Method for detecting cracks in semiconductor devices and related wire bonding systems

Abstract

A method for detecting cracks in semiconductor elements on a wire bonding system is provided. This method includes (a) placing semiconductor elements on a wire bonding system, and (b) detecting whether there are cracks in the semiconductor elements on the wire bonding system.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims the benefit of U.S. Provisional Application No. 63 / 526,054, filed on July 11, 2023, the content of which is incorporated herein by reference.

[0002] The present invention relates to a method for detecting cracks in semiconductor devices and related wire bonding systems.

Background Art

[0003] In the electronics assembly industry, wire bonding has continued to be a major method for providing electrical interconnects between two (or more) locations within a workpiece. In a typical wire bonding application, a wire bonding tool (e.g., a capillary bonding tool for ball bonding applications, a wedge bonding tool for wedge bonding applications, etc.) is used to bond the first end of a wire to a first bonding location to form a first bond. Next, the wire continuous with the first bond is extended towards a second bonding location. Then, a second bond (continuous with the first bond and the wire) is formed at the second bonding location. Thus, a wire loop is formed between the first bonding location and the second bonding location. During the formation of wire bonds, various types of energy (e.g., ultrasonic, thermo - ultrasonic, thermo - compression, etc.) may be used in relation to the bonding force and / or heat.

[0004] The occurrence of cracks in semiconductor devices (e.g., semiconductor dies) is a concern in the electronics assembly industry. The occurrence of such cracks is often a concern in relation to overhanging dies (e.g., unsupported portions of semiconductor dies in semiconductor devices). However, cracks can occur in any type of semiconductor package or device.

[0005] U.S. Patents 10,121,759 and 10,665,564 (both titled “On-Bonder Automated Overhang Die Optimization Tool Wire Bonding and Related Methods”) relate to techniques for optimizing wire bonding operations related to unsupported portions of semiconductor devices (e.g., overhang dies). [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Unfortunately, the presence and / or formation of cracks in semiconductor devices often go undetected until time and / or effort associated with the semiconductor device (e.g., performing wire bonding work associated with the semiconductor device) has been wasted. Therefore, it is desirable to improve crack detection in semiconductor devices. [Means for solving the problem]

[0007] According to exemplary embodiments of the present invention, a method for detecting cracks in semiconductor elements on a wire bonding system is provided. This method includes (a) placing semiconductor elements on a wire bonding system, and (b) detecting whether cracks are present in the semiconductor elements on the wire bonding system.

[0008] According to other embodiments of the present invention, the method described in the preceding paragraph may have one or more of the following features: Step (b) includes determining the Z-axis position of a portion of a semiconductor element in order to detect whether the semiconductor element has a crack; Step (b) includes performing an imaging operation on a wire bonding system in order to detect whether the semiconductor element has a crack; Step (b) includes determining the Z-axis position of a deflected portion of the semiconductor element in order to detect whether the semiconductor element has a crack; Step (b) includes determining the Z-axis position of a portion of a semiconductor element during a wire bonding operation in order to detect whether the semiconductor element has a crack; Step (b) includes performing an imaging operation on a wire bonding system in order to detect whether the semiconductor element has a crack; the imaging operation includes imaging a portion of the semiconductor element (i) before a wire bond is formed on the semiconductor element and (ii) after a wire bond is formed on the semiconductor element; Step (b) includes detecting whether the semiconductor element has a crack by monitoring electrical characteristics related to the ultrasonic energy applied during the wire bonding operation, wherein the electrical characteristics are impedance values ​​related to the operation of an ultrasonic transducer. Step (b) includes the step of detecting whether a semiconductor device has a crack using a first bond head assembly of a wire bonding system, the method further including (c) bonding a wire to the semiconductor device using a second bond head assembly of a wire bonding system; and / or step (b) includes bringing a contact tool held by the first bond head assembly into contact with a deflected portion of the semiconductor device in order to detect whether a crack exists in the semiconductor device.

[0009] According to another exemplary embodiment of the present invention, a wire bonding system is provided. This wire bonding system comprises a bond head assembly configured to mount a wire bonding tool for performing wire bonding operations on a workpiece containing a semiconductor element. The wire bonding system also comprises a support structure for supporting the workpiece. Furthermore, the wire bonding system comprises a computer system configured to detect whether there is a crack in the semiconductor element on the wire bonding system.

