Method of optimizing the clamping of semiconductor elements against a support structure on a wire bonder and related method

Abstract

A method of adjusting the clamping of a semiconductor element against a support structure on a wire bonder is provided. The method includes: (a) detecting a suspension indicator of the semiconductor element relative to the support structure at a plurality of locations of the semiconductor element; and (b) adjusting the clamping of the semiconductor element against the support structure based on the results of step (a).

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 001,415, filed March 29, 2020, the contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to wire bonding operations, and more particularly to techniques for clamping semiconductor devices onto a wire bonding machine. Background Technology

[0004] In semiconductor device manufacturing and packaging, wire bonding has always been the primary method for providing electrical interconnects between two locations within a package (e.g., between a die pad and a lead in a leadframe). More specifically, using a wire bonder (also called a wire bonder), wire loops are formed between the respective locations to be electrically interconnected. The main methods for forming wire loops are ball bonding and wedge bonding. Various different types of bonding energies can be used in the bonding portion between (a) the end of the formed wire loop and (b) the bonding location (e.g., die pad, lead, etc.), including, for example, ultrasonic energy, thermo-ultrasonic energy, thermo-pressure energy, etc. Wire bonders (e.g., cylindrical bumpers) are also used to form conductive bumps from portions of wire.

[0005] Such wire bonders typically include a device clamping system (sometimes also called a "device holder," "clamping insert," "window holder," etc.) (hereinafter referred to as a "device holder"). The device holder holds semiconductor components (e.g., lead frames comprising multiple semiconductor dies) in place against the support structure of the wire bonder. In this way, the semiconductor components are ready for wire bonding operations.

[0006] However, sometimes the semiconductor device is not properly clamped against the support structure. For example, part of the semiconductor device may be clamped loosely, tightly, or both. Wire bonder operators often use trial and error to ensure the semiconductor device is properly clamped against the support structure. This trial-and-error method leads to defects in the wire bonding operation.

[0007] Therefore, it will be desirable to provide improved technologies for controlling the clamping of devices on wire bonders. Summary of the Invention

[0008] According to an exemplary embodiment of the present invention, a method for adjusting the clamping of a semiconductor element against a support structure on a wire bonding machine is provided. The method includes: (a) detecting a suspension index of the semiconductor element relative to the support structure at multiple locations of the semiconductor element; and (b) adjusting the clamping of the semiconductor element against the support structure based on the result of step (a).

[0009] According to still another exemplary embodiment of the present application, there is provided a method of determining a desired clamping force profile for clamping a semiconductor element on a wire bonder. The method comprises: (a) clamping the semiconductor element against a support structure of the wire bonder using a device clamp of the wire bonder at a plurality of clamping force profiles; (b) detecting a float value of a plurality of locations of the semiconductor element at each of the plurality of clamping force profiles; and (c) determining the desired clamping force profile for clamping the semiconductor element on the wire bonder using data obtained from step (b).

[0010] According to still another exemplary embodiment of the present application, there is provided a method of detecting a float indicator of a portion of a semiconductor element on a wire bonder. The method comprises: (a) clamping the semiconductor element against a support structure of the wire bonder; and (b) detecting a float indicator of the portion of the semiconductor element relative to the support structure.

[0011] The method of the present application can also be embodied as an apparatus (e.g., as part of a smart component of a wire bonder), or as computer program instructions on a computer readable medium (e.g., a computer readable medium containing a wire bonding program for use in conjunction with a wire bonder). BRIEF DESCRIPTION OF DRAWINGS

[0012] The present application is best understood from the following detailed description when read in connection with the accompanying drawings. It is emphasized that, according to common practice, the various features are not necessarily drawn to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawings are the following figures:

[0013] Figure 1A is a side block diagram illustrating a wire bonder for implementing a method according to an exemplary embodiment of the present application;

[0014] Figure 1B is a top block diagram of the wire bonder of Figure 1A ; and

[0015] Figures 2A-2C is a side block diagram illustrating a float of a semiconductor element to be detected according to an exemplary embodiment of the present application;

[0016] Figures 3A-3C is a side block diagram illustrating a detection of a float indicator of a semiconductor element according to an exemplary embodiment of the present application;

[0017] Figures 4A-4C is a side block diagram illustrating a detection of a float indicator of a semiconductor element according to another exemplary embodiment of the present application;

[0018] Figures 5A-5C is a side view block diagram illustrating detection of a suspension indicator of a semiconductor element using a velocity profile, in accordance with yet another exemplary embodiment of the present application;

[0019] Figures 6A-6C is a side view block diagram illustrating detection of a suspension indicator of a semiconductor element using a force profile, in accordance with yet another exemplary embodiment of the present application;

