A decapping method and experimental method for failure analysis of integrated circuit base island area

Abstract

The present application relates to an opening method and experimental method for failure analysis of the base island area of ​​an integrated circuit. The opening method includes the following steps: S1: using laser opening to remove the plastic encapsulation material on the upper surface of the chip until the upper surface of the chip and a portion of the bonding wires are exposed; S2: using chemical etching to remove the residual plastic encapsulation material above the chip and in the bonding wire area; S3: cutting the bonding wires and moving the two cut bonding wires to a vertical state; S4: covering the chip with a laser shield; S5: continuing to use the laser to remove the plastic encapsulation material above the base island until the upper surface of the base island is exposed. This application mostly uses the laser method to remove the plastic encapsulation material, and a small part uses the chemical method to remove the plastic encapsulation material. Overall, it still maintains a high processing efficiency. The chemical method also has minimal impact on the chip and surrounding structures, and will not affect the judgment of failure problems. It takes into account the balance between opening efficiency and damage.

Description

Technical Field

[0001] The present application relates to the technical field of integrated circuit failure analysis experiments, and in particular to a method for opening a cover and an experimental method for failure analysis of an integrated circuit base island region. Background Art

[0002] The integrated circuit base island area carries a variety of materials such as chips, die-bonding glue, bonding wires, etc., and involves a variety of packaging processes. Therefore, most failure anomalies occur in the base island area. To conduct reliability testing or failure analysis on the base island area, the integrated circuit needs to be decapped (Decap, also known as opening or uncapping). There are two main traditional decapping methods. One is to use chemicals to corrode the plastic packaging material. The chemical decapping method has low quality, long processing time, and is not environmentally friendly. The base island area is more inclined to the bottom of the integrated circuit relative to the chip area. During failure analysis, it takes longer for the chemicals to decap to the base island area, which can easily damage the structure of the base island area. For example, it can easily cause the silver plating layer in the base island area to corrode and fall off, and reduce the bonding strength between the die-bonding glue and the base island. , affecting the quality characteristics of the base island area, which is not conducive to failure analysis and judgment; the second is to use laser to remove the plastic packaging material. Laser opening has the advantages of good opening effect, high efficiency, and good consistency. It has obvious advantages, but the bonding wires of the integrated circuit will block the laser, resulting in the plastic packaging material under the bonding wires being difficult to remove. The residual plastic packaging material will affect the experimental results. If the chemical method is used to remove these residual plastic packaging materials, the problems described in method one will occur again. It is necessary to develop a new opening method for failure analysis of the integrated circuit base island area to reduce the impact of the opening process on the base island area. Summary of the Invention

[0003] In order to solve the technical problem that the existing integrated circuit decapping method easily causes damage to the quality characteristics of the base island area and affects the judgment of failure problems, the present invention provides a decapping method for failure analysis of the base island area of ​​an integrated circuit.

[0004] The present application provides the following technical solution: a method for removing the plastic encapsulation material above the integrated circuit base island for failure analysis, comprising the following steps:

[0005] S1: Use laser decapping to remove the plastic encapsulation material on the upper surface of the chip until the upper surface of the chip and part of the bonding wire are exposed;

[0006] S2: Use chemical corrosion to remove the residual plastic packaging material above the chip and the bonding wire area;

[0007] S3: Cut the bonding wire and move the two cut bonding wires to a vertical state;

[0008] S4: Cover the chip with a laser shield;

[0009] S5: Continue to use the laser to remove the plastic sealing material above the base island until the upper surface of the base island is exposed.

[0010] By adopting the above technical solution, the present application first uses a laser to open the cover to remove the plastic encapsulation material on the upper surface of the chip, exposing the upper surface of the chip and a part of the bonding wire. Since a large amount of plastic encapsulation material needs to be removed at this stage, the laser method is adopted to ensure high efficiency, and the contact time between the laser and the chip is short, which has minimal impact on the chip and surrounding structures. Since the height of the bonding wire is higher than the upper surface of the chip, the bonding wire will block the laser, resulting in some plastic encapsulation material remaining under the bonding wire. The present application uses chemical etching to remove the residual plastic encapsulation material above the chip and in the bonding wire area. Since the amount of residual plastic encapsulation material is very small, the time required for processing is also short. The chip is shorter, and the side of the chip is still wrapped by the plastic packaging material at this time, and the impact on the chip and the surrounding structures is also minimal. After the residual plastic packaging material under the bonding wire is removed, the bonding wire can be cut off, and then the two cut bonding wires can be adjusted to a vertical state. In this state, the bonding wire will not block the laser, and the laser can continue to be used to remove a large amount of plastic packaging material above the base island until the upper surface of the base island is exposed to ensure high efficiency. In addition, since the chip is exposed at this time, in order to avoid the impact of the laser on the chip and the surrounding structures, especially covering the laser shielding material above the chip, the laser will not have much impact on the chip during the subsequent laser irradiation. This application mostly uses the laser method to remove the plastic packaging material, and a small part uses the chemical method to remove the plastic packaging material. On the whole, it still maintains a high processing efficiency. The chemical method has little impact on the chip and the surrounding structures, and will not affect the judgment of the failure problem. It takes into account the balance between the opening efficiency and damage.

