JP2000195861A - Semiconductor device and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device suitable for an imaging device, such as a CCD and the like and a method of producing the same. SOLUTION: A semiconductor substrate 12 is etched on the rear surface opposite to the device forming surface, a through-hole 22 is formed opposite to a metal pad 20, a metal is deposited thereon by plating to form a bump 34. Since the bump 34 is formed on the rear surface of the substrate 12 and no obstacle is on the device forming surface, it is suitable for an imaging device. Instead of plating, a metal ball may be positioned and heat-treated on the through-hole 22, and the melt of the metal ball may be filled into the through- hole 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of a semiconductor device effective for an imaging device such as a medical CCD (Charge Coupled Device) which requires ultra-miniaturization and a method of manufacturing the same.

[0002]

2. Description of the Related Art Generally, in a semiconductor device, a metal pad (bonding pad) is formed on an element formation surface of a semiconductor substrate, and the semiconductor substrate is divided into chips, and then, for example, a wire bonding method or a bump method. Using such techniques, the leads or conductor patterns of the lead frame and the metal pads are electrically connected, sealed in a plastic or ceramic package, and shipped as a finished product.

FIG. 4 is a schematic view showing an example of the structure of a conventional semiconductor device. FIG. 1A shows a structure using a wire bond.
Are fixed on the lead frame 103 with the element formation surface facing upward.

[0004] A lead 102 is arranged around the semiconductor substrate 100, and a bonding pad 120 provided on the semiconductor substrate 100 is connected to the lead 102 by a bonding wire 121.

On the other hand, FIG. 1B shows a structure using a bump, in which a bump 131 formed on a bonding pad 130 is applied to a conductor pattern 104 formed on a circuit board. The bumps 131 are electrically and mechanically connected to the conductive pattern 104 by being brought into contact with each other and melting the bumps 131 by heat treatment.

However, according to the connection method using the bumps 130, since the element formation surface of the semiconductor substrate 101 cannot be turned upward, an imaging device such as a CCD cannot be assembled.

On the other hand, when the bonding wires 121 are used, the element forming surface of the semiconductor substrate 100 can be directed upward, but the entire semiconductor device becomes large. Also,
Since the bonding wires 121 exist on the semiconductor substrate 100, there is a problem that the bonding wires 121 diffusely reflect light and deteriorate light receiving characteristics of the semiconductor substrate 100.

Particularly, in recent years, medical CCDs such as endoscopes have been used.
Are required to be further reduced in size and higher in performance, but it is difficult to cope with the above-mentioned conventional connection technology.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned disadvantages of the prior art, and has as its object to make the apparatus ultra-small and not to cause irregular reflection of light. A semiconductor device and a method for manufacturing the same are provided.

[0010]

According to a first aspect of the present invention, there is provided a semiconductor device having a semiconductor substrate and a metal pad formed on a first surface side of the semiconductor substrate. In addition, a through hole is provided below the bottom surface of the metal pad of the semiconductor substrate on a second surface opposite to the first surface.

According to a second aspect of the present invention, in the semiconductor device according to the first aspect, the through hole is filled with a conductive material electrically connected to the bottom surface of the metal pad. I have.

According to a third aspect of the present invention, in the semiconductor device according to the second aspect, an insulating film is formed on the side wall of the through hole, and the conductive material is electrically insulated from the semiconductor substrate. It is configured.

According to a fourth aspect of the present invention, in the semiconductor device according to any one of the second and third aspects, the second conductive material is filled in the through hole.
Are formed on the surface side of.

According to a fifth aspect of the present invention, a metal pad is formed on the first surface side of a semiconductor substrate having first and second surfaces, and the semiconductor substrate is formed from the second surface side of the semiconductor substrate. A method of manufacturing a semiconductor device, wherein a substrate is partially etched to form a through hole at a position of a bottom surface of the metal pad.

According to a sixth aspect of the present invention, there is provided the semiconductor device manufacturing method according to the fifth aspect, further comprising a step of forming an insulating film on at least the side wall of the through hole.

According to a seventh aspect of the present invention, in the method of manufacturing a semiconductor device according to the fifth or sixth aspect, after exposing the bottom surface of the metal pad in the through hole, depositing a metal, There is a step of filling the holes.

The invention according to claim 8 is the method of manufacturing a semiconductor device according to claim 7, wherein a metal film is formed on the bottom surface of the metal pad exposed in the through hole, and the metal film is formed on the surface of the metal film. And a step of depositing a metal.

According to a ninth aspect of the present invention, there is provided the method of manufacturing a semiconductor device according to the fifth or sixth aspect, wherein a molten metal having a low melting point is poured into the through hole, and the low melting point metal is filled in the through hole. And a step of filling with a metal.

