JP3803214B2 - Manufacturing method of semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a thin semiconductor device.
[0002]
[Prior art]
In order to reduce the thickness of a semiconductor chip, a back grinding process for grinding the back side of a semiconductor wafer (hereinafter simply referred to as “wafer”) on which elements and wirings have been formed has been conventionally performed. This back grinding process has generally been performed by attaching a soft protective film to the surface of the wafer, pressing the wafer against the grindstone via the protective film, and rotating the wafer in that state.
[0003]
However, since the wafer is handled by the robot in the cutting process for cutting individual chips from the wafer, and the chip is handled by the robot in the process of mounting the cut chips on the lead frame, the thickness is excessively reduced. If pursued, it will lead to breakage of wafers and chips during handling, and yield will decrease. In particular, today, when wafers have become large in diameter, wafers that have been thinned by backside grinding can be easily damaged.
[0004]
In order to solve such a problem, for example, in Japanese Patent Application Laid-Open No. 11-150090, after a bump electrode group is formed on the surface of a wafer, a resin film is formed on the wafer surface, and the resin film is strengthened for protection. It has been proposed to be used as a plate. In the semiconductor device manufacturing method of this publication, the back surface of the wafer is ground after the resin film is formed, and the surface layer portion of the resin film is removed by etching to expose the protruding electrode group. Yes. After that, the resin film is removed along the scribe line, and further, a nitride film as a protective film is formed in a region avoiding the protruding electrode, and then the wafer is cut along the scribe line to obtain individual chips. Is cut out.
[0005]
In this method, the wafer after back grinding is reinforced with a resin film, and individual chips are also reinforced with a resin film. And it has the structure where the projection electrode used as an external electrode was embed | buried under the said resin film. As a result, the wafer and the chip can be handled well without causing such breakage, and the semiconductor device can be significantly reduced in thickness as compared with a configuration in which the external terminals are drawn out using wire bonding or the like.
[0006]
[Problems to be solved by the invention]
However, in the above-described prior art manufacturing method, due to the difference in thermal expansion / contraction rate between the wafer and the resin film between the formation of the resin film on the wafer surface and the back surface grinding, FIG. As shown exaggeratedly, there is a problem that the wafer is warped. When a wafer with such warpage is ground with a flat grindstone, the thickness of the wafer after grinding differs between the central region and the peripheral region of the wafer, so that a semiconductor chip with a uniform thickness can be obtained. In addition to disappearance, the semiconductor chip cut out from the central region of the wafer may not be thinned to the desired thickness.
[0007]
Accordingly, an object of the present invention is to solve the above technical problem and prevent the semiconductor substrate from warping, so that the back surface grinding process of the semiconductor substrate can be performed satisfactorily. It is an object of the present invention to provide a method for manufacturing a semiconductor device that can be manufactured satisfactorily.
[0008]
[Means for Solving the Problems and Effects of the Invention]
The invention according to claim 1 for achieving the above object includes a step of forming a surface resin layer on a surface of a semiconductor substrate, a step of forming a back surface resin layer on the back surface of the semiconductor substrate, the surface resin layer, and For the semiconductor substrate on which the back resin layer is formed, the back resin layer is removed by polishing or grinding, and further, by polishing or grinding the back side of the semiconductor substrate from which the back resin layer has been removed, A method for manufacturing a semiconductor device, comprising: a back grinding step of thinning a semiconductor substrate.
[0009]
Note that either the front surface resin layer or the back surface resin layer may be formed first or simultaneously. However, the front surface resin layer and the rear surface resin layer are formed at a short time interval such that warpage of the semiconductor substrate does not become a problem, or the semiconductor substrate is formed between the front surface resin layer and the rear surface resin layer. The temperature of the semiconductor substrate on which only one of the resin layers is formed is controlled so that no major warpage occurs on the semiconductor substrate until the other resin layer is formed. It is preferable to be placed in a different environment.
[0010]
According to the first aspect of the present invention, since the resin layer is formed on both the front surface and the back surface of the semiconductor substrate, thermal expansion / contraction is equally generated on the front and back surfaces of the semiconductor substrate. Therefore, there is no possibility that undesired warpage has occurred in the semiconductor substrate during the back surface grinding of the semiconductor substrate, so that this back surface grinding process can be performed satisfactorily, in either the central region or the peripheral region of the semiconductor substrate. However, the semiconductor substrate can be uniformly thinned. Thereby, a thin semiconductor device can be manufactured satisfactorily.
