JPH05335315A - Manufacture of electrode - Google Patents

Abstract

PURPOSE:To suppress short-circuiting between bump electrodes having high contact strength and small electrode pitch by covering he region other than that for an electrode with photosensitive resin, and by plating it with an acid zincate conversion plating liquid, at the time of manufacturing a bump electrode to be used for minutely mounting a semiconductor element through electroless plating process. CONSTITUTION:A conductive layer 3 composed of aluminum is formed on a silicon substrate 1 forming a circuit, and a nickel/phosphorus layer 5 is formed on the conductive layer 3, and a gold layer 6 is formed on the nickel/phosphorus layer 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a projection-shaped electrode used for fine mounting of semiconductor elements.

[0002]

2. Description of the Related Art A method for connecting an element using a semiconductor or an insulator to an external circuit is a thin film mounting method typified by TAB (Tape Automated Bonding) or flip chip, or a wire bonding method widely used in packages. There is. Among them, TAB is expanding its field of application because it can be mounted in a small size and light weight.

The protruding electrodes (bumps) required for the TAB on the side of the semiconductor element are required to shorten the manufacturing process, so that the "plating and finishing" magazine, July issue, 19
In 1988, as shown on page 70, a method of forming an electroless plated film by activation using a zinc substitution method was known.

However, the conventional zinc displacement plating technique has the following problems.

First, the zinc substitution method can improve the plating strength because it can remove the aluminum oxide film. However, in the conventionally known zinc substitution method, since a strongly alkaline zinc substitution solution is used, the aluminum thin film which is an electrode is instantaneously etched, and the aluminum layer must be thickened in order to obtain bump strength.
Furthermore, since the aluminum conductive layer of the semiconductor element tends to be thinned due to the miniaturization of the pattern rule of the semiconductor element, the conventional zinc substitution method has a high bump strength and can manufacture a miniaturized electrode. It was difficult.

Secondly, when the plating electrodes have a narrow pitch, they come into contact with adjacent electrodes due to isotropic growth of plating. Therefore, a method of preventing contact by using a photosensitive resin is known. However, the conventional zinc substitution method has a problem that the resin is dissolved due to its alkalinity and such a contact prevention method cannot be adopted.

Thirdly, the alkaline zinc displacement plating solution is
It has the function of melting not only aluminum but also the insulating layer,
In addition, no means has been taken to prevent dissolution of the insulating layer due to resist or the like.

Therefore, for the purpose of solving these problems, it was considered to apply an acidic zinc displacement plating solution containing hydrofluoric acid, which has a smaller etching amount of aluminum than an alkaline zinc displacement plating solution.

[0009]

However, since the conventional technique is a zinc displacement plating solution using hydrofluoric acid, the resist is damaged by the action of hydrofluoric acid in the acidic zinc displacement plating solution, and the resist during the plating treatment may be damaged. There is a problem that peeling or the like occurs and the function as a plating resist cannot be exhibited.

The present invention solves these problems, and an object thereof is to improve a zinc displacement plating solution, prevent resist peeling, and achieve high connection strength even in a narrow pitch electrode using a resist and having a small electrode area. A method for manufacturing an electrode having high reliability when finally connected is provided.

[0011]

According to the method of manufacturing an electrode of the present invention, a conductive layer made of aluminum is laminated on a semiconductor substrate through a first insulating layer, and a region other than a predetermined electrode region is covered with a second insulating layer. Then, in the method for producing an electrode, in which a zinc layer is plated on the conductive layer in the electrode planned region and a connection metal layer is laminated on the zinc layer, the aluminum other than the electrode planned region on the semiconductor substrate is used. A photosensitive resin layer is applied onto the conductive layer and the second insulating layer, and the zinc layer is formed by dipping the zinc layer in an acidic zinc displacement plating solution containing hydrofluoric acid and ammonium fluoride, to form a connecting metal layer. It is characterized in that the photosensitive resin layer is removed after being formed by an electroless plating method.

The zinc displacement plating solution of the present invention is prepared by adding ammonium fluoride to the zinc displacement plating solution containing hydrofluoric acid in order to enhance the hydrofluoric acid resistance of the photosensitive resin, which is a pretreatment for electroless plating. Used to.

[0013]

EXAMPLES The effects of the present invention will be described below based on examples.