[0010] According to other embodiments of the present invention, the wire bonding system described in the preceding paragraph may have one or more of the following features: another bond head assembly configured to mount a contact tool used in connection with detecting whether a semiconductor element has a crack; another bond head assembly configured to mount an imaging system used in connection with detecting whether a semiconductor element has a crack; a computer system configured to determine the Z-axis position of a portion of a semiconductor element in order to detect whether a semiconductor element has a crack; an imaging system mounted on a bond head assembly that performs imaging operations on the wire bonding system in connection with detecting whether a semiconductor element has a crack An imaging system configured to perform; another bond head assembly configured to image a portion of the semiconductor element (i) before a wire bond is formed on the semiconductor element, and (ii) after a wire bond is formed on the semiconductor element; a computer system configured to determine the Z-axis position of a flexed portion of the semiconductor element in order to detect whether there is a crack in the semiconductor element; the computer system configured to determine the Z-axis position of a portion of the semiconductor element during the wire bonding operation to detect whether there is a crack in the semiconductor element; the computer system configured to monitor electrical characteristics related to the ultrasonic energy applied during the wire bonding operation; and / or electrical characteristics are impedance values ​​related to the operation of the ultrasonic transducer. [Brief explanation of the drawing]

[0011] This invention is best understood by reading the following detailed description in conjunction with the accompanying drawings. Note that, as is customary, various features in the drawings are not depicted to scale. Rather, for clarity, the dimensions of various features have been arbitrarily enlarged or reduced. The drawings include the following figures. [Figure 1A]Figures 1A to 1C are block diagrams and side views showing a portion of a wire bonding system according to an exemplary embodiment of the present invention. [Figure 1B] Figures 1A to 1C are block diagrams and side views showing a portion of a wire bonding system according to an exemplary embodiment of the present invention. [Figure 1C] Figures 1A to 1C are block diagrams and side views showing a portion of a wire bonding system according to an exemplary embodiment of the present invention. [Figure 2] Figure 2 is a timing diagram showing the Z-axis profile during the formation of a wire bond in a portion of the bond head assembly of a wire bonding system, which is useful in relation to various exemplary embodiments of the present invention. [Figure 3A] Figures 3A and 3B are graphs useful in relation to various embodiments of the present invention, showing the relationship between bonding force and die deflection in relation to non-cracked and cracked semiconductor elements. [Figure 3B] Figures 3A and 3B are graphs useful in relation to various embodiments of the present invention, showing the relationship between bonding force and die deflection in relation to non-cracked and cracked semiconductor elements. [Figure 4A] Figures 4A to 4D and 5A to 5D are side and top views of a partial block diagram of another wire bonding system according to an exemplary embodiment of the present invention. [Figure 4B] Figures 4A to 4D and 5A to 5D are side and top views of a partial block diagram of another wire bonding system according to an exemplary embodiment of the present invention. [Figure 4C] Figures 4A to 4D and 5A to 5D are side and top views of a partial block diagram of another wire bonding system according to an exemplary embodiment of the present invention. [Figure 4D] Figures 4A to 4D and 5A to 5D are side and top views of a partial block diagram of another wire bonding system according to an exemplary embodiment of the present invention. [Figure 5A]Figures 4A to 4D and 5A to 5D are side and top views of a partial block diagram of another wire bonding system according to an exemplary embodiment of the present invention. [Figure 5B] Figures 4A to 4D and 5A to 5D are side and top views of a partial block diagram of another wire bonding system according to an exemplary embodiment of the present invention. [Figure 5C] Figures 4A to 4D and 5A to 5D are side and top views of a partial block diagram of another wire bonding system according to an exemplary embodiment of the present invention. [Figure 5D] Figures 4A to 4D and 5A to 5D are side and top views of a partial block diagram of another wire bonding system according to an exemplary embodiment of the present invention. [Figure 6A] Figures 6A-6B are timing diagrams showing electrical characteristics related to ultrasonic energy applied during wire bonding operations, which are useful in relation to various exemplary embodiments of the present invention. [Figure 6B] Figures 6A-6B are timing diagrams showing electrical characteristics related to ultrasonic energy applied during wire bonding operations, which are useful in relation to various exemplary embodiments of the present invention. [Figure 7] Figure 7 is a block diagram side view showing a part of yet another wire bonding system according to an exemplary embodiment of the present invention. [Figure 8] Figure 8 is a flowchart illustrating a method for detecting cracks in semiconductor elements on a wire bonding system according to various exemplary embodiments of the present invention. [Modes for carrying out the invention]

[0012] As used herein, the term "semiconductor device" shall refer to any structure that includes (or is configured to include in a later process) a semiconductor chip or die. Exemplary semiconductor devices include a substrate (e.g., a lead frame, a PCB, a carrier, etc.), a substrate on which one or more semiconductor dies are mounted, a bare semiconductor die, a packaged semiconductor device, a flip chip semiconductor device, a die embedded in a substrate, a stack of semiconductor dies, and the like. Further, semiconductor devices may include elements (e.g., spacers, substrates, etc. that are joined in a stacked die configuration) configured to be joined to a semiconductor package or otherwise included therein.

[0013] As used herein, the term "crack" may refer to an undesirable abnormal condition of a semiconductor device (e.g., a semiconductor die) configured to be wire bonded. For example, a crack may refer to a permanent or plastic deformation of the semiconductor die, such as a (partial or complete) break or dent formed in the die. In another example, a crack may refer to damage and / or voids in the semiconductor die. In yet another example, a crack may refer to a state in which a part of the semiconductor die is missing.

[0014] The term "electrical characteristics" as used herein may refer to impedance values, voltage values, current values, power consumption, and the like.

[0015] According to certain exemplary embodiments of the present invention, a method and system for detecting cracks in a semiconductor device (e.g., a semiconductor die) on a wire bonding system are provided. Certain exemplary methods for detecting such cracks in a wire bonding apparatus can be executed in real time.

[0016] In certain embodiments, a method for detecting the presence of a crack in a semiconductor element includes measuring the deflection of a portion of the semiconductor element while a force is applied (e.g., using a Z-axis encoder of a wire bonding system). In other embodiments of the present invention, a method for detecting the presence of a crack in a semiconductor element includes monitoring electrical properties related to the ultrasonic energy applied during a wire bonding operation (e.g., impedance monitoring). In other embodiments of the present invention, a method for detecting the presence of a crack in a semiconductor element utilizes an imaging system (e.g., imaging a portion of the semiconductor element before and / or after forming a wire bond on that portion). These methods, and other methods within the scope of the present invention, can be combined as needed (e.g., a combination of deflection measurement and imaging system detection, a combination of deflection measurement and electrical property monitoring, a combination of electrical property monitoring and an imaging system, etc.).

[0017] Certain methods and systems described herein enable inspection of semiconductor devices (e.g., semiconductor dies) before wire bonding is formed. Such inspection may involve checking for cracks (e.g., "die cracks") caused by processes performed before wire bonding (e.g., wafer backgrinding, dicing, die attach, probing, etc.). Furthermore, aspects of the present invention also relate to crack inspection after the wire bonding process (e.g., after wire bond formation).

[0018] Specific embodiments of the present invention detect cracks in real time using a wire bonding system (e.g., a wire bonding apparatus, a wire bonding machine, etc.). In specific embodiments, cracks in semiconductor devices are mechanically inspected before and / or after wire bonding using a wire bonding system (e.g., a wire bonding apparatus, a wire bonding machine, etc.). As described herein, in specific embodiments, ultrasonic-based crack detection (e.g., monitoring electrical properties related to ultrasonic energy applied during the wire bonding operation) and image-based crack detection (e.g., visual-based, optical-based, etc.) can be used (e.g., to detect cracks viewed from the top surface of a semiconductor device). In specific embodiments, infrared cameras, laser systems, and ultrasonic-based non-destructive sensing systems can be used for crack detection in a wire bonding system (e.g., as an alternative to or in addition to a mechanical detection mechanism).

[0019] When a wire bonding tool (e.g., one mounted on the bond head assembly of a wire bonding machine) contacts a bond pad (or other bonding location) on an unsupported portion of an overhang die (or other overhang portion of a semiconductor device), the die surface may flex downward. This flexing can cause various problems in wire bonding and / or loop forming, for example, by causing the die to vibrate when the wire bonding tool separates from the die surface after bonding. If a "crack" is present in the overhang die, the defect can adversely affect the entire semiconductor package or workpiece (e.g., excessive flexing, die fracture, etc.).

[0020] A particular aspect of the present invention relates to automatically performing in-situ crack detection, pre-bonding crack detection, and / or post-bonding crack detection. According to a particular exemplary embodiment of the present invention, a bonding program is executed using programmed bonding locations (e.g., locations on an overhang die). A bonding tool (e.g., a capillary) makes contact with each programmed bonding location (e.g., whether or not a wire is engaged with the bonding tool) using predetermined starting values ​​for specific parameters such as damping gain, contact speed (e.g., constant speed mode), and bonding force. A Z-axis encoder is used to provide data (e.g., position values ​​along the vertical "Z-axis"), which are then collected and analyzed. This data can be compared with user-defined values ​​(e.g., allowable die deflection, desired bonding force, etc.) to determine whether or not a crack is present.

[0021] Die cracks may not be apparent during the manufacturing process and may manifest as microcracks that are difficult to detect. Typically, such microcracks may not be detected until later functional testing is performed. In some cases, semiconductor devices may fail during the final functional testing of the package or final product (e.g., after sealing). Currently, functional testing is performed as an "offline" and cumbersome process. If microcracks are not detected and failure occurs during functional testing, the entire production lot may be defective. Certain embodiments described herein can detect die cracks early and prevent future failures. The ability to detect cracks in situ and / or in real time using a wire bonding system (e.g., a wire bonder) can save time and materials and significantly improve yield. The methods and systems described herein can be used to develop or optimize processes that can minimize or eliminate crack-related problems.

[0022] Throughout the drawings, the same reference number refers to the same element. Therefore, unless otherwise specified in the context, a description of a particular element related to a particular drawing is applicable throughout the entire drawing.

