JPH06192858A - Focused ion beam generator - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a focused ion beam generator that performs uniform etching by changing the scanning speed of the focused ion beam even if substances having different sputter rates are mixed. [Structure] Focused ions for etching by scanning the ion beam on the surface of the sample 7 utilizing a sputtering phenomenon generated by irradiating the surface of the sample 7 with the ion beam emitted from the ion source 1 through an optical system. In the beam generator, a sputter particle detector 9 for detecting sputter particles emitted from the surface of the sample 7 during the scanning of the ion beam, and a sputter rate discriminating unit for discriminating the sputter rate based on the detection signal of the sputter particle detector 9. 10 and a speed / velocity control unit 11 that controls the scanning speed of the ion beam according to the output signal of the sputter rate determination unit 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focused ion beam generator having a function of etching a specific minute area of a sample.

[0002]

2. Description of the Related Art FIG. 5 is a sectional view showing the structure of a typical conventional focused ion beam generator. In the figure, 1 is an ion source, 2 is a condenser lens, 3 is a movable diaphragm, 4 is a stigmator, 5 is an objective lens, and the ion beam emitted from the ion source 1 passes through these optical systems 2-5. The surface of the sample 7 focused and placed on the sample table 8 is scanned by the XY deflector 6.

By using the focused ion beam generator having the above structure, it is possible to etch a specific minute region on the sample surface, for example, a specific minute region such as a semiconductor element, by utilizing the spattering phenomenon of the ion beam. . Then, it is possible to observe the cross section of the opening portion of the specific minute area where the semiconductor element or the like has been opened by etching with a scanning ion microscope or a scanning electron microscope.

For example, FIG. 6 is a schematic cross-sectional view when an etching hole is formed by using a focused ion beam generator in order to observe a cross section of a specific minute region such as a semiconductor element. The focused ion beam 12 is applied to a sample 7. Is irradiated to form an etching hole. Further, FIG. 7 is a schematic diagram when observing the cross section 13 of the opening using a scanning ion microscope or a scanning electron microscope (not shown) after the etching opening. In FIG. 7, in the case of a scanning ion microscope, the sample 7 is irradiated with an ion beam as the primary beam 14, and in the case of a scanning electron microscope, the sample 7 is irradiated with an electron beam as the primary beam 14 to obtain a secondary beam from the sample 7. The electrons 15 are emitted.

[0005]

Since the conventional focused ion beam generator is constructed as described above, when the sample 7 such as a semiconductor element is made of a plurality of materials, etching is performed depending on different materials. There is a difference in rates,
As shown in FIG. 7, the low etching rate substance remains as an etching residue 17 at the desired etching location even after the local opening is performed for observing the cross section, and the field of view is observed when observing the cross section by the etching residue 17. There was a problem of hindrance.

For example, as shown in FIG. 8, when the surface of the sample 7 is made of SiO ₂ and W which are substances having different compositions, S
Comparing the sputtering rate of iO ₂ and W, large it compared to SiO ₂ of W, and that of SiO ₂ in the opposite small compared to W. Therefore, when etching is carried out by irradiation with the focused ion beam 12, as shown in FIG. 9, an etching residue 17 is generated in W, which obstructs the visual field when observing a cross section.

The present invention has been made to solve the above problems, and enables uniform etching even in the case of locally forming holes of a material composed of a plurality of substances having different sputtering rates. The purpose is to obtain a focused ion beam generator.

[0008]

A focused ion beam generator according to the present invention utilizes a sputtering phenomenon generated by irradiating a sample surface with an ion beam emitted from an ion source through an optical system. In a focused ion beam generator that performs etching by scanning the surface with an ion beam, a sputter particle detector that detects sputter particles emitted from the sample surface during ion beam scanning and a detection signal of this sputter particle detector It is characterized by comprising a sputter rate discriminating section for discriminating the sputter rate on the basis of the sputter rate and a scanning speed control section for controlling the scanning speed of the ion beam according to the output signal of the sputter rate discriminating section.

