JP2004047903A - Semiconductor device and its manufacture - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device and its manufacturing method by which grinding process of the underside of a semiconductor substrate can be performed properly by preventing the semiconductor substrate from warping and the strength of the semiconductor device having a reduced thickness can be maintained. <P>SOLUTION: Salient electrodes 2 are formed on the surface 1a of a wafer 1 (Fig.(a)). A low-elasticity first resin film 3 having a thickness of burying the tops of the salient electrodes 2 is formed on the surface 1a of the wafer 1 (Fig.(b)). The underside 1b of the wafer 1 is ground by using a grinder or the like (Fig.(d)). After grinding, a second resin film 4 exhibiting a high elasticity or a high hardness is formed. The superficial layer of the first resin film 3 is removed by etching or the like for exposing the tops of the salient electrodes 2 (Fig.(e)). The wafer 1 is divided by a dicing process for obtaining 5 pieces of semiconductor chips 5 (Fig. 1(f)). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a small and thin semiconductor device and a method for manufacturing the same.
[0002]
[Prior art]
2. Description of the Related Art In order to reduce the thickness of a semiconductor chip, a back surface grinding step of grinding a back surface side of a semiconductor wafer (hereinafter, simply referred to as a “wafer”) on which elements and wirings have been formed has been conventionally performed. In this backside grinding step, generally, a soft protective film is attached to the surface of the wafer, the wafer is pressed through the protective film, the backside of the wafer is pressed against a grindstone, and the wafer is rotated in that state. Has been done.
[0003]
However, in a process after grinding, for example, a cutting process for cutting individual chips from a wafer or a process of mounting the cut chips on a lead frame, the wafers and chips are handled by a robot. Therefore, if the thickness is excessively reduced, the wafer or chip may be damaged during handling, and the yield may be reduced. In particular, today, when the diameter of a wafer has been increased, a wafer thinned by back surface grinding may be easily damaged.
[0004]
In order to solve such a problem, for example, Japanese Patent Application Laid-Open No. H11-150090 discloses that after forming a group of protruding electrodes on the surface of a wafer, a resin film is formed on the surface of the wafer and the resin film is protected and strengthened. It has been proposed for use as a plate. In the method of manufacturing a semiconductor device disclosed in this publication, the back surface of the wafer is ground after the formation of the resin film, and the top portion of the bump electrode group is exposed by removing the surface layer portion of the resin film by etching. Has become. After that, the resin film is removed along the scribe line, and a nitride film as a protective film is formed in a region avoiding the protruding electrodes. After that, the wafer is cut along the scribe line, and individual chips are cut. Is cut out.
[0005]
In this method, the wafer after the back surface grinding is reinforced by the resin film, and individual chips cut from the wafer are also reinforced by the resin film. Thereby, the wafer and the chip can be satisfactorily handled without causing the breakage thereof. In addition, since such a chip can be mounted by connecting the top of the exposed protruding electrode to an electrode pad or the like of a wiring board, the semiconductor device is compared with a configuration in which external terminals are pulled out using wire bonding or the like. Can be significantly reduced in thickness.
[0006]
[Problems to be solved by the invention]
However, in the above-mentioned prior art manufacturing method, the difference between the thermal expansion / shrinkage ratio between the wafer and the resin film between the time when the resin film is formed on the wafer surface and the time when the back surface grinding is performed is caused by the difference in FIG. As shown exaggeratedly, there is a problem that the wafer is warped. Grinding the warped wafer with a flat grindstone causes a difference in the thickness of the ground wafer between the central region and the peripheral region of the wafer, so that a semiconductor chip having a uniform thickness can be obtained. In addition to the loss, the semiconductor chips cut out from the peripheral region of the wafer may not be thinned to the expected thickness. In addition, the thinned wafer is separated into individual pieces by a process of laminating an adhesive tape called a dicing tape into individual pieces called a dicing process. Since the semiconductor substrate is singulated, scratches or microcracks called chipping occur at the singulated corners of the semiconductor substrate. The semiconductor substrate that has been singulated later can be completely singulated by pushing up the back of the dicing tape with a needle and peeling it off from the tape. In addition, the completed semiconductor device also tends to be scratched with the back surface opposite to the active surface of the semiconductor substrate exposed, which lowers the reliability.
