JPH0645408A - Method and apparatus for wire bonding semiconductor device - Google Patents

Abstract

(57) [Abstract] [Purpose] In order to reduce the damage at the time of bonding to the IC chip electrode and to improve the bondability of the bonding to the inner leads, the holding temperature of the first bond and the second bond is set. It is possible to set independently, and perform accurate bonding. A wire of a semiconductor device by thermocompression bonding which performs a first bond for joining an electrode 9 of an IC chip 5 and a bonding wire 3 and a second bond for joining a bonding wire 3 and an inner lead 10. In the bonding method, the first bonding is performed at a low first temperature, and then the second bonding is performed at a high second temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wire bonding in the manufacture of semiconductor devices.

[0002]

2. Description of the Related Art Conventionally, as a technique in such a field,
For example, there were the following. Wire bonds using gold wires are roughly classified into a thermocompression bonding method and an ultrasonic combined thermocompression bonding method.

FIG. 3 is a sectional view of the wire bonding process of the conventional thermocompression bonding method using ultrasonic waves. First, as shown in FIG. 3A, the tip of the gold wire 3 protruding from the bonding tool 2 is heated by the electric discharge between the electric torch 1 and the gold wire 3. Then, as shown in FIG. 3B, a gold ball 4 is formed at the tip of the gold wire 3 protruding from the bonding tool 2.

Next, as shown in FIG. 3 (c), the bonding tool 2 is lowered, and the gold ball 4 is bonded to the electrode of the heated IC chip 5 (in the case of ultrasonic combined thermal compression, here). Ultrasonic waves are added in). Next, as shown in FIG. 3D, the bonding tool 2 is moved onto the heated inner lead 6 and lowered. At this time, the gold wire 3 forms a loop.

Next, as shown in FIG. 3 (e), after the loop is formed, the bonding tool 2 is raised, the clamp 7 is closed at a certain height, and the clamp 7 is further raised, so that a force is applied to the bonding portion and the gold wire is applied. 3 is cut. The above-mentioned steps are the first bond (1st Bond), that is, the step of joining the IC chip electrode 5 and the tip of the gold wire 3 (see FIG. 3C), and the second bond (2nd Band), that is, the gold wire 3. The process can be divided into a process of joining the inner lead 6 with the inner lead 6 (see FIG. 3D). Both of them obtain a joining force by forming an alloy (diffusion) of the gold wire and the metal of the bonding portion. Further, the diffusion is accelerated as the temperature becomes higher, and the bonding strength is obtained. Currently, both the first bond and the second bond are maintained at about 250 ° C. That is, in the case of the first bond, the IC chip electrode is a flat surface (a square electrode having a length almost equal to the crushed diameter of the gold ball as one side) formed by the Al vapor deposition film, and the bonding area with gold is almost the same. The area of a crushed gold ball is reached. Therefore,
Since a diffusion area can be obtained, joining is relatively easy.
There is no problem in bonding strength at about 0 ° C.

[0006]

However, the damage at the time of bonding the IC chip electrode to the base (film structure) tends to increase as the temperature increases. Therefore, it is desirable to bond at a lower temperature, but at the current temperature of about 250 ° C., cracks may occur under the electrodes depending on the bonding conditions of the wire bonder and the thickness (film thickness) of the underlayer (film structure) of the chip electrode. May occur.

In the case of the second bond, in the case of joining with the inner lead 6, the joining area with gold is limited to the portion which holds down the gold wire on one side of the bonding tool (on the semicircle of the tool), and the diffusion area. Is not as good as the first bond,
The bonding conditions are the same as those for the first bond, and peeling occurs when the bonding tool is pulled up after forming the loop.

Therefore, when performing normal bonding, a method of applying ultrasonic waves stronger than that of the first bond side is used. However, the normal 250C
In the bonding at °, an unstable etching frame with a tip shape such as an ultra-multi pin is arranged. 4A and 4B are views showing a conventional etching frame having an unstable tip shape such as a super-multi-pin structure. FIG. 4A is an overall plan view thereof, and FIG. 4B is an enlarged view of an A portion of FIG. 4A. FIG. 4B is a perspective view, and FIG.
FIG. 6 is a sectional view taken along line BB of FIG.

