JP3008745B2 - Wire bonding inspection method and wire bonding inspection device - 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 inspection method and a wire bonding inspection apparatus, and more particularly, to a method for automatically measuring the shape and position of a wire after wire bonding, automatically correcting coordinate setting data of the apparatus, and achieving high precision. This makes it possible to perform a simple detection.

[0002]

2. Description of the Related Art Recently, products of semiconductor devices such as ICs and LSIs have been increasingly integrated year by year.

[0003] In particular, in the manufacturing process of the semiconductor circuit itself, that is, in the so-called pre-process, automation technology has been largely adopted, and unmanned processes have been advanced.

On the other hand, automation of a wire bonder has been attempted even in a wire bonding process which is a subsequent process. On the other hand, at present, the inspection exclusively relies on visual inspection.

For example, Japanese Patent Application Laid-Open No. 4-259807 proposes an image input device for inspecting a linear object in which three-dimensional image data of a bonding wire is obtained and the appearance of the bonding wire is visually inspected from the data. I have.

In this publication, a procedure is followed in which an operator analyzes image data obtained by a pair of cameras and corrects a set value of a wire bonder to continue manufacturing.

FIG. 6 is a schematic view of a main part of a conventional wire bonding inspection apparatus. In FIG. 1, reference numeral 13 denotes a ring illuminator, and 14 denotes an epi-illumination illuminator. Reference numeral 15 denotes an imaging device which images the semiconductor chip 1. Each of the elements 13, 14, 15 constitutes an imaging unit 15a. 1
Reference numeral 1 denotes an XYZ stage, which drives the imaging unit 15a based on a signal from the stage controller 24.

The semiconductor chip 1 to be measured is transported to the inspection area by the transport device 12 based on a signal from the transport control device 21. Thereafter, the imaging device 15 is moved to a position where a first bond portion (hereinafter, referred to as a “ball portion”) is present, focused, and an image of the ball portion is captured.

Although the image at this time includes the balls 3 and the electrode pads 4 as shown in FIG. 2, for example, the outer dimensions and the center coordinates of only the balls are calculated by the image processing device 23.

Subsequently, the imaging device 15 is moved to a position where a second bond portion (for example, hereinafter referred to as a "crescent portion") is present, and an image of the crescent portion is captured like the ball portion.

FIG. 5 is an explanatory diagram of the image captured by the crescent portion at this time. In FIG. 5, 2 is a wire, 6 is a crescent, 7 is a capillary dent, and 8 is a lead.

In the measurement of the crescent portion, the width, length and center coordinates of the crescent 6 in FIG. Furthermore, bend / spacing of wire part 2
The measurement of the height and the like is performed sequentially using a means such as image processing.

The measurement result obtained as described above is compared with a previously input reference value by the central processing unit 31 to judge the quality of the bonding state.

[0014]

FIG. 3 is a cross-sectional view of a main part when a ball portion is formed. In the figure, a ball 3 is formed by pressing a spherical portion at the end of a gold wire onto a semiconductor chip 1 by a capillary 5. At this time, the hole diameter of the capillary 5 is larger than the diameter of the wire 2. Therefore, the center of the capillary 5 and the center of the wire 2 are displaced by several μm. Further, since the ball 3 is eccentric with respect to the wire 2, there is a problem that a displacement of several tens μm occurs between the center of the ball 3 and the center of the capillary 5.

Also, in the crescent portion, as shown in FIG. 5, a deviation of more than half of the outer diameter of the capillary 5 occurs at the center coordinate of the crescent 6 and the center of the capillary dent 7.

On the other hand, in the wire bonder, the control of the bonding coordinates is all performed by controlling the trajectory of the capillary 5. Therefore, there is a problem that it is very difficult to directly and accurately correct the position coordinate data of the wire bonder based on the position coordinates calculated by the conventional wire bonding inspection apparatus.

An object of the present invention is to provide a wire bonding inspection method and a wire bonding inspection apparatus capable of automatically and continuously performing a high-precision inspection of the appearance of a semiconductor chip after wire bonding without relying on an operator. And

[0018]

According to a wire bonding inspection method of the present invention, a semiconductor device after wire bonding is transported and fixed at a predetermined position by a transport device, and the semiconductor chip is illuminated with a light beam from an illuminating means. When image information of a chip is obtained from an image pickup device provided on a position-adjustable stage and a first bond portion and / or a second bond portion of the semiconductor chip is inspected by the image processing device from the image information, a ball portion or a crescent The position of the capillary dent and / or the dimensional information of the capillary dent is determined by adjusting the illumination method of the capillary dent formed on the portion, and the center position of the capillary dent is measured. It is characterized in that the shape and displacement of the wire after wire bonding are detected.

