Ion implant dose control
US6870170B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 4, 2004 |
| Grant date | Mar 22, 2005 |
| Priority date | — |
| Expiry date | Mar 4, 2024 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J2237/31703
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
This invention is concerned with the control of implanting ions into a substrate, such as doping semiconductor wafers. The ion beam is measured to ensure waters are implanted with the correct, uniform ion dose. The incident ion beam comprises ions and neutrals, yet detectors measure only ions. The ions/neutrals ratio varies with the ion implanter's chamber pressure that in turn is known to rise and fall when the ion beam is on and off the wafer respectively, according to a characteristic time constant. This invention provides methods of correcting measured ionic currents to account for neutrals using the time constant. Initially an assumed time constant is used that is later improved by measuring the ionic current after a delay sufficient to allow the chamber pressure to recover to its base value. The time constant may also be improved by removing any quadratic variation in already determined true beam current values.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.