As shown in FIG. 4A, the tip portion 6a of the inner lead 6 adjacent to the die pad 8 is enlarged and shown [see FIGS. 4B and 4C], and the tip of the inner lead is shown. In the portion 6a, the side surface 6b is etched by a chemical, the bottom surface 6c becomes narrow, the bottom surface 6c becomes unstable, and ultrasonic transmission may not be stable, and peeling may occur (it may be difficult to prevent it under bonding conditions. When the sound wave is increased, the variation in the waveform also increases and sudden peeling occurs,
It may lead to abnormal wire loop shape). Here, 3 is a gold wire and 4 is a gold ball.

FIG. 5 is a schematic view of a heating device used in a conventional thermocompression bonding process. Here, 3 is a gold wire, 5 is an IC chip, 8 is a die pad, 9 is an IC chip electrode, 10 is an inner lead, 11 is a heater block, 1
2 is a thermocouple cable, 13 is a heater cable,
Reference numeral 14 is a heater unit, and 15 is a control unit.

As shown in this figure, the IC chip 5, the IC chip electrode 9 and the inner lead 10 are kept at the same temperature (about 250 ° C.) by the same heater block 11. The heat source is provided by the heater unit 14, and the temperature control is performed by the control unit 1.
Performed by 5.

There are the following problems regarding bondability. (1) Problems in bonding at the current temperature (up to 250 ° C) The first bond Depending on the bonding condition of the wire bonder, the variation in bonding, and the film thickness condition of the IC chip electrode (film structure thereunder), etc. At times, the electrodes may be damaged, and eventually cracks may occur under the electrodes, causing electrical leakage, which may result in defective elements.

Second bond In an unstable etching frame having a tip shape such as an ultra-multi pin, when ultrasonic output is increased to obtain bonding strength, ultrasonic transmission is not stably performed and sudden peeling occurs. May occur. Further, the wire loop shape may be similarly deformed.

(2) Problems caused by keeping the first bond and the second bond at the same temperature In consideration of the above (1), if the temperature is lowered in order to reduce the damage of the first bond, The bonding force of the second bond is reduced and peeling is feared. When the temperature is raised to obtain a stable bonding force of the second bond, the IC chip electrode (film structure below) in the first bond There is concern about damage.

Therefore, the "same temperature" is a major obstacle to improving the bondability of both. (3) Regarding the device, in the conventional device shown in FIG.
The electrodes of the chip and the inner leads can be held only at the same temperature, and the temperature cannot be set individually. The present invention eliminates the above-mentioned problems, reduces damage at the time of bonding to an IC chip electrode, and improves the bondability of bonding to an inner lead so as to maintain the first bond and the second bond. It is an object of the present invention to provide a wire bonding method for a semiconductor device and a device for the semiconductor device, in which the temperature can be independently set and accurate bonding can be performed.

[0016]

In order to achieve the above object, the present invention provides a first bond for bonding an electrode of a semiconductor element and a thin metal wire, and a first bond for bonding a thin metal wire and an inner lead. In the wire bonding method for a semiconductor device by thermocompression bonding, the first bonding is performed at a first temperature, and then the second bonding is performed using the first bonding.
The second temperature, which is higher than the above temperature, is used.

The first temperature is approximately 150 ° to 2
10 ° and the second temperature is approximately 250 to 300 °
It is a degree. Furthermore, in a wire bonding apparatus for a semiconductor device by thermocompression bonding, a first bond for bonding an electrode of a semiconductor element and a metal thin wire and a second bond for bonding a metal thin wire and an inner lead are provided. When performing the first bonding, the heater that sets the bonding pad to the first temperature, the first heater control unit that controls the temperature of the heater, and the second inner bond, the inner lead is the first A heater that is set to a second temperature higher than the above temperature and a second heater control unit that controls the temperature of the heater are provided.

