JPH02280334A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To easily obtain a bump of high accuracy and high reliability by forming a protruding electrode of photosensitive resin mixed with conductive filler coated with transparent conductive substance on the surface of transparent bead of organic resin. CONSTITUTION:Transparent conductive filler 6 is applied to an Si substrate 1 having an electrode pad 2 and an insulating film 3. A conductive resin layer 7 is formed by spin coating of photosensitive bisazide resin and isopren rubber whose viscosity has been adjusted with solvent. After prebacing, it is radiated with a UV-ray through a glass mask 8, and it is developed. When the resin is negative type, a radiated position remains as an elastic bump 4. The filler 6 is coated with ITO6b on the surface of a transparent 6a made, for example, of styrene and divinylbenzene. According to the structure, since the bump is formed by a photolithography method, a forming cost and a time are reduced as compared with those at the time of plating, and since a composing member is resin, an elastic bump having excellent stress alleviation and high connecting reliability is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the structure of a semiconductor device (hereinafter referred to as IC) and its manufacturing method, and particularly relates to the structure of a protruding electrode (hereinafter referred to as bump) which is an external connection electrode. , relates to its manufacturing method and is mainly used in the semiconductor industry.

[Conventional technology and its issues]

A common method for electrically connecting IC chips and lead frames or circuit boards is so-called wire bonding, which connects fine wires made of gold, aluminum, copper, etc. using ultrasonic waves or thermocompression bonding. It is well known and is still mainstream today.

However, in recent years, in addition to compactness, thinness, and high density, which are typified by the words "light, thin, short, and small," which have been increasingly demanded, wire bonding costs account for the majority of mounting costs from the viewpoint of low cost. has become unsatisfactory with the times, and there is a need for the development of low-cost mounting technology suitable for high-density mounting.

Wireless bonding, in which various bumps are provided on the surface of an IC chip and the IC chip is directly mounted on a circuit board etc. via the bumps, has been proposed as a way to meet these demands, and technological development is progressing. Some of them have been put into practical use.

For example, in the flip-chip method, solder bumps are generally formed as external connection electrodes, aligned with the circuit board to be connected, and then connected by solder reflow by heating.

FIG. 5 is a cross-sectional view of an IC on which solder bumps are formed for conventional general flip-chip connection.

An electrode pad 2 made of aluminum is formed on a semiconductor substrate 1, an insulating film 6 formed on the electrode pad 2 is opened, and a solder bump 10 is further formed through a barrier layer 9 made of aluminum, chromium, and copper. It is.

FIG. 6 is a cross-sectional view of an IC connected by a conventional general flip-chip method, in which a conductive pattern 11 is formed on an insulating substrate 12 at a position corresponding to the connection with a solder bump on the IC, and a solder resist layer is formed. IC chip 1 is placed on the wiring board provided with 16
After positioning 6, heat the whole and reflow the solder to connect.

Another typical method is TAB (Tape).
There is an automated bonding method.

FIG. 7 is a cross-sectional view of a conventional general TAB type IC, in which a conductor pattern 11a is formed on an insulating substrate 12, and the wiring at the connection end with the IC chip is extended from the insulating substrate and tin-plated. After aligning the wiring board and the IC chip 16 on which the gold bumps 14 are formed, they are bonded by thermocompression using the heat tool 15 and connected by gold-tin eutectic.

Another technique, for example, is a method described in Japanese Patent Application Laid-Open No. 63-9942, in which an IC chip on which gold bumps are formed and a circuit board are pressure-connected by the shrinkage stress generated when the resin hardens. There is also.

These various methods described above are all characterized by connection via bumps made of metal such as solder, gold, or copper, but as is well known, metal bumps have high rigidity;
Since the stress relaxation effect is small, if stress is applied from the outside, it may cause a failure inside the IC chip, and may also cause problems at the connection portion with a circuit board or the like.

That is, it is a connection failure due to a disconnection inside the IC chip or electrical heating or peeling of the bump connection portion. Furthermore, the bump forming process is long, and the cost associated with this process is also a cause of increasing mounting costs, which is a problem that is desired to be improved.

