JPH01134953A - Detection for bump electrode plating end point - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] Regarding a new method for detecting the end point of bump electrode plating, the purpose is to detect a constant plating amount with good reproducibility. In the bump electrode plating step of coating the semiconductor wafer with a resist film and forming a bump electrode made of a plating layer on the electrode portion, a laser beam is irradiated from one end of the semiconductor wafer in parallel to the semiconductor wafer surface on which the plating layer will grow, and the semiconductor wafer is At the other end of the wafer, observe changes in the amount of transmitted light as the plating layer grows, or by irradiating a laser beam from one end of the semiconductor wafer parallel to the surface of the semiconductor unihull on which the plating layer grows, and The method is characterized in that the end point of plating the hump electrode is determined by observing changes in the amount of reflected light as the SJI gold layer grows.

[Industrial Application Field] The present invention relates to a novel method for detecting the end point of bump electrode plating. .

Recently, ICs (integrated circuits) with bump electrodes have been used extensively, and they do not require wire bonding (the thickness of the package can be reduced, which makes the package flat, making it easier to create IC cards. This is because there are advantages such as ease of use.

However, in order to create such bump electrodes, plating (
The formation of a plating layer is essential, and controlling the amount of plating is a particularly important issue for improving quality.

[Prior art and problems to be solved by the invention] FIG. 4 shows a cross-sectional view of a bump electrode, and 1 is a semiconductor substrate (
part of a semiconductor wafer), 2 is an aluminum electrode film, 3
4 is a barrier metal film, 4 is an insulating film, and 5 is a plating layer. That is, a plating layer made of half metal or gold is formed on the aluminum electrode film via a barrier metal film, and the plating layer 5 is made to protrude in a convex shape, and this is called a bump electrode B.
This structure allows wireless bonding by connecting this bump electrode to the other electrode by adhering it.

In wireless ■C, many such bump electrodes are provided around the chip periphery, similar to wire bonding electrodes, and when bump electrodes are provided, the electrodes are provided not only at the chip periphery but also at the chip center. This makes it possible to reduce wiring and contribute to higher integration of ICs.

The following Figure 5 shows a diagram in the process of forming a solder bump electrode among the bump electrodes.To explain the method of forming a solder bump while referring to the figure, first, an aluminum electrode film 2 is placed on a semiconductor substrate 1. is formed, an insulating film 4 is deposited thereon to open an electrode window, and a Ti/(:u/Ni barrier metal film 3 is vapor-deposited on top of it. A resist film pattern 6 is then provided on top of it, and an aluminum A window is opened only in the electrode film 2 portion, and a solder plating layer 5 is grown on the window portion by a plating method,
The plating layer 5 is grown in the shape of a pine mushroom with a height of 60 to 80 μm.

FIG. 6 is a schematic cross-sectional view of the plating apparatus, in which 11 is a semiconductor wafer, 12 is a plating container, and 13 is a cathode pin.

Reference numeral 14 denotes a mesh-like anode, and the plating solution is placed in a plating container for the semiconductor wafer 11, which is pressed from the back side with the surface of the semiconductor wafer 11 on which the plating layer is grown facing downward and brought into contact with the cathode pins at several points on the surface. The jet flows from the bottom to the top and contacts the semiconductor wafer 11, and the bump electrode B
Electrolytic plating is performed to grow a plating layer. and,
After the plating liquid comes into contact with the semiconductor wafer 11, it falls from around the top end of the plating container and is circulated.

After that, the resist film pattern 6 shown in FIG. 4 is removed, the exposed excess barrier metal film 3 is removed, and then the solder plating layer 5 is reflowed (melted) by heating.
let Then, without being welded to the insulating film 4, the solder swells due to its own surface tension (as shown by the dotted line), and a bump electrode made of a solder plating layer as shown in FIG. 3 is completed. The height of the convex portion of this solder plating layer is about 150 microns.

By the way, the problem here is the constant height of the bump electrode, which is determined by the amount of plating in the plating layer. Conventionally, this plating layer was difficult to measure because it was in the plating solution, and adjustment of the plating amount depended on the plating time. However, since the plating area (number of electrodes), plating current, plating quality, etc. are complicated, it is difficult to make the amount of noodles uniform just by regulating the plating processing time.

The present invention proposes a bump electrode plating end point detection method for the purpose of making the plating amount constant.

[Means for Solving the Problems] The purpose is to irradiate a laser beam from one end of the semiconductor wafer parallel to the surface of the semiconductor wafer on which the plating layer grows, and to irradiate laser light parallel to the surface of the semiconductor wafer on which the plating layer grows at the other end of the semiconductor wafer. Observe the change in the amount of transmitted light, or irradiate a laser beam from one end of the semiconductor wafer parallel to the semiconductor wafer surface on which the plating layer grows, and change the amount of reflected light as the plating layer grows on the front surface of the semiconductor wafer. This is achieved by a bump electrode plating end point detection method that determines the end point of plating on bump electrodes by observing the amount of plating.

[In other words, the present invention detects the plating end point by irradiating a laser beam into the plating solution.The laser beam is irradiated from one end of the semiconductor wafer parallel to the surface on which the plating layer will grow, and the plating solution is irradiated from one end of the semiconductor wafer. The end point of plating the bump electrode is determined by observing changes in the amount of transmitted light as the layer grows, or by observing changes in the amount of reflected light as the plating layer grows on the front surface of the semiconductor wafer.

