Hitachi-high-technologies Corporation

Hitachi, Ltd.

Okinawa Institute of Science and Technology Promotion Corporation

Takaho Yoshida

Takeshi Kawasaki

Hideo Todokoro

Yoichi Ose

Tomonori Nakano

Hisanao Akima

Hiroto Kasai

Yoichi Hirayama

High expectations are placed on aberration correctors to increase the resolving power of charged particle devices. Meanwhile, a far more complicated configuration and higher mechanical precision assembly in comparison to prior art aberration correctors are necessary in charged particle beam optical devices that use low-energy electron beams. A complex electromagnetic quadrupole part employed in the aberration corrector preferably has the forward extremities of the poles provided in a vacuum near an electron beam path and excitation coils disposed outside the vacuum, and this necessitates a structure that can achieve both electrical insulation and vacuum sealing for each of these poles. Such structural complexity generally conflicts with improving mechanical assembly precision. The complicated structure in the above problems can be simplified by: separating the electrodes and the magnetic poles in the complex electromagnetic multipole that had been used in prior art aberration correctors; and offsetting the positions of both, or ensuring that the widths of both do not match. Consequently, improvement of mechanical assembly precision can be achieved.

Charged particle beam apparatus and aberration corrector

The present invention provides a method and apparatus for correcting an aberration in a charged-particle-beam device. The apparatus includes a charged-particle-beam source, a charged-particle optical system that irradiates a specimen with charged particles emitted from the charged-particle-beam source, an aberration corrector that corrects an aberration of the charged-particle optical system, a control unit that controls the charged-particle optical system and the aberration corrector, a through-focus imaging unit that obtains plural Ronchigrams in which a focal position of the charged-particle optical system is changed, and an aberration calculation unit that divides the obtained Ronchigram into plural local areas, and calculates the amount of the aberration based on line focuses detected in the local areas.

Charged-particle-beam device and method for correcting aberration

Beam scanning for obtaining a scanned image is performed by an aberration corrector, which is an aberration measured lens, and a scanning coil disposed above an objective lens, instead of a scanning coil ordinarily placed on the objective lens. Thus, distortion with an aberration of an aberration measured lens is scanned on the surface of a sample, and then a scanned image is formed from a scattered electron beam, a transmission electron beam, or a reflected/secondary electron beam that is generated by the scan, achieving a scanning aberration information pattern equivalent to a conventional Ronchigram. Such means is a feature of the present invention.

Charged particle optical equipment and method for measuring lens aberration

Disclosed is a scanning transmission type electron microscope provided with a scanning transmission electron microscope provided with an aberration correctorfor correcting the aberration of an electron-optical system that irradiates electron beams to a sample (); a bright field image detector () for detecting electron beams that have transmitted through the sample; a camera (); and an information processing apparatus () for processing signals detected by the detectors. The information processing apparatus divides a Ronchigram obtained by the detectors into a plurality of areas, and calculates a feature vector (W;), which reflects the magnitude and direction of an on-axis secondary comma aberration (B), from the values of an off-axis defocus {C(&#x3c4;)} to be obtained for each of the plurality of areas, and the distance (&#x3c4;) from the center of the Ronchigram to the center of the plurality of areas, and also calculates the correcting condition for the on-axis secondary comma aberration with the feature vector. In such a way, a scanning transmission type electron microscope that can correct he on-axis secondary comma aberration thereof in a short period of time, and efficiently, was able to be provided.

Scanning transmission type electron microscope

To provide an aberration correction configuration that can realize both an aberration correction function for a long focus and an aberration correction function for a short focus. While having a conventional aberration correction apparatus configuration that has two rotationally symmetric lenses arranged between two multipole lenses, three rotationally symmetric lenses are disposed between an objective lens and a multipole lens instead of the conventional arrangement in which two rotationally symmetric lenses are disposed therebetween. When using the objective lens with a long focal length, aberrations are corrected using two rotationally symmetric lenses among three rotationally symmetric lenses disposed between the objective lens and the multipole lens. When using the objective lens with a short focal length, e.g. for high resolution observation, aberrations are corrected using two rotationally symmetric lenses of a different combination to those used for a long focus, among the three rotationally symmetric lenses disposed between the objective lens and the multipole lens. (See FIG.)

