JP3152755B2 - Wire bonding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire bonding apparatus used in a bonding step of connecting a semiconductor chip and a lead frame using a metal wire during a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art A wire bonding apparatus used in a bonding step for connecting wires using metal wires is generally constructed as shown in FIG. That is, a bonding tool 14 for connecting the electrode pads of the semiconductor chip 11 and the leads on the lead frame 12 with a thin metal wire (wire) 13 made of Au or the like, and the bonding tool 14
And a bonding head 16 for supporting the transducer horn 15
And an XY table 17 for moving the bonding head 16 smoothly and strictly in the horizontal direction, a recognition TV camera 18 fixed to the bonding head 16 and moving integrally with the bonding head 16, and a camera 18. Image processing unit 19 for recognizing a target position from image information to be obtained
And a display 20 for displaying an image obtained by the camera 18, a control unit 21 for controlling the operation of the entire apparatus, and an operation unit 22 for issuing an operation command.

FIG. 3 is a view of the transducer horn 15 and the recognition TV camera 18 as viewed from above. The center of the bonding tool 14 and the center of the recognition TV camera 18 are deviated from each other. An offset amount (x1, y1) exists between the positions. This offset is unavoidable in order to prevent the bonding tool 14 from entering the field of view of the recognition TV camera 18, and the offset amount (x1, y1) is set as a unique value for each wire bonding apparatus by the control unit 21. Is stored in the memory of.

In normal bonding, first, image information is captured by the recognition TV camera 18 at each of two alignment positions on the semiconductor chip 11, and the chip is positioned with respect to a preset reference position for alignment. The shift amount is determined, and the positions of the respective electrode pads and leads are calculated. Subsequently, the bonding head 16 is moved in the horizontal direction by the stored offset amount, and the transducer horn 15 is moved up and down by a mechanism (not shown) while the bonding tool 14 is sequentially moved on the center of the electrode pad and then on the center of the lead. The connection is performed with the metal wire. Then, the connection process is repeated for all the electrode pads, thereby completing the bonding process.

Therefore, the stored offset amount (x
If (1, y1) is different from the actual value, the center of the electrode pad 23 on the semiconductor chip 11 may be displaced from the actual bonding position as shown in FIG. In addition,
The distances (δx, δy) in FIG. 4 indicate the above shift amounts. For this reason, storing an accurate offset amount is extremely important for the yield and quality of the product. Further, it is necessary to correct the offset amount every time the bonding tool 14 is exchanged, and the error needs to be corrected with a practical value and within an accuracy of several μm.

Incidentally, in recent years, high integration of semiconductor devices,
With the miniaturization, the electrode pads and leads have a smaller pitch and more pins, and higher precision is required. In such a situation, the work of correcting the offset amount is an extremely important management item. Conventionally, the offset amount correcting method of finely adjusting and storing the offset amount is performed in the following procedure.

Procedure 1: The transported semiconductor chip 11 is stopped at the bonding processing position, and the recognition TV camera 18
With this, an arbitrary virtual bonding target position on the semiconductor chip 11 is imaged. FIG. 5 shows a display screen 24 of the display 20 captured by the camera 18, and 25 in FIG. 5A indicates a virtual bonding target position (the electrode pad 23 in this example).
And 26 is a cross line displayed at the center of the display screen 24.

Next, the bonding head 16 is moved by the XY table 17 with reference to the cross line 26 displayed at the center of the display screen 24, and as shown in FIG. To match.

Procedure 2: From the position adjusted in Procedure 1,
The bonding head 16 is moved by the XY table 17 by the offset amount stored in advance, and dummy bonding is performed using ordinary bonding parameters such as bonding load, ultrasonic output, and bonding time. Bonding is performed, and as shown in FIG. 6, an impression 27 by the tool 14 is formed on the semiconductor chip or on the lead (in this example, on the semiconductor chip).

Step 3: The bonding head 16 is returned by the offset amount again, and the position of the impression 27 after the dummy bonding is imaged by the camera 18 to confirm the degree of coincidence. At this time, it is ideal that the intersection of the cross lines 26 is the virtual bonding target position, and the center of the indentation 27 just overlaps this virtual bonding target position.

