| 摘要 |
PURPOSE:To reduce the measurement error of the dose amount, and suppress the variation in the dose amount among batches by measuring the degree of vacuum near a beam line part or a beam-detecting Faraday cup, and performing correction operation on the beam current value on the basis of the measured value. CONSTITUTION:A vacuum gauge 6 is set to a Faraday part, and the measured value of a beam ampere meter 7 is corrected according to the measured value of the vacuum degree of the Faraday part. When neutral particles and ion beams with over two valences are produced due to the exchange of charges with the molecules of remaining gas, the equation of It=Im/(1-C.P) is satisfied. In the above equation, (It) represents the true amount of beams; (Im), the amount of beams measured by the beam ampere meter 7; (P), the degree of vacuum; and (C), a correction coefficient. Therefore, the true amount of beams, (It), can be known by performing operation according to both the beam current, (Im), measured by a Faraday cup and the degree of vacuum, (P), measured by the vacuum meter 6. |
