art
An example of ion implanting apparatus capable of irradiating a substrate with an ion beam having a large width and parallelized is disclosed in JP-A-2000-505234 (page 14, line 14 to page 15, line 15, FIG. 5). This ion implanting apparatus has a structure in which a unidirectionally diverging fan-shaped ion beam extracted from a small-sized ion source is bent in a plane in parallel to the fan face through a mass separating magnet serving as a beam parallelizing magnet so that desired ion species thereof are selected (mass-separated) and parallerized to form an ion beam having a large width and parallelized, and the substrate is irradiated with the ion beam.
In the ion implanting apparatus, the mass resolution of the mass separating magnet is high in the outer periphery of an ion-beam deflecting region and low in the inner periphery thereof. This is due to the fact that since the ion beam is parallelized while being bent, the deflecting angle is larger on the outer periphery to increase the mass resolution. However, with an increase in the mass resolution, the ion species are strictly separated. The amount of the ion species obtained is therefore decreased. Thus, the beam current density of the ion beam derived from the mass separating magnet results in a non-uniform distribution that it is low when the ion-beam has passed the outer periphery and high when the ion-beam passed the inner periphery. Namely, the uniformity of the beam current density distribution in a width direction of the ion beam is deteriorated.
In the ion-implanting apparatus disclosed in JP-A-2000-505234 (page 14, line 14 to page 15, line 15, FIG. 5), it can be proposed to correct the non-uniformity of the beam current density distribution due to the above reason by local deflection of the ion beam by the use of a multi-polar ion lens provided on the upstream side of the mass-separating magnet (for example, the ion beam is deflected toward the region having a lower current density to increase the current density on the region). However, the non-uniformity of the beam current density distribution due to the above fact is so great that correction by the multi-polar ion lens has a limit.
Further, if the non-uniformity of the beam current density distribution is corrected by largely deflecting the ion beam by the multi-polar ion lens, owing to this deflection, another problem of deteriorating the parallelism in the width direction of the ion beam occurs.
The above problem becomes more serious when the width of the ion beam derived from the mass separating magnet is increased in order to dealing with the large-scaling the substrate (for example, the substrate having a narrow side width of about 600 mm or more).
Further, in the above conventional technique of increasing the width of the ion beam by the use of divergence of the ion beam derived from the ion source, the beam current density decreases with an increase in the width of the ion beam. So dealing with the large-scaling of the substrate leads to a reduction in the processing speed per a single substrate.