Transmission electron microscope sample and preparation method thereof

Abstract

The invention relates to a method for preparing a transmission electron microscope sample, and the method comprises the steps: S1, cutting a sample containing a TSV structure from a wafer, and adhering the sample to a U-shaped fork; s2, fixing the U-shaped fork adhered with the sample on a T-shaped bracket; s3, adjusting the sample and the T-shaped bracket to a horizontal state; s4, adjusting the height of one end of the T-shaped bracket to enable the T-shaped bracket to form an inclined angle with the horizontal plane; s5, grinding the sample on the T-shaped bracket with the inclined angle so as to form a sample with an inclined edge structure; and S6, performing FIB processing on the sample with the bevel edge structure after grinding to form the transmission electron microscope sample. According to the method, the preparation time of the transmission electron microscope sample can be shortened, and the efficiency of an FIB machine can be improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular, to a transmission electron microscope sample and a preparation method thereof. Background Art

[0002] Through-Silicon Via (TSV) technology is a vertical electrical interconnection passing through a silicon substrate (wafer or chip), and vertical conduction is made between chips and between wafers. TSV technology realizes vertical electrical interconnection of silicon vias (as shown in Figure 1 ), and is a technology for realizing interconnection between chips. This technology is the latest vertical electrical interconnection technology at present and is one of the key technologies for realizing 3D advanced packaging.

[0003] In TSV technology, as shown in Figure 2 , since the TSV depth reaches 60 μm or more, when observing the top, middle, and bottom structures of a sample simultaneously, the preparation method of a common transmission electron microscope sample needs to perform FIB (focused ion beam) processing three times. Specifically, cut the top of the transmission electron microscope sample and enter the FIB machine for processing; after cutting the top transmission electron microscope sample and taking it out, grind it with a grinding machine until it is close to the middle, and then enter the FIB machine for processing; then after cutting the middle transmission electron microscope sample and taking it out, grind it with a grinding machine until it is close to the bottom, and then enter the FIB machine for processing. A total of two grindings are required and the machine is entered and exited three times.

[0004] In the current prior art, the structures of different parts of a sample cannot be observed simultaneously, resulting in a long preparation time for the transmission electron microscope sample, and the machine time cannot be effectively utilized, slowing down the processing speed of the FIB machine. Summary of the Invention

[0005] The object of the present invention is to provide a transmission electron microscope sample and a preparation method thereof, which can shorten the preparation time of the transmission electron microscope sample and improve the efficiency of the FIB machine.

[0006] To achieve the above object, in the first aspect of the present invention, a method for preparing a transmission electron microscope sample is provided, and the method includes:

[0007] S1. Cut out a sample containing a TSV structure from a wafer and adhere the sample to a U-shaped fork;

[0008] S2. Fix the U-shaped fork with the sample adhered thereto on a T-shaped bracket;

[0009] S3. Adjust the sample and the T-shaped bracket to a horizontal state;

[0010] S4. Adjust the height of one end of the T-shaped bracket to form an inclination angle between the T-shaped bracket and the horizontal plane;

[0011] S5. Grind the sample on the T-shaped bracket with the formed inclination angle to form a sample with a bevel structure;

[0012] S6. Perform FIB processing on the sample with the bevel structure after grinding to form the transmission electron microscope sample.

[0013] Optionally, the thickness of the sample containing the TSV structure is 120 - 150 nm; the depth of the TSV structure is 60 - 80 μm.

[0014] Optionally, the step of adhering the sample to the U-shaped fork includes: placing a piece of glass at the front end of the U-shaped fork, coating a hot melt adhesive on the glass to form an adhesion layer, and adhering the sample on the adhesion layer.

[0015] Optionally, the T-shaped bracket is provided with adjusting feet. Dip the front end of the U-shaped fork adhered with the sample in water, place a piece of glass on the T-shaped bracket, and rotate the adjusting feet by observing the water mark on the glass to adjust the sample and the T-shaped bracket to a horizontal state.

