Method for improving analysis conductivity of FIB-material

Abstract

A method for improving FIB-material analysis conductivity comprises the following steps that a target area is found in a scanning electron microscope mode, a sample table is tilted to prepare to conduct protective layer deposition under an ion beam, a nano manipulator is stretched into the sample table to enhance conductivity and assist deposition before the protective layer deposition, and the target area is obtained. The method comprises the following steps: roughly cutting and finely cutting a target area by using an ion beam to obtain a target section, returning to a nano manipulator, adjusting the position of an observation section area under a scanning electron microscope, and stretching into the nano manipulator before shooting to enhance the conductivity and improve the quality of a shot picture. The method utilizes the conductivity of the nano manipulator to effectively improve the aggregation of charges on the surface of the sample. Therefore, the phenomenon of image drift is avoided during W plating and rough cutting under the ion beam, so that accurate W plating and rough cutting in a target area can be realized, and the quality of a cross-section shot image is improved. The method is simple to operate and high in precision, has the effect of rapidly improving the conductivity of the sample, and has very high practicability.

Description

Technical Field

[0001] The invention relates to the field of semiconductor chip manufacturing, and in particular to a method for improving conductivity of FIB-material analysis. Background Art

[0002] With the development of science and technology, the requirements for characterizing the microstructure of materials have also increased. Focused ion beam (FIB) is based on a scanning electron microscope with an ion beam column added and equipped with a nanomanipulator. Its working principle is to first use a high-energy ion beam to cut a specific analysis position of the material to prepare a cross section, and then use a high-resolution scanning electron microscope to photograph and analyze the micro-nanostructure of the cross section at a specific position.

[0003] Compared with conductor materials, materials with poor conductivity have serious charging effects, which make FIB processing more difficult. The charging effect will cause the image to be blurred or even offset, which makes it impossible for the FIB ion beam to accurately locate and process. At present, the method to improve the conductivity of the sample is generally to coat a layer of conductive metal film on the surface of the sample before testing to eliminate the charging effect. However, during slicing, the continuous irradiation of the ion beam will etch the metal film on the surface, thereby losing its conductive function. Summary of the invention

[0004] The purpose of the present invention is to provide a method for improving the conductivity of FIB-material analysis. The method utilizes the conductivity of the nanomanipulator to export the accumulated electrons, thereby reducing the charging effect and effectively solving the image drift problem, thereby enabling precise positioning during slicing, improving slicing efficiency and the final cross-sectional image quality.

[0005] To achieve the above object, the present invention provides a method for improving the conductivity of FIB material analysis, characterized in that it comprises the following steps: (1) The target area found in scanning electron microscopy (SEM) mode; (2) Tilt the sample stage to prepare for protective layer deposition under the ion beam; (3) Extending the nanomanipulator to enhance conductivity and assist deposition; (4) Deposition of protective layer in target area; (5) Using an ion beam to perform rough and fine cutting on the target area to obtain a target cross section; (6) Retract the nanomanipulator and adjust the position of the cross-sectional area for observation under the scanning electron microscope; (7) Before taking pictures, insert the nanomanipulator to enhance the conductivity and improve the quality of the pictures.

[0006] In step (1), the SEM mode will obtain a magnified image of the sample surface and move the field of view to different places to find the target area. In step (2), the sample stage is tilted to 50-60°, which may be slightly different for other types of equipment.

[0007] In step (3), under the ion beam window, the voltage is 20-30kV, the beam current is 80-430pA, and the nanomanipulator enters and stops moving instantly after contacting the FIB material surface. It does not move when it contacts the FIB sample surface, and is fixed when the nanomanipulator is not operated.

[0008] The front end of the nanomanipulator is provided with a metal probe, the metal probe is selected from W, and the needle handle of the metal probe is any one of tungsten, nickel or stainless steel.

[0009] The front end of the nanomanipulator is made of metal tungsten, which has good conductivity. When it touches the surface of the sample, it can extract the charge accumulated on the surface of the sample (the surface of samples with poor conductivity will continue to accumulate charge when scanning).

