WAFER SIDE EDGE CLEANING APPARATUS

Abstract

A wafer side edge cleaning apparatus includes: a cleaning device including a fixing element and a wafer brush disposed beneath the fixing element. The wafer brush is in the shape of a frustum. The frustum has a tapered surface contacting with a side edge of a wafer. The top surface of the frustum is larger than the bottom surface of the frustum. When cleaning the side edge of the wafer, the wafer and the wafer brush are rotated in different directions and a cleaning solution flows out from the fixing element rinses and washes the side edge brush.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wafer cleaning apparatus, and more particularly, to an apparatus for cleaning the side edge of a wafer.

2. Description of the Prior Art

Semiconductor chip fabrication is a complicated process that involves many manufacturing steps. These steps may include layering, patterning, etching, doping, chemical mechanical polishing (CMP), etc. It is well known that, during the various steps in these operations, the surfaces, or side edges of the semiconductor wafers will become contaminated with residues. In particular, the side edge of the wafer may suffer from peelings.

The removal of these contaminants and peelings is a priority to semiconductor chip fabricators because contaminants and peelings will pollute the chamber and influence the quality of the integrated circuit on the wafer.

Conventionally, one system used to remove wafer contaminants on the surface is a wafer cleaning device. In the wafer cleaning device, a semiconductor wafer is held to a stage. The stage has a vacuum suction member to suck the back side of the wafer, so the wafer can be disposed on the stage stably. Then, the wafer is rotated and the surface of the wafer is scrubbed by a brush.

Although a conventional wafer cleaning device can effectively clean the front side of the wafer, such systems fail to provide a cleaning method at the side edge/bevel area to remove contamination and peelings.

SUMMARY OF THE INVENTION

It is therefore one objective of the present invention to provide an apparatus that cleans the side edge of wafers, including the bevel area (when present).

According to a preferred embodiment of the present invention, a wafer side edge cleaning apparatus includes: a wafer stage for holding and rotating a wafer, wherein the wafer has a side edge, and a cleaning element includes: a fixing element, and a wafer brush fixed onto the fixing element, the wafer brush having a tapered surface contacting the side edge of the wafer. The tapered surface defines a bottom surface and a top surface of the wafer brush; the bottom surface is away from the fixing element, the top surface contacts the fixing element, and the bottom surface is smaller than the top surface. A cleaning solution rinses the wafer brush when the side edge of the wafer is subject to cleaning by the wafer brush.

According to a preferred embodiment of the present invention, the tapered surface and the top surface define an included angle which is between 45 and 80 degrees.

According to another preferred embodiment of the present invention, the wafer side edge cleaning apparatus further includes a bolt disposed under the fixing element and penetrating the wafer brush, and a nut disposed under the wafer brush and screwed on the bolt to fix the wafer brush on the fixing element.

According to another preferred embodiment of the present invention, the side edge of the wafer comprises a bevel.

From one aspect, the features of the present invention are that the side edge of the wafer is cleaned by the tapered surface of the wafer brush. Because the tapered surface contacts the side edge of the wafer, the containments or peelings on the side edge can be adsorbed on the wafer brush so these containments or peelings can be removed.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a wafer side edge cleaning apparatus schematically.

FIG. 2 depicts a three-dimensional graph of a cleaning element schematically according to a first preferred embodiment of the present invention.

FIG. 3 depicts a sectional view of the cleaning element shown in FIG. 2 along the line AA′.

FIG. 4 depicts a sectional view of the cleaning element shown in FIG. 2 along the line BB′.

FIG. 5 depicts a three-dimensional graph of a cleaning element schematically according to a second preferred embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 depicts a wafer side edge cleaning apparatus schematically. As shown in FIG. 1, the wafer side edge cleaning apparatus includes a wafer stage 12 for holding and rotating a wafer 14. The wafer 14 includes a side edge 16, and the side edge 16 includes a bevel 17. A vacuum suction member (not shown) sucks the wafer 14 by a suction force F₁ to fix the wafer on the wafer stage 12. The side edge of the wafer is cleaned after the steps of layering, patterning, etching, doping, or chemical mechanical polishing, and before the succeeding fabrication step. Furthermore, when the side edge 16 is subject to cleaning, the bevel 17 of the side edge 16 is cleaned as well.