In this case, the plating height, that is, the plating amount, can be directly observed, and the plating amount can be controlled more accurately than the conventional method of regulating the plating time, and the IC provided with bump electrodes can be made more reliable.

[Example] Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram of a plating apparatus showing a plating method according to the present invention, in which (al is a plan view, and (bl is a cross-section taken along the line AA'' in FIG. 6(a). Identical parts have the same symbols, and 21 is a laser beam oscillator.

Reference numeral 22 denotes a laser light detector. The laser light oscillator 21 is attached to the upper part of the plating container 12, and the laser light detector 22 is provided above the other end of the plating container 12 facing the laser light oscillator. This laser beam has a short optical wavelength and is easily transmitted through the plating liquid and observed.

In this way, the laser beam L from the laser beam oscillator 21 is irradiated very close to the wafer surface from one end of the semiconductor wafer 11 in parallel to the wafer surface, and the laser beam L is irradiated from one end of the semiconductor wafer 11 in parallel to the wafer surface, and the laser beam L is irradiated from one end of the semiconductor wafer 11 in parallel to the wafer surface. Detects light intensity. Then, the transmitted light of the laser beam irradiated from the laser beam oscillator 21 is blocked as the bump electrode B grows, and the amount of light received by the laser beam detector 22 gradually decreases. In this way, a reference value for the amount of light received by the laser photodetector relative to the amount of light irradiated by the laser beam oscillator is determined in advance, and the time when the reference value is reached is determined as the plating end point.

Figure 2 is a diagram showing the relative position between the laser beam and the bump electrode. For example, bump electrode B gradually grows (indicated by a dotted line) and the laser beam L is completely blocked by the bump electrode B, allowing the laser beam to be detected. The time when the amount of light received by the device becomes zero is the end point of the plating.

The height of the bump electrode B is 60 to 80 μm, and the beam diameter of the laser beam can be adjusted to about 10 to 20 μm. Therefore, by adjusting the placement positions of the laser beam oscillator 21 and the laser beam detector 22, the laser beam can be adjusted. Transmission is possible at the positions shown.

In addition, as in the embodiment shown in Fig. 2, even if the reference value of the amount of light received by the laser light detector is determined as described above without detecting the point that is completely shielded, and the plating end point is managed using that value, good.

In addition to the method of observing the decrease in the field of view of the laser light detector 22 due to the growth of the bump electrode B described above, when the laser beam hits the bump electrode as the bump electrode B grows, the laser light is diffusely reflected. Therefore, changes in the amount of light may be observed. In this second embodiment, for example,
The laser beam detector 22'' is placed at the position shown in Fig. 1 (indicated by the dotted line) for observation. Fig. 3 shows the relative position between the laser beam and the bump electrode in this second embodiment. This indicates that the diffusely reflected light increases due to the growth of the bump electrode B. Then, the increase in the light intensity of the laser light detector 22' is detected and determined as the end point of plating.

Furthermore, it is also possible to adopt a method in which the two laser light detectors 22 and 22' are installed together, and both the transmitted light and reflected light are measured and processed by a calculation processing system to detect the end point.

According to the above plating end point detection method, the plating height of the bump electrode can be directly detected, the plating amount can be adjusted with high precision,
The height of the bump electrode becomes constant.

By doing so, the strength of the electrode connection becomes constant and reliability of the IC can be improved.

Note that this method can naturally be applied to bump electrodes made of gold or the like other than solder bump electrodes.

[Effects of the Invention] As is clear from the above explanation, according to the present invention, the amount of plating on bump electrodes is well controlled and the quality is improved, which has a great effect on improving the reliability of ICs provided with bump electrodes. It is.

[Brief explanation of the drawing]

1(a) and 1(b) are schematic diagrams of a plating apparatus showing the plating method according to the present invention, FIG. 2 is a diagram showing the relative position of the laser beam and the bump electrode, and FIG. Figure 4 is a cross-sectional view of the bump electrode, Figure 5 is a diagram showing the process of forming the solder bump electrode, and Figure 6 is a cross-sectional schematic diagram of the plating device. be. In the figure, ■ is a semiconductor substrate (part of a semiconductor wafer), 11 is a semiconductor wafer, 12 is a plating container, 13 is a cathode pin, 14 is an anode, 21 is a laser beam oscillator, 22 is a laser beam detector, and B is a bump. Electrode, L is the laser beam, (b) AA' cross-section unexploded glll key sound Ota 9 end T light lead bomotosei is the country's first
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Claims (1)

[Claims] A semiconductor in which a plating layer is grown from one end of the semiconductor wafer in a bump electrode plating process in which an electrode part on the surface of the semiconductor wafer is exposed and the other part is covered with a resist film, and a bump electrode made of a plating layer is formed on the electrode part. Either irradiate a laser beam parallel to the wafer surface and observe the change in the amount of transmitted light as the plating layer grows at the other end of the semiconductor wafer, or A bump electrode plating end point characterized in that the end point of bump electrode plating is determined by irradiating laser light in parallel and observing changes in the amount of reflected light as the plating layer grows on the front surface of the semiconductor wafer. Detection method.