JPH09213700A - Manufacturing method of bump electrode - Google Patents

Abstract

(57) Abstract: It is an object of the present invention to provide a method of manufacturing a bump electrode in which a metal for a bump electrode is not corroded and a side reaction product is not generated. The etching solution used in the barrier metal film removing step is hydrochloric acid: nitric acid = 1: 9-.
Reverse aqua regia having a mixing ratio of 1:20 diluted with acetic acid 20 to 25 times, or ammonia: hydrogen peroxide = 1: 3 to
A solution in which a mixing ratio of 1: 4 is diluted 2-3 times with water and ethylenediaminetetraacetic acid is dissolved is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a bump electrode for connecting a chip of a flip chip type semiconductor device to the outside.

[0002]

2. Description of the Related Art Generally, as means for mounting a chip as a semiconductor device such as an integrated circuit on various wiring boards, etc., a case where the chip is once housed in a package and a bump electrode is provided. It may be mounted in the form of a flip chip. However, the latter flip-chip method is remarkably superior in that the mounting space can be reduced, the overall size can be reduced, and the mounting labor can be saved.

By the way, solder and Cu are used for the bump electrodes.
Metals such as (copper) and Au (gold) are used, and their sizes are various. In any case, the metal for the bump electrode is formed by the electroplating method in the state of the wafer before isolation into the flip chip. To grow.

That is, in the step shown in FIG. 6A, the surface of the substrate A is covered with an oxide film B of phosphorus silicate glass or the like, on which a metal film C of Al (aluminum) or the like for connection or wiring is formed. Are arranged in a predetermined pattern, and a small window E is opened in an insulating film D which is a so-called protective film covering silicon nitride or the like, and bump electrodes connected to the metal film C are provided through the window E. A thin barrier metal film F is deposited over the wafer to provide it. This barrier metal film F has a lower base film G1 such as Ti (titanium) or Cr (chrome) and Cu (copper), Pd (palladium), Pd (palladium), for the convenience of growing a bump electrode thereon by electrolytic plating.
It is a composite film composed of an upper base film G2 of Ni (nickel), Au (gold), W (tungsten), or the like.

In the process shown in FIG. 6B, however, a photoresist film H is spin-coated on the entire surface, and a plating window J is opened in a pattern larger than the window E of the insulating film D by a photo process. .

However, the step shown in FIG. 6C is a step of growing the bump electrode, and the window J of the photoresist film H is used.
Cu for the bump electrode by the electrolytic plating method using
A metal K such as Au or Au is grown to a height of, for example, several tens of μm. At this time, the barrier metal film F is used for the plating electrode,
By subjecting this to electrolytic plating while being connected to the cathode of the plating power source, the bump electrode metal K is grown to a thickness of, for example, 30 to 50 μm in many places in the wafer.

In the final step shown in FIG. 6D, after removing the photoresist film H, the upper base film G2 and the lower base film G1 are sequentially removed by chemical etching using the bump electrode metal K as a mask. To the state shown in the figure.

The lower base film G1 in the barrier metal film F
Is used as the above-mentioned plating electrode film and also serves as a barrier film for preventing the metal film C from diffusing into the bump electrode metal K. On the other hand, the upper base film G2 serves to connect the bump electrode metal K to the lower base film G1 at a relatively thin root of the bump electrode metal K with a low resistance value and high mechanical strength. .

[0009]

By the way, when the upper base film G2 and the lower base film G1 are sequentially removed by a chemical etching method, when the upper base film G2 is Ni, diluted nitric acid, or , A mixed solution of hydrofluoric acid: nitric acid: acetone = 1: 1: 1 was used. Also,
When etching Pd, aqua regia or a mixed solution of hydrochloric acid, nitric acid and acetic acid is used. However,
When such an etching solution is used, the bump electrode metal K is corroded and damaged during etching, and a part of the metal K is dissolved in the etching solution.