[0020] Figure 7 is a flowchart illustrating a method of adjusting a clamp of a semiconductor element against a support structure of a wire bonder, in accordance with an exemplary embodiment of the present application;

[0021] Figure 8 is a flowchart illustrating a method of determining a desired clamp force profile for clamping a semiconductor element on a wire bonder, in accordance with an exemplary embodiment of the present application; and

[0022] Figure 9 is a flowchart illustrating a method of detecting a suspension indicator of a portion of a semiconductor element on a wire bonder, in accordance with an exemplary embodiment of the present application. DETAILED DESCRIPTION

[0023] As used herein, a "semiconductor element" is intended to refer to any structure that includes (or is configured to include in a subsequent step) a semiconductor chip or die. Exemplary semiconductor elements include a substrate (e.g., a lead frame, a PCB, a carrier, etc.), a substrate carrying one or more semiconductor dies, a bare semiconductor die, a packaged semiconductor device, a flip-chip semiconductor device, a die embedded in a substrate, a semiconductor die stack, etc. Further, a semiconductor element can include elements configured to be soldered or otherwise included in a semiconductor package (e.g., spacers, substrates, etc. to be soldered in a stacked die configuration).

[0024] As used herein, a "suspension indicator" is generally intended to refer to one or more suspension indicators. For example, a suspension indicator can be a simple indication of suspension (e.g., a suspension condition). For example, such a simple indication of suspension can be a "no suspension" condition, an "acceptable amount of suspension" condition, an "excessive suspension" condition, etc. That is, in such examples, the actual amount of suspension can not be considered. In other examples, a suspension indicator can be a value associated with suspension (e.g., an amount of suspension between a portion of a semiconductor element and a support structure). That is, a suspension indicator can relate to a distance between (i) a respective portion of a semiconductor element at each of a plurality of locations of the semiconductor element and (ii) a support structure. For example, a suspension indicator of a semiconductor element relative to a support structure can also be referred to as a suspension height determination.

[0025] According to various exemplary embodiments of the present application, semiconductor device clamping techniques are provided including methods of adjusting clamping force, methods of correcting (e.g., automatically correcting) clamping force, methods of monitoring (e.g., real-time monitoring) clamping, methods of monitoring suspension, etc. In connection with these methods, wire bonder signals can be used, for example, (i) as feedback to automatically correct optimal device clamping force, and / or (ii) as a real-time monitor of device clamping and / or a suspension indicator.

[0026] Aspects of the present application can be used to provide improved / optimized clamping of semiconductor devices, for example, to achieve wire bonding performance that meets requirements. Additionally, aspects of the present application can be used to monitor clamping and / or suspension of semiconductor devices. Further, according to aspects of the present application, if a suspension condition exists (e.g., if a suspension indicator or suspension value for a portion of a semiconductor device is not within an acceptable range), a warning indication (e.g., a machine alarm, an operator alarm, etc.) can be provided. The warning can cause an operator to check various machine hardware and functions. For example, such a suspension condition can be caused by improper clamping, material problems, substrate problems, machine conditions, etc.

[0027] According to certain exemplary embodiments of the present application, the proposed methods include an automatic correction scheme that will detect a desired (e.g., optimal) clamping force for one or more devices that are within a clamping window (i.e., a device clamp, a windowed clamp, a clamping insert).

[0028] The proposed exemplary methods also include a real-time method for monitoring any poor clamping conditions (and / or suspension values or conditions) during wire bonding to prevent yield loss.

[0029] An exemplary correction method uses wire bonder signals to determine the amount of "suspension" at various wire bonding locations at multiple clamping force levels. The desired (e.g., optimal) clamping force is determined (e.g., calculated) based on minimizing the amount of suspension.

[0030] Suspension indicators (e.g., presence or absence of a suspension condition, a suspension value, etc.) can also be determined on a wire bonder according to aspects of the present application independent of closed loop clamping force determination. Such determination of a suspension value can be provided for a variety of reasons including, but not limited to: (i) for wire bonding process analysis; (ii) for providing a warning indication (e.g., whether a suspension value is outside of an acceptable range); (iii) for adjusting (e.g., automatically adjusting) at least one wire bonding parameter of a wire bonding process (e.g., if a suspension value is outside of an acceptable range); etc.

[0031] According to one particular method of determining the levitation value, a force is applied between the wire bonding tool and the semiconductor element (e.g., a press force pressing against a support structure of the wire bonder), and a height position is recorded (i.e., a first height position). Then, the force is released (or at least reduced), and another height position is recorded (e.g., a second height position) when the position signal is stable. The difference between these two height positions can be considered as the levitation value.

[0032] In another particular method of determining the levitation value, the applied force is ramped from low to high - and a point (e.g., an inflection point) on the position curve is observed to obtain the levitation value.

