Measuring device and measuring method
A measuring device for measuring a sample by emitting a charged particle beam includes a particle source, an electronic lens, a detector, a stage, a sensor for measuring the environment, and a control device, in which the control device includes a control module having a height calculation module configured to calculate a height estimation value indicating an estimated height of the sample at a measurement position; and a correction value calculation module configured to calculate a correction value reflecting a change of the environment based on the measurement position of the sample and an amount of change of the environment measured by the sensor, and the control module corrects the height estimation value based on the correction value, and sets a control value for controlling focus adjustment using the electronic lens based on the corrected height estimation value.
1. A measuring device for measuring a sample by emitting a charged particle beam, the measuring device comprising:
a particle source configured to emit the charged particle beam;
an electronic lens configured to focus the charged particle beam;
a detector configured to detect a signal generated from the sample irradiated with the charged particle beam;
a stage capable of moving with the sample mounted thereon;
an electrostatic chuck attached to the stage that fixes the sample, the stage and the electrostatic chuck being made of different materials;
a sensor configured to measure environment of the measuring device; and
a control device configured to control the measuring device overall, the control device comprising a processor that executes:
a height calculation process configured to calculate a height estimation value indicating an estimated height of the sample at a measurement position; and
a correction value calculation process configured to calculate a correction value reflecting a change of the environment based on the measurement position of the sample and an amount of change of the environment measured by the sensor;
a height correction process to correct the height estimation value based on the correction value; and
a setting process to set a control value for controlling focus adjustment using the electronic lens based on the corrected height estimation value, wherein
the control device retains parameter information representing a distribution of distortions caused by a stress of a connecting portion of the stage and the electrostatic chuck due to a difference in materials thereof for calculating the correction value, and
the correction value calculation process calculates the correction value of the measurement position of the sample based on the measurement position of the sample, the amount of environmental change measured by the sensor, and the parameter information.
2. The measuring device according to claim 1 , wherein
the control device retains a focus map indicating a relationship between a position of the sample in a plane and a height of the sample,
the height calculation process calculates the height estimation value based on the measurement position of the sample and the focus map.
3. The measuring device according to claim 2 , wherein
the environment is at least one of a temperature and an atmospheric pressure.
4. The measuring device according to claim 3 , further comprising:
a height sensor configured to measure an actual measured value indicating the height of the sample at the measurement position, wherein
the processor executes a process to:
calculate an error between the corrected height estimation value and the actual measured value after the control value is set based on the corrected height estimation value;
set a new control value based on the actual measured value; and
update the parameter information based on the error.
5. The measuring device according to claim 4 , wherein
the electronic lens includes an electromagnetic lens for changing a focusing action of the charged particle beam by using the action of a magnetic field lens and an electrostatic lens for changing the focusing action of a charged particle beam by using the action of an electric field, and
the processor executes a process to:
determine whether the corrected height estimation value is greater than a threshold value;
set a control value for controlling a focus adjustment using the electrostatic lens based on the corrected height estimation value when it is determined that the corrected height estimation value is equal to or less than the threshold value;
set a control value for controlling a focus adjustment using the electromagnetic lens based on the corrected height estimation value when it is determined that the corrected height estimation value is greater than the threshold value; and
set a control value for controlling focus adjustment using the electrostatic lens based on the actual measured value.
6. The measuring device according to claim 1 , wherein
the electrostatic chuck fixes the sample by adsorbing the sample.
7. A measuring method in a measuring device for measuring a sample by emitting a charged particle beam, the measuring device including a particle source configured to emit the charged particle beam; an electronic lens configured to focus the charged particle beam; a detector configured to detect a signal generated from the sample irradiated with the charged particle beam; a stage capable of moving with the sample mounted thereon; an electrostatic chuck attached to the stage that fixes the sample, the stage and the electrostatic chuck being made of different materials; a sensor configured to measure environment of the measuring device; and a control device configured to control the measuring device overall and including a control module, the measuring method comprising:
a first step in which the control module calculates a height estimation value indicating an estimated value of the height of the sample at a measurement position;
a second step in which the control module calculates a correction value reflecting an environmental change based on the measurement position and an amount of the environmental change measured by the sensor;
a third step in which the control module corrects the height estimation value based on the correction value;
a fourth step in which the control module sets a control value for controlling a focus adjustment using the electronic lens based on the corrected height estimation value; and
a fifth step in which the control module detects the signal by irradiating the sample with the charged particle beam set to a predetermined focus value by the electronic lens to which the control value is set, wherein
the control device retains parameter information representing a distribution of distortions caused by a stress of a connecting portion of the stage and the electrostatic chuck due to a difference in materials thereof for calculating the correction value, and
in the second step, the control module calculates the correction value of the measurement position of the sample based on the measurement position of the sample, the amount of environmental change measured by the sensor, and the parameter information.
8. The measuring method according to claim 7 , wherein
the control device retains a focus map indicating a relationship between a position of the sample in a plane and a height of the sample,
in the first step, the control module calculates the height estimation value based on the measurement position of the sample and the focus map.
9. The measuring method according to claim 8 , wherein
the environment is at least one of a temperature and an atmospheric pressure.
10. The measuring method according to claim 9 , wherein
the measuring device further includes a height sensor configured to measure an actual measured value indicating the height of the sample at the measurement position, and
the measuring method further comprises:
a sixth step in which the control module sets a new control value based on the actual measured value after the process of the fourth step is executed; and
a seventh step in which the control module updates the parameter information based on an error between the corrected height estimation value and the actual measured value after the process of the fifth step is executed.
11. The measuring method according to claim 10 , wherein
the electronic lens includes an electromagnetic lens for changing a focusing action of the charged particle beam by using the action of a magnetic field and an electrostatic lens for changing the focusing action of a charged particle beam by using the action of an electric field,
the fourth step includes:
a step in which the control module determines whether the corrected height estimation value is greater than a threshold value;
a step in which, when it is determined that the corrected height estimation value is equal to or less than the threshold value, the control module sets a control value for controlling a focus adjustment using the electrostatic lens based on the corrected height estimation value; and
a step in which, when it is determined that the corrected height estimation value is greater than the threshold value, the control module sets a control value for controlling a focus adjustment using the electromagnetic lens based on the corrected height estimation value, and
the sixth step includes a step in which the control module sets a control value for controlling a focus adjustment using the electrostatic lens based on the actual measured value.
12. The measuring method according to claim 7 , wherein
the electrostatic chuck fixes the sample by adsorbing the sample.