When the side edge 16 is subject to cleaning, the wafer 14 is rotated to a first direction: for example, the wafer 14 is rotated clockwise. At this point, a controlling arm 18 moves a cleaning element 20 downward, and a wafer brush 22 of the cleaning element 20 is therefore disposed at a side of the side edge 16 in a horizontal direction. Then, the controlling arm 18 moves the cleaning device 20 toward the side edge 16 of the wafer in a horizontal direction, and a tapered surface 24 of the wafer brush 22 contacts the side edge 16 of the wafer 14. At this point, the wafer brush 22 has a lateral force F₂ and a downward force F₃ with respect to the wafer 14. According to a preferred embodiment of the present invention, the suction force F₁ should be greater than the downward force F₃ provided by the wafer brush 22, otherwise one point on the rim of the wafer 14 will be raised upwards, making the wafer 14 act like a seesaw. The lateral force F2 should be equal to a coefficient of friction μ multiplied by the suction force F₁; that is, F₂=F₁×μ. The coefficient of friction μ represents the coefficient of friction of the wafer 14 on the stage 12. In this way, the wafer 14 can be fixed on the stage 12 stably without moving in a lateral direction. Moreover, during the process of the side edge 16 of the wafer being cleaned, the wafer brush 22 is rotated to a second direction: for example, the wafer brush 22 can be rotated counterclockwise.

FIG. 2 depicts a three-dimensional graph of a cleaning element schematically according to a first preferred embodiment of the present invention. FIG. 3 depicts a sectional view of the cleaning element in FIG. 2 along the line AA'. FIG. 4 depicts a sectional view of the cleaning element in FIG. 2 along the line BB'.

As shown in FIG. 2, the cleaning element 20 further includes a fixing element 26 having a bolt 30 attached under the fixing element 26. The wafer brush 22 is fixed under the fixing element 26 with the bolt 30 penetrating through the wafer brush 22. A nut 32 is disposed beneath the wafer brush 22 and screws on the bolt 30 to fix the wafer brush 22 securely. The wafer brush 22 has to be replaced by a new one periodically so as to maintain the best cleaning result. The nut 32 can be easily taken apart from the bolt 30, therefore, the wafer brush 22 can be changed simply. Maintenance work of the wafer brush 22 becomes simple. Furthermore, because the nut 32 can change its position by moving up or down, the combination of the bolt 30 and nut 32 for fixing the wafer brush 22 with different sizes and shapes has also been taken into consideration. Therefore, based on different requirements, the wafer brush 22 with different sizes or shapes can be fixed on the fixing element 26 by adjusting the position of the nut 32.

It should be noted that the wafer brush 22 is preferably in the shape of a frustum. The wafer brush has a tapered surface 24, and the tapered surface 24 defines a bottom surface 34 and a top surface 36 of the wafer brush 22. The bottom surface 34 is away from the fixing element 26, and the top surface 36 contacts the fixing element 26. Moreover, the bottom surface 34 is smaller than the top surface 36. Referring to FIG. 3, according to a preferred embodiment of the present invention, the tapered surface 34 and the top surface 36 of the wafer brush 22 define an included angle θ which is between 30 and 90 degrees, and preferably between 45 and 80 degrees so as to clean the side edge 16 entirely. Furthermore, the wafer brush 22 can be made of materials which have less hardness than the wafer, and have the properties of high adhesiveness and stability, such as resin. Preferably, the wafer brush 22 is formed by poly vinyl alcohol (PVA), because PVA has excellent plasticity, emulsifying, and adhesive properties. It is also resistant to oil, grease and solvent. Therefore, PVA is suitable for forming the wafer brush 22 which has a special profile. Moreover, the wafer brush 22 made of PVA will not be consumed by the cleaning solution 28 because of its resistivity to solvent.

As illustrated in FIG. 2 and FIG. 4, at least an opening 38 is formed on the fixing element 26. A cleaning solution supplying tube (not shown) for supplying the cleaning solution 28 can be set within the fixing element 26. The exit of the cleaning solution supplying tube can be positioned at the opening 38, and the cleaning solution 28 can flow out from the opening 38. The cleaning solution 28 can be de-ionized wafer including conductive ions. The conductive ions may be formed by carbon dioxide dissolved in the de-ionized wafer.

