Charged particle beam device, charged particle beam system, and adjustment method
To correct a difference in signal intensity due to a difference in hardware, for example, temporal deterioration of the hardware in the same device, or a difference in signal intensity between different devices. An adjustment method according to the disclosure specifies an amplification gain with which the same detection signal intensity as that of a comparison target is obtained by comparing correspondence relationships between the detection signal intensity and the amplification gain at different time points in the same charged particle beam device or among different charged particle beam devices.
1 . An adjustment method for adjusting an amplification gain of an amplification unit, included in a solid-state electron multiplier tube or a micro channel plate, included in each of a plurality of charged particle beam devices configured to irradiate a sample with a charged particle beam,
each of the charged particle beam devices including
an irradiation unit configured to emit the charged particle beam,
a detector configured to detect a secondary particle generated from the sample due to irradiation on the sample with the charged particle beam and output a detection signal indicating an intensity of the secondary particle,
the amplification unit, which is configured to amplify the detection signal, and
a processor configured to adjust the amplification gain of the amplification unit,
the adjustment method comprising:
a step of acquiring a first correspondence relationship at a first time point between an intensity of the detection signal and the amplification gain in a first charged particle beam device of the plurality of charged particle beam devices;
a step of acquiring a second correspondence relationship at a second time point later than the first time point between the intensity of the detection signal and the amplification gain in the first charged particle beam device, or at the second time point between an intensity of the detection signal and the amplification gain in a second charged particle beam device of the plurality of charged particle beam devices; and
a step of specifying, by comparing the first correspondence relationship with the second correspondence relationship, the amplification gain in the first charged particle beam device so as to obtain, at the second time point in the first charged particle beam device, a detection signal intensity with which measurement accuracy or sensitivity equivalent to that of the detection signal of the first charged particle beam device at the first time point or of the second charged particle beam device at the second time point is obtained, and outputting a result thereof.
2 . The adjustment method according to claim 1 , wherein
the processor is further configured to adjust an offset of the detection signal, and
the adjustment method further comprises:
a step of acquiring a first intensity acquired by performing,
at the first time point on the first charged particle beam device or at the second time point on the second charged particle beam device,
a step of acquiring a minimum value of the detection signal while changing the offset in a state in which the sample is not irradiated with the charged particle beam,
a step of specifying the offset with which the minimum value is larger than a specified value equal to or larger than zero, and
a step of acquiring the first intensity of the detection signal corresponding to the amplification gain by referring to the first correspondence relationship using the specified offset, and
in the step of specifying the amplification gain, the amplification gain in the first charged particle beam device is specified such that the first intensity is obtained at the second time point.
3 . The adjustment method according to claim 2 , wherein
in the step of acquiring the first intensity, at the first time point on the first charged particle beam device or at the second time point on the second charged particle beam device, a result is acquired by performing
a step of specifying, when the first intensity is equal to or larger than a detection signal upper limit value, the amplification gain with which the detection signal smaller than the detection signal upper limit value is obtained by re-changing the offset and reacquiring the first intensity.
4 . The adjustment method according to claim 1 , further comprising:
a step of acquiring a first intensity acquired by performing,
at the first time point on the first charged particle beam device or at the second time point on the second charged particle beam device,
a step of acquiring a maximum value of the detection signal while changing the amplification gain in a state in which the sample is irradiated with the charged particle beam,
a step of acquiring the amplification gain with which the maximum value falls within a predetermined range larger or smaller than a target value, and
a step of acquiring the first intensity of the detection signal corresponding to the acquired amplification gain by referring to the first correspondence relationship using the acquired amplification gain, wherein
in the step of specifying the amplification gain, the amplification gain in the first charged particle beam device is specified such that the first intensity is obtained at the second time point.
5 . The adjustment method according to claim 4 , wherein
in the step of acquiring the first intensity, at the first time point on the first charged particle beam device or at the second time point on the second charged particle beam device, a result is acquired by performing a step of specifying, when the first intensity is equal to or larger than a detection signal upper limit value, the amplification gain with which the detection signal smaller than the detection signal upper limit value is obtained by re-changing the amplification gain and reacquiring the first intensity.
6 . The adjustment method according to claim 1 , wherein
the processor is further configured to adjust an offset of the detection signal, and
the adjustment method further comprises:
a step of acquiring a minimum value of the detection signal while changing the offset in a state in which the sample is not irradiated with the charged particle beam;
a step of specifying the offset with which the minimum value is larger than a specified value equal to or larger than zero; and
a step of generating an observation image of the sample using the specified offset and the specified amplification gain.
7 . The adjustment method according to claim 1 , further comprising:
a step of acquiring a first maximum value of the detection signal in the first charged particle beam device; and
a step of acquiring a second maximum value of the detection signal in the second charged particle beam device, wherein
in the step of specifying the amplification gain, the amplification gain is specified such that a smaller one of the first maximum value and the second maximum value is obtained in the first charged particle beam device.
8 . The adjustment method according to claim 1 , further comprising:
a step of reacquiring the first correspondence relationship at least at one of a time point at which the first correspondence relationship is changed by a threshold or more or a time point at which a predetermined time elapses after the first correspondence relationship is acquired; and
a step of reacquiring the second correspondence relationship at least at one of a time point at which the second correspondence relationship is changed by a threshold or more or a time point at which a predetermined time elapses after the second correspondence relationship is acquired.
9 . The adjustment method according to claim 1 , wherein
in the step of acquiring the first correspondence relationship, the first correspondence relationship is acquired using, as the sample, a mirror secondary particle acquired by the detector while applying the charged particle beam to a first calibration sample or the sample, and
in the step of acquiring the second correspondence relationship, the acquired second correspondence relationship is acquired by the second charged particle beam device using, as the sample, a mirror secondary particle acquired by the detector while applying the charged particle beam to a second calibration sample or the sample.
10 . The adjustment method according to claim 1 , further comprising:
a step of uniformizing, by specifying the amplification gain in the first charged particle beam device, a luminance value of an observation image of the sample acquired by the first charged particle beam device and a luminance value of an observation image of the sample acquired by the second charged particle beam device within a range in which the same degree of observation accuracy is obtained.
11 . The adjustment method according to claim 2 , further comprising:
a step of storing the acquired first intensity in data that is sharable between the first charged particle beam device and the second charged particle beam device.
12 . The adjustment method according to claim 11 , further comprising:
a step of sharing the first intensity between the first charged particle beam device and the second charged particle beam device by sharing the data in which the first intensity is recorded between the first charged particle beam device and the second charged particle beam device.
13 . The adjustment method according to claim 1 , further comprising:
a step of generating an observation image of the sample using the specified amplification gain.
14 . A charged particle beam device comprising:
a computer system configured to execute the adjustment method according to claim 1 .
15 . A charged particle beam system comprising:
a computer system configured to execute the adjustment method according to claim 1 ;
the first charged particle beam device; and
the second charged particle beam device.
16 . The charged particle beam system according to claim 15 , wherein
the computer system is configured to perform
a step of acquiring a first maximum value of the detection signal in the first charged particle beam device,
a step of acquiring a second maximum value of the detection signal in the second charged particle beam device, and
a step of sharing a smaller one of the first maximum value and the second maximum value between the first charged particle beam device and the second charged particle beam device, and
in the step of specifying the amplification gain, the computer system specifies the amplification gain such that the smaller one of the first maximum value and the second maximum value is obtained in the first charged particle beam device.