JPH05129304A - Structure of bump electrode and its manufacture - Google Patents

Abstract

PURPOSE:To enhance the mounting density of the title structure and to enhance the reliability of the structure after the structure has been mounted by a method wherein the structure is constituted of the following: a protrusion-shaped body which is formed on a circuit board and which has worked a single-crystal material by an anisotropic etching method; an insulating layer on the protrusion-shaped body; and a conductive layer on the insulating layer. CONSTITUTION:The structure of bump electrodes which electrically connect an electronic element to a circuit board 1 is constituted of the following: a protrusion-shaped body which is formed on the circuit board 1 and which has worked a single-crystal material by an anisotropic etching method; an insulating layer 4 on the protrusion- shaped body; and a conductor layer 5 on the insulating layer 4. For example, an Si substrate 1 whose surface has been polished and which is provided with a (100) orientation is thermally oxidized; an oxide film 2 in about 1mum is formed. Then, the oxide film 2 is etched so that protrusions about 20mum square can be formed at a pitch of about 60mum; the film is etched by 20mum by using the aqueous solution of KOH so that Si (111) orientation crystal faces 3 are exposed. Then, an insulating film composed of an oxide film 4 is formed; after that, an Al layer 5 as a conductive layer is plated; a circuit is formed by a photolithographic method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a protruding electrode for connecting an electronic device to a circuit board and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, a drastic improvement in circuit packaging density has been required due to improvements in fine processing technology for semiconductor devices and higher functionality of products using the same. For realization, a mounting method has been considered in which a protruding electrode (bump) is formed on a semiconductor electrode or an electrode on a circuit board by a plating method or the like, and a semiconductor element is directly connected to the circuit board.

[0003]

However, the conventional techniques have not been satisfactory in terms of improvement in packaging density. In the bump manufactured by the conventional plating method or the like, when the electrodes come close to each other, the plating grows in the lateral direction to short-circuit the electrodes, making it impossible to reduce the connection pitch. As a countermeasure, there is a method of forming a photosensitive resin up to the electrode height in a plating process to prevent lateral plating growth.
However, this method has a problem that when the bump becomes smaller, the ratio of the film thickness of the photosensitive resin to the diameter of the electrode approaches 1, and the pattern cannot be accurately developed.

Further, since the bumps formed on the semiconductor element are formed on the semiconductor element by a treatment such as plating, the manufacturing process of the semiconductor element is lengthened, and there is an anxiety factor that reduces reliability.

The present invention solves these problems, and an object thereof is to form a protrusion shape on the circuit board side without depending on the plating method, and to realize fine connection and improve the reliability of mounting.

[0006]

The structure of the protruding electrode of the present invention is the structure of the protruding electrode for electrically connecting an electronic element and a circuit board, and is formed on the circuit board by anisotropic etching of a single crystal material. It is characterized in that it is composed of a protrusion-shaped body processed by the method, an insulating layer on the protrusion-shaped body, and a conductive layer on the insulating layer.

Further, in the structure of the protruding electrode for electrically connecting the electronic element and the circuit board, the protruding electrode is formed on the circuit board,
It is characterized in that it is composed of an insulating layer, a protrusion-shaped body obtained by processing a single crystal material by an anisotropic etching method on the insulating layer, and a conductive layer on the protrusion-shaped body.

The single crystal material is silicon or gallium arsenide. Further, the method of manufacturing a bump electrode according to the present invention is characterized in that the circuit board and the bump-shaped body are made of a silicon single crystal material, and the insulating layer is formed by high-temperature bonding of a silicon single crystal material with an oxide film or diffusion of oxygen ions And

Materials used in the present invention include silicon, gallium / arsenic, quartz, indium / phosphorus and the like.

The anisotropic etching method of the present invention is a processing method utilizing a mechanism in which the etching rate varies depending on the crystal plane orientation of a single crystal material, and uses a wet anisotropic etching method using an aqueous solution or reactive plasma. There is a dry etching method. For example, etching using silicon by a wet method is a high-concentration and high-temperature alkali metal or alkaline earth metal hydroxide such as lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, or barium hydroxide. To aqueous solution,
When a single crystal of silicon is dipped and etched, the etching rate of the (111) orientation, which is the crystal orientation of silicon, is remarkably slower than that of (110) or (100). Then, for example, when the thermal oxide film is patterned on the (100) substrate in the (110) direction as an etching mask, the etching is stopped in the (111) direction, and micron-precision machining is possible.
The etching mechanism does not change even if the crystal orientation of the substrate is (110), and the etching solution is a trace additive such as alcohol such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol, There is also a method of changing the etching rate ratio by adding a surfactant. In addition, gallium / arsenic is etched by a mixed solution of sulfuric acid and hydrogen peroxide, and other single crystal materials also have an etching aqueous solution capable of anisotropic etching.

As the conductive layer forming the circuit, a transparent conductive film of copper, aluminum, gold, silver, tin oxide or an indium oxide / tin alloy, a yttrium-based sintered body, a metal superconducting alloy film, or the like can be used. Further, there is also a method of electrical conductivity using ion implantation of boron or the like into a semiconductor such as silicon and diffusion.