[0033] In another particular method of detecting the levitation indicator, the time elapsed between a reference height (e.g., a search height) and a contact height / position is determined (while knowing the velocity profile of the wire bonding tool) when lowering the wire bonding tool towards the semiconductor element. This time can be referred to as the "CV" time - where CV stands for constant velocity. The contact height is the height at which contact between the wire bonding tool and the semiconductor element is declared to have occurred. With the time elapsed and the velocity profile (and / or other signals, such as height position signals, etc.), the levitation indicator is detected.

[0034] In another particular method of detecting the levitation indicator, a force (e.g., an impact force) is detected while lowering the wire bonding tool to generate a force profile. The force is determined when contact between the wire bonding tool and the semiconductor element is made. The determined force is correlated to the levitation indicator (e.g., with predetermined data, etc.).

[0035] For example real-time monitoring aspects of the present invention, the levitation indicator (e.g., levitation value / amount and / or levitation condition) can be monitored at programmed intervals. When a limit is exceeded, a warning or error message can be provided to the machine operator. Another option is to automatically trigger a clamp force adjustment and / or correction to obtain a desired (e.g., optimal) clamp force. Another option is to automatically trigger a soldering parameter adjustment to compensate for an adverse levitation indicator.

[0036] Figure 1A is a simplified side view of a wire bonder 100. The wire bonder includes a support structure 102 (e.g., a heated block, an anvil, etc.) for supporting a semiconductor element 104 during a wire bonding operation. In Figure 1AIn the embodiment of the application illustrated in FIG. 1, the semiconductor component 104 is a leadframe that includes a plurality of lead fingers 104b. A plurality of semiconductor dies 104a (previously mounted on the leadframe) are also included in the exemplary semiconductor component 104. The device holder 106 secures the semiconductor component 104 against the support structure 102 with a clamping force. The wire bonder 100 also includes a plurality of clamping arms 106a, 106b that are used to move the device holder 106 along the vertical axis of the wire bonder 100 and to press the device holder 106 against the semiconductor component 104 (and against the support structure 102) with a desired amount of clamping (e.g., a desired amount of clamping force, a desired amount of clamping position, etc.). Although Figure 1A While two (2) clamping arms 106a, 106b are illustrated in FIG. 1, any number of clamping arms can be employed as desired.

[0037] The device holder 106 defines a plurality of apertures 106c (sometimes only one aperture) through which wire bonding operations can be performed. For example, the semiconductor component 104 includes a plurality of semiconductor dies 104a and the device holder 106 defines a plurality of apertures 106c for access to the plurality of semiconductor dies 104a during wire bonding operations.

[0038] The wire bonder 100 also includes a wire bonding tool 108 (e.g., a capillary wire bonding tool, a wedge bonding tool, etc.) for bonding wire portions to the semiconductor component 104. As will be appreciated by those skilled in the art, the wire bonding tool 108 (carried by a bonder head assembly 110) can be moved along a plurality of axes of the wire bonder 100 to perform wire bonding operations. For example, the wire bonding tool 108 is moved along the x-axis and y-axis by movement of the bonder head assembly 110. A linkage 110a is provided between the bonder head assembly 110 and the wire bonding tool 108. The linkage 110a is configured for movement along the z-axis of the wire bonder. A z-axis position detector 112 (e.g., a z-axis encoder) is provided to detect the z-axis position of the linkage (and thus the z-axis relative position of the wire bonding tool 108) and to provide data corresponding to the z-axis position (e.g., in real time) to a computer 114 of the wire bonder 100. Thus, the computer 114 has information relating to the z-axis position of the wire bonding tool 108 through which it moves. Figure 1B is a top view of certain elements of the wire bonder 100.

[0039] Figure 2A is a simplified view of a portion of the wire bonder 100 of FIG. 1. Figures 1A-1B is a simplified view of a portion of the wire bonder 100 of FIG. 1. Figure 2B is a detailed view of a portion of the wire bonder 100 of FIG. 1. Figure 2A Figure 2B ​In this case, a portion of the semiconductor element 104 is not pressed against the support structure 102. For example, the clamping force on the semiconductor element 104 (using the device holder 106) may be too large, thus creating a "bubble" where the semiconductor element 104 is not pressed against the support structure 102. Figure 2B As shown in the diagram. The spacing between the lower surface of the semiconductor element 104 and the upper surface of the support structure 102 can be referred to as the "float value," and this spacing is... Figure 2B It is labeled "FV" in Chinese. Figure 2C In this process, the wire bonding tool 108 has been lowered to press down on this portion of the semiconductor element 104, so that this portion now contacts the support structure 102. This type of operation ( Figures 2B-2C (As shown) can be useful in conjunction with the present invention, such as regarding Figures 3A-3C , Figures 4A-4C , Figures 5A-5C and Figures 6A-6C This will be explained in more detail.