[0011] Preferably, after step S5, the following steps are further included: S6, adjusting the two cut bonding wires to a vertical state again; S7: continuing to use laser to remove the residual plastic packaging material above the base island.

[0012] By adopting the above technical solution, since the bonding wires below the upper surface of the chip are still bent and will still block the laser during the processing, there will still be residual plastic molding compound under the bonding wires. If a thrust test of the bonding joints is to be performed, the plastic molding compound needs to be further removed. If the plastic molding compound is removed by chemical methods, it will cause damage and affect the quality characteristics of the base island area. Therefore, this application will adjust the two cut sections of the bonding wires to a vertical state; continue to use the laser to remove the residual plastic molding compound above the base island, which can reduce the impact on the bonding wires and the base island area.

[0013] Preferably, in step S3, the bonding wire is cut using a tensile test hook.

[0014] By adopting the above technical solution, the tensile test hook is a commonly used tool for cutting bonding wires.

[0015] Preferably, the laser shield is a metal plate or a ceramic plate, fixed on the chip by adhesive.

[0016] By adopting the above technical solution, the laser shield can be easily fixed on the upper surface of the chip.

[0017] Preferably, the bonding wire is an aluminum ribbon bonding wire.

[0018] By adopting the above technical solution, since the aluminum strip welding wire has a larger surface area than the cylindrical wire, it can block a larger area of ​​laser, and the amount of residual plastic packaging material is larger. The effect of laser opening in the existing technology is worse, and it is more necessary to use the opening method described in this application to perform the opening operation.

[0019] The present application provides an experimental method for failure analysis of the base island area of ​​an integrated circuit, which adopts the following technical solution: an experimental method for failure analysis of the base island area of ​​an integrated circuit, first using the above-described opening method to open the cover on the integrated circuit, completely exposing the base island, chip, die-bonding glue and bonding solder joints, and then using corresponding test tools to test or measure the base island, chip, die-bonding glue and bonding solder joints.

[0020] Preferably, a thrust test tool is used to perform a thrust test on the chip or the bonding joint.

[0021] Preferably, the quality of the bonding joints is observed using a microscope.

[0022] By adopting the above-mentioned technical solution, the uncovering method for integrated circuit base island area failure analysis described in this application can be applied to various base island area failure analysis experiments. First, the cover is opened on the integrated circuit using the above-mentioned uncovering method to completely expose the base island, chip, die-bonding glue and bonding solder joints, and then the base island, chip, die-bonding glue and bonding solder joints are tested or measured using corresponding test tools.

[0023] In summary, this application includes at least one of the following beneficial technical effects:

[0024] 1. This application mostly uses lasers to remove the plastic encapsulation material, and a small part uses chemicals to remove the plastic encapsulation material. Overall, the processing efficiency is still relatively high. The chemical method has minimal impact on the chip and surrounding structures, and will not affect the judgment of failure issues. It takes into account the balance between decapping efficiency and damage.

[0025] 2. The decapping method for failure analysis of the integrated circuit base island area described in this application can be applied to various base island area failure analysis experiments, such as testing or measuring experiments on the base island, chip, die-bonding adhesive, and bonding solder joints. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1A flow chart of the cover opening method described in Example 1 of the present application is depicted;

[0027] Figure 2 A schematic diagram of the structure of the integrated circuit described in this application when the cover is not opened is depicted;

[0028] Figure 3 A schematic diagram of the state after processing in step S1 of the first embodiment of the present application is depicted;

[0029] Figure 4 A schematic diagram of the state after processing in step S2 of the first embodiment of the present application is depicted;

[0030] Figure 5 A schematic diagram of the state after processing in step S3 of the first embodiment of the present application is depicted;

[0031] Figure 6 A schematic diagram of the state after processing in step S4 of the first embodiment of the present application is depicted;

[0032] Figure 7 A schematic diagram of the state after processing in step S5 of the first embodiment of the present application is depicted;

[0033] Figure 8 A flow chart of the cover opening method described in Example 2 of the present application is depicted;

[0034] Figure 9 A schematic diagram of the state of the second embodiment of the present application after processing in step S6 is depicted;

[0035] Figure 10 A schematic diagram of the state of the second embodiment of the present application after processing in step S7 is depicted.

