JP2000048161A - Wafer for ic card and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thin wafer of high strength capable of realizing a thin IC card by mounting a circuit on the mirror surface finishing side of the wafer and forming a coating film of which the thickness of a cold-settable polysilicone varnish is within a specified range on the grinding surface of the rear side surface of the wafer. SOLUTION: An adhesive tape 2 is adhered to the circuit surface of the wafer 1 mounting a circuit and it is mounted onto the porous ceramic board 6 of a chuck mechanism supported by a hollow rotary shaft 7 while bringing the surface of this adhesive tape into contact with the surface of the board 6. After decompressing the hollow part 8 of the shaft 7 and chucking the wafer 1 to the board 6, the cold setting polysilicone varnish is supplied on the center of the grinding surface of the rear side surface of the wafer 1 as a continuous stream by a varnish supplying tube 4 while rotating the shaft 7 by 100 to 1000 rpm and rotating the wafer 1 in a horizontal direction. The coat of polysilicone of 0.1 to 10 μm thick is formed on the grinding surface of the rear side surface of the wafer 1 by spin-coating like this way.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reinforcing scratches on a ground surface of a wafer such as a bare wafer, a device wafer, an SOI wafer, a magnetic head wafer, and a magnetic disk wafer. In particular, the present invention relates to a thin IC card wafer in which a back surface ground surface of a wafer whose complex circuit is mirror-finished in units of microns by an exposure apparatus is reinforced with resin, and a method of manufacturing the same.

[0002]

2. Description of the Related Art IC cards are used for recording, erasing, and recording.
It can be rewritten, has a large storage capacity, and doubles as a record book.Therefore, it is being considered to replace the existing magnetic cards such as bank bank cards, railway operation record cards, department store cards, shopping cards, and telephone cards. (Patent Nos. 2510520 and 2510669).
Such an IC card is an IC on which an IC chip is mounted.
It is composed of a module and a card substrate on which a concave portion for mounting the IC module is formed.

[0003] For example, as shown in FIG.
0 comprises an IC module 21 and a card substrate 22.
In the figure, 23 is a substrate, 24 is an external terminal, 25 is a through hole, 25a is conductive plating, 26 is a pattern layer, 27 is a protective resist layer, 28 is an IC chip, 29 is a bonding material, 30 is a resin mold portion, 31 Is a card base material, 32 is an adhesive, 33 is a concave portion, 33a is a first concave portion, and 33b is a second concave portion.
The concave portion 34 is an adhesive storage groove. Although some IC cards have been put into practical use as microcomputer electronic cards, they are far from being widely used like magnetic cards.

[0004] The following two points are considered to be the major factors. The cost of the IC chip is high, and the manufacturing cost of the IC card is high. The thickness of the IC chip is at least 420 μm, the thickness of the IC card is about 500 μm, and the thickness is thicker than the 180-350 μm of the prepaid card and the bank magnetic card. It is bulky to carry. For the above, 64 Mb in 1996-1997
It's IC chip price is 10000-12000
In 1998, the price was reduced to around 600 yen per piece, and it is expected that the use of 16 Mbit and 64 Mbit IC chips will be resolved. For I
As a technology for encapsulating the C chip in the card, a resin film lamination technology and an IC chip resin encapsulation technology have been developed and succeeded in reducing the thickness of the resin, but succeeded in reducing the thickness of the IC chip. Not.