[0010] In step (4), continue to enter the tungsten needle under the ion beam window with a voltage of 20-30 kV and a beam current of 80-430 pA, and perform W deposition in the target area to obtain a target area protected by a W layer.

[0011] The deposition thickness is 0.5-1 μm, and the target area protected by W is 2-5 μm in length and 1-3 μm in width.

[0012] In step (5), at a voltage of 20-30 kV and a beam current of 0.79-9.3 nA, a rough cut is performed below the target area protected by W using an ion beam to obtain a target cross section after rough cutting; and further at a voltage of 20-30 kV and a beam current of 40-230 pA, a fine cut is performed on the rough cut cross section using an ion beam to make the lower edge of the target sample consistent with the lower edge of the target area protected by W.

[0013] In step (7), under the electron beam window, the voltage is 1-10kV, the beam current is 25-200pA, and the nanomanipulator enters and stops moving instantly after contacting the FIB material surface. It does not move when it contacts the sample surface, which plays a role in extracting the charge.

[0014] In step (7), a metal probe is provided at the front end of the nanomanipulator, and the metal probe is selected from W, and the handle of the metal probe is any one of tungsten, nickel or stainless steel.

[0015] Compared with the prior art, the present invention achieves the following technical effects: The present invention utilizes the conductivity of the nanomanipulator to effectively improve the accumulation of charges on the sample surface. This prevents image drift during W plating and rough cutting under an ion beam, thereby enabling accurate W plating and rough cutting in the target area and improving the quality of cross-sectional images. The method is simple to operate, has high accuracy, has the effect of quickly improving the conductivity of the sample, and has strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a secondary ion image of the nanomanipulator approaching the sample surface in step (3) of Example 1 of the present invention.

[0017] Figure 2 This is a secondary ion image when the nanomanipulator contacts the sample surface in step (3) of Example 1 of the present invention.

[0018] Figure 3 This is a comparison diagram of the deposition of the protective layer before and after the nanomanipulator is inserted in step (3) of Example 1 of the present invention. The upper side is the deposition layer before the nanomanipulator is assisted, and the lower side is the deposition layer after the nanomanipulator is assisted.

[0019] Figure 4 It is a secondary ion image after rough cutting and fine cutting of the target area in step (4) of Example 1 of the present invention.

[0020] Figure 5 This is a secondary electron image of the slice cross section before the nanomanipulator is inserted in step (6) of Example 1 of the present invention.

[0021] Figure 6 This is a secondary electron image of the slice cross section after the nanomanipulator is inserted in step (6) of Example 1 of the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0023] Example 1 An embodiment of the present invention relates to a method for improving conductivity of FIB material analysis, comprising the following steps: (1) The target area found in scanning electron microscopy (SEM) mode; (2) Tilt the sample stage to prepare for protective layer deposition under the ion beam; (3) Extending the nanomanipulator to enhance conductivity and assist deposition; (4) Deposition of protective layer in target area; (5) Using an ion beam to perform rough and fine cutting on the target area to obtain a target cross section; (6) Retract the nanomanipulator and adjust the position of the cross-sectional area for observation under the scanning electron microscope; (7) Before taking pictures, insert the nanomanipulator to enhance the conductivity and improve the quality of the pictures.

[0024] In step (3), under the ion beam window, the voltage is 30kV, the beam current is 230pA, and the nanomanipulator enters and stops moving instantly after contacting the FIB material surface. A metal probe is provided at the front end of the nanomanipulator, and the metal probe is selected from a W metal probe.

[0025] Furthermore, the specific steps in step (4) are as follows: further, under the ion beam window, the voltage is 30 kV, the beam current is 230 pA, the nanomanipulator is entered, the nanomanipulator is controlled to move downward, and the movement is stopped at the moment of contact with the sample surface, and the tungsten needle is entered to deposit W in the target area to obtain the target area protected by the W layer; the deposition thickness is 0.5 μm, and the length of the target area protected by W is 10 μm and the width is 1.5 μm.

[0026] Furthermore, the specific steps in step (5) are: At a voltage of 30 kV and a beam current of 2.5 nA, the ion beam was used to perform rough cutting below the target area protected by W to obtain the target cross-section after rough cutting; at a voltage of 30 kV and a beam current of 80 pA, the rough-cut cross-section was finely cut using an ion beam to make the lower edge of the target sample consistent with the lower edge of the target area protected by W.

