JP3156676B2 - Wire bonding apparatus and wire bonding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a wire bonding apparatus and a wire bonding method.

[0002]

2. Description of the Related Art A conventional wire bonding apparatus will be described with reference to FIGS. FIG. 7 is a perspective view for explaining the configuration of a conventional wire bonding apparatus, and FIGS. 8 and 9 are views for explaining problems when bonding is performed using a conventional wire bonding apparatus. FIG. 10 is a flowchart showing a conventional bonding procedure.

A conventional wire bonding apparatus is shown in FIG.
As shown in FIG. 1, a plurality of pads 2 mainly formed of a material such as aluminum and leads 3 formed on a surface of a semiconductor chip 1 using a thin metal wire 5 having a diameter of 20 to 30 μm made of a material such as gold or aluminum. In this case, wiring is performed between metal terminals.

[0004] Fine metal wires 5 in wire bonding
The mechanism of the connection between the pad 2 and the pad 2 is to press down a thin metal wire 5 drawn out from a tool 4 attached to the tip of a bond arm 6 that can move up and down on the surface of the pad 2 and further apply heat energy and the like by a heater 9. Thus, the oxide film formed on the surface of the pad 2 is eliminated, and the metal wires 5 and the respective metal materials constituting the pad 2 are brought into close contact with each other to cause mutual diffusion and alloy formation, thereby joining.

However, the size of the pad 2 and the distance between the adjacent pads 2 have been reduced with the miniaturization of semiconductor products. Accordingly, the size of the thin metal wire 5 crushed at the time of pressure bonding has been reduced. It is necessary to reduce the size so that a short circuit does not occur between adjacent pads 2. In addition, the miniaturization of wiring patterns formed on the surface of the semiconductor chip 1 has been advanced. At this time, in order to prevent these wiring patterns from being eroded by charge transfer, the material of the wiring patterns is made of aluminum. Containing a small amount of additive such as Cu. In general, the bonding pad 2 is also made of the same material as the wiring pattern for reasons such as shortening the manufacturing process of the semiconductor chip.

[0006]

The hardness of an oxide film formed on the surface of the pad 2 changes depending on the kind and amount of a small amount of additive. For example, in the case of an aluminum pad to which 1% Si is added, Vickers hardness Shows a surface hardness of about 30 (Hv), whereas an aluminum pad to which 0.5% Cu is added in addition to 1% Si has a Vickers hardness of about 70 Hv, which is twice as high. There is the above hardness difference.

In such a pad having a high surface hardness, FIG.
As shown in FIG. 8A, a crack 14 is easily formed in the pad 2 by the impact force given by the tool 4 at the time of crimping. In the pad 2 having such a crack 14, as shown in FIG. May be separated from the semiconductor chip 1, which may cause a decrease in the reliability of the semiconductor product. In addition, since the metal thin wire 5 receives a large impact force during crimping, as shown in FIG. 9, the metal thin wire 5 after crimping may be significantly crushed, causing a short-circuit 15 between adjacent pads 2 in some cases. .

In order to prevent such a problem, the operator must set conditions for the control section such as reducing the rolling speed and pressing force of the tool 4 so as to reduce the impact force exerted on the pad 2 by the tool 4. Had to do. In addition, if the conditions suitable for a pad with a high surface hardness are applied to a pad made of a material with a low surface hardness, sufficient adhesion cannot be obtained due to the small collapse of the fine metal wire, causing defects such as non-adhesion,
Problems such as a decrease in productivity due to a decrease in the rolling speed of the tool occur.

Therefore, it is necessary to set optimum conditions for each surface hardness of the pad in stable production. In order to find the optimum conditions, after the conditions are changed, wire bonding is actually performed. The condition of the product,
For example, it is performed by repeating the operation of checking the size of a crushed metal wire, the presence or absence of a crack, and the like.

