Patent ID: 7643157

Claim:
A phase shift amount measurement apparatus for measuring a phase shift amount of a phase shift mask which is a phase difference between light passing through a phase shift portion of a phase shift mask and light passing through a non-phase shift portion, said phase shift amount measurement apparatus comprising: an illumination light source projecting illumination light toward a mask pattern of the phase shift mask including the phase shift portion and the non-phase shift portion, a shearing interferometer receiving the light emitted from the mask pattern and forming a laterally offset interference image of the mask pattern including two interference pattern images of the mask pattern which are formed by the light passing through the phase shift portion and the light passing through the non-phase shift portion and correspond with each other, a device for modulating a phase of said laterally offset interference image which includes said two interference pattern images over one period, a two-dimensional imaging device having a plurality of light receiving elements and which simultaneously captures said two interference pattern images included in the laterally offset interference image of the mask pattern, wherein said plurality of light receiving elements which simultaneously capture said two interference pattern images form first and second pixel areas, a focusing optical system for focusing the laterally offset interference image formed by the shearing interferometer on the two-dimensional imaging device; and a signal processing device for receiving output signals from the light receiving elements of the first and second pixel areas, calculating phase differences between the two interference pattern images based on phase modulation data over one period outputted from the plurality of light receiving elements capturing said two interference pattern images, and calculating the phase shift amount of the phase shift mask pattern for each light receiving element of the first and second pixel areas based on the calculated phase differences between the two interference pattern images, wherein said signal processing device removes any pixels producing a peculiar amplitude value from measured amplitude values of said light receiving elements and calculates the phase shift amount by use of the output signals from the remaining light receiving elements.