[0007]
Therefore, an object of the present invention is to solve the above-mentioned technical problems and prevent the semiconductor substrate from warping, thereby enabling the back surface grinding process of the semiconductor substrate to be favorably performed, and the low-strength grinding by thinning. An object of the present invention is to provide a thin and high-strength semiconductor device and a method of manufacturing the same by increasing the strength of a later wafer.
Another object of the present invention is to provide a semiconductor device having a configuration that can be easily reduced in size and thickness.
[0008]
Means for Solving the Problems and Effects of the Invention
According to a first aspect of the present invention, there is provided a semiconductor substrate, at least one of a protruding electrode or a wiring formed on one surface of the semiconductor substrate, and a first resin film formed on one surface of the semiconductor substrate. Wherein the first resin film has low elasticity to the extent that stress due to a difference in thermal expansion coefficient with the semiconductor substrate is reduced.
[0009]
According to the present invention, since the low elastic resin film is formed on the first resin film formed on one surface of the semiconductor substrate, warpage due to a difference in thermal expansion / contraction between the semiconductor substrate and the resin film is reduced. Does not occur. This allows the back surface of the semiconductor substrate to be uniformly ground while the semiconductor substrate is flat. Therefore, by such a method for manufacturing a semiconductor device, it is possible to obtain a semiconductor substrate having a uniform thickness adjusted to a desired thickness. That is, since the obtained semiconductor substrate is uniformly thinned in both the central region and the peripheral region, a thin semiconductor chip having a uniform thickness is obtained by cutting individual semiconductor chips from the semiconductor substrate. Can be obtained. Further, even in the completed semiconductor substrate, there is no warpage due to the difference in thermal expansion / contraction between the semiconductor substrate and the resin film.
[0010]
According to a second aspect of the present invention, there is provided a semiconductor substrate, at least one of a protruding electrode or a wiring formed on one surface of the semiconductor substrate, and a first resin film formed on one surface of the semiconductor substrate. Wherein the elastic modulus of the first resin film is 5 GPa or less.
[0011]
According to the present invention, by setting the elastic modulus of the first resin film to 5 GPa or less, warpage due to a difference in thermal expansion / contraction between the semiconductor substrate and the resin film does not occur. Therefore, the same effect as the first aspect is obtained.
[0012]
Further, a second resin film having higher elasticity or higher strength than the first resin film may be formed on the other surface of the semiconductor substrate. Further, it is more preferable that the elastic modulus of the second resin film is 10 GPa or more. By doing so, the strength of the reduced semiconductor device can be increased by grinding the back surface of the semiconductor substrate. It is more preferable that the semiconductor substrate has a thickness of 400 μm or less. It is even more preferable that the semiconductor substrate has a thickness of 200 μm or less and is formed at the center in the thickness direction of the semiconductor device in a sectional structure.
[0013]
According to a seventh aspect of the present invention, there is provided a semiconductor device comprising: a step of forming at least one of a protruding electrode and a wiring on one surface of a semiconductor substrate; Forming a first resin film having low elasticity on the active surface side so as to reduce stress due to a difference in thermal expansion coefficient from the semiconductor substrate, and polishing or grinding the other surface of the semiconductor substrate; A step of forming a second resin film having a higher elasticity or a higher hardness than the first resin film on the ground surface after the grinding step of reducing the thickness of the semiconductor substrate; (2) a step of cutting out into individual pieces after forming the resin film.
[0014]
According to the present invention, since the low elastic resin layer is formed on the first resin film formed on one surface of the semiconductor substrate, warpage due to a difference in thermal expansion / contraction between the semiconductor substrate and the resin film is reduced. Does not occur. This allows the back surface of the semiconductor substrate to be uniformly ground while the semiconductor substrate is flat. Therefore, by such a method for manufacturing a semiconductor device, it is possible to obtain a semiconductor substrate having a uniform thickness adjusted to a desired thickness. That is, since the obtained semiconductor substrate is uniformly thinned in both the central region and the peripheral region, a thin semiconductor chip having a uniform thickness is obtained by cutting individual semiconductor chips from the semiconductor substrate. Can be obtained. Further, even in the completed semiconductor substrate, there is no warpage due to the difference in thermal expansion / contraction between the semiconductor substrate and the resin film. Furthermore, since the second resin film having higher elasticity or higher hardness than the first resin film is formed on the other surface of the semiconductor substrate, grinding the back surface of the semiconductor substrate can reduce the strength of the semiconductor device. Strength can be increased.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is an illustrative sectional view showing a method for manufacturing a semiconductor device according to an embodiment of the present invention in the order of steps. The semiconductor wafer 1 of FIG. 1 (hereinafter simply referred to as “wafer 1”) has undergone various element forming steps, wiring steps, and the like, and the surface 1a on the active surface layer side is a protective film made of a nitride film or the like. (Passivation film). A pad for electrical connection with the outside is exposed from the protective film.
