Reliability evaluation method of bonding wire

Abstract

The invention relates to a bonding wire reliability evaluation method, which comprises the following steps: aiming at a plurality of different bonding wires stored based on a preset storage condition, selecting a preset number of bonding wires from the plurality of different bonding wires as sample bonding wires, and obtaining storage result data of each sample bonding wire; carrying out profile cutting on the welding spot of each bonding wire and then carrying out profile analysis to obtain profile analysis data of each bonding wire; and determining a reliability evaluation result of the bonding wires based on the storage result data of each sample bonding wire and the profile analysis data of each bonding wire. According to the invention, the reliability of the bonding wire can be evaluated so as to ensure that the integrated circuit chip has normal signal transmission performance and electrical performance, and the production effect of the integrated circuit chip is improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a reliability evaluation method for bonding wires. Background Art

[0002] The bonding wire is used to provide the interconnection between the chip and the substrate, and is the most important part of all parts used to achieve the interconnection between the chip and the substrate. In production, the wire (gold wire or aluminum wire) is bonded to the pad at the bottom of the chip through the ultrasonic vibration generated by the piezoelectric transducer and the pressure of the bonding tool, thereby interconnecting the chip and the substrate.

[0003] The reliability of bonding wires directly affects the performance of integrated circuit chips. If bonding wires are broken, detached, or have poor contact, the signal transmission and electrical performance of integrated circuit chips will be directly affected. In order to ensure that integrated circuit chips have normal signal transmission and electrical performance, the reliability of bonding wires must be evaluated.

[0004] How to evaluate the reliability of bonding wires to ensure that integrated circuit chips have normal signal transmission performance and electrical performance and improve the production effect of integrated circuit chips still needs to be solved. Summary of the invention

[0005] Based on this, it is necessary to provide a reliability evaluation method for bonding wires to evaluate the reliability of bonding wires in order to ensure that the integrated circuit chip has normal signal transmission performance and electrical performance and improve the production effect of the integrated circuit chip.

[0006] A reliability evaluation method for a bonding wire, comprising:

[0007] For a plurality of different bonding wires stored based on preset storage conditions, a preset number of bonding wires are selected from the plurality of different bonding wires as sample bonding wires, and storage result data of each sample bonding wire is obtained;

[0008] Performing cross-section cutting on the solder joint of each bonding wire and then performing cross-section analysis to obtain cross-section analysis data of each bonding wire;

[0009] Based on the storage result data of each sample bonding wire and the profile analysis data of each bonding wire, the reliability evaluation result of the bonding wire is determined.

[0010] In one embodiment, the factors for classifying the types of bonding wires include at least one of wire material, wire diameter, bonding accuracy, spacing between adjacent wires, longest wire arc capability, arc height accuracy, minimum arc height, or maximum welding area.

[0011] In one embodiment, the step of performing cross-section cutting and then cross-section analysis on the solder joints of each bonding wire includes:

[0012] For each bonding wire, a cutting position is selected at the solder joint of the bonding wire;

[0013] Cutting the metal layer formed at the welding point at the cutting position to obtain a cutting sample;

[0014] The cut sample is subjected to cross-sectional analysis, which includes optical analysis and / or microscopic analysis.

[0015] In one embodiment, the step of selecting a cutting position at a solder joint of a bonding wire comprises:

[0016] Remove the solder ball at the solder joint, and use the removal position of the solder ball on the pad as the cutting position.

[0017] In one embodiment, the step of selecting a cutting position at a solder joint of a bonding wire comprises:

[0018] In the case where the solder ball at the solder joint is not removed, the position where the solder ball contacts the pad is selected as the cutting position.

[0019] In one embodiment, there are multiple cutting positions; cutting the metal layer formed at the welding point at the cutting position to obtain a cutting sample includes:

[0020] According to a preset cutting sequence between a plurality of cutting positions, the metal layer is cut at each cutting position in turn to obtain a cutting sample corresponding to each cutting position.

[0021] In one embodiment, after determining the reliability evaluation result of the bonding wire, the method further includes:

[0022] If the reliability evaluation result is that the bonding wire is unreliable, returning to the step of selecting a preset number of bonding wires from the plurality of different bonding wires stored based on the preset storage conditions, until the reliability evaluation result of the bonding wire is determined again;

[0023] If the reliability assessment result of the bonding wire is that the bonding wire is reliable, the step of selecting a preset number of bonding wires from the plurality of different bonding wires stored based on the preset storage conditions is stopped.

