JP3812970B2 - Polishing apparatus and polishing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polishing apparatus used for surface polishing of a semiconductor wafer or the like, and more particularly to a polishing apparatus, a polishing method , and a polishing pad in which a polishing slurry (abrasive liquid) supply hole or the like is provided at the center of a polishing surface plate.
[0002]
[Prior art]
The surface polishing of the semiconductor wafer is performed in a semiconductor wafer manufacturing process, a semiconductor element forming process on the semiconductor wafer, or the like. For polishing the surface of the semiconductor wafer, a polishing apparatus using a polishing pad is employed.
[0003]
FIG. 5 is a schematic longitudinal sectional view showing a wafer polishing apparatus. The polishing pad 11 is attached to a polishing surface plate 31, and a wafer mounting portion 42 is provided on the sample stage 41 so as to face the polishing pad 11. The wafer S is placed on the wafer placement unit 42. The polishing surface plate 31, the sample stage 41, and the wafer mounting unit 42 are configured to be rotatable around their respective axis centers. In addition, a retainer 43 is provided on the outer peripheral portion of the wafer S so as not to cause surface sag in the wafer S during polishing.
[0004]
For polishing the wafer S, while supplying a polishing slurry to the surface of the polishing pad 11, the wafer mounting portion 42 is rotated (autorotated) and either one or both of the polishing platen 31 and the sample table 41 are rotated (revolved). In this state, the polishing pad 11 attached to the polishing surface plate 31 is pressed against the wafer S held on the wafer mounting portion 42. Due to the relative rotation between the wafer S and the polishing pad, the surface of the wafer S is polished with high precision by the fine abrasive particles in the polishing slurry.
[0005]
FIG. 6 is a schematic plan view of the sample stage of the wafer polishing apparatus, showing the movement of the wafer relative to the polishing pad. The wafer S rotates around the center of the wafer S by the rotation of the wafer mounting portion 42 and revolves around the central axis of the polishing pad by the rotation of the sample table 41 and the polishing surface plate (not shown).
[0006]
In order to perform high-precision processing on the surface of a wafer, it is necessary that the surface on which the polishing pad of the polishing surface plate is attached has high flatness and that the polishing pad is properly attached to the polishing surface plate. is there.
[0007]
The polishing pad is attached to the polishing surface plate mainly by a method of attaching using an adhesive or a double-sided tape. However, this method has the following problems.
[0008]
When the polishing pad is attached to the polishing surface plate, air bubbles may be mixed between the polishing pad and the polishing surface plate, or the polishing pad may be wrinkled. In this case, since the surface of the polishing pad facing the wafer is uneven, the polishing pressure in the wafer surface varies, and as a result, the amount of polishing in the wafer surface varies, and high-precision polishing cannot be performed.
[0009]
Since the polishing pad is worn out by friction with the wafer generated through the abrasive particles, the polishing pad is replaced every predetermined time. Each time this polishing pad is replaced, it is necessary to attach the polishing pad correctly while preventing air bubbles from entering between the polishing pad and the polishing platen for the reasons described above. In addition, the work takes a lot of time. In particular, it takes a lot of time to remove the adhesive remaining on the surface of the polishing platen after peeling off the used polishing pad and clean the surface.
[0010]
Therefore, as a method for solving these problems, a method has been proposed in which a pad fixing ring is attached to the outer peripheral portion of the polishing pad, and this ring is fixed to the polishing surface plate with a screw so that the polishing pad is lifted on the polishing surface plate. ing. According to this method, since the adhesive is not used, the above-mentioned problems caused by the adhesive can be solved.
[0011]
[Problems to be solved by the invention]
However, the method of lifting the polishing pad on the polishing surface plate using this pad fixing ring stretches as the polishing pad is used. Therefore, it is necessary to occasionally tighten the screw that attaches the pad fixing ring to the polishing surface plate to lift the polishing pad. is there. If this elongation is left as it is, wrinkles occur on the surface of the polishing pad, which adversely affects the polishing of the wafer.
[0012]
The present invention has been made to solve such problems, and can easily attach a polishing pad to a polishing surface plate, and automatically absorbs the elongation even when the polishing pad is elongated. An object of the present invention is to provide a polishing apparatus and a polishing method capable of polishing a wafer with high accuracy and stability, and to provide a polishing pad used in such a polishing apparatus and polishing method .
