JPH0448627Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a focused ion beam device that is effective for use in high-precision ion beam lithography and the like.

[Prior Art] A focused ion beam device used in ion beam lithography generally uses a two-stage focusing lens system. This is because it is preferable to install a blanking deflection electrode or an ExB mass filter at the position of the crossover image of the ion beam. FIG. 5 is an optical diagram of a conventional focused ion beam device, in which reference numeral 1 indicates, for example, a field emission type ion source. The ion beam emitted from this ion source is focused by an electrostatic focusing lens 2, and forms an image CO of a crossover point formed near the ion source 1 between the ion beam and the objective lens 3. The ion beam diverging from this crossover image CO is reduced and imaged by the next objective lens 3, and is irradiated onto the sample 4 as a minute spot. A deflection electrode 5 that can deflect ions in any direction is arranged on the sample 4, and if a pattern signal is supplied to this deflection electrode from a computer (not shown),
A desired ion beam can be used to write on the sample. This deflection electrode is also used for checking the ion optical system, and as shown in the figure, a surface scanning signal is supplied from a two-dimensional scanning signal generating circuit 6. A secondary electron detector 7 is arranged above the sample 4, and detects secondary electrons generated from the sample when the sample is irradiated with an ion beam, and is sent to a display device such as a cathode ray tube via an amplifier 8. 9 as a luminance signal. A deflection electrode 10 for blanking is arranged at the position of the crossover image CO, and a desired voltage signal is sent from a blanking power supply 11. An aperture plate 12 having a minute opening is placed directly below the blanking deflection electrode to block the ion beam. Denoted at 13 and 14 are two-stage alignment deflection electrodes, and by adjusting the alignment power supply 15, the ion beam can be aligned.

In such a configuration, in a general device, the magnification of the focusing lens 2 is approximately 1, and the magnification of the objective lens is approximately 1.
It is about 0.3 to 0.5, and the crossover diameter is calculated to be 0.1 μm or less in diameter. Therefore, the size of the crossover image CO generated between lenses 2 and 3 is also about the same, and the objective lens reduces this to 1/2 to 1/3 and projects it onto the sample. Including aberrations, a spot diameter of 0.1 μm can be theoretically obtained. However, in reality, due to misalignment of the axes of the ion source and each lens, the above crossover image
The CO spot diameter may be larger than the above and far exceed the amount of aberration of the objective lens. With this, even if you reduce the size using an objective lens, you will not be able to narrow it down to 0.1 μm. In order to confirm the spot diameter, a monitor device consisting of the deflection electrode 5, a scanning power source 6, a secondary electron detector 7, and a cathode ray tube 9 is provided, which displays a secondary electron image and determines the spot diameter from the image. That's what I do.

[Problems that the invention aims to solve] However, since such a device only knows the final ion beam spot diameter, it is difficult to distinguish even if the intermediate crossover image is larger than the predetermined spot diameter due to poor alignment, etc. However, it was extremely difficult to reduce the spot diameter of the beam projected onto the sample to 0.1 μm or less.

Therefore, in view of the above points, the purpose of the present invention is to provide a focused ion beam device that can easily check the size of the intermediate crossover image and narrow down the final spot on the sample to a desired size. That's true.

[Means for Solving the Problems] The present invention includes an ion source, at least two stages of focusing lenses for focusing the ion beam from the ion source, and a crossover image formed between the lenses. an aperture plate having a minute aperture arranged at a position, a blanking deflection electrode or an ExB mass filter placed above the aperture plate, and a secondary electron detector also placed above the aperture plate; means for relatively moving the scanning position of the ion beam and the aperture plate in order to change the irradiation position of the ion beam on the aperture plate; and means for surface-scanning a desired area on the aperture plate with the ion beam; A focused ion beam device comprising a display device that displays a scanned image based on a detection signal obtained from the secondary electron detector during surface scanning has a structural feature.

[Example] Fig. 1 is an optical diagram of an embodiment of the present invention, and Fig. 5 is an optical diagram of an embodiment of the present invention.
The same reference numerals as in the figures indicate similar members. 16 is an aperture plate having a minute opening, and is placed at the position of the crossover image CO. A deflection electrode for blanking is placed above this aperture plate, and the blanking electrode ₁₁ ,
Alternatively, it is connected to the DC power supply 17 for shifting.
A second blanking deflection electrode 18 and an aperture plate 19 are installed below the aperture plate 16, and a blanking signal is applied to this electrode 18 in synchronization with the first blanking electrode 10. . If two stages of blanking deflection electrodes are provided across the crossover image CO in this way, the effect will be similar to that of placing the deflection electrodes exactly at the position of the crossover image, and the ions on the sample during blanking will be Deterioration of pattern accuracy due to beam positional deviation can be prevented. A plurality of secondary electron detectors 20 are arranged above the aperture plate 16 (below the blanking electrode 10) in an annular shape or around an ion path.
Detect secondary electrons generated from above. For example, a multi-channel plate (MCP) is used as this detector, and its output is subjected to appropriate signal processing and supplied as a brightness modulation signal to the cathode ray tube 9 via the amplifier 21 and the switch _S2 . A secondary electron detector 7 from the sample is connected to the a terminal of this switch, and the switch is configured so that signals from both detectors can be selectively supplied to the cathode ray tube. 22 is an adder which adds the alignment signal from the alignment circuit 15 and the surface scanning signal from the scanning signal generation circuit 6 supplied via the switch S ₃ and supplies the result to the deflection electrodes 13 and 14.