Here, a description will be given, with reference to FIG. 10, of an operation procedure for mass-producing an actual semiconductor product.
The operator sets conditions such as the rolling speed and the pressing force of the tool described in the specification sheet for each type of product (step 30).
1). The conditions described in the specifications for each type of the product are obtained by previously searching for the optimum conditions for each surface hardness of the pad of the product by another worker while bonding as described above. .

Next, the worker performs bonding on a small amount of the product (step 302), and the state of the product, for example,
The size of the crushed metal wire, the presence or absence of cracks, and the like are confirmed by an appearance inspection using a microscope (step 303). At this time, if a defective product occurs (step 304), fine adjustment of the condition setting is performed (step 305). The confirmation of the condition setting and the fine adjustment work are also necessary in order to cope with a case where the surface hardness of the pad varies between the production lots of the semiconductor chip.

[0012] If no defective products are found in the condition setting after the confirmation and fine adjustment using the small amount of products (step 306), wire bonding is performed on a large number of products.
(Step 307) If a defective product such as a crack of the pad is found in the sampling inspection or the like during the production (Step 308), the condition is set again (Step 305).

As described above, the work of setting the optimum condition for each surface hardness of the pad requires a great deal of labor.
If the conditions are not suitable, there is a problem that many defective products are generated. In particular, the work of searching for the optimum conditions depends on the experience and skills of the worker, and thus the quality and productivity of the product are uneven by the worker.

Further, it has been confirmed that the hardness of the surface of the pad changes depending on the thickness and layer structure of the pad in addition to the difference depending on the type and amount of the additive described above. Nowadays, the frequency of searching for the optimum condition for each surface hardness of the pad and the risk of occurrence of defective products are increasing.

The present invention has been made in view of the above problems, and a main object of the present invention is to enable reliable and easy connection of wires to various semiconductor devices having different pad surface hardnesses. A wire bonding apparatus and a wire bonding method are provided.

[0016]

In order to achieve the above object, a wire bonding apparatus according to the present invention comprises a tool for pressing a bonding wire against a pad and an arm supported by a bond head. What is claimed is: 1. A wire bonding apparatus comprising: at least a moving unit on a pad; and a control unit for controlling an operation of the arm and the bond head, wherein a measurement of measuring a depth of an indentation formed on the pad by the tool. Means, storage means for storing a predetermined bonding condition, and determination means for setting the bonding condition by comparing the information measured by the measurement means with the information stored in the storage means. It is a thing.

In the wire bonding method of the present invention, (a) a tool for pressing a bonding wire against a pad is moved and pressed down on the pad via an arm supported by a bond head to form an indentation. Process and
(B) a step of measuring the depth of the indentation formed on the pad by the tool; (c) a step of comparing the measured depth of the indentation with information stored in advance in storage means; And) setting an appropriate bonding condition based on the comparison result.

In the present invention, the depth of the indentation may be measured by a laser displacement meter, and the information stored in the storage means includes the depth of the indentation, the lowering speed of the tool, the pressing force, It is preferable to include at least one or more pieces of information of the pressurizing time and the heating temperature. In addition, the present invention is preferably applied to any one of a thermocompression bonding wire bonding apparatus, an ultrasonic compression bonding wire bonding apparatus, a thermocompression bonding wire bonding apparatus using ultrasonic waves, and a TAB bonding apparatus.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION In a preferred embodiment of the wire bonding apparatus according to the present invention, a tool (4 in FIG. 1) for pressing a bonding wire against a pad (2 in FIG. 1), and the tool is moved up and down. Arm (6 in FIG. 1), a bond head (7 in FIG. 1) including the arm and moving on an XY stage, and a control unit (7 in FIG. 1) for controlling the operations of the arm and the bond head. 1
0), a laser displacement meter (12 in FIG. 1) for measuring the depth of an indentation formed on the pad by the tool, and a memory unit (FIG. 1) for storing predetermined bonding conditions.
And 11) comparing the depth of the indentation measured by the laser displacement meter with the information stored in the memory unit, and automatically setting a bonding condition suitable for the pad.

