Charged particle beam writing apparatus, charged particle beam writing method, and phase difference plate adjustment method

A charged particle beam writing apparatus comprising:

• a writer radiating a charged particle beam to a sample to write a pattern, the writer including a writing chamber in which a movable stage for placing the sample is internally installed;
• a laser source outputting a laser beam with a first frequency and a second frequency;
• a length measurer measuring a position of the stage using the laser beam with the first frequency and the second frequency;
• a wall surface displacement measurer measuring a wall surface displacement of the writing chamber using the laser beam with the first frequency and the second frequency;
• and
• a writing controller controlling the writer,
• wherein the length measurer includes a first laser interferometer provided in a wall surface of the writing chamber, and detects a first synthetic beam and outputs a first beat signal, the first synthetic beam being obtained by synthesizing a laser beam with the first frequency which has traveled back and forth between the first laser interferometer and the stage, and a laser beam with the second frequency reflected in the first laser interferometer,
• the wall surface displacement measurer includes a second laser interferometer provided in the wall surface of the writing chamber, and detects a second synthetic beam and outputs a second beat signal, the second synthetic beam being obtained by synthesizing a laser beam with the first frequency which has traveled back and forth between the second laser interferometer and a fixed mirror fixed at a predetermined position in the writing chamber, and a laser beam with the second frequency reflected in the second laser interferometer, and
• the writing controller calculates the position of the stage based on a difference between the first beat signal and the second beat signal.