[0005] That is, when the IC card is put into a business card holder or a pocket, and the user puts it in clothes, sits down, or falls down while exercising, external stress acts on the IC card, and the encapsulated IC chip is damaged. It has been pointed out that malfunctions occur or stop working. Therefore, with the current technology,
The thickness of the IC chip must be at least 42 to withstand this stress.
0 μm. The brittle material that composes the IC chip is
The silicon wafer occupies a considerable part of the thickness of the IC chip. The process of obtaining a silicon wafer for IC cards is generally performed by slicing a single crystal ingot pulled up by a single crystal pulling apparatus to obtain a thin disk-shaped wafer, and in order to prevent chipping or cracking of the sliced wafer. A chamfering step for chamfering the outer peripheral edge of the wafer, a lapping step for flattening the surface of the chamfered wafer, a wet etching step for removing the remaining work-affected layer due to chamfering and lapping, and mirror polishing one side of the etched wafer A single-sided mirror surface process, a cleaning process to remove abrasives and foreign matter remaining on the polished wafer to improve the degree of cleaning, and a process of transferring a complicated circuit to the mirror-polished finished surface by an exposure device in units of microns. Adhesive tape on the surface to protect the circuit, adhesive on the chuck table The wafer is placed so that the side of the wafer is in contact with the table (table), the back surface of the wafer facing upward on the table is ground, and the thickness of the wafer is back-ground to a thickness of about 50 to 150 μm. A chemical etching process to remove scratches (see FIG. 3) having a depth of 0.5 to 1.5 μm generated on the surface of the wafer, setting the etched wafer in a dicing apparatus, separating an adhesive tape, A dicing step of dicing the wafer into chips (JP-A-6-224095,
See JP-A-10-50642. )

[0006]

The strength of the back-ground wafer was measured by using a three-point bending tester shown in FIG.
A hollow cylinder having a diameter of 7 mm is provided at the center of a square wafer sample piece having a width of 15 mm and a diameter of 250 mm to 300 mm.
The sample was placed on a jig consisting of a boring cylindrical body with a diameter of 5 mm, and the center point of the sample piece was roughly aligned with the center point of the jig. Contact
When the load applied to the weight when the sample piece was broken when it was lowered at a speed of 1 mm / min was defined as a three-point bending rupture strength,
Its strength is a three-point bending damage strength of at most 20 Newton (N) due to generation of scratches at the time of back surface grinding. The chemical etching step is performed to eliminate the scratches with nitric acid and hydrofluoric acid. However, in the etching method, even if the scratch disappears or the uneven surface of the wafer is reduced in thickness, almost the same unevenness is obtained. Is not copied, which does not lead to improvement in the three-point bending strength of the wafer. According to the present invention, even if a scratch (scratch) on the ground surface of the back surface of the wafer remains or not, the thickness 150 of the wafer is comparable to that of a prepaid card or a bank card.
It is an object of the present invention to provide a thin wafer having high strength capable of realizing an IC card of up to 300 μm.

[0007]

According to one aspect of the present invention, a circuit is mounted on a mirror-finished surface of a wafer, and a cold-curable polysilicon varnish having a thickness of 0.1 to 1 is formed on a ground surface of the wafer.
A thickness of 50 to 150 μm with a 0 μm film formed
m IC card wafers. According to the second aspect of the present invention, the adhesive tape is adhered to the surface of the circuit mounted on the mirror-finished surface to protect the circuit surface, and the wafer whose back surface has been ground and cleaned can be rotated on the adhesive tape side of the wafer. Chuck on a table supported by a suitable shaft, and then, while rotating the wafer on the table in the horizontal direction by rotating the shaft, drop a room temperature curable polysilicon varnish onto the ground back surface to perform spin coating. And drying the same to form a polysilicon film having a thickness of 0.1 to 10 μm on the ground back surface.

[0008]

According to the spin coating method, the polysilicon film compensates for a decrease in the strength of the scratch, and has a three-point bending strength of 40.
A silicon wafer having a thickness of 50 to 150 μm, which is as high as Newton or more, can be manufactured.
It has become possible to manufacture an IC card having a thickness of 0 to 300 μm, comparable to a prepaid card.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a plan view of an apparatus for forming a polysilicon film on a back-ground surface of a back-ground wafer, and FIG. 2 is a schematic diagram of a three-point bending test machine for the wafer. FIG. 3 is a view showing a state of a polished wafer obtained by synthesizing a surface state of the back-ground (back) ground wafer and a state of breakage near the front surface. Indicates the state of the cross section of the wafer. In the figure,
1 is a wafer, 1a is a grinding back surface, 2 is an adhesive tape, 3 is a varnish, 4 is a varnish supply tube, 5 is hot air, 6 is a suction plate, 7 is a hollow rotary shaft, and 8 is a hollow portion.