[0012]

In the mounting method of the present invention, since the protruding electrode is formed on the substrate, the process of forming the protruding electrode on the semiconductor element can be omitted.
The reliability after mounting can be improved. Furthermore, by using the anisotropic etching technique as a method of processing the protruding electrodes, it is possible to form protruding electrodes having a narrower diameter and improve the packaging density.

[0013]

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

(Embodiment 1) FIG. 1 is a perspective view of a circuit board of this embodiment.

FIG. 2 is a sectional view of each step of this embodiment.
This embodiment will be described with reference to this figure.

First, as shown in FIG. 2 (a), a surface-polished (100) -oriented silicon substrate 1 having a thickness of about 600 μm.
Is thermally oxidized to form an oxide film 2 of about 1 micron.

Next, as shown in FIG. 2B, the oxide film is etched by photolithography and etching so that projections of about 20 μm square are formed at a pitch of about 60 μm, and water at 80 ° C. and 40 g / l is used. The potassium oxide aqueous solution was used to expose the silicon (111) oriented crystal plane 3 to 20
Micron etching processing was performed.

Next, as shown in FIG. 2C, an insulating layer made of an oxide film 4 was formed, and then an aluminum layer 5 was plated as a conductive layer to form a circuit by photolithography. Finally, the aluminum alloy electrode of the semiconductor element was connected to the protrusion directly or by using an anisotropic conductive film or an anisotropic conductive adhesive.

This connection was electrically good.

(Embodiment 2) FIGS. 3A to 3C are sectional views showing the steps of this embodiment. This embodiment will be described with reference to this figure.

First, a chromium layer 7 and a gold layer 8 are sputtered on a gallium / arsenic substrate 6 of (100) orientation having a thickness of about 600 microns as shown in FIG.

Next, as shown in FIG. 3B, the chrome layer 7 and the gold layer 8 are formed so that projections of about 20 μm square can be formed at a pitch of about 60 μm by photolithography and etching.
By etching, 1 part of sulfuric acid, 8 parts of hydrogen peroxide solution, 5 parts of pure water
A 20 micron etching process was performed so that the gallium / arsenic (111) crystal plane 9 was exposed with 0 part of the etching aqueous solution.

Next, after forming the insulating layer 10 as shown in FIG. 3C, an aluminum layer 11 was plated as a conductive layer, and a circuit was formed by a photolithography method.

Finally, the aluminum alloy electrode of the semiconductor element was connected to the protrusion directly or by using an anisotropic conductive film or an anisotropic conductive adhesive.

This connection was electrically good.

Example 3 A circuit board was manufactured in the same manner as in Example 1 except that the aluminum layer in Example 1 was changed to a laminated layer of chromium and gold, and the aluminum alloy electrode of the semiconductor element was brought into contact with the protruding portion. And connected.

This connection was electrically good.

(Embodiment 4) A thickness of 600 as in Embodiment 1
A silicon single crystal substrate having a micron (100) orientation was etched by about 20 microns by a photolithography method and an etching method using potassium hydroxide.

Next, electronic elements such as resistors, semiconductors and capacitors are formed by a conventional method for manufacturing a semiconductor device, and an aluminum layer is plated as a conductive layer in the same manner as in Example 1,
The circuit was formed by the photolithography method.

Finally, the aluminum alloy electrode of the semiconductor element was connected to the protrusion directly or by using an anisotropic conductive film or an anisotropic conductive adhesive.

This connection was electrically good.

(Embodiment 5) FIG. 4 is a sectional view of this embodiment.

As shown in FIG. 4, a selective conductive region 13 including a protrusion is formed on a silicon substrate 12 which has been subjected to the same etching process as that of the first embodiment by a photolithography method and implantation of boron ions. Next, a semiconductor element was brought into contact with this conductive region directly or through an anisotropic conductive film or an anisotropic conductive adhesive to realize electrical connection.

This connection was electrically good.

(Embodiment 6) FIGS. 5A to 5C are cross-sectional views of this embodiment in steps. This embodiment will be described with reference to this figure.

As shown in FIG. 5A, the silicon substrate 1
In the same manner as in Example 1, the protrusion shape was processed by using the substrate in which the oxide film 15 was bonded to silicon and the silicon with oxide film was formed by implantation of oxygen ions.

Then, as shown in FIG. 5B, an aluminum layer 16 was plated on the protrusions. The semiconductor element was connected to this directly or via an anisotropic conductive film or an anisotropic conductive adhesive.

This connection was electrically good.

(Comparative Example 1) FIG. 6 is a sectional view of each step of this comparative example. This comparative example will be described with reference to this figure.

First, as shown in FIG. 6A, an oxide film 18, an aluminum layer 19 and a gold layer 20 are formed on a mirror-polished silicon substrate 17 of about 600 microns.

Next, as shown in FIG. 6 (b), the aluminum layer 19 and the gold layer 20 are wired by the photolithography method, and the negative photosensitive resin 21 of about 1 micron is used to form the gold layer 2.
Selective conductive layer regions 22 are formed on the silicon at a pitch of about 60 microns.

