Charged particle beam writing apparatus and charged particle beam writing method

A charged particle beam writing method for writing a pattern on a substrate by adjusting a charged particle beam using a single mark on a stage and irradiating the substrate with the charged particle beam, the substrate being a writing target placed on the stage, the charged particle beam writing method comprising:

• detecting a surface height of the single mark;
• detecting an irradiation position of the charged particle beam on a surface of the single mark by irradiation with the charged particle beam focused at a surface height of the single mark;
• calculating an amount of drift of the charged particle beam on the surface of the single mark using the detected irradiation position;
• calculating a correction amount for correcting a shift in irradiation position caused by a drift on a surface of the substrate, by the amount of drift on the surface of the single mark;
• and
• correcting the irradiation position of the charged particle beam by using the calculated correction amount,
• wherein before irradiating the single mark, the charged particle beam is focused onto the surface of the single mark by using an objective lens.