In response to such requests, for example, Japanese Patent Application Laid-Open No. 58-38769
A proposal has been made to form bumps using a conductive elastic adhesive and connect them by screen printing, as disclosed in Japanese Patent Publication No. This conventional bump forming method has the advantage of shortening the process and making a connection that is resistant to external stresses such as vibrations. However, when forming bumps with a paste adhesive,
Since the screen printing method has a low resolution, the shape of the bumps formed is limited to conical or hemispherical shapes as the bump diameter becomes smaller, and the practical limit of the bump pitch is approximately 250 μm. there were.

That is, there is a problem that bumps cannot be formed because adjacent adhesives are short-circuited.

Therefore, for example, Japanese Patent Application Laid-Open No. 63-28
A proposal such as that described in Publication No. 3144 has been made.

This method involves disposing metal powder such as gold, palladium, rhodium, or gold-plated nickel on a photosensitive resin and forming it by a photolithography process.

However, conductive powder without light transmittance has the disadvantage that as the occupancy of the conductive powder in the resin increases, the resolution of photolithography decreases.

Furthermore, as the content of the conductive powder decreases, the resistance value of the bump itself increases, making it unsuitable for connection to the outside.

In other words, the irradiated ultraviolet light is blocked by the metal powder, and the chemical reaction of the resin does not proceed sufficiently in the area near the electrode band.
In addition to the problem that independent bumps cannot be formed,
The increase in mounting costs due to the use of precious metal powder as described above cannot be ignored. However, due to the need for high-density packaging, there is a demand for further micropitch, and a low-cost and highly reliable connection is required.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a semiconductor device having bumps that can form bumps without requiring many steps, have high dimensional accuracy, and excellent connection reliability, and a method for manufacturing the same. is the purpose.

[Means to solve the problem]

In order to achieve the above object, the bump of the present invention is formed by the structure and manufacturing method described below.

(a) After forming the element, an insulating film with openings corresponding to the electrode pads is formed on the semiconductor substrate on which electrode pads for connection with the outside are formed, and then the insulating film is In a semiconductor device in which a protruding electrode is formed for external connection, the protruding electrode is made of a photosensitive resin mixed with a conductive filler made by coating a transparent conductive substance on the surface of a transparent bead made of an organic resin. Features.

(b) A conductive resin layer made of a photosensitive resin mixed with a conductive filler coated with a transparent conductive material on the surface of transparent organic resin beads is applied to the entire surface of the insulating film with openings in the electrode pad area of the semiconductor substrate. and a step of patterning the conductive resin layer by photolithography to form elastic bumps.

[Effect]

According to the present invention, since the means for forming bumps is photolithography, conventional equipment such as plating or vapor deposition is not required, and the cost and time involved in forming bumps can be significantly reduced.

Furthermore, because the transparent conductive filler enables reliable exposure and development processing, and because the component is mainly resin, it is possible to form elastic bumps with high precision, excellent stress relaxation properties, and high connection reliability. becomes.

〔Example〕

Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a sectional view showing an embodiment of a semiconductor device according to the present invention.

An electrode pad 2a made of laminated aluminum and nickel is formed on a semiconductor substrate 1, and an elastic bump 4 made of a photosensitive resin 5 and a transparent conductive filler 6 is further formed with an insulating film 6 interposed therebetween.
was formed.

FIG. 2 is a sectional view showing an embodiment of the transparent conductive filler 6, which is a component of the elastic bump 4. Indium tin oxide (hereinafter referred to as ITO) is applied to the surface of the transparent resin sphere 6a made of styrene and divinylbenzene. ) is formed by depositing a transparent conductive material layer 6b.

This transparent conductive material layer 6b can be made of any transparent conductive material other than the above-mentioned ITO, such as tin oxide or chromium silicide.

