Method for measuring a pattern dimension using a scanning electron microscope

A method for measuring a measurement target pattern with an electron microscope to acquire actual electron microscope images of the measurement target pattern with electron beams at two or more different incident angles under image acquisition conditions and estimate the three-dimensional shape of the measurement target pattern by using the acquired two or more actual electron microscope images, the method comprising:

• a measurement recipe creation step of obtaining pattern shape information by modeling approximate shapes of various target patterns in numerical data in advance, which are obtained by varying dimensions in a predetermined predicted variation range;
• a library creation step of creating a group of first simulated waveforms of electron microscope signals obtained by irradiating the various target pattern shapes with the electron beams at the two or more different incident angles by performing electron beam simulations on the various target pattern shapes within the predicted variation range, the electron beam simulations representing characteristics of an electron microscope, including electron optics resolution, beam divergence half angle and aberration coefficients, and image acquisition conditions imposed by the electron microscope, including conditions for emitting electron beams at the two or more different incident angles, and storing a combination of the created group of the two or more first simulated waveforms of the electron microscope signals and the pattern shape information, which corresponds to the created group of the first simulated waveforms and is obtained in the measurement recipe creation step, as a library;
• and
• a measurement step of acquiring an actual electron microscope image of a measurement target pattern with the electron microscope which is adjusted in focus and astigmatism and comparing the acquired two or more actual electron microscope images with the group of the first simulated waveforms created in the library creation step or a group of second simulated waveforms, which are created from the group of the first simulated waveforms, and measuring the three-dimensional shape of the measurement target pattern by selecting the pattern shape information that minimizes total errors between the two or more actual electron microscope images and the group of the first simulated waveforms or the group of the second simulated waveforms,
• wherein the library creation step includes the steps of:
• calculating a best focus position by using simulation images for each of the target pattern shapes in the same evaluation method as with an actual electron microscope, in advance;
• and
• reflecting the calculated best focus position in the electron beam simulation as an image acquisition condition imposed by the electron microscope.

A method for measuring a measurement target pattern with an electron microscope to acquire actual electron microscope images of the measurement target pattern with electron beams at two or more different incident angles under image acquisition conditions and estimate the three-dimensional shape of the measurement target pattern by using the acquired two or more actual electron microscope images, the method comprising:

• a measurement recipe creation step of obtaining pattern shape information by modeling approximate shapes of various target patterns in numerical data in advance, which are obtained by varying dimensions in a predetermined predicted variation range;
• a library creation step of creating a group of first simulated waveforms of electron microscope signals obtained by irradiating the various target pattern shapes with the electron beams at the two or more different incident angles by performing electron beam simulations on the various target pattern shapes within the predicted variation range, the electron beam simulations representing characteristics of an electron microscope, including electron optics resolution, beam divergence half angle and aberration coefficients, and image acquisition conditions imposed by the electron microscope, including conditions for emitting electron beams at the two or more different incident angles, and storing a combination of the created group of the two or more first simulated waveforms of the electron microscope signals and the pattern shape information, which corresponds to the created group of the first simulated waveforms and is obtained in the measurement recipe creation step, as a library;
• and
• a measurement step of acquiring an actual electron microscope image of a measurement target pattern with the electron microscope which is adjusted in focus and astigmatism and comparing the acquired two or more actual electron microscope images with the group of the first simulated waveforms created in the library creation step or a group of second simulated waveforms, which are created from the group of the first simulated waveforms, and measuring the three-dimensional shape of the measurement target pattern by selecting the pattern shape information that minimizes total errors between the two or more actual electron microscope images and the group of the first simulated waveforms or the group of the second simulated waveforms,
• wherein the library creation step includes the steps of:
• calculating a best focus position by using simulation images for each of the target pattern shapes in the same evaluation method as with an actual electron microscope, in advance;
• and
• reflecting the calculated best focus position in the electron beam simulation as an image acquisition condition imposed by the electron microscope.

A method of measuring a target pattern and estimating a shape of the target pattern comprising the steps of:

• acquiring a plurality of images of the target pattern using a plurality of different apparatuses;
• determining which apparatus has the highest resolution, based on evaluation of the acquired images;
• selecting an image acquired by the highest resolution apparatus and designating the selected image as an actual electron microscope image of the target pattern;
• creating a measurement recipe creation by obtaining pattern shape information and numerically modeling, in advance, approximate shapes of various target patterns obtained by varying dimensions in a predetermined predicted variation range;
• creating a library of first simulated waveforms by:
• performing electron beam simulations for various target pattern shapes within the predicted variation range, the electron beam simulations representing characteristics of an electron microscope, including electron optics resolution, beam divergence half angle and aberration coefficients, and image acquisition condition imposed by the electron microscope, and
• storing a combination of the created first simulated waveforms of the electron microscope signals and the pattern shape information corresponding to the first simulated waveforms, as a library;
• adjusting focus and astigmatism of the actual electron microscope image of the target pattern;
• comparing the acquired actual electron microscope image with either the first simulated waveforms, or second simulated waveforms which are created from the first simulated waveforms;
• selecting a first simulated waveform or a second simulated waveform which is most similar to the acquired actual electron microscope image;
• and
• estimating the shape of the measurement target pattern from the pattern shape information that corresponds to the selected first simulated waveform or second simulated waveform and is used in creating the library,
• wherein the step of creating a library further comprises the steps of:
• calculating a best focus position by using simulation images for each of the target pattern shapes in the same evaluation method as with an actual electron microscope, in advance, and
• reflecting the calculated best focus position in the electron beam simulation as an image acquisition condition imposed by the electron microscope.