[0024] In one embodiment, the preset storage conditions include a preset storage temperature and a preset storage time; wherein the preset storage temperature is a temperature in the range of 100 degrees Celsius to 150 degrees Celsius, and the preset storage time is a time in the range of 900 hours to 1000 hours.

[0025] In one embodiment, the stored result data includes tensile test data and / or physical morphology data.

[0026] In one embodiment, after determining the reliability evaluation result of the bonding wire, the method further includes:

[0027] When the reliability evaluation result indicates that the bonding wire is unreliable, an alarm is issued, and the reliability evaluation result, the stored result data, and the profile analysis data are displayed.

[0028] The above-mentioned reliability assessment method of the bonding wires, on a packaging production line that has passed the QML certification, combines the reliability assessments of a variety of different bonding wires on the packaging production line to provide a reliability assessment of the bonding wires on the packaging production line. The reliability assessment performed by the method provided in this embodiment is not an assessment of the reliability of one bonding wire, but a reliability assessment of a variety of bonding wires on the packaging production line. If the reliability assessments of a variety of bonding wires on the packaging production line are good, then the reliability assessments of all bonding wires on the packaging production line that has passed the QML certification are good. Conversely, if the reliability assessment of any bonding wire on the packaging production line fails, then the reliability assessments of all bonding wires on the packaging production line that has passed the QML certification fail, and at this time the packaging production line needs to be rectified. After the rectification, the reliability assessment of the bonding wires can be performed again until the reliability assessment of any bonding wire solder joint selected on the packaging production line passes.

[0029] Therefore, the method provided in this embodiment can ensure that the integrated circuit chip has normal signal transmission performance and electrical performance by evaluating the reliability of the bonding wire, thereby improving the production effect of the integrated circuit chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG1 is a schematic flow chart of a method for evaluating the reliability of a bonding wire in one embodiment;

[0031] FIG2 is a schematic flow chart of a method for evaluating the reliability of a bonding wire in yet another embodiment;

[0032] FIG3 is a schematic flow chart of a method for evaluating the reliability of a bonding wire in another embodiment;

[0033] FIG. 4 is a schematic flow chart of a method for evaluating the reliability of a bonding wire in yet another embodiment. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0035] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," and the like may be used herein to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that, in addition to the orientations shown in the figures, spatially relative terms also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is flipped, an element or feature described as "under other elements" or "under it" or "under it" will be oriented as being "above" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. In addition, the device may also include additional orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptors used herein are interpreted accordingly.

[0036] A bonding wire is a thin metal wire that is tightly connected to a pad on a chip or substrate through a specific process (such as hot pressing, ultrasonic welding, or thermoacoustic welding) to achieve electrical interconnection. Its main function is to provide a reliable electrical connection between the chip and the external circuit to ensure accurate signal transmission. In production, the wire (gold wire or aluminum wire) is bonded to the pad at the bottom of the chip through the ultrasonic vibration generated by the piezoelectric transducer and the pressure of the bonding tool, thereby interconnecting the chip to the substrate. The reliability of the bonding wire directly affects the performance of the integrated circuit chip. If the bonding wire breaks, falls off, or has poor contact, it will directly affect the signal transmission and electrical performance of the integrated circuit chip.

[0037] Therefore, in order to ensure that the integrated circuit chip has normal signal transmission performance and electrical performance, the reliability of the bonding wires must be evaluated.

[0038] Based on this, the present application provides a reliability evaluation method for a bonding wire, which is described in detail in various embodiments below.

[0039] In an exemplary embodiment, as shown in FIG1 , a reliability assessment method for a bonding wire is provided, comprising the following steps 101 to 103. In which:

[0040] Step 101 : for a plurality of different bonding wires stored based on preset storage conditions, a preset number of bonding wires are selected from the plurality of different bonding wires as sample bonding wires, and storage result data of each sample bonding wire is obtained.

[0041] The preset storage condition may include a preset storage temperature and a preset storage time. The preset storage temperature may be a temperature in the range of 100 degrees Celsius (°C) to 150°C. The preset storage time may be a time in the range of 900 hours (h) to 1000 hours. Preferably, the preset storage temperature may be 125°C. Preferably, the preset storage time may be 1000 hours.

[0042] Among them, when dividing into multiple different bonding wires, the factors for dividing the types of bonding wires may include at least one of the wire material, wire diameter, bonding accuracy, spacing between adjacent wires, longest wire arc capability, arc height accuracy, minimum arc height or maximum welding area.