The appropriate thickness of the transparent conductive material layer 6b is 0.1 μm to 0.3 μm, and if it is less than 0.1 μm, the connection resistance increases and the thickness is 0.1 μm to 0.3 μm.
If the thickness exceeds 3 μm, the resolution in the exposure and development steps will deteriorate due to a decrease in transparency.

This transparent conductive material layer 6b is obtained by immersing the transparent resin sphere 6a in a solution in which ultrafine particles of ITO are dispersed in a suitable solvent, drying it, and subjecting it to heat treatment.

Further, tin oxide can be formed using the same method, but chromium silicide can be formed by sputtering.

The size of the transparent resin sphere 6a is about 5 μm if the height of the bump to be formed is up to about 20 μm, and if the height of the bump is higher than that, good results can be obtained by using a size of about 10 μm. .

FIG. 3 shows the process of forming elastic bumps of the present invention on a semiconductor substrate (silicon wafer).

First, as shown in FIG. 3(a), 65% by weight of a transparent conductive filler 6 is placed on a semiconductor substrate 1 on which an electrode pad 2 and an insulating film 3 are formed, and a solvent is added to adjust the viscosity of imprene rubber and bisazide. A conductive resin layer 7 is formed by uniformly applying a photosensitive resin using a spin coater.

The mixing ratio of the transparent conductive filler 6 to the photosensitive resin is 45
% to 70% by weight is most suitable.

In the case of this photosensitive resin, the heat resistance temperature after bump formation is 15
The heat resistance is about 0°C, but if a cyclized butadiene resin is used, a heat resistant product of about 300°C can be obtained.

This photosensitive resin contains a volatile solvent in order to maintain a constant viscosity suitable for coating, but this is volatilized by the yellowtail bake treatment performed at a temperature of around 80°C before the exposure process. It is something that disappears.

Therefore, the content rate of the transparent conductive filler 6 is the same as that of the semiconductor substrate (
Although it is at least 70% by weight when applied to silicon wafers using a spin coater or screen printer, it is adjusted in advance so that it is within the range of 45% to 70% by weight when bump formation is completed. put.

Next, as shown in FIG. 3(b), the coated photosensitive conductive resin layer 7 is irradiated with ultraviolet rays through a glass mask 8.
The pattern of the glass mask 8 is printed at a predetermined position, and an exposure process is performed.

If the photosensitive resin 5 mixed with the transparent conductive filler 6 is of negative type, the portions not exposed to ultraviolet rays are removed by the next development process.

Although FIG. 3(b) shows an example in which a negative fist type photosensitive resin 5 is used, a positive type can also be used in the same way by reversing the masking during exposure.

Next, as shown in FIG. 3(C), when a development process is performed, the areas exposed to ultraviolet rays remain as elastic bumps 4 as described above.

In this step, a post-baking process is then performed at a temperature of about 145° C. to stabilize the photosensitive resin 5 and form the elastic bumps 4 on the electrode pads 2a.

As methods for mounting the semiconductor device having elastic bumps according to the present invention on other circuit boards, etc., there are two methods: After alignment, post-bake processing is performed while the semiconductor device is in pressure contact with each other, and the method is bonded and connected. There is a method of connecting to a circuit board or the like by pressing and fixing it with a spring or sealing resin.

In the former case, since heat of around 145° C. is applied, it is advisable to apply gold plating or the like to the connection terminals of the circuit board and the like to prevent oxidation.

FIG. 4 shows a cross-sectional view of an embodiment in which adhesive connection is made using post-bake processing.

When connected using this method, it is desirable to seal the entire body with resin in order to protect the connection between the conductor pattern 11 on the insulating substrate 12 and the elastic bumps 4 on the semiconductor substrate 1 and to improve adhesion reliability. .

In the present invention, an embodiment in which the transparent conductive filler 6 is a sphere has been described, but the shape of the transparent conductive filler 6 is not limited to this, and may also be applied to an incomplete sphere, an ellipsoid, a cube, a rectangular parallelepiped, and other polygons. Furthermore, it is obvious that transparent glass beads, transparent conductive plastics, etc. can be used in place of the transparent resin bulb 6a.