Aberration correction apparatus that corrects spherical aberration of charged particle apparatus

An electron beam apparatus with an aberration corrector using multipole lenses is provided. The electron beam apparatus has a scan mode for enabling the operation of the aberration corrector and a scan mode for disabling the operation of the aberration corrector and the operation of each of the aberration corrector, a condenser lens, and the like is controlled such that the object point of an objective lens does not change in either of the scan modes. If a comparison is made between the secondary electron images of a specimen in the two modes, the image scaling factor and the focus remain unchanged and evaluation and adjustment can be performed by distinctly recognizing only the effect of the aberration corrector. This reduces the time required to adjust an optical axis which has been long due to an axial alignment defect inherent in the aberration corrector and an axial alignment defect in a part other than the aberration corrector which are indistinguishably intermingled with each other.

Electron beam apparatus with aberration corrector

A crystal thin film is adopted as a specimen for measurement. A change in the contrast of crystal lattice fringes is measured under a condition that a diffracted wave and other wave are caused to interfere with each other. Thus, an information transfer limit of a transmission electron microscope can be measured quantitatively. Since the measurement is performed with a condition for interference restricted, the information transfer limit of the transmission electron microscope can be quantitatively assessed.

Method for measuring information transfer limit in transmission electron microscope, and transmission electron microscope using the same

When an accelerating voltage and operating distance are changed, an excitation current and a pole voltage of an aberration corrector must also be changed. Moreover, different multipole voltages or currents must be added individually for each pole in order to superpose multipoles. In view of overcoming the problems explained above, the charged particle optical apparatus of the present invention comprises an excitation device including, to give excitation to form a multipole field to each pole of the multipole lens, electromagnetic type quadrupole of four stages arranged along an optical axis of charged particle beam, electromagnetic type quadrupole of two stages for superposing distribution of voltage similar to distribution of magnetic potential of the electromagnetic type quadrupole of two stages at the center of the electromagnetic type quadrupole of four stages, and electromagnetic type octupole for superposing magnetic potential at least to three multipoles among that of four stages and also comprises a first power supply group for driving the same excitation device and a second power supply group for impressing voltages.

Charged particle optical apparatus with aberration corrector

A scanning electron microscope includes an electron gun to generate an electron beam, and an electron optical system directing the electron beam to a specimen. The electron optical system includes an objective lens that converges the electron beam to a surface of the specimen, an aberration corrector disposed between the electron gun and the objective lens so as to at least compensate for aberration caused by the objective lens, and a tilter which tilts electron beam to be incident into the aberration corrector. The aberration corrector further compensates for aberration caused by the tilter.

Charged particle beam column

A transmission electron microscope has a means for inputting a spatial size or distance d desired to be observed by the operator, calculates high contrast of an image based on this value and an observing condition which can reduce the influence of a false image superimposed, and desirably modulates an accelerating voltage of the electron microscope based thereon.

Transmission electron microscope

The present invention provides a charged particle beam column that does not cause displacement of an image or degradation of a resolution of images when a charged particle beam is tilted at a large angle. In the charged particle beam column including an aberration corrector, a deflector is used to control the direction of incidence of the charged particle beam on a second condenser lens but the object point of a condenser lens is not shifted. Consequently, the converging charged particle beam is tilted at a large angle with respect to the surface of a specimen without the necessity of shifting the object point of an objective lens lying on the optical axis of the charged particle beam column. At this time, the aberration corrector prevents a shift of an image or degradation of a resolution derived from the tilt of the charged particle beam.

The present invention provides an aberration corrector functioning under a condition outside the setting optical condition of an incorporated charged particle beam apparatus. An intermediate potential region different from the ground potential of an aberration corrector is provided in the space between the stages of multipole lenses constructing the aberration corrector to adjust a potential. Using this, when selecting an incident (outgoing) condition, an outgoing (incident) condition can be adjusted.

Growing community of inventors

Higashimatsuyama, Japan

Takaho Yoshida