However, as shown in FIG. 6, when the virtual bonding target position 25 does not coincide with the center of the impression 27, the projected impression 27 is displayed with reference to the cross line 26 on the display screen 24. The operator again finely adjusts the position of the bonding head 16 by using the XY table 17 so that the position of the bonding head 16 comes to the center of the screen 24, and visually adjusts the position. With this fine adjustment, the bonding head
The control unit 21 calculates 16 movement amounts (Δx, Δy).

Step 4: The movement amount (Δx, Δy) of the bonding head 16 calculated in step 3 is added to or subtracted from the offset amount (x1, y2) and stored as a true offset amount. After fine-tuning the offset amount by the above procedure,
An actual bonding process is performed.

[0013]

The above-described method of correcting the offset amount has the following problems.

First, since the formation of the bonding indentation by the dummy bonding is performed using the same parameter as the normal bonding operation, such as the load, which causes less product damage, a good indentation cannot be obtained and the indentation is formed. As shown in FIG. 7, depending on the position of the tool or the inclination of the tool, there is a limit in accuracy in determining the center of the bonding indentation because a one-sided contact occurs as shown in FIG. Second, since the correction of the offset amount is performed by the operator with the naked eye, skill is required, and there is an individual difference, which causes quality variation.

Third, due to the first and second problems, it is extremely difficult to accurately perform the correction by the conventional indentation, and it is necessary to inspect several products after wire bonding and correct the offset amount. Need to be repeated. For this reason, some products are often wasted. 4th
In addition, the offset amount must be accurately corrected each time the bonding tool is replaced, which is a problem in terms of work efficiency.

Fifth, a bonding tool must be pressed on a soft ground to form a clear indentation, but the lead frame is hard and a clear indentation can be obtained by a bonding process using ordinary bonding parameters. Therefore, dummy bonding is often performed on an electrode pad made of aluminum on a semiconductor chip. For this reason, the chip may be damaged during the dummy bonding. Needless to say, these problems have a great effect on yield and productivity. A first object of the present invention is to provide a wire bonding that can clearly form an indentation even on a relatively hard material such as a lead frame. A second object of the present invention is to provide a wire bonding capable of automating an offset amount correcting operation.

[0017]

According to the first aspect of the present invention, a super
To control the wire bonding means using sound waves, the parameters used for controlling the wire bonding means and controlling the normal bonding operation, and the dummy bonding operation for forming an indentation on the surface to be bonded. Used, and the above normal bonding operation
Overload for parameters used to control
Wave output and the wire bonding apparatus and a bonding control unit parameter holding portion is provided for holding the bonding time increased by Oh Ru parameters are provided.

According to the second invention, a wire bonding means having a bonding tool using ultrasonic waves, and the wire bonding means are used for controlling the wire bonding means and controlling a normal bonding operation. parameters and are used to control the dummy bonding operation to form the indentation with respect to the bonding surface, the normal of Bondi
The parameters used to control the
Te load, a parameter holding unit for holding the ultrasonic output and Ru Oh increased bonding time parameters, the center of the bonding tool and its recognition center are in the positional relationship of the offset, the more bonded to said wire bonding means Imaging means for capturing image information of the surface to be bonded, and indentations formed at the time of dummy bonding performed by the wire bonding means are captured as image information by the imaging means, and the center coordinates of the indentations are based on the image information. And a control means for calculating a shift amount of the dummy bonding with respect to the target position, and correcting the offset amount between the center of the bonding tool and the recognition center of the imaging means based on the shift amount. An apparatus is provided.

[0019]

By storing the dummy bonding parameters separately from the normal bonding parameters, indentations can be clearly formed on relatively hard materials such as leads. Further, the difference from the virtual bonding target position at the time of dummy bonding can be automatically measured by capturing the indentation shape as image information and obtaining the center coordinates.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. Since the configuration of the entire wire bonding apparatus according to the present invention is the same as that shown in FIG. 2, description thereof will be omitted, and only different points from the conventional one will be described.

