JP2016139687A - Wire bonding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the inclination of one surface of a semiconductor element accurately, while reflecting the wire bonding conditions, when bonding a wire to one surface of a semiconductor element by wedge bonding.SOLUTION: For a semiconductor element 30 on a bonding stage 200, temporary bonding for forming a collapsed portion 41 protruding farther than the diameter D of a wire 40 is performed by mean of a bonding tool 100. Subsequently, inclination angles θ1, θ2 are determined from the relationship of tanθ1=(t1-t2)/L and tanθ2=(t3-t4)/W, where the direction of supersonic vibration if the first direction Y, a direction perpendicular thereto is a second direction X, thicknesses at the opposite ends of a first maximum dimension part 41a of the collapsed portion 41 having a maximum dimension L in the first direction Y are t1, t2, thicknesses at the opposite ends of a second maximum dimension part 41b including the collapsed portion 41 having a maximum dimension W in the second direction X are t3, t4, and the inclination angles of one surface 31 of the semiconductor element 30 in the first direction Y, and second direction X are θ1, θ2.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a wire bonding method for bonding a wire to one surface of a semiconductor element by wedge bonding.

  Conventionally, as a bonding method by this type of wedge bonding, for example, a method described in Patent Document 1 has been proposed. Specifically, a load and ultrasonic vibration are applied to the wire with a bonding tool from above the one surface in a state where the wire is in contact with the one surface of the semiconductor element whose one surface is a bonding surface. Thereby, since a wire is crushed and deform | transformed, a wire is joined to one surface of a semiconductor element.

  Here, the semiconductor element is bonded in a state where it is mounted on the bonding stage. However, when a foreign substance is interposed between the semiconductor element and the stage, one surface of the semiconductor element is likely to be inclined from the horizontal plane. In many cases, the semiconductor element is mounted on the bonding stage in a state of being bonded to the substrate with solder or the like, but one surface of the semiconductor element is more likely to be inclined than the horizontal plane due to non-uniform solder thickness or the like.

  When wedge bonding is performed in a state where one surface of the semiconductor element is tilted in this manner, the crushed portion of the wire that is thinly deformed by the bonding tool is likely to have a highly asymmetric shape, which tends to cause a decrease in bonding reliability.

  Therefore, conventionally, as described in Patent Document 1, for example, the inclination of one surface of a semiconductor element as a bonding surface is detected and obtained by optical means such as imaging using a laser or a camera. The inclination is corrected and wire bonding is performed.

Japanese Patent Laid-Open No. 11-150148

  By the way, as described above, the conventional method for obtaining the tilt of one surface of a semiconductor element is to directly detect the tilt state of the one surface of the semiconductor element by optical means such as laser or camera imaging.

  However, in this case, the inclination of one surface of the semiconductor element is not obtained based on the actual state during wire bonding, that is, the state in which a bonding load or ultrasonic vibration is applied to the wire. Therefore, in order to correct the inclination with high accuracy and realize normal bonding, inclination detection reflecting the wire bonding condition is desired.

  The present invention has been made in view of the above problems, and an object of the present invention is to enable accurate inclination detection reflecting wire bonding conditions when bonding a wire to one surface of a semiconductor element by wedge bonding. To do.

  In order to achieve the above object, according to the first aspect of the present invention, in the state where the wire (40) is brought into contact with the one surface of the semiconductor element (30) having the one surface (31) as the bonding surface, A wire bonding method by wedge bonding in which a wire is deformed so as to be crushed by applying a load and ultrasonic vibration to the wire with a bonding tool (100) from above, and has the following features. .

  That is, the wire bonding method according to claim 1 is obtained by a mounting step of mounting the semiconductor element on the bonding stage (200), an inclination determination step of determining an inclination of one surface of the semiconductor element from the horizontal plane, and an inclination determination step. An inclination correction process for correcting the inclination of one surface of the semiconductor element, and a bonding process for bonding wires by wedge bonding thereafter.

