JPH08213401A - Bump electrode and manufacture thereof - Google Patents

Abstract

PURPOSE: To increase the connecting area of a first layer of an electrode root to an electrode pad and an insulating film and to improve the strength of a bump electrode by increasing the diameter of the root made of a metal film or the first layer of the root larger than that of the electrode. CONSTITUTION: A barrier metal first layer 4 made of TiN, a barrier metal second layer 5 made of Ti having a diameter smaller than the diameter of the layer 4, an electrode substrate film 6 having the same diameter as that of the layer 5 made of Cu, an electrode 8 having the same diameter as that of the film 6 made of Cu and a solder bump 9 are sequentially laminated on an insulating film 3 made of SiN having a hole 3' which has a diameter smaller than that of an Al pad 2 at the position of the pad 2 to protect the pad 2 provided on a wiring for wiring an element, the wiring and the element on a wafer board 1, The diameter of the layer 4 is increased larger than that of the layer 5 to increase the connecting area of the pad 2 to the film 3 and the layer 4, thereby improving the strength of a bump electrode 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bump electrode used for electrical connection between an electronic device including an integrated circuit and the like and the outside and a method for manufacturing the bump electrode.

[0002]

2. Description of the Related Art In recent years, there has been a demand for high-density mounting of electronic devices such as computers and hybrid ICs for automobiles in order to reduce costs. Among them, the flip-chip mounting method using the solder bump protruding electrodes has attracted attention as a high-density mounting method because the bonding area is smaller than other mounting methods and the bonding strength is high.

In particular, in recent years, ICs have become highly integrated as products have become highly integrated and multifunctional, and therefore bump bump electrodes tend to be miniaturized. Further, conventionally, as a mounting structure mounted by a flip-chip mounting method, a signal of a semiconductor element is taken out, a barrier metal (electrode root portion) is formed under a take-in electrode by sputtering Ti, and then a bump electrode is vapor-deposited. Those formed by a plating method, a plating method, etc. are well known (Japanese Patent Laid-Open No. 4-217323).
issue).

[0004]

However, a barrier metal such as that disclosed in Japanese Patent Laid-Open No. 4-217323 has a T content.
In the structure using i, over-etching or under-etching occurs depending on the etching time, which causes a variation in the diameter of the bump electrode and a variation in the strength of the bump electrode. For example, the relationship between the diameter of the bump electrode and the strength of the bump electrode is shown in FIG. 4. When the diameter of the bump electrode changes from 220 μm to 160 μm, the strength decreases from 300 g to about ½ of that. When the diameter of the bump electrode becomes 50 μm, its strength decreases to about 15 g.

The diameter of the bump electrode is 160 μm and 5
When variations of ± 10 μm are generated by etching centered on 0 μm, the variations of the respective intensities at 160 μm and 50 μm are as shown in FIG. That is, when the diameter of the bump electrode varies by ± 10 μm with 160 μm as the center due to enching, the strength has a variation of 0.88 to 1.12, but when the variation occurs by ± 10 μm around 50 μm, Its strength varies widely from 0.64 to 1.44.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a bump electrode having a large diameter at the electrode base and no variation in the diameter and a method for manufacturing the bump electrode.

[0007]

In order to solve the above problems, the structure of the present invention has an electrode pad formed on a substrate of an electronic device including an integrated circuit and the electrode pad at the position of the electrode pad. Bumps for forming electrical connection between the electronic device and the outside, which have holes with a diameter smaller than that of the electronic device and are formed on an insulating film for protecting wirings and elements formed on the substrate. An electrode, which is formed on the electrode root portion, is composed of an electrode root portion formed of a metal film formed on the electrode pad and the insulating film, and a metal film having a composition different from that of the metal film forming the electrode root portion. An electrode base film and a metal film having a composition different from that of the metal film forming the electrode base, the electrode part formed on the electrode base film, solder, and solder bumps formed on the electrode part are sequentially laminated. Formed and configured, the electrode root Diameter of the metal film to be formed is characterized in that it is larger than the diameter of the electrode portion.

According to the second aspect of the invention, the metal film forming the electrode root portion is formed on the first layer and the second layer having an etching rate higher than the etching rate of the first layer.
And the diameter of the first layer is larger than the diameter of the electrode portion, and the diameter of the second layer is the same as the diameter of the electrode portion.

