JPH04372887A - Charged particle beam device - Google Patents

Abstract

PURPOSE:To realize a charged particle beam device capable of measuring the relation between the high frequency exciting current applied to a magnetic head and the high frequency magnetic field generated thereby with high time resolving power and high time accuracy. CONSTITUTION:A current detecting resistor 4 is inserted in a magnetic head in series and the voltage generated across both terminals thereof is applied to a deflector 5. Stroboscopic pulse electron beam 11 of the same timing as the measuring time of a magnetic field is passed through the deflecting plate 5 and a current value is calculated by the conversion from the quantity of deflection thereof. By this constitution, the high frequency characteristics of a device generating a high frequency magnetic field such as the magnetic head can be more accurately evaluated in detail.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a charged particle beam device capable of measuring the relationship between a high frequency excitation current applied to a magnetic head etc. and a high frequency magnetic field generated thereby with high time resolution and high time accuracy. .

0002

[Background Art] Magnetic disk drives for computers, magnetic tape drives, and magnetic recording devices such as VTRs have made remarkable progress in increasing the density and speed of reading and writing, and the performance of the magnetic heads used in these devices has also improved. is requested.

In order to achieve high-density magnetic recording, a narrow-track magnetic head with a steep recording magnetic field distribution is required. In order to develop such a head, it is important to develop an apparatus that can precisely measure the distribution of the recording magnetic field generated by the head. A known method for measuring the recording magnetic field distribution of a magnetic head is to make an electron beam pass near the gap of the magnetic head and take advantage of the fact that the electron beam is bent by the Lorentz force caused by the magnetic field. It is being To measure the three-dimensional distribution of a magnetic field, the sample that generates the magnetic field is rotated little by little while the electron beam is scanned, the amount of deflection of the electron beam due to the magnetic field is detected by a position detector, and the amount of deflection of the electron beam is measured. Get data. Then, based on this data, computed tomography (hereinafter referred to as C
A Lorentz tomography method is known in which the original magnetic field distribution is reconstructed by calculation using

On the other hand, in order to increase the speed of writing and reading, it is essential to improve the frequency characteristics of the magnetic head. As the frequency of the current applied to the magnetic head increases, the reversal of magnetization of the magnetic material constituting the head pole becomes unable to respond to changes in the current, and the strength of the magnetic field generated from the tip of the head pole decreases. This limits the writing speed. In order to develop a magnetic head capable of high-speed operation, it is essential to measure the magnetic field distribution while the magnetic head is operating at high frequency. As a method for measuring such a high-frequency magnetic field distribution, a method is known in which strobe measurement using a pulsed electron beam is employed in Lorentz tomography. In this method, one pulsed electron beam is generated during one period of the excitation current waveform, and the phase of this pulsed electron beam is controlled. If the measurement is performed with the phase fixed, the magnetic field strength at the instant of the phase when the pulsed electron beam passes can be measured as if it were a DC magnetic field. Also, by changing the phase of the pulsed electron beam little by little and measuring one period, changes over one period can be measured. Such an example is given in Proceedings of the 51st Annual Conference of the Japan Society of Applied Physics, P510 (October 1990).
), and in the Japan Society for the Promotion of Science's 132nd Committee on Industrial Applications of Charged Particle Beams, 113th Research Meeting Materials, page 7. However, in this measurement, it was difficult to correlate the responses of the excitation current and magnetic field with high time accuracy. This is because conventionally, excitation current cannot be measured using the strobe method, and is measured in real time using an ordinary current probe.
This was because the time standards of the measured generated magnetic field and excitation current did not match.

[0005]

In order to accurately measure the temporal relationship between the high frequency magnetic field generated by the magnetic head and the excitation current, it is necessary to perform measurements in which the time standards of both coincide.

[0006]

Means for Solving the Problems The high frequency excitation current applied to the magnetic head is measured using the same strobe pulsed electron beam as used for magnetic field measurement. Specifically, a resistor is inserted in series with the magnetic head, and a voltage generated at both ends is applied to the deflection plate. A strobe pulse electron beam is passed through this deflection plate, and the amount of deflection is converted into a current value. Alternatively, an air-core coil is inserted in series with the magnetic head. Then, a strobe pulse electron beam is passed through the magnetic field generated by the air-core coil.
The current value is converted from the amount of deflection. These methods measure current and magnetic field with a strobe pulsed electron beam at the same timing, allowing accurate temporal correspondence between the two.

[0007]

[Operation] There is no means to directly measure the current value using a strobe pulsed electron beam. Therefore, this is made possible by converting the current into a magnetic field, electric field, or voltage.