[0011]
The invention described in claim 2 further includes a cutting-out step of cutting out the semiconductor device by cutting the semiconductor substrate along a cutting line after the back surface grinding step. This is a method for manufacturing the semiconductor device.
According to the present invention, a plurality of semiconductor device pieces are cut out from a thinned semiconductor substrate. However, since the semiconductor substrate is uniformly thin everywhere, thin semiconductor device pieces having a uniform thickness can be obtained. Obtainable.
[0012]
The semiconductor substrate may further include an electrode forming step for forming a protruding electrode on the surface of the semiconductor substrate, and a surface grinding step for polishing or grinding the surface resin layer in order to expose the protruding electrode from the surface resin layer. . In this case, either the back grinding process or the surface grinding process may be performed first. Further, the cutting process is performed on the semiconductor substrate that has undergone the surface grinding process and the back surface grinding process.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic sectional view showing a method of manufacturing a semiconductor device according to an embodiment of the present invention in the order of steps. The semiconductor wafer W of FIG. 1 (hereinafter simply referred to as “wafer W”) has undergone various element forming steps, wiring forming steps, and the like, and the surface 1 which is the surface on the active surface region side is a protection made of a nitride film or the like It is covered with a film (passivation film). From this protective film, a pad for electrical connection with the outside is exposed.
[0014]
As shown in FIG. 1A, a plurality of protruding electrodes T made of, for example, gold (Au) are formed on this pad (electrode forming step). The protruding electrode T is preferably formed by, for example, electrolytic plating, and the height from the surface of the protective film is preferably about 50 μm, for example. The protruding electrode T is preferably a columnar shape such as a columnar shape or a quadrangular prism shape. As the material, solder or the like can be applied besides gold.
[0015]
After the formation of the protruding electrodes T, a protective resin layer 3 (surface resin layer) is formed on almost the entire surface 1 of the semiconductor wafer W as shown in FIG. The protective resin layer 3 is made of, for example, an epoxy resin, and is formed by, for example, a screen printing method. The protective resin layer 3 is preferably formed with a thickness that allows the protruding electrode T to be buried. Specifically, it is preferable that the thickness of the protective resin layer 3 is about 100 μm, thereby sufficiently exhibiting the function of reinforcing the wafer W that has undergone the back surface grinding process even after the surface grinding process described later. be able to.
[0016]
After the formation of the protective resin layer 3, the back surface resin layer 4 is formed on almost the entire back surface 2 of the wafer W as shown in FIG. The back surface resin layer 4 is preferably made of the same material as the protective resin layer 3, and is preferably formed to have substantially the same thickness as the protective resin layer 3. The back resin layer 4 can be formed by the same formation method as that for the protective resin layer 3.
It is preferable that the formation process of the protective resin layer 3 and the formation process of the back surface resin layer 4 are performed one after another so as not to cause a temperature change that causes a large warp in the wafer W, or simultaneously. If it is necessary to perform the formation process of the back surface resin layer 4 after a considerable time after the formation process of the protection resin layer 3, the wafer W after the formation of the protection resin layer 3 is formed on the protection resin layer 3. It is preferable that the temperature is controlled so that no warpage caused by the difference in thermal expansion / shrinkage between the wafer W and the wafer W occurs.
[0017]
After the back surface resin layer 4 is formed on the back surface 2 of the wafer W, as shown in FIG. 1 (d), the front surface 1 side of the semiconductor wafer W is ground using, for example, a grinder (surface grinding process). Precisely, the surface of the protective resin layer 3 is ground to expose the heads of all the protruding electrodes T. After the protruding electrodes T are exposed, both the protective resin layer 3 and the protruding electrodes T are ground. Progress simultaneously. This surface grinding treatment is performed, for example, until the layer thickness t3 of the protective resin layer 3 becomes about 40 μm, for example. After the surface grinding treatment, the surface of the protective resin layer 3 and the top surface of the protruding electrode T are flush with each other. In this surface grinding step, the back surface of the wafer W must be held by, for example, a vacuum chuck device or the like. At this time, the back surface 2 of the wafer W is protected by the back surface resin layer 4.
