JP2848971B2 - Bonding method of thin plate - 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 for bonding a thin plate suitable for use in a case where a thin plate-like workpiece such as a silicon wafer is bonded to a holding member for polishing.

[0002]

2. Description of the Related Art When polishing or lapping the surface of a thin plate-like workpiece (hereinafter abbreviated as a wafer) such as a silicon wafer, it is bonded to a highly rigid holding member in order to obtain the rigidity of the wafer. In this state, the other side of the workpiece may be pressed against a surface plate or the like to perform the processing. FIG. 3 shows a conventionally known method of polishing a wafer as an example of such a polishing method. In this polishing method, first, a polishing machine 1 is provided above a surface plate 2 of a polishing apparatus 1 in parallel with a surface surface 2a of the surface plate. The holding member 3 having the holding surface 3a is provided, and the bonding surface 4a of the wafer 4 is bonded to the holding surface 3a of the holding member 3 to hold the wafer 4.

Here, the procedure for bonding the wafer 4 will be briefly described. First, an adhesive is applied to the bonding surface 4a of the wafer 4 by a known coating method such as spin coating to form a uniform thickness on the wafer 4. An adhesive layer 5 is formed. The adhesive is, for example, a natural wax or a synthetic wax obtained by mixing a paraffin polymer resin and rosin. Next, the holding member 3 is heated to raise the temperature of the holding surface 3 a to a temperature sufficiently higher than the melting point of the adhesive, and thereafter, the wafer 4 and the holding member 3 are pressure-bonded via the adhesive layer 5. As a result, the bonding layer 5 is immediately melted and spread between the holding surface 3a and the bonding surface 4a of the wafer 4, and thereafter, the wafer 4
By cooling the holding member 3, the adhesive is solidified to bond the wafer 4 and the holding member 3. Then, after bonding the wafer 4 as described above, the holding member 3 is pressed downward by the hydraulic cylinder 6 and the polished surface 4b of the wafer 4 is pressed.
Is pressed against the surface 2a of the platen. The platen surface 2a is rotated around the axis by a motor M while supplying a polishing liquid containing abrasive grains, and the holding member 3 is also rotated around the axis by a driving device (not shown). Thereby, the polished surface 4b of the wafer 4 and the surface 2a of the platen are polished so that the polished surface 4b of the wafer 4 is parallel to the holding surface 3a.

[0004]

In the conventional bonding method described above, the bonding layer 5 flows when the holding member 3 and the wafer 4 are bonded to each other, so that the polished surface 4b of the wafer 4 is bonded. In some cases, processing could not be performed parallel to the surface 4a. That is, in the above-described bonding method, the temperature of the holding member 3 is maintained at a temperature equal to or higher than the melting point of the bonding material.
Melts and flows. Therefore, although the adhesive layer 5 having a uniform thickness is formed on the bonding surface 4a of the wafer 4 before bonding, the adhesive material interposed between the holding member 3 and the wafer 4 flows and the bonding layer 5, the thickness of the wafer 5 becomes non-uniform, and the wafer 4 is deformed in accordance with the unevenness, and the polished surface 4b of the wafer 4 and the holding surface 3a of the holding member 3 become out of parallel.

Here, as a means for keeping the thickness of the adhesive layer 5 uniform, for example, a spherical jig is pressed against the back side of the wafer 4 to unevenly pressurize it to create a predetermined pressure gradient. Although a method of keeping the thickness of the adhesive layer 5 uniform by changing the position of the pressure gradient in accordance with the flow state of the adhesive has been attempted, in practice, the thickness fluctuates under the influence of the viscosity coefficient. It is difficult to synchronize the flow speed of the adhesive and the change speed of the pressure gradient, and it is difficult to obtain a sufficient effect. The same problem remains even if a roller-shaped jig is used instead of the spherical jig. The present invention has been made under such a background, and a thin plate-like workpiece such as a wafer and a holding member are held while maintaining the thickness of an adhesive layer interposed therebetween. An object of the present invention is to provide a method of bonding a thin plate that can be bonded.

[0006]

In order to solve the above-mentioned problems, in the method of bonding a thin plate according to the present invention, the temperature of the above-mentioned adhesive layer is maintained at a sufficiently high viscosity near the melting point. The bonding surface and the holding surface of the holding member are press-bonded via the bonding layer, and then the temperature of the bonding layer is raised above the melting point to bond the workpiece and the holding member.

[0007]

According to the above construction, the flow of the adhesive layer does not occur when the workpiece and the holding member are pressed and pressed together, so that the thickness of the adhesive layer is kept uniform and the workpiece is deformed. It is possible to adhere to the holding member without causing the holding member.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. The same components as those in the above-described conventional example are denoted by the same reference numerals, and description thereof will be omitted.

