JP2000138193A - Method of preventing adhesion of deposit on mount plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent colloidal silica contained in an abrasive from depositing on the exposed part of a mount plate on which a wafer is not stuck to, when the wafer is stuck to the surface of the mount plate and the mount plate is set to a polisher to polish the wafer. SOLUTION: After a wafer 1 is stuck to a mount plate 3, a coat agent resistant to an abrasive is applied on the exposed surface of the mount plate 3 to form a coating layer 4. The coating layer 4 is removed after polishing processing. If trace amounts of colloidal silica contained in the abrasive deposits, a deposit accumulates on the surface of the coating layer. The deposit can be prevented from adhered on the surface of the mount plate 3 by removing the coating layer. Accordingly, the deposit layer is not formed as in the conventional methods, and the wafer is always uniformly stuck to the mount layer 3. Thus, the wafer with a high degree of flatness can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing deposits from adhering to a mount plate so as to obtain extremely high flatness when a wafer is polished smoothly in a semiconductor manufacturing process or the like. is there.

[0002]

2. Description of the Related Art Silicon wafers used in semiconductor manufacturing processes
Wafers such as c have been required to have higher and higher flatness with the ultra-high integration of semiconductor devices. Generally, in order to polish the surface of a wafer flat, the wafer is bonded to a mount plate made of ceramics or the like, the mount plate is set on a polishing machine, and the wafer is placed on a surface plate on which a polishing cloth is stuck. -Polishing by pressing the c surface. After the polishing process, the wafer is peeled off from the mounting plate, and the mounting plate is cleaned and reused.

Although most of the dust and the like are removed in the step of cleaning the mount plate, it is usual that colloidal silica or the like contained in the abrasive used in the polishing step directly adheres to the surface of the mount plate. It is difficult to remove easily in the washing process. In particular, the colloidal silica as described above is deposited in an order when the mounting surface is dried when the mounting plate is transported to the next step in a state in which the abrasive is attached, and the mounting plate is deposited several times. If it is used 100 times, the deposited layer formed around the bonded portion of the wafer may reach several μm. The deposits described above do not occur on the bonding surface of the mounting plate to which the wafer is bonded, but the surface of the mounting plate corresponding to the notch such as an orientation flat or a notch formed on the wafer is also formed. The deposit adheres as if it entered from the outer periphery of the wafer. As described above, if the wafer is bonded to the mounting plate in a state where a portion of the wafer is placed on the portion where the deposit is attached, the entire surface of the wafer is removed. The wafer could not be uniformly adhered to the mounting plate, and it was difficult to flatten the wafer with high precision.

[0004]

The problem to be solved by the present invention is as follows.
In the wafer polishing in which the wafer is adhered to the surface of the mount plate to polish the wafer as described above, deposits such as colloidal silica are deposited on the surface of the mount plate other than the portion where the wafer is attached. It is an object of the present invention to provide a method for preventing deposits from adhering to a mount plate so as not to adhere.

[0005]

According to the present invention, in a wafer polishing for polishing a wafer by bonding the wafer to the surface of a mounting plate, the wafer is bonded to the mounting plate. A coating agent resistant to an abrasive is applied to the exposed surface of the mount plate surrounding the bonded portion of the wafer to form a coating layer, and after the wafer is polished, the coating layer is removed. There is provided a method for preventing deposits from adhering to a mount plate, characterized in that the above-mentioned problem is solved.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a wafer (1) such as a silicon wafer has an adhesive layer (2) on which an adhesive such as wax diluted in an organic solvent is thinly applied. Is formed, and the wafer (1) with the adhesive is adhered to a mount plate (3) made of ceramics or the like. In the drawing, as an example, a wafer having a diameter of 300 mmφ (1)
And the mounting plate (3) to which this is attached has a diameter of 3
Although the case where the polishing process is performed on a single wafer and formed to have a diameter of 20 mm is shown, the present invention may be applied to a case where a plurality of wafers are attached to a mount plate and the polishing process is performed.

