An EBSD packaging substrate sample and its preparation method

Abstract

The EBSD sample of the packaging substrate and its preparation method provided by this invention combine mechanical polishing, electrolytic polishing, and conductive treatment processes. Then, the conductive layer on the surface of the test area is removed using the ion beam of a FIB-SEM dual-beam system. This ensures the integrity of the diffraction pattern information of the test area while maintaining the conductivity of the EBSD sample to a certain extent, and simultaneously reduces the oxidation degree of the EBSD sample surface. This results in a packaging substrate EBSD sample with a high EBSD calibration rate, reaching 85%–95% or higher. The EBSD sample prepared using this method has a large testable area, allowing for the acquisition of all EBSD test and analysis information for blind vias in the packaging substrate. Compared to preparing EBSD samples by single FIB ion beam cutting, this method has a shorter preparation time, higher production efficiency, and the electrolytic polishing solution can be reused, thus reducing production costs to a certain extent.

Description

Technical Field

[0001] This invention relates to the field of semiconductor integrated circuit packaging substrate manufacturing, and in particular to an EBSD packaging substrate sample and its preparation method. Background Technology

[0002] As chips develop towards lower power consumption, higher speed, higher density, and lower voltage, the demand for packaging substrates has increased, and higher requirements have been placed on the performance and quality of packaging substrates. In the production process of packaging substrates, the size of the die and the orientation of the die in different layers will affect the performance and quality of the packaging substrate.

[0003] Electron backscatter diffraction (EBSD) is a technique that uses an electron beam in a scanning electron microscope to excite and form diffraction patterns on a tilted sample surface, thereby determining the crystal structure, orientation, and related information. EBSD can thus provide information on the microstructure, structure, grain size, shape, and orientation distribution of any crystalline material. The principle of EBSD is that the scattered electrons generated by the incident electron beam on a tilted crystalline sample form a diffraction pattern. This diffraction pattern carries crystallographic information such as the crystal structure and orientation of the scanned region of the sample, and provides absolute crystal orientation at sub-micron resolution. However, EBSD is highly sensitive to crystal defects, requiring the elimination of all surface defects in the test sample during preparation.

[0004] In existing technologies, the most commonly used methods for EBSD sample preparation are mechanical polishing, vibration polishing, chemical polishing, electrolytic polishing, focused ion beam (FIB) polishing, and argon ion polishing. Mechanical polishing yields samples with high flatness and brightness, and allows for the simultaneous preparation of multiple samples. However, it has a long preparation cycle, is prone to surface scratches, and suffers from residual stress, severely reducing the EBSD calibration rate. Vibratory polishing is time-consuming, has high sample processing costs, and is unsuitable for easily corroded magnesium alloys. Chemical polishing is fast, efficient, and suitable for complex parts, but it has poor brightness and generates significant pollution. Electrolytic polishing uses simple equipment, is low-cost, has a short preparation cycle, and produces no mechanical deformation, but it is only suitable for conductive materials. Focused ion beam (FIB) polishing has a long preparation cycle, but requires the removal of obstructions around the test area, resulting in a small observation area and very high equipment costs. Argon ion polishing can obtain a good surface without causing mechanical damage to the sample, but the experimental parameters are difficult to control, and the high cost of experimental equipment prevents its widespread adoption. Furthermore, the heat generated by ion bombardment may damage the surface of the EBSD sample, significantly impacting the EBSD calibration rate.

[0005] Currently, for some failed packaging substrate samples, it is necessary to perform EBSD technology analysis on key parts of the packaging substrate, such as the interconnect surface of blind vias. When FIB polishing is selected to prepare packaging substrate EBSD samples, the preparation time is as long as 8 hours, and the area that can be tested for EBSD is very small, with a calibration rate of only about 53% after testing. If mechanical polishing is selected to prepare packaging substrate EBSD samples, it is impossible to capture any EBSD pattern on the packaging substrate. Therefore, it is crucial to design a preparation method for packaging substrate EBSD samples with specific parameters. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide an EBSD sample of a packaged substrate and a method for preparing the same, so as to solve the problems of high cost, long preparation time and complex process flow leading to low production efficiency in the preparation of EBSD samples of packaged substrates, and small test area or even no diffraction pattern of EBSD samples, which seriously affect the EBSD calibration rate.

[0007] To achieve the above and other related objectives, the present invention provides a method for preparing an EBSD sample of a packaging substrate, the method comprising the following steps:

[0008] Mechanical grinding and polishing are performed on the packaging substrate;

[0009] Electropolishing of a mechanically polished packaging substrate is performed using an electropolishing solution composed of inorganic acids and organic alcohols.

