Patent Application
20160358883
The present invention relates to a bump forming method, a bump forming apparatus, and a semiconductor device manufacturing method.
As a bump forming method of semiconductor devices, there is known a bump forming method to which a wire bonding method is applied. For example, a method has been known in which a pressure-bonding ball formed at the leading end of a wire is bonded onto an electrode on a semiconductor die and, on this pressure-bonding ball, a neck portion of the wire having a certain height is formed to form a bump (see Patent Document 1). Such a bump may be called a stud bump (registered trademark).
Patent Document 1: Japanese Patent No. 4509043
However, in the invention described in Patent Document 1, when the bump gets above a certain height, it may be difficult for the neck portion of the wire to stand upright and it may also be difficult to cut the wire by operating the bonding tool. As another related art, there has also been known a method of forming a stacked bump by stacking multiple bumps, but the method suffers from a problem in that even stacking bumps is cumbersome and time-consuming or bumps may be misaligned and a desired bump strength may not be provided.
Incidentally, three dimensional packaging configurations such as TSV (Through Silicon Via) and POP (Package On Package) are currently becoming mainstream. In such packaging configurations, it is required to form bumps having above a certain height at a pitch distance narrowed to some extent and there is an increasing need to form such bumps more easily and efficiently.
It is hence that the present invention provides a bump forming method, a bump forming apparatus, and a semiconductor device manufacturing method with which the above described problem can be solved.
An aspect of the present invention is directed to a bump forming method of semiconductor devices using a bonding tool with a wire inserted therethrough, the method including: a bonding step of lowering the bonding tool toward a first point on a reference plane and bonding the leading end of the wire extending out of the tip of the bonding tool to the first point; a wire pay-out step of moving the bonding tool in a direction away from the first point while paying out the wire from the tip of the bonding tool; a thin portion forming step of pressing a portion of the wire at a second point on the reference plane using the bonding tool to form a thin portion in the wire; a wire shaping step of moving the bonding tool along with the thin portion of the wire and shaping the wire bonded to the first point in a manner rising from the reference plane; and a bump forming step of cutting the wire at the thin portion to form a bump having a shape rising from the reference plane at the first point.
In accordance with the arrangement above, the wire is formed with a thin portion using the bonding tool and the wire bonded to the first point is shaped in a manner rising from the reference plane, and then the wire is cut at the thin portion, so that a bump is formed having a shape rising from the reference plane at the first point. It is therefore possible to form a bump having a desired height more easily and efficiently.
In the bump forming method, in the wire pay-out step, the bonding tool is moved to a predetermined height in a direction perpendicular to the reference plane, moved toward the second point in the parallel direction while being kept at the predetermined height, and moved toward the second point in the direction perpendicular to the reference plane.
In the bump forming method, in the wire pay-out step, the bonding tool is moved to a predetermined height in a direction perpendicular to the reference plane and moved toward the second point in a predetermined curve.
In the bump forming method, in the wire pay-out step, the bonding tool is moved toward above the second point to a predetermined height in a predetermined curve and moved toward the second point in a direction perpendicular to the reference plane.
In the bump forming method, in the wire shaping step, the bonding tool is moved toward above a third point on the reference plane, the third point configured on the line connecting the second point and the first point with the first point being arranged between the third point and the second point.
In the bump forming method, in the wire shaping step, the bonding tool is moved to a predetermined height in a direction perpendicular to the reference plane and moved toward the third point in the parallel direction while being kept at the predetermined height.
In the bump forming method, in the wire shaping step, the bonding tool is moved toward above the third point to a predetermined height in a predetermined curve.
The bump forming method can further include, after the wire shaping step and before the wire cutting step, a step of raising the bonding tool while paying out the wire from the tip of the bonding tool.
In the bump forming method, in the bump forming step, the bonding tool is raised further, with the wire being restrained by a wire clamper, to cut the wire at the thin portion.
The bump forming method can further include, before the bonding step, a step of forming the leading end of the wire into a ball.
In the bump forming method, in the thin portion forming step, the wire is pressed such that the thin portion of the wire has a thickness approximately half the diameter of the wire.
A semiconductor device manufacturing method according to an aspect of the present invention includes the bump forming method.
