JPH0780379B2 - IC card - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a card-shaped semiconductor device (hereinafter referred to as an IC card) having a semiconductor integrated circuit (IC) built therein, and particularly to an IC chip built in the IC card. The present invention relates to a technology effectively applied to the crack prevention technology of.

[Prior art]

Cards such as cash cards and telephone cards that can be attached to and detached from the input / output terminal of the central processing unit are frequently used. This card generally has a read-only nonvolatile storage function provided with a magnetic surface layer for magnetic recording. This type of card has a small amount of information because it has a limit in the area of the magnetic surface layer and the densification of the magnetic material.

On the other hand, an IC card incorporating a semiconductor integrated circuit such as a microcomputer or an electrically erasable non-volatile memory function can highly integrate the semiconductor chip that constitutes the microcomputer or the non-volatile memory function, so You can do a lot. Further, since the IC card can independently perform information processing, it has a feature that the communication processing amount between the central processing unit and the input terminal device can be reduced.

As shown in FIG. 9, the IC card is formed by sandwiching an IC chip 2 in a core member 1, providing protective covers 3 on both sides of the core member 1, and thermocompression bonding with a high temperature press. is there.

[Problems to be solved by the invention]

However, as a result of examining the IC card technology, the inventor has found out the following problems.

That is, the IC chip used in the IC card is required to have a small thickness in accordance with the relatively small thickness. If the IC chip has the same thickness as that of a general semiconductor device and that of the IC chip to be finally obtained, the mechanical strength of the semiconductor wafer will be lowered. The semiconductor wafer is easily damaged.

Therefore, various circuit elements and the like are formed on a semiconductor wafer having a relatively large thickness by a known method regardless of the IC chip to be finally obtained. That is, the semiconductor wafer is made relatively thick until just before chip division. afterwards,
The semiconductor wafer is thinned by, for example, mechanically grinding the surface opposite to the surface on which the circuit elements and the like are formed (hereinafter referred to as the back surface), and then a plurality of semiconductor wafers are formed.
Divided into IC chips.

Since the IC card is carried in a pocket or the like and carried around, it may be bent, which may cause stress due to a bending moment.

As described above, since the IC chip has a relatively small thickness, it has low strength against mechanical stress. Therefore, the above-mentioned force easily causes a crack in the IC chip, and as a result, the IC card becomes unusable.

An object of the present invention is to provide a technique capable of reducing or preventing the occurrence of cracks in IC chips in IC cards.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[Means for solving problems]

The following is a brief description of the outline of the typical inventions among the inventions disclosed in the present application.

That is, an IC card in which a rectangular semiconductor chip is embedded in an insulating flexible core member, and an insulating flexible protective cover is provided on both surfaces of the core member. The back surface of the wafer has a grinding (grinding) direction substantially parallel to its long side.

[Action]

According to the above-mentioned means, since the grinding (grinding) direction of the back surface of the IC chip wafer is parallel to its long side, an IC card that is strong against bending stress can be obtained.

Example of Invention

An embodiment of the present invention will be specifically described below with reference to the drawings.

In all the drawings, those having the same function are designated by the same reference numeral, and repeated description thereof will be omitted.

〔Example〕

FIG. 1 is a plan view showing a schematic configuration of an IC card according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, and FIG. It is a figure for explaining the principle of.

FIG. 4 is a copy diagram showing a schematic configuration of an IC chip according to an embodiment of the present invention.

As shown in FIG. 1 and FIG. 2, the IC card of this embodiment uses, for example, a silicon substrate between core members having insulation flexibility such as vinyl chloride.
The IC chip 2 is embedded, and both surfaces of the core member 1 are covered with a protective cover 3 made of vinyl chloride or the like and having insulating flexibility, and thermocompression bonded by a high temperature press or the like.

Here, the bending strength of the IC card will be examined.

Here, the IC chip 2 is obtained as follows.

First, a MOSF is formed on the surface of the surface by a known integrated circuit forming technique.
A relatively thick semiconductor wafer on which circuit elements such as ET, wiring, electrodes, etc. are formed is prepared. Such a semiconductor wafer is then fixed to a sample table for grinding by a method such as vacuum adsorption. In this state, the rotary grinding disk or the sample table is moved, and as a result, the back surface of the semiconductor wafer is mechanically ground to reduce its thickness.

Although not particularly limited, the grinding device includes a plurality of grinding disks such as a grinding disk in which relatively large abrasive particles are used and a grinding disk in which relatively small abrasive particles are used. This enables high speed grinding and reduces the mechanical strain remaining on the back surface of the semiconductor wafer.

After that, the semiconductor wafer is transferred onto a sample table of a dicing device and divided into a plurality of IC chips by dicing.