[0013]
The polishing apparatus of the present invention is a polishing apparatus including a polishing surface plate having a polishing pad adherent surface, a pad center holding plate for holding the center of the polishing pad, and a pad outer edge holding for holding an outer edge portion of the polishing pad. a plate, a mechanism for attaching and detaching said pad central holding plate to the polishing platen, the pad outer retaining plate is connected to each of the plurality of pull portions of the plurality of locations of the pad outer retaining plate each pull, the polishing And a tension means for applying a tension to the pad and attaching the pad to the polishing surface plate.
In the polishing apparatus of the present invention, the stretching means pulls each of the plurality of pulling portions of the pad outer edge holding plate with a constant tension .
In the polishing apparatus according to the present invention, the pad center holding plate includes a supply hole for polishing slurry .
The polishing method of the present invention, the polishing pad to the polishing platen of the above-described polishing apparatus are adhered, characterized by polishing the wafer.
[0014]
According to the onset bright, it is not necessary to use an adhesive to an adherend to the polishing platen of the polishing pad, it does not occur irregularities of the polishing pad surface by inclusion of air bubbles. Moreover, the troublesome work of removing the adhesive on the surface of the polishing surface plate is unnecessary.
[0015]
A constant tension is applied to the polishing pad attached to the polishing surface plate by pulling a plurality of locations on the pad outer edge holding plate. Therefore, even if the polishing pad is stretched, the stretch is absorbed and wrinkles are not generated. In addition, the polishing pad can be replaced semi-automatically.
[0016]
Furthermore, since the polishing pad is fixed on both sides of the central portion and the peripheral portion, the polishing pad is more stably lifted. In addition, there is also an advantage that it is easy to provide a polishing slurry (abrasive liquid) supply hole in the center of the polishing surface plate.
[0017]
Further, the wafer can be polished with high accuracy over a long period of time by attaching the polishing pad to the polishing surface plate of the polishing apparatus and polishing the wafer.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
An example of the polishing apparatus of the present invention will be described. An example of the polishing apparatus of the present invention is the polishing apparatus shown in FIG. 5 and FIG. 6, and only the part where the polishing pad is attached to the polishing surface plate is different from the conventional one.
[0019]
FIG. 1 is a half sectional view of a polishing surface plate portion of a polishing apparatus according to an embodiment of the present invention. A state in which the polishing pad 11 is already stretched on the pad-attached surface of the polishing surface plate 31 is shown. A polishing slurry supply hole 33 is provided at the center of the polishing surface plate 31. A polishing slurry supply hole 11 a is also provided in the center of the polishing pad 11.
[0020]
The pad center portion 11b of the polishing pad 11 is a pad center holding plate 14 composed of a center holding lower plate 12 and a center holding upper plate 13, and is sandwiched from both sides and fixed with bolts (not shown). The pad center holding plate 14 is attached to a recess 32 in the center of the polishing pad attachment surface of the polishing surface plate 31.
[0021]
The pad outer edge portion 11d of the polishing pad 11 is a pad outer edge holding plate 20 composed of an outer edge holding lower plate 18 and an outer edge holding upper plate 19 each having a substantially ring shape, and is sandwiched from both sides and fixed with bolts. By hooking the hook 21 of the outer edge holding upper plate 19 to the hook 22 at the lower end of the rod 23, the pad outer edge holding plate 20 is connected to the rod 23 of the air cylinder 25, and the polishing pad 11 is driven with a constant tension by driving the air cylinder 25. Is attached to the polishing surface plate 31.
[0022]
Of the polishing pad 11, the pad main body 11c that is in close contact with the polishing surface plate 31 is used for polishing the wafer.
[0023]
The pad center holding plate 14 and the pad outer edge holding plate 20 are made of a material having chemical resistance against chemicals such as alkalis and acids, and a material on which the polishing slurry is difficult to adhere, such as stainless steel or Teflon (registered trademark). It is preferable to produce by. The same applies to bolts.
[0024]
FIG. 2 is a bottom view of the polishing surface plate on which the polishing pad of the polishing apparatus of the present invention is attached. 51 and 52 are bolts.
[0025]
A method of stretching the polishing pad 11 on the polishing surface plate 31 will be described with reference to FIG.
[0026]
(1) The pad center holding plate 14 and the pad outer edge holding plate 20 are attached to the polishing pad 11 with bolts.
[0027]
(2) The pad center holding plate 14 is attached to the concave portion 32 at the center of the polishing surface plate 31 and the hook 21 of the pad outer edge holding plate 20 is hooked on the hook 22 at the tip of the rod 23 of the air cylinder 25.