  Furthermore, in the inclination determination step, the following first step and second step are performed. In the first step, a wire is brought into contact with one surface of a semiconductor element by a bonding tool, and a load and ultrasonic vibration are applied to the wire to deform the wire so that the wire is crushed. This is a process as temporary bonding for forming the crushed portion (41), which is the portion that has been cut.

  In the second step, in the horizontal plane, the direction of ultrasonic vibration is the first direction Y, the direction orthogonal to the first direction Y is the second direction X, and the maximum dimension along the first direction Y of the collapsed portion. The portion having L is defined as the first maximum dimension portion (41a), the portion including the collapsed portion and having the maximum dimension W along the second direction X is defined as the second maximum dimension portion (41b). The thicknesses at both ends in one direction Y are t1 and t2, the thicknesses of the crushed portions at both ends in the second direction X of the second maximum dimension portion are t3 and t4, and the inclination angle of one surface of the semiconductor element in the first direction Y is Assuming that the inclination angle of one surface of the semiconductor element in θ1 and the second direction X is θ2, from the relationship of tan θ1 = (t1−t2) / L and tanθ2 = (t3−t4) / W, the inclination angle θ1, This is a step of obtaining θ2.

  In the tilt correction step, the bonding stage is adjusted based on the tilt angles θ1 and θ2 obtained in the second step, and the tilt of one surface of the semiconductor element is corrected so that the one surface of the semiconductor element is parallel to the horizontal plane. . The wire bonding method of claim 1 is characterized by these points.

  According to this, since the presence / absence of the inclination of one surface of the semiconductor element can be determined based on the state of the collapsed portion of the wire formed by temporary bonding, it is possible to detect the inclination with high accuracy reflecting the wire bonding conditions.

  In addition, the code | symbol in the bracket | parenthesis of each means described in the claim and this column is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

It is a schematic side view which shows the principal part of the semiconductor device concerning embodiment of this invention. It is a schematic sectional drawing in alignment with the dashed-dotted line AA in FIG. It is a schematic top view which shows the planar structure of the wire in FIG. It is process drawing which shows the bonding process by wedge bonding in the wire bonding method concerning the said embodiment, (a) is a schematic side view, (b) is a schematic sectional drawing along the dashed-dotted line BB in (a). is there. 5A and 5B are process diagrams illustrating a bonding process subsequent to FIG. 4, in which FIG. 5A is a schematic side view, and FIG. 5B is a schematic cross-sectional view taken along one-dot chain line CC in FIG. It is a schematic sectional drawing which shows an example of the cause of generation | occurrence | production of the one surface of the semiconductor element on a bonding stage, (a) shows a 1st example and (b) shows a 2nd example. It is process drawing which shows the inclination determination process in the 1st direction Y of the wire bonding method concerning the said embodiment, (a) is a schematic side view, (b) is a schematic top view in (a). It is process drawing which shows the inclination determination process in the 2nd direction X of the wire bonding method concerning the said embodiment, (a) is a schematic sectional drawing, (b) is a schematic top view in (a). It is process drawing which shows the inclination correction process of the wire bonding method concerning the said embodiment, (a) shows a 1st example, (b) shows a 2nd example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, parts that are the same or equivalent to each other are given the same reference numerals in the drawings for the sake of simplicity. In each of the following drawings, a horizontal plane as a virtual plane is indicated by a broken line as necessary.

  First, a semiconductor device as a wire bonding structure according to an embodiment of the present invention will be described with reference to FIGS. This semiconductor device is mounted on a vehicle such as an automobile and is applied as a device for driving various electronic devices for the vehicle.

  The semiconductor device of the present embodiment is roughly configured to include a substrate 10, a semiconductor element 30 bonded to the substrate 10 via a bonding member 20, and a wire 40 connected to the semiconductor element 30. Yes.

  The substrate 10 is, for example, a printed circuit board, a wiring substrate such as a ceramic substrate, or a lead frame, and supports the semiconductor element 30. The semiconductor element 30 is an IC chip or a transistor element made of a silicon semiconductor or the like, and is formed by a semiconductor process.