[0040] Figures 3A-3C The figure illustrates a method for detecting the floating value of a portion of semiconductor element 104. Now refer to... Figure 3A A portion 104b of the semiconductor element 104 (i.e., in the case where portion 104b is a soldered portion such as a lead) is "suspended" relative to the support structure 102. To detect the amount of suspension (sometimes referred to as the suspension value or suspension index), in... Figure 3B At this location, using the pressing pressure applied by the wire bonding tool 108, the suspended portion of the semiconductor element 104 is pressed against the support structure 102. At this position, the z-axis height is determined (see [reference needed]). Figure 1A (Z-axis position detector 112 and computer 114). This height is... Figure 3B It is shown as "h1" in the middle. Figure 3C At this point, at least a portion of the pressure is reduced to allow the previously suspended portion of the semiconductor element 104 to return to its suspended position (“neutral height”). At this position, the z-axis height is determined (see [reference needed]). Figure 1A (Z-axis position detector 112 and computer 114). This height is... Figure 3C The value is shown as "h2". In this example, h2 and h1 can be used to calculate the slack value (e.g., the slack value is h2 minus h1).

[0041] Figures 4A-4C The figure illustrates another method for detecting the floating value of a portion of semiconductor element 104. Now refer to... Figure 4A A portion 104b of the semiconductor element 104 (i.e., in the case where portion 104b is a soldered portion such as a lead) is "suspended" relative to the support structure 102. To detect the amount of suspension (sometimes referred to as the suspension value or suspension index), in...Figure 3B At this location, the wire bonding tool 108 contacts the suspended portion of the semiconductor element 104. This contact can be detected using any of a variety of techniques (e.g., constant speed detection of the wire bonding tool 108, position detection of the wire bonding tool 108, motor current detection of the z-axis motor driving the wire bonding tool 108, etc.). In any case, Figure 4B The height of the z-axis at the point of contact is known (see from [source]). Figure 1A (Z-axis position detector 112 and computer 114). This height is... Figure 4B It is shown as "h1" in the middle. Figure 4C At this location, using the pressing pressure applied by the wire bonding tool 108, the suspended portion of the semiconductor element 104 is pressed against the support structure 102. At this position, the z-axis height is determined (see [reference needed]). Figure 1A (Z-axis position detector 112 and computer 114). This height is... Figure 4C The value is shown as "h2". In this example, h2 and h1 can be used to calculate the slack value (e.g., the slack value is h1 minus h2).

[0042] Figures 5A-5C The figure illustrates a method for inspecting the suspension index of a portion 104b of a semiconductor element 104 using a wire bonding tool 108. Now refer to... Figure 5A A portion 104b of the semiconductor element 104 (i.e., where portion 104b may be a soldered portion of the semiconductor element 104, such as a lead) is "suspended" relative to the support structure 102. Figure 5A At this point, the wire bonding tool 108 is at a predetermined height h1 (e.g., sometimes also referred to as "search height," "reference height," or "end height"). That is, the predetermined height h1 is a known position (e.g., a relative position) on the wire bonding machine. At time T1 ( Figure 5A (As shown in the diagram), the wire bonding tool 108 begins to descend toward the semiconductor device 104 at a speed distribution V. Figure 5B At time T2, the wire bonding tool 108 (still traveling at speed distribution V) forms initial contact with a portion 104b of the semiconductor element 104 at height h2 (i.e., initial contact height h2). This initial contact can be detected, for example, using an electrical continuity detection process (e.g., a "BITS" process). That is, in connection with wire bonding, it is often desirable to confirm that a portion of the wire has been properly bonded to the bonding position. Wire bonding machines marketed by Kulik & Sof Industries often utilize this "BITS" process (i.e., a solder integrity test system) to confirm that a proper wire bond has been formed. International Patent Application Publication WO2009 / 002345 illustrates exemplary details of such a process and related systems, the entire contents of which are incorporated herein by reference. This BITS process can be used to detect... Figure 5BThe initial contact can be detected in any suitable manner. For example, the initial contact can be detected by using a force sensor, as shown in FIG. 1. In this example, the force sensor 110 is positioned between the support structure 102 and the wire bonding tool 108. The force sensor 110 detects the initial contact between the wire bonding tool 108 and the semiconductor element 104. Of course, other methods of detecting the initial contact can be used, such as force and / or position based methods.