[0016] Optionally, the length of the T-shaped bracket is 3 - 5 cm, the height of one end of the T-shaped bracket is 1 - 2 cm, and the inclination angle is 11.53° - 41.82°.

[0017] Optionally, the grinding step includes: grinding the sample with water sandpaper until the middle part of the TSV structure is exposed, and then grinding with diamond sandpaper until the bottom of the TSV structure is exposed to form the sample with the bevel structure, so that the top, middle, and bottom of the TSV structure of the sample are presented simultaneously.

[0018] Optionally, the angle between the bevel and the horizontal plane is 11.53° - 41.82°.

[0019] Optionally, after grinding, the depth of the middle part of the TSV structure of the sample is 30 - 40 μm, and the depth of the bottom of the TSV structure is 2 - 5 μm.

[0020] Optionally, the FIB processing step includes: making marks on the surface of the sample with the bevel structure, depositing a platinum protection layer in the marked area, forming grooves on the front and back sides of the platinum protection layer, the depth of the grooves can expose the side walls of the TSV structure, using an ion beam to thin the sample in the grooves to an ideal thickness, and cutting off the bottom and two side walls of the sample in the grooves to form the transmission electron microscope sample.

[0021] In a second aspect of the present invention, a transmission electron microscope sample is provided, which is prepared by the method provided in the first aspect of the present invention.

[0022] Optionally, the transmission electron microscope sample includes a TSV structure; the thickness of the transmission electron microscope sample is 70-90 nm.

[0023] Optionally, the transmission electron microscope sample has a bevel structure.

[0024] Through the above technical solutions, in the present invention, the sample on the T-shaped bracket with an inclined angle is ground to form a sample with a bevel structure, so that the top, middle and bottom of the TSV structure of the sample can be presented simultaneously; then the ground sample with a bevel structure is processed by FIB to form a transmission electron microscope sample, and the structures of the top, middle and bottom of the sample can be observed simultaneously. The method of the present invention applies the T-shaped bracket to the TSV, which can increase the speed and convenience of FIB execution, reduce the number of grinding times and the number of times of entering and leaving the FIB machine, thereby shortening the preparation time of the transmission electron microscope sample, improving the efficiency of the FIB machine, and at the same time increasing the output rate of the transmission electron microscope sample.

[0025] Other features and advantages of the present invention will be described in detail in the subsequent specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification, and are used to explain the present invention together with the following specific implementation, but do not constitute a limitation to the present invention. In the drawings:

[0027] Figure 1 is an electron microscope image of a through-silicon via structure;

[0028] Figure 2 is an electron microscope image of the top, middle and bottom structures of a through-silicon via;

[0029] Figure 3 is a top view of the sample at the test structure position of the present invention;

[0030] Figure 4 is a schematic structural diagram of adhering the sample to the U-fork in the present invention;

[0031] Figure 5 is a schematic structural diagram of placing the U-fork on the T-holder and adjusting the sample and the T-holder to be horizontal in the present invention;

[0032] Figure 6 is a schematic diagram of placing the glass on the T-holder and water on the glass in the present invention;

[0033] Figure 7It is a schematic diagram of the present invention for adjusting the tilt angle by rotating the T-holder adjustment feet;

[0034] Figure 8 It is a schematic cross-sectional view before and after grinding of a sample for testing the structural position of the present invention;

[0035] Figure 9 It is a schematic cross-sectional view of the ground sample of the present invention;

[0036] Figure 10 It is a TEM image of different parts of the ground sample of the present invention. Specific Embodiments

[0037] The following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for explaining and illustrating the present invention, and are not used to limit the present invention.

[0038] The first aspect of the present invention provides a method for preparing a transmission electron microscope sample, the method comprising:

[0039] S1. Cut out a sample containing a TSV structure from a wafer and adhere the sample to a U-fork;

[0040] S2. Fix the U-fork with the adhered sample on a T-holder;

[0041] S3. Adjust the sample and the T-holder to a horizontal state;

[0042] S4. Adjust the height of one end of the T-holder to form an inclination angle between the T-holder and the horizontal plane;

[0043] S5. Grind the sample on the T-holder with the formed inclination angle to form a sample with a bevel structure;

[0044] S6. Perform FIB processing on the ground sample with the bevel structure to form the transmission electron microscope sample.