  Here, the semiconductor element 30 is chip-shaped, and one surface 31 which is one of the front and back plate surfaces is used as a bonding surface. That is, the semiconductor element 30 is bonded and fixed to the substrate 10 via the bonding member 20 with the plate surface opposite to the one surface 31 facing the substrate 10. As this joining member 20, die bond materials, such as solder, a conductive adhesive, or an insulating adhesive agent, are mentioned, for example.

  The wire 40 is made of Au (gold), Al (aluminum), Cu (copper), or the like, and is bonded to the one surface 31 of the semiconductor element 30. Specifically, the bonding portion of the wire 40 in the one surface 31 of the semiconductor element 30 is configured as a bonding pad made of aluminum or the like (not shown), and the wire 40 is connected to the pad.

  Note that the number of the wires 40 bonded to the one surface 31 of the semiconductor element 30 may be one, but typically, there are a plurality of wires. The bonding portion between the wire 40 and the semiconductor element 30 may be bonded by primary bonding in wire bonding or may be bonded by secondary bonding.

  The wire 40 is bonded by wedge bonding, which will be described later, and is applied with a load and ultrasonic vibration from above the one surface 31 of the semiconductor element 30 by the bonding tool 100 (see FIGS. 4 and 5). It is joined by being crushed and deformed.

  Here, as shown in FIGS. 1 to 3, a crushing portion 41 is formed on the wire 40 by applying a load of the bonding tool 100 and applying ultrasonic vibration. The crushing portion 41 is a portion that is thinly deformed beyond the diameter D of the wire 40 (see FIG. 3) with respect to the original shape of the wire 40, and is formed on both sides of the axis of the wire 40 (longitudinal axis). ing.

  The wire 40 is bonded to the one surface 31 of the semiconductor element 30 at the crushing portion 41. 1 to 3 show a first direction Y that is a direction of ultrasonic vibration during wire bonding in a horizontal plane and a second direction X that is a direction orthogonal to the first direction Y. . Here, the first direction Y is substantially parallel to the axial direction of the wire 40, and the second direction X is substantially parallel to the radial direction of the wire 40.

  In the example shown in FIGS. 1 and 2, the one surface 31 of the semiconductor element 30 is inclined from the horizontal plane in each direction Y and X due to the non-uniform thickness of the bonding member 20. However, as will be described later, at the time of wire bonding, the one surface 31 of the semiconductor element 30 and the horizontal surface are aligned in parallel.

  Next, the manufacturing method of the semiconductor device of the present embodiment will be described focusing on the wire bonding method with reference to FIGS. First, the semiconductor element 30 is mounted on the substrate 10 via the bonding member 20 and bonded. Then, wire bonding is performed on the one surface 31 of the semiconductor element 30 to connect the wires 40.

  This wire bonding is performed in accordance with typical wedge bonding, and an outline of this wedge bonding will be described. First, the semiconductor element 30 is mounted on the bonding stage 200 (see FIG. 6) (mounting process). Here, the substrate 10 having the semiconductor element 30 fixed thereto is mounted on the bonding stage 200.

  Then, as shown in FIGS. 4 and 5, a bonding step is performed in which the wire 40 is bonded to the one surface 31 of the semiconductor element 30 by a wedge bonding method. This bonding process is common to both 1st bonding (primary bonding) and 2nd bonding (secondary bonding).

  In these steps, as shown in FIGS. 4 and 5, a bonding tool 100 for pressing the wire 40, a wire guide (not shown) for moving the wire 40, and a wire cutter (not shown) for cutting the wire 40 are provided. A bonding device is used. The bonding tool 100, the wire guide, and the wire cutter can be moved to desired positions by an actuator (not shown).

  In the wedge bonding of this embodiment, first, the wire 40 is routed to the one surface 31 of the semiconductor element 30 that is a bonding portion, and bonding is performed there. Then, after this bonding, wire cutting is performed as necessary.

  As shown in FIGS. 4 and 5, the bonding tool 100 has a groove 102 having a width corresponding to the diameter D of the wire 40 on the wire pressing surface 101 for pressing the wire 40. Here, the groove 102 has a semicircular cross section, and is provided so as to extend over the entire area from one end of the wire pressing surface 101 to the other end opposite thereto.