[0043] At time Tl, the wire bonding tool 108 (still traveling at the velocity profile V) has continued to descend to a height h2. At time T2, the wire bonding tool 108 and the semiconductor element 104 have been declared to have made contact. The declaration of contact can be made, for example, using a predetermined change in velocity (i.e., a change due to contact). Other criteria can also be used to declare that contact has been made between the wire bonding tool 108 and the semiconductor element 104. Figure 5C At this position (i.e., at the height h2 where contact has been declared), a period of time elapses between T2-Tl. That is, the wire bonding tool 108 begins to descend at (i) time Tl and (ii) the wire bonding tool 108 and the semiconductor element 104 are declared to have made contact at time T2. In other embodiments of the present application, another period of time can be used, such as the time between T3-T2 or the time between T2-Tl.

[0044] Figure 5A At this position (i.e., at the height h2 where contact has been declared), a period of time elapses between T2-Tl. That is, the wire bonding tool 108 begins to descend at (i) time Tl and (ii) the wire bonding tool 108 and the semiconductor element 104 are declared to have made contact at time T2. In other embodiments of the present application, another period of time can be used, such as the time between T3-T2 or the time between T2-Tl. Figure 5C During the descent of the wire bonding tool 108 toward the semiconductor element 104, as shown in FIG. 1, the velocity profile V of the wire bonding tool is known. For example, the wire bonding tool 108 can travel at a constant velocity (e.g., "CV") profile between h2-h3, or some other velocity profile. Regardless, by knowing the period of time that elapses between T2-Tl (or another period of time, such as T3-T2 or T2-Tl) and the velocity profile V, a suspension indicator can be determined. For example, the suspension indicator can be a simple suspension indication. For example, such a simple suspension "indication" can be a "no suspension" condition, an "acceptable amount of suspension" condition, an "excessive amount of suspension" condition, etc. In other examples, the suspension indicator can be a value associated with the suspension (e.g., the amount of suspension between the portion 104b and the support structure 102, or see

[0045] Figures 5A-5C Figure 2B Figure 1A

[0046] Figures 6A-6C FIG. 2 illustrates another method of detecting a suspension indicator of a portion 104b of the semiconductor element 104 using the wire bonding tool 108. Referring now to FIG. 2, the wire bonding tool 108 is initially positioned at a height h4 above the semiconductor element 104. The wire bonding tool 108 is then lowered toward the semiconductor element 104. As the wire bonding tool 108 is lowered, the velocity profile V of the wire bonding tool 108 is known. For example, the wire bonding tool 108 can travel at a constant velocity (e.g., "CV") profile between h4-h5, or some other velocity profile. Regardless, by knowing the period of time that elapses between T5-T4 (or another period of time, such as T6-T5 or T5-T4) and the velocity profile V, a suspension indicator can be determined. For example, the suspension indicator can be a simple suspension indication. For example, such a simple suspension "indication" can be a "no suspension" condition, an "acceptable amount of suspension" condition, an "excessive amount of suspension" condition, etc. In other examples, the suspension indicator can be a value associated with the suspension (e.g., the amount of suspension between the portion 104b and the support structure 102, or see Figure 6A ​​​​​, a portion 104b of the semiconductor element 104 (i.e., where the portion 104b can be a solder portion of the semiconductor element 104 such as a lead) is "suspended" relative to the support structure 102. In Figure 6A , the wire bonding tool 108 is at a predetermined height hi (e.g., sometimes also referred to as a "search height" or "reference height"). That is, the predetermined height hi is a known position (e.g., relative position) on the wire bonder. At time Tl Figure 6A , the wire bonding tool 108 begins to lower toward the semiconductor element 104. While lowering the wire bonding tool 108, the force (e.g., impact force, as measured with a force sensor in the bonding head assembly of the wire bonder) is monitored (e.g., to generate a force profile including at least one force measurement). At Figure 6B , at time T2, the wire bonding tool 108 (e.g., still monitoring the force with the force sensor) makes initial contact with the portion 104b of the semiconductor element 104 at height h2 (i.e., the initial contact height h2). This initial contact can be detected, for example, with an electrical continuity detection process (e.g., a "BITS" process). Of course, other methods of detecting initial contact can be used, such as force and / or position based methods.

[0047] At Figure 6C , the wire bonding tool 108 (e.g., still monitoring the force with the force sensor) has continued to lower to height h3, where, at time T3, contact between the wire bonding tool 108 and the semiconductor element 104 has been declared. The declaration of contact can be made, for example, with a change detected using the force sensor. Of course, other methods of declaring contact can be used.

[0048] At this position (i.e., at the height h3 where contact was declared), and with the force measurements monitored using the force sensor, a suspension indicator can be learned (e.g., by correlating the measured force with the suspension indicator). For example, the suspension indicator can be a simple suspension indication. For example, such a simple suspension "indication" can be a "no suspension" condition, an "acceptable amount of suspension" condition, an "excessive suspension" condition, etc. In other examples, the suspension indicator can be a value associated with suspension (e.g., an amount of suspension between the portion 104b and the support structure 102, or see "FV" shown in Figure 2B ). That is, with information including time values (e.g., Tl, T2, T3), position values (e.g., hi, h2, h3), and measured force profiles (e.g., one or more force values detected at times such as Tl, T2, T3) - along with a computer on the wire bonder (e.g., see computer 114 in Figure 1A ), a suspension value can be calculated.