[0045] By grinding the sample on the T-holder with the formed inclination angle to form a sample with a bevel structure, the top, middle, and bottom of the TSV structure of the sample can be presented simultaneously; then perform FIB processing on the ground sample with the bevel structure to form a transmission electron microscope sample, and the structures of the top, middle, and bottom of the sample can be observed simultaneously. The method of the present invention applies the T-holder to the TSV, which can increase the speed and convenience of FIB execution, reduce the number of grinding times and the number of times of entering and exiting the FIB machine, thereby shortening the preparation time of the transmission electron microscope sample, improving the efficiency of the FIB machine, and increasing the output rate of the transmission electron microscope sample.

[0046] According to the present invention, optionally, the sample containing the TSV structure cut from the wafer is a sample at the position of the wafer test structure as shown in Figure 3 , the thickness of the sample containing the TSV structure is 120-150 nm; the depth of the TSV structure is 60-80 μm.

[0047] According to the present invention, optionally, as shown in Figure 4 , the step of adhering the sample to the U-shaped fork includes: placing a piece of glass at the front end of the U-shaped fork, coating a hot melt adhesive on the glass to form an adhesive layer, and adhering the sample on the adhesive layer.

[0048] According to the present invention, optionally, as shown in Figure 5 and Figure 6 , the T-shaped bracket is provided with adjusting feet. Dip the front end of the U-shaped fork adhered with the sample in water, place a piece of glass on the T-shaped bracket, and rotate the adjusting feet by observing the water mark on the glass to adjust the sample and the T-shaped bracket to a horizontal state, which can reduce the errors generated during the subsequent process.

[0049] According to the present invention, optionally, as shown in Figure 7 , the length (L) of the T-shaped bracket is 3-5 cm, the height (h) of one end of the T-shaped bracket is 1-2 cm, and the inclination angle (α) is 11.53°-41.82°. Through the above embodiments, the sample on the T-shaped bracket can be ground to form a bevel structure, so that the top, middle and bottom of the TSV structure of the sample can be presented simultaneously, which is convenient for observing the structures of different parts of the sample at the same time.

[0050] The calculation formula for the inclination angle is: α = arcsin(h / L). For example, the length (L) of the T-shaped bracket can be 4 cm, and the height (h) of one end of the T-shaped bracket can be 2 cm. According to the calculation formula for the inclination angle, the inclination angle (α) can be 30°.

[0051] According to the present invention, optionally, the grinding step includes: grinding the sample with 1000#, 2000# and 4000# water sandpapers (the water sandpaper needs to be ground with water) until the middle part of the TSV structure is exposed. Before changing to a different type of water sandpaper after each grinding, the ground place needs to be brushed clean with clean water, and then grind with 1 μm and 0.5 μm diamond sandpapers until the bottom of the TSV structure is exposed to form the sample with the bevel structure, see Figure 8 ; the included angle between the bevel and the horizontal plane is 11.53°-41.82°, as shown in Figure 9As shown, it is possible to simultaneously present the top, middle, and bottom of the TSV structure of the sample, reducing the number of grinding times and the number of subsequent entries and exits of the FIB machine, thereby shortening the transmission electron microscope sample preparation time and increasing the output rate of transmission electron microscope samples. By fixing the sample on a T-shaped bracket and cooperating with the selection of water sandpaper and diamond sandpaper to grind the sample, the flatness of grinding is ensured. Further, since the diamond sandpaper is relatively thin, the sample is likely to be damaged due to the unevenness of the grinding disc during grinding. Before grinding with the diamond sandpaper, a glass gasket is placed on the grinding disc, and then the diamond sandpaper is selected and placed on the glass gasket, so that the diamond sandpaper is flatly attached to the glass gasket. By placing a smooth glass gasket between the diamond sandpaper and the grinding disc, it is avoided that the grinding disc wears the sample through the diamond sandpaper during grinding, ensuring the quality of grinding.

