Semiconductor device with recess portion over pad electrode

Abstract

A manufacturing method of a semiconductor device formed in a chip size package is improved to enhance a yield and reliability. A window to expose first wirings is formed only in a region of a semiconductor substrate where the first wirings exist. As a result, area of the semiconductor substrate bonded to a supporting body through an insulation film and a resin is increased to prevent cracks in the supporting body and separation of the semiconductor substrate from the supporting body. A slit is formed along a dicing line after forming the window, the slit is covered with a protection film and then the semiconductor substrate is diced into individual semiconductor dice. Thus, separation on a cut surface or at an edge of the semiconductor dice, which otherwise would be caused by contact of the blade in the dicing can be prevented.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a semiconductor device and manufacturing method thereof, specifically to a semiconductor device encapsulated in a package having roughly the same outside dimensions as a semiconductor die packaged in it and a manufacturing method thereof.

2. Description of the Related Art

A CSP (Chip Size Package) has received attention in recent years as a new packaging technology. The CSP means a small package having about the same outside dimensions as those of a semiconductor die packaged in it. A BGA type semiconductor device has been known as a kind of CSP. A plurality of ball-shaped conductive terminals made of metal such as solder is arrayed in a grid pattern on one principal surface of a package of the BGA type semiconductor device and is electrically connected with the semiconductor die mounted on the other side of the package.

When the BGA type semiconductor device is mounted on electronic equipment, the 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 semiconductor device has advantages in providing a large number of conductive terminals and in reducing size over other CSP type semiconductor devices such as an SOP (Small Outline Package) and a QFP (Quad Flat Package), which have lead pins protruding from their sides. The BGA type semiconductor device is used as an image sensor chip for a digital camera incorporated into a mobile telephone, for example.

FIGS. 13A and 13B show outline structure of a conventional BGA type semiconductor device. FIG. 13A is an oblique perspective figure showing a top side of the BGA type semiconductor device. And FIG. 13B is an oblique perspective figure showing a back side of the BGA type semiconductor device.

A semiconductor die 101 is sealed between a first glass substrate 104a and a second glass substrate 104b through resins 105a and 105b in the BGA type semiconductor device 100. A plurality of ball-shaped conductive terminals (hereafter referred to as conductive terminals) 111 is arrayed in a grid pattern on a principal surface of the second glass substrate 104b, that is, on a back surface of the BGA type semiconductor device 100. The conductive terminals 111 are connected to the semiconductor die 101 through a plurality of second wirings 109. The plurality of second wirings 109 is connected with aluminum first wirings pulled out from inside of the semiconductor die 101, making each of the conductive terminals 111 electrically connected with the semiconductor die 101.

More detailed explanation on a cross-sectional structure of the BGA type semiconductor device 100 is given hereafter referring to FIG. 14. FIG. 14 shows a cross-sectional view of the BGA type semiconductor devices 100 divided along dicing lines into individual dice.

The first wiring 103 is provided on an insulation film 102 on a top surface of the semiconductor die 101. The semiconductor die 101 is bonded to the first glass substrate 104a with the resin 105a. A back surface of the semiconductor die 101 is bonded to the second glass substrate 104b with the resin 105b. One end of the first wiring 103 is connected to the second wiring 109. The second wiring 109 extends from the end of the first wiring 103 to a surface of the second glass substrate 104b. The ball-shaped conductive terminal 111 is formed on the second wiring 109 extending onto the second glass substrate 104b.

The semiconductor device described above has disadvantages of increased thickness and higher manufacturing cost, since it uses two glass substrates. So, a method to bond the glass substrate only to the top surface of the semiconductor die, on which the first wiring is formed, has been considered. In this case, the bottom surface of the device is made of the semiconductor substrate which is easier to process by etching compared with the glass substrate. Taking this advantage, the first wiring is exposed by etching the semiconductor substrate and the insulation film in the dicing line region in order for the first wiring to be connected with the second wiring. As a result, a contact area between the first wiring and the second wiring is increased, compared with the conventional method using two glass substrates. After forming the second wirings, a protection film and the conductive terminals, the semiconductor substrate is finally separated into individual semiconductor dice by cutting the glass substrate.

The insulation film formed on the semiconductor substrate is left exposed in the dicing line region after the first wiring is exposed. At that time, only the insulation film, the resin and the glass substrate exist in the dicing line region. Considering thickness of each component, all of the semiconductor dice are supported practically only with the glass substrate. Furthermore, considerable warping is caused in the glass substrate, because of the difference in thermal expansion coefficients between the semiconductor substrate and the glass substrate. Therefore, weights of the semiconductor dice and others bonded to the glass substrate are imposed on the glass substrate during handling in the manufacturing process. In some cases, this may cause separation 204 between the semiconductor die and the glass substrate (not shown) in peripheral regions of the semiconductor dice and cracks 205 in the glass substrate 202, as shown in FIG. 11. Thus, the yield and reliability of the semiconductor devices have been reduced.