In the semiconductor device of the present invention, a metal pad is formed on the first surface side of the semiconductor substrate, and a through hole is provided below the bottom surface of the metal pad of the semiconductor substrate. This through hole is open on the second surface of the semiconductor substrate opposite to the first surface.

After exposing the bottom surface of the metal pad in the through hole or forming a metal film on the exposed surface,
When the through hole is filled with a conductive material such as a metal, the filled conductive material is electrically connected to the metal pad.

When the filled conductive material is connected to an external lead or a conductive pattern, the bonding pad can be electrically connected to an external circuit. If an insulating film is formed in the through hole, the filled conductive material and the semiconductor substrate can be electrically insulated.
If an insulating film is also formed on the second surface of the semiconductor substrate,
A short circuit between the conductive substance and the semiconductor substrate on the second surface side is eliminated.

Further, when the conductive material filling the through holes is raised on the second surface and bumps protruding from the second surface are formed, connection with the leads and the conductor pattern becomes easy.

In order to fill the through hole with a conductive material as described above, a metal is deposited by a plating method, or the second surface of the semiconductor substrate is directed upward, and a low melting point metal is placed on the through hole opening. Can be arranged, melted by heat treatment, and poured into through holes.

In any case, a metal film serving as a base layer for plating or a metal film having good adhesion to a low melting point metal can be formed on the metal pad exposed in the through hole.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor device according to the present invention will be described below with reference to an embodiment shown in the accompanying drawings, together with a method for manufacturing the same.

FIGS. 1 (a) to 1 (f) and 2 (g) to 2 (k) are process diagrams showing the manufacturing method of the present invention, and show the semiconductor substrate shown in FIGS. The semiconductor device of the present invention formed from 12 is shown in FIGS. 1 (d) to 1 (f) and 2 (g) to 2 (h).

Hereinafter, the above-described method of manufacturing a semiconductor device according to the present invention will be described with reference to sectional process diagrams shown in FIGS.

Referring to FIG. 1A, reference numeral 12 denotes a semiconductor substrate such as a silicon substrate in a wafer state, and a large number of electric elements (not shown) such as transistors are formed on the upper surface in the figure. ing. Assuming that the surface on which the electric element is formed is a first surface, an insulating film 14 is formed on the first surface, and an aluminum thin film is entirely formed on the insulating film 14. , Patterned, narrow internal wiring 16
, A large area metal pad 20 is formed.

Further, an insulating film (passivation film) 18 is formed on the surface of the insulating film 14, the internal wiring 16 and the metal pad 20.
Are formed.

Here, the internal wiring 16 and the metal pad 2
0 is formed from a single-layer aluminum thin film. The wiring 16 and the metal pad 20 are not limited to those having a single layer of aluminum. A multilayer structure in which one or a plurality of films of polysilicon, tungsten, titanium, or the like is formed under aluminum, or aluminum. Instead, it can be formed using copper. Further, the uppermost insulating film may be used as an interlayer insulating film, and an internal wiring may be further laminated on the surface thereof to form an internal wiring having a multilayer structure.

The electric elements formed on the semiconductor substrate 12 are connected to each other by such an internal wiring 16,
The electric circuits formed by them are likewise connected to the metal pads 20 by the internal wiring 16.

On the second surface (back surface) of the semiconductor substrate 12 opposite to the first surface, a CVD (Chemical Vapor Deposition) method is used.
position: a chemical vapor deposition method) or the like, an insulating film 24 such as a silicon oxide film is formed on the entire surface (FIG. 1B), and then a predetermined pattern is formed on the insulating film 24 by a photolithography process. A resist film 32 is formed (FIG. 1C).

The resist film 32 has an opening having a diameter smaller than that of the metal pad 32 at a position directly below the rear surface of the metal pad 32, and the insulating film 24 exposed at the bottom of the opening.
Is removed by wet or plasma etching,
Subsequently, the semiconductor substrate 12 is etched to form a through hole 22 (FIG. 1D).

In the etching, anisotropic dry etching using plasma can form the through-hole 22 with the highest accuracy. When the semiconductor substrate 12 is etched, the insulating film 14 serves as a stopper. ,
This is preferable because the vertical progress of the etching can be automatically stopped.

In this case, the surface of the insulating film 14 is exposed on the metal pad 20 on the bottom surface of the through hole 22.
The semiconductor substrate 12 is exposed on the side wall of the through hole 22.

Next, the photosensitive resist 32 is peeled and removed.
(FIG. 1E), the second semiconductor substrate 12 is formed by a CVD method or the like.
When an insulating film 26 such as a silicon oxide film is formed on the surface side of
The side wall of the through hole 22 is covered with the insulating film 26
(FIG. 1 (f)).