First, the case of converting into an electric field will be described. A resistor is inserted in series with the magnetic head, and the excitation current waveform is first converted into voltage. By applying this voltage to the deflection plate, an electric field having the same timing as the excitation current waveform is generated. If the capacitance of the deflection plate is sufficiently small, the delay between the excitation current and the generated electric field can be ignored. A strobe pulsed electron beam is passed through this deflection plate. FIG. 1 shows the timing of this strobe pulse electron beam along with time changes in the excitation current waveform, electric field waveform, and generated magnetic field. The pulsed electron beam that has passed through the deflection plate receives a deflection corresponding to the current value at the moment A when it passes through the deflection plate. Therefore, by measuring this amount of deflection, the excitation current value A can be determined. After this current measurement is performed, the pulsed electron beam is moved to a region near the surface of the magnetic head where the magnetic field is measured, and the amount of deflection due to the magnetic field is measured. Through this measurement, the magnetic field strength at the moment A can be measured. If the above measurement is performed for one cycle by slightly shifting the phase relationship between the pulsed electron beam and the excitation current waveform, it is possible to measure one cycle while accurately taking the temporal correspondence between the excitation current waveform and the change in the magnetic field. can.

[0009] Furthermore, when converting the excitation current into a magnetic field,
Instead of a resistor, an air-core coil is inserted in series with the magnetic head. The magnetic field generated by the air-core coil has the same timing as the current flowing through the coil. This magnetic field can be measured using a strobe pulse electron beam in the same way as the electric field.

In the method of converting excitation current into voltage, a resistor is inserted in series with the magnetic head. A strobe pulse electron beam is applied to both ends of this resistor, and the energy of the secondary electrons generated is analyzed to determine the voltage across the resistor. If the voltage across a resistor can be measured, the current flowing through this resistor can be determined.

[0011]

[Embodiment] A first embodiment of the present invention will be explained with reference to FIG. The drive circuit 3 generates a high frequency current using the high frequency signal of the oscillator 1 as a trigger signal. The magnetic head 2 is excited by this high frequency current. A current detection resistor 4 is inserted in series with the magnetic head, and deflection plates 5 are connected to both ends of the current detection resistor 4. On the other hand, the high frequency signal of the oscillator 1 is transmitted to the delay circuit 6.
The signal is also sent to the pulse generator 7 and serves as a trigger signal for the pulse generator 7. The signal from the pulse generator 7 is applied to an electron beam blanker 8, where the electron beam 10 is pulsed. The pulsed electron beam 11 can be moved to any desired position by a scanning deflector 12. Behind the magnetic head 2 is a position detector 14 that detects the position of the pulsed electron beam.
is placed. When measuring the high frequency current that excites the magnetic head, a pulsed electron beam is passed through the deflection plate 5 by the scanning deflector 12. The amount of deflection caused by this is measured by the rear position detector 14 and converted into a current value. The phase of the pulsed electron beam is controlled by a delay circuit 6. By changing the delay amount of the delay circuit 6 little by little and measuring one cycle of the high frequency current, a high frequency current waveform can be obtained. When measuring the high frequency magnetic field generated by the magnetic head 2, the pulsed electron beam 11 is moved by a scanning deflector 12 to a space near the surface of the magnetic head. The amount of deflection of the pulsed electron beam 11 due to the magnetic field is measured by the rear position detector 14, and this is converted into magnetic field strength. When measuring how the magnetic field changes during one cycle of the high-frequency excitation current, the delay circuit 6 changes the amount of delay little by little and repeats the measurement. Through the above measurements, it is possible to accurately measure the temporal correspondence between the high-frequency excitation current and the high-frequency magnetic field generated thereby.

In the Lorentz tomography method for three-dimensionally measuring magnetic field distribution, it is necessary to repeat the process of passing an electron beam near the surface of a magnetic head and measuring the amount of deflection by rotating the magnetic head little by little. In the case of this measurement, it is preferable to use a sample stage having a structure as shown in FIG. The magnetic head 2 is placed on top of a cylindrical sample stage 21 . The sample stage 21 is made of non-magnetic metal, has a through hole in its side surface, and has a deflection plate 5 provided therein. By making the deflection plate 5 and the sample stage 21 into an integral structure in this way, even if the sample stage 21 is rotated, the lead wire 22 connecting the deflection plate 5 and the magnetic head will not be twisted. Furthermore, since the distance between the deflection plate 5 and the magnetic head 2 can be brought closer, the delay caused by the lead wire 22 between the magnetic head 2 and the deflection plate 5 can be ignored. Further, since the electric field generated by the deflection plate 5 is inside the metallic sample stage 21, it does not affect the vicinity of the surface of the magnetic head 2. Therefore, when measuring a magnetic field, measurement errors do not occur due to the influence of an electric field.

In the above description, the method of converting the excitation current into an electric field has been described. However, in the method of converting the excitation current into a magnetic field, an air-core coil may be inserted in place of the current detection resistor 4 and the deflection plate 5. In this case, it is necessary to provide a magnetic shield between the air-core coil and the magnetic head so that the magnetic field generated by the air-core coil does not affect the magnetic field generated by the magnetic head 2.