The structure of the third invention is characterized in that the second layer at the base of the electrode is composed of Ti having a film thickness of 5 nm to 80 nm.

According to a fourth aspect of the present invention, there is provided an electrode pad formed on a substrate of an electronic device including an integrated circuit and a hole having a diameter smaller than the diameter of the electrode pad at the position of the electrode pad. A method of manufacturing a bump electrode, which is formed on an insulating film for protecting wirings and elements formed on a substrate and electrically connects the electronic device to the outside, comprising a metal film. A step of forming an electrode root on the electrode pad and the insulating film; a step of forming an electrode base film made of a metal film having a composition different from that of the metal film forming the electrode root on the electrode root; A step of forming an electrode portion composed of a metal film having a composition different from that of the constituent metal film on the electrode base film,
And a step of forming a solder bump made of solder on the electrode portion, and in the step of forming the electrode root portion, the diameter of the electrode root portion is formed larger than the diameter of the electrode portion.

According to a fifth aspect of the invention, the step of forming the electrode root portion includes the step of forming the first layer as the electrode root portion,
Forming on the first layer a second layer having an etching rate higher than the etching rate of the first layer;
The same etching solution is used in the step of forming the layer and the step of forming the second layer, and in the step of forming the second layer, the diameter of the second layer is formed to be the same as the diameter of the electrode portion. The step of forming is characterized in that the diameter of the first layer is formed larger than the diameter of the electrode portion.

According to the sixth aspect of the invention, in the step of forming the second layer at the base of the electrode, the second layer is made of Ti with a thickness of 5 nm to 80 nm.
It is characterized in that it is formed to a film thickness of nm.

[0013]

The first function of the present invention is to have an electrode pad formed on a substrate of an electronic device including an integrated circuit and a hole having a diameter smaller than the diameter of the electrode pad at the position of the electrode pad. Then, in the bump electrode for electrically connecting the electronic device and the outside, which is formed on the insulating film for protecting the wiring and the element formed on the substrate, the electrode base made of the metal film is formed. The diameter of the electrode portion or the diameter of the first layer of the electrode root portion is made larger than the diameter of the electrode portion, and as a result, the bonding area between the first layer of the electrode root portion and the electrode pad and the insulating film is increased. Therefore, the strength of the bump electrode can be improved. (Claims 1 to 6)

A second function is to form a metal film forming an electrode root portion of the bump electrode on the first layer and the first layer, and to provide a second etching rate higher than that of the first layer. Layer and using the same etchant,
The diameter of the first layer is formed to be larger than the diameter of the electrode portion, and the diameter of the second layer is formed to be the same as the diameter of the electrode portion. The effect is that two layers having different diameters are subjected to the same etching. It can be easily formed with a liquid. (Claim 2, Claim 3, Claim 5, Claim 6)

The third action is to make the second layer at the base of the electrode 5n.
The Ti film has a thickness of m to 80 nm, and the effect is that the Ti film does not become brittle during hydrogen annealing, so that the strength of the bump electrode can be maintained at a certain level. (Claims 3 and 6)

[0016]

EXAMPLES The present invention will be described below based on specific examples. FIG. 1 shows the configuration of the first embodiment of the present invention. The bump electrodes 10 are Al pads 2 (electrode pads) provided on the wiring for connecting the elements arranged on the wafer substrate 1 and A for protecting the wiring and the elements.
On the passivation film 3 (insulating film) made of SiN in which a hole 3'having a diameter smaller than that of the Al pad 2 is provided at the position of the l pad 2, the barrier metal first layer 4 made of TiN (electrode base portion) is formed. Corresponding to the first layer), a barrier metal second layer 5 made of Ti and having a diameter smaller than that of the barrier metal first layer 4 (corresponding to the second layer at the base of the electrode), and a barrier metal second layer 5 made of Cu. An electrode base film 6 having the same diameter as the electrode base film 6, an electrode base film 6 having the same diameter as the electrode base film 6, and a solder bump 9 made of solder are sequentially laminated and formed.

