Patent ID: 7358509

Claim:
An angle measurement apparatus used for an ion implanter, said ion implanter irradiating an ion beam onto a substrate in a vacuum chamber, said substrate being held by a holder whose angle with respect to the ion beam is variable, said angle measurement apparatus comprising: a first camera and a second camera which measure luminance distribution of beam plasma at two positions in a traveling direction of the ion beam, and respectively output image data corresponding to the measured luminance distribution, said beam plasma being produced when the ion beam collides with residual gas and emitting light; a linear light source arranged on the holder in a state that it is substantially in parallel with a substrate holding surface of the holder; a third camera which measures light emitted from the linear light source and outputs image data corresponding to the measured light; a first image data processor which processes the image data from the first camera and obtains a centroid of a first area of the luminance distribution of the beam plasma; a second image data processor which processes the image data from the second camera and obtains a centroid of a second area of the luminance distribution of the beam plasma; a third image data processor which processes the image data from the third camera and obtains a parallel line that is parallel to the linear light source; and a deviation angle computing unit for obtaining a difference between a measurement angle and a reference angle as a deviation angle, said measurement angle being formed by the parallel line and a line connecting the centroid of the first area and the centroid of the second area when the angle of the holder with respect to the ion beam is set to the reference angle.