In the bonding method of this embodiment, first, as shown in FIG. 1, one side of a wafer 4 formed in a substantially disk shape is polished on one side with a bonding surface 4a, and the other surface is polished with a surface plate 2a of a polishing apparatus 1. The surface to be polished 4b is formed, and an adhesive is applied to the adhesive surface 4a to form an adhesive layer 5 having a uniform thickness. Here, as the adhesive, a natural wax or a synthetic wax is used as in the above-described conventional example, and a well-known coating method such as a spin coating method is used as a coating method. The thickness of the adhesive layer 5 is preferably in the range of about 0.5 μm to 5 μm for a wafer 4 having a thickness of, for example, 600 μm.

After the formation of the bonding layer 5, the bonding surface 4a of the wafer 4 and the holding surface 3a of the holding member 3 are brought into close contact with each other via the bonding layer 5, as shown in FIG. At this time, the temperature of the holding member 3 is previously heated to 70 ° C. near the melting point of the adhesive. Then, the wafer 4 is evenly pressed from the surface to be polished 4b toward the holding surface 3a, and the adhesive layer 5 and the holding surface 3 of the holding member 3 are pressed.
a is firmly press-bonded, and thereby the surface 5a of the adhesive layer 5 is pressed.
In addition to eliminating air bubbles between the first and second holding surfaces 3a, the adhesive on the surface of the adhesive layer 5 is cut into the holding surface 3a. At this time,
Examples of the method of uniformly pressing the wafer 4 include a method of interposing a silicon rubber plate which is in close contact with the surface to be polished 4b between a jig for pressing the surface to be polished 4b and the surface to be polished 4b. Is used to pressurize the wafer 4.

After the wafer 4 is pressurized, the holding member 3 is subsequently heated from the side opposite to the holding surface 3a to raise the adhesive layer 5 to a temperature sufficiently higher than the melting point, for example, 100.degree. As a result, the adhesive layer 5 is heated to a temperature equal to or higher than the melting point and melts, and the adhesive spreads sufficiently on the holding surface 3a which is microscopically uneven. Then, by cooling the holding member 3, the adhesive is re-solidified and the holding surface 3 a of the holding member 3 and the bonding surface 4 a of the wafer 4 are firmly bonded via the bonding layer 5. When the wafer 4 and the holding member 3 are bonded in the above procedure, the melting of the bonding layer 5 proceeds very slowly at the stage where the holding member 3 and the wafer 4 are brought into close contact with each other via the bonding layer 5 and pressed. Moreover, the melted portion is also restrained at the original position without flowing due to the viscosity of the adhesive. Therefore, when the wafer 4 and the holding member 3 are pressed, the thickness of the adhesive layer 5 is kept uniform. As a result, the deformation of the wafer 4 is prevented, and the bonding surface 4a and the holding surface 3a are accurately formed. The wafer 4 and the holding member 3 can be bonded so as to be parallel.

In this embodiment, the temperature of the holding surface 3a when the holding member 3 and the wafer 4 are pressure-bonded is controlled by the adhesive layer 5 in particular.
The temperature is maintained at 70 ° C., which is close to the melting point, but the present invention is not limited to this. For example, the temperature may be set to a low temperature at which there is no possibility that the adhesive layer 5 melts. Conversely, even if the temperature of the holding member 3 is higher than the melting point, the above effect can be sufficiently exerted.

In this embodiment, the bonding layer 5 is formed only on the bonding surface 4a of the wafer 4, but the present invention is not limited to this, and the bonding layer 5 is formed on the holding surface 3a side or with the bonding surface 4a. An adhesive layer may be formed on both surfaces 3a.

Further, in the present embodiment, the wafer 4 has been particularly described as an example of the workpiece, but the present invention is not limited to this, and can be applied to bonding of various other thin plate-shaped workpieces.

[0015]

As described above, according to the present invention, the temperature of the adhesive layer is kept close to the melting point when the thin plate-shaped workpiece and the holding member are pressed, so that the adhesive layer can be made uniform. The workpiece can be adhered to the holding member in parallel while maintaining the thickness, and as a result, an excellent effect of greatly improving the processing accuracy of the thin plate-shaped workpiece can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state in which an adhesive layer is formed on a wafer surface.

FIG. 2 is a view showing a state in which a wafer and a holding member are crimped.

FIG. 3 is a schematic view of a polishing apparatus for explaining a wafer polishing method.

[Explanation of symbols]

 Reference Signs List 3 holding member 3a holding surface 4 wafer (workpiece) 4a bonding surface 5 bonding layer

Claims (1)

(57) [Claims] An adhesive is applied to at least one of an adhesive surface of a thin plate-shaped workpiece and a holding surface of a holding member for holding the workpiece to form an adhesive layer having a uniform thickness. Thereafter, in a method of bonding a thin plate in which the bonding surface of the workpiece and the holding surface of the holding member are pressed through the bonding layer to bond the workpiece and the holding member, the temperature of the bonding layer is set to a temperature near the melting point. In the state of holding, the bonding surface of the workpiece and the holding surface of the holding member are press-bonded via the bonding layer, and then the temperature of the bonding layer is increased to separate the processing object and the holding member. A method for bonding thin plates, comprising bonding.