Rapid pretreatment method for electron microscope sample

Abstract

The invention relates to a rapid pretreatment method for an electron microscope sample. The rapid pretreatment method comprises the steps of S1, surface cleaning, S2, embedding, S3, grinding and polishing, S4, chemical etching, S5, conductive treatment and S6, SEM analysis. Compared with FIB ion treatment, the method has the advantages that the sample preparation process is more controllable, the extension part of the silver layer can be removed by chemical erosion besides grinding and polishing, the damage to the film layer structure can be effectively reduced, the cost is low, the operation is simple and convenient, the repeatability is good, and powerful support is provided for SEM analysis of the film layer of the film coating sample.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of test samples, and in particular to a rapid pretreatment method for electron microscope samples. Background Art

[0002] Coating, as a technical means to significantly improve the surface properties of materials, has been widely used in many fields such as semiconductors, photovoltaics, and optics. In these high-tech industries, the quality and structure of the film formed by coating play a vital role in the final performance of the product. Scanning electron microscopy (SEM) is a key tool for observing and analyzing the microstructure of the film layer. During the preparation process of the coated sample, the surface of the film layer often has the problem of uneven extension, resulting in image distortion and blurring during electron microscope observation, which seriously affects the accuracy of the analysis. Therefore, how to optimize and improve the ductility of the surface of the coated film layer has become a problem that needs to be solved urgently in the current field of SEM technology.

[0003] At present, the coating samples are processed by focused ion beam (FIB) ion polishing and other technologies. This equipment is expensive and takes a long time to process. In addition, the high-energy ion beam will damage the sample during the process. When preparing the cross section, the cross section may produce a taper of 1.5 to 4 degrees, resulting in vertical lines on the cross section, which will affect the accuracy of the analysis.

[0004] In a 5NSi coating sample, there are 5N silicon layer, chrome layer, nickel copper layer and silver layer stacked in sequence. The silver layer is prone to extension at the cross section, which will cause the measured film thickness to be greater than the actual film thickness, and the test results will be seriously distorted.

[0005] Therefore, it is necessary to design a simple preprocessing method to solve the above problems. Summary of the invention

[0006] The main purpose of the present invention is to provide a rapid pretreatment method for electron microscope samples, which can effectively reduce the damage of the membrane structure, has low cost, simple operation and good repeatability.

[0007] The present invention achieves the above-mentioned purpose through the following technical scheme: a method for rapid pretreatment of electron microscope samples, comprising the following steps:

[0008] S1. Surface cleaning: Select the sample to be analyzed and put it into ethanol for ultrasonic cleaning;

[0009] S2. Mounting: Using adhesive to mount the sample in a hard mold with the cross section facing upward to obtain a mounted sample;

[0010] S3, grinding and polishing: first grind the cross section of the mounted sample with sandpaper, and finally polish it on a polishing wheel to obtain a polished mounted sample;

[0011] S4, chemical etching: drop an etchant on the cross section of the polished mounted sample, and etch it for 2-5 minutes by wiping method. The volume ratio of each component of the etchant formula is as follows: H2O2: NH4OH: H2O = 1:1:98, and obtain the etched mounted sample;

[0012] S5, conductive treatment: putting the etched inlaid sample into a gold plating machine, sputtering a gold film on the surface to obtain a plated inlaid sample;

[0013] S6. SEM analysis: Fix the coated mounted sample on the SEM sample stage for imaging analysis.

[0014] Specifically, the sample is a 5NSi coating sample, including a 5N silicon layer, a chrome-plated layer, a nickel-copper-plated layer and a silver layer stacked in sequence.

[0015] Specifically, the material of the adhesive is epoxy resin.

[0016] Specifically, the sandpaper polishing in step S2 is as follows: the mounted sample is polished with sandpapers of No. 80, 240, 400, 800, 1500, and 2400 with water in sequence, and each polishing time is 30s to 40s; each time the sandpaper is replaced, the polishing direction should be changed by 90°.

[0017] Specifically, the polishing method in step S2 is: using diamond polishing liquid to polish the cross section for 2 to 3 minutes.

[0018] The beneficial effects of the technical solution of the present invention are:

[0019] Compared with FIB ion treatment, this method has a more controllable sample preparation process. In addition to grinding and polishing, chemical etching is also used to remove the extended part of the silver layer, which can effectively reduce the damage to the film structure. It is low-cost, easy to operate, and has good repeatability, providing strong support for the SEM analysis of the film layer of the coated sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the SEM image of the cross-section sample of 5NSi coating after FIB ion treatment;

[0021] Figure 2 This is a SEM image of a cross-section sample of a 5NSi coating treated by the method of the present invention. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below with reference to specific embodiments.

[0023] Example:

[0024] like Figure 1 As shown, a method for rapid pretreatment of electron microscope samples of the present invention comprises the following steps:

[0025] S1. Surface cleaning: Select the sample to be analyzed and put it into ethanol for ultrasonic cleaning for 10 minutes.

[0026] Step S1 is to remove impurities and contaminants attached to the sample surface to ensure the purity of the sample surface. The sample in the embodiment is a 5NSi coating sample, including a 5N silicon layer, a chrome-plated layer, a nickel-copper-plated layer and a silver layer stacked in sequence.

[0027] S2. Mounting: Use adhesive to mount the sample in a hard mold with the cross section facing upward to obtain a mounted sample.

