This application is based on Japanese Patent Application No. 2005-174921, the content of which is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a CSP type semiconductor device with high reliability and a manufacturing method thereof.
2. Description of the Related Art
CSP (Chip Size Package) has received attention as a new packaging technology in recent years. The CSP means a small package having almost the same outside dimensions as those of a semiconductor die packaged in it.
Conventionally, a BGA (Ball Grid Array) type semiconductor device has been known as a kind of CSP. Ball-shaped conductive terminals are provided in this BGA type semiconductor device, being electrically connected with pad electrodes on a semiconductor substrate.
When this BGA type semiconductor device is mounted on electronic equipment, a semiconductor die is electrically connected with an external circuit on a printed circuit board by compression bonding of the conductive terminals to wiring patterns on the printed circuit board.
Such a BGA type electronic device has advantages in providing a large number of conductive terminals and in reducing size over other CSP type semiconductor devices such as SOP (Small Outline Package) and QFP (Quad Flat Package), which have lead pins protruding from their sides. Therefore, the BGA type electronic device is broadly used as an image sensor chip for a digital camera incorporated into a mobile telephone or the like, for example.
Hereafter, the conventional BGA type semiconductor device will be described using figures (FIGS. 7 to 10). FIGS. 7 to 10 show cross-sectional views in process order.
First, a silicon oxide film 101 and an interlayer insulation film 102 (a polyimide type resin film, a PSG film, or the like) are formed on a semiconductor substrate 100 made of silicon (Si) or the like as shown in
A metal layer (aluminum layer) is then formed on the interlayer insulation film 102 and patterned using a mask (not shown) to form a pad electrode 103 on the interlayer insulation film 102.
Next, a passivation film 104 made of solder resist or the like is formed on the front side of the semiconductor substrate 100 including on the pad electrode 103, and exposure and development are performed to the passivation film 104, thereby forming an opening 105 exposing a predetermined surface of the pad electrode 103 as shown in
Then, a plating layer 106 having a layered structure of nickel (Ni) and gold (Au) is formed on the pad electrode 103 exposed in the opening 105 by an electrolytic plating method or an electroless plating method as shown in
A portion near an end portion of the pad electrode 103 is not covered with the plating layer 106, leaving an exposed portion 107. There can be various causes of the formation of this exposed portion 107. One example is that residues of the passivation film 104 are easy to remain on its sidewall (patterned surface) when the opening 105 is formed due to filler (additive) or the like added to the passivation film 104 for preventing the passivation film 104 from warping, and the residue makes the sidewall uneven, so that the plating layer 106 hardly adheres to the sidewall. It is noted that the exposed portion 107 means a portion exposing the pad electrode 103 between the passivation film 104 and the plating layer 106.
Next, a solder ball is fixed to a predetermined region of the plating layer 106 by an electrolytic plating method or an electroless plating method, thereby forming a conductive terminal 108 as shown in
It is possible to form the conductive terminal 108 by screen-printing solder and reflowing the solder by a heat treatment (solder bump).
The relevant technology is disclosed in Japanese Patent Application Publication No. 2000-299406.
In the described conventional BGA type semiconductor device, however, a substance such as moisture, chemicals, a corrosive gas, metal ions, or the like that causes corrosion infiltrates through the exposed portion 107 to corrode the pad electrode 103 and reduces the reliability of the semiconductor device.
The invention provides a semiconductor device that includes a semiconductor substrate, an insulation film disposed on the substrate, a pad electrode disposed on the insulation film, a first passivation film disposed on the insulation film and having an opening above the pad electrode so that an edge portion of the pad electrode is covered by the first passivation film, a plating layer disposed on the pad electrode in the opening, a conductive terminal disposed on the plating layer and electrically connected with the pad electrode, and a second passivation film disposed on the first passivation film and in contact with the conductive terminal.