[0010] The electropolished packaging substrate is then subjected to conductive treatment by gold or carbon spraying.

[0011] The gold or carbon layer on the surface of the area to be tested is removed using a FIB-SEM dual-beam system to obtain the EBSD sample of the packaged substrate.

[0012] Optionally, the mechanical polishing process includes cutting the packaging substrate, curing it with epoxy resin, and then sequentially mechanically grinding and mechanically polishing the packaging substrate, wherein the polishing slurry used for mechanical polishing includes an alumina polishing slurry with a particle size of 0.3 μm.

[0013] Optionally, when mechanically polishing the packaging substrate, sandpaper of 180 grit, 360 grit, 600 grit, 1200 grit, 2400 grit and 4000 grit is used in sequence, and the packaging substrate is rotated 90° each time the sandpaper is changed, until the previous polishing marks are eliminated.

[0014] Optionally, the specific steps of the mechanical polishing are as follows: the rotation speed is adjusted to 100-500 r / min to perform the first polishing of the packaging substrate, and alumina polishing slurry is added during the first polishing process; then the rotation speed is adjusted to 100-300 r / min to perform the second polishing, until the polished cross section of the packaging substrate is free of scratches and has a bright mirror surface under an optical microscope.

[0015] Optionally, the mechanical polishing time is 0.5 min to 5 min.

[0016] Optionally, during electropolishing, a copper sheet is used as the cathode and connected to the negative terminal of the power supply, and the packaging substrate is used as the anode and connected to the positive terminal of the power supply. During the electropolishing process, the electrolyte is continuously stirred until bubbles are generated on the surface of the packaging substrate and it has a bright mirror finish. After the electropolishing is completed, the packaging substrate is removed and cleaned and dried.

[0017] Optionally, the parameters for electropolishing are set as follows: voltage 5V~10V, current 0.5A~3A, and polishing time 2s~30s.

[0018] Optionally, the electropolishing solution used in electropolishing is obtained by mixing phosphoric acid, ethanol, isopropanol, and DI water in a mass fraction ratio of 5:5:1:10 or 5.5:4.5:1:8.

[0019] Optionally, the method for removing the gold or carbon layer on the surface of the area to be tested using a FIB-SEM dual-beam system includes placing the conductive packaged substrate into the horizontal sample stage of the sample chamber, evacuating the sample chamber, rotating the horizontal sample stage by a certain angle, adjusting the ion beam pair and parameters of the FIB-SEM dual-beam system, thereby removing the gold or carbon layer on the surface of the area to be tested on the packaged substrate.

[0020] Optionally, the parameters of the FIB-SEM dual-beam system are: FIB accelerating voltage 10kV~30kV; FIB beam current intensity 30pA~100pA.

[0021] The present invention also provides an EBSD packaging substrate sample, which can be prepared by the preparation method of the EBSD packaging substrate sample according to any one of claims 1 to 10.

[0022] The EBSD sample of the packaging substrate and its preparation method of the present invention have the following beneficial effects: The preparation method combines mechanical polishing, electrolytic polishing, and conductive treatment processes, and then uses the ion beam of the FIB-SEM dual-beam system to remove the conductive layer on the surface of the test area. This ensures the integrity of the diffraction pattern information of the test area, maintains the conductivity of the EBSD sample to a certain extent, and reduces the oxidation degree of the EBSD sample surface, thereby preparing a packaging substrate EBSD sample with a high EBSD calibration rate, which can reach 85% to 95% or higher. The packaging substrate EBSD sample prepared by the above preparation method has a large testable area, thus obtaining all EBSD test and analysis information of the blind vias in the packaging substrate. Compared with the preparation of packaging substrate EBSD samples by single FIB ion beam cutting, the preparation time is short and the production efficiency is high. The electrolytic polishing solution in the preparation process can also be reused, thereby reducing the production cost to a certain extent. Attached Figure Description

[0023] Figure 1 The flowchart shown is a method for preparing an EBSD sample of a packaging substrate provided by the present invention.

[0024] Figure 2 The image shown is a calibration result diagram of the EBSD sample of the packaging substrate obtained in Embodiment 1 of the present invention. Detailed Implementation

[0025] The following specific examples illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0026] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0027] The technical solutions provided by the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings and specific examples.

[0028] Figure 1 This is a flowchart of the method for preparing the EBSD sample of the packaging substrate of the present invention, as shown below. Figure 1 As shown, the preparation method includes the following steps:

[0029] S1: Mechanical grinding and polishing of the packaging substrate;

[0030] S2: Electropolishing of the mechanically polished packaging substrate is performed using an electropolishing solution composed of inorganic acids and organic alcohols.

