JPS59229519A - Scanning photon microscope - Google Patents

Abstract

PURPOSE:To permit detection of the temp. distribution on the surface of an object to be observed and easy analysis of a defect accident with high resolving power by scanning the surface of said object with a photon beam and detecting the photoelectron from the object. CONSTITUTION:The electron beam 6 from an electron gun 5 is converted to pulses by a combination of a pulse power source 26, a blanking plate 7 and a blanking aperture 8. The pulses are converged by an electron lens 9 and are irradiated onto a plate 11 on which a fluorescent material 11'is coated. The photon beam 13 generated by the plate 11 is converged by a lens 12 and is irradiated to a solid state circuit element 14. The scanning of the beam 13 is accomplished by deflecting the beam 6 with a coil 10. When the element 14 is locally heated owing to a short circuit accident or the like, a radiation of photoelectron arises and the output signal from a detector 19 is supplied via a signal processing circuit to a display tube 27, by which the temp. distributing condition is made visible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a scanning photon microscope that scans a photon beam to obtain a microscopic image.

[Background of the invention]

A scanning photon microscope is a scanning electron microscope that replaces electrons with photons, and is not new in itself. However, unlike electron microscopes, conventional scanning photon microscopes are not used in a vacuum;
Microscopic images are obtained using reflected light and scattered light from a sample in the atmosphere. If the sample is a semiconductor, transmitted light is also used,
Furthermore, it is widely practiced to use photovoltaic force or photocurrent generated in a sample as a signal.

In principle, it is possible to use photoelectron radiation as a signal source for scanning images. However, for photoelectron emission, the energy of the light must exceed the work function of the object to be irradiated. For example, if the object is Al (work function φ'': 4 eV).

The wavelength of the light is in the ultraviolet region of 310 nm or less. Conversely, photons in the visible range with wavelengths of violet (~36Qnm) or longer have a small work function such as cesium (φγ1.6
Photoelectrons cannot be expected except in the case of materials with

Therefore, when using photons in the visible and infrared regions,
In many cases, photoelectrons cannot be detected. Therefore, in conventional scanning photon microscopy, there is no reason why the sample must be placed in a vacuum; all samples are placed in the atmosphere.

As a result, there has never been a scanning photon microscope that scans the surface of an object housed in a vacuum using a photon beam with an energy that does not exceed the work function of the object to obtain a microscopic image.

[Purpose of the invention]

Therefore, an object of the present invention is to scan the surface of an object to be observed housed in a vacuum using a photon beam with an energy not exceeding the work function of the object to be observed, thereby making it possible to obtain a microscopic image. To provide a photon microscope.

[Summary of the invention]

In order to achieve the above object, the scanning photon microscope according to the present invention includes a vacuum container for containing an object to be observed, a photon source that faces the object to be observed and generates a photon beam, and a scanning photon microscope that uses the photon beam to expose the object to the object. The gist includes means for scanning the surface of the observed object, and a detector for detecting photoelectrons generated when the photons hit the observed object.

The present invention will be described in detail using FIGS. 1 and 2.

FIG. 1 shows the principle of the photoelectron generation mechanism using an energy diaphragm. When the object 1 is irradiated with photons 2° 2', the electrons 3 and 3' in the full band 1' in the energy level diagram of the object.

It receives energy from photons 2 and 2' and is excited. However, if the energy of photon 2.2' is less than the work function φ, then
The electrons 3.3' cannot escape into the vacuum space 4 outside the object.

On the other hand, if an object is heated for some reason.

The electrons in the filled zone 1' are excited and lifted to a high-energy state 1''. When such a state is irradiated with a photon 2'', as can be easily understood from FIG.

Electron 3" rises to an energy level above its work function.

As a result, they fly out into the vacuum space 4 as photoelectrons.

Therefore, when an object is heated, photoelectron emission becomes possible using photons with energy lower than the work function, and scanning images using these photoelectrons become possible.

[Embodiments of the invention]

FIG. 3 is a block diagram showing one embodiment of a scanning photon microscope according to the present invention. In this embodiment, the photon beam is pulsed. Extracting the signal in synchronization with the pulsed photon beam has the advantage of improving the signal-to-noise ratio. Although any light source may be used, FIG. 3 shows a case where an electron beam device used in a scanning electron microscope is applied to the light source.