In the three-point bending tester 10 shown in FIG.
Denotes a jig, 12 denotes a test piece (wafer), and 13 denotes a weight. A cylinder having a diameter of 7 mm is hollowed out at the center of the jig.
The jig and weight are made of stainless steel, and the diameter of the cylindrical weight is 5 mm
At a speed of 1 mm / min. The adhesive tape 2 is adhered to the circuit surface of the wafer 1 on which the circuit is mounted, on the porous ceramic plate 6 of the chuck mechanism supported by the hollow rotary shaft 7, and this adhesive tape surface is brought into contact with the surface of the porous ceramic plate 6. And place it. The backside ground surface 1a of the wafer washed with isopropyl alcohol faces upward. After depressurizing the hollow portion 8 of the rotating shaft 7 and chucking the wafer 1 on the porous ceramic suction plate 6, the rotating shaft 7 is
While rotating the wafer 1 in the horizontal direction at 1,000 rpm, preferably 200 to 600 rpm, the room temperature curable polysilicon varnish is supplied as a continuous flow from the varnish supply pipe 4 to the center of the ground back surface of the wafer.

Next, in order to shorten the drying time of the varnish on the back ground surface on which the continuous film of the varnish is formed, 10
Blow hot air 5 at 0 to 160 ° C. Hot air blowing is not required if the drying time can be slow. After spin coating as described above, a thickness of 0.1-1
A film of polysilicon having a thickness of 0 μm, preferably 0.2 to 8 μm is formed. Room-temperature-curable polysilicone varnishes include polymethylsiloxane, polymethylphenylsiloxane, epoxy-modified polymethylsiloxane, alkoxy-modified polymethylsiloxane (methoxy groups, ethoxy groups, and butoxy groups as alkoxy groups), aminosilane-modified polymethylsiloxane, and the like. Is dissolved in an aromatic hydrocarbon solvent having a boiling point of 100 to 160 [deg.] C. such as benzene, toluene, or xylene, and a varnish having a concentration of 1 to 55% by weight is used. Among these polysilicones, a methylphenyl-based silicone is preferred from the viewpoint of solubility in an aromatic hydrocarbon solvent.

A room temperature-curable polysilicon varnish obtained by dissolving a methylphenyl-based silicone in a mixed solvent of toluene and xylene at a concentration of 50% by weight is, for example, a silicone varnish TSR144 (specific gravity: 1.02, viscosity: 110 mPa · s) manufactured by Toshiba Silicone Co., Ltd. ). In order to improve the impregnation property of the varnish into the scratches (wounds) of the wafer, it is preferable to use the varnish diluted with a solvent.

Conventionally, the sharp tip of the uneven surface of the back surface is chipped by chipping to generate a large number of particles and reduce the yield of IC chips. However, a uniform film of polysilicon is formed on the back surface. As a result, the yield of IC chips can be improved. After the spin coating, the adhesive tape is separated from the surface of the wafer in a dicing process, and the wafer is diced into IC chips. The printed and wired IC chip is housed in a concave portion of the card base material, and the periphery of a wiring portion including the IC chip and the bonding wires is sealed with a resin to form an IC card.

[0014]

Example of back grinding: An ultraviolet-curable resin layer on a polyethylene terephthalate biaxially-stretched film substrate was adhered on the circuit surface of an 8-inch silicon wafer (200 μm thick) on which circuits were mounted, and further adhered thereon A pressure-sensitive adhesive tape (120/38/8 μm thick) provided with an agent layer is adhered, and the substrate surface of the pressure-sensitive adhesive tape is placed so as to be in contact with a porous ceramic table of a chuck mechanism of an index table of a grinding device. Then, the hollow rotary shaft for supporting the base is 700 mmHg.
And the wafer was adsorbed. The final thickness (T _f ) of the target ground wafer was determined to be 136 μm, and the grinding amount was calculated to be 64 μm. If the grinding speed S is 0.8 μm / min, the theoretical grinding time is calculated to be 80 minutes.

The grindstone is lowered and pressed against the upper surface of the wafer on the suction chuck of the index table (pressure 500).
g / cm ² ), the rotation axis of the chuck mechanism was rotated rightward at 60 rpm and the rotation axis of the grindstone was rotated leftward at 100 rpm, and grinding was performed at a grinding speed of 0.8 μm / min for 80 minutes. The thickness of the roughly cut wafer was 135 μm.