Further, when the lower base film G1 is Ti, the etching solution is hydrochloric acid or hydrofluoric acid solution, or
An aqueous solution of hydrofluoric acid: nitric acid: water = 1: 1: 50 is used. However, when hydrochloric acid is used as the etching liquid, the bump electrode metal K is corroded. When a hydrofluoric acid aqueous solution or an aqueous solution of hydrofluoric acid: nitric acid: water = 1: 1: 50 is used, a side reaction product may be formed on the silicon wafer.

In any case, the problems that the metal K for bump electrodes is corroded and the side reaction products are generated, which reduces the reliability of mounting by the flip chip method and contributes to the reduction in yield. The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for manufacturing a bump electrode that can solve the above problems.

[0012]

According to a first aspect of the present invention, there is provided a method of manufacturing a bump electrode, wherein the terminal metal film is electrically connected to the terminal metal film through a window formed in an insulating film covering the terminal metal film formed on the substrate. A barrier metal film formed by laminating palladium or nickel or palladium and nickel on the barrier metal film, and a solder bump provided on the barrier metal film, wherein the barrier metal film is an insulating film. A barrier metal film forming step of forming on the terminal metal film via the solder bump forming step of forming the solder bump on the barrier metal film after the barrier metal film forming step, and a solder bump forming step of And a barrier metal film removing step of removing the barrier metal film by etching with the solder bumps as a mask, which is used in the barrier metal film removing step. Are etchant, hydrochloric: nitric acid = 1: 9 to 1: 20 to the inverse aqua regia 20 mixing ratio of acetic acid
It is characterized by being diluted 25 times.

According to a second aspect of the present invention, in the method of manufacturing the bump electrode according to the first aspect, after etching the barrier metal film in the barrier metal film removing step, a mixed solvent having a mixing ratio of acetic acid: water = 1: 1 to 1: 2 is used. It is characterized by being washed.

According to a third aspect of the present invention, in the method of manufacturing a bump electrode, the barrier metal is electrically connected to the terminal metal film through a window opened in an insulating film covering the terminal metal film formed on the substrate. In a method of manufacturing a bump electrode including a barrier metal film made of titanium and a solder bump provided on the barrier metal film, a barrier formed by forming the barrier metal film on the terminal metal film via an insulating film. A metal film forming step,
A solder bump forming step of forming the solder bumps on the barrier metal film after the barrier metal film forming step, and a barrier metal removing the barrier metal film by etching using the solder bumps as a mask after the solder bump forming step. The etching solution used in the barrier metal film removing step is ethylenediamine prepared by diluting a solution having a mixing ratio of ammonia: hydrogen peroxide = 1: 3 to 1: 4 with water 2-3 times. It is a solution in which tetraacetic acid is dissolved.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a bump electrode, wherein a barrier metal electrically connected to the terminal metal film through a window opened in an insulating film covering the terminal metal film formed on the substrate. And a solder bump provided on the barrier metal film. The barrier metal film is an upper barrier metal film provided on the terminal metal film side and formed by laminating palladium or nickel or the palladium and nickel. And a lower barrier metal film made of titanium provided on the solder bump side, and a barrier metal film is formed on the terminal metal film via an insulating film in the method of manufacturing a bump electrode. And a solder bump forming step of forming the solder bumps on the barrier metal film after the barrier metal film forming step, and a solder bump forming step after the solder bump forming step. And a barrier metal film removing step of removing the barrier metal film by etching as a mask. In the barrier metal film removing step, the upper barrier metal film has a mixing ratio of hydrochloric acid: nitric acid = 1: 9 to 1:20. An upper barrier metal film removal step of removing the reverse aqua regia with an etching solution diluted 20 to 25 times with acetic acid, and the lower barrier metal film after the upper barrier metal film removal step is ammonia: hydrogen peroxide = 1: 3. A lower barrier metal film removing step of diluting a solution having a mixing ratio of ˜1: 4 by 2 to 3 times with water and removing with an etching solution in which ethylenediaminetetraacetic acid is dissolved.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a bump electrode 1 manufactured by the method for manufacturing a bump electrode according to this embodiment. That is, the bump electrode 1 becomes a connection or wiring terminal with a thickness of 1 to 1.5 μm formed in a predetermined pattern on the silicon wafer 2 through the oxide film 2a.
Insulation (passivation) of, for example, silicon nitride or silicon dioxide having a thickness of 1 to 2 μm, which covers the metal film 3 made of
It is electrically connected to the metal film 3 through a circular window 5 formed in the film 4. The structure of the bump electrode 1 includes a barrier metal film 6 connected to the metal film 3 through the window 5 and, for example, a height 3 provided on the barrier metal film 6.
The solder bump 7 has a substantially spherical diameter of 0 to 50 μm. The barrier metal film 6 is made of Ti having a barrier effect against Al diffusion and has a thickness of 0.1 to 0.3.
μm lower barrier metal film 8 and this lower barrier metal film 8
A thickness of 0.2 to 0.6 μm made of Pd that is well compatible with the solder bump 7 and the lower barrier metal film 8 provided on the upper side.
m of the upper barrier metal film 9 to form a composite film.