[0018]
Further, as shown in FIG. 1 (e), the back grinding process is similarly performed using, for example, a grinder. That is, the back surface resin layer 4 is ground and removed, and the back surface 2 of the semiconductor wafer W is ground continuously. As a result, the wafer W is thinned to a predetermined thickness tw (for example, tw is in the range of 100 μm). In this back grinding process, the front surface 1 of the semiconductor wafer W is protected by the protective resin layer 3, so that it is not necessary to use a protective film or the like.
[0019]
After that, as shown in FIG. 1 (f), along the scribe line (cutting line), the protective resin layer and the wafer W are cut by the dicing saw 5, and the semiconductor chip C shown in a perspective view in FIG. A plurality of pieces are cut out (cutout process).
In the back grinding process and the surface grinding process, the entire wafer W is reinforced by the protective resin layer 3 formed on the front surface 1 of the wafer W. Therefore, since the wafer W can be satisfactorily ground without causing damage to the wafer W, the wafer W can be advantageously thinned.
[0020]
Further, when the wafer W is handled before the cutting process or when the wafer W is cut by the dicing saw 5, the protective resin layer 3 reinforces the wafer W, so that the wafer W or the semiconductor chip C is damaged. There is no risk of occurrence. Therefore, the wafer W can be thinned to a desired thickness, which can contribute to the thinning of the semiconductor chip C.
In the final form of the semiconductor chip C shown in FIG. 2, the protective resin layer 3 protects the surface 1 (active surface) of the wafer W, and the top surface of the protruding electrode T from the protective resin layer 3. Is exposed, no further packaging of the semiconductor chip C is necessary. Therefore, an extremely thin semiconductor package can be obtained.
[0021]
As described above, according to this embodiment, the protective resin layer 3 is formed on the front surface 1 of the wafer W, and the back resin layer 4 is formed on the back surface 2. Equally occurs. Therefore, since the wafer W is not warped during the surface grinding step (FIG. 1 (d)) and the back surface grinding step (FIG. 1 (e)), the grinding of the protective resin layer 3 and the wafer W It is possible to uniformly grind the back surface 2 of each part of the wafer W. Thereby, the plurality of chips C cut out through the cutting step (FIG. 1 (f)) can have a uniform thickness.
[0022]
For example, in the state shown in FIG. 1D immediately after the surface grinding process is finished, the thicknesses of the resin layers 3 and 4 on the front and back surfaces of the wafer W are different. If the warpage of W becomes a problem, for example, the front and back surfaces of the wafer W may be held using a chuck. Since the protective resin layer 3 is sufficiently thinned after the back surface grinding process, there is no possibility that undesired warpage occurs in the wafer W in the state shown in FIG.
[0023]
Although one embodiment of the present invention has been described, the present invention can be implemented in other forms. For example, in the above-described embodiment, the surface grinding step (FIG. 1 (d)) is performed first, and then the back surface grinding step (FIG. 1 (e)) is performed, but the back surface grinding step is performed first. Then, a surface grinding step may be performed. However, in order to uniformly grind the protective resin layer 3 in each part of the wafer W, it is preferable to perform the surface grinding step first.
[0024]
In addition, various modifications can be made within the scope of the matters described in the claims.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a method of manufacturing a semiconductor device according to an embodiment of the present invention in the order of steps.
FIG. 2 is a schematic perspective view of a semiconductor chip manufactured by the manufacturing method.
FIG. 3 is an illustrative view for explaining a problem of warping that occurs when a resin layer is formed only on the surface of a wafer.
[Explanation of symbols]
T Projection electrode W Semiconductor wafer (semiconductor substrate)
C Semiconductor chip 3 Protective resin layer (surface resin layer)
4 Back surface resin layer 5 Dicing saw

Claims (2)

Forming a surface resin layer on the surface of the semiconductor substrate;
Forming a back surface resin layer on the back surface of the semiconductor substrate;
The backside resin layer is polished or ground and removed from the semiconductor substrate on which the topside resin layer and the backside resin layer are formed, and the backside of the semiconductor substrate from which the backside resin layer has been removed is polished or ground. And a back grinding process for thinning the semiconductor substrate. 2. The method of manufacturing a semiconductor device according to claim 1, further comprising a cutting-out step of cutting out the semiconductor device by cutting the semiconductor substrate along a cutting line after the back grinding step.

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