[0043] The bonding wire process capability of a typical packaging production line is shown in Table 1. In addition to gold wire and copper wire bonding, there are also silver wire bonding and aluminum wire wedge bonding. The wire diameters of the bonding wires vary. The material components of the bonding wires provided by suppliers of different brands are also different, and the failure mechanisms produced during bonding may also be different.

[0044] Table 1:

[0045]

[0046] In accordance with the standard elements of GJB 546B-2011 "Outline for Quality Assurance of Electronic Components" and the standard requirements of GJB 7400-2011 "General Specification for Semiconductor Integrated Circuits for Qualified Manufacturer Certification", the Qualified Manufacturer Listing (QML) certification of the packaging production line is carried out from the aspects of on-site document control, organizational structure and personnel setup, process document control capability, procurement and material control capability, equipment control capability, production process control capability, and quality assurance capability.

[0047] Different types of bonding wires require roughly the same process parameters during packaging production line certification. This article takes CQFP (Ceramic Quad Flat Pack) and CDIP (Ceramic Dual In-line Package) packaging as examples. For CQFP packaging, the parameter data required during packaging production line certification is shown in Table 2. For CDIP packaging, the parameter data required during packaging production line certification is shown in Table 3.

[0048] Table 2:

[0049]

[0050] Table 3:

[0051]

[0052] When selecting a preset number of bonding wires, three bonding wires may be selected as sample bonding wires.

[0053] After high-temperature storage, the bonding wires may be subjected to a tensile force analysis and a physical morphology analysis. Correspondingly, the storage result data may include tensile force test data and / or physical morphology data.

[0054] For example, when performing a tensile analysis, a micro force sensor may be used to perform a tensile test on the bonding wire.

[0055] Step 102 , performing cross-section cutting and then cross-section analysis on the solder joints of each bonding wire to obtain cross-section analysis data of each bonding wire.

[0056] The cross-section analysis is used to perform optical analysis or microscopic analysis on the cross-section formed after cutting.

[0057] When the solder joint is cut into sections, the section can be made directly below the solder ball, or the section can be made at the position where the solder ball is pushed off after the solder ball is pushed off. In an exemplary embodiment, the section formed can also be cold buried, ground and polished.

[0058] The profile analysis data includes spectral data, fluorescence data, interference data, etc. obtained after optical analysis. The profile analysis data also includes microscopic image data and quantitative data (such as size, quantity, composition, dynamic data, etc.) obtained after microscopic analysis.

[0059] Step 103 , determining a reliability evaluation result of the bonding wire based on the storage result data of each sample bonding wire and the cross-sectional analysis data of each bonding wire.

[0060] If the storage result data and the profile analysis data indicate that the bonding wire has undergone a worse change under the preset storage condition, it can be determined that the reliability assessment result of the bonding wire is that the bonding wire is unreliable.

[0061] If the storage result data and the profile analysis data indicate that the change of the bonding wire under the preset storage condition is within the expected range and the change is not significant, then it can be determined that the reliability assessment result of the bonding wire is that the bonding wire is reliable.

[0062] The reliability assessment method of the bonding wire provided in the present embodiment combines the reliability assessment of multiple different bonding wires on the packaging production line that has passed the QML certification, thereby providing a reliability assessment of the bonding wires on the packaging production line. The reliability assessment performed by the method provided in the present embodiment is not an assessment of the reliability of one bonding wire, but a reliability assessment of multiple bonding wires on the packaging production line. If the reliability assessments of multiple bonding wires on the packaging production line are good, then the reliability assessments of all bonding wires on the packaging production line that has passed the QML certification are good. Conversely, if the reliability assessment of any bonding wire on the packaging production line fails, then the reliability assessments of all bonding wires on the packaging production line that has passed the QML certification fail, and at this time the packaging production line needs to be rectified. After the rectification, the reliability assessment of the bonding wires can be performed again until the reliability assessment of any bonding wire solder joint selected on the packaging production line passes.

[0063] Therefore, the method provided in this embodiment can ensure that the integrated circuit chip has normal signal transmission performance and electrical performance by evaluating the reliability of the bonding wire, thereby improving the production effect of the integrated circuit chip.

[0064] In an exemplary embodiment, as shown in FIG2 , step 102 includes steps 201 to 203. Among them:

[0065] Step 201 : for each bonding wire, select a cutting position at the solder joint of the bonding wire.

[0066] The cutting position may be on the solder ball at the solder joint, or may be at the position where the solder ball contacts the solder pad.

[0067] When the cutting position is on the solder ball, it can be at a position such as half or one third of the solder ball.