On a mounting plate (3) to which the wafer (1) is bonded, a coating agent having a resistance to an abrasive used in a polishing process is applied to an exposed surface surrounding the bonded portion of the wafer. By doing so, a coating layer (4) is formed. As the coating agent, for example, a substance substantially the same as the adhesive used for bonding the wafer (1) may be used as the coating agent, or an appropriate material particularly resistant to abrasives may be used. Can be used as a coating agent.

The application of the coating agent can be appropriately performed according to the properties of the coating agent. In the case of a molten wax similar to the adhesive, the nozzle (5) is used as shown in FIG. Co
The coating agent can be dropped and spin-coated by rotating the mount plate (3), or can be applied using a dispenser nozzle. At this time, the thickness of the coating layer (4) formed by the application is set so as not to exceed the polished surface (6) of the wafer (1) bonded to the mounting plate (3), and the resistance to the abrasive is impaired. Sufficient thickness, for example, about 1-30μ
m, preferably about 10 to 20 μm. Thereafter, the coating agent is solidified by heating or cooling according to the type of the coating agent to form a coating layer (4) (FIG. 3).

The mounting plate (3) (FIG. 3) on which the coating layer (4) is formed by bonding the wafer (1) is set on a polishing machine, and the polishing surface (6) of the wafer (1) is set. ) Is applied to a polishing cloth and rotated to polish. After the polishing process, the coating layer (4) remains on the mount plate (3) from which the wafer has been peeled off, as shown in FIG. The coating layer (4) may be removed at the same time when the mounting plate (3) is washed, or may be removed by another step.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A silicon wafer spin-coated with a molten wax mainly composed of petrolium wax as an adhesive.
The wafer (1) was placed on the mounting plate (3), and was pressed by a stamper (not shown) so that air was not taken in between the wafer and the mounting plate. After cooling the mounting plate (3) to solidify the molten wax and securely attach the wafer to the mounting plate, the nozzle (5) corresponding to the outer periphery of the bonding portion of the wafer (1) is used. The coating agent was applied by rotating a mount plate while dripping molten wax having a solid concentration of 50%, which was mainly composed of petroleum wax, as a coating agent. Then, the coating layer (4) having a thickness of about 15 μm was formed by cooling the molten wax. The mount plate was set in a polishing machine as usual, and the wafer was polished. After the wafer was peeled off, the mounting plate was washed with a detergent for washing the petroleum wax. As a result, the coating layer (4) was removed, and the surface of the mounting plate was made of colloidal silica or the like contained in the abrasive. No sediment was found. The mounting plate may be cooled by bonding the wafer, subsequently applying a coating agent around the wafer, and then cooling the same. A layer could be formed.

[0011]

The present invention is constructed as described above,
A coating agent resistant to an abrasive was applied to the exposed surface of the mount plate to which the wafer was bonded to form a coating layer, and after the wafer was polished, the coating layer was removed. Even if a very small amount of colloidal silica or the like in the polishing agent used in the polishing step is deposited, the deposit is deposited on the surface of the coating layer. The above-mentioned deposits can be prevented from adhering to the surface of the mounting plate, and therefore, a conventional deposition layer is not formed. Therefore, the wafer can always be uniformly adhered to the mounting plate, and a wafer having a high flatness can be obtained. Obtainable.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a wafer and a mounting plate before bonding.

FIG. 2 is an explanatory view showing a state in which a coating agent is applied to a mount plate to which a wafer is adhered.

FIG. 3 is an explanatory diagram of a mount plate in a state where a coating layer is formed.

FIG. 4 is an explanatory view of a mount plate with a wafer removed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wafer 2 Adhesive layer 3 Mounting plate 4 Coating layer

Claims (1)

[Claims] 1. A wafer polishing method for polishing a wafer by bonding the wafer to a surface of a mounting plate, wherein the wafer is bonded to a mounting plate, and then the wafer is surrounded by a bonding portion of the wafer. A mounting plate, characterized in that a coating agent having a resistance to an abrasive is applied to the exposed surface of the plate to form a coating layer, and the coating layer is removed after polishing the wafer. For preventing sediment from adhering to the surface.