It goes without saying that this light source can be replaced with a conventional laser or cathode ray tube.

In FIG. 3, an electron beam 6 is extracted from an electron gun 5, focused by an electron lens 9, and irradiated onto a fluorescent plate 11 coated with a suitable fluorescent substance 11'. In order to obtain a pulsed light source, a pulse voltage is applied to the blanking plate 7 from a pulse power source 26, and in combination with the blanking aperture 8, the electron beam 6 is pulsed and the fluorescent plate 11 is irradiated with the pulsed electron beam 6. The photon beam 13 generated by the fluorescent plate 11 passes through the lens 1
2 and irradiates the solid-state circuit element 14. Scanning of the photon beam 13 is automatically performed by deflecting and scanning the electron beam 6 with a deflection coil 1o. In the solid state circuit element 14.

A voltage is applied by the DC power source 16 through the electrodes 15, 15', and the device is kept operating under normal conditions.

If the solid state circuit element 14 is operating normally.

Although no photoelectrons are emitted from the element surface, one circuit element
Local heating, such as from a short-circuit accident, results in photoelectron emission for the reasons already explained. This electron is detected by the detector 19
A signal obtained by detection is amplified by an amplifier and supplied to a scanning image display tube 27 via a signal processing circuit 24. Since the electron beam (not shown) of the display tube 27 and the electron beam 6 are synchronously scanned by the deflection coil B via the scanning power supply n, two circuits are required as is well known in the case of a scanning electron microscope. The scanning photon image of the element 14 leaks onto the display tube 27,
If the heating is localized, the temperature distribution can be visually observed.

It is clear that photoelectrons may be detected by amplifying the terminal voltage of the detection resistor 17 between the two-circuit element 14 and the ground using the amplifier 8.

When there is no photoelectron emission (when there is no temperature rise in the circuit element 14), the circuit element 14 cannot be recognized by photoelectrons, but photons are reflected from the surface of the two-circuit element 14.

If the scattering is detected by the detector 21 and amplified by the amplifier 22, an image of the surface of the element can be obtained using this as a signal.

If a substance with a work function lower than the energy of the photon beam being used exists on the surface of the circuit element 14, photoelectrons can be detected even when the temperature of the circuit element 14 does not rise. According to the present invention, the presence of a specific substance can be detected. can be detected. This is because if the temperature of the circuit element 14 increases, the photoelectron emission from the specific substance increases.

It is clear that a temperature increase in that area can be identified.

When it is desired to change the wavelength of light, the fluorescent substance 11' is changed according to the purpose.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the temperature distribution on the surface of a solid-state circuit element can be detected using visible photons, which are easy to handle, and failure analysis becomes easy. Moreover, since the spatial resolution is based on the photon spot, a high resolution of around 1 μm can be achieved.

[Brief explanation of the drawing]

1 and 2 are energy level diagrams for detailed explanation of the present invention, and FIG. 3 is a block diagram showing the configuration of a scanning photon microscope according to the present invention. 1...Object 1'...Filled zone■“
...High energy state 2.2'...Photon 3.3'
, 3"...electron 4...vacuum space 5...electron gun 6...electron beam 7...blanking plate 8...blanking anno-cha 9...electron lens 10 ...deflection coil 1
1... Fluorescent plate 11 fluorescent substance 12
... Lens 13 ... Photon beam 14
...Solid circuit element 15, 15'゛°electrode 16-''DC power supply 17...Detection resistor 1
8.20.22...Amplifier 19...Photoelectron detector 21...Reflected and scattered photon detector B...Scanning power source Control...Signal processing circuit 5
...Deflection coil...Pulse power supply 27.
...Scanning Image Display Management Agent Patent Attorney Junnosuke Nakamura

Claims (1)

[Claims] a vacuum container for storing an object to be observed; a photon source that faces the object to be observed and generates a photon beam; and means for scanning the surface of the object to be observed with the photon beam;
and a detector for detecting photoelectrons generated when the photons hit the object to be observed.