JP2531360B2 - Method for manufacturing semiconductor device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device including a step of grinding the back surface of a semiconductor substrate to process the semiconductor substrate to a constant thickness.

[0002]

2. Description of the Related Art In a semiconductor device, a semiconductor element and wiring are usually formed on one main surface of a semiconductor wafer having a predetermined thickness, and then the back surface on which no element is formed is ground to a desired thickness. After adjustment, it is cut into chips and incorporated into a case to complete a part, which is mounted in the apparatus in this state. Here, the desired thickness is 3 due to assembly restrictions.
On the other hand, in the process of processing a semiconductor wafer, a thickness of 500 to 800 μm is required due to the necessity of mechanical strength and the prevention of crystal defects during heat treatment. Therefore, grinding cannot be omitted by using a wafer having a desired thickness from the beginning.

In addition to the above-mentioned general use method, in recent years, in order to increase the system speed and density, a method of directly mounting a semiconductor chip on a device substrate without using a case has been used. ing. That is, a bump electrode is provided on the chip surface, and TAB (Tape Autom
This is a method of directly connecting to the device substrate via a lead of an ated bonding method or the like. Usually, a large number of the above chips are mounted on a device substrate, and a heat sink or the like for radiating the chips is commonly contacted with the back surfaces of the plurality of chips. In the case where the above-mentioned mounting method is adopted, in an element such as a memory element that may malfunction due to α-rays, a resin film for α-ray shielding is attached to the chip.

Next, a conventional method of manufacturing a semiconductor device compatible with the above mounting method will be described with reference to FIG. First, as shown in FIG. 5A, a wafer 1 on which elements and wirings are formed and bumps 2 are formed on the surface is prepared, and a resin film 11 for surface protection (thickness 500 μm is formed on the wafer 1.
A) is attached [Fig. 5 (b)]. After that, the back surface is ground with a grinding device set to a predetermined gap x [Fig.
(C)]. Then, the resin film 11 is removed, and the thickness y
To obtain the wafer [FIG. 5 (d)].

Next, this is cut into chips 3 [FIG.
(E)], The α-ray shielding silicon resin film 4 is adhered to the surface to obtain a chip having a thickness z (FIG. 5 (f)). Further, after the inner lead bonding of the TAB lead 7 is performed, the chip is electrically inspected, and then the outer lead bonding is performed to connect the chip and the wiring substrate. Finally, the wiring board 8 on which the chip is mounted is mounted in a system having a heat sink 9 to complete the device [FIG. 5 (g)].

[0006]

When the above-mentioned mounting method is adopted, since a plurality of chips are arranged on the same wiring board and the back surfaces of the chips are collectively cooled by the same heat sink or the like, the individual chip thicknesses are reduced. If there is variation, the chips will not be fully contacted with the heat sink. In order to avoid such a problem, it is necessary to suppress the variation of the chip thickness to about ± 10 μm or less, but in the conventional manufacturing method, some of them may be ± 40 to 70 μm, so that some chips are insufficiently cooled. However, there is a problem that the electrical performance is deteriorated due to the rise of the chip temperature and the chip is broken in an extreme case.

The reason why such a large variation occurs in the conventional manufacturing method is that the error in the clearance (x) of the grinding machine is about ± 1.
This is because the following variations are added to the chip thickness in addition to 0 μm. That is, the variation of the surface protection resin film thickness is about ± 10 μm, and the variation of the α-ray shielding silicon resin film thickness is about ± 20 to ± 50 μm. These are due to both manufacturing variation of the film itself and thickness variation due to the pressing force at the time of attachment. As a result, the total chip thickness z has a large error of ± 40 to 70 μm.

[0008]

According to the present invention, in order to eliminate the above-mentioned cause of variation, a step of dividing a wafer on which elements have been formed into individual chips, and an element surface on each chip is semipermanently formed. The method includes a step of forming a protective film for protection while avoiding the electrode portion, and a step of grinding the back surface of the semiconductor substrate to process the substrate thickness to a desired value. There is provided a method for manufacturing a semiconductor device, which is performed while being covered with a protective film.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a process cross-sectional view showing the manufacturing process flow of the first embodiment of the present invention. First, a wafer 1 is prepared in which elements, wirings and bumps 2 are formed on one main surface of a semiconductor substrate [FIG. 1 (a)]. Next, the wafer 1 is attached to the semiconductor chip 3
It is cut into pieces [Fig. 1 (b)]. Further, a silicon resin film 4 for α-ray shielding and surface protection is adhered to the chip surface [FIG. 1 (c)]. Next, the surface of the chip 3 is sucked and held by the vacuum chuck 5, and the clearance between the tip of the chip 3 and the lower surface of the vacuum chuck 5 is adjusted to z.
Is moved to perform grinding [Fig. 1 (d)], and the total thickness z
To obtain a chip [FIG. 1 (e)]. After that, the TAB lead 7 is inner lead bonded to the semiconductor chip 3, an electrical test is performed, and then the TAB lead 7 is mounted on the wiring board 8 and the back surface is brought into contact with the heat sink 9 to complete mounting in the device. [FIG. 1 (f)]. According to the present embodiment, the variation of the total chip thickness z depends only on the gap of the grinding device, and it is possible to obtain a semiconductor chip processed into a highly accurate thickness of about ± 10 μm.