  The bonding tool 100 is configured to perform wedge bonding in which the wire 40 is pressed against the one surface 31 of the semiconductor element 30 while applying the ultrasonic vibration and load while the wire 40 is supported by the groove 102.

  Here, as shown in FIG. 4, in the bonding process of this embodiment, the bonding tool 100 is used to cause a part of the wire 40 to enter the groove 102. Then, as shown in FIG. 5, ultrasonic vibration and a load are applied to deform the wire 40 so as to be crushed.

  As a result, as shown in FIG. 5, the wire 40 is formed with a deformed portion that protrudes beyond the diameter D of the wire 40, that is, a collapsed portion 41. Thus, the bonded wire 40 as a product is formed, and the wire bonding is completed.

  Here, when the inclination of the one surface 31 of the semiconductor element 30 that is the bonding surface from the horizontal plane is generated, the application of load and vibration is not uniform in the entire crushed portion 41, so that the planar shape and thickness of the crushed portion 41 are not uniform. The shape of the wire has a large asymmetry with respect to the axis of the wire 40. An example of the cause of this inclination is shown in FIG.

  As shown in the first example of FIG. 6A, the inclination is caused by the thickness variation of the bonding member 20 between the substrate 10 and the semiconductor element 30, or in the second example of FIG. 6B. As shown, it is generated by a foreign substance K1 or the like interposed between the substrate 10 and the bonding stage 200. Here, the foreign material K1 is, for example, dust or debris. Further, the asymmetry of the shape of the collapsed portion 41 is not preferable because it leads to a decrease in bonding strength and the like.

  Therefore, in the wire bonding method of the present embodiment, the inclination of the one surface 31 of the semiconductor element 30 on the bonding stage 200 is further obtained between the mounting process and the wire bonding process that is the actual bonding, and this inclination is corrected. I did it.

  In this case, paying attention to the fact that the inclination is a cause of the asymmetric shape of the crushed portion 41, provisional bonding is performed based on the actual bonding operation in the bonding tool 100, and the shape of the crushed portion 41 at that time The inclination was calculated.

  Specifically, an inclination determination step for obtaining the inclination of the one surface 31 of the semiconductor element 30 from the horizontal plane and an inclination correction step for correcting the inclination of the one surface 31 of the semiconductor element 30 obtained in the inclination determination step are performed. Thereafter, as shown in FIGS. 4 and 5, a bonding process is performed as the actual bonding for bonding the wires by wedge bonding.

  In the inclination determination step, first, as shown in FIGS. 7 and 8, a first step as temporary bonding is performed. In this first step, provisional bonding is performed by the same operation as that of the bonding tool 100 shown in FIGS.

  Specifically, in the first step, the wire 40 is brought into contact with the one surface 31 of the semiconductor element 30 by the bonding tool 100, and a load and ultrasonic vibration are applied to the wire 40 to deform the wire 40. Let Thereby, in the first step, a crushed portion 41 that is a portion protruding beyond the diameter D of the wire 40 and deformed is formed, and the wire 40 is temporarily bonded.

  However, due to the cause shown in FIG. 6 and the like, when the one surface 31 of the semiconductor element 30 is tilted during this temporary bonding, as shown in FIGS. The shape of the asymmetry is large on both sides of the axis of the wire 40.

  As shown in FIG. 7 and FIG. 8, both the first direction Y, which is the direction of ultrasonic vibration in the horizontal plane, and the second direction X, which is the direction orthogonal to the first direction Y, become lower due to the inclination. The crushing portion 41 is thicker and the extent of expansion is smaller. That is, the direction of inclination and the tendency of asymmetry of the collapsed portion 41 have a correlation.

  Here, as shown in FIG. 7, a portion having a maximum dimension L along the first direction Y in the collapsed portion 41 is defined as a first maximum dimension portion 41 a. On the other hand, as shown in FIG. 8, a portion of the wire 40 that includes the crushed portion 41 and has the maximum dimension W along the second direction X is defined as a second maximum dimension portion 41b. In other words, the second maximum dimension portion 41 b is configured by the crushed portions 41 on both sides of the axis of the wire 40 and a region having a width of the diameter D of the wire 40 interposed between both the crushed portions 41.