FIG. 1 shows the control unit 21 for controlling the whole wire bonding apparatus of the present invention, and a TV camera for recognition.
FIG. 2 is a block diagram illustrating a configuration of an electric circuit including an image processing unit 19 that processes image information captured by 18. Reference numeral 31 in the figure denotes an operation unit that collectively includes, for example, the XY table 17 and the like that perform the mechanical operation in FIG.

In this embodiment, a bonding load, an ultrasonic output,
In addition to a data memory (A) 32 for storing parameters such as a bonding time, a data memory (B) for storing parameters such as a bonding load, an ultrasonic output, and a bonding time used at the time of dummy bonding at the time of offset amount correction. 33 are provided. In addition, this control unit
The offset data memory 34 stores an offset amount between the center of the bonding tool 14 and the recognition center of the recognition TV camera 18, a command from the operation unit 22 is input to the memory 21, The storage data of 32, 33, and 34 and an output from an arithmetic processing unit in the image processing unit 19 described later are input, and an arithmetic processing unit 35 that outputs an operation command based on these inputs, an output of the arithmetic processing unit 35 There is provided an operation control unit 36 that outputs an operation control signal based on the above and inputs the operation control signal to the operation unit 31.

On the other hand, in the image processing section 19, in addition to a reference image memory (A) 41 for storing reference image information used for normal chip alignment, an indentation shape obtained by dummy bonding is provided. A reference image memory (B) 42 for storing reference image information used when recognizing the
An A / D converter 43 for converting image information captured by the camera 18 into digital information, an image memory 44 for storing output information of the A / D converter 43 as image information, the reference image memory (A) 41, A correlator 45 for performing pattern matching of image information stored in the reference image memory (B) 42 and the image memory 44 to obtain coordinates, and the correlator 45
Is provided with an arithmetic processing unit 46 for inputting the coordinate data obtained in step (1) and calculating the amount of deviation (δx, δy) from the virtual target position. The deviation amount (δx, δy) calculated by the arithmetic processing unit 46 is calculated by the arithmetic processing unit 35 in the control unit 21.
Are stored in the offset data memory 34 via Next, the procedure for correcting the offset amount by the present apparatus will be described.

Procedure 1: The semiconductor chip transported
11 is stopped at the bonding processing position, the operator determines an arbitrary bonding target position for performing dummy bonding to the lead on the lead frame with reference to the cross line 26 on the display screen 24 of the display 20, and operates the operation unit 22. Input a command to start the correction operation.

Step 2: The bonding head 16 moves from the position determined by step 1 by an offset amount stored in advance in the offset data memory 34 of the control unit 21, and is fixed to the tip of the transducer horn 15 here. The tool 14 hits the lead, and a bonding impression is formed. At this time, the data memory (A)
The indentation is formed by using the special dummy bonding parameters stored in the data memory (B) 33 in which the load, ultrasonic output and bonding time are increased, instead of the normal bonding parameters stored in 32. Also, even if the lead is made of a hard material, a bonding impression can be formed satisfactorily. Therefore, indentations are clearly formed, and accurate correction can be performed.

Step 3: The bonding head 16 returns by the offset amount, and the virtual bonding target position is captured again by the recognition TV camera 18. Next, an operation of recognizing an indentation position by dummy bonding with respect to a target position is started. First, the formed impression is captured as image information by the camera 18 and stored in the image memory 44 via the A / D converter 43. Next, the reference image of the impression stored in the reference image memory (B) 42 and the actual image stored in the image memory 44 are subjected to pattern matching by the correlator 45, and the center coordinates of the impression are obtained. Then, in accordance with the coordinate data, the arithmetic processing unit 46 calculates the amount of deviation (δx, δy) from the virtual target position.

The bonding impression by the dummy bonding is transferred in a state where the shape of the bonding tool 14 is similar and is unique to the bonding tool. Therefore, if the indentation reference pattern for each bonding tool is stored in the reference image memory (B) 42, the center of the indentation can be satisfactorily obtained only by comparing the indentation with the correlator 45. Here, the method of recognizing the difference in position between the indentation reference pattern and the bonding indentation by pattern matching has been described. However, as another method, the center of the bonding indentation may be obtained by a feature extraction method without using a correlator. good.

