JPH0528950A - Method and device for machining cross section - Google Patents

Abstract

PURPOSE:To enhance the accuracy of a position at which to form the cross section of a device so as to obtain an accurate cross section at a desired place with efficiency by utilizing a mask which is movable in vacuum state in machining the cross section of the device using a focused ion beam. CONSTITUTION:A rectangular hole 3 for enabling observation from the oblique direction of a cross section is formed in the surface of a substrate 2 such as LSI by using a focused ion beam 1. Next a mask 4 put on the end of a manipulator 5 is shifted to a finish cross section position by driving of the manipulator 5. Since a large quantity of secondary electrons are emitted from the end face of the mask, halation occurs at the end portion of the mask 4 against an effort to adjust a contrast on the surface of the sample and so accurate positioning is not possible. Therefore secondary electron signal intensity is compressed logarithmically to prevent halations to form a beam image which is easy to watch and to accurately set the cross section position. The mask 4 is formed by opening an Si crystal thin film while making the form of its end face good, and a strip shape cross section including the boundary of the mask 4 is finished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for processing a cross section of a device using a focused ion beam.

[0002]

2. Description of the Related Art The prior art is the Proceedings of International Reliability Physics Symposium, (1989) pp. 43-5.
Page 2 (Proceedings of International Reliability Phy
sics Symposium, (1989) pp.43-52).

[0003]

In the above-mentioned prior art, the device is processed using a focused ion beam for cross-section processing, and a scanning ion microscope image (Scanning Ion Microscope: SI for short) is used.
The image of the cross-sectional structure was observed using the M) function. FIG. 3 is an explanatory diagram of a processing procedure.

(1) A rough processing area is designated based on the SIM image.

(2) A rectangular hole is roughly processed with a beam having a current of 2 to 5 nA.

(3) Finishing is performed by scanning the vicinity of the observation cross section with a beam having a current of 400 pA. The prior art can be evaluated in that a plurality of beam currents (beam diameters) are selectively used and a cross section is efficiently formed. However, since the rough processing is first performed with a beam with a large beam diameter,
There is a drawback that it is difficult to accurately set the final cross-sectional position to a desired position. Further, since the beam diameter is made minute at the time of finish processing, processing is performed with a small beam current. Further, if the processing region drifts due to charge-up of the device or other reasons, there is a drawback that a cross section cannot be formed at an accurate position.

DRAM (Dynamic Random Access Memor)
As typified by y), miniaturization and high integration of semiconductors are rapidly advancing, and improvement of processing position accuracy is a problem in cross-section processing.

An object of the present invention is to improve the processing position accuracy of cross-section processing, to form a cross section at a desired position of a fine device, and to make it possible to observe the structure of the cross section.

[0009]

In order to achieve the above object, the processed cross section is processed by using a mask movable in vacuum.

[0010]

By using a mask when forming the cross section, a clean cross section can be formed by using a beam having a large beam diameter and a large beam current, so that processing can be performed at high speed. Further, when the band-shaped region including the mask end face is scanned and processed, even if the processed region drifts, the sectional position does not move as long as the drift amount is within the width of the band-shaped region. Therefore, the cross-sectional position can be set accurately.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram of the FIB processing apparatus used in the embodiment. The ion beam emitted from the liquid metal ion source 100 is focused on the sample substrate 2 by the condenser lens 101 and the objective lens 107. The beam acceleration voltage is 30 kV. A variable aperture 102, an aligner / stigmer 103, a blanker 104, a blanking aperture 105, and a deflector 106 are arranged between the lenses. The sample substrate 2 can be moved by the stage 108. Secondary electrons generated from the sample substrate 2 by FIB irradiation are detected and amplified by the secondary electron detector 109, and displayed as a SIM image on the CRT of the computer 111 by synchronizing with deflection control.

FIG. 1 is a device top view showing a cross-section processing procedure utilizing the present invention. Hereinafter, description will be made step by step.
(1) The sample substrate 2 (LSI substrate) is FIB-processed with the square hole 3 that allows observation from a diagonal direction of the cross section. (2)
The mask 4 mounted on the tip of the manipulator 5 is driven to move to the finishing cross-section position. At this time, since a large amount of secondary electrons are emitted from the mask end surface, if contrast is adjusted to the sample surface, halation occurs at the mask end portion, and accurate positioning cannot be performed. As a measure against this, the secondary electron signal intensity was logarithmically compressed. As a result, halation can be prevented, and accurate cross-sectional position setting can be performed using a SIM image that is easy to see. The mask used in this example was prepared by cleaving a silicon crystal thin film,
The end face shape of the mask is good. (3) A band-shaped region including the boundary line between the sample substrate 2 and the mask 4 is finished by FIB1. As a result, even if the processing region is slightly shifted due to charge-up or the like, a cross section can be formed at an accurate position (mask end face). Moreover, since it is not necessary to use a fine beam as a beam for finishing, there is an advantage that finishing can be performed at high speed with a large current. (4) The manipulator is driven to move and remove the mask 4. Since the cross section 6 is formed, the cross section can be observed.

In the present embodiment, sputtering processing by FIB irradiation was used, but in addition to this, FIB assist etching, electron beam assist etching, laser beam assist etching and the like can also be used in principle.
Assisted etching has a high processing speed, although the selectivity is greatly increased depending on the processing material. The cross-section processing described in this embodiment can be applied to, for example, semiconductor laser and end face processing of a waveguide.

[0014]

According to the present invention, the precision of the cross-section forming position in cross-section processing is improved, and the cross-section at a desired location can be efficiently and accurately formed.

[Brief description of drawings]

FIG. 1 is a perspective view showing a cross-section processing procedure according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a focused ion beam processing apparatus used in an example of the present invention.

FIG. 3 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

1 ... FIB, 2 ... Sample substrate, 3 ... square hole, 4 ... mask, 5
... manipulator, 6 ... observation section, 100 ... liquid metal ion source, 101 ... condenser lens, 102 ... variable aperture, 103 ... aligner stigmer, 10
4 ... Blanker, 105 ... Blanking aperture, 106 ... Deflector, 107 ... Objective lens, 10
8 ... Stage, 109 ... Secondary electron detector, 110 ... Manipulator, 111 ... Computer, 112 ... System bus.

Claims (4)

[Claims] 1. A processing method for forming a cross section in a device by using a focused ion beam (FIB), wherein the processed cross section is processed by using a mask movable in vacuum. Processing method. 2. The cross-section processing comprises at least rough processing of a hole that enables observation from an oblique direction of the cross section and finish processing for cutting out the observation cross section neatly, and the movable mask is used during the finish processing. The cross-section processing method according to claim 1. 3. The cross-section processing method according to claim 1, wherein the end face of the movable mask is a cleavage plane of a crystal. 4. A manipulator equipped with an ion source, an ion optical system for focusing and deflecting an ion beam emitted from the ion source on a sample, a FIB control system for irradiating the ion beam at a desired location with a desired intensity, and a movable mask. A cross-section processing device comprising: