JPS605503Y2 - Transmission scanning electron microscope - Google Patents

Description

[Detailed description of the invention] The present invention relates to an electron microscope, and in particular to a transmission type scanning electron microscope that can scan and irradiate a sample with an electron beam and detect the scattered electron beam that has passed through the sample to obtain a dark-field image of the sample. Regarding electron microscopes.

A conventional transmission scanning electron microscope is schematically shown in FIG. 1, where 1 is a sample, and the sample 1 is irradiated with an electron beam that is scanned over the sample.

The electron beam transmitted through the sample 1 is diffracted as it passes through the sample, and a diffraction image is formed near the back focal plane of the objective lens 2 for each diffracted electron beam of a different order.

Among such diffracted electron beams, for example, in order to obtain a dark field image based on the electron beam a from the imaging point of the next diffracted electron beam, the electron beam a is placed in a cylindrical space surrounded by an objective lens yoke. The first deflection coil 3 deflects the light by an angle θ1 toward the optical axis, and the second deflection coil 4, which is also placed in the space, deflects the light by an angle θ2 in the opposite direction.
The beam is then swung back and guided along the optical axis, leading to an electron beam detector.

In such a conventional device, in order to obtain a dark field image based on a higher-order diffracted electron beam, the magnetic field strength created by the first and second deflection coils, especially the first deflection coil 3, is increased. Since the deflection angle θ must be increased, the number of turns of the first deflection coil must be increased, or the current supplied must be increased.

On the other hand, there are electron microscopes that include an electromagnetic lens that functions as a second objective lens placed along the optical axis in a cylindrical space surrounded by an objective lens yoke. It is known that images can be observed at a range of magnifications.

Therefore, the present application proposes a novel system that enables the observation of dark-field images based on higher-order diffracted electron beams without increasing the number of windings of the first deflection coil or the supply current. The present invention will be described below with reference to the drawings.

In FIGS. 2 and 3 for showing an embodiment of the present invention, 5 is an objective lens yoke, and 6 is an excitation coil for the objective lens.

In the cylindrical space 7 of the objective lens yoke, a first deflection coil 8 and a second deflection coil 9 are arranged spaced apart from each other.

An electromagnetic lens 10 is disposed in the space 7 between the first and second deflection coils 8.9 along the optical axis.

The electromagnetic lens 10 includes an excitation coil 11 and an auxiliary yoke 10a.
It becomes more.

The first and second deflection coils 8 and 9 each consist of a pair of X-ray deflection coils and a Y deflection coil, ie, 8X, 8Y, 9X, and 9Y, as shown in FIG.

FIG. 3 is a diagram for explaining the mutual relationship between the currents supplied to each coil and the deflection that the electron beam undergoes. In the figure, 1 and 2 represent a sample and an objective lens, respectively.
11 represents the excitation coil 11 in FIG.

As shown in FIG. 3, the first X deflection coil 8X and the first
The Y deflection coils 8Y each have a first X deflection power source 12X1.
Current regulators 13X, 1 from the first Y deflection power supply 12Y, respectively.
Similarly, the second X deflection and Y deflection coils 9X and 9Y are supplied with current regulators 15X and 15 from the second X deflection and Y deflection power supplies 14X and 14Y, respectively.
Deflection current is supplied via Y.

Signals related to the set values of the currents supplied by the current regulators 15X and 15Y are supplied to current regulators 13X and 13Y, respectively.

Further, an exciting current from a power source 16 is supplied to the exciting coil 11 via a current regulator 17.

A signal regarding the set value of the current supplied by the current regulator 17 is supplied to the current regulators 15X and 15Y.

In such a configuration, when attempting to observe a dark-field image based on the diffracted electron beam that has passed through the sample, a current,
Adjust the regulators 15X, 15Y and 17 to adjust the second
The currents supplied to the deflection coil, Y deflection coil, and excitation coil 11 are set.

The signals related to the set values by the current regulators 15X and 15Y are supplied to the first X current regulators 13X and 13Y, respectively.
Deflection, Y deflection from the power supplies 12X, 12Y to the first X deflection, Y
The current supplied to the deflection coils 13X and 13Y is specified.

Further, the signal regarding the supply current setting value by the current regulator 17 is supplied to the current regulators 15X and 15Y, and these
Add correction to the initial current supply setting value by the regulator.

That is, the electromagnetic lens 10 acts as a converging lens 18, but when an electron beam passes through this lens 18, the electron beam rotates by an angle corresponding to the excitation intensity. X deflection, Y deflection coil 9X, 9
In order to perform it together with Y, actually these coils 9X
.

The current value supplied to 9Y is a value that deviates from the initial setting value.

Now, apply the current determined in this way to each coil, 8X
, 8Y, 11, 9X, and 9Y, when the sample 1 is irradiated with a scanning electron beam, the diffracted electron beam is deflected by the first deflection coil 8 toward the optical axis by an angle Φ1, Further, after being deflected by an angle Φ by a converging lens 18 formed by the excitation coil 11, it is deflected back by an angle Φ2 by a second deflection coil 9 so as to proceed along the optical axis.

Therefore, the electron beam is extra deflected by the deflection angle Φ by the converging lens 18, and Φ□ in FIG. 1 can be substantially increased to a large value without increasing the number of turns of the first deflection coil or the supply current. It is possible to observe dark-field images based on high-order diffracted electron beams.

Furthermore, in the device based on the present invention, if only the electromagnetic lens 10 is operated in conjunction with other lenses without supplying current to the first and second deflection coils 8 and 9, an extremely wide range can be achieved. An electron microscope transmission image can be observed at a magnification of .

[Brief explanation of drawings]

Figure 1 is a diagram for explaining the conventional device, Figures 2 and 3
The figure is a diagram for explaining one embodiment of the present invention. 1: sample, 2: objective lens, 3, 8: first deflection coil, 4, 9: second deflection coil, 5: objective lens yoke,
6.11: Excitation coil, 7: Cylindrical space, 10: Electromagnetic lens, 10a: Auxiliary yoke, 12X, 12Y, 14X,
14Y: Deflection power supply, 13X, 13Y, 15X, 15Y,
17: Current regulator, 16: Power supply, L: Optical axis.

Claims (1)

[Scope of utility model registration request] The first and second deflection coils are arranged in a cylindrical space surrounded by an objective lens yoke, and the electron beam transmitted through the sample is incident thereon, and the first and second deflection coils are arranged in the space. a deflection current of the first deflection coil and the electromagnetic lens for deflecting the electron beam rotated by the electromagnetic lens to proceed along the optical axis; Transmission scanning electron microscope characterized in that it comprises means for supplying a deflection current to said second deflection coil in relation to an excitation intensity of said second deflection coil.