In particular, the central processing unit calculates the amount of deviation between the center position coordinates of the capillary dent on the ball portion or the crescent portion side obtained by the image processing device and the bonding coordinates stored in the wire bonder and stores the difference in the wire bonder. It is characterized in that the bonding coordinates thus set are automatically corrected.

A wire bonding inspection apparatus according to the present invention includes a transfer device for transferring and fixing a semiconductor chip after wire bonding, an illuminating device for irradiating the semiconductor chip with a variable irradiation direction, and an apparatus for obtaining image information of the semiconductor chip. XYZ
Imaging device movable in the direction, from the image information obtained by the imaging device, from the position and dimensional information of the capillary dent formed in the ball portion or the crescent portion in the first bond portion and / or the second bond portion of the semiconductor chip. The image processing device for determining the center position, and calculating the amount of deviation between the bonding coordinates stored in the wire bond and the center position coordinates of the capillary dent obtained by the image processing device,
It is characterized in that the shape and positional deviation of the wire after bonding are automatically measured using a central processing unit that automatically corrects the bonding coordinates stored in the wire bond.

[0021]

FIG. 1 is a schematic view of a main part of a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a semiconductor chip to be inspected after wire bonding. 13 is a ring illumination device for illuminating the semiconductor chip 1, 14 is an epi-illumination device for illuminating the semiconductor chip 1, 15 is an imaging device for capturing an image of the semiconductor chip 1, and 11 is an XYZ stage. The device 15 is positioned relatively to the semiconductor chip 1. Reference numeral 12 denotes a transport device which transports and fixes the test object 1. 23 is an image processing device,
The image signal captured by the imaging device 15 is analyzed.

Reference numeral 21 denotes a transfer control device, and the transfer device 12
Drive control. Reference numeral 22 denotes an illumination control device, which drives and controls the ring illumination device 13 and the epi-illumination device 14 to perform ring illumination or epi-illumination on the semiconductor chip 1. Reference numeral 24 denotes a stage control device which drives and controls the XYZ stage 11. Reference numeral 32 denotes a wire bonder, which inputs position coordinates of a bond portion and a crescent portion to be connected from the outside. Reference numeral 31 denotes a central processing unit, which determines the quality of the test object 1 and corrects data of the wire bonder 32. 33 is an external input device.

In general, the ball portion is formed by the tip of the capillary 5 as shown in FIG.
And a ring-shaped flat portion (or concave portion) is formed on the upper surface of the ball portion.

According to the present embodiment, at the time of ball measurement, a capillary dent formed on the ball is extracted by image processing after measuring the position and external dimensions of the ball portion.
The actual position of the capillary at the time of bonding is detected by analyzing and calculating the coordinates of the center position of the capillary dent.

Even when the crescent portion is formed, a capillary dent 7 is formed on the lead 8 as shown in FIG.
When measuring the crescent part 6, the position of the crescent part
After measuring the external dimensions, the center position coordinates of the capillary dent 7 are extracted and analyzed by image processing, the center position coordinates of the capillary dent are calculated, and the actual position of the capillary at the time of bonding is detected. I have to.

The amount of deviation between the coordinates obtained by the above processing and the reference coordinates to which bonding should be originally performed, for example, the center coordinate of the electrode pad 4, is calculated, and the amount of deviation is used as a correction value for the wire bonder. The stored bonding coordinates are automatically corrected.

Next, the measurement procedure of this embodiment will be described with reference to FIGS.
This will be described with reference to the flowchart of FIG.

First, a pre-stored measurement condition is selected (step ST11), and then a lead frame on which the semiconductor chip 1 as a test object is mounted is set on the transfer device 12 (step ST12).

Subsequently, a command from the external input device 33 or a signal for starting measurement from the wire bonder 32 is transmitted to the central processing unit 31.
(Step ST13), the semiconductor chip 1 after the wire bonding, which is the test object, is carried to the inspection area by the transfer device 12 (step ST21) and fixed.

Subsequently, the illumination device 13 or 14 irradiates the semiconductor chip 11 with light (step ST22), and moves the image pickup device 15 to a preset position for focusing. "
And the positioning error including the rotation direction of the semiconductor chip 1 is corrected.