[0023] Referring to the drawings, Figures 1A to 1C show a wire bonding system 100. The wire bonding system 100 comprises a bond head assembly 116 for bonding one or more wires to a semiconductor element 104 (e.g., a die in a workpiece 126). The bond head assembly 116 is configured to mount a wire bonding tool 102 (e.g., a capillary, wedge bonding tool, etc.) for performing wire bonding operations on the workpiece 126 containing the semiconductor element 104. The bond head assembly 116 includes a Z-axis encoder 116c for measuring the Z-axis profile (e.g., vertical position) of the bond head assembly 116 of the wire bonding system 100. As will be understood by those skilled in the art, the bond head assembly 116 may include a plurality of elements configured to move along a plurality of axes of the wire bonding system 100 (e.g., horizontal X-axis, horizontal Y-axis, vertical Z-axis, etc.). These elements may include, for example, an ultrasonic transducer, an imaging system, a wire clamp, and various other elements. The Z-axis encoder 116c can be positioned at a desired location on the bond head assembly 116.

[0024] The wire bonding system 100 also includes a support structure 124 for supporting the workpiece 126 (including the semiconductor element 104). The wire bonding system 100 also includes a computer system 118. The computer system 118 can be configured to control the movement of the bond head assembly 116. The computer system 118 can be configured to detect whether there is a crack in the semiconductor element 104 (e.g., and / or semiconductor element 114) on the wire bonding system 100. In certain embodiments, the computer system 118 can be configured to determine the Z-axis position of a portion of the semiconductor element (e.g., a portion) and to detect whether there is a crack in the semiconductor element. In certain embodiments, the computer system 118 can be configured to communicate with an imaging system (e.g., an imaging system mounted on the bond head assembly 116) to detect whether there is a crack in the semiconductor element. In certain embodiments, the computer system 118 may be configured to monitor electrical properties (e.g., impedance values) related to the ultrasonic energy applied during the wire bonding operation.

[0025] Therefore, at least in relation to the computer system 118, the wire bonding system 100 is configured to detect whether there is a crack in the semiconductor element 104 (e.g., and / or semiconductor element 114, etc.) on the wire bonding system 100. As will be understood by those skilled in the art, the computer system 118 may be any type of computing device (e.g., a controller, a computer included as part of the wire bonding system 100, a computer system separate from the wire bonding system 100, multiple computing devices such as processors operating in relation to the wire bonding system 100, etc.).

[0026] Figures 1A to 1C show a workpiece 126 positioned on a support structure 124. While workpiece 126 is an example of a workpiece, it goes without saying that the present invention is not limited to use in relation to a specific workpiece. The present invention is broadly applicable to a wide variety of workpieces. The illustrated workpiece 126 includes a substrate 106 directly positioned on the support structure 124. A semiconductor element 114 (e.g., a "bottom die") is shown positioned on the substrate 106 using an adhesive 112 (e.g., a die attach adhesive). A spacer 110 is shown positioned on the semiconductor element 114 using an adhesive 112. A semiconductor element 104 (e.g., a "top die") is shown positioned on the spacer 110 using an adhesive 112.

[0027] Referring specifically to Figure 1A, it is shown that, prior to the wire bonding operation, a free air ball 108a (i.e., FAB) is provided at the end of the bonding tool 102 (e.g., a capillary) at a height H1 (e.g., a height relative to a reference line on the wire bonding system 100). The free air ball 108a is formed from the wire 108 (the wire 108 is positioned through the bonding tool 102). The free air ball 108a is in contact with a portion of the semiconductor element 104 (e.g., the top surface) (the top surface of the semiconductor element 104 is shown at a height H2, which is another height relative to the reference line). The semiconductor element 104 is in an "overhang" state, and the unsupported portion 104a of the semiconductor element 104 is not directly supported from below. A wire loop 108b is shown beneath the semiconductor element 104.

[0028] Referring to Figure 1B, the wire bonding tool 102 is shown in a state where it has been moved downward (i.e., along the vertical Z-axis) by applying a predetermined force in connection with a wire bonding operation (e.g., a wire loop formation operation). In Figure 1B (and other specific drawings herein), specific structures of the wire bonding system 100 (e.g., bond head assembly 116, support structure 124, computer system 118, etc.) are omitted for simplification. The free air ball 108a is shown in a deformed state as the first bond 108c (or in a crushed state in specific applications). The end of the wire bonding tool 102, moved downward, is now at a height H3, where H3 is lower than H1 (i.e., closer to the substrate 106). When the tip of the wire bonding tool 102 is at height H3, the top surface of the semiconductor element 104 is at a height H4, where H4 is lower than H2 (i.e., closer to the substrate 106). In other words, as a result of the force applied during the wire bonding process, the unsupported portion 104a of the semiconductor element 104 is deformed, altered, or bent.