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention;

Embodiment 1 A wire bonding apparatus according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view for explaining the configuration of a wire bonding apparatus according to a first embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view of a tool tip. FIGS. 3A and 3B are diagrams for explaining a state in which an indentation is generated by bonding. FIG. 3A is a plan view, and FIG.
Is a sectional view. FIG. 4 is a flowchart showing the procedure of bonding, and FIG. 5 is a diagram for explaining how the indentation is measured by the wire bonding apparatus of this embodiment.

First, the configuration of the wire bonding apparatus according to the present embodiment will be described with reference to FIG. 1. This apparatus includes a pad 2 formed on the surface of a semiconductor chip 1 and an external terminal called a lead 3. It is wired by a thin metal wire 5 derived from the tip of a hollow tool 4,
A bond head 7 for vertically moving a bond arm 6 to which a tool 4 is attached at the tip, an XY table 8 on which the bond head 7 is loaded so as to be movable in two horizontal axes, and an operation of each of these mechanisms is controlled. It has a control unit 10 and a memory unit 11 for storing information of optimum condition set values corresponding to each product described later. In addition, the semiconductor chip 1
Below the lead 3 is provided a heater 9 for supplying thermal energy necessary for connecting the thin metal wire 5. Furthermore,
A laser displacement gauge 12 for measuring a distance in the vertical direction is provided above the bond head 7, and is connected so that the information is transmitted to the control unit 10.

Next, the shape of the tip of the tool 4 used in the wire bonding apparatus will be described with reference to FIG. 2. A plurality of tips of the tool 4 are arranged on the surface of the semiconductor chip 1 at fine intervals. It has a thin and sharp conical shape according to the size of the pad 2. In the center thereof, a hole 41 for leading out the thin metal wire 5 and a chamfer portion 4 necessary for leading out, crimping and cutting the thin metal wire 5 are provided.
1 and an arc portion 43. In addition, the diameter of the tip of the tool 4, the hole 41, the chamfer 42,
The size of the arc portion 43 differs depending on the thickness of the thin metal wire 5 used, the arrangement interval of the pads 2 and the like.

Next, with reference to FIG. 3, the setting of the optimum conditions corresponding to each product stored in the memory unit 11 in advance will be described. The depth of the indentation 13 formed on the surface of the pad 2 by the tool 4 as shown in FIG. 3 has a correlation with the hardness of the surface of the pad 2 when the amount of energy for forming the indentation 13 is constant. It has been confirmed by the inventor's experiment that the depth of the indentation 13 is shallower as is higher. The condition that the amount of energy for forming the indentation 13 is constant means that the control unit 10 in the wire bonding apparatus.
By controlling the lowering speed of the tool 4, the pressing force, the tip shape of the tool 4, and the heating temperature of the heater 9 controlled by the controller 9, the temperature can be controlled.

As an example, the lowering speed of the tool 4 is set to 0.1
mm / sec, pressure 2 gf, pressurizing time 5 seconds, the diameter of the tip of the tool 4 is 140 μm, the diameter of the hole 41 is 43 μm, and the diameter of the chamfer 42 is 6
Table 1 shows the depths of the indentations 13 in the two types A and B having the pads 2 having different surface hardnesses when the tool 4 having the tip shape of 4 μm and the radius of the arc portion 43 of 25 μm is used. Table 1 also shows these A,
In two types B, the fine metal wire 5 crushed during crimping
The condition setting value of the wire bonding apparatus capable of maintaining the size of the wire bonding and the bonding strength between the thin metal wire 5 and the pad 2 at a certain reference value or more is shown as the optimum condition setting value.

[0026]

[Table 1]

As shown in Table 1, the optimum condition setting values that differ depending on the difference in the surface hardness of the pad 2 and the corresponding information on the depth of the indentation of the tool 4 are stored in the memory unit 11 in advance.

Next, with reference to FIG. 4, description will be given of an operation for changing the type of a product when mass production is performed by the wire bonding apparatus according to the present embodiment.