[0036] Explanation of the accompanying symbols: 1. base island; 2. plastic packaging material; 3. chip; 4. bonding wire; 5. die-bonding glue; 6. laser shield. DETAILED DESCRIPTION

[0037] The following is combined with Figure 1-10 This application is described in further detail.

[0038] Example 1:

[0039] Reference Figures 1 to 7 The embodiment of the present application discloses a method for removing the plastic encapsulation material 2 above the integrated circuit base island 1 for failure analysis, comprising the following steps:

[0040] S1: Reference Figure 3 , using laser decapping to remove the plastic encapsulation material 2 on the upper surface of the chip 3 until the upper surface of the chip 3 and a portion of the bonding wire 4 are exposed;

[0041] S2: Reference Figure 4, using chemical corrosion to remove the residual plastic packaging material 2 above the chip 3 and the bonding wire 4 area;

[0042] S3: Reference Figure 5 , cut the bonding wire 4, and move the two cut bonding wires 4 to a vertical state;

[0043] S4: Reference Figure 6 , covering the laser shield 6 above the chip 3;

[0044] S5: Reference Figure 7 , continue to use laser to remove the plastic packaging material 2 above the base island 1 until the upper surface of the base island 1 is exposed.

[0045] In this embodiment, in step S1, a laser decapping machine is used to decap. In step S2, the chemical used can be industrial dilute hydrochloric acid, dilute sulfuric acid, or the like. In step S3, a tensile test hook is used to cut the bonding wires 4. The laser shield 6 is a metal or ceramic plate, secured to the chip 3 with adhesive backing, making it easy to secure the laser shield 6 to the top surface of the chip 3.

[0046] In the present application, the bonding wire 4 can be made of a common cylindrical gold wire, aluminum wire, or copper wire, or an aluminum ribbon wire. Because the aluminum ribbon wire has a larger surface area than a cylindrical wire, it can block a larger area of ​​laser light, resulting in a larger amount of residual plastic molding compound 2. Consequently, the laser decapping effect of the prior art is poor, and the decapping method described in the present application is more desirable.

[0047] Because the bonding wires 4 below the top surface of the chip 3 are still bent and block the laser during processing, residual molding compound 2 may remain beneath the bonding wires 4. If only measuring the thickness of the die-bonding adhesive 5 or performing a thrust test on the chip 3 is required, this residual molding compound 2 will not affect the test results and can be left in place. If a thrust test is performed on the bonding joints, further molding compound 2 removal is required. The specific removal method is described in the next embodiment.

[0048] The present application first uses a laser to open the cover to remove the plastic encapsulation material 2 on the upper surface of the chip 3, exposing the upper surface of the chip 3 and a portion of the bonding wire 4. Since a large amount of plastic encapsulation material 2 needs to be removed at this stage, the laser method is used to ensure high efficiency, and the time the laser contacts the chip 3 is short, which has minimal impact on the chip 3 and surrounding structures. Since the height of the bonding wire 4 is higher than the upper surface of the chip 3, the bonding wire 4 will block the laser, resulting in some plastic encapsulation material 2 remaining below the bonding wire 4. The present application uses chemical etching to remove the residual plastic encapsulation material 2 above the chip 3 and in the bonding wire 4 area. Since the amount of residual plastic encapsulation material 2 is very small, the time required for processing is also short, and At this time, the side of the chip 3 is still wrapped by the plastic encapsulation material 2, and the impact on the chip 3 and the surrounding structures is also very small. After the residual plastic encapsulation material 2 below the bonding wire 4 is removed, the bonding wire 4 can be cut off, and then the two cut sections of the bonding wire 4 can be adjusted to a vertical state. In this state, the bonding wire 4 will not block the laser, and the laser can continue to be used to remove a large amount of plastic encapsulation material 2 above the base island 1 until the upper surface of the base island 1 is exposed to ensure high efficiency. In addition, since the chip 3 is already exposed at this time, in order to avoid the impact of the laser on the chip 3 and the surrounding structures, a laser shield 6 is especially covered above the chip 3. In the subsequent laser irradiation, the laser will not have much impact on the chip 3. This application mostly uses the laser method to remove the plastic encapsulation material 2, and a small part uses the chemical method to remove the plastic encapsulation material 2. Overall, a high processing efficiency is still maintained. The chemical method has a very small impact on the chip 3 and the surrounding structures, and will not affect the judgment of the failure problem, taking into account the balance between the opening efficiency and damage.