(Embodiment 1) FIG. 1 is a sectional view of an electrode manufactured in the present embodiment 1. It is composed of a silicon substrate 1, a first insulating layer 2 made of silicon oxide, a conductive layer 3 made of aluminum, a second insulating layer 4 made of alkoxide or polyimide, a nickel-phosphorus layer 5 and a connecting metal layer of a gold layer 6. The electrode structure is

2 to 4 are cross-sectional views for each step relating to the method of manufacturing the electrode of this embodiment. First, as shown in FIG. 2, a conductive layer 3 made of aluminum and having a thickness of about 1 micron was formed on a silicon substrate 1 on which a first insulating layer 2 was formed by a sputtering method or a vapor deposition method. Then, a second insulating layer 4 of about 1 micron of silicon oxide containing polyimide or boron, polyimide or silicon nitride is formed by spin coating or CVD method, and a plurality of 40 micron-spaced, 20 micron-square electrode planned portions are photoed. It was processed by the lithography method and the etching method.

Next, as shown in FIG. 3, a photosensitive resin 8 was applied to a portion other than the electrode planned region, and a zinc layer 7 was plated on the conductive layer 3 using an acidic zinc displacement plating solution having the following composition.

<Acid Zinc Substitution Plating Solution> Zinc sulfate 820 g / l Hydrofluoric acid (48%) 17 ml / l Ammonium fluoride 10 g / l Temperature 25 degrees Celsius Time 90 seconds At this time, the amount of aluminum etching is small, Upon observation, a dense zinc film was formed.

Next, as shown in FIG. 4, a nickel / phosphorus layer 5 as a connecting metal layer was formed to a thickness of about 20 μm by the following electroless nickel / phosphorus plating solution.

<Plating Composition> Nickel Sulfate Hexahydrate 30 g / l Sodium Hypophosphite Dihydrate 10 g / l Trisodium Citrate Dihydrate 10 g / l Ammonium Sulfate 66 g / l Thiodiglycolic Acid 10 ppm <Plating conditions> pH 5.5 Temperature 70 degrees (Celsius) Subsequently, the gold layer 6 was about 5 by using a known electroless gold plating solution.
The photosensitive resin layer 8 was peeled off by the displacement plating of 00 angstrom to complete the electrode.

The variation in electrode height of this embodiment is small,
It had a good electrode structure.

(Embodiment 2) First, a conductive layer made of aluminum and having a thickness of about 1 micron is formed on a silicon substrate having a first insulating layer formed thereon by a sputtering method or a vapor deposition method. Then, a second insulating layer of silicon oxide containing polyimide or boron of about 1 micron, polyimide or silicon nitride is formed by spin coating or CVD method, and a plurality of electrode portions having a 20 micron interval and 50 micron square are to be photolithographically formed. Processed by the etching method and the etching method.

Next, a photosensitive resin was applied to a portion other than the electrode planned area up to a predetermined electrode height, and a zinc layer was plated on the conductive layer using an acidic zinc displacement plating solution having the following composition.

<Acidic zinc displacement plating solution> Zinc sulfate 700 g / l Hydrofluoric acid (48%) 15 ml / l Ammonium fluoride 10 g / l Temperature 15 degrees Celsius Treatment time 60 seconds Since this plating solution is acidic, the resin is It did not melt, and zinc could be subjected to displacement plating. Next, an electroless nickel / boron plating solution described below was used to form a nickel / boron layer, which is a connecting metal layer, to a thickness of about 20 μm to complete the electrode.

<Plating Composition> Nickel Sulfate Hexahydrate 30 g / l DMAB 5 g / l Sodium Citrate 50 g / l <Plating Conditions> pH 7 Temperature 70 ° C. (degrees Celsius) The electrode of this example has a narrow pitch. However, the electrodes did not come into contact with each other. In addition, the height variation of the electrodes was small.

(Embodiment 3) First, an aluminum layer having a thickness of about 1 micron is formed on a silicon substrate on which a first insulating layer is formed by a sputtering method or a vapor deposition method. Then, a second insulating layer of silicon oxide, polyimide or silicon nitride containing phosphorus or boron having a thickness of about 1 micron is formed by spin coating or a CVD method.
A portion of the electrode having a square of 0 micron was processed by a photolithography method and an etching method. Then, the following zinc displacement plating solution was used to perform displacement plating of zinc on the conductive layer made of aluminum.

<Acid Zinc Substitution Plating Solution> Zinc sulfate 600 g / l Hydrofluoric acid (48%) 20 ml / l Ammonium fluoride 5 g / l Temperature 10 degrees Celsius Treatment time 60 seconds At this time, the etching amount of aluminum was small, and this plating surface When observed, a dense zinc film was formed.

Next, a connection metal layer was formed to a thickness of about 20 μm using the following electroless nickel-rhenium-phosphorus plating solution.