Step 4: The shift amount (δ calculated in step 3)
(x, δy) is given as a correction value to the arithmetic processing unit 35 in the control unit 21 and is added to or subtracted from the initial offset amount (x1, y1) stored in the offset data memory 34 to obtain the true offset amount (x1, δ1). x2, y2) are obtained, are stored in the offset data memory 34 again, the offset amount is updated, and the correction operation ends.

The correct offset amount can be automatically stored in the above procedure. And then,
The bonding process is performed using the corrected offset amount.

[0030]

As described above, according to the present invention, the bonding parameters used in the dummy bonding performed for correcting the offset amount, which is the deviation between the recognition TV camera and the tip of the bonding tool, are as follows:
By storing the bonding parameters separately from the bonding parameters used during normal bonding, clear bonding impressions can be obtained. Further, by using the parameters for dummy bonding, it is not necessary to form an indent by performing dummy bonding on the semiconductor chip, and it is possible to form a good indent on a relatively hard lead frame.

Furthermore, the indentation formed by the dummy bonding is taken in as image information, and the difference between the virtual dummy bonding target position and the bonding indentation is automatically measured. Work can be automated. Therefore, a positioning operation by a skilled operator becomes unnecessary, and variation in quality can be suppressed.
Further, it is possible to effectively perform the offset amount correction every time the bonding tool is replaced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an electric circuit that integrally controls the entire wire bonding apparatus of the present invention.

FIG. 2 is a diagram showing a configuration of a wire bonding apparatus.

FIG. 3 is a top view of a transducer horn and a recognition TV camera of the apparatus of FIG. 2;

FIG. 4 is a diagram showing a state after bonding.

FIG. 5 is a view showing a display screen of a recognition TV camera of the apparatus shown in FIG. 2;

FIG. 6 is a view showing a display screen of a recognition TV camera of the apparatus shown in FIG. 2;

FIG. 7 is a view showing an indentation formed by dummy bonding.

[Explanation of symbols]

11: Semiconductor chip, 12: Lead frame, 13: Fine metal wire (wire), 14: Bonding tool, 15: Transducer horn, 16: Bonding head, 17: XY table, 18: TV camera for recognition, 19: Image processing unit , 20 display, 21 control unit, 22 operation unit, 23 electrode pad, 24 display screen, 25 virtual bonding target position, 26
... Cross line, 27 ... Indentation, 31 ... Operation unit, 32 ... Data memory (A), 33 ... Data memory (B), 34 ... Offset data memory, 35 ... Operation processing unit, 36 ... Operation control unit, 41 ...
Reference image memory (A), 42... Reference image memory (B), 43
.. A / D converter, 44 image memory, 45 correlator, 46 arithmetic processing unit.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/60 301

Claims (2)

(57) [Claims] 1. A wire bonding means using an ultrasonic wave, a parameter used for controlling the wire bonding means and controlling a normal bonding operation, and a dummy bonding for forming an indentation on a surface to be bonded. Used to control the operation and above normal bond
Parameters used to control the
And a bonding control means provided with a parameter holding unit for holding a load, an ultrasonic output, and a parameter for increasing a bonding time . 2. A wire bonding means having a bonding tool using an ultrasonic wave, a parameter used for controlling the wire bonding means and controlling a normal bonding operation, and an indentation on a surface to be bonded. It is used to control the dummy bonding operation of forming, the normal bonderizing
Parameters used to control the
A parameter holding unit for holding a load, an ultrasonic output, and a parameter for increasing a bonding time, and a center of the bonding tool and a recognition center thereof are offset from each other, and the wire bonding is performed. means
Uptake and imaging means for capturing image information of the bonding surface to be more bonding indentations formed during dummy bonding performed by the wire bonding means as image information by the imaging means, the based on the image information A control unit for calculating a shift amount from a target position of the dummy bonding by obtaining a center coordinate of the indentation, and correcting an offset amount between a center of the bonding tool and a recognition center of the imaging unit based on the shift amount. A wire bonding apparatus, comprising: