Adjustment method of inspection apparatus focus position, and pattern inspection apparatus

A pattern inspection apparatus comprising:

• a stage configured to mount thereon an evaluation substrate on which a plurality of types of figure patterns have been formed;
• a drive mechanism configured to move a height position of the stage;
• an autofocus optical system configured to lead, while varying a height position of a pattern forming surface of the evaluation substrate by moving the height position of the stage, one of a light transmitted through the evaluation substrate and a light reflected from the evaluation substrate irradiated with an inspection light to a first light amount sensor and a second light amount sensor which measure, for each of the plurality of types of figure patterns, a light amount at a front focus position and a light amount at a back focus position of the one of the light transmitted through the evaluation substrate and the light reflected from the evaluation substrate;
• an autofocus signal calculation circuit configured to calculate an autofocus signal, for the each of the plurality of types of figure patterns and for each the height position of the pattern forming surface of the evaluation substrate, by using the light amount measured at the front focus position and the light amount measured at the back focus position;
• a specification circuit configured to specify a value of an autofocus signal for inspection such that a difference between values of autofocus signals of the plurality of types of figure patterns calculated at a same height position of the pattern forming surface of the evaluation substrate is one of equal to and less than a threshold value;
• an autofocus mechanism configured to adjust, in a state where an inspection substrate on which at least two types of figure patterns out of the plurality of types of figure patterns are formed is placed on the stage, a height position of a pattern forming surface of the inspection substrate, which may be changed with a horizontal direction movement of the stage, to a height position of the pattern forming surface corresponding to the value of the autofocus signal for inspection;
• a sensor configured to acquire, in a state where the height position of the pattern forming surface of the inspection substrate has been adjusted to the height position of the pattern forming surface corresponding to the value of the autofocus signal for inspection, an optical image of the inspection substrate by receiving one of a light transmitted through the inspection substrate and a light reflected from the inspection substrate irradiated with an inspection light;
• and
• an inspection optical system configured to lead the one of the light transmitted through the inspection substrate and the light reflected from the inspection substrate to the sensor.

A method for adjusting a focus position of an inspection apparatus, comprising:

• measuring, while varying a height position of a pattern forming surface of a substrate on which a plurality of types of figure patterns are formed, for each of the plurality of types of figure patterns, a light amount at a front focus position and a light amount at a back focus position of one of a light transmitted through the substrate and a light reflected from the substrate irradiated with an inspection light;
• calculating an autofocus signal, for the each of the plurality of types of figure patterns and for each the height position of the pattern forming surface of the substrate, by using the light amount measured at the front focus position and the light amount measured at the back focus position;
• specifying a value of an autofocus signal for inspection such that a difference between values of autofocus signals of the plurality of types of figure patterns calculated at a same height position of the pattern forming surface of the substrate is one of equal to and less than a threshold value;
• and
• acquiring, in a state where the substrate is placed on a stage, while adjusting the height position of the pattern forming surface of the substrate, which may be changed with a horizontal direction movement of the stage, to a height position of the pattern forming surface corresponding to the value of the autofocus signal for inspection, an optical image of the substrate by receiving by a sensor, through an inspection optical system, the one of the light transmitted through the substrate and the light reflected from the substrate irradiated with an inspection light.