JPH11265907A - Aluminum wire bonding apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain improvement and stability in the reliability of bonding load by automatically correcting the change of load caused by the dispersion of equipment at suitable time. SOLUTION: Concerning an aluminium wire bonding device provided with an ultrasonic oscillator, ultrasonic horn 3 to be oscillated by the ultrasonic oscillator, wedge 4 for transmitting ultrasonic vibrations outputted from the ultrasonic horn 3 while changing them to vibrations orthogonal to the lengthwise direction and pressurizing device 5 for applying lengthwise pressure to the wedge so as to bond an aluminium wire supplied to the top end of the wedge 4 while pressing its top end to the bonding position of a semiconductor, this device is equipped with a sensor 10 for measuring the wedge top end load and a correcting means 18 for correcting the specified value of the bonding load measured by the sensor 10 with the real load and correcting the specified value of the bonding load based on the deviation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum wire bonding apparatus and method which are one of semiconductor manufacturing apparatuses.

[0002]

2. Description of the Related Art It is known that when a gold wire is bonded to an aluminum electrode of a silicon IC at a high temperature of 200 ° C. or higher, an intermetallic compound of aluminum and gold is generated. This is extremely fragile, and is likely to break due to shock, vibration, and overcurrent after the IC becomes a product. In order to avoid such obstacles, a method of bonding an aluminum wire on an aluminum vapor-deposited film has been performed using ultrasonic waves.

The characteristics of ultrasonic bonding are as follows: (1) Room temperature bonding that does not require heating and does not melt metal. (2) There is no contamination due to flux or generation of oxides due to sparks. (3) Dissimilar metals can be welded. Especially copper and aluminum are suitable. (4) The joint has the same strength as solder in the alloy state. (5) Even in a high-temperature heat cycle, there is no difference in the coefficient of thermal expansion of the joint and no stress breakdown. (6) A major feature of ultrasonic bonding is that the resistance value at the bonding portion is almost zero.

[0004] The principle of this ultrasonic wire bonding is as follows.
As shown in FIG. 7, between the ultrasonic horn 21 and the receiving jig 23, a metal 24 and a metal 25, for example, aluminum (wire 24
) And copper (IC board 25).
When the ultrasonic wave from 2 is applied to the ultrasonic horn 21 and the ultrasonic vibration in the horizontal direction is transmitted to the metal 25 by applying pressure, the metal 24 and the metal 25 contact each other between the contact surfaces of the metal 24 and the metal 25. The oxide film covering the surface of the substrate is destroyed and activated metal appears. Since pressure is applied to the activated metal, the distance between the active molecules is reduced and metal bonding is performed.

[0005]

In the known semiconductor wedge bonding, when a wire loop is formed, the load applied to the wire 24, the power, and the power application time are three important factors. Controlling the load is usually
A method using one or both of a mechanical spring and an electrically linear coil is common. However, there is a variation in the load due to the performance of each spring or coil. Further, it is difficult for the load value set at the time of manufacturing the device to maintain the same value thereafter. It is an object of the present invention to improve the reliability and stabilization of a bonding load by automatically performing a timely automatic correction for a load change due to a variation in equipment.

[0006]

In order to solve the above problems, an aluminum wire bonding apparatus according to the present invention comprises an ultrasonic oscillator, an ultrasonic horn excited by the ultrasonic oscillator, and an output from the ultrasonic horn. The ultrasonic vibration to be provided, a wedge for transmitting the vibration in a direction perpendicular to the longitudinal direction and transmitting, and a pressurizing device for applying a pressing force in the longitudinal direction to the wedge, the wedge was fed to the tip of the wedge In an aluminum wire bonding apparatus in which the tip of an aluminum wire is pressed against a bonding portion of a semiconductor and joined, a sensor for measuring a wedge tip load and a specified value of a bonding load measured by the sensor are compared with an actual load, and a deviation thereof is calculated. And a correcting means for correcting the specified value of the bonding load based on the following. Also,
The aluminum wire bonding method of the present invention is an aluminum wire bonding method in which the tip of an aluminum wire serving as a terminal lead is pressed against a semiconductor bonding point with a wedge tip to join the aluminum wire tip by ultrasonic vibration. It is characterized in that it is pressed against a load measuring sensor with a specified bonding load, the bonding load at that time is measured, the specified value of the bonding load is corrected based on the measured value, and bonding is performed using the corrected value as a specified value. And

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a semiconductor wedge bonding method, which uses an electrical or software means to prevent individual differences due to manufacturing or human adjustment which are important factors for each bonding load device. This allows the device itself to automatically and automatically adjust the true load uniformity condition for each device.

FIGS. 1 and 6 show a general structure example of a head portion of an aluminum wedge wire bonder. Here, since one end of the load spring 1 is fixed to the body 2, the horn 3
And a load is generated in a downward direction with respect to the wedge 4 which transmits ultrasonic vibration. To change this force,
It is possible by changing the amount of deflection of the spring. Further, the magnet part 6 on the outer periphery of the coil part of the linear coil capable of generating an electrically linear force is similarly fixed to the body 2, and the electric coil 5 inside it is subjected to framing by applying a current to the coil. Generates a force according to the law of In the current aluminum bonder, this current value is 1/25
An electric resolution value is input from a computer, for example, from 5 to 255/255, and the force is made variable.