[0068] In an exemplary embodiment, when selecting the cutting position, the solder ball at the solder joint can be removed, and the position where the solder ball is removed on the pad is used as the cutting position. Optionally, a chip shearing instrument can be used to push off the solder ball.

[0069] In an exemplary embodiment, when selecting the cutting position, the position where the solder ball contacts the solder pad may be selected as the cutting position without removing the solder ball at the solder joint.

[0070] Step 202, cutting the metal layer formed at the welding point at the cutting position to obtain a cutting sample.

[0071] The metal layer is, for example, a gold-aluminum compound layer, such as aluminum and aluminum forming a connecting metal layer.

[0072] When the metal layer is cut, a diamond band saw or a diamond wheel saw may be used to cut the metal layer, or a focused ion beam technique may be used to cut the metal layer. Other methods may also be used for cutting, which are not limited in this embodiment.

[0073] Step 203: Perform cross-sectional analysis on the cut sample, wherein the cross-sectional analysis includes optical analysis and / or microscopic analysis.

[0074] Before performing cross-sectional analysis on the cut sample, the cut sample may be polished to improve the accuracy of optical analysis results and microscopic analysis results.

[0075] Data obtained after optical analysis include spectral data, fluorescence data, interference data, etc. Data obtained after microscopic analysis include microscopic image data, quantitative data (such as size, quantity, composition, dynamic data, etc.).

[0076] The method provided in this embodiment performs a cross-sectional analysis on the cut samples to determine the changes in the solder joints of the bonding leads after storage under preset storage conditions, thereby providing a reliability assessment of the bonding leads on the packaging production line. The reliability assessment performed by the method provided in this embodiment is not an assessment of the reliability of one bonding lead, but a reliability assessment of multiple bonding leads on the packaging production line. If the reliability assessments of multiple bonding leads on the packaging production line are good, then the reliability assessments of all bonding leads on the packaging production line that has passed the QML certification are good. Conversely, if the reliability assessment of any bonding lead on the packaging production line fails, then the reliability assessments of all bonding leads on the packaging production line that has passed the QML certification fail, and the packaging production line needs to be rectified.

[0077] Therefore, the method provided in this embodiment can ensure that the integrated circuit chip has normal signal transmission performance and electrical performance, and improve the production effect of the integrated circuit chip by performing reliability assessment on the bonding wire through cross-section analysis of the bonding wire.

[0078] In some embodiments, when there are multiple cutting positions, step 202 includes:

[0079] Step 301 , according to a preset cutting sequence between a plurality of cutting positions, the metal layer is cut at each cutting position in turn to obtain a cutting sample corresponding to each cutting position.

[0080] For example, the multiple cutting positions include a first cutting position, a second cutting position, and a third cutting position, and the preset cutting order is to first cut at the first cutting position, then cut at the second cutting position, and finally cut at the third cutting position. Then, the first cutting position is first selected, and the metal layer is cut for the first time at the first cutting position to obtain a first cutting sample. Then, the second cutting position is selected, and the metal layer is cut for the second time at the second cutting position to obtain a second cutting sample. Then, the third cutting position is selected, and the metal layer is cut for the third time at the third cutting position to obtain a third cutting sample.

[0081] The cutting sequence can be changed according to actual needs to flexibly adapt to the requirements of profile analysis.

[0082] In some embodiments, after determining the reliability evaluation result of the bonding wire, the reliability evaluation method of the bonding wire further includes:

[0083] Step 401, if the reliability evaluation result is that the bonding wire is unreliable, return to the execution step of selecting a preset number of bonding wires from a plurality of different bonding wires stored based on preset storage conditions until the reliability evaluation result of the bonding wire is determined again.

[0084] If the reliability assessment result is that the bonding wire is unreliable, the production line is rectified. After the rectification, the reliability of the rectified bonding wire needs to be evaluated again. When the reliability of the rectified bonding wire is evaluated again, return to step 101 to step 103 to determine the reliability assessment result of the bonding wire. If the reliability assessment result determined again is still that the bonding wire is unreliable, return to step 101 to step 103 again. Until the reliability assessment result determined to be that the bonding wire is reliable, it is proved that the rectification has achieved the purpose, and then stop executing steps 101 to step 103.

[0085] Step 402, if the reliability assessment result of the bonding wire is that the bonding wire is reliable, then stop executing the step of selecting a preset number of bonding wires from the plurality of different bonding wires stored based on the preset storage conditions.

[0086] As long as the reliability evaluation result of the bonding wire is that the bonding wire is reliable, the execution of steps 101 to 103 is stopped. If the bonding wire is determined to be reliable when the steps 101 to 103 are executed for the first time, the execution of steps 101 to 103 does not need to be returned.