Note that the thickness of the semiconductor wafer may be reduced by chemical grinding. That is, in this case, the front surface side of the semiconductor wafer is adhered to the sample table by a corrosion resistant adhesive such as wax, and then the back surface thereof is etched by the etching solution. In this case, substantially no mechanical strain is applied to the back surface side of the semiconductor wafer. However, in that case, it should be noted that the wiring layer on the front surface side is damaged by the etching solution unless the grinding speed is relatively slow and the adhesion is not good.

In the case of the rectangular IC chip 2, as shown in FIG. 3, comparing bending f (x) in the X direction and f (y) in the Y direction, when y> x, the x direction (short The side direction is stronger against bending. Therefore, in this embodiment, the strength of the IC card can be improved by arranging the short side direction of the IC chip 2 having high strength in the long side direction of the IC card to which a large bending force acts.

5 and 6 are plan views showing the structure of the wafer from which the IC chip according to this embodiment is to be obtained. In FIG. 5, the back surface of the wafer is ground in the orientation flat (or
ientation flat) is almost parallel to. In FIG. 6, the back surface of the wafer is ground in a direction perpendicular to the orientation flat.

Fig. 7 shows the relationship between the number of grinding steps, that is, the number of passing through the same grinding machine until a predetermined thickness is obtained, and the transverse rupture strength of the wafers cut into A and B shapes from the wafer shown in Fig. 5. FIG. 3 is an experimental characteristic diagram showing the above, and shows the transverse rupture strength characteristics of the semiconductor chips in the grinding directions A and B, respectively. According to FIG. 7, it is clear that the bending fracture strength is greater when the grinding direction is substantially parallel to the long side.

FIG. 8 shows the bending resistance of the abrasive grains and the IC chip in the wafer in the grinding direction shown in FIG. 6, that is, in the case of the wafer in FIG. It is an experimental characteristic figure which shows the relationship with breaking strength.

The semiconductor wafers of FIGS. 5 and 6 have the same crystal plane, orientation flat direction, and the like. As is clear from FIGS. 5 to 8, it can be understood that the relative relationship of the bending strength is not substantially related to the crystal orientation of the semiconductor wafer.

Thus, by using the IC chip 2 having high strength obtained by grinding the IC chip 2 so that the grinding (grinding) direction (grinding trace) of the IC chip 2 is parallel to the long side of the IC card 2. The strength of can be increased. In addition, this embodiment is arranged so that the long side of the IC chip 2 is perpendicular to the long side direction of the IC card.

Thus, by arranging the long side of the IC chip 2A vertically in the long side direction of the IC card where the bending force of the IC card is most applied, the bending force is strong against the bending of the IC chip 2A. Since the short side is added, it is possible to further reduce or prevent the occurrence of cracks in the IC chip 2.

The present invention has been specifically described above based on the embodiments.
It is needless to say that the present invention is not limited to the above-mentioned embodiment and can be variously modified without departing from the scope of the invention.

〔The invention's effect〕

The following is a brief description of an effect obtained by the representative one of the inventions disclosed in the present application.

That is, by making the grinding (grinding) direction (grinding trace) of the IC chip parallel to the long side of the IC chip,
Since the bending strength of the IC chip is increased against the bending force of the card in the Y direction, the generation of cracks in the IC chip can be reduced or prevented.

[Brief description of drawings]

FIG. 1 is a plan view showing a schematic configuration of an IC card according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, and FIG. It is a figure for explaining the principle of. FIG. 4 is a copy diagram showing a schematic structure of an IC chip according to an embodiment of the present invention, FIGS. 5 and 6 are plan views showing a structure of a wafer of the IC chip according to this embodiment, and FIG. Is A or B from the wafer shown in FIG. 5 or FIG.
Fig. 8 is an experimental characteristic diagram showing the relationship between the grinding step and the bending rupture strength in the shape cut out in Fig. 8, and Fig. 8 shows the bending rupture strength of the grinding abrasive grains and IC chips in the wafer shown in Fig. 5 or Fig. 6. FIG. 9 is an experimental characteristic diagram showing the relationship, and FIG. 9 is a diagram showing a schematic configuration of an example of an IC card. In the figure, 1 ... Core member, 2, 2A, 2B ... IC chip, 3 ...
It is a protective cover.

Claims (3)

[Claims] 1. An IC card in which a rectangular semiconductor chip whose back surface is ground is embedded between core members.
An IC card, wherein the back surface of the semiconductor chip is ground so that the grinding direction is substantially parallel to the long side direction of the semiconductor chip. 2. The IC card according to claim 1, wherein the semiconductor chip is arranged so that its long side is perpendicular to the long side of the IC card. . 3. The IC card according to claim 1, wherein both surfaces of the core member are covered with a protective cover made of vinyl chloride or the like.