In this way, it is possible to control the bonding load on the aluminum wire 9 guided between the wedge tip 7 and the mating sample 8 to be bonded. Thrust is different, the actual load at the wedge tip will not be as theoretical as possible due to bearing friction or other mechanical springs.

FIG. 2 shows the results of actually measuring the wedge tip load with separate heads. As can be seen from FIG.
It can be seen that there is variation only in the electrical resolution from 255 to 255/255.

According to the present invention, a load cell 10 which is a measuring sensor for measuring such a wedge tip load is installed near the head, and the wedge tip 7 is touched to the load cell 10 by driving a Z-axis control motor. Press down one hundred microns. The horn 3, the mechanical spring 1 pressing the horn 3, and the coil of the linear coil are configured to be pushed back. At the moment of the touch, the moment when the horn is pushed back by the touch is detected, and the starting point of the pushing back is detected. The voltage detected by the load cell 10 and proportional to the load is amplified by the conversion amplifier 17, converted into a current by the controller 18, and supplied to the electric coil 5.

FIG. 3 is a flowchart showing the procedure of the bonding method of the present invention. In the figure, step 10
At 0, the wedge is moved to the bonding position. Next, at step 110, the current bonding load is set. In step 120, the analog signal (voltage) output from the load cell is converted into a gram value. In step 130, the converted value is compared with the current set value. If it is within the allowable range, it is determined in step 140 that it is normal.
If not, the process proceeds to step 160. If it greatly exceeds the allowable range, an alarm is generated in step 150.
In step 160, automatic correction is performed for cases outside the allowable range, and in step 170 the load is changed to check the linearity. If it is normal, it is determined that it is normal in step 180, and if it is above, an alarm is generated in step 150. In this manner, the load change values a and b of the load cell 10 are sampled for the pressing amount between any two points shown in FIG.

FIG. 5 shows a sample 2 with respect to the theoretical value.
It is a graph of load change c and d of two wedge tips.
It can be seen that c and d vary from the theoretical values. According to the present invention, the loads of the variations c and d are measured in advance or periodically, and the respective resolutions from the above 1/255 to 255/255 are determined by a software method so as to match the theoretical value apparently. The value of the current flowing through the linear coil is controlled.

[0014]

As described above, according to the present invention, the uniformity of the load applied to each device can be obtained, the bonding conditions can be stabilized, and the bonding results for each device can be made uniform.

[Brief description of the drawings]

FIG. 1 is a side view showing a general structure of a head portion of an aluminum wedge wire bonder.

FIG. 2 is a graph showing a relationship between a wedge tip load and a coil current.

FIG. 3 is a flowchart showing a procedure of automatic correction in the bonding method of the present invention.

FIG. 4 is a graph showing a relationship between a pressing amount and a load.

FIG. 5 is a graph showing a relationship between a theoretical value and a sample value regarding a load change value of a load cell.

FIG. 6 is an enlarged view showing a structure of a wire clamp unit.

FIG. 7 is an explanatory view showing the principle of a wire bonding method.

[Explanation of symbols]

Reference Signs List 1 load spring, 2 body, 3 horn, 4 wedge, 5 electric coil, 6 magnet, 7 wedge tip, 8 sample, 9 aluminum wire, 10 load cell, 11 wire receiver, 12 wire holder, 13 electric coil, 14 fulcrum , 15 mechanical spring, 16 movable piece, 17 conversion amplifier, 18 controller, 21 ultrasonic horn, 22 ultrasonic oscillator, 23 receiving jig, 2
4,25 metal

Claims (2)

[Claims] 1. An ultrasonic oscillator, an ultrasonic horn vibrated by the ultrasonic oscillator, and an ultrasonic vibration output from the ultrasonic horn converted into vibration in a direction orthogonal to the longitudinal direction and transmitted. An aluminum wire bonding apparatus comprising: a wedge to be formed; and a pressurizing device for applying a pressing force in the longitudinal direction to the wedge, and pressing and joining a tip of an aluminum wire fed to a tip of the wedge to a bonding portion of a semiconductor. A sensor for measuring a wedge tip load, and a correction means for comparing a specified value of the bonding load measured by the sensor with an actual load, and correcting the specified value of the bonding load based on a deviation thereof. And aluminum wire bonding equipment. 2. An aluminum wire bonding method in which a tip of an aluminum wire serving as a terminal lead is pressed against a bonding portion of a semiconductor with a wedge tip to bond the tip of the aluminum wire by ultrasonic vibration. An aluminum wire characterized in that it is pressed with a specified bonding load, the bonding load at that time is measured, the specified value of the bonding load is corrected based on the measured value, and bonding is performed using the corrected value as a specified value. Bonding method.