[0027] In step (7), under the ion beam window, the voltage is 30kV, the beam current is 230pA, and the nanomanipulator enters and stops moving instantly after contacting the FIB material surface. A metal probe is provided at the front end of the nanomanipulator, and the metal probe is selected from a W metal probe.

[0028] Compared with the prior art, the present invention achieves the following technical effects: Figure 3 The top and bottom are the comparison of the deposited coating before and after the nanomanipulator is inserted, that is, whether the nanomanipulator is inserted or not. Figure 3 The upper picture shows the nanomanipulator without being inserted. It can be seen that the coating has drifted and deviated from the target position. Figure 3 The figure below shows that there is no drift or deviation.

[0029] Figure 5 Figure 6 It is the image comparison after cutting the cross section. Figure 5 This is the figure obtained without performing step 7. Figure 5The image shows that the charge accumulation is serious and the image drifts and distorts. Figure 6 This is a figure after performing step 7. It can be seen from the figure that there is no image drift.

[0030] The present invention utilizes the conductivity of the nanomanipulator to effectively improve the accumulation of charges on the sample surface. This prevents image drift during W plating and rough cutting under an ion beam, thereby enabling accurate W plating and rough cutting in the target area and improving the quality of cross-sectional images. The method is simple to operate, has high accuracy, has the effect of quickly improving the conductivity of the sample, and has strong practicality.

Claims

1. A method for improving the conductivity of FIB-material analysis, characterized in that: The following steps are involved: (1) The target area found in scanning electron microscope mode; (2) Tilt the sample stage to prepare for protective layer deposition under the ion beam; (3) Extending the nanomanipulator to enhance conductivity and assist deposition; (4) Deposition of protective layer in target area; (5) Using an ion beam to perform rough and fine cutting on the target area to obtain a target cross section; (6) Retract the nanomanipulator and adjust the position of the cross-sectional area for observation under the scanning electron microscope; (7) Before taking pictures, insert the nanomanipulator to enhance the conductivity and improve the quality of the pictures.

2. The method for improving conductivity of FIB-material analysis according to claim 1, characterized in that: In step (3), under the ion beam window, the voltage is 20-30 kV, the beam current is 80-430 pA, and it enters the nanomanipulator and stops moving instantly after contacting the FIB material surface.

3. The method for improving conductivity of FIB-material analysis according to claim 2, characterized in that: The front end of the nanomanipulator is provided with a metal probe, the metal probe is selected from W, and the needle handle of the metal probe is any one of tungsten, nickel or stainless steel.

4. The method for improving the conductivity of FIB-material analysis according to claim 3, characterized in that: In step (4), continue to enter the tungsten needle under the ion beam window with a voltage of 20-30 kV and a beam current of 80-430 pA, and perform W deposition in the target area to obtain a target area protected by a W layer.

5. The method for improving conductivity of FIB-material analysis according to claim 4, characterized in that: The deposition thickness is 0.5-1 μm, and the target area protected by W is 2-5 μm in length and 1-3 μm in width.

6. The method for improving conductivity of FIB-material analysis according to claim 1, characterized in that: In step (5), at a voltage of 20-30 kV and a beam current of 0.79-9.3 nA, a rough cut is performed below the target area protected by W using an ion beam to obtain a target cross section after rough cutting; and then, at a voltage of 20-30 kV and a beam current of 40-230 pA, a fine cut is performed on the rough cut cross section using an ion beam.

7. The method for improving conductivity of FIB-material analysis according to claim 1, characterized in that: In step (7), under the electron beam window, the voltage is 1-10 kV, the beam current is 25-200 pA, and the nanomanipulator enters and stops moving instantly after contacting the FIB material surface.

8. The method for improving conductivity of FIB-material analysis according to claim 7, characterized in that: In step (7), a metal probe is provided at the front end of the nanomanipulator, and the metal probe is selected from W, and the handle of the metal probe is any one of tungsten, nickel or stainless steel.

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