Charged particle beam axial alignment device, charged particle beam irradiation device and charged particle beam axial alignment method

A charged particle beam irradiation device comprising:

• a charged particle source that produces a charged particle beam;
• an objective lens that converges the charged particle beam produced by the charged particle source by a magnetic field and irradiates a sample with the charged particle beam;
• a scanner that two-dimensionally scans the charged particle beam with which the sample is irradiated through the objective lens on a surface of the sample;
• a deflector that deflects the charged particle beam produced by the charged particle source to adjust a positional relationship between an axis of the charged particle beam and an optical axis of the objective lens,
• a detector that detects charged particles produced from the sample due to scanning of the charged particle beam on the surface of the sample;
• and
• a charged particle beam axial alignment device that aligns the axis of the charged particle beam with the optical axis of the objective lens, wherein
• the charged particle beam axial alignment device includes
• a setter that sets magnetic field strength of the objective lens to first strength or second strength,
• a rotation amount difference specifier that specifies a difference in rotation amount of the charged particle beam between the case where the magnetic field strength is set to the first strength and the case where the magnetic field strength is set to the second strength based on a difference in strength between the first strength and the second strength,
• a scanning controller that controls the scanner such that rotation for canceling the rotation amount difference specified by the rotation amount difference specifier is supplied to the charged particle beam, when the magnetic field strength is set to the second strength,
• a producer that produces a first scanned image based on charged particles detected by the detector when the magnetic field strength is set to the first strength, and produces a second scanned image based on charged particles detected by the detector when the magnetic field strength is set to the second strength,
• a positional relationship specifier that specifies a relative positional relationship between the first scanned image and the second scanned image, and
• a deflection controller that controls the deflector based on the positional relationship specified by the positional relationship specifier such that a position of the first scanned image and a position of the second scanned image coincide with each other.

A charged particle beam axial alignment method for converging a charged particle beam by a magnetic field of an objective lens, irradiating a sample with the charged particle beam, allowing a scanner to two-dimensionally scan the charged particle beam on a surface of the sample, deflecting the charged particle beam by a deflector, and aligning an axis of the charged particle beam with an optical axis of the objective lens in a charged particle beam irradiation device that can adjust a positional relationship between the axis of the charged particle beam and the optical axis of the objective lens, including:

• setting magnetic field strength of the objective lens to first strength;
• producing a first scanned image based on charged particles produced from the sample when the magnetic field strength is set to the first strength;
• setting the magnetic field strength of the objective lens to second strength;
• specifying a difference in rotation amount of the charged particle beam between the case where the magnetic field strength is set to the first strength and the case where the magnetic field strength is set to the second strength as a rotation amount difference based on a difference in strength between the first strength and the second strength;
• controlling the scanner such that rotation for canceling the specified rotation amount difference is supplied to the charged particle beam, when the magnetic field strength is set to the second strength;
• producing a second scanned image based on charged particles produced from the sample when the magnetic field strength is set to the second strength;
• specifying a relative positional relationship between the first scanned image and the second scanned image;
• and
• controlling the deflector based on the specified positional relationship such that a position of the first scanned image and a position of the second scanned image coincide with each other.