[0052] According to the present invention, optionally, the depth of the middle part of the TSV structure of the sample after grinding is 30 - 40 μm, and the depth of the bottom part of the TSV structure is 2 - 5 μm. Through the above implementation manner, it is convenient to observe the middle and bottom parts of the TSV structure.

[0053] According to the present invention, optionally, the steps of FIB processing include: placing the sample with the bevel structure into the FIB machine, marking and selecting a target area on the surface of the sample with the bevel structure, the target area containing the TSV structure, depositing a platinum protection layer in the marked area, digging holes on the front and back sides of the platinum protection layer, forming grooves on the front and back sides of the platinum protection layer, the depth of the grooves being able to expose the TSV structure, using an ion beam to thin the sample in the grooves to an ideal thickness, and cutting off the bottom and two side walls of the sample in the grooves to form the transmission electron microscope sample. The steps such as marking and selecting the target area, depositing the platinum protection layer, forming the grooves, and thinning with an ion beam in the FIB processing of the present invention are all well-known technical means to those skilled in the art and will not be elaborated here.

[0054] According to the present invention, optionally, the FIB machine further includes a focused electron beam structure. During the process of using FIB processing to form a transmission electron microscope sample, the morphology of the transmission electron microscope sample is observed using the focused electron beam.

[0055] The second aspect of the present invention provides a transmission electron microscope sample, which is prepared by the method provided in the first aspect of the present invention.

[0056] According to the present invention, optionally, the transmission electron microscope sample includes a TSV structure; the transmission electron microscope sample must be very thin for easy observation by transmission electron microscopy. For example, the thickness of the transmission electron microscope sample can be 70 - 90 nm; at the same time, the prepared transmission electron microscope sample has a bevel structure. Through the above embodiments, the morphology structure and defect positions of different parts on the sample can be clearly observed simultaneously by a focused electron beam on the FIB machine stage, further avoiding subsequent type defects and improving the product yield and device reliability.

[0057] The following further illustrates the present invention through examples, but the present invention is not limited thereby.

[0058] Example 1

[0059] The method for preparing a transmission electron microscope sample according to the present invention includes the following steps:

[0060] S1. Cut out a sample containing a TSV structure from a wafer and adhere the sample to the front end of a U-shaped fork. Specifically: place a piece of glass at the front end of the U-shaped fork, coat a hot melt adhesive on the glass to form an adhesive layer, and adhere the sample on the adhesive layer; wherein, the thickness of the sample containing the TSV structure is 140 nm; the depth of the TSV structure is 70 μm;

[0061] S2. Fix the U-shaped fork with the adhered sample on a T-shaped bracket; adjustment feet are symmetrically arranged at one end of the T-shaped bracket opposite to the sample. Dip the front end of the U-shaped fork with the adhered sample in water, place a piece of glass on the T-shaped bracket, and rotate the adjustment feet by observing the water marks on the glass to adjust the sample and the T-shaped bracket to a horizontal state;

[0062] S3. Adjust the height of one end of the T-shaped bracket so that the T-shaped bracket forms an inclination angle with the horizontal plane; wherein, the length L of the T-shaped bracket is 4 cm, and the height h of one end is 2 cm. According to the calculation formula of the inclination angle, the inclination angle α is 30°;

[0063] S4. Grind the sample on the T-shaped bracket with the formed inclination angle. The specific grinding process is as follows: grind the sample with 1000#, 2000#, and 4000# water sandpapers respectively until the middle part of the TSV structure is exposed, and then grind with 1 μm and 0.5 μm diamond sandpapers respectively until the bottom of the TSV structure is exposed to form a sample with a bevel structure; after grinding, the depth of the middle part of the TSV structure of the sample is 35 μm, the depth of the bottom is 4 μm, and the included angle between the bevel and the horizontal plane is 30°;

[0064] S5. Process the sample with a bevel structure after grinding by FIB. The specific processing procedure is as follows: Place the sample with the bevel structure into the FIB machine stage, mark and select the target area on the surface of the sample with the bevel structure, deposit a platinum protection layer in the marked area, form grooves on the front and back sides of the platinum protection layer. The depth of the grooves can expose the side walls of the TSV structure. Use an ion beam to thin the sample in the grooves to an ideal thickness, cut off the bottom and two side walls of the sample in the grooves to form the transmission electron microscope sample. Among them, the transmission electron microscope sample has a bevel structure, and the thickness of the transmission electron microscope sample is 80 nm. Observe the morphology of the transmission electron microscope sample using a focused electron beam. As Figure 10 shown, the morphologies of different parts of the TSV structure of the sample can be seen.

