Ion implanter for noncircular wafers
View Patent ↗Ion implanters are especially suited to meet process dose and energy demands associated with fabricating photovoltaic devices by ion implantation followed by cleaving.
1. An ion implanter configured to implant ions in semiconductor wafers, comprising:
a. a disk configured to rotate about an axis and bearing noncircular pads, each pad configured to support a noncircular semiconductor wafer; and
b. apparatus disposed to direct an ion beam, constituting a current of at least 5 mA of hydrogen or helium ions, at the disk, the apparatus comprising a mass analyzer having a resolving power less than ten,
wherein the implanter has no mass analyzer beside the mass analyzer.
2. The ion implanter of claim 1 wherein the pads and wafers are square.
3. The ion implanter of claim 1 wherein the pads and wafers are corner-clipped square.
4. The ion implanter of claim 1 wherein the pads have respective normals, and further comprising a control system configured to rotate the disk so that each normal makes a same constant angle with the ion beam.
5. The ion implanter of claim 1 wherein each of the pads has a diagonal coinciding with a radius of the disk.
6. The ion implanter of claim 1 wherein the pads are arranged in rows and columns.
7. The ion implanter of claim 1 wherein the pads are arranged in at least two concentric annuli around the axis.
8. The ion implanter of claim 1 further comprising a control system configured to rotate the disk about an axis and further to scan the disk cyclically so that the ion beam repeatedly traces a path over the disk, the path having turnaround points on the wafers.
9. The ion implanter of claim 1 wherein the ion beam constitutes a current of at least 20 mA.
10. The ion implanter of claim 1 wherein the ion beam constitutes a current of at least 50 mA.
11. The ion implanter of claim 1 wherein the mass analyzer has a maximum magnetic rigidity corresponding to selecting a singly-charged ion of mass less than 2 Daltons and energy no greater than 100 keV.
12. The ion implanter of claim 1 wherein the mass analyzer has a maximum magnetic rigidity corresponding to selecting a singly-charged ion of mass less than 5 Daltons and energy no greater than 100 keV.