[0049] Figures 7-9is a flowchart illustrating an exemplary method according to the present application. As those skilled in the art understand, certain steps included in the flowchart can be omitted; certain additional steps can be added; and the order of the steps can be changed from that illustrated - all within the scope of the present application.

[0050] Figure 7 is a flowchart illustrating a method of adjusting the clamping of a semiconductor element against a support structure on a wire bonder. For example, the method can be implemented as part of a set-up for a wire bonding operation. In another example, the method can be repeated at predetermined intervals (e.g., time intervals, production intervals, such as a number of wire bonds processed or a number of devices, etc.).

[0051] At step 700, a suspension indicator of the semiconductor element relative to the support structure is detected at a plurality of locations of the semiconductor element. The suspension indicator can be associated with a distance between (i) a respective portion of the semiconductor element at each of the plurality of locations of the semiconductor element and (ii) the support structure.

[0052] For example, the suspension indicator of the semiconductor element relative to the support structure is a suspension height measurement. In such an example, the step of detecting the suspension height measurement can include pressing a respective portion of the semiconductor element against the support structure (e.g., as illustrated in Figure 3B ) with a pressing force applied by a wire bonding tool of the wire bonder; and releasing at least a portion of the pressing force to detect the suspension height measurement (e.g., as illustrated in Figure 3C ) at a respective one of the plurality of locations of the semiconductor element. For example, a z-axis encoder (e.g., z-axis position detector 112) is used in connection with the detection of the suspension height measurement.

[0053] In another example of step 700, the suspension indicator of the semiconductor element relative to the support structure is a different suspension height measurement. In such an example, the step of detecting the suspension height measurement can include detecting contact between a respective portion of the semiconductor element and a wire bonding tool of the wire bonder during a lowering of the wire bonding tool (e.g., as illustrated in Figure 4B ); continuing to lower the wire bonding tool while detecting a pressing of the respective portion of the semiconductor element against the support structure (e.g., as illustrated in Figure 4C ); and detecting the suspension height measurement at the respective portion of the semiconductor element using position information retrieved in a previous step. For example, a z-axis encoder (e.g., z-axis position detector 112) is used in connection with the detection of the suspension height measurement.

[0054] At step 702, the clamping of the semiconductor element against the support structure is adjusted based on the results of step 700. The adjustment can vary significantly.

[0055] For example, the adjustment at step 702 can be an adjustment of clamping implemented by a device holder. For example, if the device holder includes multiple clamping arms, step 702 can include an adjustment to at least one of the clamping arms. Such an adjustment can be an adjustment of a clamping force provided by at least one of the clamping arms and / or an adjustment of a position of at least one of the clamping arms.

[0056] For example, the adjustment at step 702 can be a replacement of a device holder of the wire bonder (with a different device holder). That is, the method of FIG. 5 can be used to determine which device holder (sometimes also referred to as a p- part) is most suitable for a given wire bonding application.

[0057] Figure 8 is a flowchart illustrating a method of determining a required clamping force distribution to clamp a semiconductor element on a wire bonder. For example, the method can be implemented as part of a setup of a wire bonding operation. In another example, the method can be repeated at predetermined intervals (e.g., time intervals, production intervals, such as a number of wire bond portions or a number of devices that have been processed, etc.).

[0058] At step 800, a semiconductor element is clamped against a support structure of a wire bonder with a plurality of clamping force distributions using a device holder of the wire bonder. At step 802, a levitation value is detected for a plurality of locations of the semiconductor element at each of the plurality of clamping force distributions. For example, the levitation value (e.g.,“FV” shown in Figure 2B is related to a distance between (i) a respective portion of the semiconductor element at each of the plurality of locations of the semiconductor element and (ii) the support structure.

[0059] For example, the step of detecting the levitation value (at step 802) can include pressing a respective portion of the semiconductor element against the support structure (e.g., as shown in Figure 3B ) using a pressing force applied by a wire bonding tool of the wire bonder; and releasing at least a portion of the pressing force to detect a levitation height measurement (e.g., as shown in Figure 3C For example, a z-axis encoder (such as z-axis position detector 112) is used in connection with the detection of the levitation value.

[0060] In another example of step 802, the step of detecting the levitation value can include detecting a contact between the respective portion of the semiconductor element and the wire bonding tool (e.g., as shown in Figure 4B ) during a lowering of the wire bonding tool of the wire bonder; continuing the lowering of the wire bonding tool while detecting a pressing of the respective portion of the semiconductor element against the support structure (e.g., as shown in Figure 4Cand the position information found during the previous step is used to detect a hover value at the corresponding portion of the semiconductor element. For example, a z-axis encoder (e.g., z-axis position detector 112) is used in connection with the detection of the hover value.