[0065] Example 2

[0066] The method for preparing the transmission electron microscope sample in this example is the same as that in Example 1, except that the height h of one end of the T-shaped bracket is adjusted to 0.7 cm. According to the calculation formula of the tilt angle, the tilt angle α is 10.08°. The angle between the bevel of the sample after grinding and the horizontal plane is 10.08°, and the depth of the middle part of the TSV structure of the sample is 35 μm. The bottom of the TSV structure of the sample in this example cannot be well presented, which will increase the number of grinding times and extend the time for subsequent preparation of the transmission electron microscope sample.

[0067] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0068] In addition, it should be noted that, in the case of no contradiction, the various specific technical features described in the above specific embodiments can be combined in any suitable way. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0069] In addition, any combination can be made between different embodiments of the present invention as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a transmission electron microscope sample, characterized in that, the method comprises: S1. Cutting out a sample containing a TSV structure from a wafer and adhering the sample to a U-shaped fork; S2. Fixing the U-shaped fork with the adhered sample on a T-shaped bracket; S3. Adjusting the sample and the T-shaped bracket to a horizontal state; S4. Adjusting the height of one end of the T-shaped bracket to form an inclination angle between the T-shaped bracket and the horizontal plane; S5. Grinding the sample on the T-shaped bracket with the formed inclination angle to form a sample with a bevel structure; S6. Performing FIB processing on the sample with the bevel structure after grinding to form the transmission electron microscope sample.

2. The method according to claim 1, wherein, the depth of the TSV structure is 60 - 80 μm.

3. The method according to claim 1, wherein, the step of adhering the sample to the U-shaped fork comprises: Placing a piece of glass at the front end of the U-shaped fork, coating a hot melt adhesive on the glass to form an adhesion layer, and adhering the sample on the adhesion layer.

4. The method according to claim 1, wherein, the T-shaped bracket is provided with adjusting feet. Wet the front end of the U-shaped fork with the adhered sample, place a piece of glass on the T-shaped bracket, and rotate the adjusting feet by observing the water marks on the glass to adjust the sample and the T-shaped bracket to a horizontal state.

5. The method according to claim 1, wherein, the length of the T-shaped bracket is 3 - 5 cm, the height of one end of the T-shaped bracket is 1 - 2 cm, and the inclination angle is 11.53° - 41.82°.

6. The method according to claim 1, wherein, the grinding step comprises: Grinding the sample with water sandpaper until the middle part of the TSV structure is exposed, and then grinding with diamond sandpaper until the bottom of the TSV structure is exposed to form the sample with the bevel structure, so that the top, middle and bottom of the TSV structure of the sample are presented simultaneously.

7. The method according to claim 6, wherein, the angle between the bevel and the horizontal plane is 11.53° - 41.82°.

8. The method according to claim 6, wherein, after grinding, the depth of the middle part of the TSV structure of the sample is 30 - 40 μm, and the depth of the bottom of the TSV structure is 2 - 5 μm.

9. The method according to claim 1, wherein, the FIB processing step comprises: Making marks on the surface of the sample with the bevel structure, depositing a platinum protection layer in the marked area, forming grooves on the front and back sides of the platinum protection layer, thinning the sample in the grooves to an ideal thickness by using an ion beam, and cutting off the bottom and two side walls of the sample in the grooves to form the transmission electron microscope sample.

10. A transmission electron microscope sample, characterized in that, it is prepared by using the method according to any one of claims 1 - 9.

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