Therefore, in the bump electrode manufacturing method of this embodiment, the barrier metal film forming step of forming the barrier metal film 6 on the wafer 2 via the insulating film 4 (FIG. 3, step S).
1 and FIG. 2A), and a solder bump forming step (FIG. 3) of forming solder bumps 7 using the barrier metal film 6 as a plating electrode by electrolytic plating after the barrier metal film forming step.
Step S2 and FIG. 2B), and a barrier metal film removing step of removing the barrier metal film 6 using the solder bumps 7 as a mask after the solder bump forming step (step S3 in FIG. 3).
2C) and a solder bump shaping step (see step S4 in FIG. 3 and FIG. 1) of applying a flux to the solder bump 7 and obtaining a hemispherical solder bump 7a by wet back.

The barrier metal film forming step includes a lower barrier metal film forming step of forming a lower barrier metal film 8 made of Ti and having a thickness of 0.1 to 0.3 μm, and the lower barrier metal film step. An upper barrier metal film forming step of later forming an upper barrier metal film 9 made of Pd and having a thickness of 0.2 to 0.6 μm. In each of the lower barrier metal film forming step and the upper barrier metal film forming step, the metal films 8 and 9 are formed on the entire surface of the wafer 2 by the sputtering method.

On the other hand, the barrier metal film removing step includes an upper barrier metal film removing step of removing the upper barrier metal film 9 of Pd and a lower barrier metal film forming step of removing the lower barrier metal film 8 of Ti. It consists of

Therefore, the upper barrier metal film removing step is
Hydrochloric acid: nitric acid = 1: 9 to 1:20 (provided that hydrochloric acid was 35% by volume and nitric acid was 61% by volume, which were commercially available products.)
An upper barrier metal film etching step of removing the upper barrier metal film 9 made of Pd by immersing the reverse aqua regia in a mixing ratio of 20 to 25 times with acetic acid, and acetic acid: water after this etching step. = 1: 1 to 1: 2
And a cleaning step in which cleaning treatment is performed by immersing in a mixed solvent having a mixing ratio of. The temperature of the etching solution in the above etching process is 24 ° C to 25 ° C.
C is preferred. The immersion time in the etching solution is
5 minutes to 6 minutes is suitable. Further, the temperature of the cleaning liquid in the cleaning step is preferably 5 ° C to 6 ° C. Further, the immersion time in the cleaning liquid is preferably 0.5 minutes to 1 minute.

Further, in the step of forming the lower barrier metal film, ammonia: hydrogen peroxide = 1: 3 to 1: 4 (however, a commercially available product containing 30% by volume of ammonia and 30% by volume of hydrogen peroxide was used. ) A lower barrier metal film etching step of removing the lower barrier metal film 8 made of Ti by dipping the solution having a mixing ratio of 2 to 3 times with water and immersing it in a solution in which ethylenediaminetetraacetic acid is dissolved, After the etching step, the cleaning step is performed by immersing in water and performing a cleaning process.

