JPH07254603A - Inspection system for bump electrode - Google Patents

Abstract

PURPOSE:To realize an efficient inspection of bump electrode in which the bonding properties are ensured previously in the flip chip bonding of a bump electrode. CONSTITUTION:A half mirror 13 is disposed under an optical fiber plate 11 and a light source 12 is disposed under the half mirror 13. A CCD camera 14 is disposed on the side of the half mirror 13 while focusing on the rear surface of the optical fiber plate 11. A chip 1 to be inspected is mounted, while facing downward, on the surface of the optical, fiber plate 11 and irradiated with light introduced from the rear surface side. The CCD camera 14 picks up the optical image of a bump electrode, formed on the surface of the chip 1, reflected on the rear surface of the optical fiber plate 11. The bump electrode is then checked for abnormality, e.g. insufficient height or surface oxidation, based on the displayed image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting bump electrodes such as semiconductor chips having bump electrodes formed on the surface thereof.

In recent years, as a mounting method for semiconductor devices,
Flip chip bonding has been put to practical use. In this method, the surface electrodes of a semiconductor chip are formed with fine bumps such as solder, and the semiconductor chip is bonded face down to a wiring board or the like, and extremely high-density mounting is possible. However, if many bump electrodes have uneven heights, the bonding may be incomplete, and it is difficult to visually check after bonding. Is guaranteed.

[0003]

2. Description of the Related Art In flip chip bonding, if the bump electrodes have different heights, the bonding of bump electrodes having a relatively low height may become uncertain, so that the reliability of the bonding is guaranteed before bonding. In order to do so, it is necessary to inspect the height of the bump electrode. As a conventional example of a device for inspecting the height of bump electrodes, a chip is mounted on an XY stage and the height of each bump electrode is measured one by one by a light cutting method or an autofocus method. The chip is scanned linearly and the reflected light is reflected by PSD (Po
sition Sensitive Detector) is used to calculate the height by receiving light. Hereinafter, the latter example will be described with reference to the drawings.

FIG. 6 is a block diagram of a conventional device. In the figure, 1 is a chip as an object, 2 is a bump electrode to be inspected, 41 is a laser light source, 42 is a collimator lens, 43 and 46 are optical path changing mirrors, and 44 is a polygon mirror for scanning laser light. , 45 is a scan lens, 47
Is an imaging lens, and 48 is a PSD.

The chip 1 is, for example, an LSI chip, and a large number of fine bump electrodes 2 are formed in a matrix on the surface. The chip 1 is placed on a stage (not shown), and while moving the stage, the laser beam emitted from the laser light source 41 and oscillated by the rotating polygon mirror 44 is linearly scanned with respect to the chip 1. , The reflected light is received by the PSD 48, the position of the regular reflected light is detected, the height of each bump electrode 2 is calculated from the output signal, and the quality is determined.

[0006]

However, such a conventional device has a problem that the inspection requires an extremely long time in the former case, and in the latter case, the height of the bump electrode depends on the surface condition. There is a problem that the inspection result does not always guarantee the bondability of the bump electrode because the measurement accuracy is significantly reduced.

The present invention solves such a problem and efficiently conducts an inspection capable of guaranteeing the certainty of bonding in a flip chip bonding of a chip having bump electrodes formed on the surface before bonding. It is an object of the present invention to provide a bump electrode inspection device capable of performing the above.

[0008]

According to the present invention, there is provided an illuminating means, an optical fiber plate and a reflected light observing means, the illuminating means being face down on the upper surface side of the optical fiber plate. A bump electrode inspecting device, characterized in that the bump electrode of the chip mounted on the substrate is irradiated with illumination light from the lower surface side of the optical fiber plate, and the reflected light observation means receives the reflected light from the bump electrode. It will be achieved.

[0009]

The operation of the present invention will be described with reference to FIG.
In the figure, 1 is a chip as an object, 2 is a bump electrode to be inspected, and 11 is an optical fiber plate.
The optical fiber plate 11 is a plate in which thin optical fibers are densely bundled and fixed without changing the arrangement, and cut into a plate shape, and an image projected on one end surface is transmitted and reproduced on the other end surface. .

When the chip 1 is placed on the upper surface of the optical fiber plate 11 and the bump electrodes 2 are brought into contact with each other (or held at a minute interval), and illumination light is introduced from the lower surface side, it is reflected by the upper bump electrode 2. And return to the bottom side. In general, the light traveling in the optical fiber is diffused when it is emitted from the end face thereof, so that the reflected light becomes weak if the bump electrode 2 is away from the upper surface of the optical fiber plate 11. Moreover, as the distance increases, the amount of reflected light sharply decreases. Therefore, the bump electrode 2
When the heights of the light sources vary, the amount of reflected light varies.
On the other hand, since the reflectance is low when the surface of the bump electrode 2 is oxidized, the reflected light becomes weak in this case as well.

As a result, by observing the image of the bump electrode 2 on the lower surface of the optical fiber plate 11, it is possible to simultaneously check the bump electrode 2 having a relatively small height and the bump electrode 2 whose surface is oxidized. Can be done. Even if the height of the bump electrode 2 is relatively small, or the surface is oxidized, the reliability of bonding deteriorates. Therefore, in the inspection of the bump electrode by the inspection apparatus according to the present invention, bonding before bonding is performed. The certainty of can be efficiently guaranteed.

[0012]

EXAMPLE An example of a bump electrode inspection apparatus according to the present invention will be described with reference to FIGS.

FIG. 2 is a block diagram of the apparatus of the first embodiment of the present invention. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals. 1 is a chip, 2 is a bump electrode, 11 is an optical fiber plate, 12 is a light source, 13 is a half mirror, 1
4 is a CCD camera.

