A method for improving conductivity in FIB-material analysis

Abstract

A method for improving conductivity in FIB material analysis includes the following steps: identifying a target area under scanning electron microscope mode, tilting the sample stage to prepare for protective layer deposition under an ion beam, inserting a nanomanipulator to enhance conductivity and assist deposition before depositing the protective layer, using the ion beam to perform rough and fine sectioning of the target area to obtain a target cross-section, returning the nanomanipulator to adjust the position of the cross-section area for observation under the scanning electron microscope, and inserting the nanomanipulator again before imaging to enhance conductivity and improve image quality. This method utilizes the conductivity of the nanomanipulator to effectively improve charge accumulation on the sample surface. This eliminates image drift during W plating and rough sectioning under the ion beam, enabling precise W plating and rough sectioning in the target area and improving the quality of cross-section images. This method is simple to operate, highly accurate, and rapidly improves sample conductivity, making it highly practical.

Description

Technical Field

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

[0002] With the advancement of science and technology, the requirements for characterizing the microstructure of materials have also increased. A focused ion beam (FIB) is a scanning electron microscope (SEM) equipped with an ion beam column and a nanomanipulator. Its operating principle is to first use a high-energy ion beam to cut a specific analysis location in the material, creating a cross-section. The micro-nanostructure of this specific location is then imaged and analyzed using a high-resolution SEM.

[0003] Compared to conductive materials, materials with poor conductivity have a severe charging effect, making FIB processing more difficult. This charging effect can cause blurred or even offset images, making it difficult for the FIB ion beam to accurately position and process them. Currently, the method for improving sample conductivity is generally to coat the sample surface with a conductive metal film before testing to eliminate the charging effect. However, during slicing, the continuous ion beam irradiation will etch away the surface metal film, thus eliminating 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. This method uses the conductivity of the nanomanipulator to guide the accumulated electrons, thereby reducing the charging effect and effectively solving the image drift problem, so that precise positioning can be achieved during slicing, improving slicing efficiency and the quality of the final cross-sectional image.

[0005] To achieve the above object, the present invention provides a method for improving the conductivity of FIB material analysis, characterized by comprising the following steps:

[0006] (1) The target area found in scanning electron microscopy (SEM) mode;

[0007] (2) Tilt the sample stage to prepare for protective layer deposition under the ion beam;

[0008] (3) Inserting nanomanipulators to enhance conductivity and assist deposition;

[0009] (4) Deposition of protective layer in target area;

[0010] (5) Using the ion beam to perform rough and fine cutting on the target area to obtain the target cross section;

[0011] (6) Retract the nanomanipulator and adjust the position of the cross-section area for observation under the scanning electron microscope;

[0012] (7) Before taking the photo, insert the nanorobot to enhance the conductivity and improve the quality of the photo.

[0013] 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 degrees, which may be slightly different for other types of equipment.

[0014] In step (3), under the ion beam window, the voltage is 20-30kV, and the beam current is 80-430pA. The nanomanipulator enters and stops moving the moment it contacts the FIB material surface. It does not move when it contacts the FIB sample surface. When the nanomanipulator is not in use, it remains stationary.

[0015] 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.

[0016] The front end of the nanomanipulator is made of metal tungsten, which has good conductivity. When it contacts the surface of the sample, it can extract the charge accumulated on the surface of the sample (the surface of the sample with poor conductivity will continue to accumulate charge when scanning).

[0017] 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 the W layer.

[0018] 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.

[0019] In step (5), the ion beam is used to perform rough cutting below the target area protected by W at a voltage of 20-30 kV and a beam current of 0.79-9.3 nA to obtain a target cross section after rough cutting; and the ion beam is used to perform fine cutting on the rough cut cross section at a voltage of 20-30 kV and a beam current of 40-230 pA to make the lower edge of the target sample consistent with the lower edge of the target area protected by W.

[0020] 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 stays still after contacting the sample surface, playing the role of extracting charge.