[0061] At step 804, a desired clamping force profile to clamp the semiconductor element on the wire bonder is determined using the data acquired by step 802.

[0062] The desired clamping force profile determined in step 804 can be relatively simple, such as a fixed amount of force applied by each clamping arm continuously. Alternatively, the clamping force profile can also employ different amounts of force (and / or different z-axis positions) for each clamping arm. Still further, the clamping force profile can be a time-based profile, that is, the force applied by each of the clamping arms and / or the z-axis position or other condition of each of the clamping arms can be controlled, varied over time.

[0063] Figure 9 is a flowchart illustrating a method of detecting a hover indicator of a portion of a semiconductor element on a wire bonder. At step 900, the semiconductor element is clamped against a support structure of the wire bonder. At step 902, a hover indicator of the portion of the semiconductor element relative to the support structure is detected. For example, step 902 can employ the methods described in relation to Figures 5A-5C 、 Figures 6A-6C the methods described in relation to

[0064] Although the present application is primarily illustrated and described with respect to a wire bonder tool 108 that does not have a wire (e.g., a free air ball or a length of wire), the present application is not so limited. For example, aspects of the present application (e.g., detecting a hover indicator or a hover value, as in Figures 7-9 may also be applied to wire looping operations.

[0065] For example, by detecting a hover value during the formation of a conductive bump on a wire bonder (e.g., using a wire bonder tool with or without a portion of wire (e.g., a free air ball)), a desired height of the bump formation operation can be achieved (e.g., bump formation parameters can be varied in view of the hover). Such bump formation operations include a smoothing operation, etc.

[0066] In another example, by detecting a hover value during the formation of a wire loop (e.g., using a wire bonder tool with or without a portion of wire (e.g., a free air ball)), a desired height of the wire loop can be programmed (e.g., loop parameters can be varied in view of the hover).

[0067] The exemplary results provided by the present application overcome the lack of closed loop optimization and detection in today's industry. According to certain exemplary embodiments of the present application, new closed loop optimization methods and real-time monitoring methods related to device clamping conditions are provided.

[0068] Although the present application is illustrated and described herein with reference to specific embodiments, the application is not intended to be limited to the details shown, since various modifications can be made in the details within the scope and range of equivalents of the claims and without departing from the application.

Claims

1. A method of adjusting a clamping of a semiconductor element against a support structure of a wire bonder, the method comprising the steps of: (a) detecting a suspension indicator of the semiconductor element relative to the support structure at a plurality of locations of the semiconductor element; and (b) adjusting the clamping of the semiconductor element against the support structure based on a result of step (a), wherein the suspension indicator of the semiconductor element relative to the support structure is a suspension height measurement, and wherein step (a) comprises (al) pressing a respective portion of the semiconductor element against the support structure with a pressing force applied by a wire bonding tool of the wire bonder, and (a2) releasing at least a portion of the pressing force to detect the suspension height measurement at a respective one of the plurality of locations of the semiconductor element.

2. The method of claim 1, wherein, Steps (a) and (b) are performed as part of a setup of a wire bonding operation.

3. The method of claim 1, wherein, Steps (a) and (b) are repeated at predetermined intervals related to the wire bonding operation.

4. The method of claim 1, wherein, The clamping of the semiconductor element against the support structure is provided by a device holder, and wherein step (b) comprises adjusting the clamping by the device holder.

5. The method of claim 4, wherein, The device holder comprises a plurality of clamping arms, and wherein step (b) comprises adjusting the clamping by the device holder by adjusting at least one of the clamping arms.

6. The method of claim 5, wherein, Adjusting at least one of the clamping arms comprises adjusting at least one of (i) a clamping force provided by at least one of the clamping arms and (ii) a position of at least one of the clamping arms.

7. The method of claim 1, wherein, Step (b) comprises replacing a device holder of the wire bonder.

8. The method of claim 1, wherein, At step (a2), upon detecting the suspension height measurement at the respective one of the plurality of locations of the semiconductor element, a reduced pressing force is applied to the respective portion of the semiconductor element, the reduced pressing force being less than the pressing force.

9. The method of claim 1, wherein, The suspension indicator relates to a distance between (i) the respective portion of the semiconductor element at each of the plurality of locations of the semiconductor element and (ii) the support structure.

