JPH04363048A - Bonding method of thin sheet - Google Patents

Abstract

PURPOSE:To bond a thin sheet such as a silicon wafer or the like to a holding member or the like for polishing use with good accuracy. CONSTITUTION:An adhesive layer 5 is formed on a bonding face for a wafer 4; then, the wafer 4 and a holding member 3 are brought face to face via the adhesive layer 5. At this time, the temperature of the holding member 3 is set near the melting point of the adhesive layer 5. In addition, they are pressurized, and the surface of the adhesive layer 5 is pressure-bonded firmly to a holding face 3a for the holding member 3. The holding member 3 is heated to a temperature which is higher than the melting point of the adhesive layer 5; the adhesive layer 5 is melted after that, the holding member 3 is cooled; the adhesive layer 5 is hardened again. At a stage where the adhesive layer 5 is pressurized, the temperature of the holding member 3 is kept near its melting point. As a result, the adhesive layer 5 does not flow, and the parallelism of the wafer 4 with the holding member 3 can be kept with good accuracy.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adhering thin plates, which is suitable for use in polishing a workpiece in the form of a thin plate, such as a silicon wafer, by bonding it to a holding member.

0002

[Prior Art] When polishing or lapping the surface of a thin plate-shaped workpiece (hereinafter referred to as a wafer) such as a silicon wafer, the wafer is bonded to a highly rigid holding member in order to maintain its rigidity. In this state, the other side of the workpiece may be pressed against a surface plate or the like to perform processing. FIG. 3 shows a conventionally known wafer polishing method as an example of such a polishing method. A holding member 3 having a holding surface 3a is provided, and an adhesive surface 4 of a wafer 4 is attached to the holding surface 3a of this holding member 3.
A is glued to hold the wafer 4.

[0003] Here, to briefly explain the procedure for bonding the wafer 4, first, an adhesive is applied to the bonding surface 4a of the wafer 4 by a known coating method such as a spin coating method, and a uniform thickness is coated on the wafer 4. An adhesive layer 5 is formed. As the adhesive, for example, natural wax or synthetic wax, which is a mixture of paraffin polymer resin and rosin, is used. Next, the holding member 3 is heated to raise the temperature of the holding surface 3a to a temperature sufficiently higher than the melting point of the adhesive, and then the wafer 4 and the holding member 3 are pressed together with the adhesive layer 5 interposed therebetween. As a result, the adhesive layer 5 is immediately melted and the holding surface 3a and the wafer 4 are bonded together.
Thereafter, by cooling the wafer 4 and the holding member 3, the adhesive is solidified and the wafer 4 and the holding member 3 are bonded together. After bonding the wafer 4 as described above, the holding member 3 is pressed downward by the hydraulic cylinder 6 to press the polished surface 4b of the wafer 4 against the surface plate surface 2a. While supplying polishing liquid containing abrasive grains to the surface plate surface 2a, the surface plate 2 is rotated around its axis by a motor M, and the holding member 3 is also rotated around its axis by a drive device (not shown). As a result, the polished surface 4b of the wafer 4 and the surface plate surface 2a are polished so that the polished surface 4b of the wafer 4 is parallel to the holding surface 3a.

0004

[Problems to be Solved by the Invention] However, in the conventional bonding method described above, the bonding layer 5 flows when bonding the holding member 3 and the wafer 4, so that the polishing surface 4b of the wafer 4 cannot be bonded. In some cases, it was not possible to process parallel to the surface 4a. That is, in the above-described bonding method, since the temperature of the holding member 3 is maintained above the melting point of the adhesive, the adhesive layer 5 is immediately removed when the holding member 3 and the adhesive layer 5 come into contact with each other.
melts and flows. Therefore, even though the adhesive layer 5 of uniform thickness is formed on the adhesive surface 4a of the wafer 4 before bonding, the adhesive material interposed between the holding member 3 and the wafer 4 flows and the adhesive layer The thickness of the wafer 5 becomes non-uniform, and the wafer 4 deforms accordingly, resulting in misalignment of the polished surface 4b of the wafer 4 and the holding surface 3a of the holding member 3.

Here, as a means of keeping the thickness of the adhesive layer 5 uniform, for example, a spherical jig is pressed against the back side of the wafer 4 and pressure is applied unevenly to create a predetermined pressure gradient. Although attempts have been made to maintain a uniform thickness of the adhesive layer 5 by changing the position of the pressure gradient depending on the flow condition of the adhesive, in reality, the thickness varies due to the influence of the viscosity coefficient. It is difficult to synchronize the flow rate of the adhesive and the rate of change of the pressure gradient, making it difficult to obtain sufficient effects. Further, even if a roller-shaped jig is used in place of the spherical jig, the same problem remains. This invention was made against this background, and is a method for holding a thin plate-shaped workpiece such as a wafer and a holding member while maintaining a uniform thickness of an adhesive layer interposed between them. The object of the present invention is to provide a method for bonding thin plates that can be bonded together.