Please refer to FIG. 1 and FIG. 4. When the side edge 16 including the bevel 17 is subjected to cleaning, the cleaning solution 28 flows out from the opening 38 and rinses the wafer brush 22. The wafer brush 22 becomes moist and elastic after the cleaning solution 28 flows onto the wafer brush 22. Therefore, contaminants on the side edge 16 can be easily absorbed on the wafer brush 22 and the wafer 14 will not be damaged because the hardness of the wafer brush 22 is less than that of the wafer 14. Moreover, the cleaning solution 28 not only can rinse the wafer brush 22, but also can wash down the containments adsorbed on the wafer brush 22. Therefore, when the cleaning element 20 is used for cleaning the side edge 16 of the wafer, the cleaning solution 28 flowing out from the fixing element 26 will wash the wafer brush 22 at the same time. The cleaning solution 28 flows out from the wafer brush 22 continuously during the cleaning of the side edge 16. Moreover, because the fixing element 26 is disposed above the wafer brush 22, the cleaning solution 28 flows from the upper part of the wafer brush 22 to the lower part of the wafer brush 22. In this way, the tapered surface 24 can be entirely washed and rinsed by the cleaning solution 28. The containments or peelings on the tapered surface 24 can be removed sufficiently, and the wafer brush 22 can absorb sufficient cleaning solution 28. In addition, because the wafer brush 22 has a bottom surface 34 smaller than the top surface 36, the containments or peelings on the tapered surface 24 can flow downward along the profile of the tapered surface 24 smoothly, and the containments or peelings will not get stuck on the wafer brush 22 or the nut 32. Furthermore, when the side edge 16 is being cleaned, the bottom surface 34 is substantially parallel to the front side or the back side of the wafer 14.

FIG. 5 depicts a three-dimensional graph of a cleaning element schematically according to a second preferred embodiment of the present invention, wherein like numerals designate like components in the drawing.

The difference between the cleaning element in FIG. 5 and in FIG. 2 is that the opening 38 is set on the side wall of the fixing element 26 in FIG. 5, and the opening 38 is set within the fixing element 26 in FIG. 2. Moreover, the cleaning solution supplying tube for providing cleaning liquid is not limited to be set inside the fixing element 26. For instance, the cleaning solution supplying tube can be set on a holder (not shown) positioned near the wafer brush 22, and the cleaning solution flowing from the cleaning solution supplying tube can thereby rinse the wafer brush 22.

The fixing element of the present invention has openings so that the cleaning solution can flow out from the openings to rinse the wafer brush, and the tapered surface of the wafer brush contacting the side edge of the wafer can adsorb containments or peelings on the side edge. Furthermore, the cleaning solution can wash down the containments or peelings adsorbed on the wafer brush.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.

Claims

1. A wafer side edge cleaning apparatus comprising:

a wafer stage for holding and rotating a wafer, wherein the wafer has a side edge; and

a cleaning element comprising: a fixing element; and a wafer brush fixed onto the fixing element, wherein the wafer brush has a tapered surface contacting the side edge of the wafer, the tapered surface defines a bottom surface and a top surface of the wafer brush, the bottom surface is away from the fixing element, the top surface contacts the fixing element, and the bottom surface is smaller than the top surface, and wherein a cleaning solution rinses the wafer brush when the side edge of the wafer is subject to cleaning by the wafer brush.

2. The wafer side edge cleaning apparatus of claim 1, wherein the tapered surface and the top surface define an included angle between 30 and 90 degrees.

3. The wafer side edge cleaning apparatus of claim 2, wherein the included angle is between 45 and 80 degrees.

4. The wafer side edge cleaning apparatus of claim 1, wherein the fixing element comprises at least one opening and the cleaning solution flows out from the opening.

5. The wafer side edge cleaning apparatus of claim 1, wherein the cleaning solution comprises de-ionized water.

6. The wafer side edge cleaning apparatus of claim 5, wherein the cleaning solution comprises conductive ions.

7. The wafer side edge cleaning apparatus of claim 1, wherein the wafer brush comprises resin.

8. The wafer side edge cleaning apparatus of claim 7, wherein the wafer brush comprises poly vinyl alcohol (PVA).

9. The wafer side edge cleaning apparatus of claim 1, wherein when the side edge of the wafer is subject to cleaning, the wafer is rotated to a first direction, and the wafer brush is rotated to a second direction so that contaminants on the side edge can be adsorbed on the wafer brush.

10. The wafer side edge cleaning apparatus of claim 1, further comprising a bolt disposed under the fixing element and penetrating the wafer brush, and a nut disposed under the wafer brush and screwed on the bolt to fix the wafer brush on the fixing element.

11. The wafer side edge cleaning apparatus of claim 1, wherein the side edge of the wafer comprises a bevel.