[0009]

In the focused ion beam generator according to the present invention, the sputtered particle detector detects sputtered particles emitted from the sample surface during the scanning of the ion beam, and the sputter rate discrimination unit detects the detection signal of the sputtered particle detector. The sputter rate is determined based on the. And
The scanning speed control unit controls the scanning speed of the ion beam according to the output signal of the sputter rate determination unit, and uniform etching is possible even when locally forming a material composed of a plurality of substances with different sputter rates. To

[0010]

【Example】

Example 1. FIG. 1 is a block diagram showing a focused ion beam generator showing an embodiment of the present invention. In the figure,
8 is the same as the conventional device described above. That is,
1 is an ion source, 2 is a condenser lens, 3 is a movable diaphragm,
Reference numeral 4 is a stigmator, 5 is an objective lens, and the ion beam emitted from the ion source 1 is used in these optical systems 2-5.
The sample is focused on the surface of the sample 7 by the XY deflector 6.

Reference numeral 9 denotes a sputtered particle detector for detecting the composition of sputtered particles, which is used when the surface of the sample 7 is irradiated with a focused ion beam when the sample surface is etched by the ion source 1 and the optical systems 2 to 5. Sample atoms in the vicinity of the surface of 7 obtain a part of the energy of incident ions and are emitted to detect sputtered particles at the time of sputtering. As a detection signal, secondary ions generated by ion beam irradiation, or Neutral particles generated by sputtering may be ionized, or Auger electrons excited by ion beam irradiation or electromagnetic waves such as characteristic X-rays and visible ultraviolet light may be used. For example, in the case of characteristic X-rays, energy corresponding to the sputtered particles may be used. Detect intensity.

Reference numeral 10 denotes a sputter rate discriminating section for discriminating the sputter rate based on the detection signal of the sputtered particle detector 9, and the composition can be analyzed from the detection signal, for example, the signal according to the energy intensity, and the composition is uniform. A voltage signal with a sputter rate according to the composition is output to advance the etching. A scanning speed control unit 11 controls the XY deflector 6 to enable the scanning speed of the focused ion beam on the surface of the sample 7 according to the voltage signal, and together with the sputtered particle detector 9 and the sputter rate determination unit 10. A scanning velocity control system for the focused ion beam is constructed, and these components operate in synchronization with the scanning of the focused ion beam.

Next, the operation of the above configuration will be described. For example, as shown in FIG. 2, when the focused ion beam 12 is scanned in the reciprocating direction of the arrow on the surface of the sample 7 made of the substances M ₁ and M ₂ (7a, 7b) having different sputter rates, the substance M _By detecting the particles sputtered from ₁ and M ₂ respectively by the sputtered particle detector 9, detection signals I _M1 and I _M2 (see FIG. 2) corresponding to the substances M ₁ and M ₂ are obtained. It is possible to analyze the composition of the sample 7, and the information is sent to the sputter rate judging section 10 to judge the sputter rate. Then, a voltage signal corresponding to the sputter rate of the composition is output from the sputter rate determination unit 10.

The scanning speed control unit 11 to which the voltage signal from the sputter rate determination unit 10 is input controls the XY deflector 6 so as to make the scanning speed variable according to the voltage signal, and the different substance M of the sample 7 is controlled. Etching is allowed to proceed uniformly between ₁ and M ₂ .

[0015] For example, by comparing the sputtering rate of the materials M ₁ and M ₂ in FIG. 2, when it material M ₁ is assumed to be larger than the material M _2, in the region of the material M _1, a focused ion beam 12 The scanning speed of the focused ion beam 12 is slowed down so that the scanning speed of the focused ion beam 12 is slowed down in the area of the material M _{2 because} the sputter rate is smaller than that of the material M _1. To do.

Therefore, according to the above configuration, even if there are substances having different sputter rates, uniform etching is possible, and etching holes can be easily observed even when observing a local cross section.