However, the temperature of the etching solution in the above etching step is preferably 24 ° C to 25 ° C. Further, the immersion time in the etching solution is preferably 2 minutes to 3 minutes. Further, the temperature of the washing water in the washing step is preferably 24 ° C to 25 ° C. Further, the immersion time in the washing water is preferably 10 minutes to 15 minutes.

In the etching process of removing the upper barrier metal film, however, hydrochloric acid: nitric acid = 1: 9 to 1: 2.
Since the upper barrier metal film 9 made of Pd is removed by an etching solution obtained by diluting reverse aqua regia with a mixing ratio of 0 by 20 to 25 times with acetic acid, the solder bump 7 is not corroded and the solder bump Not only the upper barrier metal film 9 made of Pd not covered by 7 could be reliably removed by etching, but no by-products were generated.

By the way, as shown in FIG. 4, when the reverse aqua regia was diluted with acetic acid diluted 11 times, the solder bumps 7 were significantly corroded. Further, when the reverse aqua regia was diluted 51 times with acetic acid and etched, the solder bumps 7 were slightly corroded. Based on these experimental data, the optimal dilution range was found to be 20-25 fold. Further, in this case, the etching solution does not contain a dangerous substance such as hydrofluoric acid,
It also has the advantage of being extremely easy to handle and helping to improve productivity.

Further, in the cleaning process of the upper barrier metal film removing process, acetic acid: water = 1: 1 to 1: 1 as a cleaning liquid.
Since the mixed solvent having the mixing ratio of 2 was used, the surface of the wafer 2 was not clouded.

On the other hand, in the etching process of the lower barrier metal film forming process, ammonia: hydrogen peroxide = 1: 3
Since a solution having a mixing ratio of ˜1: 4 is diluted 2-3 times with water and ethylenediaminetetraacetic acid is dissolved,
Not only the lower barrier metal film 8 made of Ti, which is not covered with the solder bumps 7, can be reliably removed by etching without corroding the solder bumps 7, and no by-products were generated. . In addition, the etching liquid in this case does not contain absorptive substances such as hydrofluoric acid, and has an advantage that handling is extremely easy and productivity is improved.

In this way, in the barrier metal film removing step, the solder bumps 7 are not corroded, so that it is possible to prevent the occurrence of connection failure and contribute to the improvement of reliability.

Further, since the amount of Pb (lead) dissolved in the etching liquid is small, the waste liquid treatment becomes relatively easy. Further, the etching solution does not contain a dangerous substance such as hydrofluoric acid, and thus has an advantage that it is extremely easy to handle and helps to improve productivity.

In the bump electrode manufacturing method of the above embodiment, the barrier metal film 6 has a composite structure composed of the lower barrier metal film 8 and the upper barrier metal film 9.
A single layer structure of only Ti, only Pd, or only Ni may be used. In this case, the etching conditions in the case of using only Ni are almost the same as those in the above-described Pd removing process.

Further, as shown in FIG. 5, the upper barrier metal film 9 may be composed of a Ni film 9a and a Pd film 9b formed on the Ni film 9a. In this case, the etching conditions are almost the same as in the case of the Pd removal treatment described above, and the Ni film 9a and the Pd film 9b can be simultaneously removed by etching.

[0031]

The bump electrode manufacturing method according to the first to fourth aspects has the following particular effects. That is, since the solder bumps are not corroded in the step [1] of removing the barrier metal film, it is possible to prevent the occurrence of connection failure and contribute to the improvement of reliability. [2] Since the amount of Pb (lead) dissolved in the etching liquid is small, the waste liquid treatment becomes relatively easy. [3] The etching liquid does not contain absorptive substances such as hydrofluoric acid, and has the advantage of being extremely easy to handle and helping to improve productivity.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a bump electrode manufactured by a bump electrode manufacturing method according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a bump electrode manufacturing method according to an embodiment of the present invention.