An aspect of the present invention is directed to a bump forming apparatus for forming a bump of semiconductor devices using a bonding tool with a wire inserted therethrough, the apparatus including a control unit for controlling the operation of the bonding tool, in which the control unit is configured to perform: a bonding step of lowering the bonding tool toward a first point on a reference plane and bonding the leading end of the wire extending out of the tip of the bonding tool to the first point; a wire pay-out step of moving the bonding tool in a direction away from the first point while paying out the wire from the tip of the bonding tool; a thin portion forming step of pressing a portion of the wire at a second point on the reference plane using the bonding tool to form a thin portion in the wire; a wire shaping step of moving the bonding tool along with the thin portion of the wire and shaping the wire bonded to the first point in a manner rising from the reference plane; and a bump forming step of cutting the wire at the thin portion to form a bump having a shape rising from the reference plane at the first point.
In accordance with the arrangement above, the wire is formed with a thin portion using the bonding tool and the wire bonded to the first point is shaped in a manner rising from the reference plane, and then the wire is cut at the thin portion, so that a bump is formed having a shape rising from the reference plane at the first point. It is therefore possible to form a bump having a desired height more easily and efficiently.
In accordance with the present invention, it is possible to form a bump having a desired height more easily and efficiently.
An embodiment of the present invention will hereinafter be described. In the following description of the drawings, identical or similar components are designated by the same or similar reference symbols. The drawings are illustrative only and the dimensions and geometries of various parts are schematic only, and the technical scope of the present invention should not be understood as being limited to the embodiment.
As shown in
In the following embodiment, a plane parallel to a semiconductor device (e.g. semiconductor die) or a lead frame serving as a bonding target is defined as XY plane and the direction perpendicular to the XY plane is defined as Z direction. The tip position of the capillary 15 is identified with a spatial coordinate (X, Y, Z) represented by an X coordinate, a Y coordinate, and a Z coordinate.
The base 11 has the XY table 12 placed slidably thereon. The XY table 12 is a moving device that is able to move the capillary 15 to a predetermined position on the XY plane based on a drive signal from the control unit 10.
The bonding head 13 is a moving device that is formed integrally with a bonding arm (not shown) and holds the ultrasonic horn 16 movably in the Z direction based on a drive signal from the control unit 10. The bonding head 13 has a lightweight low center-of-gravity structure and can suppress movement of the capillary 15 due to an inertia force generated with the movement of the XY table 12.
The ultrasonic horn 16 is a rod-shaped member including a base end portion, a flange portion, a horn portion, and a leading end portion from the base to the leading end thereof The base end portion is provided with an ultrasonic vibrator 161 arranged to vibrate in response to a drive signal from the control unit 10. The flange portion is attached via the bonding arm to the bonding head 13 in a resonance manner at a position that serves as a node of ultrasonic vibration. The horn portion is an arm extending longer than the diameter of the base end portion, having a structure for amplifying and transmitting the amplitude of vibration by the ultrasonic vibrator 161 to the leading end portion. The end portion is a mounting portion for replaceably holding the capillary 15. The ultrasonic horn 16 has, as a whole, a resonance structure that resonates with vibration by the ultrasonic vibrator 161, in which the ultrasonic vibrator 161 and the flange are positioned at nodes of resonance vibration, while the capillary 15 is positioned at an anti-node of vibration. With these arrangements, the ultrasonic horn 16 serves as a transducer for converting an electrical drive signal into a mechanical vibration.
The capillary 15 is a part of a bonding tool used for bonding. An insertion hole is provided in the capillary 15, through which a wire “w” for bonding is inserted and can be paid out. The capillary 15 is attached replaceably to the ultrasonic horn 16 with a spring force or the like.
The wire damper 17 includes a piezoelectric element arranged to open and close based on a control signal from the control unit 10, whereby the wire “w” can be held and released at predetermined timing.
The wire tensioner 18 can insert the wire “w” therethrough and freely change a tensile force for the wire “w” based on a control signal from the control unit 10 to apply a moderate tensile force to the wire “w” during bonding.
