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US 6,297,510 B1Granted
Ion implant dose control
AssigneeApplied Materials, Inc.
InventorMarvin Farley
Life of this patent
Estimating the term…
Abstract
The true beam current corrected for neutrals in the beam impinging on the wafer during processing, is calculated by taking repeated measurements of the beam current during periods when the beam is clear of the wafer during a process. During such periods of multiple beam current measurements, the residual gas pressure declines in accordance with a pump down constant which is also determined. A quadratic expression relating measured beam current and time can then be solved for a factor giving a value for the corrected beam current. A corrected beam current is used to control the dosimetry of the apparatus to ensure the correct dose is uniformly applied to the surface of a wafer.
Claims17
An ion implanter having
- a vacuum chamber,
- a substrate holder in the vacuum chamber for supporting a target substrate,
- an ion beam generator for generating a beam of ions of a species to be implanted in the target substrate,
- a scanning apparatus for effecting a relative scanning movement of the ion beam across the target substrate,
- a vacuum pump for operating during implantation to pump residual gas from the vacuum chamber,
- a residual gas pressure detector producing a pressure signal indicative of changes in the residual gas pressure in the chamber,
- the scanning apparatus being arranged to produce during an implant repeated scans of the beam over the target substrate separated by periods when the beam does not impinge on the target substrate, whereby residual gas pressure in said chamber rises during each of said scans due to outgassing from the target substrate and falls during said separating periods due to pumping by said vacuum pump,
- an ion current detector providing multiple time spaced measurements of the ionic current in the ion beam at the target substrate during each of a plurality of the said separating periods, and
- a processor receiving said multiple measurements and data derived from said pressure signal indicating the changes in the residual gas pressure, and calculating therefrom a corrected value for total beam current representing the rate of delivery in the beam of particles of the species to be implanted.
6 more elements
A method of implanting a selected species of ion into a target substrate, the method comprising
- supporting the target substrate on a holder in a vacuum chamber,
- creating a vacuum within the vacuum chamber
- generating a beam of ions of the selected species to be implanted,
- pumping residual gas from the vacuum chamber during implantation of the ions into the substrate,
- effecting a repeated relative scanning movement of the ion beam across the target substrate, with repeated relative scanning movements of the beam over the target substrate being separated by periods when the beam does not impinge on the target substrate, whereby residual gas pressure in said vacuum chamber rises during each of said scans due to outgassing from the target substrate and falls during said separating periods due to said pumping,
- producing a pressure signal indicative of changes in the residual pressure in the chamber,
- effecting multiple time spaced measurements of the ionic current in the ion beam at the target substrate during each of a plurality of said separating periods, and
- calculating, from said multiple measurements and data derived from said pressure signal indicating the changes in the residual gas pressure, a corrected value for total beam current representing the rate of delivery in the beam of particles of the species to be implanted.
5 more elements
Apparatus of implanting a selected species of ion into a target substrate, comprising
- means for supporting the target substrate on a holder in a vacuum chamber,
- means for creating a vacuum within the vacuum chamber
- means for generating a beam of ions of the selected species to be implanted,
- means for pumping residual gas from the vacuum chamber during implantation of the ions into the substrate,
- means for effecting a repeated relative scanning movement of the ion beam across the target substrate, with repeated relative scanning movements of the beam over the target substrate being separated by periods when the beam does not impinge on the target substrate, whereby residual gas pressure in said vacuum chamber rises during each of said scans due to outgassing from the target substrate and falls during said separating periods due to said pumping,
- means for producing a pressure signal indicative of changes in the residual pressure in the chamber,
- means for effecting multiple time spaced measurements of the ionic current in the ion beam at the target substrate during each of a plurality of said separating periods, and
- means for calculating, from said multiple measurements and data derived from said pressure signal indicating the changes in the residual gas pressure, a corrected value for total beam current representing the rate of delivery in the beam of particles of the species to be implanted.
5 more elements
Dose monitoring apparatus for an ion implanter of the type comprising
- a vacuum chamber,
- a substrate holder in the vacuum chamber for supporting a target substrate,
- an ion beam generator for generating a beam of ions of a species to be implanted in the target substrate,
- a scanning apparatus for effecting a relative scanning movement of the ion beam across the target substrate,
- a vacuum pump for operating during implantation to pump residual gas from the vacuum chamber,
- a residual gas pressure detector producing a pressure signal indicative of changes in the residual gas pressure in the chamber,
- the scanning apparatus being arranged to produce during an implant repeated scans of the beam over the target substrate separated by periods when the beam does not impinge on the target substrate, whereby residual gas pressure in said chamber rises during each of said scans due to outgassing from the target substrate and falls during said separating periods due to pumping by said vacuum pump,
- and an ion current detector capable of providing multiple time spaced indications of the ionic current in the ion beam at the target substrate during each of a plurality of the said separating periods,
- the dose monitoring apparatus comprising a processor arranged to receive said pressure signal and said ionic current indications, to determine ionic current measurement values from said indications, to record the determined measurement values and the timing of the respective measurements during each of said plurality of said separating periods,
- and to calculate from said recorded values in each said separating period, together with data derived from said pressure signal, a respective corrected value for the total beam current representing the rate of delivery in the beam of particles of the species to be implanted.
7 more elements
A computer readable storage medium carrying instructions for controlling dose monitoring apparatus for an ion implanter of the type comprising
- a vacuum chamber,
- a substrate holder in the vacuum chamber for supporting a target substrate,
- an ion beam generator for generating a beam of ions of a species to be implanted in the target substrate,
- a scanning apparatus for effecting a relative scanning movement of the ion beam across the target substrate,
- a vacuum pump for operating during implantation to pump residual gas from the vacuum chamber,
- a residual gas pressure detector producing a pressure signal indicative of changes in the residual gas pressure in the chamber,
- the scanning apparatus being arranged to produce during an implant repeated scans of the beam over the target substrate separated by periods when the beam does not impinge on the target substrate, whereby residual gas pressure in said chamber rises during each of said scans due to outgassing from the target substrate and falls during said separating periods due to pumping by said vacuum pump,
- and an ion current detector capable of providing multiple time spaced indications of the ionic current in the ion beam at the target substrate during each of a plurality of the said separating periods,
- the dose monitoring apparatus including computer processing apparatus having a reader for reading the instructions on the storage medium, wherein said instructions are effective to control said computer processing apparatus of said dose monitoring apparatus to receive said pressure signal and said ionic current indications, to determine ionic current measurement values from said indications, to record the determined measurement values and the timing of the respective measurements during each of said plurality of said separating periods,
- and to calculate from said recorded values in each said separating period, together with data derived from said pressure signal, a respective corrected value for the total beam current representing the rate of delivery in the beam of particles of the species to be implanted.
7 more elements
Dependencies are inferred from the claim text.