The chip 1 is, for example, an LSI chip, and a large number of fine bump electrodes 2 are formed in a matrix on the surface. This bump electrode 2 is made of solder or the like,
After the chips are formed on the surface of the chip 1, the height is made uniform by pressing all of them on one plane, so that the normal tips of the bump electrodes 2 are flat.

A half mirror 13 is arranged below the optical fiber plate 11, and a light source 12 is arranged below it.
A CCD camera 14 focused on the lower surface of the optical fiber plate 11 is arranged beside the half mirror 13.

The chip 1 is placed face down directly on the upper surface of the optical fiber plate 11, or a chip holder (so that a minute gap is formed between the bump electrode 2 having a normal height and the optical fiber plate 11). (Not shown), the illumination light from the light source 12 is introduced from the lower surface side of the optical fiber plate 11 to irradiate all the bump electrodes 2 of the chip 1. Optical fiber plate 11 for the reflected light
The CCD camera 14 takes an image of the lower surface and displays it on a display device (not shown) such as a CRT. The image is used to check for abnormalities such as insufficient height of bump electrodes 2 and surface oxidation.

FIG. 3 is a block diagram of the apparatus of the second embodiment of the present invention. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals. 1 is a chip, 2 is a bump electrode, 11 is an optical fiber plate, 21 is a laser light source, 22 is a half mirror, 23 is an optical path changing mirror, 24 is a polygon mirror for laser light scanning, 25 is a scan lens, and 26 is A photodetector (eg, photomultiplier tube).

Also in this apparatus, the chip 1 is directly placed face down on the upper surface of the optical fiber plate 11, or the bump electrode 2 and the optical fiber plate 1 having a normal height are mounted.
It is held by a chip holder (not shown) so that a minute gap is created between the tip holder and the holder 1. The optical fiber plate 11 is moved in a linear direction within a horizontal plane by a moving mechanism (not shown).

The laser beam emitted from the laser light source 21 is swung by the rotating polygon mirror 24, enters from the lower surface side of the optical fiber plate 11 via the scan lens 25, and linearly scans the chip 1. This scanning is repeated while moving the optical fiber plate 11 in the direction perpendicular to the scanning direction. The reflected light is received by the photodetector 26, the output signal thereof is processed by an image processing device (not shown) and displayed on a display device (not shown), or
Alternatively, the quality is automatically determined.

FIG. 5 shows an example of an image after the above image processing.
In the figure, (A) shows a normal bump electrode, (B) a bump electrode is missing, (C) is an under bump electrode, (D) is a bump electrode displacement, and (E) is an insufficient bump electrode height or Surface oxidation,
Are shown respectively.

FIG. 4 is a block diagram of an apparatus according to the third embodiment of the present invention. In the figure, the same components as those in FIG. 3 are designated by the same reference numerals. 1 is a chip, 2 is a bump electrode, 11 is an optical fiber plate, 21 is a laser light source, 22 is a half mirror, 25 is a scan lens, 26 is a photodetector (for example, a photomultiplier tube), and 31 and 32 are galvanomirrors. is there. In this device, two galvanometer mirrors 3 are used as scanning means.
1 and 32 are used to scan the laser beam in both X and Y directions. Therefore, there is no moving mechanism for moving the optical fiber plate 11. Others are the same as those in the second embodiment.

The optical fiber plate 11 in the above-mentioned first to third embodiments is usually made of an optical fiber whose thickness does not change, that is, one having the same upper surface area and lower surface area. It is possible to use an optical fiber, that is, an optical fiber having different top and bottom areas. The image of the reflected light is enlarged when an optical fiber plate whose lower surface is larger than the upper surface is used, and the image of the reflected light is reduced when an optical fiber plate whose lower surface is smaller than the upper surface is used. These are used properly according to the resolution.

It is also possible to prepare a plurality of optical fiber plates having different opening angles on the end faces, and use these properly according to the required image resolution. The present invention is not limited to the above embodiments, and can be implemented with various modifications. For example, the present invention is effective regardless of whether the chip 1 is before dicing, that is, in a wafer state, or other than a semiconductor chip.

[0024]

As described above, according to the present invention,
It is possible to provide a bump electrode inspection device capable of efficiently performing an inspection to ensure the reliability of bonding in a flip chip bonding of a chip having a bump electrode formed on the surface, and a yield in a mounting process. Contribute to improvement, etc.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a device configuration diagram of a first embodiment of the present invention.

FIG. 3 is a device configuration diagram of a second embodiment of the present invention.

FIG. 4 is a device configuration diagram of a third embodiment of the present invention.

FIG. 5 is a diagram showing an example of an image for quality judgment.

FIG. 6 is a device configuration diagram of a conventional example.

[Explanation of symbols]

 1 LSI Chip (Chip) 2 Bump Electrode 11 Optical Fiber Plate 12 Light Source (Illumination Means) 13 Half Mirror 14 CCD Camera (Reflected Light Observation Means) 21 Laser Light Source (Illumination Means) 22 Half Mirror 23 Mirror 24 Polygon Mirror (Scanning Means) 25 Scan Lens 26 Photo Detector (Reflected Light Observing Means) 31, 32 Galvano Mirror (Scanning Means) 41 Laser Light Source 42 Collimator Lens 43, 46 Mirror 44 Polygon Mirror 45 Scan Lens 47 Imaging Lens 48 PSD

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Fumiyuki Takahashi 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (1)

[Claims] 1. An apparatus for inspecting a bump electrode of a chip having a bump electrode formed on a surface thereof, comprising: illuminating means, an optical fiber plate, and reflected light observing means, the illuminating means The bump electrode of the chip mounted face down on the upper surface side of the fiber plate is illuminated with illumination light from the lower surface side of the optical fiber plate, and the reflected light observation means receives the reflected light from the bump electrode. Bump electrode inspection device.