  Moreover, as FIG. 7 shows, one is set to t1 among the thickness of the both ends in the 1st direction Y of the 1st largest dimension part 41a, and the other is set to t2. Also, as shown in FIG. 8, one of the thicknesses of the crushed portions 41 at both ends in the second direction X of the second maximum dimension portion 41b is t3, and the other is t4.

  As shown in FIG. 7, the inclination angle of the one surface 31 of the semiconductor element 30 in the first direction Y is θ1, and as shown in FIG. 8, the one surface 31 of the semiconductor element 30 in the second direction X The inclination angle is θ2. 7 and 8, the relationship of tan θ1 = (t1−t2) / L and the relationship of tan θ2 = (t3−t4) / W are established.

  Therefore, in the tilt determination step, as the second step, each dimension t1, t2, t3, t4, L, L, of the collapsed portion 41 obtained in the first step is performed using an optical means such as a laser or a camera. Find W. In the second step, calculation by a personal computer or the like is performed. From the relationship of tan θ1 = (t1−t2) / L and tanθ2 = (t3−t4) / W, the inclination angle θ1 in the first direction Y, And the inclination angle θ2 in the second direction X is obtained.

  In addition, although the crushing part 41 is formed in the both sides of the axis | shaft of the wire 40, what is necessary is just to make any one crushing part 41 into the 1st largest dimension part 41a. Or both the crushing parts 41 are good also as the 1st largest dimension part 41a, In this case, each dimension t1, t2, and L should just take the average value of both, for example.

  Thus, after finishing the inclination determination process, in this embodiment, as shown in FIG. 9, an inclination correction process is performed. In this inclination correction process, the bonding stage 200 is adjusted based on the inclination angles θ1 and θ2 obtained in the second process, and the one surface 31 of the semiconductor element 30 is parallel to the horizontal plane. Correct the tilt.

  This inclination correction can be easily performed, for example, by adjusting the inclination of the bonding stage 200 with an electric actuator or the like. In FIG. 9, the tilt of the bonding stage 200 is adjusted using a rod 300 that moves up and down electrically. In this case, since the inclination angles θ1 and θ2 are known, the adjustment can be performed with high accuracy.

  In this way, after the one surface 31 of the semiconductor element 30 is made parallel to the horizontal plane in the tilt correcting process, the actual wire bonding by the wedge bonding, that is, the bonding process shown in FIGS.

  In this wire bonding step, the wire 40 may be bonded to the one surface 31 of the same semiconductor element 30, that is, actual bonding, while the temporarily bonded wire 40 remains. In addition, after the temporarily bonded wire 40 is pulled using a jig or the like to peel from the one surface 31 of the semiconductor element 30, the actual wire 40 may be joined to the temporary bonding portion again.

  The above is the wire bonding method of the present embodiment, and the semiconductor device of the present embodiment is thereby completed. When one of the inclination angles θ1 and θ2 in the directions Y and X described above is 0 in the inclination determination step, only the direction in which the inclination occurs may be corrected in the inclination correction step. When both the inclination angles θ1 and θ2 are both 0, the inclination correction process is omitted and the actual bonding process may be performed.

  By the way, according to the present embodiment, the temporary bonding is performed by an actual bonding operation, and the presence or absence of the inclination of the one surface 31 of the semiconductor element 30 is based on the state of the crushed portion 41 of the wire 40 by the temporary bonding. Judgment is made. Therefore, the inclination of the one surface 31 of the semiconductor element 30 can be accurately detected by reflecting the wire bonding conditions.

  Here, the load and the power of the ultrasonic vibration in the first step of the tilt determination step that is temporary bonding may be equivalent to those in the bonding step that is actual wire bonding.

  However, since the first process is merely temporary bonding, the load in the first process is smaller than the load in the bonding process, and the ultrasonic vibration power in the first process is the ultrasonic wave in the bonding process. The power may be smaller than the vibration power.