SUMMARY OF THE INVENTION

The invention provides a method of manufacturing a semiconductor device. The method includes providing a semiconductor substrate having a plurality of semiconductor dice, a boundary region between two of the semiconductor dice, an insulation film formed on a surface of the semiconductor substrate to cover at least the boundary region, and a pair of wirings formed on the insulation film so that the a center of the boundary region is located between the pair of wirings. The method also includes bonding a supporting body to the surface of the semiconductor substrate to cover the pair of wirings, and forming an opening in the semiconductor substrate so as to expose the insulation film between the pair of wirings and to expose at least part of the insulation film that is under the pair of wirings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a manufacturing method of a semiconductor device according to an embodiment of this invention.

FIGS. 2A and 2B are cross-sectional views showing the manufacturing method of the semiconductor device according to the embodiment of this invention.

FIGS. 3A and 3B are cross-sectional views showing the manufacturing method of the semiconductor device according to the embodiment of this invention.

FIGS. 4A and 4B are cross-sectional views showing the manufacturing method of the semiconductor device according to the embodiment of this invention.

FIGS. 5A and 5B are cross-sectional views showing the manufacturing method of the semiconductor device according to the embodiment of this invention.

FIGS. 6A and 6B are cross-sectional views showing the manufacturing method of the semiconductor device according to the embodiment of this invention.

FIGS. 7A and 7B are cross-sectional views showing the manufacturing method of the semiconductor device according to the embodiment of this invention.

FIGS. 8A and 8B are cross-sectional views showing the manufacturing method of the semiconductor device according to the embodiment of this invention.

FIGS. 9A and 9B are cross-sectional views showing the manufacturing method of the semiconductor device according to the embodiment of this invention.

FIGS. 10A and 10B are cross-sectional views showing the manufacturing method of the semiconductor device according to the embodiment of this invention.

FIG. 11 is a plan view showing a BGA type semiconductor device intermediate according to conventional art.

FIG. 12 is a plan view showing the semiconductor device intermediate according to the embodiment of this invention.

FIGS. 13A and 13B are oblique perspective views showing the BGA type semiconductor device according to the conventional art.

FIG. 14 is a cross-sectional view showing the BGA type semiconductor device according to the conventional art.

DETAILED DESCRIPTION OF THE INVENTION

Next, a manufacturing method of a semiconductor device according to an embodiment of this invention will be described referring to cross-sectional views shown in FIG. 1 through FIG. 10 and a plan view shown in FIG. 12 of the semiconductor device.

First, a semiconductor substrate 1 is provided, as shown in FIG. 1. CCD image sensors or semiconductor memories, for example, are formed in the semiconductor substrate 1 through semiconductor wafer processing. A pair of first wirings 3 separated by a predetermined spacing is formed on a surface of the semiconductor substrate 1 through a first insulation film 2 around a border (also referred to as a dicing line or a scribe line) S to divide the semiconductor substrate 1 into individual semiconductor dice. Each of the pair of first wirings 3 makes a pad extending from a bonding pad in the semiconductor device to proximity of the border S. That is, each of the pair of first wirings 3 is a pad for external connection, and is electrically connected with a circuit (not shown) in the semiconductor device.

Next, a glass substrate 4 is provided as a supporting body and is bonded to a surface of the semiconductor substrate 1 on which the first wirings 3 are formed, using a transparent resin 5 (an epoxy resin, for example) as an adhesive. Note that a silicon substrate or a plastic plate may be used as the supporting body other than the glass substrate used in the embodiment. An adhesive suitable for the chosen supporting body is to be selected in this case.

Thickness of the semiconductor substrate 1 is reduced by back-grinding a surface of the semiconductor substrate 1, which is opposite from the surface facing the glass substrate 4. Scratches arise on the back-ground surface of the semiconductor substrate 1, causing bumps and dips of several micrometers in width and in depth. In order to reduce the bumps and dips, the back-ground surface is wet-etched using a chemical solution having a high selection ratio between an etching rate for silicon which is a material of the semiconductor substrate 1 and an etching rate for silicon oxide which is a material of the first insulation film 2.

There is no specific restriction on the chemical solution as long as it has a high selection ratio. For example, a mixed solution composed of 2.5% of hydrofluoric acid, 50% of nitric acid, 10% of acetic acid and 37.5% of water is used as the etching solution in this embodiment.

Although doing the wet-etching is preferable, this invention does not necessarily include the wet-etching.