[0016]
As shown in FIG. 1A, a plurality of protruding electrodes 2 made of, for example, gold (Au) are formed on the pad. The protruding electrode 2 is formed, for example, by electrolytic plating, and its height from the surface of the protective film is preferably, for example, about 50 μm. It is preferable that the protruding electrodes 2 have a columnar shape such as a columnar shape or a square columnar shape. As the material, copper, solder, or the like can be used in addition to gold. In addition, scribe lines are formed on boundaries (positions indicated by arrows A in FIG. 1) of the individual semiconductor elements on the surface 1a of the wafer 1.
[0017]
Next, a first resin film 3 is formed on the front surface 1a of the wafer 1 (FIG. 1B). The first resin film 3 can be obtained by applying a liquid resin by a screen printing method, a spin coating method, a bar coating method, or the like, and then curing the resin. The type of resin can be polyimide, epoxy, or the like. It is preferable that the cured first resin film 3 (hereinafter, simply referred to as “first resin film 3”) be formed to have a thickness that allows the protruding electrode 2 to be buried. Specifically, the thickness of the first resin film 3 is preferably about 100 μm. The surface of the first resin film 3 is preferably flat. The first resin film 3 has low elasticity enough to reduce stress due to a difference in thermal expansion coefficient from the semiconductor substrate, and has an elastic modulus of 5 GPa or less, particularly 2 GPa or less.
[0018]
Subsequently, the back surface 1b of the wafer 1 on which the first resin film 3 is formed is ground using, for example, a grinder to adjust the wafer 1 to a desired thickness (FIG. 1C). When the first resin film 3 is formed so as to cover the top of the bump electrode 2 and the surface of the first resin film 3 is flat, the first resin film 3 depends on the difference in thermal expansion coefficient from the semiconductor substrate. Since the elasticity is low enough to reduce the stress, the wafer 1 can be uniformly pressed from the side where the first resin film 3 is formed during grinding.
Thereafter, the second resin film 4 is formed on the back surface side of the ground semiconductor substrate (FIG. 1D). The second resin film 4 can be obtained by applying a liquid resin by a screen printing method, a spin coating method, a bar coating method, or the like, and then curing the resin. The type of resin can be polyimide, epoxy, or the like. The second resin film 4 is formed of a material having higher elasticity or higher strength than the first resin film 4. It is desirable that the second resin film 4 has an elastic modulus of 10 GPa or more, particularly 20 GPa or more.
FIG. 2 is a perspective view showing the entire wafer on which the first resin film 3 and the second resin film 4 are formed.
[0019]
Subsequently, the surface of the wafer on which the first resin layer 3 is formed, on which the protruding electrodes or wirings are provided, is ground using, for example, a grinder to adjust the first resin film 3 to a desired thickness to expose the protruding electrodes. .
[0020]
Subsequently, the wafer on which the first resin film 3 and the second resin film 4 are formed is attached to a tape called a dicing tape, and the semiconductor substrate is cut into individual pieces in a cutting process called dicing. The individual pieces are not scattered by the adhesive force (adhesive force). At this time, the tape may be attached to the electrode surface or the opposite side, but it is preferable to attach the tape to the second resin film 4 because damage during peeling can be prevented.
[0021]
As described above, according to this embodiment, the first resin film 3 formed on the surface 1a of the wafer 1 is formed with a low-elastic resin, so that the thermal expansion between the wafer 1 and the first resin film 3 is achieved. / No warping caused by the difference in shrinkage occurs. Therefore, when the grinding process (FIG. 1D) is performed, the wafer 1 is flat, so that the back surface 1b of the wafer 1 can be uniformly ground at each part of the wafer 1.