[0029] Referring to Figure 1C, the wire bonding tool 102 is shown to have been moved further downward (i.e., in the vertical Z-axis direction). The unsupported portion 104a cracks, thereby forming an unsupported portion 104a' and a fractured portion 104a''. Of course, please understand that this figure is not to scale. The fractured portion 104a'' may not be completely separated from the rest of the semiconductor element 104. The end of the wire bonding tool 102, moved downward, is at a height H5, which is lower than H1 and H3 (i.e., closer to the substrate 106). When the end of the wire bonding tool 102 is at a height H5, the top surface of the semiconductor element 104 is at a height H6, which is lower than H2 and H4 (i.e., closer to the substrate 106). The height of the wire bonding tool 102 and / or the height of the top surface of the semiconductor element 104 can be used as thresholds to determine whether there is a crack in the semiconductor element 104. For example, suppose we assume that if the height of the wire bonding tool 102 is lower than height H3, it indicates that there is a crack in the semiconductor element 104. Since height H5 is lower than H3, the crack in the semiconductor element 104 can be detected using the wire bonding tool 102 that reaches height H5. For example, suppose we assume that if the height of the top surface of the semiconductor element 104 is lower than height H4, it indicates that there is a crack in the semiconductor element 104. Since height H6 is lower than H4, the crack in the semiconductor element 104 can be detected by using the fact that the top surface of the semiconductor element 104 reaches height H6. Of course, these are just examples of methods for detecting cracks in the semiconductor element 104 using the deflection of the unsupported portion of the semiconductor element 104.

[0030] Furthermore, while Figures 1A-1C show height values ​​at specific locations (e.g., the end of the bonding tool 102, the top surface of the semiconductor element 104), it should be understood that these are merely examples of height values ​​that can be monitored in relation to crack detection. According to the present invention, any suitable height value that can be monitored in relation to crack detection may be any suitable height value.

[0031] Referring to Figure 2, a graph of the vertical position of the wire bonding tool 102 during crack detection (in this case, simultaneously with the wire bonding operation) is shown. As illustrated, the Z-axis profile of the wire bonding tool 102 when cracks are present (e.g., before bonding or caused by bonding) can be distinguished from the Z-axis profile when cracks are absent (i.e., "normal"). For example, there is a clear difference between the minimum value Mc when cracks are present and the minimum value Mn when "normal".

[0032] In addition to comparing measured height values ​​(e.g., H5 and / or H6 in Figure 1C) with thresholds (e.g., H3 and / or H4 in Figure 1B), cracks can be detected as a function of the vertical position profile as a function of time. For example, if a semiconductor element bends or flexes at a faster rate than expected (e.g., before reaching a "threshold"), a crack can be detected. For example, as shown in Figure 2, the presence of a crack in a semiconductor element can be determined by comparing the slope of the profile as the bonding tool deforms the semiconductor element with a reference slope.

[0033] Referring to Figures 3A-3B, graphs of the deflection of a semiconductor element (e.g., a semiconductor die) as a function of force during crack detection (in this case, simultaneous with wire bonding). Figure 3A, in particular, shows an exemplary "normal" crack detection (and wire bonding) operation. As illustrated, the deflection of a semiconductor element (e.g., semiconductor element 104 in Figures 1A-1B) has a roughly linear relationship, where the amount of deflection is proportional to the applied force (e.g., the force applied using a wire bonding tool). It should be understood that the linear shape in Figure 3A is an approximation. In certain configurations or applications, this relationship may be nonlinear (e.g., exponential, logarithmic, or polynomial). However, this relationship can be considered a baseline (or expected relationship), from which the presence of a crack can be determined (e.g., if a specific deviation from the expected relationship occurs).

[0034] Referring to Figure 3B, the crack detection operation (simultaneous with the wire bonding operation) when a crack is present is shown. As illustrated, the relationship between the semiconductor element and the applied force (e.g., denoted as "bonding force") is linear and constant from the origin to the crack point Pc (e.g., see Figure 1C where the crack is present). At Pc, the semiconductor element cracks and / or deforms, and thereafter, the semiconductor element deflects at a greater rate as a function of the increasing force. In this way, the crack can be detected (e.g., using computer system 118).

[0035] The wire bonding system 100 can be configured to detect cracks using various techniques. For example, in certain embodiments, crack detection can be performed using a bonding tool 102 mounted on a bond head assembly 116 in combination with a computer system 118 (see, for example, Figures 1A-1C). In certain embodiments, another contact element or device can be used for crack detection. In certain embodiments, an imaging system (e.g., a camera and lighting assembly) can be used for crack detection. In certain embodiments, a combination of an imaging system, a bonding tool, and / or a contact element can be used for crack detection.

[0036] The wire bonding system 100' is shown in Figures 4A to 4D and Figures 5A to 5D. Unless otherwise noted, the descriptions of the wire bonding system 100 in relation to Figures 1A to 1C also apply to the wire bonding system 100'. The wire bonding system 100' is substantially the same as the wire bonding system 100, except that it includes an imaging system 120. Note that in some figures, some structural elements of the wire bonding system 100' (e.g., bond head assembly 116, support structure 124, computer system 118, etc.) are omitted for simplification.

[0037] Figures 4A-4D and 5A-5D show a “non-overhang” configuration of the semiconductor elements 104 / 114 and the substrate 106 (in contrast to the application example shown in Figures 1A-1C). In Figures 4A-4D and 5A-5D, the workpiece 128 is placed on a support structure 124 (not shown in Figures 4B-4D and 5B-5D). The semiconductor element 114 (e.g., “bottom die”) is placed on the substrate 106 using adhesive 112 (e.g., die attach adhesive). The semiconductor element 104 (e.g., “top die”) is placed on the semiconductor element 114 using adhesive 112.