The barrier metal first layer 4 has a thickness of 200 nm to 30.
The barrier metal second layer 5 is formed to a thickness of 0 nm and has a thickness of 5 n.
The film is formed with a film thickness of m to 80 nm. In addition, the electrode base film 6
Is formed with a film thickness of 500 nm to 1000 nm, and the electrode portion 8 is formed with a film thickness of 10 μm to 50 μm. The diameter of the barrier metal first layer 4 is 8 μ than the diameter of the barrier metal second layer 5.
It is formed larger by m to 12 μm.

In the above structure, the barrier metal first layer 4
Is formed larger than the diameter of the barrier metal second layer 5, but the bonding strength between the barrier metal first layer 4 and the barrier metal second layer 5 and the bonding between the barrier metal second layer 5 and the electrode base film 6 Since the bonding strength between the Al pad 2 and the passivation film 3 and the barrier metal first layer 4 is smaller than the strength, the diameter of the barrier metal first layer 4 is formed larger than that of the barrier metal second layer 5. The bump electrode 1
The strength of 0 can be improved.

That is, FIG. 3 shows the relationship between the diameter of the barrier metal first layer 4 and the shear strength of the bump electrode 10. It can be seen that as the diameter of the barrier metal first layer 4 increases, the shear strength also increases. . Therefore, by forming the diameter of the barrier metal first layer 4 larger than the diameter of the barrier metal second layer 5, the bonding strength between the Al pad 2 and the passivation film 3 and the barrier metal first layer 4 is improved, and the Al pad 2 and the passivation film 3 and the barrier metal first layer 4 are not peeled off, and the shear strength of the bump electrode 10 can be improved.

As shown in FIG. 3, when the thickness of the barrier metal second layer 5 made of Ti is 5 nm to 80 nm, the shear strength of the bump electrode 10 increases as the diameter of the barrier metal first layer 4 increases. But the barrier metal second layer 5
If the film thickness exceeds 80 nm, the diameter of the barrier metal first layer 4 increases, but the Ti film becomes brittle due to the hydrogen annealing treatment, and the shear strength decreases. Therefore, by setting the thickness of the barrier metal second layer 5 to 5 nm to 80 nm, the shear strength of the bump electrode 10 can be maintained at a constant level.

Next, a method of manufacturing the bump electrode 10 will be described below with reference to FIG. First, in order to connect the elements arranged on the wafer substrate 1, an Al pad 2 is formed on the wiring, and a hole 3 ′ having a diameter smaller than the diameter of the Al pad 2 is provided at the position of the Al pad 2. A passivation film 3 made of is formed on the wafer substrate 1 and the Al pad 2 in order to protect the elements and wirings on the wafer substrate 1 (FIG. 2A).

Then, TiN is sputtered on the surface of the wafer substrate 1 on which the passivation film 3 is formed by sputtering.
The barrier metal first layer 4 is formed with a film thickness of 00 nm to 300 nm (the step of forming the first layer at the base of the electrode), and then Ti is sputtered on the barrier metal first layer 4 to a thickness of 5 nm. The barrier metal second layer 5 is formed with a film thickness of ˜80 nm (step of forming the first layer at the electrode root). After the barrier metal second layer 5 is formed, an electrode base film 6 made of Cu is formed to a film thickness of 500 nm to 1000 nm (step of forming the electrode base film) (FIG. 2B).

After forming the electrode base film 6, in order to form the bump electrode 10 having a predetermined shape at a predetermined position, a resist 7 is applied on the electrode base film 6 and then exposed and developed by a photo process. A photo hole 7'having a predetermined shape is formed at a predetermined position (FIG. 2 (c)). At the position where the photohole 7'is formed, the electrode portion 8 is plated (electric field or electroless plating), for example, a Cu film is plated with copper sulfate to a thickness of 10 μm.
It is formed to a film thickness of 50 μm (step of forming an electrode portion).
After the electrode portion 8 is formed, solder plating is performed on the electrode portion 8 with an organic acid bath or a hydrofluoric acid bath to form solder bumps 9 (step of forming solder bumps) (FIG. 2D).

After forming the solder bumps 9, the resist 7 is removed. Subsequently, the electrode base film 6 made of a Cu film is etched by using an etching solution capable of selectively etching only Cu. Next, using an ethylenediaminetetratetraacetic acid (hereinafter referred to as EDTA) -based Ti etching solution, Ti
The film and the TiN film are simultaneously etched.

