Phase shift amount measurement apparatus and transmittance measurement apparatus

A phase shift amount measurement method for measuring a phase shift amount which is a phase difference between light transmitted through a phase shift portion of a phase shift mask and light transmitted through a non-phase shift portion, said phase shift amount measurement method, comprising the steps of;

• projecting an illumination beam toward the phase shift mask to be inspected,
• forming a laterally offset interference image of a mask pattern of the phase shift mask,
• capturing the formed laterally offset interference image by a two-dimensional imaging device having a plurality of light receiving elements,
• phase modulating the laterally offset interference image over one period to produce phase modulated data,
• selecting first and second measuring areas including a plurality of light receiving elements which form corresponding pattern images, respectively,
• processing the phase modulation data outputted from the light receiving elements included in the first and second measuring areas to output phase difference information for each light receiving element, and
• calculating the phase shift amount of the mask pattern for each light receiving element of the two-dimensional imaging device based on the phase difference information.

A transmittance measurement apparatus for measuring the transmittance of a light shielding pattern formed on a photo-mask, said transmittance measurement apparatus comprising:

• an illumination light source projecting illumination light toward a mask pattern of the photo-mask,
• a shearing interferometer receiving the light emitted from the mask pattern and forming a laterally offset interference image of the mask pattern,
• a two-dimensional imaging device having a plurality of light receiving elements and capturing the laterally offset interference image of the mask pattern,
• a focusing optical system for focusing the laterally offset interference image formed by the shearing interferometer on the two-dimensional imaging device,
• a phase modulating device for modulating the phase of said laterally offset interference image over one period, and
• a signal processing device for receiving output signals of light receiving elements output from said two-dimensional imaging device, calculating an amplitude of phase modulation data of light receiving elements included in a first measurement area in which the image of the light shielding pattern of the captured laterally offset interference image is formed and an amplitude of phase modulation data of light receiving elements included in a second measurement area in which a light shielding pattern is not formed, and calculating the transmittance of the light shielding pattern based on a ratio of amplitudes of phase modulation data of the first measurement area and the second measurement area and a ratio of numbers of light receiving elements included in the measurement areas.

A transmittance measurement method for measuring a transmittance of a light shielding pattern formed on a photo-mask, said transmittance measurement method comprising the steps of;

• projecting an illumination beam toward the photo-mask to be inspected,
• forming a laterally offset interference image of a mask pattern of the photo-mask,
• capturing the laterally offset interference image by a two-dimensional imaging device having a plurality of light receiving elements,
• phase modulating said laterally offset interference image over one period,
• defining a first measuring area included in the image of the light shielding pattern and a second measuring area where a light shielding pattern is not formed in the laterally offset interference image,
• calculating an amplitude of phase modulation data of light receiving elements included in the first measuring area and an amplitude of phase modulation data of light receiving elements included in the second measuring area in which a light shielding pattern is not formed, and
• calculating a transmittance of the light shielding pattern based on a ratio of the amplitude of the first measurement area and the amplitude of the second measurement area and a ratio of numbers of light receiving elements included in the measurement areas.