[0038] Figures 4A–4D show the use of the imaging system 120 in applications where no cracks were detected. A bond head assembly (e.g., bond head assembly 116, another bond head assembly, etc.) can be configured to mount the imaging system 120, which is used in connection with detecting whether a semiconductor element (e.g., semiconductor element 104) has cracks. In certain embodiments, the imaging system 120 is not mounted on a bond head assembly (not shown), and the imaging system 120 is configured to perform imaging operations on the wire bonding system 100' in connection with detecting whether a semiconductor element (e.g., semiconductor element 104) has cracks. In certain embodiments, the imaging system 120 is configured to image a portion of the semiconductor element (e.g., semiconductor element 104) before a wire bond is formed on the semiconductor element (e.g., semiconductor element 104) and after a wire bond is formed on the semiconductor element.

[0039] Referring to Figures 4A-4D, a free air ball 108a (i.e., FAB) is shown at the end of the bonding tool 102 (e.g., a capillary) before the wire bonding operation. In Figure 4A, the imaging system 120 can optionally provide one or more images of the semiconductor element 104 (connected to a computer system 118, not shown) before the wire bonding operation. Such images can be used in relation to the crack detection process to compare with images taken after the wire bonding operation (see, for example, Figure 4C and the description below). In Figure 4B, the free air ball 108a is in contact with the upper surface of the semiconductor element 104 before the wire bonding operation. During the wire bonding operation, the imaging system 120 (connected to data processing hardware and associated software, such as the computer system 118 shown in Figure 1A) can provide images for real-time evaluation of crack detection. Figure 4C shows the state after the first bond 108c (or squash) has been formed (in this case, a complete wire loop similar to the wire loop 108b in Figure 4D can be formed using the first bond 108c). The bond head assembly (not shown) is moved to the right (i.e., horizontally, i.e., in the +X direction), thereby moving the wire bonding tool 102 and the imaging system 120. Figure 4C shows the imaging system 120, in conjunction with a computer system 118 (not shown), providing (e.g., the image in Figure 4D) 122(or more) after the wire bonding operation. As shown in the top view of Figure 4D, no cracks are shown in the image 122. Therefore, the wire bonding system 100' can determine that no cracks exist (and / or were not detected). This determination can be made automatically (e.g., using the computer system 118). The captured image 122 is recorded and can be displayed to the operator (e.g., machine operator, engineer, etc.).This crack detection process can utilize images taken before the wire bonding operation (see, for example, Figure 4A and the description above) and images taken after the wire bonding operation, or it can utilize only images taken after the wire bonding operation.

[0040] Figures 5A–5D illustrate the use of the imaging system 120 in applications where cracks are detected. Referring to Figure 5A, a free air ball 108a (i.e., FAB) is provided to the end of the bonding tool 102 (e.g., a capillary) before the wire bonding operation. In Figure 5A, the imaging system 120 can optionally provide one or more images of the semiconductor element (connected to a computer system 118, not shown) before the wire bonding operation. Such images can be used in relation to the crack detection process to compare with images taken after the wire bonding operation (e.g., see Figure 5C and the description below). In Figure 5B, in relation to the wire bonding operation, the free air ball 108a is in contact with the upper surface of the semiconductor element 104. During the wire bonding operation, the imaging system 120 (in conjunction with data processing hardware and associated software, such as the computer system 118 shown in Figure 1A) can provide images for evaluating crack detection in real time. During the bonding operation, a crack occurs, as indicated by the fracture portion 104a''. Figure 5C shows the state after the first bond 108c (or squash) has been formed (a complete wire loop similar to the wire loop 108b in Figure 5D can also be formed using the first bond 108c). The bond head assembly (not shown) is moved to the right (i.e., horizontally, i.e., in the +X direction), thereby moving the wire bonding tool 102 and the imaging system 120. Figure 5C shows the imaging system 120, in conjunction with a computer system 118 (not shown), providing (e.g., the image in Figure 5D) after the wire bonding operation. As shown in the top view of Figure 5C, in Figure 5D, the image 122 clearly shows a crack. Therefore, the wire bonding system 100' can determine that a crack is present. This determination can be made automatically (e.g., using the computer system 118). The captured image 122 is recorded and displayed to the operator (e.g., machine operator, engineer, etc.).This crack detection process can utilize images taken before the wire bonding operation (see, for example, Figure 5A and the description above) and images taken after the wire bonding operation, or it can utilize only images taken after the wire bonding operation.

[0041] It should be understood that the imaging system 120 can take on various embodiments. For example, the imaging system 120 may include an optical camera that uses visible light. In another example, the imaging system 120 may include an infrared camera. In yet another example, the imaging system 120 may include a laser system. In yet another example, the imaging system may use electromagnetic radiation (e.g., X-rays) that can penetrate semiconductor elements.