In addition, aluminum, which is a common component of electrode pads, tends to form an oxide film on its surface that increases contact resistance, and this becomes even more noticeable after heat treatments such as pre-bake and post-bake. Elastic bumps 4 are formed via electrode pads 2a in which nickel is laminated on the electrode pads 2a.

Since the purpose of this nickel is to prevent oxidation of the aluminum surface, other substances such as gold, silver, palladium, etc., which are difficult to oxidize at temperatures of around 150° C. applied during post-baking treatment, may be used.

FIG. 8 is a sectional view showing another embodiment of the method of forming the electrode pad 2a of this embodiment shown in FIG.

First, as shown in FIG. 8(a), on the semiconductor substrate 1,
An electrode pad 2 is formed of aluminum, and an insulating film 6 is further formed.
After forming the electrode pad 2 and opening the electrode pad 2, a conductive film 17 made of nickel is deposited over the entire surface. After that, a conductive resin layer is formed on the entire surface, and elastic bumps are formed by photolithography.

As shown in FIG. 8(b), this conductive film 17 is formed by using the formed elastic bumps 4 as an etching mask and removing the conductive film 17 except under the bumps by etching, thereby forming a conductive layer 17a.

〔Effect of the invention〕

As explained above, according to the present invention, by introducing a transparent conductive filler and applying photolithography, conventional semiconductor manufacturing equipment can be used as is, and the time required for bump formation is significantly reduced compared to the conventional method. This makes it possible to easily form high-precision bumps at low cost.

Furthermore, there is a large degree of freedom in designing the bump height, and since the formed bumps are made of highly elastic resin bumps, they have a large ability to relax external stress, and in the case of a mounting structure using pressure welding, there are advantages such as high connection reliability. In addition, bump pitch 30μ
m or less can be easily achieved, making it possible to significantly increase the number of terminals in an IC chip.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of a semiconductor device according to the present invention; FIG. 2 is a sectional view showing an embodiment of a transparent conductive filler which is one of the members constituting the bump in the present invention;
3(a) to 3(C) are cross-sectional views illustrating an example of forming bumps on a semiconductor substrate according to the present invention in the order of steps, and FIG. FIG. 5 is a cross-sectional view showing a semiconductor device formed with solder bumps for conventional general flip-chip connection, and FIG. 6 is a cross-sectional view showing an example of a conventional general flip-chip connection. FIG. 7 is a cross-sectional view showing a semiconductor device connected by the chip method, FIG. 7 is a cross-sectional view showing a semiconductor device connected by the conventional general TAB method, and FIGS. 8(a) and fb) are the formation of the semiconductor device according to the present invention. FIG. 3 is a cross-sectional view illustrating an embodiment of the method. 4...Elastic bump, 6a...Transparent resin ball. 5...Photosensitive resin, 6b...Transparent conductive material layer, 6...Transparent conductive filler Fig. 1 1' Semiconductor 412 (b) Fig. 2 (C ) 4. Elastic bread? / Figure 5 ρ, Ushihi no V pump + S stop base pump 2 electrode pad Figure 6 Figure 7 Figure 12, binding board + 6.1c + pump

Claims (2)

[Claims] (1) After forming an element, an insulating film with an opening at a position corresponding to the electrode pad is formed on the semiconductor substrate on which electrode pads for connection with the outside are formed, and an insulating film is formed to connect the external In a semiconductor device in which a protruding electrode for connection is formed, the protruding electrode is made of a photosensitive resin in which a conductive filler is mixed with a transparent conductive substance coated on the surface of fine transparent beads made of an organic resin. A semiconductor device characterized by: (2) A conductive resin layer made of a photosensitive resin mixed with a conductive filler made by coating the surface of transparent organic resin beads with a transparent conductive substance is applied to the entire surface of the insulating film with openings in the electrode pad area of the semiconductor substrate. 1. A method of manufacturing a semiconductor device, comprising the steps of: forming an elastic bump; and patterning the conductive resin layer by photolithography to form an elastic bump.