[0087] In an exemplary embodiment, when the reliability assessment result is that the bonding wire is unreliable, an alarm is issued. The alarm may be a whistle alarm, a flashing light alarm, or other forms of alarm, which are not limited in this embodiment. When the reliability assessment result is that the bonding wire is unreliable, the reliability assessment result, the storage result data, and the profile analysis data may also be displayed to facilitate the staff to analyze the rectification direction and rectify the production line.

[0088] The method provided in the above embodiment provides a prompt when the bonding wire is unreliable so that the staff can rectify the production line in time. The method provided in this embodiment can also re-evaluate the reliability of the bonding wire after the production line is rectified to improve the reliability of the bonding wire.

[0089] The reliability evaluation method of the bonding wire provided in the above embodiment can ensure that the bonding wire works reliably during its life cycle through the reliability evaluation of the bonding wire process, thereby ensuring that the integrated circuit chip works reliably during its life cycle. In addition, the QML certification based on the packaging process guides the contractor to pay more attention to the entire process of product realization, puts forward higher requirements on the bonding wire process capabilities of circuit manufacturers, and promotes the development of the bonding wire reliability design technology and reliability evaluation technology of monolithic integrated circuits (integrated circuit chips).

[0090] The technical features of the above embodiment can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above embodiment are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0091] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A reliability evaluation method for a bonding wire, characterized in that: include: For a plurality of different bonding wires stored based on preset storage conditions, a preset number of bonding wires are selected from the plurality of different bonding wires as sample bonding wires, and storage result data of each sample bonding wire is obtained; Performing cross-section cutting on the solder joint of each bonding wire and then performing cross-section analysis to obtain cross-section analysis data of each bonding wire; Based on the storage result data of each sample bonding wire and the profile analysis data of each bonding wire, the reliability evaluation result of the bonding wire is determined.

2. The method according to claim 1, characterized in that The factors for classifying the bonding wires include at least one of wire material, wire diameter, bonding accuracy, spacing between adjacent wires, longest wire arc capability, arc height accuracy, minimum arc height or maximum welding area.

3. The method according to claim 1, characterized in that The step of performing cross-section cutting and cross-section analysis on the solder joints of each bonding wire includes: For each bonding wire, a cutting position is selected at the solder joint of the bonding wire; Cutting the metal layer formed at the welding point at the cutting position to obtain a cutting sample; The cut sample is subjected to cross-sectional analysis, which includes optical analysis and / or microscopic analysis.

4. The method according to claim 3, characterized in that The step of selecting a cutting position at a solder joint of a bonding wire comprises: Remove the solder ball at the solder joint, and use the removal position of the solder ball on the pad as the cutting position.

5. The method according to claim 3, characterized in that: The step of selecting a cutting position at a solder joint of a bonding wire comprises: In the case where the solder ball at the solder joint is not removed, the position where the solder ball contacts the pad is selected as the cutting position.

6. The method according to claim 3, characterized in that There are multiple cutting positions; the metal layer formed at the welding point is cut at the cutting position to obtain a cutting sample, including: According to a preset cutting sequence between a plurality of cutting positions, the metal layer is cut at each cutting position in turn to obtain a cutting sample corresponding to each cutting position.

7. The method according to any one of claims 1 to 6, characterized in that: After determining the reliability evaluation result of the bonding wire, the method further includes: If the reliability evaluation result is that the bonding wire is unreliable, returning to the step of selecting a preset number of bonding wires from the plurality of different bonding wires stored based on the preset storage conditions, until the reliability evaluation result of the bonding wire is determined again; If the reliability assessment result of the bonding wire is that the bonding wire is reliable, the step of selecting a preset number of bonding wires from the plurality of different bonding wires stored based on the preset storage conditions is stopped.

8. The method according to any one of claims 1 to 6, characterized in that: The preset storage conditions include a preset storage temperature and a preset storage time; wherein the preset storage temperature is a temperature in the range of 100 degrees Celsius to 150 degrees Celsius, and the preset storage time is a time in the range of 900 hours to 1000 hours.

9. The method according to any one of claims 1 to 6, characterized in that: The stored result data includes tensile test data and / or physical morphology data.

10. The method according to any one of claims 1 to 7, characterized in that: After determining the reliability evaluation result of the bonding wire, the method further includes: When the reliability evaluation result indicates that the bonding wire is unreliable, an alarm is issued, and the reliability evaluation result, the stored result data, and the profile analysis data are displayed.

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