Further, at least three or more points on the semiconductor chip 1 are subjected to auto-focusing, and a three-dimensional tilt component is also corrected based on the height at that time (step ST23). Here, the lighting device is turned on after the semiconductor chip 1 is fixed. However, the lighting timing may be any time before the image is captured.

Next, the imaging device 15 is moved to a position where an image of the first ball portion of the bonding wire to be inspected can be taken in and focused (step ST3).
1). At this time, an image as shown in FIG. This image is taken into the image processing device 23, and only the ball portion 3 is extracted and measured from the image. Further, the position coordinates of the stage are called from the stage control device 24, and the position coordinates of the ball 3 are calculated by the central processing device 31. (Step ST32).

Here, the state when the ball portion 3 is formed will be described. As described above, the ball portion 3 is pressed onto the semiconductor chip 1 by the tip of the capillary 5 as shown in FIG. A ring-shaped flat portion (or concave portion) is formed on the upper surface of the ball portion 3.

Therefore, when the illumination for the ball portion 3 is only epi-illumination, or when the vertical component of the illumination light is increased (step ST33), the light reflected from the flat portion causes a ring-shaped bright light as shown in FIG. Part 9 appears. This image is taken into the image processing device 23 again, and only the ring portion 9 is extracted and measured in the same manner as the ball, and the center coordinates are calculated (step ST34).

Further, the imaging device 15 is moved to a position where an image of the first crescent portion 6 of the bonding wire to be inspected can be taken in and focused (step S).
T35). However, if the central processing unit 31 determines whether or not the ball unit 3 and the crescent 6 are within the same screen, and it is determined that the ball unit 3 and the crescent 6 are within the same screen, there is no need to move the imaging device 15.

FIG. 5 is a schematic view of an image captured by the crescent portion 6. As shown in the drawing, also in the crescent portion 6, similarly to the above-mentioned ball portion 3, the capillary dent 7 is formed. Appears in. After capturing this image, only the ring portion is extracted and measured in the same manner as the ball, and the center coordinates are calculated (step S).
T36).

Further, the image pickup device 15 is placed at the measurement position of the wire section 2.
Is moved (step ST37) to capture an image and measure the wire section 2 (step ST38). For the measurement of the wire portion 2, for example, a measuring method proposed in Japanese Patent Application Laid-Open No. Hei 5-18722 can be applied.

Steps ST31 to ST3 described above
8 is automatically repeated for all the inspection target wires of the semiconductor chip 1, and the obtained measurement result is compared with a reference value set in the central processing unit 31 in advance to make a pass / fail judgment (step ST41). .

Generally, a plurality of semiconductor chips are mounted on one lead frame. If it is necessary to measure the semiconductor chips next, steps ST21 to ST21 are performed.
A series of processing up to 41 is repeated.

Thereafter, the central processing unit 31 performs the wire bonding process on the semiconductor chip 1 by wire bonding.
2, the bonding coordinates stored in the wire bonder 32 are input via the communication means 34. The deviation calculated for the bonding coordinates in step ST41 is calculated as a correction amount, and the corrected value is transferred as new bonding coordinates to the wire bonder 32 via the communication means 34 and stored (step ST51).
Prepare for the next wire bonding.

Finally, the lead frame for which inspection has been completed is ejected from the inspection area by the transfer device 12 (step ST).
52), all processing ends;

In this embodiment, the following procedure can be partially changed.

(1-1) In the description of the first embodiment, step S
Ball part, crescent part, as shown in T31-38,
Although the measurement is performed in the order of the wire portions, the measurement order may be changed. Further, the measurement of the next wire portion is performed after all the items are measured for one wire portion. For example, a procedure in which the entire wire portion is inspected for only the ball portion and then the crescent portion is inspected. You may take it.

(1-2) In the first embodiment, the case where only one wire portion to be inspected is present in the image obtained by the imaging device 15 has been described. In many cases, the wire portion is captured on the same screen.

Therefore, when the position of the imaging device 15 is determined in step ST31 in FIG. 7, the coordinates of the wire portion to be inspected are all checked in the central processing unit 31, and the number of wires captured on the same screen is the maximum. Then, the position of the imaging device 15 is determined.

Further, for the measurement of the wire portion in the image obtained in this way, the processing in the image processing device 23 may be parallelized. According to this, it is possible to measure an increase in speed and efficiency.