FIG. 3 is a flowchart showing a bump electrode manufacturing method according to an embodiment of the present invention.

FIG. 4 is a diagram showing an effect of an etching solution used in the bump electrode manufacturing method according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram of a bump electrode manufacturing method according to another embodiment of the present invention.

FIG. 6 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

1: bump electrode, 2: wafer, 3: metal film, 4: insulating (passivation) film, 6: barrier metal film, 7: solder bump, 8: lower barrier metal film, 9: upper barrier metal film.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 21/92 603E

Claims (4)

[Claims] 1. Palladium or nickel, or palladium and nickel, which are electrically connected to the terminal metal film through a window opened in an insulating film covering the terminal metal film formed on a substrate, are laminated. Forming a barrier metal film on the terminal metal film via an insulating film in a method of manufacturing a bump electrode comprising a barrier metal film formed of the barrier metal film and a solder bump provided on the barrier metal film. And a step of forming the solder bumps on the barrier metal film after the step of forming the barrier metal film, and a step of etching the barrier metal film using the solder bumps as a mask after the step of forming the solder bumps. And a barrier metal film removing step, wherein in the barrier metal film removing step, the barrier metal film is removed by hydrochloric acid: nitric acid = 1: 9 to 1 Method for manufacturing a bump electrode which is characterized in that the etchant reverse aqua regia mixing ratio was diluted 20-25 fold in acetic acid 20. 2. The method according to claim 1, wherein after the barrier metal film is etched in the barrier metal film removing step, the barrier metal film is washed with a mixed solvent having a mixing ratio of acetic acid: water = 1: 1 to 1: 2.
A method for manufacturing a bump electrode as described above. 3. A barrier metal film electrically connected to the terminal metal film through a window opened in an insulating film covering the terminal metal film formed on a substrate, the barrier metal film comprising titanium. A barrier metal film forming step of forming the barrier metal film on the terminal metal film via an insulating film in a method of manufacturing a bump electrode including a solder bump provided on the barrier metal film; A solder bump forming step of forming the solder bump on the barrier metal film after the film forming step, and a barrier metal film removing step of removing the barrier metal film by etching using the solder bump as a mask after the solder bump forming step In the step of removing the barrier metal film, the barrier metal film is removed by adding a solution of ammonia: hydrogen peroxide = 1: 3 to 1: 4 with water in an amount of 2 to 2 times. Method for manufacturing a bump electrode which is characterized in that the times to dissolve the diluted ethylenediaminetetraacetic acid in an etching solution. 4. A barrier metal film electrically connected to the terminal metal film through a window opened in an insulating film covering the terminal metal film formed on the substrate, and a barrier metal film on the barrier metal film. The barrier metal film is provided on the terminal metal film side, and the barrier metal film is provided on the solder bump side and an upper barrier metal film formed by laminating palladium or nickel or the palladium and nickel. In a method of manufacturing a bump electrode including a lower barrier metal film made of titanium, a barrier metal film forming step of forming the barrier metal film on the terminal metal film via an insulating film, and a barrier metal film forming step After that, a step of forming the solder bump on the barrier metal film is performed, and after the step of forming the solder bump, the barrier metal film is etched using the solder bump as a mask. And a barrier metal film removing step of removing the upper barrier metal film with hydrochloric acid: nitric acid = 1: 9 to 1:20 in reverse aqua regia with acetic acid. The upper barrier metal film removing step of removing with an etching solution diluted to 25 times, and the lower barrier metal film after the upper barrier metal film removing step has a mixing ratio of ammonia: hydrogen peroxide = 1: 3 to 1: 4. And a lower barrier metal film removing step of diluting the solution of 2 to 3 times with water and removing with an etching solution in which ethylenediaminetetraacetic acid is dissolved.