First, the control unit 10 drives the XY stage 8 to move the tool 4 above the pad 2 (step 101). Next, the bond arm 6 of the bond head 7 is driven, and the tool 4 is pressed down on the pad 2 at a constant descent speed, pressure, and pressing time (step 102). At this time, if the metal wire 5 is interposed between the tool 4 and the pad 2, it is difficult to measure the depth of the indentation 13 to be performed next. Therefore, it is preferable to remove the metal wire 5 from the tool 4. .

Next, the control unit 10 raises the tool 4 and drives the XY stage 8 to move the laser displacement meter to a position above the pad 2 that has pressed down the tool 4 (step 10).
3). Here, the control unit 10 emits a laser beam from the laser displacement meter 12 while driving the XY stage 8, thereby controlling the laser displacement meter 12 and the pad 2 within a certain range on the surface of the pad 2 as shown in FIG. The depth of the indentation 13 is measured by measuring the distance to the surface and calculating the difference between the shortest distance and the longest distance (step 104).

Next, the control unit 10 compares the measured depth of the indentation 13 with the depth of the indentation stored in the memory unit 11 in advance, calculates the surface hardness of the pad 2, and calculates the surface hardness of the pad 2. Optimum condition setting values are stored in the memory unit 11
(Step 105). Then, wire bonding for a large number of products is performed under the optimum condition setting (step 106).

By the above-described series of operations, optimum conditions can be set for the changed product type.

As described above, once the tool 4 is pressed against the pad 2, the indentation 13 is measured by the laser displacement meter 12, and
By comparing the result with data stored in the memory unit 11 in advance and setting the optimum bonding conditions, a highly reliable bonding operation can be performed without depending on the operator.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 6 is a flowchart showing a procedure for performing bonding by the wire bonding apparatus according to the second embodiment of the present invention.

In the first embodiment, the optimization of the condition setting on the pad side of the wire bonding apparatus has been described. However, the optimization of the condition setting on the lead side can also be applied. The object on which 13 indentations are formed by the tool 4 is used as the lead 3 instead of the pad 2.

The operation when mass production is performed by the wire bonding apparatus according to the present embodiment will be described with reference to FIG. 6. First, the control unit 10 drives the XY stage 8 and moves the tool 4 above the leads 3. Move (Step 2
01). Next, the bond arm 6 of the bond head 7 is driven, and the tool 4 is pressed down to the lead 3 at a constant descent speed, pressing force, and pressing time (step 202).

Subsequently, the control unit 10 raises the tool 4 and drives the XY stage 8 to move the laser displacement meter above the lead 3 that has pressed down the tool 4 (step 2).
03). Here, the control unit 10 measures the depth of the indentation 13 by irradiating the laser beam from the laser displacement meter 12 while driving the XY stage 8 (Step 204).

Next, the control unit 10 compares the measured depth of the indentation 13 with the depth of the indentation stored in the memory unit 11 in advance, calculates the surface hardness of the lead 3, and calculates the surface hardness of the pad. Optimum condition setting values are stored in the memory unit 11
(Step 205). Then, wire bonding is performed on a large number of products under the optimal setting of these conditions (step 206).

As described above, in the present embodiment, the depth of the indentation 13 formed in the lead 3 is measured, and the condition setting value corresponding to the depth is called from the memory unit 11 to change the state of the lead 3. Suitable conditions can be set automatically. As a result, it is possible to always set the optimum conditions even for products such as LOC in which the sticking force of the leads fluctuates, and to reduce the number of work steps, reduce defective products, and improve the productivity. The same effect as the example can be obtained. Further, the effect can be doubled by using the optimization of the condition setting on the pad side shown in the first embodiment.

The present invention is not limited to the thermocompression bonding wire bonding apparatus shown in the above embodiment, but may be applied to an ultrasonic bonding method, a thermocompression bonding wire bonding apparatus and a TAB bonding apparatus. It is applicable, and the same effects as those of the above-described embodiment can be obtained.

[0041]

As described above, according to the present invention,
The following effects are obtained.