FIG. 3A shows a focused ion beam generator having a function capable of automatically varying the scanning speed of the focused ion beam 12 in order to observe a cross section 13 of a specific minute region of a sample 7 such as a semiconductor device. Fig. 3 is a schematic sectional view of a sample in which an etching hole is formed so that a substance having a low etching rate does not remain, and Fig. 3 (b) shows a scanning ion microscope or a scanning electron microscope after the etching hole is formed. A schematic view of observing the cross section 13 based on the secondary electrons emitted from the open hole sample 7 by the irradiation of the primary beam 14. The etching open hole is easily observed because no etching residue remains as in the conventional example. To be done.

Further, FIG. 4A shows an extremely thin region (observation cross section 1).
FIG. 4B is a schematic cross-sectional view when both sides of this remaining region are etched to leave 3), as shown in FIG.
After etching as in (a), the cross section of the opening is observed based on the transmitted electrons 16 using a transmission electron microscope.

[0019]

As described above, according to the present invention, the sputter particle detector for detecting the sputter particles emitted from the sample surface during the scanning of the ion beam, and the sputtering based on the detection signal of the sputter particle detector. Since the sputtering rate discriminating unit for discriminating the rate and the scanning speed control unit for controlling the scanning velocity of the ion beam according to the output signal of the sputter rate discriminating unit are provided, it is possible to detect the substance sputtered by the irradiation of the focused ion beam. The composition is detected, the sputter rate of the sputtered substance is recognized from the information, and the beam scanning speed can be automatically changed so that the etching proceeds uniformly even if the composition of the substance changes. Even when a substance composed of a plurality of different materials is used to locally open a hole with this device, the etching rate is delayed in the etching hole. There is an effect such material does not remain.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a focused ion beam generator according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram illustrating the operation of FIG.

3A and 3B are a schematic diagram when an etching hole is formed and a schematic diagram when observing a cross section of the hole using the focused ion beam generator of FIG. 1 for observing a cross section of a specific minute region.

4A and 4B are schematic diagrams when a sample for observation is prepared and observed by a transmission electron microscope using the focused ion beam generator of FIG.

FIG. 5 is a configuration diagram of a focused ion beam generator of a conventional example.

FIG. 6 is a schematic diagram when an etching hole is formed by using a conventional focused ion beam generator for observing a cross section of a specific minute region.

FIG. 7 is a schematic diagram when observing a cross section of an aperture using a conventional focused ion beam generator.

FIG. 8 is an explanatory diagram of a problem during etching when the composition of the substance on the sample surface is different.

9 is an explanatory diagram of an etching residue during the etching of FIG.

[Explanation of Codes] 1 ion source 6 XY deflector 7 sample 9 sputtered particle detector 10 sputter rate controller 11 scanning speed controller

[Procedure amendment]

[Submission date] May 11, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

For example, as shown in FIG. 8, when the surface of the sample 7 is made of SiO ₂ and W which are substances having different compositions, S
Comparing the sputtering rates of iO ₂ and W, that of W is smaller than that of SiO ₂ , and conversely, that of SiO ₂ is greater than that of W. Therefore, when etching is carried out by irradiation with the focused ion beam 12, as shown in FIG. 9, an etching residue 17 is generated in W, which obstructs the visual field when observing a cross section.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 21/302 D 9277-4M

Claims (1)

[Claims] 1. A focused ion beam for etching by scanning an ion beam on a sample surface by utilizing a sputtering phenomenon generated by irradiating the sample surface with an ion beam emitted from an ion source through an optical system. In the generator, a sputter particle detector that detects sputter particles emitted from the sample surface during ion beam scanning, and a sputter rate determination unit that determines the sputter rate based on the detection signal of this sputter particle detector,
A focused ion beam generator, comprising: a scanning speed control unit that controls a scanning speed of an ion beam according to an output signal of the sputtering rate determination unit.