With this configuration, all switches S ₁ to _{S 3} are set to a
When connected to the terminal, it will be in the same state as shown in Figure 5,
An image of secondary electrons from the sample 4 detected by the detector 7 can be observed on a cathode ray tube. Next, when the switch S ₁ is switched to the b terminal, the DC power supply 17 is connected to the blanking deflection electrode as shown in Fig. 2.
A constant voltage is applied from , and the scanning position of the ion beam is shifted to a predetermined position on the aperture plate 16 . In this state, when the switch _S3 is switched to the b terminal, the surface scanning signal from the scanning power supply 6 is supplied to the alignment deflection electrode via the adder 22, and only the center beam is shown in FIG. As shown in FIG. 2, the ion beam whose scanning position has been shifted scans a certain area on the aperture plate 16. The secondary electrons emitted from each point on the aperture plate by scanning the ion beam are detected by the detector 20, appropriately amplified by the amplifier 21, and further subjected to appropriate signal processing (not shown) before being transmitted via the switch _S2 . Supplied to the cathode ray tube. As a result, an image obtained by scanning the intermediate crossover image on the aperture plate is obtained, so that the state of the crossover image can be confirmed from the image, and alignment failures and other deficiencies in the optical system can be detected. Therefore, by adjusting each part so that this crossover image is minimized, it becomes possible to finally project an ion beam with a minute beam spot diameter (0.1 μm or less) onto the sample.

In the above, it goes without saying that it is convenient to link two or more of the switches _S1 to _S3 . In addition, in place of the blanking electrode or in combination with the above blanking electrode, E
It can also be used in the same way for devices using ×B mass filters. In this case, it is highly effective to provide two stages of E×B mass filters with the aperture plate 16 in between. Furthermore, in order to shift the scanning position of the ion beam to a desired position on the aperture plate 16, a shift voltage from the DC power source 17 is applied to the blanking deflector in FIG. Deflection electrodes may also be used. Furthermore, instead of using such electrical shifting, the standard sample 23 is attached to an arbitrary position on the aperture plate as shown in FIG. The fine aperture and the standard sample may be selectively placed in the ion beam path by mechanically moving the reference sample.
Furthermore, although the above embodiment uses two stages of lenses for focusing the ion beam, it is possible to use a larger number of lenses in the same way.

[Effect] As explained above, in the present invention, an aperture plate having a minute aperture is placed at the position of the crossover image formed in the middle of the focusing lens, and two
At the same time as the secondary electron detector is arranged, the ion beam is scanned over the desired area of the aperture plate, and the resulting secondary electrons from each part are detected and displayed as an image. The focusing state of the intermediate crossover image can be easily and accurately confirmed from the image, and alignment and other adjustments can therefore be made extremely accurately, allowing the ion beam to have the desired minute spot diameter to be placed on the sample. This makes it possible to perform highly accurate ion beam lithography.

[Brief explanation of the drawing]

Fig. 1 is an optical diagram showing one embodiment of the present invention;
3 and 3 are explanatory diagrams thereof, FIG. 4 is a diagram showing another embodiment of the present invention, and FIG. 5 is an optical diagram showing a conventional device. 1... Ion source, 2... Focusing lens, 3... Objective lens, 4... Sample, 5... Deflection electrode, 6...
Scanning signal generation signal, 7... Secondary electron detector, 8...
...Amplifier, 9...Cathode ray tube, 10...Blanking deflection electrode, 11...Blanking power supply, 12
... Aperture plate, 13, 14 ... Deflection electrode for alignment, 15 ... Scanning circuit, 16 ... Aperture plate, 17 ... DC power supply, 18 ... Second deflection electrode for blanking, 19 ... Aperture plate ,2
0...Secondary electron detector, 21...Amplifier, 22...
...adder.

Claims (1)

[Claims for Utility Model Registration] (1) An ion source, at least two stages of focusing lenses for focusing the ion beam from the ion source, and an arrangement at a position of a crossover image formed between the lenses. an aperture plate having a minute aperture, a blanking deflection electrode or an ExB mass filter placed above the aperture plate, a secondary electron detector also placed above the aperture plate, and a secondary electron detector placed above the aperture plate; means for relatively moving the scanning position of the ion beam and the aperture plate in order to change the irradiation position of the ion beam on the ion beam; means for surface-scanning a desired area on the aperture plate with the ion beam; A focused ion beam device comprising a display device that displays a scanned image based on a detection signal obtained from the secondary electron detector. (2) The focused ion beam device according to claim 1, wherein the blanking deflection electrode or the E×B mass filter is also installed behind the aperture plate. (3) The focused ion beam device according to claim 1 or 2, wherein the scanning signal of the surface scanning is supplied to a deflection electrode for alignment arranged in the ion beam path. (4) The focusing system according to claims 1 to 3, wherein a constant voltage is applied to the blanking deflection electrode in order to move the scanning position of the ion beam to a desired area on the aperture plate. Ion beam device. (5) Utility model registration claims 1 to 3, wherein the aperture plate is mechanically moved in a direction perpendicular to the ion beam in order to move the scanning position of the ion beam to a desired area of the aperture plate. Focused ion beam device.