[0021] 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.

[0022] Compared with the prior art, the present invention achieves the following technical effects:

[0023] This method leverages the conductivity of the nanomanipulator to effectively improve surface charge accumulation on the sample. This eliminates image drift during W plating and rough cutting under an ion beam, enabling precise W plating and rough cutting in the target area and improving the quality of cross-sectional images. This method is simple to operate, highly accurate, and rapidly improves sample conductivity, demonstrating its strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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.

[0025] Figure 2 This is a secondary ion image of the nanomanipulator when it contacts the sample surface in step (3) of Example 1 of the present invention.

[0026] Figure 3 This is a comparison diagram of the protective layer deposition 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.

[0027] Figure 4 This is a secondary ion image after the target area is roughly cut and finely cut in step (4) of Example 1 of the present invention.

[0028] 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.

[0029] 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

[0030] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, 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 equally within the scope limited by the appended claims of the application.

[0031] Example 1

[0032] An embodiment of the present invention relates to a method for improving conductivity of FIB material analysis, comprising the following steps:

[0033] (1) The target area found in scanning electron microscopy (SEM) mode;

[0034] (2) Tilt the sample stage to prepare for protective layer deposition under the ion beam;

[0035] (3) Inserting nanomanipulators to enhance conductivity and assist deposition;

[0036] (4) Deposition of protective layer in target area;

[0037] (5) Using the ion beam to perform rough and fine cutting on the target area to obtain the target cross section;

[0038] (6) Retract the nanomanipulator and adjust the position of the cross-sectional area for observation under the scanning electron microscope;

[0039] (7) Before taking the photo, insert the nanorobot to enhance the conductivity and improve the quality of the photo.

[0040] 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. The front end of the nanomanipulator is provided with a metal probe, and the metal probe is selected from a W metal probe.

[0041] 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.

[0042] Furthermore, the specific steps in step (5) are:

[0043] 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 fine-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.

[0044] 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. The front end of the nanomanipulator is provided with a metal probe, and the metal probe is selected from a W metal probe.

[0045] Compared with the prior art, the present invention achieves the following technical effects: Figure 3 The top and bottom are respectively the comparison of the deposited coating before and after the nanomanipulator is inserted, that is, whether the step of inserting the nanomanipulator is included. Figure 3 The upper picture is the one without the nanomanipulator inserted. It can be seen that the coating has drifted and deviated from the target position. Figure 3The figure below shows that there is no drift or deviation.

[0046] Figure 5 Figure 6 The image comparison is taken after cutting the cross section, where Figure 5 This is the figure obtained without performing step 7. Figure 5 The image shows serious charge accumulation, image drift, and distortion. Figure 6 This is a figure after step 7 is performed. It can be seen from the figure that there is no image drift.

[0047] This method leverages the conductivity of the nanomanipulator to effectively improve surface charge accumulation on the sample. This eliminates image drift during W plating and rough cutting under an ion beam, enabling precise W plating and rough cutting in the target area and improving the quality of cross-sectional images. This method is simple to operate, highly accurate, and rapidly improves sample conductivity, demonstrating its 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) Insert the nanomanipulator to enhance conductivity-assisted deposition. Under the ion beam window, the voltage is 20-30kV, the beam current is 80-430pA, enter the nanomanipulator, and stop moving instantly after contacting the FIB material surface; (4) Deposition of protective layer in target area; (5) Using the ion beam to perform rough and fine cutting on the target area to obtain the 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 shooting, insert the nanomanipulator to enhance the conductivity and improve the quality of the photos. 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 surface of the FIB material.

2. The method for improving conductivity of FIB-material analysis according to claim 1, 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.

3. The method for improving conductivity of FIB-material analysis according to claim 2, 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 the W layer.

4. The method for improving conductivity of FIB-material analysis according to claim 3, 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.

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

6. The method for improving conductivity of FIB-material analysis according to claim 1, 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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