Next, as shown in FIG. 6 (c), a gold layer 23 having a thickness of about 20 μm was formed on the conductive layer region 22 by an electrolytic plating method using the following known liquid containing a gold sulfite salt.

(Plating Solution Composition) Sodium gold sulfite 12 g / l Sodium sulfite 50 g / l Sodium citrate 50 g / l Sodium tetraborate 10 g / l (Plating conditions) Temperature 40 degrees Celsius Current density 0.3 A / dm2 At this time, the bump electrodes were electrically contacted by plating growth in the lateral direction.

Comparative Example 2 A conductive layer region was formed in the same manner as Comparative Example 1 except that the film thickness of the negative photosensitive resin 21 of Comparative Example 1 was changed to about 20 μm. Then, electrolytic gold plating was performed, but since the ratio of the photosensitive resin to the diameter of the conductive layer region was about 1, the photosensitive resin remained on the conductive layer region and gold could not be laminated.

As described above, the connection of the example was electrically good, but in the comparative example, a good product could not be obtained at the time of manufacturing the protruding electrode, such as electrical short circuit or plating failure.

Epoxy resin was applied to the connected portions of the circuit boards that had been connected in Examples 1 to 6 and evaluated for long-term reliability. The results are shown in Table 1.

[0047]

[Table 1]

In this example, the connection reliability was good even with such a narrow protruding electrode diameter.

The aluminum layer in this embodiment is copper,
Even transparent conductive films of gold, silver, tin oxide or indium oxide / tin alloy, yttrium-based sintered bodies, metal superconducting alloy films, tungsten, etc. do not change the effect of the present invention, and the forming method is sputtering, vapor deposition, CVD, electroplating, electroless plating, etc. may be used. The thick gold layer may be silver, copper, nickel alloy, cobalt alloy, or palladium alloy.

Further, in addition to silicon, gallium, and arsenic, indium, phosphorus, and quartz did not change the effect of the present invention.

In the anisotropic etching of silicon, the crystal orientation may be set to (110), and the etching solution may be alkali hydroxide such as sodium hydroxide, lithium hydroxide or cesium hydroxide, or a trace amount thereof in addition to potassium hydroxide. Even if the substance was replaced with methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, a fluorine-based surfactant or the like, the effect was not changed. Further, the effect was not changed even by the anisotropic etching technique using plasma such as CF4 gas.

[0052]

As described above, the bump electrode structure of the present invention has the effect of improving the packaging density because the bump electrodes are formed on the circuit board by the anisotropic etching method. Further, as compared with a mounting method using a semiconductor element with bumps, a bump manufacturing process on the semiconductor element side is not required. Therefore, the mounting cost can be reduced, the manufacturing process of the semiconductor element can be shortened, and the reliability can be improved. Further, since another electronic element can be formed on the circuit board, there is an effect that the packaging density as a circuit can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view of a circuit board according to a first embodiment of the present invention.

FIG. 2 is a sectional view of each step of Embodiment 1 of the present invention.

3A to 3C are cross-sectional views according to steps of a second embodiment of the present invention.

FIG. 4 is a sectional view of a fifth embodiment of the present invention.

5A to 5C are cross-sectional views according to steps of a sixth embodiment of the present invention.

6A to 6C are cross-sectional views according to steps of a comparative example of the present invention.

[Explanation of symbols]

 1 Silicon Substrate 2 Oxide Film 3 Silicon (111) Oriented Crystal Plane 4 Oxide Film 5 Aluminum Layer 6 Gallium / Arsenic Substrate 7 Chromium Layer 8 Gold Layer 9 Gallium / Arsenic (111) Crystal Plane 10 Insulating Layer 11 Aluminum Layer 12 Silicon Substrate 13 Conductive region 14 Silicon substrate 15 Oxide film 16 Aluminum layer 17 Silicon substrate 18 Oxide film 19 Aluminum layer 20 Gold layer 21 Photosensitive resin 22 Conductive layer region 23 Gold layer

Claims (4)

[Claims] 1. In a structure of a projection electrode for electrically connecting an electronic element and a circuit board, a projection-shaped body formed on the circuit board and processed by a single crystal material by an anisotropic etching method, and the projection-shaped body. A structure of a bump electrode, comprising: an insulating layer on the insulating layer; and a conductive layer on the insulating layer. 2. In a structure of a protruding electrode for electrically connecting an electronic element and a circuit board, an insulating layer formed on the circuit board and a single crystal material processed on the insulating layer by an anisotropic etching method. A structure of a projection electrode, comprising a projection-shaped body and a conductive layer on the projection-shaped body. 3. The structure of the bump electrode, wherein the single crystal material according to claim 1 is silicon or gallium arsenide. 4. The circuit board according to claim 2, wherein the projection-shaped body is made of a silicon single crystal material, and the insulating layer is formed by high-temperature bonding of a silicon single crystal material with an oxide film or diffusion of oxygen ions. Method for manufacturing bump electrode.