Next, the semiconductor substrate 1 is etched isotropically (or anisotropically) to expose portions of the first wirings 3, using a mask of photoresist (not shown) formed on the surface of the semiconductor substrate 1 opposite from the surface facing the glass substrate 4, as shown in FIGS. 2A and 2B. As a result, a window 20 opened along a border S in a region around the first wirings 3 is formed to expose the first insulation film 2, as shown in FIG. 2A. On the other hand, the semiconductor substrate 1 remains intact in a region where the first wiring does not exist, as shown in FIG. 2B.

The area of the semiconductor substrate 1 bonded to the glass substrate 4 through the first insulation film 2 and the resin 5 is still maintained large by forming the windows 20 which are opened only in the regions around the first wirings 3, as described above. Strength to support the glass substrate 4 is stronger than the conventional method. Also, warping of the glass substrate 4 due to the difference in thermal expansion coefficients between the semiconductor substrate 1 and the glass substrate 4 is reduced as well as cracks and separation in the semiconductor device.

FIG. 12 shows a plan view of the device intermediate at the process step of FIGS. 2A and 2B. Only a portion of a semiconductor substrate in the region under and between the pair of first wirings 301 is removed by etching instead of the whole scribe line region 304. The portion removed by the etching is called a window 303, which corresponds to the window 20 shown in FIG. 2A. As a result, most area of a supporting body is in contact with the semiconductor substrate 302 through the resin and the insulation film.

Note that the etching may be performed either by dry-etching or by wet-etching. In explanations on the manufacturing process hereafter, symbol A denotes a figure showing the region where the window 20 is formed, while symbol B denotes a figure showing the region where the window 20 is not formed, as in the case of FIG. 2A and FIG. 2B.

There are bumps and dips, residues and foreign particles on the surface of the semiconductor substrate 1. In addition, there are sharp edges at corners of the window 20, as shown in circles denoted 1a and 1b in FIG. 2A.

Wet-etching is made to remove the residues and the foreign particles and round the sharp edges, as shown in FIGS. 3A and 3B. With this, the sharp edges shown in the circles 1a and 1b in FIG. 2A are smoothed out, as shown in circles 1a and 1b in FIG. 3A.

Next, a second insulation film 6 is formed on the surface of the semiconductor substrate 1 opposite from the surface facing the glass substrate 4, as shown in FIGS. 4A and 4B. A silane-based oxide film of 3 μm in thickness is formed in this embodiment.

Next, a photoresist film (not shown) is applied above the surface of the semiconductor substrate 1 opposite from the surface facing the glass substrate 4 and pattering is made to form an opening in the photoresist film in the window 20 along the border S. Then portions of the first wirings 3 are exposed by etching the second insulation film 6 and the first insulation film 2 using the photoresist film (not shown) as a mask, as shown in FIGS. 5A and 5B.

Next, flexible cushioning pads 7 are formed at locations where conductive terminals 11 are formed later, as shown in FIGS. 6A and 6B. The cushioning pads 7 have function to absorb power applied through the conductive terminals 11 and relax stress when the conductive terminals 11 are bonded. However, this invention does not necessarily require including the cushioning pads 7.

A second wiring layer 8 is formed above the surface of the semiconductor substrate 1 opposite from the surface facing the glass substrate 4. With this, each of the first wirings 3 is electrically connected with the second wiring layer 8.

After that, a photoresist film (not shown) is applied above the surface of the semiconductor substrate 1 opposite from the surface facing the glass substrate 4. An opening is formed in the photoresist film in the window 20 along the border S in the region where the window 20 has been formed. On the other hand, the photoresist film is removed to expose the second wiring layer 8 in the region where the window 20 is not formed. Etching is performed using the photoresist film (not shown) as a mask to remove a portion of the second wiring layer 8 around the border S. Also, the second wiring layer 8 in the region where the window 20 is not formed is removed to complete the second wirings 8.

Next, a slit 30 (an inverted V-shaped groove) is formed in the glass substrate 4 along the border S so that the glass substrate 4 is cut to a depth of 30 μm, for example, as shown in FIGS. 7A and 7B.

That is, the resin 5 and a portion of the glass substrate 4 are cut to form the slit 30 in the region where the first wirings 3 exist (the region in the window 20 along the border S). It is necessary to use a blade of a width narrow enough not to contact the second wirings 8 in the window 20 in this process.

On the other hand, the semiconductor substrate 1, the first insulation film 2, the resin 5 and a portion of the glass substrate 4 are cut to form the slit 30 in the region where the first wiring 3 does not exist (i.e., the region where the window 20 is not formed).

Although the slit 30 has a wedge-shaped cross-section in the embodiment, it may have a rectangular cross-section. Besides, this invention does not necessary require the process step to form the slit 30.

Next, electroless plating is applied to the surface above the semiconductor substrate 1 opposite from the surface facing the glass substrate 4 to form a Ni—Au plating film 9 on the second wirings 8, as shown in FIGS. 8A and 8B. The film is formed only on the second wirings 8 because it is formed by plating.