FIG. 2 is a process sectional view showing a manufacturing process flow of the second embodiment of the present invention. In this embodiment, the steps of FIGS. 2A to 2C are the same as the steps of FIGS. 1A to 1C of the first embodiment, but FIG.
In the grinding step shown in (d), unlike the case of the first embodiment, the grinding wheel 10 is lifted from below the chip to perform grinding, and the lifting is stopped when the gap reaches the desired thickness z. Then, a chip 3 having a total thickness z shown in FIG. After that, as in the case of the first embodiment, the wiring board 8 and the heat sink 9 are formed by the TAB method.
It is mounted in a certain device [FIG. 2 (f)]. In this embodiment, since the tip is gradually cut, there is an advantage that chipping of the tip end portion, which is likely to occur in the previous embodiment, is unlikely to occur.

FIG. 3 is a process sectional view showing a manufacturing process flow of the third embodiment of the present invention. First, a wafer 1 in which elements, wirings and bumps 2 are formed on one main surface of a semiconductor substrate
[Fig. 3 (a)], and a silicon resin film 4 for α-ray shielding and surface protection is provided on each chip in the wafer state.
Are adhered [Fig. 3 (b)]. Next, the back surface of the wafer 1 is ground by a grinding machine having a gap z to obtain a total thickness z.
To obtain the wafer [FIG. 3 (c)]. Then, the wafer 1 is diced to obtain semiconductor chips 3 having a total thickness z (FIG. 3D). Further, as in the case of the first embodiment, it is mounted in a device having the wiring board 8 and the heat sink 9 [FIG. 3 (e)]. In this embodiment, since the back surface is ground in the wafer state, workability is improved as compared with the previous embodiment.

FIG. 4 is a process sectional view showing a manufacturing process flow of the fourth embodiment of the present invention. First, a wafer 1 in which elements, wirings and bumps 2 are formed on one main surface of a semiconductor substrate
Is prepared [FIG. 4 (a)], and the photosensitive resin film 4a is adhered on the wafer [FIG. 4 (b)]. Then, exposure and development are performed to form a photosensitive resin film 4a for α-ray shielding and surface protection on each chip [FIG. 4 (c)]. Next, the back surface of the wafer 1 is ground by a grinding machine having a gap z to obtain a wafer having a total thickness z [FIG.
(D)]. Then, the wafer 1 is diced to obtain semiconductor chips 3 having a total thickness z (FIG. 4E). further,
Similar to the case of the first embodiment, it is mounted in a device having the wiring board 8 and the heat sink 9 [FIG. 4 (f)]. In this embodiment, since the resin film for α-ray shielding and surface protection is formed by the photolithography method, there is an advantage that the resin film can be formed with high accuracy.

While the preferred embodiment has been described,
The present invention is not limited to these examples, and various modifications can be made within the scope of the present invention described in the claims. The mounting method is also T
The method is not limited to the AB method.

[0014]

As described above, in the method of manufacturing a semiconductor device according to the present invention, the resin film permanently adhered to the semiconductor chip and used for the purpose of α-ray shielding is also used as the surface protective film during the back grinding. Therefore, according to the present invention, as in the case of using the resin film dedicated to the surface protection at the time of grinding the back surface, the influence of the variation in the thickness of the surface protection film and the variation in the alpha-ray shielding resin film is eliminated. It is possible to obtain a chip with a high precision thickness without receiving it.
Therefore, according to the present invention, when a plurality of chips are brought into contact with a common heat sink, all the chips can be brought into contact with it with an appropriate contact pressure, and cooling at the time of mounting can be performed uniformly and sufficiently. Like Further, according to the present invention, the process of forming the resin film dedicated to surface protection can be omitted by using the α-ray shielding film also as the surface protection film, and the process is simplified.

[Brief description of drawings]

FIG. 1 is a process sectional view for explaining a first embodiment of the present invention.

FIG. 2 is a process sectional view for explaining a second embodiment of the present invention.

FIG. 3 is a process sectional view for explaining a third embodiment of the present invention.

FIG. 4 is a process sectional view for explaining a fourth embodiment of the present invention.

FIG. 5 is a process sectional view for explaining a conventional example.

[Explanation of symbols]

 1 Wafer 2 Bump 3 Semiconductor Chip 4 Silicon Resin Film 4a Photosensitive Resin Film 5 Vacuum Chuck 6 Diamond Wheel for Grinding 7 TAB Lead 8 Wiring Board 9 Heat Sink 10 Grinding Wheel 11 Surface Protective Resin Film

Claims (3)

(57) [Claims] 1. A step of dividing a wafer on which elements have been formed into individual chips, a step of forming a protective film for semi-permanently protecting the element surface on each chip while avoiding the electrode portion, and a back surface of the semiconductor substrate. In a method of manufacturing a semiconductor device, which comprises a step of grinding to process a substrate thickness to a desired value, backside grinding is performed in a state in which an element surface of a chip is covered with the protective film. Manufacturing method. 2. A step of dividing a wafer on which elements have been formed into individual chips, a step of attaching a protective film that semipermanently protects the element surface on each of the divided chips while avoiding electrode parts, and A method of manufacturing a semiconductor device, comprising the step of grinding the back surface of the chip with the element surface covered with the protective film to process the thickness of the chip to a desired value. 3. A step of forming a protective film for semipermanently protecting an element surface on each chip of a wafer on which elements have been formed, and a back surface of the wafer with the element surface of the chip covered with the protective film. Grinding and processing the thickness of the wafer to a desired value, dividing the wafer into individual chips,
A method for manufacturing a semiconductor device, comprising: