Metrology Apparatus and a Method of Determining a Characteristic of Interest

Abstract

A computer program product causes a processor to execute a process of causing an optical system to illuminate at least one structure on a substrate that comprises first repetitive features at a first pitch in a first layer and second repetitive features at a second pitch in a second layer, the first repetitive features at least partially overlapping with the second repetitive features. The first pitch is different from the second pitch. The processor causes the optical system to receive radiation scattered by the at least one structure and transmit a portion of the received scattered radiation to a sensor arranged in an image plane of the optical system or in a plane conjugate with the image plane for detecting the received scattered radiation and configured to detect a characteristic of radiation impinging on the sensor. The processor then determines a characteristic of interest of the structure.

1 . A computer program product stored on a non-transitory computer readable medium and comprising a set of instructions that, when executed, cause a processor to execute processes of:
 causing an optical system to illuminate, using a radiation beam from a radiation source, at least one structure on a substrate, the at least one structure comprising first repetitive features at a first pitch in a first layer and second repetitive features at a second pitch in a second layer, the first repetitive features at least partially overlapping with the second repetitive features, and the first pitch being different from the second pitch;   causing the optical system to receive radiation scattered by the at least one structure and transmit a portion of the received scattered radiation to a sensor, the sensor configured to be arranged in an image plane of the optical system or in a plane conjugate with the image plane for detecting the received scattered radiation and configured to detect a characteristic of radiation impinging on the sensor; and   determining a characteristic of interest of the at least one structure on the substrate based on the radiation transmitted to the sensor.   
     
     
         2 . The computer program product of  claim 1 , wherein the processor further executes a process of controlling the optical system to prevent or allow transmission of radiation of the 0 th  diffraction order of the scattered radiation towards the sensor. 
     
     
         3 . The computer program product of  claim 2 , wherein the process of controlling the optical system to prevent or allow transmission of radiation of the 0 th  diffraction order of the scattered radiation towards the sensor comprises controlling a position of an optical element that is configured to prevent or allow the transmission of the radiation of the 0 th  diffraction order of the scattered radiation towards the sensor. 
     
     
         4 . The computer program product of  claim 3 , wherein the processor causes the optical element to move from a first position to a second position by means of a translation or a rotation of the optical element. 
     
     
         5 . The computer program product of  claim 2 , wherein the optical system is controlled so that radiation of the 0 th  diffraction order of the scattered radiation is reflected towards a second sensor. 
     
     
         6 . The computer program product of  claim 1 , wherein the determining the characteristic of interest of the at least one structure on the substrate comprises determining an overlay value of the first repetitive features and the second repetitive features. 
     
     
         7 . The computer program product of  claim 6 , wherein the determining an overlay value of the first repetitive features and the second repetitive features comprises determining a displacement between the first repetitive features and the second repetitive features. 
     
     
         8 . The computer program product of  claim 1 , wherein the determining the characteristic of interest of the at least one structure on the substrate comprises providing information about an expected or ideal structure to be detected. 
     
     
         9 . The computer program product of  claim 8 , wherein the determining the characteristic of interest of the at least one structure on the substrate further comprises applying pattern recognition to an image at the sensor to detect a structure similar to the expected or ideal structure. 
     
     
         10 . The computer program product of  claim 1 , wherein the determining the characteristic of interest of the at least one structure on the substrate comprises providing one or more parameters of the measurement. 
     
     
         11 . The computer program product of  claim 10 , wherein the one or more parameters of the measurement includes at least one of a wavelength, polarization, intensity distribution, and an illumination angle of illumination radiation. 
     
     
         12 . The computer program product of  claim 10 , wherein the one or more parameters of the measurement includes at least one of a number of measured points and one or more locations of measured points. 
     
     
         13 . The computer program product of  claim 1 , wherein the determining the characteristic of interest of the at least one structure on the substrate comprises providing one or more parameters of the structure. 
     
     
         14 . The computer program product of  claim 13 , wherein the one or more parameters of the structure includes at least one of a geometric characteristic, an orientation, a pitch, a size, and a segmentation of a feature in the structure. 
     
     
         15 . The computer program product of  claim 13 , wherein the one or more parameters of the structure includes at least one of a length the first repetitive feature or the second repetitive feature, a materials property of the structure, and an identification of the structure. 
     
     
         16 . The computer program product of  claim 15 , wherein:
 the one or more parameters of the structure includes a materials property of at least a part of the structure, and   the materials property includes at least one of a refractive index, an extinction coefficient, and a material type of the at least a part of the structure.   
     
     
         17 . The computer program product of  claim 1 , wherein the processor further executes a process of controlling actuators to move the at least one structure with respect to a spot of the beam of radiation that illuminates the at least one structure. 
     
     
         18 . The computer program product of  claim 1 , wherein the processor further executes a process of controlling a wavelength filter to transmit radiation of a predetermined wavelength or radiation having a wavelength within a predetermined range. 
     
     
         19 . The computer program product of  claim 1 , wherein the processor further executes a process of controlling a polarization of at least one of the beam of radiation and the scattered radiation. 
     
     
         20 . The computer program product of  claim 1 , wherein the processor further executes a process of controlling a wavelength of the beam of radiation emitted by the radiation source.