[0028] When the sample is subsequently processed, the detection surface (i.e., the cross section) needs to face upward, which requires a hard mold as a fixing base for the sample. At this time, the sample is in a vertical position in the hard mold, and the gap between the two is filled with an adhesive, so that the position of the sample can be maintained. The adhesive in the embodiment is epoxy resin. Because epoxy resin is simple and easy to obtain, and has good physical and chemical properties.

[0029] S3. Grinding and polishing: First, grind the cross section of the mounted sample with sandpaper, and finally polish it on a polishing wheel to obtain a polished mounted sample.

[0030] Sandpaper grinding is as follows: the inlaid sample is grinded with sandpapers of No. 80, 240, 400, 800, 1500, and 2400 with water in sequence, and each grinding time is 30s to 40s; each time the sandpaper is changed, the grinding direction should be changed by 90°. The polishing method is as follows: use diamond polishing liquid to polish the cross section for 2 to 3 minutes. In this step, the roughness of the sandpaper used for grinding gradually decreases, and finally the diamond polishing liquid is used for polishing, so that the cross section can be smooth without obvious textures or scratches, which is convenient for final observation.

[0031] S4. Chemical etching: drop an etchant on the cross section of the polished mounted sample and etch it for 2-5 minutes using a wiping method. The volume ratio of the components of the etchant formula is as follows: H2O2: NH4OH: H2O = 1:1:98, and obtain the etched mounted sample.

[0032] The hydrogen peroxide in the etchant can oxidize the silver at the cross section to +1 valence. In the presence of ammonia water, a silver ammonia solution will be generated. The silver exists in the form of Ag(NH3)2 + , which will dissolve in the solution, thereby effectively removing the extension of the outermost layer of the silver layer and improving the accuracy of the analysis.

[0033] S5. Conductive treatment: put the etched inlaid sample into a gold plating machine, sputter a gold film on the surface, and obtain a plated inlaid sample.

[0034] The conductivity of the coating material itself is poor, and the static electricity generated cannot be easily conducted away, resulting in charge accumulation, which in turn causes image distortion during SEM observation. In order to avoid this problem, the gold plating machine will coat the cross section with a very thin layer of gold film, the film thickness can even be as low as the diameter of a single gold atom. The purpose is to use the conductivity of gold to conduct the charge at the cross section without interfering with the observation of the cross section itself, thereby ensuring the accuracy of SEM detection.

[0035] S6. SEM analysis: Fix the coated mounted sample on the SEM sample stage for imaging analysis.

[0036] The acquired SEM images were post-processed and analyzed, including adjusting parameters such as brightness, contrast, and magnification to further improve image quality and enhance the accuracy of analysis.

[0037] Figure 1 and Figure 2 The pure black part in the middle and outer part is the adhesive epoxy resin. Figure 1 The 5N silicon layer, chrome-plated layer, nickel-plated copper layer and silver layer can also be distinguished, which gradually lighten in color from bottom to top. Figure 2 Only the 5N silicon layer, chrome-plated layer and nickel-plated copper layer can be distinguished, which gradually become lighter in color from bottom to top. Figure 1 and Figure 2 It can be seen that for the 5NSi coated samples treated by FIB ion treatment, the top silver layer will leave a large virtual shadow due to the extension problem, which seriously affects the accuracy of the film thickness analysis; for the 5NSi coated samples treated by this method, the silver layer is almost invisible, and the overall film thickness analysis can be more accurate. Therefore, compared with FIB ion treatment, this method has a more controllable sample preparation process. In addition to grinding and polishing, chemical etching is also used to remove the extended part of the silver layer, which can effectively reduce the damage to the film structure. It is low-cost, easy to operate, and has good repeatability, providing strong support for the SEM analysis of the film layer of the coated sample.

[0038] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for rapid pretreatment of electron microscope samples, characterized in that The steps include: S1. Surface cleaning: Select the sample to be analyzed and put it into ethanol for ultrasonic cleaning; S2. Mounting: Using adhesive to mount the sample in a hard mold with the cross section facing upward to obtain a mounted sample; S3, grinding and polishing: first grind the cross section of the mounted sample with sandpaper, and finally polish it on a polishing wheel to obtain a polished mounted sample; S4, chemical etching: drop an etchant on the cross section of the polished mounted sample, and etch it for 2-5 minutes by wiping method. The volume ratio of each component of the etchant formula is as follows: H2O2: NH4OH: H2O = 1:1:98, and obtain the etched mounted sample; S5, conductive treatment: putting the etched inlaid sample into a gold plating machine, sputtering a gold film on the surface to obtain a plated inlaid sample; S6. SEM analysis: Fix the coated mounted sample on the SEM sample stage for imaging analysis.

2. The method for rapid pretreatment of electron microscope samples according to claim 1, characterized in that: The sample is a 5NSi coating sample, which includes a 5N silicon layer, a chrome-plated layer, a nickel-copper-plated layer and a silver layer stacked in sequence.

3. The method for rapid pretreatment of electron microscope samples according to claim 1, characterized in that: The material of the adhesive is epoxy resin.

4. The method for rapid pretreatment of electron microscope samples according to claim 1, characterized in that: The sandpaper polishing in step S2 is as follows: the mounted sample is polished with sandpapers of No. 80, 240, 400, 800, 1500 and 2400 with water in sequence, and each polishing time is 30s to 40s; Each time you change the sandpaper, the grinding direction should be changed by 90°.

5. The method for rapid pretreatment of electron microscope samples according to claim 1, characterized in that: The polishing method in step S2 is: using diamond polishing liquid to polish the cross section for 2 to 3 minutes.

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