[0031] S3: Perform conductive treatment on the electropolished packaging substrate by sputtering gold or carbon.

[0032] S4: Remove the gold or carbon layer on the surface of the area to be tested using a FIB-SEM dual-beam system to obtain the EBSD sample of the packaged substrate.

[0033] As an example, the specific process of step S1 is as follows: the packaging substrate to be tested is cut to a suitable size, and the cut packaging substrate is potted and cured. Specifically, epoxy resin can be used, and there should be no visible gaps at the interface between the cured packaging substrate and the epoxy resin. After curing, the packaging substrate is mechanically ground and mechanically polished in sequence. During mechanical grinding, 180 grit, 360 grit, 600 grit, 1200 grit, 2400 grit, and 4000 grit sandpaper are used in sequence. Each time the sandpaper is changed, the packaging substrate is rotated 90° before the next mechanical grinding is performed, until the previous grinding marks are eliminated. After mechanical grinding is completed, the packaging substrate is then mechanically polished. The specific steps of mechanical polishing are as follows: First, the rotation speed is adjusted to 100r / min to 500r / min for the first polishing of the packaging substrate. During the first polishing process, alumina polishing slurry with a particle size of 0.3μm is added to prevent stress concentration on the packaging substrate during polishing, which would affect the EBSD calibration rate. Then, the rotation speed is adjusted to 100r / min to 300r / min for the second polishing, until the polished cross-section of the packaging substrate is free of scratches and has a bright mirror surface when observed under an optical microscope. The mechanical polishing time is 0.5min to 5min, and the specific time can be set according to actual needs.

[0034] As an example, the specific process of step S2 is as follows: Add an electrolytic polishing solution with a mass fraction ratio of phosphoric acid:ethanol:isopropanol:DI water of 5:5:1:10 or 5.5:4.5:1:8 to a beaker. When measuring the mass fraction of each component, ensure that the error does not exceed 5% of its respective mass. Place the beaker on a magnetic stirrer to ensure continuous stirring of the electrolytic polishing solution during the electrolytic polishing process. This promotes the flow of the electrolytic polishing solution, ensures ion diffusion within the polishing area and replenishment of the electrolytic polishing solution, thereby avoiding surface spots due to uneven polishing. Then, place a copper sheet into the beaker and connect it to the negative terminal of the power supply. The mechanically polished packaged substrate is placed in a beaker and connected to the positive terminal of a power supply, serving as the cathode during electrolysis. The mechanically polished packaged substrate is then used as the anode during electrolysis. The settings of parameters such as polishing voltage, current, and time directly affect the polishing quality of the sample. Therefore, this invention sets the voltage between the cathode and anode to 5V–10V, the current to 0.5A–3A, and the polishing time to 2s–30s. If the current exceeds the range or the polishing time is too long, the sample is prone to over-corrosion. If the current is below the range or the polishing time is too short, the stress layer of the sample cannot be effectively removed, which will seriously affect the EBSD calibration rate of the sample. Furthermore, the electrolytic polishing of the sample occurs after mechanical polishing to prevent scratches from affecting the EBSD calibration rate of the sample.

[0035] Optionally, the electropolishing process continues until bubbles are generated on the surface of the packaging substrate and the surface of the area to be tested on the packaging substrate appears as a bright mirror under an optical microscope. Then, the packaging substrate is removed from the electropolishing solution and quickly cleaned and dried to obtain the packaging substrate after electropolishing.

[0036] As an example, the specific process of step S3 is as follows: Since the sample needs to be conductive when using a scanning electron microscope (SEM) to analyze the sample, the packaged substrate after electropolishing is sputtered with gold or carbon to ensure that the sample can conduct electricity. Sputtering gold or carbon can also avoid oxidation on the surface of the packaged substrate, thereby reducing the impact on the EBSD calibration rate of the packaged substrate.

[0037] As an example, the specific process of step S4 is as follows: After the conductive treatment of the encapsulation substrate is applied with conductive adhesive, it is placed on the horizontal sample stage of the SEM sample chamber. The sample chamber is evacuated. After the vacuum degree reaches a certain value, the ion beam of the FIB-SEM dual-beam system is turned on, and its parameters are adjusted to an accelerating voltage of 10kV to 30kV and a beam current of 30pA to 100pA. Then, the horizontal sample stage is rotated at a certain angle and adjusted to the position of the test area on the encapsulation substrate, thereby removing the gold or carbon layer on the surface of the test area, and finally obtaining an EBSD sample of the encapsulation substrate that meets the requirements of EBSD technology testing.