10. A method of determining a required clamping force distribution for clamping a semiconductor element on a wire bonder, the method comprising the steps of: (a) clamping the semiconductor element against a support structure of the wire bonder with a plurality of clamping force distributions by a device holder of the wire bonder; (b) detecting a suspension value of a plurality of locations of the semiconductor element under each of the plurality of clamping force distributions; and (c) determining a required clamping force distribution for clamping the semiconductor element on the wire bonder using data obtained from step (b), wherein step (b) comprises (bl) pressing a respective portion of the semiconductor element against the support structure with a pressing force applied by a wire bonding tool of the wire bonder, and (b2) releasing at least a portion of the pressing force to detect the suspension value at a respective one of the plurality of locations of the semiconductor element.

11. The method of claim 10, wherein, The semiconductor element comprises a plurality of semiconductor dies, and the device holder defines a plurality of apertures for accessing the plurality of semiconductor dies during a wire bonding operation. The semiconductor element comprises a plurality of semiconductor dies, and the device holder defines a plurality of apertures for accessing the plurality of semiconductor dies during a wire bonding operation.

12. The method of claim 10, wherein, At step (b2), a reduced pressing force is applied to the respective portion of the semiconductor element while detecting the levitation value at the respective one of the plurality of locations of the semiconductor element, the reduced pressing force being less than the pressing force.

13. The method of claim 10, wherein, Step (a) comprises: (a1) lowering a wire bonding tool of the wire bonder and detecting contact between the respective portion of the semiconductor element and the wire bonding tool; (a2) continuing to lower the wire bonding tool until a pressing of the respective portion of the semiconductor element against the support structure is detected; and (a3) detecting the levitation value at the respective portion of the semiconductor element using position information retrieved during step (a1) and step (a2).

14. The method of claim 10, wherein, The levitation value is related to a distance between (i) the respective portion of the semiconductor element at each of the plurality of locations of the semiconductor element and (ii) the support structure.

15. A method of detecting a levitation indicator of a portion of a semiconductor element on a wire bonder, the method comprising the steps of: (a) clamping the semiconductor element against a support structure of the wire bonder; and (b) detecting a levitation indicator of the portion of the semiconductor element relative to the support structure, wherein the levitation indicator comprises at least one of (i) a levitation condition and (ii) a levitation height determination, and wherein step (b) comprises: (b1) pressing the portion of the semiconductor element against the support structure using a pressing force applied by a wire bonding tool of the wire bonder; and (b2) releasing at least a portion of the pressing force to detect the levitation indicator.

16. The method of claim 15, wherein, At step (b2), a reduced pressing force is applied to the portion of the semiconductor element while detecting the levitation indicator, the reduced pressing force being less than the pressing force.

17. The method of claim 15, wherein, The levitation indicator comprises at least one of (i) a levitation condition and (ii) a levitation height determination, and wherein step (b) comprises: (b1) lowering a wire bonding tool of the wire bonder and detecting contact between the portion of the semiconductor element and the wire bonding tool; (b2) continuing to lower the wire bonding tool while detecting a pressing of the portion of the semiconductor element against the support structure; and (b3) detecting the levitation indicator at the portion of the semiconductor element using position information retrieved during step (b1) and step (b2).

18. The method of claim 15, wherein, Step (b) comprises lowering a wire bonding tool of the wire bonder from a predetermined height of the wire bonding tool above the portion of the semiconductor element, and detecting the levitation indicator using a time elapsed between (i) the wire bonding tool being at the predetermined height and (ii) a contact between the wire bonding tool and the portion of the semiconductor element being declared.

19. The method of claim 18, wherein, The predetermined height is a search height of a wire bonding process on the wire bonder.

20. The method of claim 18, wherein, The levitation indicator is detected using a known velocity profile of the wire bonding tool between the predetermined height and the contact declaration, in combination with the time elapsed.

21. The method of claim 15, wherein, Step (b) comprises lowering a wire bonding tool of the wire bonder towards the portion of the semiconductor element, and detecting the levitation indicator using a force detected in relation to contact between the wire bonding tool and the portion of the semiconductor element.

22. The method of claim 21, wherein, The force is an impact force detected at the time when contact is declared between the wire bonding tool and the portion of the semiconductor element.

23. The method of claim 22, wherein, The impact force is detected using a force sensor in a bonding head assembly of a wire bonder, the bonding head assembly carrying the wire bonding tool.

24. The method of claim 15, wherein, Step (b) is repeated for a plurality of locations of the semiconductor element, such that a plurality of hovering indicators are detected, and the hovering indicators are related to a distance between (i) a portion of the semiconductor element at each of the plurality of locations of the semiconductor element and (ii) the support structure.

25. The method of claim 15, further comprising the step of: A warning indication is provided if a hovering indicator detected in step (b) is outside an acceptable range for that hovering indicator.

26. The method of claim 15, further comprising the step of: At least one bonding parameter of the wire bonding process is automatically adjusted if a hovering indicator detected in step (b) is outside an acceptable range for that hovering indicator.

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