Next, a protection film 10 is formed on a surface above the semiconductor substrate 1 opposite from the surface facing the glass substrate 4, as shown in FIGS. 9A and 9B. In order to form the protection film 10, the surface opposite from the surface facing the glass substrate 4 is held upward, a thermosetting organic resin is dropped on it and the organic resin is spread over the surface by spinning the semiconductor substrate 1 utilizing centrifugal force. With this, the protection film 10 is formed above the back surface of the semiconductor substrate 1 including a inner wall of the slit 30 formed along the border S.

In other words, the protection film 10 is formed to cover the second insulation film 6 and the resin 5 and the glass substrate 4 exposed on the inner wall of the slit 30 in the region where the first wirings 3 exist (the region in the window 20 along the border S). On the other hand, the protection film 10 is formed to cover the second insulation film 6, the semiconductor substrate 1, the first insulation film 2, the resin 5 and the glass substrate 4 exposed on the inner wall of the slit 30 in the region other than the region where the first wirings 3 exist (i.e. the region where the window 20 is not formed).

After that, portions of the protection film 10 above locations where the conductive terminals 11 are to be formed are removed by etching using a photoresist film (with openings at locations corresponding to the cushioning pads 7, not shown) as a mask and the conductive terminals 11 are formed on the Ni—Au plating film 9 at the locations corresponding to the cushioning pads 7. The conductive terminals 11 are electrically connected with the second wirings 8 through the Ni—Au plating film 9. The conductive terminals 111 are formed of solder bumps of gold bumps. When the gold bumps are used, thickness of the conductive terminal 11 can be reduced from 160 μm to several micrometers or several tens of micrometers.

Then the semiconductor substrate is diced into individual semiconductor dice along the border S at a portion where the slit 30 is provided, as shown in FIGS. 10A and 10B. A dicing blade preferably has a width to cut only the glass substrate 4 and the protection film 10 in the slit 30.

In the manufacturing method of the semiconductor device according to the embodiment, the dicing is performed in two steps, that is, the slit 30 is formed and then dicing is made after forming the protection film 10 to cover the slit 30. By doing so, separation can be made by dicing only the glass substrate 4 and the protection film 10, since the inner wall of the slit 30 formed along the border S (i.e. the dicing line) is covered with the protection film 10 when the dicing to separate the semiconductor device into the individual dice is performed. It means that the blade does not contact layers (the resin 5, the second wirings 8, etc.) and contacts only the glass substrate 4 and the protection film 10. Therefore, the separation caused in the separated semiconductor device, that is, on a cut surface or at an edge of the semiconductor dice by contacting the blade in the dicing process, can be prevented as much as possible.

As a result, yield and reliability of the semiconductor device can be improved. Also, the semiconductor device of this invention can be made thinner and produced at reduced cost, since it is formed of the single glass substrate.

Although the conductive terminals 11 electrically connected with the second wirings 8 are formed in this embodiment, this invention does not necessarily require the terminals. That is, this invention may be applied to a semiconductor device without the conductive terminals (an LGA (Land Grid Array) type package, for example).

Yield and reliability can be improved by preventing the cracks caused in the glass substrate and the separation in the peripheral regions of the semiconductor dice with this invention. In addition, the semiconductor device can be made thinner and produced at reduced cost, since a number of the glass substrates used in the device is reduced from two to one.

Claims

1. A semiconductor device comprising: a semiconductor die having an insulation film formed on a front surface thereof;a first wiring formed on the insulation film;a supporting body disposed on the insulation film and the first wiring;an adhesive layer attaching the supporting body to the front surface of the semiconductor die so as to cover all lateral edges of the first wiring;a recess portion formed in the semiconductor die and extending from a side of the semiconductor die horizontally with respect to the front surface and extending from a back surface of the semiconductor die vertically with respect to the front surface so as to extend into the supporting body; anda second wiring disposed in the recess portion so as to be connected to the first wiring; anda protection film disposed on the second wiring so as to be in contact with a side surface of the supporting body,wherein, in plan view of the semiconductor device, a length of the recess portion along said side of the semiconductor die is shorter than a length of the semiconductor die along said side of the semiconductor die, andin plan view of the semiconductor device a part of the first wiring is in the recess portion and not covered by the semiconductor die, and another part of the first wiring is covered by the semiconductor die.

2. The semiconductor device of claim 1, wherein part of the first wiring is disposed between the semiconductor die and the supporting body.

3. The semiconductor device of claim 2, wherein the length of the recess portion along said side of the semiconductor die is shorter than a length of the first wiring along said side of the semiconductor die so that both ends of the first wiring along said side of the semiconductor die are covered by the semiconductor die.

4. The semiconductor device of claim 2, wherein the recess portion extends horizontally so as not to reach a side of the first wiring that is normal to said side of the semiconductor die.