The rotary spool 19 replaceably holds a reel with the wire wound therearound and is arranged to pay out the wire “w” according to the tensile force applied through the wire tensioner 18. It is noted that the material of the wire “w” is selected for good workability and low electrical resistance. For example, gold (Au), silver (Ag), aluminum (Al), or copper (Cu) is commonly used.
The torch electrode 14 is connected to a high-voltage power source not shown through a discharge stabilization resistor not shown and is arranged to generate spark (discharge) based on a control signal from the control unit 10 and, with the heat of the spark, form a free-air ball fab at the leading end of the wire “w” paid out from the tip of the capillary 15. The position of the torch electrode 14 is fixed and, upon discharging, the capillary 15 comes close to the torch electrode 14 until a predetermined distance to generate moderate spark between the leading end of the wire “w” and the torch electrode 14.
The bonding stage 20 is a stage with a working surface to place a work 30 (e.g. substrate or semiconductor die) to be formed with bumps thereon. The heater 21 is provided under the working surface of the bonding stage 20, with which the work 30 can be heated to a temperature suitable for bonding.
The operation unit 40 includes input means such as a trackball, a mouse, a joystick, and a touch panel that serve as an input device for outputting operations by an operator to the control unit 10. The camera 42 is arranged to take an image of the work 30 placed on the working surface of the bonding stage 20. The display 41 is arranged to display an image taken by the camera 42 at a predetermined magnification visible to the operator. The operator operates the operation unit 40 and sets the trajectory of the capillary 15 while observing the work 30 displayed on the display 41.
The control unit 10 is arranged to output various control signals for controlling the bump forming apparatus 1 based on a predetermined software program. Specifically, the control unit 10 performs the following control as a non-limiting example.
(1) Identify the spatial position (X, Y, Z) of the tip of the capillary 15 based on a detection signal from a positional detection sensor not shown and output to the XY table 12 and the bonding head 13 a drive signal for moving the capillary 15 to a spatial position defined by the program.
(2) Output to the ultrasonic vibrator 161 of the ultrasonic horn 16 a control signal for generating ultrasonic vibration during bonding to a bonding point.
(3) Output a control signal for controlling the opening and closing operation of the wire damper 17 such that the wire “w” is paid out as defined by the program. Specifically, set the wire clamper 17 to a releasing state to pay out the wire “w”, while set the wire clamper 17 to a restraining state to form a bent point in the wire “w” or to cut the wire “w”.
(4) Output a control signal for discharging at the torch electrode 14 when forming a free-air ball fab at the leading end of the wire “w”. (5) Output an image from the camera 42 on the display 41. (6) Identify the spatial coordinate of a bonding point, a bent point, etc. based on operations on the operation unit 40.
It is noted that the configuration of the bump forming apparatus 1 is illustrative only and should not be limited thereto. For example, the bonding stage 20 or both the bump forming apparatus 1 and the bonding stage 20 each is provided with a moving device for movement in the X, Y, or Z direction.
Next will be described a bump forming method according to this embodiment.
First will be described a basic operation of the bump forming apparatus 1.
What should be done first is to set a trajectory of the tip 15a of the capillary 15 (see
The operator operates the operation unit 40 while observing images taken by the camera 42 on the display 41 to sequentially set trajectory change points. Specifically, inputting coordinate information through the operation unit 40 and/or positioning and inputting at a desired point a marker displayed on the display 41 causes the X coordinate and the Y coordinate of the point to be set. Numerically inputting the Z-directional displacement of the work 30 from a reference plane (e.g. a surface of the work 30) through the operation unit 40 causes the Z coordinate to be set.
After setting the spatial coordinates of change points for all bumps to be formed, the bonding operation is started. The control unit 10 moves the capillary 15 relatively with respect to the reference plane of the work in the order of the set change points so as to move the capillary 15 along the set trajectory, while repeating release and holding by the wire clamper 17, to perform the bonding operation.