(1-3) Steps ST34 and ST in FIG.
In FIG. 36, the shape of the capillary dent 7 formed on the ball 3 or the lead frame 8 in FIGS. 4 and 5 is described as being a ring shape. In some cases, about ２ of them are not formed partially or cannot be recognized.

In such a case, by registering the diameter of the capillary in the central processing unit 31 or the image processing unit 23 in advance, a circular figure corresponding to the capillary diameter is selected from the captured image, and An algorithm for obtaining the center coordinates of the figure may be used together. According to this, accuracy can be improved.

[0050]

According to the present invention, by setting each element as described above, the appearance inspection of a semiconductor chip after wire bonding can be performed automatically and continuously with high precision without relying on an operator. A wire bonding inspection method and a wire bonding inspection device that can be realized.

In particular, according to the present invention, the appearance inspection of the semiconductor chip after wire bonding can be performed automatically and continuously, and there is no individual difference as seen in the visual inspection, and the positions of the ball and the crescent are not changed. Since it is managed by the capillary center coordinates, there is an effect that the deviation amount from the reference value can be used as it is as the correction value of the bonding coordinates of the wire bonder.

Further, since the coordinate correction of the wire bonder is also performed automatically, there is an effect that the bonding can be continued in a good state without relying on the operator's hand.

[Brief description of the drawings]

FIG. 1 is a schematic view of a main part of a wire bonding inspection apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a ball portion captured image in a conventional measurement.

FIG. 3 is a sectional view when a ball portion is formed.

FIG. 4 is an explanatory diagram of a ball portion captured image according to the present invention.

FIG. 5 is an explanatory diagram of a captured image when measuring a crescent portion.

FIG. 6 is a schematic view of a main part of a conventional wire bonding inspection apparatus.

FIG. 7 is a flowchart of a measurement procedure according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor chip 2 Wire 3 Ball 4 Electrode pad 5 Capillary 6 Crescent 7 Capillary dent 8 Lead 9 Ring-shaped bright part 11 XYZ stage 12 Transport device 13 Ring illumination 14 Epi-illumination 15 Imaging device 21 Transport control device 22 Lighting control device 23 Image Processing device 24 Stage control device 31 Central processing device 32 Wire bonder 33 External input device

Continuation of the front page (72) Inventor Hidetoshi Nishigun 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masato Nakura 3-30-2, Shimomaruko 3-chome, Ota-ku, Tokyo Canon Inc. (56) reference Patent flat 5-18722 (JP, a) JP Akira 60-167340 (JP, a) JP Akira 51-120176 (JP, a) (58 ) investigated the field (Int.Cl. ⁷ G01B 11/00-11/30 102 G01N 21/84-21/91 G06T 7/00 H01L 21/64-21/66

Claims (3)

(57) [Claims] The semiconductor chip after wire bonding is transported and fixed at a predetermined position by a transport device, the semiconductor chip is illuminated with a light beam from an illuminating means, and image information of the semiconductor chip is provided on a stage capable of position adjustment. When the first bond portion and / or the second bond portion of the semiconductor chip is inspected by the image processing device obtained from the image pickup device using the image information, the illumination of the capillary dent formed on the ball portion or the crescent portion is performed. By adjusting the illumination method from the means, obtaining the position or / and dimensional information of the capillary dent, measuring the center position of the capillary dent and detecting the shape and displacement of the wire after wire bonding A wire bonding inspection method. 2. A central processing unit calculates a deviation amount between a center position coordinate of a capillary dent on a ball portion or a crescent portion obtained by the image processing device and a bonding coordinate stored in the wire bonder, and stores the deviation amount in the wire bonder. 2. The wire bonding inspection method according to claim 1, wherein said bonding coordinates are automatically corrected. A transport device for transporting and fixing the semiconductor chip after wire bonding, a lighting device for illuminating the semiconductor chip with a variable irradiation direction, an imaging device movable in XYZ directions to obtain image information of the semiconductor chip, An image processing device for obtaining a position of a capillary dent formed on a ball portion or a crescent portion in a first bond portion and / or a second bond portion of the semiconductor chip from image information obtained by the imaging device, and a center position thereof from dimensional information; And a central processing unit that calculates an amount of deviation between the bonding coordinates stored in the wire bond and the center position coordinates of the capillary dent obtained by the image processing apparatus, and automatically corrects the bonding coordinates stored in the wire bond. Characterized in that the wire shape and displacement after bonding are automatically measured using Inspection equipment.