[0038] Optionally, after removing the qualified EBSD sample from the horizontal chamber, place it on a 45° sample stage, adjust the angle of the sample stage to 70°, and set a voltage of 30kV to complete the testing and analysis of the area under test.

[0039] Example 1

[0040] Specifically, the packaging substrate is cut to a suitable size and then coated with epoxy resin for curing. After curing, the packaging substrate is mechanically polished sequentially using sandpaper of 180 grit, 360 grit, 600 grit, 1200 grit, 2400 grit, and 4000 grit. Each time the sandpaper is changed, the packaging substrate is rotated 90° before the next polishing, until the previous scratches are eliminated. After mechanical polishing, the packaging substrate is mechanically polished. The first polishing is performed at a speed of 500 r / min, with 0.3 μm alumina polishing slurry added during the first polishing process. The first polishing time is 30 seconds. The second polishing is performed at a speed of 300 r / min for 15 seconds, resulting in a packaging substrate with a scratch-free and bright mirror-like surface when observed under an optical microscope.

[0041] Specifically, an electrolytic polishing solution with a mass fraction ratio of phosphoric acid:ethanol:isopropanol:DI water of 5:5:1:10 is added to a beaker. The beaker is placed on a magnetic stirrer to ensure continuous stirring of the electrolytic polishing solution during the electrolytic polishing process. A copper sheet is placed in the beaker and connected to the negative terminal of the power supply, serving as the cathode during electrolysis. The mechanically polished packaging substrate is placed in the beaker and connected to the positive terminal of the power supply, serving as the anode during electrolysis. The voltage between the cathode and anode is set to 5V, the current to 1.6A, and the polishing time to 5s. Then, the packaging substrate is removed from the electrolytic polishing solution and quickly cleaned and dried to complete the electrolytic polishing.

[0042] Specifically, the packaging substrate after electropolishing is then subjected to gold sputtering.

[0043] Specifically, after the gold-sprayed packaging substrate is coated with conductive adhesive, it is placed on the horizontal sample stage of the SEM sample chamber. The sample chamber is evacuated, the ion beam of the FIB-SEM dual-beam system is turned on, and its parameters are adjusted to a voltage of 30kV and a current of 100pA. Then, the horizontal sample stage is adjusted to the position of the test area on the packaging substrate, and the gold layer on the surface of the test area is removed to finally obtain the packaging substrate EBSD sample that meets the requirements of EBSD technology testing.

[0044] Field emission scanning electron microscopy (FESEM) was used to observe EBSD samples on the packaged substrate. EBSD testing was performed at an operating voltage of 30 kV and a tilt angle of 70°, achieving a calibration rate of 92.55%. Experimental results are as follows: Figure 2 As shown.

[0045] Example 2

[0046] Specifically, the packaging substrate is cut to a suitable size and then coated with epoxy resin for curing. After curing, the packaging substrate is mechanically polished sequentially using sandpaper of 180 grit, 360 grit, 600 grit, 1200 grit, 2400 grit, and 4000 grit. Each time the sandpaper is changed, the packaging substrate is rotated 90° before the next polishing, until the previous scratches are eliminated. After mechanical polishing, the packaging substrate is mechanically polished. The first polishing is performed at a speed of 250 r / min, during which 0.3 μm alumina polishing slurry is added. The first polishing time is 15 seconds. The second polishing is performed at a speed of 150 r / min for 30 seconds, resulting in a packaging substrate with a smooth, bright mirror-like surface under an optical microscope, free of scratches.

[0047] Specifically, an electrolytic polishing solution with a mass fraction ratio of phosphoric acid:ethanol:isopropanol:DI water of 5:5:1:10 is added to a beaker. The beaker is placed on a magnetic stirrer to ensure continuous stirring of the electrolytic polishing solution during the electrolytic polishing process. A copper sheet is placed in the beaker and connected to the negative terminal of the power supply, serving as the cathode during electrolysis. The mechanically polished packaging substrate is placed in the beaker and connected to the positive terminal of the power supply, serving as the anode during electrolysis. The voltage between the cathode and anode is set to 5V, the current to 2A, and the polishing time to 15s. Then, the packaging substrate is removed from the electrolytic polishing solution and quickly cleaned and dried to complete the electrolytic polishing.

[0048] Specifically, the packaging substrate after electropolishing is then subjected to gold sputtering.