An example of the bump forming method according to this embodiment will hereinafter be described with reference to
First, as shown in
Next, as shown in
During bonding at the first point X1, the control unit 10 supplies a control signal to the ultrasonic horn 16 to cause the ultrasonic vibrator 161 to generate ultrasonic vibration and, through the ultrasonic horn 16 and the capillary 15, apply the ultrasonic vibration to the free-air ball fab. Further, since the electrode 52 on the substrate 50 is applied with a predetermined amount of heat by the heater 21, the mutual effect of the load applied on the free-air ball fab, the ultrasonic vibration, and the heat applied by the heater 21 causes the free-air ball fab to be bonded to the electrode 52. A deformed ball portion 62 of the wire is thus formed.
It is noted that as shown in
Next, as shown in
Subsequently, as shown in
As shown in
The pressing force of the capillary 15 against the wire “w” at the second point X2 can be smaller than the pressing force of the capillary 15 against the wire “w” at the first point X1. The pressing force at the second point X2 can also be smaller than the pressing force of the second bonding during common wire bonding. It is noted that during pressing at the second point X2, ultrasound and/or scrubbing operations can also be applied, as needed.
At the second point X2, a thin portion 64 of the wire “w” is thus formed. The thin portion 64 is provided at a position slightly off the central axis of the insertion hole of the capillary 15 toward the first point X1. For example, the thin portion 64 is a tool impression by the tip 15a of the capillary 15. The thin portion 64 of the wire “w” is configured to have a thickness smaller than the diameter of the wire “w”. The thickness of the thin portion 64 can be, for example, roughly 50% of the diameter of the wire “w”. It is noted that at time t4, the wire “w” has not yet been cut at the thin portion 64, but in a state extending integrally from the deformed ball portion 62 into the insertion hole of the capillary 15.
Next, as shown in
As shown in
Next, as indicated by the trajectory from time t6 to t7 in
A bump 60 having a shape (predetermined height) rising from the reference plane can thus be formed on the electrode 52 of the substrate 50. In the case of forming multiple bumps on the substrate 50, the above described steps are repeated for each electrode.
As shown in
As described heretofore, in accordance with the bump forming method according to this embodiment, the wire “w” is formed with the thin portion 64 using the bonding tool (capillary 15) and the wire bonded to the first point X1 is shaped in a manner rising from the reference plane, and then the wire “w” is cut at the thin portion 64, so that a bump is formed having a shape rising from the reference plane at the first point X1. It is therefore possible to form a bump 60 having a desired height more easily and efficiently.
The above described bump forming method is used to manufacture a semiconductor device. The semiconductor device includes a bump 60 formed through the above described steps. The bump 60 is particularly suitable for applications that require getting above a certain height at a pitch distance narrowed to some extent.
As shown in
The present invention is not limited to the above described embodiment, but is applied in various variations.
The trajectory of movement of the bonding tool (capillary 15) is not limited to the aspect indicated by the arrows in
Herein,
For example, as shown in
Alternatively, as shown in
Alternatively, as shown in
Alternatively, as shown in
Although the above embodiment has described the case where a ball fab is first formed at the leading end of the wire “w” as shown in
Although the above embodiment has described the case where the capillary 15 is moved to the third point X3, which is positioned opposite to the second point X2 with respect to the first point X1, such that the wire “w” is shaped, the aspect of movement of the capillary is not limited thereto as long as the wire “w” can be shaped in a rise-up manner at the first point X1. For example, the capillary 15 is moved from the second point X2 to the first point X1 with its Y coordinate being fixed. In this case, the Y coordinate is changed also. In the bump forming method according to this embodiment, the aspect of movement of the capillary 15 to form a bump having a rise-up shape at the first point X1 can vary in different ways depending on the material of the wire, the pressing force on the wire, the load applied on the wire according to the trajectory of the capillary 15, etc.
The examples and applications described through the above described embodiment of the invention can be combined appropriately depending on the intended use or can be changed or modified for use, and the present invention is not limited to the description of the above embodiment. It is obvious from the description of the appended claims that such combined, changed, or modified modes could also be included within the technical scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-030413 | Feb 2014 | JP | national |
This application is a Continuation of PCT International Application No. PCT/JP2014/061608, filed on Apr. 24, 2014, which claims priority under 35 U.S.C §119(a) to Patent Application No. 2014-030413, filed in Japan on Feb. 20, 2014, all of that are hereby expressly incorporated by reference into the present application.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2014/061608 | Apr 2014 | US |
| Child | 15241086 | US |
