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US 6,583,421 B2Granted
Charge measuring device with wide dynamic range
AssigneeDiamond Semiconductor Group, Inc.
InventorPhilip C. Harvey
Life of this patent
Estimating the term…
Abstract
A fast dosimeter for ion implantation and other systems that produce charges or current to be measured. When a charge accumulator reaches a predetermined charge, a fixed charge is removed to reduce the accumulated charge. A counter records each charge removal. Between removals, an analog-to-digital converter measures the accumulator charge. The outputs from the counter and the analog-to-digital converter provide a continually updated value for the total accumulated charge, and by differentiation, current with respect to time.
Claims24
A dosimeter for measuring charge accumulated in a charge gathering means comprising:
- A) a charge accumulator having an input connected to the charge gathering means and an output for producing a signal representative of accumulated charge,
- B) charge measuring means for measuring the magnitude of the accumulated charge at said charge accumulator output,
- C) charge altering means at said charge accumulator input for producing a fixed change in the charge of said charge accumulator during a single operation when the charge in said charge accumulator reaches a predetermined threshold, and
- D) counting means for counting the number of operations of said charge altering means whereby the count and indicated charge magnitude yield the total accumulated charge.
1 more element
A dosimeter for measuring charge accumulated in a charge gathering means comprising:
- A) a charge accumulator having an input connected to the charge gathering means and an output for producing a signal representative of accumulated charge, said charge accumulator including:
- i) an amplifier with an input and output,
- ii) a feed back capacitor for said amplifier for storing charge, and
- iii) a summing junction at said amplifier input for connection to the charge gathering device and to said charge removing means
- B) charge measuring means for measuring the magnitude of the accumulated charge at said charge accumulator output,
- C) charge removal means at said charge accumulator input for removing a fixed charge from said charge accumulator during a single operation when said charge magnitude reaches a predetermined threshold, said charge removal means including:
- i) a switched capacitive storage circuit for storing a fixed charge having charging and discharging modes of operation, and
- ii) a threshold circuit for shifting said switched capacitive storage circuit between the charging and discharging modes of operation whereby said switched capacitive storage circuit discharges the fixed charge from the input of said charge accumulator when the signal at said charge accumulator output exceeds the predetermined threshold value, and
- D) counting means for counting the number of operations of said fixed incremental charge means whereby the count and indicated charge magnitude correspond to the accumulated charge.
6 more elements
A dosimeter for measuring charge accumulated in a Faraday cup in ion implantation device comprising:
- A) a charge accumulator amplifier with an input and output having a feed back capacitor for storing charge and a summing junction at said amplifier input for connection to the Faraday cage,
- B) a charge measuring analog-to-digital converter connected to said charge accumulator amplifier output for generating a digital output,
- C) a switched capacitive storage circuit for storing a fixed charge connected to said charge accumulator amplifier input having charging and discharging modes of operation,
- D) a threshold circuit for shifting said switched capacitive storage circuit between the charging and discharging modes whereby said switched capacitive storage circuit discharges the fixed charge from the input of said charge accumulator amplifier when the signal at said charge accumulator amplifier output exceeds a predetermined threshold value, and
- E) a counter connected to said switched capacitive storage unit that changes its count each time said switched capacitive storage circuit discharges whereby the outputs from said charge measuring analog-to-digital converter and said counter yield accumulated charge.
2 more elements
A dosimeter for measuring the net charge accumulated in a charge gathering means comprising:
- A) a charge accumulator having an input connected to the charge gathering means and an output for producing a signal representative of accumulated charge,
- B) charge measuring means for measuring the magnitude of the accumulated charge at said charge accumulator output,
- C) first charge modifying means at said charge accumulator input for removing a fixed charge from said charge accumulator during a single operation when the charge in said charge accumulator exceeds a first predetermined threshold, and
- D) second charge modifying means at said charge accumulator input for adding the fixed charge from said charge accumulator during a single operation when the charge in said charge accumulator falls below a second predetermined threshold, and
- E) counting means for counting the number of operations of said first and second charge modifying means whereby the net count and indicated charge magnitude yield the total charge accumulated in said charge gathering means.
2 more elements
Dependencies are inferred from the claim text.