[0042] Referring to Figures 6A and 6B, illustrative graphs of electrical characteristics related to ultrasonic detection are shown. Figure 6A shows a graph of the ultrasonic current as a function of time. The ultrasonic current applied (e.g., to the transducer of the bond head assembly) during "normal" operation (i.e., when there are no cracks in the semiconductor device) is denoted by the reference letter IAn. The ultrasonic current applied when there are cracks in the semiconductor device (or when cracks are present) is denoted by the reference letter IAc. As shown in the figure, the applied current IAc fluctuates during wire bonding operations where cracks are present. In contrast, the applied current IAn remains relatively constant throughout the wire bonding operation when no cracks are present. Such current information can be used in crack detection processes (e.g., using computer system 118).

[0043] Referring to Figure 6B, an exemplary plot of impedance as a function of time is shown. The impedance under "normal" operation (i.e., when there are no cracks in the semiconductor element) (e.g., the impedance to the transducer of the bond head assembly) is indicated by the reference letter ZAn. The impedance when there are cracks in the semiconductor element is indicated by the reference letter ZAc. As shown in the figure, if cracks are present during the wire bonding operation (e.g., due to discontinuities at the bond location), the impedance ZAc fluctuates. In contrast, the applied current ZAn remains relatively constant throughout the wire bonding operation (indicated by the relatively flat portion indicated by ZAn in the plot). Such impedance information can be used in a crack detection process (e.g., using computer system 118).

[0044] As shown in Figures 6A-6B, ultrasonic current or impedance (or both) can be used to detect the presence of cracks (e.g., during wire bonding). However, it should be understood that other electrical properties (e.g., voltage) can also be used for crack detection.

[0045] Referring to Figure 7, a wire bonding system 200 is shown. The wire bonding system 200 includes a crack detection system 202 and a wire bonding system 206. The wire bonding system 200 also includes a support structure 210 for supporting a workpiece (e.g., a substrate, a semiconductor device, a die, etc.) and a material transport system 204. The crack detection system 202 includes a bond head assembly 116a which includes an imaging system 120. The bond head assembly 116a is configured to mount the imaging system 120 which is used to detect whether there is a crack in the semiconductor device (e.g., as in the technology illustrated and described in relation to Figures 4A-4D and 5A-5D). The bond head assembly 116a is configured to support and / or transport a contact tool 208. The contact tool 208 may be a bonding tool (e.g., a capillary) or another tool (e.g., a contact element that is not a bonding tool). The contact tool 208 can be used to detect whether a semiconductor device has a crack (for example, as illustrated and described in relation to Figures 1A-1C).

[0046] The wire bonding system 206 includes a bond head assembly 116b that supports the bonding tool 102. The wire bonding system 206 is similar in many ways to the wire bonding system 100 shown in Figures 1A-1C. Therefore, unless otherwise noted (or unless the differences are evident from the context), much of the description relating to the wire bonding system 100 is also applicable to the wire bonding system 206. For example, the bond head assembly 116b is similar to the bond head assembly 116 (i.e., in Figures 1A-1C).

[0047] Bond head assemblies 116a and 116b can be placed in a common area or in separate areas (e.g., separate compartments) as indicated by vertical dashed lines. The material transport system 204 can move the workpiece 126 / 128 (including the semiconductor element 104) from the crack detection system 202 to the wire bonding system 206. In one example, after the workpiece 126 / 128 is indicated to have "passed" the crack detection test (e.g., using the imaging system 120, the contact tool 208, or one or more of the other processes described herein), the workpiece 126 / 128 can be moved to the wire bonding system 206 for wire bonding work. Bond head assemblies 116a and 116b can be electronically and communicatively coupled to the computer system 118. Thus, the computer system 118 can instruct bond head assembly 116b not to bond the semiconductor element 104 (e.g., of workpiece 126 / 128) if a crack is detected.

[0048] It should be understood that various embodiments are possible for the system shown in Figure 7. For example, multiple imaging systems 120 can be used (for example, at least one imaging system 120 can be used for the crack detection system 202 for pre-bonding work, and at least one imaging system 120 can be used for the wire bonding system 206 for bonding and post-bonding work).

[0049] Figure 8 is a flowchart illustrating a method for detecting cracks in semiconductor elements on a wire bonding system. As those skilled in the art will understand, certain steps included in the flowchart are omittable, certain steps can be added, and the order of the steps can be changed from the order shown. All of these are within the scope of the present invention.