[0006]

[Means for Solving the Problems] In order to solve the above problems, in the thin plate bonding method of the present invention, the workpiece is bonded to the workpiece while the temperature of the adhesive layer is maintained at a sufficiently high viscosity state near the melting point. The adhesive surface and the holding surface of the holding member are pressed together via the adhesive layer, and then the temperature of the adhesive layer is raised above the melting point to bond the workpiece and the holding member.

[0007]

[Operation] According to the above structure, when the workpiece and the holding member are pressed and bonded together, the adhesive layer does not flow, so the thickness of the adhesive layer is kept uniform, and the workpiece is deformed. It can be bonded to the holding member without causing damage.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the same components as those in the conventional example described above are given the same reference numerals and their explanations will be omitted.

In the bonding method of this embodiment, first, as shown in FIG. An adhesive is applied to the adhesive surface 4a to form an adhesive layer 5 having a uniform thickness. Here, natural wax or synthetic wax is used as the adhesive as in the conventional example described above, and a well-known coating method such as a spin coating method is used as the coating method. Further, the thickness of the adhesive layer 5 is preferably in the range of approximately 0.5 μm to 5 μm for a wafer 4 having a thickness of 600 μm, for example.

After forming the adhesive layer 5, the adhesive 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 adhesive layer 5, as shown in FIG. At this time, the temperature of the holding member 3 is heated in advance to 70° C., which is near the melting point of the adhesive. Next, the wafer 4 is evenly pressed from the surface to be polished 4b toward the holding surface 3a to bond the adhesive layer 5 and the holding surface 3 of the holding member 3.
a, and thereby the surface 5a of the adhesive layer 5
While eliminating air bubbles between the holding surface 3a and the holding surface 3a, the adhesive material on the surface of the adhesive layer 5 is forced to bite into the holding surface 3a. At this time,
As a method of applying pressure to the wafer 4 evenly, for example, a method of interposing a silicone rubber plate that is in close contact with the entire surface of the surface to be polished 4b between a jig that presses the surface to be polished 4b and the surface to be polished 4b, or a method using fluid pressure. For example, a method of pressurizing the wafer 4 using a method is used.

After pressurizing the wafer 4, the holding member 3 is heated from the side opposite to the holding surface 3a to raise the temperature of the adhesive layer 5 to a temperature sufficiently higher than the melting point, for example, 100°C. As a result, the adhesive layer 5 is heated to a temperature higher than its melting point and melted, and the adhesive material is sufficiently spread over the microscopically uneven holding surface 3a. Then, by cooling the holding member 3, the adhesive re-solidifies, and the holding surface 3a of the holding member 3 and the bonding surface 4a of the wafer 4 are firmly bonded via the adhesive layer 5. When the wafer 4 and the holding member 3 are bonded using the above procedure, the melting of the adhesive layer 5 progresses extremely slowly at the stage where the holding member 3 and the wafer 4 are brought into close contact with each other via the adhesive layer 5 and pressed. Furthermore, the molten portion is also held in its original position without flowing due to the viscosity of the adhesive. Therefore, when pressing the wafer 4 and the holding member 3, the thickness of the adhesive layer 5 is kept uniform, and as a result, deformation of the wafer 4 is prevented and the adhesive surface 4a and the holding surface 3a are accurately aligned. The wafer 4 and the holding member 3 can be bonded so as to be parallel to each other.

In this embodiment, the temperature of the holding surface 3a when the holding member 3 and the wafer 4 are bonded is determined by the adhesive layer 5.
Although the temperature is maintained at 70° C., which is close to the melting point of , the present invention is not limited to this. For example, the temperature may be set to a low temperature at which there is no fear that the adhesive layer 5 will melt at all. Conversely, even if the temperature of the holding member 3 is higher than the melting point, the above effects can be sufficiently achieved.

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

Further, in this embodiment, the wafer 4 was specifically explained 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-like workpieces.

[0015]

As explained above, according to the present invention, the temperature of the adhesive layer is maintained near the melting point when pressing the thin plate-shaped workpiece and the holding member, so that the adhesive layer can be uniformly formed. The workpiece can be adhered to the holding member in parallel while maintaining the thickness, and as a result, an excellent effect can be obtained in that the processing accuracy of the thin plate-like workpiece can be greatly improved.

[Brief explanation of the drawing]

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

FIG. 2 is a diagram showing a state in which a wafer and a holding member are pressed together.

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

[Explanation of symbols]

3 Holding member 3a Holding surface 4 Wafer (workpiece) 4a Adhesive surface 5 Adhesive layer

Claims (1)

[Claims] Claim 1: An adhesive is applied to at least one of the adhesive surface of a thin plate-shaped workpiece and the holding surface of a holding member that holds this workpiece to form an adhesive layer of uniform thickness; After that, in a thin plate bonding method in which the adhesive surface of the workpiece and the holding surface of the holding member are bonded together via the adhesive layer to bond the workpiece and the holding member, the temperature of the adhesive layer is set to around the melting point. The adhesive surface of the workpiece and the holding surface of the holding member are pressed together via the adhesive layer, and then the temperature of the adhesive layer is increased to bond the workpiece and the holding member together. A method for bonding thin plates, which is characterized by bonding.