Patent EP-4166933-A1 (EP)
Inventor: MASUMURA SHIGEKI
IPC: G01N21/84
Filed: 2020-06-15
Abstract: Technical Problem 
     In the case where object light returned from an object surface to be inspected has a low content of a direct light component that corresponds to regular reflection and regular transmission of irradiation light, and contrast information thereof is therefore acquired by mainly observing a scattered light component, if irradiation conditions, such as inclines of optical axes of irradiation light, at respective points on the object surface cannot be kept uniform, it is difficult to quantitatively reflect incline directions and incline angles of minute areas in the vicinity of respective points on the object surface in a variation in optical attributes, and in the contrast, of the scattered light. 
     On the other hand, in the case where object light returned from an object surface to be inspected has a high content of the direct light component, and contrast information thereof is acquired by mainly observing the direct light component, 
when surface characteristics of the object surface include, for example, a three-dimensional shape containing a relatively large change, if an incline of a minute surface constituting the object surface is larger than or equal to a certain angle, the optical axis of direct light that is regular reflection of irradiation light, of object light returned from the object surface, is significantly inclined and thus located outside an observation solid angle formed by an observation optical system from above the object, and therefore, the observation optical system cannot capture direct light from that inclined surface, which means that gray level information of that portion cannot be obtained from the direct light returned from the object, and it is difficult to continuously and quantitatively obtain the surface profile of the object surface. 
     Solution to Problem 
     The present invention was made in view of the above-described problems, and it is an object thereof to provide an inspection and measurement system and an inspection and measurement method with which, 
in an observation area of an object to be inspected, an object surface is irradiated with irradiation light capable of forming identical irradiation solid angles at respective points on the object surface, and 
when mainly observing a scattered light component, of object light returned from the object surface, other than direct light corresponding to regular reflection or regular transmission of the irradiation light, and acquiring a surface profile of the object surface based on the thus obtained contrast information, inclines of minute surfaces in the vicinity of the respective points on the object surface can be quantitatively reflected as a variation in optical attributes, and in the contrast information, of the scattered light component, or 
when mainly obtaining contrast information generated by a variation in inclusive relations between solid angles formed by the direct light and observation solid angles formed by an observation optical system for observing the direct light, and thereby acquiring a surface profile of the object surface, a relative relation of three-dimensional shape information such as height, incline, and incline direction, for example, can be acquired with regard to a surface profile of a region that is adjacent to a region in which an incline of a minute surface in the vicinity of a respective point on the object surface is larger than or equal to 1/2 of the sum of half plane angles of the irradiation solid angle and the observation solid angle at that point, and the observation optical system cannot continuously obtain gray level information based on the direct light returned from the object surface. 
     That is to say, the present invention was made based on the following new idea: 
when observing scattered light of object light returned from the inspection object when irradiated with irradiation light, irradiation solid angles of the irradiation light are formed such that the three-dimensional shape of an object surface can be acquired by causing illuminance on minute surfaces in the vicinity of respective points on the object surface to have the same illuminance distribution if the minute surfaces have the same incline direction and the same incline angle and by quantitatively varying optical attributes and contrast of the scattered light component of object light returned from minute surfaces having different incline directions and incline angles, according to the variation in incline direction and incline angle of the minute surfaces, or 
when observing direct light of object light returned from the inspection object, with attention being paid to the fact that, with respect to a discontinuous region in which the 3D shape of the object surface contains a large change and inclines of minute surfaces in the vicinity of respective points on the object surface cannot be continuously acquired as contrast information of object light returned from the respective points, there is a specific region in which irradiation solid angles of the irradiation light incident on respective points on the object surface in the vicinity of the discontinuous region are not reflected in solid angles of direct light corresponding to regularly reflected light of object light returned from those points, and with attention being also paid to a variation in the solid angles of the direct light relative to the irradiation solid angles and a variation in object light from the discontinuous region, the three-dimensional shape of the discontinuous region can be acquired based on contrast information of the object light.