Charged-particle-beam mapping projection-optical systems and methods for adjusting same

In an inspection apparatus that includes a charged-particle-beam (CPB) optical system having a cathode lens and including an X-Y stage for holding an object, a method for adjusting an optical axis of the CPB optical system, the method comprising:

• guiding a charged particle beam from the object through the optical system along the optical axis to a detector;
• from an adjustment CPB source located on a surface of the X-Y stage, generating an adjustment charged particle beam that propagates from the adjustment CPB source to the detector and produces an image of the object at the detector;
• and
• determining a position of the X-Y stage using the adjustment charged particle beam to adjust the optical axis.

A method for aligning an inspection apparatus, comprising:

• using a first optical system, guiding a first energy beam from a specimen to a first detector along a first optical axis;
• using a second optical system, guiding a second energy beam from the specimen to a second detector along a second optical axis;
• obtaining an image of a pattern to measure a location of the specimen relative to the second optical axis and a distance of the specimen to the second optical axis:
• determining a baseline from the distance between the first and second optical axes;
• and
• using the baseline, aligning an evaluated area of the specimen to the first optical axis to align the specimen with respect to the first optical axis.

A charged-particle-beam (CPB) apparatus, comprising:

• an irradiation-optical system having a respective optical axis and being situated and configured for guiding a primary charged particle beam from a beam source to a surface of a specimen on a stage;
• a detection-optical system situated and configured for detecting a secondary beam of charged beam of charged from the surface and for producing an image of the surface, the detection-optical system and irradiation-optical system being situated in a vacuum environment;
• a beam deflector provided in at least one of the irradiation-optical system and detection-optical system;
• and
• an off-axis optical system having an optical axis situated at a predetermined distance from the axis of the irradiation-optical system, the off-axis optical system being configured to illuminate the specimen with an optical aligment beam passing from outside the vacuum environment through a window and through an objective lens situated in the vacuum environment so as to align the specimen with the axis of the irradiation-optical system.

In an apparatus including a specimen stage, a charged-particle-beam (CPB) optical system having a main optical axis, and an off-axis optical system having a respective optical axis, a method for measuring an off-axis distance in the apparatus, the method comprising:

• providing a first pattern on the specimen stage;
• obtaining a first image of the first pattern using the off-axis optical system;
• providing a second pattern at a known distance from the first pattern;
• obtaining a second image of the second pattern using the CPB optical system;
• and
• determining a distance between the main optical axis and the optical axis of the off-axis optical system based on the first and second images.

In an apparatus including a specimen stage, a charged-particle-beam (CPB) optical system having a main optical axis, and an off-axis optical system having a respective optical axis, a method for measuring an off-axis distance in the apparatus, the method comprising:

• providing a first pattern on the specimen stage;
• obtaining a first image of the first pattern using the off-axis optical system;
• using a stage-position-measuring device, measuring a first stage position when obtaining the first image;
• using the CPB optical system, obtaining a second image of a pattern on the specimen stage, the pattern being either the first pattern or a second pattern situated a known distance from the first pattern;
• using the stage-position-measuring device, measuring a second stage position when obtaining the second image;
• and
• determining a distance between the main optical axis and the optical axis of the off-axis optical system based on the first and second images and the respective first and second stage positions.

A method for evaluating a specimen with an image obtained using a charged particle beam, the method comprising:

• using an off-axis optical system, obtaining an image of a pattern provided on the specimen;
• while obtaining the image, measuring a position of a stage holding the specimen;
• reading or measuring a stage-position baseline;
• and
• calculating a target stage position from the obtained image, measured stage position, and baseline, and moving the stage toward the target stage position.

In an inspection apparatus including a stage for mounting a specimen for inspection, a charged-particle-beam (CPB) source for generating a charged particle beam from a surface of the specimen, a CPB detector for detecting the charged particle beam, and a deflector situated between the stage and the CPB detector, a method for adjusting an optical axis of the inspection apparatus, the method comprising:

• generating a charged particle beam from the CPB source so as to cause the charged particle beam to be generated from the surface of the specimen;
• obtaining a first image of the specimen by detecting the charged particle beam while not applying a voltage to the deflector;
• obtaining a second image of the specimen by detecting the charged particle beam while applying a voltage to the deflector;
• and
• setting the voltage applied to the deflector based on the first and second images, so as to adjust the optical axis.