Furthermore, the potential across the current detection resistor 4 inserted in series with the magnetic head 2 is set to the strobe pulse electron beam 1.
It is also possible to determine the excitation current by measuring according to 1. This example will be explained with reference to FIG. A secondary electron energy analyzer 31 is added to the configuration of FIG. 2. The energy of the secondary electrons 30 generated by irradiation with the pulsed electron beam 11 changes depending on the potential of the irradiation part. The amount of change in this secondary electron energy is measured by an energy analyzer 31. The current value is determined from the potential difference between both ends of the current detection resistor 4 thus determined.

[0015]

[Effects of the Invention] When a magnetic head or the like is excited by a high-frequency current and the resulting high-frequency magnetic field is measured with an electron beam, it is now possible to accurately correlate the current with time. This has made it possible to evaluate the high frequency characteristics of magnetic heads and the like in more detail.

[Brief explanation of the drawing]

[Figure 1] Diagram explaining magnetic head excitation current, generated magnetic field, and timing of pulsed electron beam

[Figure 2] Configuration diagram of an embodiment of the present invention

FIG. 3 is a diagram explaining the structure of another embodiment of the present invention.

[Figure 4
] Configuration diagram of another embodiment of the present invention

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Oscillator, 2... Magnetic head, 3... Drive circuit, 4... Current detection resistor, 5... Deflection plate, 6... Delay circuit, 7... Pulse oscillator, 8... Electron beam blanker, 10... Electron beam, 11
...Pulse electron beam, 12...Scanning deflector, 14...Position detector, 21...Sample stage, 22...Lead wire, 30...Secondary electron, 31...Energy analyzer.

Claims (7)

[Claims] 1. A sample that generates a high-frequency magnetic field by applying a high-frequency current, means for generating a pulsed charged particle beam synchronized with the high-frequency current, and means for converting the high-frequency current into a voltage value. an electrostatic deflection plate that applies the voltage value; a means for passing the pulsed charged particle beam through the electrostatic deflection plate or any location in the high-frequency magnetic field; and an electric field generated by the electrostatic deflection plate or the means for measuring the amount of deflection of the charged particle beam bent by the high frequency magnetic field generated by the sample; A charged particle beam device characterized in that the high frequency magnetic field strength is determined from the amount of deflection of the charged particle beam. 2. A sample that generates a high-frequency magnetic field by applying a high-frequency current, means for generating a pulsed charged particle beam synchronized with the high-frequency current, and an air-core coil inserted in series with the sample. , a means for passing the pulsed charged particle beam near the air-core coil or any place in the high-frequency magnetic field; and a means for measuring the amount of deflection of the charged particle beam, the high frequency current being determined from the amount of deflection of the charged particle beam due to the electric field, and the high frequency magnetic field strength being determined from the amount of deflection of the charged particle beam due to the magnetic field. Characteristic charged particle beam device. 3. The charged particle beam apparatus according to claim 1, further comprising: means for rotating the sample around an axis perpendicular to the traveling direction of the charged particle beam; A charged particle beam device that measures the amount of deflection caused by the magnetic field generated by the sample multiple times at different rotation angles and calculates the spatial intensity distribution of the magnetic field on the sample surface. 4. In the charged particle beam device according to claim 3, the sample is placed on an upper part of a non-magnetic metal sample stage, and a hole is provided in the side surface of the sample stage to penetrate through the sample stage. A charged particle beam device comprising the deflection plate. 5. The charged particle beam device according to claim 2, further comprising: means for rotating the sample around an axis perpendicular to the traveling direction of the charged particle beam; A charged particle beam device that measures the amount of deflection caused by the magnetic field generated by the sample multiple times at different rotation angles and calculates the spatial intensity distribution of the magnetic field on the sample surface. 6. In the charged particle beam device according to claim 5, the sample is placed on an upper part of a non-magnetic metal sample stage, and a hole is provided in the side surface of the sample stage to pass through, and a hole is provided inside the charged particle beam device. A charged particle beam device comprising the air-core coil. 7. A sample that generates a high-frequency magnetic field by applying a high-frequency current, means for generating a pulsed charged particle beam synchronized with the high-frequency current, a resistor inserted in series with the sample, and a means for irradiating both ends of the resistor with a pulsed charged particle beam or passing it through any location in the high frequency magnetic field, and analyzing the energy of secondary electrons generated from both ends of the resistor by irradiating the pulsed charged particle beam. It consists of means for measuring the voltage value across the resistor, and means for measuring the amount of deflection of the charged particle beam bent by the high-frequency magnetic field generated by the sample. A charged particle beam device characterized in that the high frequency magnetic field strength of the high frequency current is determined from the amount of deflection of the charged particle beam due to the magnetic field.