At this time, the second surface and the metal pad 20 are covered by the two layers of insulating films 14 and 26. In this state, the two layers of the insulating film 14 , 26 are stacked, and also on the second surface side of the silicon substrate 12, two layers of insulating films 24, 26 are stacked.

Although depending on the inner diameter of the through hole 22, the smaller the inner diameter, the smaller the through hole 22.
Is generally thinner than the second surface of the semiconductor substrate 12 or the side wall surface of the through hole 22.

Subsequently, the insulating film 26 is anisotropically etched by plasma etching so that the insulating film 26 formed on the side wall surface of the through hole 22 is left. When the 14 is removed, the bottom surface of the metal pad 20 is exposed (FIG. 2G).

The thickness of the insulating films 24 and 26 stacked on the second surface of the semiconductor substrate 12 is larger than the thickness of the insulating films 26 and 14 stacked on the bottom surface of the metal pad 20. The insulating films 24 and 26 remain not only in the insulating film 26 but also in a portion other than the through hole 22 on the second surface. In particular, when the through hole 22 has a small diameter, the insulating film 26 formed after the opening of the through hole 22 is thin on the bottom surface of the through hole 22. The insulating film 26 formed on the substrate remains.

In the present invention, the semiconductor substrate 12
Of the insulating films 24 and 26 deposited on the back surface of the second surface, at least the insulating film 24 formed before the opening of the through hole 22 should remain on the second surface side.
6 can be removed.

To ensure that the insulating film remains, in the semiconductor device shown in FIG. 1F, a patterned resist film is formed, and the insulating film 2 formed after the opening of the through hole 22 is formed.
It is preferable to perform anisotropic etching in the through hole 22 while protecting the portion on the second surface of No. 6.

After the bottom surface of the metal pad 20 is exposed, a metal film 28 is entirely formed on the second surface side of the semiconductor substrate 12 by a sputtering method or a vapor deposition method (FIG. 2).
(h)).

Next, a patterned resist film 34 is formed on the metal film 28 (FIG. 2 (i)). An opening is provided on the through hole 22 of the resist film 34, so that only the metal film 28 on the bottom surface of the through hole 22 is exposed.

Next, if necessary, the first
After a protective film such as a wax film is formed on the surface of the metal film 28 (a protective film is not formed here), when immersed in a plating solution, the surface of the metal film 28
(Conductive substance) is deposited, and the inside of the through hole 22 is filled with the metal. If the deposition is continued after filling the through holes 22 by controlling the plating time, the deposited metal protrudes from the second surface, and the bumps 30 are formed (FIG. 2).
(j)).

Next, when the resist film 34 and the metal film 28 are removed in this order, the semiconductor device 10 is obtained.
(k)). When a protective film such as wax is formed on the surface of the semiconductor substrate 12, the wax is also removed using a solvent or the like.

When the semiconductor device 10 is divided into chips, the bumps 30 of the semiconductor device 10 can be connected to leads or conductive patterns.

As described above, according to the semiconductor device manufacturing method of the present invention, the bump 3
Since 0 can be formed, the internal circuit can be connected to an external circuit by connecting the second surface side to a lead or a conductor pattern and connecting a bump. In that case, since there is no shield on the first surface side, it is suitable for a light receiving element such as a CCD.

When a low-melting-point metal such as solder is deposited by the above plating, the bump 30 is melted by heat treatment, and the bump 30 is connected to a lead or a conductor pattern. When the deposited metal is copper and the bump 30 is made of copper, the bump 30 can be connected to a conductor pattern or a lead using an anisotropic conductive film.

As the plating method, wet plating such as electrolytic plating and electroless plating can be used, and any other method that can fill the inside of the through hole with a conductive substance can be used in the present invention.

For example, a ball made of a conductive material may be arranged in the opening of the through hole 22, melted, and the inside of the through hole 22 may be filled with the conductive material.

FIG. 3 shows a method of manufacturing such a semiconductor device.
This will be described with reference to cross-sectional process diagrams shown in (g), (l), and (m).

FIG. 3 (g) shows the same state as that of FIG. 2 (g), that is, the state of FIG. In the semiconductor substrate 12, the insulating film 14 at the bottom of the through hole 22 is removed by etching, and the bottom of the metal pad 20 is exposed at the bottom of the through hole 22.

In this state, the ball 36 made of a low melting point metal such as solder is placed on the opening of the through hole 22 with the second surface side of the semiconductor substrate 12 facing upward (FIG. 3).
(h)).

In this state, when the ball 36 is heat-treated at a relatively low temperature to melt the ball 36, the melt flows into the through hole 22. Next, upon cooling, the inside of the through hole 22 is filled with the low melting point metal constituting the ball 36.

