Focusing apparatus, focusing method, and pattern inspection method

A focusing method comprising:

• illuminating a substrate, on which a pattern is formed, with a reflection illumination light by using a reflection illumination optical system;
• receiving a pattern image of the substrate by a time delay integration sensor (TDI sensor) through an image forming optical system which forms the pattern image of the substrate;
• performing gray scale value equalization by using a gray scale value output by the TDI sensor which received the pattern image of the substrate generated by irradiating the substrate with the reflection illumination light;
• receiving the pattern image of the substrate by the TDI sensor generated by irradiating the substrate with the reflection illumination light having passed through a first reticle and a second reticle, in a state where the gray scale value equalization has been performed, by using the first and second reticles, the first reticle being arranged at a front side of a conjugate position of the TDI sensor facing a surface of the substrate, along an optical axis direction, in an optical path of the reflection illumination optical system, being configured to be irradiated with the reflection illumination light, and having thereon a light-shielding pattern whose end part is parallel with a direction of time integration of the TDI sensor, and a transmission pattern whose occupancy rate in an illumination region is larger than that of the light-shielding pattern, and the second reticle, being arranged at a back side of the conjugate position of the TDI sensor facing the surface of the substrate, to be equivalently opposite to the first reticle, along the optical axis direction, in the optical path of the reflection illumination optical system, being configured to be irradiated with the reflection illumination light, and having thereon a light-shielding pattern and a transmission pattern which are same shapes as those of the first reticle and whose arrangement direction is opposite to that of the first reticle;
• calculating, in the state where the gray scale value equalization has been performed, a distance change/move amount of a relative distance, for focusing the pattern image of the substrate, between the substrate and the conjugate position of the TDI sensor by using a first derivative value of a gray scale value output by the TDI sensor which received the pattern image of the substrate generated by irradiating the substrate with the reflection illumination light having passed through the first and second reticles;
• and
• changing/moving the relative distance between the substrate and the conjugate position of the TDI sensor by using the distance change/move amount.

A pattern inspection method comprising:

• illuminating a substrate, on which an alignment pattern and a circuit pattern are formed, with a reflection illumination light by using a reflection illumination optical system;
• receiving an alignment pattern image of the substrate by a time delay integration sensor (TDI sensor) through an image forming optical system which forms a pattern image of the substrate;
• performing gray scale value equalization by adjusting a gain and offset by using a gray scale value output by the TDI sensor which received the alignment pattern image of the substrate generated by irradiating the substrate with the reflection illumination light;
• arranging a first reticle, where a light-shielding pattern whose end part is parallel with a direction of time integration of the TDI sensor, and a transmission pattern whose occupancy rate in an illumination region is larger than that of the light-shielding pattern are formed, at a front side of a conjugate position of the TDI sensor facing a surface of the substrate, along an optical axis direction, in an optical path of the reflection illumination optical system, and also arranging a second reticle, where alight-shielding pattern and a transmission pattern which are same shapes as those of the first reticle and whose arrangement direction is opposite to that of the first reticle, at a back side of the conjugate position of the TDI sensor facing the surface of the substrate, to be equivalently opposite to the first reticle, along the optical axis direction, in the optical path of the reflection illumination optical system;
• measuring, in a state where the gray scale value equalization has been performed by adjusting the gain and offset, a height position of the substrate by using a first derivative value of a gray scale value output by the TDI sensor which received the alignment pattern image of the substrate generated by irradiating the substrate with the reflection illumination light having passed through the first and second reticles;
• acquiring a height position distribution of the substrate, based on the height position of the substrate;
• and
• inspecting the circuit pattern formed on the substrate while changing the height position of the substrate, based on the height position distribution.