[0049] Example 2:

[0050] Reference Figures 8 to 10 , which is different from the first embodiment in that the following steps are further included after step S5: S6, adjusting the two cut bonding wires 4 to a vertical state again; S7: continuing to use laser to remove the residual plastic packaging material 2 above the base island 1.

[0051] Since the bonding wires 4 below the top surface of the chip 3 are still bent and will still block the laser during processing, there will still be residual plastic molding compound 2 below the bonding wires 4. Since the top surface of the base island 1 is now completely exposed, the plastic molding compound 2 can no longer be removed using chemicals, otherwise it will cause damage and affect the quality characteristics of the base island 1 area. Therefore, in this embodiment, the two cut sections of the bonding wires 4 are adjusted to a vertical state; and the laser is continued to be used to remove the residual plastic molding compound 2 above the base island 1. It is precisely because the length of the bent section of the bonding wire 4 is greatly shortened at this time that it is easier to peel off. (If the bonding wire 4 is not cut off at the beginning and the upper half of the bonding wire 4 is not adjusted to a vertical state, then there will be too much plastic molding compound 2 below the complete bonding wire 4, making it difficult to peel off the bonding wire 4).

[0052] The uncovering method for failure analysis of the integrated circuit base island 1 area described in this application can be applied to various experiments for failure analysis of the base island 1 area. First, use the uncovering method described above to open the cover on the integrated circuit to completely expose the base island 1, chip 3, die-bonding glue 5 and bonding solder joints, and then use corresponding test tools to test or measure the base island 1, chip 3, die-bonding glue 5 and bonding solder joints.

[0053] For example, when the thrust of the chip 3 or the bonding solder joints needs to be tested, after opening the cover, a conventional thrust test can be performed on the chip 3 or the bonding solder joints using a thrust test tool.

[0054] For example, when it is necessary to judge whether the quality of the bonding solder joints is qualified, after opening the cover, the quality of the bonding solder joints is observed using a microscope and a judgment is made.

[0055] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A method for removing the plastic packaging material (2) above the integrated circuit base island (1) for failure analysis of the integrated circuit base island area, characterized in that: The following steps are involved: S1: using a laser to open the cover to remove the plastic packaging material (2) on the upper surface of the chip (3) until the upper surface of the chip (3) and a portion of the bonding wire (4) are exposed; S2: using chemical reagents to erode and remove the residual plastic packaging material (2) above the chip (3) and the bonding wire (4) area; S3: Cutting the bonding wire (4), and moving the two cut bonding wires (4) to a vertical state; S4: Covering the chip (3) with a laser shield (6); S5: Continue to use the laser to remove the plastic packaging material (2) above the base island (1) until the upper surface of the base island (1) is exposed.

2. The method for decapping the integrated circuit base island region failure analysis according to claim 1, characterized in that: After step S5, the following steps are also included: S6, adjusting the two cut sections of bonding wires (4) to a vertical state again; S7: continuing to use laser to remove the residual plastic packaging material (2) above the base island (1).

3. The method for decapping the integrated circuit base island region failure analysis according to claim 1, characterized in that: In step S3, the bonding wire (4) is cut using a tensile test hook.

4. The method for decapping an integrated circuit base island region failure analysis according to claim 1, characterized in that: The laser shield (6) is a metal plate or a ceramic plate, and is fixed on the chip (3) via adhesive backing.

5. The method for decapping the integrated circuit base island region failure analysis according to claim 1, characterized in that: The bonding wire (4) is an aluminum ribbon bonding wire.

6. An experimental method for failure analysis of integrated circuit base island area, characterized in that: First, use the uncovering method described in any one of claims 1 to 5 to uncover the integrated circuit, completely exposing the base island (1), chip (3), die-bonding glue (5) and bonding solder joints, and then use corresponding testing tools to test or measure the base island (1), chip (3), die-bonding glue (5) and bonding solder joints.

7. The experimental method for failure analysis of integrated circuit base island region according to claim 6, characterized in that: A thrust test tool is used to perform a thrust test on the chip (3) or the bonding solder joint.

8. The experimental method for failure analysis of integrated circuit base island region according to claim 6, characterized in that: The quality of the bonding solder joints was observed using a microscope.

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