If the volume of the ball 36 is larger than the volume of the through hole 22, the melt rises on the second surface, and when cooled, the bump 30 'made of a low melting point metal.
Is obtained (FIG. 3 (i)).

When the semiconductor device 11 is divided into chips, the bumps 30 'can be connected to leads and conductive patterns.

A metal film having good adhesion to solder or the like is formed on the exposed bottom surface of the metal pad 20 so that the semiconductor substrate 12
After the unnecessary portion on the second surface is removed, if the melt of the ball 36 is poured, electrical and mechanical connection is ensured, which is convenient.

As described above, in the semiconductor device of the present invention, since there is no shield on the element forming surface side of the semiconductor substrate, for example, an effective area can be increased in an imaging device such as a CCD for medical use, and irregular reflection of light can be achieved. It is possible to manufacture a high-performance device without any problem.

Further, according to the semiconductor device and the method for manufacturing the same of the present invention, the entire surface of the element formation surface of the semiconductor substrate can be covered with the surface protective film, so that the reliability of the semiconductor device can be improved.

Further, since bumps serving as connection terminals with the outside are provided on the back side of the semiconductor substrate, wire bonding is not required in the assembling process, and a package having the same size as the semiconductor substrate divided into chips is formed in a package. It can also be sealed. Therefore, the semiconductor device of the present invention is extremely small.

Further, bumps are formed on the back surface of the semiconductor substrate and sealed, so that assembly is easy.

The semiconductor device according to the present invention includes not only a semiconductor device in a wafer state but also a semiconductor device divided into chips.
In addition, those in which it is sealed in a package are also included. It may be sealed together with another type of semiconductor substrate.

In the above, the metal is deposited by the plating method, and the through hole 22 is filled with the ball 34. However, the semiconductor in which the inside of the through hole 22 is filled with the metal or the conductive material by another method. A device manufacturing method and a semiconductor device are also included in the present invention.

[0065]

According to the present invention, the back side of the semiconductor substrate can be connected to leads or conductive patterns by a bump method, so that it can be sealed in a package with a size similar to the semiconductor substrate. Further, since there is no shield such as a bonding wire on the element forming surface, it is particularly effective for an imaging device such as a medical CCD.

[Brief description of the drawings]

1 (a) to 1 (f): First half of a process chart of a semiconductor device manufacturing method according to an example of the present invention.

FIG. 2 (g) to (k): latter half of the process diagram

FIGS. 3 (g), (l), and (m): process diagrams of another method for manufacturing a semiconductor device of the present invention.

4A and 4B are examples of a conventional semiconductor device.

[Explanation of symbols]

10 semiconductor device 12 semiconductor substrate 20
... Metal pad 22 ... Through hole 26 ... Insulating film 28 ... Metal film 30, 30 '... Bump

Continued on front page F-term (reference) 4M118 AA05 AA10 AB01 BA10 HA31 HA33 5F033 JJ07 JJ11 KK04 KK08 KK18 KK19 NN06 PP15 PP19 PP27 PP28 QQ07 QQ10 QQ12 QQ16 QQ21 QQ25 QQ30 QQ35 QQ37 QQ73 RR04 TT04

Claims (9)

[Claims] 1. A semiconductor device comprising: a semiconductor substrate; and a metal pad formed on a first surface side of the semiconductor substrate, wherein the semiconductor substrate has a first surface under a bottom surface of the metal pad.
A semiconductor device provided with a through-hole opening on a second surface opposite to the surface. 2. The semiconductor device according to claim 1, wherein said through hole is filled with a conductive material electrically connected to a bottom surface of said metal pad. 3. The semiconductor device according to claim 2, wherein an insulating film is formed on at least the side wall of the through hole, and the conductive material is electrically insulated from the semiconductor substrate. 4. The semiconductor device according to claim 2, wherein a bump protruding toward said second surface is formed by a conductive substance filled in said through hole. 5. A semiconductor substrate having first and second surfaces, a metal pad is formed on the first surface side of the semiconductor substrate, and the semiconductor substrate is partially etched from the second surface side of the semiconductor substrate. And forming a through hole at the bottom of the metal pad. 6. The method according to claim 5, wherein an insulating film is formed on at least the side wall of the through hole. 7. The method according to claim 5, wherein after exposing the bottom surface of the metal pad in the through hole, a metal is deposited to fill the through hole. 8. The method of manufacturing a semiconductor device according to claim 7, wherein after exposing the bottom surface of the metal pad in the through hole, a metal film is formed, and the metal is deposited on the surface of the metal film. 9. The method of manufacturing a semiconductor device according to claim 5, wherein a molten metal having a low melting point is poured into said through-hole, and said through-hole is filled with said metal having a low melting point.