Here, the liquid temperature of the Ti etching liquid is 60 ±.
At 5 ° C., the liquid composition is EDTA: 10 g to 20 g / H ₂ O 1liter H ₂ O ₂ : 280 ml to 440 ml / H ₂ O 1liter NH ₄ OH: 24 ml to 36 ml / H ₂ O 1liter.

The etching rate (vertical direction) of the EDTA-based Ti etching solution at 60 ° C. is 3.75 nm / sec for the Ti film and 2.15 nm for the TiN film.
/ Sec, and the barrier metal first layer 4 and the barrier metal second layer 5 are made of materials having different etching rates with respect to the same etching solution. By using a material having an etching rate higher than that of the first layer 4, the barrier metal second layer 5 has the same diameter as the electrode portion 8 and the barrier metal first layer 4 has a diameter larger than the diameter of the electrode portion 8 by 8 μm to 12 μm. Form. Finally, the bump electrode 10 is formed by reflowing the solder by heat treatment (see FIG. 2).
(E)).

As described above, the barrier metal as the electrode base of the bump electrode 10 has a two-layer structure, and the material having a low etching rate is the lower barrier metal first layer 4.
The barrier metal second layer 5 having the same diameter as that of the electrode portion 8 by arranging a material having a high etching rate in the upper barrier metal second layer 5 and etching using the same Ti etching solution. The barrier metal first layer 4 can be formed to have a diameter larger than the electrode portion 8 by 8 μm to 12 μm,
As a result, the barrier metal first layer 4 and A having a small bonding strength are formed.
Since the bonding area between the l pad 2 and the passivation film 3 can be made large, the barrier metal first layer 4
The strength between the Al pad 2 and the passivation film 3 is improved, peeling does not occur, and the shear strength of the bump electrode 10 can be improved.

On the other hand, the bonding areas between the barrier metal first layer 4 and the barrier metal second layer 5 and between the barrier metal second layer 5 and the electrode base film 6 are the same as the barrier metal first layer 4 and the Al.
Although the bonding area is smaller than the bonding area between the pad 2 and the passivation film 3, the bonding strength is large, so that peeling does not occur and the shear strength of the bump electrode 10 can be maintained. In addition, since the bump electrode 10 can be formed with high accuracy by using the above method, it is possible to manufacture the bump electrode 10 of high quality without variations in its strength.

In the present embodiment, TiN is used as the barrier metal first layer 4, but the present invention is not limited to this, and when the barrier metal second layer 5 is Ti, TiO 2 is used.
₂ , a Ti alloy such as TiC may be used. Further, although Ti is used as the barrier metal second layer 5 in the present embodiment, it is not limited to this, and Zr may be used. In that case, ZrO ₂ is contained in the barrier metal first layer 4, ZrN or the like may be used.

In the present invention, the barrier metal first layer 4 and the barrier metal second layer 5 are not necessarily limited to the above composition, but materials having different etching rates for the same etching solution are used, and the barrier metal of the lower layer is formed. The first layer 4 may be made of a material having a low etching rate, and the upper barrier metal second layer 5 may be made of a material having a high etching rate, and the material is not limited.

Depending on the target product (for example, IC card,
Liquid crystal products, mobile phones, etc.) and solder bumps 9 are not necessary, but the barrier metal first layer 4, barrier metal second layer 5, electrode base film 6, etc. are collectively formed with Cl ₂ , BCl ₃ , CF _4, etc. If the electrode portion 8 is dry-etched, the etching rate is barrier metal first layer 4 <barrier metal second layer 5
Therefore, a predetermined shape can be obtained. Further, in the present embodiment, the passivation film 3 is formed of SiN, but the present invention is not limited to this, and SiO ₂
Any insulating film such as a film may be used.

As indicated above, according to the present invention,
The electrode root portion has a two-layer structure, a material having a high etching rate is arranged in the second layer (upper layer) of the electrode root portion, and a material having a low etching rate is arranged in the first layer (lower layer) of the electrode root portion, The first layer and the second layer are etched using the same etching solution, and the diameter of the first layer is 8 μm or less than the diameter of the electrode portion.
By forming the bump electrode 12 μm larger, the shear strength of the bump electrode can be improved, and since the bump electrode can be formed with high accuracy, there is no variation in the shear strength of the bump electrode, and the bump electrode has high strength. Higher quality is possible. In addition, the second layer at the base of the electrode is 5n
By forming the Ti film with a thickness of m to 80 nm, the Ti film is not embrittled by the hydrogen annealing treatment.
The shear strength of the bump electrode can be maintained at a constant level.