[0018]

According to the present invention, a semiconductor device by thermocompression bonding is used, in which a first bond for bonding an electrode of a semiconductor element and a metal thin wire and a second bond for bonding a metal thin wire and an inner lead are bonded. In the wire bonding method, in the first bond, a temperature (150 to 21 ° C.) lower than a normal temperature (250 to 21 ° C.) is set so that the IC chip electrode (underlying film structure) can be stably bonded with less damage.
Bonding is performed at 0 ° C. In the second bond, in order to obtain a stable bonding force without greatly depending on ultrasonic waves in an etching frame or the like having an unstable tip shape such as an ultra-multi pin, a temperature higher than normal (250 ° C) (~ Bonding is performed at about 300 ° C.

Therefore, it is possible to reduce damage to the film structure under the bonding electrode. In addition, it is possible to eliminate sudden damage due to variations in bonding. Moreover, the joining force between the inner lead and the gold wire can be significantly improved. Further, since the heater block is divided into a die pad heater block and an inner lead heater block and each is controlled, the temperature of the die pad and the inner lead can be accurately set independently.

[0020]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a perspective view of a heating device for thermocompression bonding wire bonding showing an embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. As shown in these figures, 16 is an inner lead heater block, 17 is a die pad heater block, 18 is a die pad heater,
Reference numeral 19a is a thermocouple tip portion, 20 is a second heater unit, 21 is a second control unit, 27 is a first heater unit, and 28 is a first control unit.

As shown in these figures, in this embodiment, the heater block 11 is divided into a die pad heater block 17 and an inner lead heater block 18. The die pad heater block 17 is composed of:
By the second control unit 21, a lower temperature (150 ° C to 210 ° C) than usual (conventional: about 250 °).
Heater block 1 for inner leads
The first control unit 28 controls the temperature 6 to a temperature higher than usual (about 250 to 300 ° C.).

Since the die pad heater block 17 is expected to be quite small (depending on the die pad size), the die pad heater 18 and a thermostat for monitoring the temperature of the heater are used in utilizing the limited space. The couple 19 is inserted from the bottom. Therefore, first, the first bond for joining the electrode 9 of the IC chip 5 and the bonding wire 3 is connected to the second bond.
The die pad heater block 17 controlled by the control unit 21 controls the temperature of the die pad 8 to a relatively low temperature of 150 ° C to 210 ° C.

Next, the second bond for joining the bonding wire 3 and the inner lead 10 is connected to the inner lead 1.
0 is carried out by controlling the temperature to a relatively high temperature of about 300 ° C. Here, each temperature control is, as shown in FIG.
In the die pad heater block 17 in which the bonding is performed, the temperature of the die pad heater 18 is detected by the thermocouple 19 arranged around the die pad heater 18, and the output signal thereof is input to the first control unit 28. In the first control unit 28, the first heater unit 27 is controlled by the output control signal from the first control unit 28 so as to be compared with the reference value and reach the set temperature.

Here, the die pad heater 18 and the thermocouple 19 are inserted and attached from below the heater block 11. Further, in the inner lead heater block 16 in which the second bonding is performed, as shown in FIG.
The temperature of 0 is detected by the thermocouple 31 arranged in the vicinity thereof, and the output signal thereof is inputted to the second control unit 21, which is compared with the reference value and set. To reach the temperature
The second heater unit 20 is controlled by the output control signal from the second control unit 21.

Here, the die pad heater block 17 is used.
The thermocouple 31 is inserted from the side of the heater block 11 and attached. With this structure, damage to the film structure below the bonding electrode can be reduced. In addition, it is possible to eliminate sudden damage due to variations in bonding. Therefore, it is possible to reduce the electric leakage failure caused by the damage under the electrode where the first bonding is performed.

At the present time, ICs are in the age of high integration, and the film structure is very thin, as seen in multilayer wiring.
It tends to be brittle. Therefore, the damage under the electrode must be taken into consideration more than ever, and the damage reduction by low temperature bonding can exert a great effect. It has been confirmed that in the low temperature bonding, the occurrence of cracks decreases when the temperature is around 210 ° C or lower, and the reliability due to thermal stress is maintained up to approximately 150 ° C.