The invention also provides a method of manufacturing a semiconductor device. The method includes providing a semiconductor substrate having an insulation film disposed thereon and an pad electrode disposed on the insulation film, forming on the insulation film a first passivation film covering an edge portion of the pad electrode, forming a plating layer on the pad electrode by an electrolytic plating method or an electroless plating method, forming a conductive terminal on the plating layer, and forming on the first passivation film a second passivation film so as to be in contact with the conductive terminal and to fill a gap between an edge portion of the plating layer and an edge portion of the first passivation film.
FIGS. 1 to 5 are cross-sectional views for explaining a semiconductor device of an embodiment of the invention and its manufacturing method.
FIGS. 6 is a plan view for explaining a semiconductor device of the embodiment and its manufacturing method.
FIGS. 7 to 10 are cross-sectional views for explaining a semiconductor device of a conventional art and its manufacturing method.
An embodiment of the invention will be described in detail referring to figures. FIGS. 1 to 5 are cross-sectional views shown in process order.
First, an insulation film 2 (e.g. a silicon oxide film formed by a thermal oxidation method or a CVD method) is formed on a semiconductor substrate 1 made of silicon (Si) or the like to have a film thickness of, for example, 2 μm as shown in
Although the interlayer insulation film 3 is formed for securing a withstand voltage in this embodiment since the withstand voltage may be not secured enough if only the insulation film 2 is formed there, it is possible to form a structure without the interlayer insulation film 3 in particular. The interlayer insulation film 3 can be made of a silicon oxide film, a silicon nitride film, a PSG film, a BPSG film, or the other insulation film by a CVD method or the like.
Next, a metal layer made of aluminum (Al), copper (Cu), or the like that is to be a pad electrode 4 is formed by a CVD method, a sputtering method, or the other deposition method, and then the metal layer is patterned using a mask (not shown), thereby forming the pad electrode 4 having a film thickness of, for example, 1 μm on the interlayer insulation film 3. The pad electrode 4 is an external connection pad connected with an input circuit or an output circuit (not shown) on the semiconductor substrate.
Next, a first passivation film 5 that covers an end portion of the pad electrode 4 and has an opening 6 on the pad electrode 4 is formed to have a thickness of, for example, 10 μm as shown in
Then, exposure and development are performed to the coated organic material to form the opening 6 exposing a predetermined surface of the pad electrode 4, and a heat treatment (post-bake) is performed thereto. The first passivation film 5 covers the interlayer insulation film 3 and the end portion of the pad electrode 4. This first passivation film 5 and a second passivation film 10 that will be described below stabilize the surface of the semiconductor substrate 1 and function as protection films protecting the pad electrode 4 from corroding or the like.
Next, a plating layer 7 is formed on the pad electrode 4 exposed in the opening 6 by layering a nickel (Ni) layer mainly made of nickel and a gold (Au) layer mainly made of gold in this order (a lower layer=a nickel layer, an upper layer=a gold layer) by an electrolytic plating method or an electroless plating method using the first passivation film 5 as a mask as shown in
Next, a solder ball is fixed to a predetermined region of the plating layer 7 by an electrolytic plating method using the plating layer 7 as a plating electrode, thereby forming a conductive terminal 9 as shown in
It is possible to form the conductive terminal 9 by screen-printing solder and reflowing this solder by a heat treatment (solder bump). An advantage of forming a solder bump as the conductive terminal 9 is to form a fine shaped terminal with high accuracy. The conductive terminal 9 can be made of gold and its material is not particularly limited.
Next, the second passivation film 10 (a repair passivation film) made of an organic material such as a polyimide type resin film or a solder resist film is formed on the semiconductor substrate 1 by a coating method to have a thickness of, for example, 10 μm as shown in
As described above, although there can be various causes of the formation of the exposed portion 8 (the influence of the filler or the adhesion state of the first passivation film 5 and the plating layer 7), this embodiment is not affected by these causes and can be broadly applied to a semiconductor device where the exposed portion 8 occurs eventually and its manufacturing method.
Although this embodiment is described as applied to the semiconductor device formed with the ball-shaped terminal 9, the structure of the embodiment can be applied to the semiconductor device without the ball-shaped terminal, for example, to a LGA (Land Grid Array) type semiconductor device.
Number | Date | Country | Kind |
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2005-174921 | Jun 2005 | JP | national |