[Brief description of drawings]

FIG. 1 is a structural diagram showing a configuration of a first embodiment according to the present invention.

FIG. 2 is a schematic diagram showing a method for manufacturing bump electrodes.

FIG. 3 is a relationship diagram showing the relationship between the diameter of the barrier metal first layer, the film thickness of the barrier metal second layer, and the shear strength of the bump electrode.

FIG. 4 is a graph showing a relationship between a diameter of a bump electrode and strength.

FIG. 5 is a graph showing the relationship between variations in the diameter of bump electrodes and variations in strength.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wafer substrate 2 Al pad (electrode pad) 3 Passivation film (insulating film) 4 Barrier metal 1st layer (electrode root part 1st layer) 5 Barrier metal 2nd layer (electrode root part 2nd layer) 6 Electrode base film 7 Resist 8 Electrode 9 Solder bump 10 Bump electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Tanaka 1-1, Showa-cho, Kariya city, Aichi Prefecture Nihon Denso Co., Ltd. (72) Inventor Keiji Mayama 1-1-cho, Showa-cho, Kariya city, Aichi prefecture Co., Ltd. (72) Inventor Koji Ino 1-1, Showa-cho, Kariya city, Aichi prefecture

Claims (6)

[Claims] 1. An electrode pad formed on a substrate of an electronic device including an integrated circuit, and a hole having a diameter smaller than the diameter of the electrode pad at the position of the electrode pad, and formed on the substrate. A bump electrode, which is formed on an insulating film for protecting wirings and elements, for electrically connecting the electronic device to the outside, the metal being formed on the electrode pad and the insulating film. An electrode root part made of a film, an electrode base film formed on the electrode root part, which is made of a metal film having a composition different from that of the metal film forming the electrode root part, and the metal forming the electrode root part A metal film having a composition different from that of the film, the electrode part formed on the electrode base film, and solder bumps formed on the electrode part, which are formed on the electrode part, are sequentially laminated and formed, and the electrode root part is formed. The metal film constituting the Diameter bump electrodes, characterized in that it is formed larger than the diameter of the electrode portion. 2. The metal film forming the electrode root portion,
A first layer and a second layer formed on the first layer and having an etching rate higher than the etching rate of the first layer, wherein the diameter of the first layer is larger than the diameter of the electrode portion;
The bump electrode according to claim 1, wherein the diameter of the layer is formed to be the same as the diameter of the electrode portion. 3. The second layer at the base of the electrode has a thickness of 5 nm to
The bump electrode according to claim 2, wherein the bump electrode is made of Ti having a film thickness of 80 nm. 4. An electrode pad formed on a substrate of an electronic device including an integrated circuit, and a hole having a diameter smaller than the diameter of the electrode pad formed at the position of the electrode pad, formed on the substrate. A method of manufacturing a bump electrode, which is formed on an insulating film for protecting wirings and elements, for electrically connecting the electronic device to the outside, comprising: A step of forming on the pad and the insulating film, a step of forming an electrode base film made of a metal film having a composition different from that of the metal film forming the electrode root portion on the electrode root portion, and the electrode root portion A step of forming an electrode part made of a metal film having a composition different from that of the metal film on the electrode base film, and a step of forming solder bumps made of solder on the electrode part; In the process of forming Method for manufacturing a bump electrode and forming a diameter of the electrode base portion greater than the diameter of the electrode portion. 5. The step of forming the electrode root portion includes a step of forming a first layer as the electrode root portion, and a second etching rate higher than an etching rate of the first layer on the first layer. A step of forming a layer, the step of forming the first layer and the step of forming the second layer use the same etching solution, and the step of forming the second layer The diameter of the second layer is formed to be the same as the diameter of the electrode portion, and in the step of forming the first layer, the diameter of the first layer is formed to be larger than the diameter of the electrode portion. Item 5. A method for manufacturing a bump electrode according to Item 4. 6. The bump according to claim 5, wherein in the step of forming the second layer at the base of the electrode, the second layer is formed of Ti to a film thickness of 5 nm to 80 nm. Electrode manufacturing method.