Then, after raising the grindstone, the index table is rotated to the right by 120 degrees, and then the finished grindstone is lowered and pressed onto the rough-cut wafer (pressure 50).
g / cm ² ) Finish grinding was performed by rotating the rotating shaft of the chuck mechanism and the rotating shaft of the finishing grindstone. After the rotation of both rotating shafts was stopped and the grindstone was raised, the index table was rotated to the right by 120 degrees, and the thickness of the wafer was measured to be 134.0 μm. The roughness (Rmax) of the ground wafer measured by a stylus profilometer was 2 nm (the maximum depth of breakage was 1.4 μm, and the three-point bending rupture strength was 16 Newton). Next, the ground surface of the finish-ground wafer was washed with water.

Example of spin coating: A back surface ground surface is suctioned on a cleaned wafer using a chuck in which a porous ceramic plate of a chuck mechanism is covered with a breathable polyester cloth.
It was mounted on a porous ceramic suction plate 6 of the spin device shown in FIG. Then, after the rotation shaft 7 is attracted to 450 mmHg to fix the wafer, the rotation speed of the rotation shaft 7 is increased to 30 mm.
Rotate to the right at 0 rpm or 600 rpm, and then place a room temperature curing type polysilicon varnish TSR-144 (trade name) of Toshiba Silicone Co., Ltd. or its xylene / toluene from the varnish supply pipe on the center point of the back grinding surface of the wafer. : A varnish having a concentration shown in Table 1 diluted with a mixed solvent was supplied in a continuous flow (8 to 40 cc / min), and supplied for a time (min) shown in the same table to form a continuous film to form the ground back surface of the wafer. After that, hot air of 100 ° C. was blown from above the wafer and dried to obtain a cured film having a film thickness shown in the same table. Next, the wafer was taken out from the suction plate of the chuck mechanism, the wafer was diced into a 15 mm square, and the three-point bending strength of five wafer chip pieces from which the adhesive tape had been removed was measured. Table 1 shows the results.

[0018]

[Table 1]

[0019]

As can be understood from the three-point bending strength of the wafer shown in Table 1, although the film (experiments 1 to 3) was thinner than the scratch (scratch) depth of 1.4 μm (Experiment 1 to 3).
The fact that the three-point bending strength of the wafers Nos. 1 to 3 shows a value which is more than twice the value of 16 Newtons of the wafer having no film (blank) means that the polysilicon penetrates into the scratches and fills the wafers. It is assumed that the strength was improved.

[Brief description of the drawings]

FIG. 1 is a plan view of a spin coater.

FIG. 2 is a sectional view of a three-point bending tester.

FIG. 3 is a diagram showing a combination of a surface state and a cross-sectional state of a ground back surface of a wafer.

FIG. 4 is a cross-sectional view illustrating an example of an IC card.

Claims (5)

[Claims] 1. A circuit is mounted on a mirror-finished surface of a wafer, and a cold-curable polysilicon varnish having a thickness of 0.1 to 10 μm is formed on a ground surface of a back surface of the wafer. IC card wafer of 150 μm. 2. The cold-curable polysilicone varnish is a methylphenyl-based silicone having a boiling point of 100 to 160.
2. The IC card wafer according to claim 1, wherein the wafer is dissolved in an aromatic hydrocarbon solvent at a temperature of ° C. 3. An adhesive tape is adhered to the surface of the circuit mounted on the mirror-finished surface to protect the circuit surface, and the wafer whose back surface has been ground and cleaned can be rotated on the adhesive tape side of the wafer. Chuck on a table supported by a shaft, then spin-rotate the shaft to rotate the wafer on the table in the horizontal direction while spin-coating a cold-curable polysilicon varnish onto the ground back surface, A method for manufacturing a wafer, comprising drying and forming a polysilicon film having a thickness of 0.1 to 10 [mu] m on a ground back surface. 4. The cold-curable polysilicone varnish is prepared by converting a methylphenyl-based silicone to a boiling point of 100 to 160.
4. The method for producing a wafer according to claim 3, wherein the wafer is dissolved in an aromatic hydrocarbon solvent at a temperature of about 5 ° C. 5. The wafer manufacturing method according to claim 3, wherein drying of the varnish is performed by blowing hot air at 80 to 160 ° C. on the ground back surface of the wafer.