<Plating Composition> Nickel Sulfate Hexahydrate 30 g / l Ammonium Perrhenate 0.1 g / l Sodium Hypophosphite Dihydrate 10 g / l Trisodium Citrate Dihydrate 10 g / l ammonium sulfate 66 g / l thiodiglycolic acid 10 ppm <plating conditions> pH 8.5 temperature 70 ° C. (celsius) Subsequently, a known electroless gold plating solution was used to form about 50 gold layers.
The electrode was completed by performing 0 angstrom displacement plating.

There is little variation in electrode height in this embodiment,
It had a good electrode structure. Furthermore, because it contains rhenium,
The corrosion resistance was good in a halogen ion atmosphere.

(Example 4) An electrode was completed in the same manner as in Example 2 except that the connection metal layer of Example 2 was changed to an electroless plating film of palladium / phosphorus having the following composition and conditions.

<Plating Composition> Palladium chloride 0.01 mol / l Sodium phosphite 0.02 mol / l Thiourea 10 mg / l Ethylenediamine 0.01 mol / l <Plating conditions> pH 6 temperature 70 ° C. (Example 5) An electrode was completed in the same manner as in Example 2 except that the connection metal layer of Example 2 was changed to an electroless gold plating film having the following composition and conditions.

<Plating composition> Potassium chloroaurate 2 g / l Potassium sulfite 30 g / l Thiourea 10 g / l Potassium sulfate 10 g / l <Plating conditions> Temperature: 70 degrees Celsius or more TAB connection was made by the method. And the minimum value of connection strength is 30
As a result of judging less than g / electrode as poor and 30 g / electrode or more as good, the electrodes of Examples 1 and 2 and 3 and 4 and 5 showed a good connection state as shown in Table 1.

[0033]

[Table 1]

Further, since there is little variation in the height of the electrodes of the embodiment, a good connection state can be obtained even by a flip chip method using a semiconductor element with an anisotropic conductive film or an anisotropic adhesive, and the temperature including TAB can be improved. Long-term reliability was examined by a cycle test and an electric humidity test, and they were all good.

It should be noted that the effects of this example were the same except for the zinc substitution, nickel plating solution composition, processing conditions, bump height, electrode composition and semiconductor substrate material shown in this example.

The electroless plating solution includes nickel-phosphorus, nickel-boron, nickel-phosphorus, palladium-phosphorus or nickel-boron plating solutions and tungsten.
Even the plating solution containing one or more metal ions of molybdenum, manganese, copper, palladium, cobalt, zinc, thallium, and bismuth did not change the effect.

With respect to the nickel plating solution, even if a known electroless plating solution composition or other commercially available plating solution is used other than this embodiment, the effect remains the same.

The zinc substitution method did not change the effect even if the substitution operation was performed twice or more.

Further onto the nickel alloy or gold plating,
Even when the solder was laminated by the electroless plating method or the dipping method in a molten solder bath, the effect on the connection was not changed.

[0040]

As described above, according to the present invention, by using an acidic zinc substitution solution containing hydrofluoric acid and ammonium fluoride in the production of an electrode, a photosensitive resin coated on a portion other than the electrode planned area is used. It has been possible to manufacture highly reliable electrodes without causing peeling during plating. Then, since the photosensitive resin other than the electrode planned portion is not peeled off during the plating process, a short circuit does not occur even in the electrode with a narrow interval, and stable connection can be realized in the TAB or flip chip connection method. ..

[Brief description of drawings]

FIG. 1 is a sectional view of an electrode according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the manufacturing process of the electrode according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view of the manufacturing process of the electrode according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view of the manufacturing process of the electrode according to the first embodiment of the present invention.

[Explanation of symbols]

 1 Silicon Substrate 2 First Insulating Layer 3 Conductive Layer 4 Second Insulating Film 5 Nickel Phosphorus Layer 6 Gold Layer 7 Zinc Layer 8 Photosensitive Resin Layer

Claims (1)

[Claims] 1. A conductive layer made of aluminum is laminated on a semiconductor substrate with a first insulating layer interposed therebetween, and a portion other than a predetermined electrode region is covered with a second insulating layer, and then a zinc layer is formed on the conductive layer in the predetermined electrode region. In a method of manufacturing an electrode in which a connection metal layer for plating an electric connection on the zinc layer is laminated, a photosensitive layer is formed on a conductive layer and a second insulating layer made of aluminum other than a predetermined electrode region on a semiconductor substrate. Conductive resin layer is applied, the zinc layer is formed by dipping in an acidic zinc displacement plating solution containing hydrofluoric acid and ammonium fluoride, and a connecting metal layer is formed by electroless plating, and then the photosensitive resin is formed. A method for manufacturing an electrode, wherein the layer is removed.