Overlay measurement system and overlay measurement device for overlay error measurement using electron microscopy

An overlay measurement system that comprises a scanning electron microscope and a computer subsystem and measures overlay error of a sample having an upper-layer pattern and a lower-layer pattern including a line pattern,

• wherein the scanning electron microscope includes
• an electron optical system that applies a primary electron beam to the sample,
• a secondary electron detector that detects secondary electrons among signal electrons emitted by scanning a surface of the sample with the primary electron beam, and
• a backscattered electron detector that detects backscattered electrons among the signal electrons, and
• the computer subsystem is configured to
• form a secondary electron image from a detection signal of the secondary electron detector and form a backscattered electron image from a detection signal of the backscattered electron detector,
• create a SUMLINE profile by summing luminance information of the backscattered electron image along a longitudinal direction of the line pattern, and
• calculate overlay error of the sample using positional information of the upper-layer pattern detected from the secondary electron image and positional information of the lower-layer pattern detected using an estimated line pattern estimated based on edge coordinates on the SUMLINE profile from the backscattered electron image,
• wherein the computer subsystem is configured to display a setting screen to set a measurement pattern, a measurement algorithm, and a measurement option for each of the detectors of the secondary electron detector and the backscattered electron detector,
• wherein a pattern detected from an image is set as the measurement pattern,
• an algorithm to detect the pattern set as the measurement pattern from the image is set as the measurement algorithm, and
• a setting item necessary for detecting the pattern set as the measurement pattern from the image according to the algorithm set as the measurement algorithm is set as the measurement option.

An overlay measurement system that comprises a scanning electron microscope and a computer subsystem and measures overlay error of a sample having an upper-layer pattern and a lower-layer pattern including a line pattern,

• wherein the scanning electron microscope includes
• an electron optical system that applies a primary electron beam to the sample,
• a secondary electron detector that detects secondary electrons among signal electrons emitted by scanning a surface of the sample with the primary electron beam, and
• a backscattered electron detector that detects backscattered electrons among the signal electrons, and
• the computer subsystem is configured to
• form a secondary electron image from a detection signal of the secondary electron detector and form a backscattered electron image from a detection signal of the backscattered electron detector,
• create a SUMLINE profile by summing luminance information of the backscattered electron image along a longitudinal direction of the line pattern, and
• calculate overlay error of the sample using positional information of the upper-layer pattern detected from the secondary electron image and positional information of the lower-layer pattern detected using an estimated line pattern estimated based on edge coordinates on the SUMLINE profile from the backscattered electron image,
• wherein the computer subsystem sets a cumulative frame number to acquire the secondary electron image and the backscattered electron image, and
• creates the SUMLINE profile while increasing by one a frame number to be summed for acquiring the backscattered electron image, and sets a frame number, the frame number being given when an evaluation value of the SUMLINE profile becomes equal to or larger than a threshold, as the cumulative frame number.

An overlay measurement system that comprises a scanning electron microscope and a computer subsystem and measures overlay error of a sample having an upper-layer pattern and a lower-layer pattern including a line pattern,

• wherein the scanning electron microscope includes
• an electron optical system that applies a primary electron beam to the sample,
• a secondary electron detector that detects secondary electrons among signal electrons emitted by scanning a surface of the sample with the primary electron beam, and
• a backscattered electron detector that detects backscattered electrons among the signal electrons, and
• the computer subsystem is configured to
• form a secondary electron image from a detection signal of the secondary electron detector and form a backscattered electron image from a detection signal of the backscattered electron detector,
• create a SUMLINE profile by summing luminance information of the backscattered electron image along a longitudinal direction of the line pattern, and
• calculate overlay error of the sample using positional information of the upper-layer pattern detected from the secondary electron image and positional information of the lower-layer pattern detected using an estimated line pattern estimated based on edge coordinates on the SUMLINE profile from the backscattered electron image,
• wherein the computer subsystem sets a cumulative frame number to acquire the secondary electron image and the backscattered electron image,
• creates the secondary electron image while increasing by one a frame number to be summed for acquiring the secondary electron image, and sets a frame number, the frame number being given when an evaluation value of the secondary electron image becomes equal to or larger than a threshold, as the cumulative frame number.

An overlay measurement device that measures overlay error of a sample having an upper-layer pattern and a lower-layer pattern including a line pattern from a secondary electron image and a backscattered electron image, each image being acquired by a scanning electron microscope, of the sample, the device comprising:

• a profile creation section that creates a SUMLINE profile by summing luminance information of the backscattered electron image along a longitudinal direction of the line pattern;
• and
• an overlay calculation section that calculates overlay error of the sample using positional information of the upper-layer pattern detected from the secondary electron image and positional information of the lower-layer pattern detected using an estimated line pattern estimated based on edge coordinates on the SUMLINE profile from the backscattered electron image,
• wherein the secondary electron image is an electron microscopic image formed based on secondary electrons contained in signal electrons emitted by scanning a surface of the sample with a primary electron beam, and the backscattered electron image is an electron microscopic image formed based on backscattered electrons contained in the signal electrons,
• wherein the upper-layer pattern is a pattern formed in a resist layer or an organic matter layer and the line pattern includes a metal layer or a semiconductor layer.