A first advantage of the present invention is that the number of man-hours required for setting conditions corresponding to products can be reduced. The reason is that since the apparatus automatically sets conditions corresponding to the state of the product, there is no need for a manual operation such as adjusting the condition set value while checking the state of the product.

The second effect of the present invention is that the occurrence of defective products can be reduced and the reliability of semiconductor products can be improved. The reason is that the apparatus always sets the optimum conditions, so that it is possible to prevent the occurrence of defects due to inappropriate setting of the conditions by the operator.

A third effect of the present invention is that productivity can be improved. The reason is that the time required by the operator to set the conditions corresponding to the product has been shortened by automation, and that the condition setting including the speed conditions corresponding to each product state is always optimized by automation. Because you can.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a configuration of a wire bonding apparatus according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a tool tip of the wire bonding apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram for explaining how an indent is formed by a wire bonding apparatus.

FIG. 4 is a flowchart showing a procedure for performing bonding by the wire bonding apparatus according to the first embodiment of the present invention.

FIG. 5 is a diagram for explaining how an indentation is measured by the wire bonding apparatus according to the first embodiment of the present invention.

FIG. 6 is a flowchart showing a procedure for performing bonding by a wire bonding apparatus according to a second embodiment of the present invention.

FIG. 7 is a perspective view illustrating a configuration of a conventional wire bonding apparatus.

FIG. 8 is a cross-sectional view for describing a defect in conventional wire bonding.

FIG. 9 is a cross-sectional view for describing a problem in conventional wire bonding.

FIG. 10 is a flowchart for explaining a conventional wire bonding procedure.

[Explanation of symbols]

 Reference Signs List 1 semiconductor chip 2 pad 3 lead 4 tool 5 metal wiring 6 bond arm 7 bond head 8 XY stage 9 heater 10 control unit 11 memory unit 12 laser displacement meter 13 indentation 14 crack 15 short 41 hole 42 chamfer 43 arc

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-133442 (JP, A) JP-A-62-150730 (JP, A) JP-A-60-167340 (JP, A) JP-A 8- 64629 (JP, A) JP-A-51-120176 (JP, A) JP-A-6-89918 (JP, A) JP-A-9-64094 (JP, A) JP-A-10-112469 (JP, A) JP-A-11-288967 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/60

Claims (7)

(57) [Claims] A tool for pressing a bonding wire against a pad; a means for moving the tool onto the pad via an arm supported by a bond head; and a control for controlling the operation of the arm and the bond head. A wire bonding apparatus having at least a part, a measuring means for measuring a depth of an indentation formed on the pad by the tool, a storage means for storing a predetermined bonding condition, and the measuring means A wire bonding apparatus comprising: a determination unit that sets bonding conditions by comparing measured information with information stored in the storage unit. 2. The wire bonding apparatus according to claim 1, wherein the depth of the indentation is measured by a laser displacement meter. 3. The information stored in the storage means includes at least one or a plurality of information of a depth of an indentation, a lowering speed of a tool, a pressing force, a pressurizing time and a heating temperature. The wire bonding apparatus according to claim 1. 4. A wire bonding apparatus according to claim 1, wherein the wire bonding apparatus is a thermocompression bonding wire bonding apparatus, an ultrasonic bonding wire bonding apparatus.
Ultrasonic combined thermo-compression wire bonding machine and T
A wire bonding apparatus which is one of AB bonding apparatuses. 5. A step of: (a) moving a tool for pressing a bonding wire against a pad onto the pad via an arm supported by a bond head, and pressing down on the pad to form an indent; (b) the tool (C) comparing the measured depth of the indentation with information previously stored in the storage means; and (d) comparing the result of the comparison. And setting a suitable bonding condition. 6. The wire bonding method according to claim 5, wherein the depth of the indentation is measured by a laser displacement meter. 7. The information stored in the storage means includes at least one or a plurality of information of a depth of an indentation, a lowering speed of a tool, a pressing force, a pressing time, and a heating temperature. Item 7. The wire bonding method according to item 5 or 6.