A position detection apparatus configured to detect a pattern including a plurality of pattern elements formed on an object includes a control unit configured to detect the pattern by performing pattern matching between a template including a plurality of feature points and the plurality of pattern elements. While, performing pattern matching, the control unit changes positions of the plurality of feature points such that a correlation between an image and the template is within a predetermined allowable range.

Aspects of the present disclosure provide an imaging system. For example, in the imaging system a first light source can generate a first light beam of a first wavelength, a second light source can generate a second light beam of a second wavelength, the second light beam having power sufficient to pass through at least a portion of a thickness of a wafer, an alignment module can coaxially align the second light beam with the first light beam, a coaxial module can focus the coaxially aligned first and second light beams onto a first pattern located on a front side of the wafer and a second pattern located below the first pattern, respectively, and an image capturing module can capture a first image of the first pattern and a second image of the second pattern. The second image can be captured via quantum tunneling imaging or infrared (IR) transmission imaging.

A method of determining a position of a feature (for example an alignment mark) on an object (for example a silicon wafer) is disclosed. The method comprises determining an offset parameter, determining the second position; and determining a first position from the second position and the offset parameter, the position of the mark being the first position. The offset parameter is a measure of a difference in: a first position that is indicative of the position of the feature; and a second position that is indicative of the position of the feature. The offset parameter may be determined using a first measurement apparatus and the second position may be determined using a second, different measurement apparatus.

A method of measuring overlay uses a plurality of asymmetry measurements from locations (LOI) on a pair of sub-targets (1032, 1034) formed on a substrate (W). For each sub-target, the plurality of asymmetry measurements are fitted to at least one expected relationship (1502, 1504) between asymmetry and overlay, based on a known bias variation deigned into the sub-targets. Continuous bias variation in one example is provided by varying the pitch of top and bottom gratings (P1/P2). Bias variations between the sub-targets of the pair are equal and opposite (P2/P1). Overlay (OV) is calculated based on a relative shift (xs) between the fitted relationships for the two sub-targets. The step of fitting asymmetry measurements to at least one expected relationship includes wholly or partially discounting measurements (1506, 1508, 1510) that deviate from the expected relationship and/or fall outside a particular segment of the fitted relationship.

Embodiments of the present disclosure provide an alignment mark evaluation method and an alignment mark evaluation system. The alignment mark evaluation method includes: setting a process step code of a wafer with an alignment mark to be evaluated as an evaluation code; obtaining a current process step code of the wafer; if it is detected that the current process step code is the evaluation code, switching a step to be executed to an alignment mark evaluation step; and executing the alignment mark evaluation step to evaluate the alignment mark to be evaluated.

A method of processing a wafer is provided. The method includes providing a reference plate below the wafer. The reference plate includes a reference pattern. The reference plate is imaged to capture an image of the reference pattern by directing light through the wafer. A first pattern is aligned using the image of the reference pattern. The first pattern is applied to a working surface of the wafer based on the aligning.

Aspects of the present disclosure provide a method of aligning a wafer pattern. For example, the method can include providing a wafer having a reference pattern located below a front side of the wafer, and directing a light beam to the wafer. The method can further include identifying at least one of power and a wavelength of the light beam such that the light beam is capable of passing through the wafer and reaching the reference pattern, or identifying at least one of power and a wavelength of the light beam based on at least one of a material of the wafer and a depth of the reference pattern below the front side of the wafer. The method can further include using the light beam to image the reference pattern.

Aspects of the present disclosure provide an inspection system, which can include an image module and processing circuitry. The imaging module can image a wafer with a first light beam and a second light beam. The first light beam can be coaxially aligned with the second light beam, and image a first pattern located on a front side of a wafer to form a first image. The second light beam can image a second pattern located below the first pattern to form a second image via quantum tunneling imaging or infrared transmission imaging. The second light beam can have power sufficient to pass through at least a portion of a thickness of the wafer and reach the second pattern. The processing circuitry can perform image analysis on the first image and the second image to calculate an overlay value of the first and second patterns and/or defects of the wafer.

Aspects of the present disclosure provide an imaging system. For example, in the imaging system a first light source can generate a first light beam of a first wavelength, a second light source can generate a second light beam of a second wavelength, the second light beam having power sufficient to pass through at least a portion of a thickness of a wafer, an alignment module can coaxially align the second light beam with the first light beam, a coaxial module can focus the coaxially aligned first and second light beams onto a first pattern located on a front side of the wafer and a second pattern located below the first pattern, respectively, and an image capturing module can capture a first image of the first pattern and a second image of the second pattern. The second image can be captured via quantum tunneling imaging or infrared (IR) transmission imaging.

A method of pattern alignment is provided. The method includes identifying a reference pattern positioned below a working surface of a wafer. The wafer is exposed to a first pattern of actinic radiation. The first pattern is a first component of a composite pattern. The first pattern of actinic radiation is aligned using the reference pattern. The wafer is exposed to a second pattern of actinic radiation. The second pattern is a second component of the composite pattern and exposed adjacent to the first pattern. The second pattern of actinic radiation is aligned with the first pattern of actinic radiation using the reference pattern.