  If a load and ultrasonic vibration are applied from the bonding tool 100 to the semiconductor element 30 in a state where the one surface 31 of the semiconductor element 30 is inclined in the first step, the semiconductor element 30 may be damaged. However, it is easy to avoid such a concern by making the load by the bonding tool 100 and the power of ultrasonic vibration in the first step smaller than those of the actual bonding.

(Other embodiments)
As the semiconductor device, it is sufficient that the wire 40 is wedge-bonded to the one surface 31 of the semiconductor element 30. If possible, the semiconductor device may be configured such that the substrate 10 is omitted. Moreover, as a semiconductor device, the structure by which the semiconductor element 30 and the wire 40 were sealed with mold resin as needed may be sufficient.

  Further, the groove 102 of the bonding tool 100 may have a V-shaped cross section other than the above-described semicircular groove.

  Further, the present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope described in the claims. The above embodiments are not irrelevant to each other, and can be combined as appropriate unless the combination is clearly impossible, and the above embodiments are not limited to the illustrated examples. Absent. In each of the above-described embodiments, it is needless to say that elements constituting the embodiment are not necessarily essential unless explicitly stated as essential and clearly considered essential in principle. Yes. Further, in each of the above embodiments, when numerical values such as the number, numerical value, quantity, range, etc. of the constituent elements of the embodiment are mentioned, it is clearly limited to a specific number when clearly indicated as essential and in principle. The number is not limited to the specific number except for the case. Further, in each of the above embodiments, when referring to the shape, positional relationship, etc. of the component, etc., the shape, unless otherwise specified and in principle limited to a specific shape, positional relationship, etc. It is not limited to the positional relationship or the like.

DESCRIPTION OF SYMBOLS 30 Semiconductor element 31 One surface of a semiconductor element 40 Wire 41 Crushing part 41a wire 1st largest dimension part 41b 2nd largest dimension part 100 Bonding tool 200 Bonding stage

Claims (2)

In a state where the wire (40) is in contact with the one surface of the semiconductor element (30) having the one surface (31) as the bonding surface, the bonding tool (100) is used to apply a load and a load to the wire from above the one surface. A wire bonding method by wedge bonding in which the wire is deformed so as to be crushed by applying sonic vibration,
A mounting step of mounting the semiconductor element on the bonding stage (200);
An inclination determination step for obtaining an inclination from one horizontal surface of the semiconductor element;
An inclination correction step of correcting the inclination of one surface of the semiconductor element obtained in the inclination determination step;
Thereafter, a bonding step of bonding the wire by wedge bonding,
In the inclination determining step, the wire is brought into contact with one surface of the semiconductor element by the bonding tool, and a load and ultrasonic vibration are applied to the wire to deform the wire so that the wire is crushed. A first step as a temporary bonding to form a crushed portion (41) that is a part that protrudes and deforms more than
The direction of the ultrasonic vibration in the horizontal plane is a first direction Y, and a direction orthogonal to the first direction Y is a second direction X,
A portion having the maximum dimension L along the first direction Y in the collapsed portion is a first maximum dimension portion (41a), and a portion having the maximum dimension W along the second direction X is included including the collapsed portion. The second maximum dimension part (41b),
The thicknesses of both ends in the first direction Y of the first maximum dimension portion are t1 and t2, the thicknesses of the crushing portions at both ends in the second direction X of the second maximum dimension portion are t3 and t4, When the inclination angle of one surface of the semiconductor element in the direction Y of 1 is θ1, and the inclination angle of one surface of the semiconductor element in the second direction X is θ2,
a second step of obtaining the tilt angles θ1 and θ2 from the relationship of tan θ1 = (t1−t2) / L and tan θ2 = (t3−t4) / W,
In the tilt correction step, the bonding stage is adjusted based on the tilt angles θ1 and θ2 obtained in the second step, so that one surface of the semiconductor element is parallel to a horizontal plane. A wire bonding method characterized by correcting inclination.   The load in the first step is a load smaller than the load in the bonding step, and the power of the ultrasonic vibration in the first step is smaller than the power of the ultrasonic vibration in the bonding step. The wire bonding method according to claim 1, wherein the wire bonding method is provided.

Images