[0049] Specifically, after the gold-sprayed packaging substrate is coated with conductive adhesive, it is placed on the horizontal sample stage of the SEM sample chamber. The sample chamber is evacuated, the ion beam of the FIB-SEM dual-beam system is turned on, and its parameters are adjusted to a voltage of 30kV and a current of 100pA. Then, the horizontal sample stage is adjusted to the position of the area to be tested, and the gold layer on the surface of the area to be tested is removed. Finally, an EBSD sample of the packaging substrate that meets the requirements of EBSD technology testing is obtained.

[0050] EBSD samples were observed using a field emission scanning electron microscope. The operating voltage was set to 30 kV and the tilt angle was 70° for EBSD testing, and the calibration rate reached 93.89%.

[0051] The EBSD sample of the packaging substrate and its preparation method of the present invention have the following beneficial effects: The preparation method combines mechanical grinding and polishing with electrolytic polishing processes, and then uses the ion beam of the FIB-SEM dual-beam system to remove the conductive layer on the surface of the test area. On the one hand, the FIB-SEM dual-beam system can accurately position and process the sample; on the other hand, FIB is a focused beam, which causes less damage to the sample compared to the ion beam, and can observe the lattice morphology and internal defects of the sample. This ensures the integrity of the diffraction pattern information of the test area, maintains the conductivity of the EBSD sample of the packaging substrate to a certain extent, and reduces the oxidation degree of the surface of the EBSD sample of the packaging substrate, thereby preparing a EBSD sample of the packaging substrate with a high EBSD calibration rate, which can reach 85% to 95% or higher. The EBSD sample of the packaging substrate prepared by the preparation method has a large testable area, thus obtaining all EBSD test and analysis information of the blind holes in the packaging substrate. Compared with the preparation of EBSD samples of the packaging substrate by single FIB ion beam cutting, the preparation time is short and the production efficiency is high. The electrolytic polishing solution in the preparation process can also be reused, thereby reducing the production cost to a certain extent. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0052] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing an EBSD sample of a packaging substrate, characterized in that, The preparation method includes the following steps: The packaging substrate was mechanically polished with sandpaper of 180 grit, 360 grit, 600 grit, 1200 grit, 2400 grit and 4000 grit in sequence. Each time the sandpaper was changed, the packaging substrate was rotated 90° at the same time until the previous polishing marks were removed. Mechanical polishing includes first polishing the packaging substrate by adjusting the rotation speed to 100~500 r / min, during which alumina polishing slurry is added; then, the rotation speed is adjusted to 100 r / min~300 r / min for a second polishing, until the polished cross section of the packaging substrate is free of scratches and has a bright mirror surface under an optical microscope. The mechanical polishing time is 0.5 min~5 min. Electropolishing of a mechanically polished packaging substrate is performed using an electropolishing solution obtained by mixing phosphoric acid, ethanol, isopropanol, and DI water. The electropolishing parameters are set as follows: voltage 5V~10V, current 0.5A~3A, polishing time 2s~30s, and the mass fraction ratio of the electropolishing solution is either 5:5:1:10 or 5.5:4.5:1:

8. The electropolished packaging substrate is then subjected to conductive treatment by gold or carbon spraying. The conductive packaged substrate is placed into the horizontal sample stage of the sample chamber of the FIB-SEM dual-beam system, and the sample chamber is evacuated. The horizontal sample stage is rotated at a certain angle, and the ion beam pair of the FIB-SEM dual-beam system is adjusted with the following parameters: FIB accelerating voltage 10kV~30kV, FIB beam current intensity 30pA~100pA. This removes the gold or carbon layer on the surface of the area to be tested on the packaged substrate to obtain the EBSD sample of the packaged substrate.

2. The preparation method according to claim 1, characterized in that: The mechanical grinding and polishing process includes cutting the packaging substrate, curing it with epoxy resin, and then mechanically grinding and polishing the packaging substrate in sequence. The polishing slurry used for mechanical polishing is alumina polishing slurry.

3. The preparation method according to claim 1, characterized in that: During electropolishing, a copper sheet is used as the cathode and connected to the negative terminal of the power supply, while the packaging substrate is used as the anode and connected to the positive terminal of the power supply. During the electropolishing process, the electrolyte is continuously stirred until bubbles are generated on the surface of the packaging substrate and it becomes a bright mirror surface. After the electropolishing is completed, the packaging substrate is removed and cleaned and dried.

4. An EBSD packaging substrate sample, characterized in that: The EBSD sample of the packaging substrate was prepared using the preparation method described in any one of claims 1 to 3.

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