Further, the inner lead is bonded at a higher temperature (about 300 C °) than the normal (about 250 C °) (second
The bonding force between the inner lead and the gold wire can be significantly improved by the bonding. Therefore, even in the case of an unstable etching frame with a tip shape such as ultra-multi pins,
It becomes possible to perform stable bonding without greatly depending on the ultrasonic wave for the bonding force, and it is possible to prevent the second bond from peeling off.

Also, in the case of a normal press-processed lead frame, improvement in bonding property can be expected to reduce the inner lead plating thickness and further direct bonding without plating. Further, in the heater block, it is divided into a die pad heater block and an inner lead heater block, and in order to control each of them,
The temperature of the die pad and the inner lead can be set independently.

The thin metal wire is not limited to the gold wire,
For example, Al wire or Cu wire may be used. Further, the present invention is not limited to the above-described embodiments, and various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention.

[0030]

As described above in detail, according to the present invention, the following effects can be obtained. (1) Bonding (first bond) to the electrode of the IC chip at a temperature lower than normal (about 250 ° C.) (about 150 ° C. to 210 ° C.) can reduce damage to the film structure below the bonding electrode. it can. Also,
It is possible to eliminate sudden damage due to variations in bonding.

Therefore, it is possible to reduce the electric leak failure caused by the damage under the electrode where the first bonding is performed. (2) Bonding (second bonding) to the inner leads at a higher temperature (about 300 ° C.) than normal (about 250 ° C.) can significantly improve the bonding force between the inner leads and the gold wire.

Therefore, even in the case of an unstable etching frame having a tip shape such as ultra-multi-pins, stable joining can be performed without largely depending on the ultrasonic wave.
The peeling of the second bond can be prevented. Also,
Even in the case of a normal press-processed lead frame, the inner lead plating thickness can be reduced by improving the bondability,
Furthermore, direct bonding without plating can be expected.

(3) Since the heater block is divided into a die pad heater block and an inner lead heater block and each is controlled, the temperature of the die pad and the inner lead can be set independently and accurately. .

[Brief description of drawings]

FIG. 1 is a perspective view of a heating device for thermocompression bonding wire bonding showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA of FIG.

FIG. 3 is a cross-sectional view of a wire bonding process of a conventional thermocompression bonding method using ultrasonic waves.

FIG. 4 is a diagram showing a conventional unstable etching frame having a tip shape such as an ultra-multi pin.

FIG. 5 is a schematic view of a heating device used in a conventional thermocompression bonding process.

[Explanation of symbols]

 3 Bonding Wire 5 IC Chip 8 Die Pad 9 IC Chip Electrode 10 Inner Lead 11 Heater Block 16 Inner Lead Heater Block 17 Die Pad Heater Block 18 Die Pad Heater 19 Thermocouple 19a Thermocouple Tip 20 Second Heater Unit 21 No. 2 control unit 27 1st heater unit 28 1st control unit

Claims (4)

[Claims] 1. A wire bonding method for a semiconductor device by thermocompression bonding, which comprises a first bond for bonding an electrode of a semiconductor element and a thin metal wire and a second bond for bonding a thin metal wire and an inner lead. (A) The first bonding is performed at a first temperature, (b) Next, the second bonding is performed at a second temperature higher than the first temperature. Wire bonding method for equipment. 2. The first temperature is approximately 150 ° to 210 °.
2. The wire bonding method for a semiconductor device according to claim 1, wherein the second temperature is about 250 ° to 300 °. 3. A wire bonding apparatus for a semiconductor device by thermocompression bonding, which comprises a first bond for bonding an electrode of a semiconductor element and a thin metal wire and a second bond for bonding a thin metal wire and an inner lead. (A) a heater block that sets the bonding pad to a first temperature in performing the first bonding; (b) a first heater control unit that controls the temperature of the heater; and (c) the first heater control unit. In performing the bonding of No. 2, a heater block for setting the inner lead to a second temperature higher than the first temperature, and (d) a second heater control unit for controlling the temperature of the heater are provided. A wire bonding apparatus for a semiconductor device, which is characterized in that 4. The wire bonding apparatus for a semiconductor device according to claim 3, wherein a heater set to the first temperature and a thermocouple for monitoring the temperature are inserted from a lower portion of the heater block.