[0022]
In the grinding step, the entire wafer 1 is reinforced by the first resin film 3 formed on the surface 1a of the wafer 1. Therefore, the wafer 1 can be satisfactorily ground without causing damage to the wafer 1, so that the wafer 1 can be advantageously thinned.
Also, when the wafer 1 is handled in the cutting process or when the wafer 1 is cut by a dicing blade, the first resin film 3 and the second resin film 4 reinforce the wafer 1, so that the wafer 1 and the semiconductor There is no possibility that the chip 5 will be damaged. Therefore, the thickness of the wafer 1 can be reduced to a desired thickness, thereby contributing to a reduction in the thickness of the semiconductor chip 5.
[0023]
In the final form of the semiconductor chip 5 shown in FIG. 3, the semiconductor substrate is protected and reinforced on both sides by two kinds of resins. That is, the first resin film 3 protects the front surface 1a (active surface) of the wafer 1, and is also reinforced and protected on the back surface by the second resin film 4 having high elasticity or high hardness. Further, since the protruding electrodes 2 are exposed, further packaging of the semiconductor chip 5 is unnecessary. Therefore, it is possible to obtain a miniaturized and thinned semiconductor package with extremely high quality and high strength. Such a semiconductor package (semiconductor chip 5) can be mounted with the exposed protruding electrode 2 facing (face down) an electrode pad or the like formed on the wiring board.
[0024]
The above embodiments show the case where the wiring is formed on one surface of the semiconductor substrate 1 and then the protruding electrode 2 is formed. However, only one of the wiring and the protruding electrode may be formed for external connection. Good. Even when the protruding electrode 2 is not formed, a part of the wiring can be exposed from the first resin film 3 and connected to an electrode pad or the like of a wiring board.
In addition, various changes can be made within the scope of the matters described in the claims.
[Brief description of the drawings]
FIG. 1 is an illustrative sectional view showing a method for manufacturing a semiconductor device according to an embodiment of the present invention in the order of steps;
FIG. 2 is an illustrative perspective view showing a first resin film 3, a second resin film 4, and a semiconductor substrate.
FIG. 3 is a schematic perspective view of a semiconductor chip manufactured by the manufacturing method.
FIG. 4 is an illustrative view for explaining a problem of a warpage generated when a normal resin film is formed on one surface of a wafer;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Wafer 2 Protruding electrode 3 First resin film 4 Second resin film 5 Semiconductor chip

Claims (7)

A semiconductor substrate, at least one of a protruding electrode or a wiring formed on one surface of the semiconductor substrate, and a first resin film formed on one surface of the semiconductor substrate; A semiconductor device having low elasticity enough to reduce stress caused by a difference in thermal expansion coefficient of the semiconductor device. The semiconductor device includes a semiconductor substrate, at least one of a protruding electrode or a wiring formed on one surface of the semiconductor substrate, and a first resin film formed on the one surface, and an elastic modulus of the first resin film is 5 GPa or less. A semiconductor device, characterized in that: The semiconductor device according to claim 1, wherein a second resin film having higher elasticity or higher strength than the first resin film is formed on the other surface of the semiconductor substrate. 4. The semiconductor device according to claim 3, wherein said second resin film has an elastic modulus of 10 GPa or more. The semiconductor device according to claim 1, wherein the semiconductor substrate has a thickness of 400 μm or less. 7. The semiconductor device according to claim 3, wherein the semiconductor substrate has a thickness of 200 [mu] m or less and is formed at a center in a thickness direction of the semiconductor device in a cross-sectional structure. Forming at least one of a protruding electrode and a wiring on one surface of the semiconductor substrate;
Forming a first resin film having low elasticity on the surface of the semiconductor substrate on the active surface side provided with the protruding electrodes or the wirings or the like so as to reduce stress due to a difference in thermal expansion coefficient with the semiconductor substrate; ,
Grinding or grinding the other surface of the semiconductor substrate to reduce the thickness of the semiconductor substrate,
Forming a second resin film having higher elasticity or hardness than the first resin film on the ground surface after the first grinding step;
Cutting the wafer into individual pieces after the formation of the second resin film.

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