[0050] In step 800, the semiconductor element is placed on a wire bonding system (e.g., wire bonding system 100 in Figures 1A-1C). In step 802, the semiconductor element on the wire bonding system is detected (e.g., determined) for cracks. In an optional step 802A (which may be part of step 802), the Z-axis position (e.g., during the wire bonding operation) of a portion of the semiconductor element (e.g., a flex portion) is determined to detect whether the semiconductor element has cracks (see, for example, Figures 1A-1C, Figure 2, and Figures 3A-3B). In an optional step 802B (which may be part of step 802), an imaging operation is performed on the wire bonding system to detect whether the semiconductor element has cracks (see, for example, Figures 4A-4D, and Figures 5A-5D). In certain embodiments, the imaging operation includes imaging a portion of the semiconductor element before and after the wire bond is formed on the semiconductor element. In an optional step 802C (which may be part of step 802), electrical properties related to the ultrasonic energy applied during the wire bonding operation are monitored to detect whether there are cracks in the semiconductor device (see, for example, Figures 6A–6B). In certain embodiments, the electrical properties are impedance values ​​related to the operation of the ultrasonic transducer. It should be understood that any of steps 802A, 802B, or 802C (individually or in combination) can be used for crack detection. In step 804, the wire is bonded to the semiconductor device using a second bond head assembly of the wire bonding system (see, for example, wire loop 108b in Figures 4D and 5D). Step 802 includes detecting whether there are cracks in the semiconductor device using a first bond head assembly of the wire bonding system. In certain embodiments, step 802 includes detecting whether there are cracks in the semiconductor device by bringing a flexed portion of the semiconductor device into contact with a contact tool held by the first bond head assembly.

[0051] Although the present invention is illustrated and described herein with reference to specific embodiments, the present invention is not limited to the illustrated details, and various modifications can be made to the details within the scope of the equivalents of the claims and without departing from the present invention.

Claims

1. A method for detecting cracks in semiconductor devices on a wire bonding system, (a) A step of providing the semiconductor element onto the wire bonding system, (b) A step of detecting whether there is a crack in the semiconductor element on the wire bonding system, A method of having.

2. A method according to claim 1, wherein step (b) includes determining the Z-axis position of a portion of the semiconductor element to detect whether or not there is a crack in the semiconductor element.

3. A method according to claim 2, wherein step (b) includes performing an imaging operation on the wire bonding system to detect whether the semiconductor element has a crack.

4. A method according to claim 1, wherein step (b) includes determining the Z-axis position of the bent portion of the semiconductor element to detect whether or not there is a crack in the semiconductor element.

5. A method according to claim 1, wherein step (b) includes determining the Z-axis position of a portion of the semiconductor element during a wire bonding operation to detect whether or not there is a crack in the semiconductor element.

6. A method according to claim 1, wherein step (b) includes performing an imaging operation on the wire bonding system to detect whether the semiconductor element has a crack.

7. A method according to claim 6, wherein the imaging operation includes the steps of (i) imaging a part of the semiconductor element before forming a wire bond on the semiconductor element, and (ii) imaging a part of the semiconductor element after forming a wire bond on the semiconductor element.

8. A method according to claim 1, wherein step (b) includes monitoring electrical properties related to ultrasonic energy applied during a wire bonding operation to detect whether a crack exists in the semiconductor element.

9. The method according to claim 8, wherein the electrical characteristic is an impedance value related to the operation of the ultrasonic transducer.

10. A method according to claim 1, wherein step (b) includes detecting whether a crack exists in the semiconductor element using a first bond head assembly of the wire bonding system, and the method further includes (c) bonding a wire to the semiconductor element using a second bond head assembly of the wire bonding system.

11. A method according to claim 10, wherein step (b) includes bringing a flexed portion of the semiconductor element into contact with a contact tool held by a first bond head assembly to detect whether the semiconductor element has a crack.

12. A wire bonding system, A bond head assembly configured to mount a wire bonding tool for performing a wire bonding operation on a workpiece containing semiconductor elements, A support structure for supporting the aforementioned workpiece, The computer system, configured to detect whether there is a crack in the semiconductor element on the wire bonding system, A wire bonding system having [a specific feature / feature].

13. A wire bonding system according to claim 12, further comprising another bond head assembly, the other bond head assembly being configured to mount a contact tool used for detecting whether a crack exists in the semiconductor element.

14. A wire bonding system according to claim 12, further comprising another bond head assembly, the other bond head assembly being configured to incorporate an imaging system used to detect whether the semiconductor element has a crack.

15. A wire bonding system according to claim 12, wherein the computer system is configured to determine the Z-axis position of a part of the semiconductor element and to detect whether or not there is a crack in the semiconductor element.

16. A wire bonding system according to claim 12, further comprising an imaging system attached to a bond head assembly, wherein the imaging system is configured to perform imaging operations on the wire bonding system in connection with detecting whether or not there is a crack in the semiconductor element.

17. A wire bonding system according to claim 16, wherein the imaging system is configured to image a part of the semiconductor element (i) before forming a wire bond on the semiconductor element, and (ii) after forming a wire bond on the semiconductor element.

18. A wire bonding system according to claim 12, wherein the computer system is configured to determine the Z-axis position of the bent portion of the semiconductor element and to detect whether or not there is a crack in the semiconductor element.

19. A wire bonding system according to claim 12, wherein the computer system is configured to determine the Z-axis position of a part of the semiconductor element during the wire bonding operation and to detect whether or not there is a crack in the semiconductor element.

20. A wire bonding system according to claim 12, wherein the computer system is configured to monitor electrical properties related to ultrasonic energy applied during a wire bonding operation.

21. A wire bonding system according to claim 20, wherein the electrical characteristics are impedance values ​​related to the operation of an ultrasonic transducer.

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