[0028]
(3) The air cylinder 25 is driven and the pad outer edge holding plate 20 is pulled upward with a constant tension, and the polishing pad 11 is pulled up on the polishing surface plate 31.
[0029]
The attachment part of the pad center holding plate 14 to the polishing surface plate 31 will be described.
[0030]
FIG. 3 is a partially enlarged view of the central portion of the polishing pad deposition surface of the polishing surface plate of FIG. A groove 31b is provided on the side wall of the recess 32 at the center of the polishing pad surface of the polishing surface plate 31 so as to project inward. Further, the pad center holding upper plate 13 is provided with a protruding portion 13b protruding outward. It is attached by placing the protruding portion 13b of the pad center holding upper plate 13 in this groove 31b of the polishing surface plate 31. Reference numerals 12a and 13a denote polishing slurry supply holes provided in the pad center holding lower plate 12 and the pad center holding upper plate 13, respectively.
[0031]
4A and 4B are cross-sectional views taken along the line AA of FIG. 3, in which FIG. 4A illustrates a state in which the pad center holding plate is pushed up into the central recess of the polishing surface plate 31, and FIG. It is a figure to do.
[0032]
A method of attaching the pad center holding plate 14 (upper plate 13) to the polishing surface plate 31 is as follows.
[0033]
(1) The pad center holding plate 14 (upper plate 13) is brought under the recess 32 of the polishing surface plate 31. The pad center holding plate 14 (upper plate 13) is pushed up to the concave portion 32 at the center of the polishing surface plate 31 (FIG. 4A).
[0034]
{Circle around (2)} The pad center holding plate 14 (upper plate 13) is rotated, and the protruding portion 13b projecting outside the pad center holding upper plate 13 is placed on the groove 31b of the polishing surface plate 31 (FIG. 4B).
[0035]
Moreover, what is necessary is just to reverse at the time of removal. In this way, the pad center holding plate 14 (upper plate 13) can be easily attached to and detached from the polishing surface plate 31. Note that if a step is provided in the circumferential direction of the groove 31b of the polishing surface plate 31, the protruding portion 13b of the pad center holding upper plate 13 can be prevented from moving in the circumferential direction.
[0036]
As described above, since this polishing apparatus attaches the polishing pad to the polishing surface plate by pulling a plurality of portions of the pad outer edge holding plate, a constant tension can always be applied to the polishing pad. Therefore, even if the polishing pad is stretched, the stretch is absorbed and wrinkles are not generated. In addition, the polishing pad 11 can be easily attached. Further, the wafer can be polished with high accuracy over a long period of time by attaching the polishing pad to the polishing surface plate of the polishing apparatus and polishing the wafer.
[0037]
The pad center holding plate 14 and the pad outer edge holding plate 20 are each a pair of holding plates of an upper plate and a lower plate, but need only be able to hold the polishing pad and need to be a set of two. There is no.
[0038]
Needless to say, the mechanism for attaching and detaching the pad center holding plate 14 to and from the polishing surface plate 31 is not limited to that shown in the example of the present invention.
[0039]
The tension for lifting the polishing pad with the air cylinder may be determined from the material of the polishing pad and the area of the polishing pad.
[0040]
【Example】
Examples of the present invention will be described. The polishing apparatus used in this example is the polishing apparatus shown in FIGS. The polishing pad was held by a pair of pad center holding plate 14 and pad outer edge holding plate 20 each of which is a set. Pad central holding plate 14 and the pad outer retaining plate 20 made of stainless steel (JIS-SUS304), knurled in a portion in contact with the polishing pad 11, a Teflon (registered trademark) in the other surface Coated. As the polishing pad 11, a polishing pad made of polyester, which is easier to extend than other pads, was used. The outer diameter of the polishing pad 11 (pad body 11c) was 800 mm. The tension when lifting the polishing pad with the air cylinder 25 was 40 kgf.
[0041]
Using this polishing apparatus, an 8-inch silicon wafer having a thermal oxide film formed on the surface was polished. The polishing slurry is obtained by suspending silica in an aqueous KOH solution. With this polishing apparatus, the wafer could be polished with high accuracy over a long period of time without adjusting the tension of the polishing pad.
[0042]
Further, compared to the conventional method, the polishing pad can be easily replaced in a short time without requiring skill.
[0043]
【The invention's effect】
According to the polishing apparatus of the present invention, the polishing pad can be easily mounted on the polishing surface plate. Further, according to the polishing method using the polishing apparatus of the present invention, even if the polishing pad is elongated during polishing, the elongation is automatically absorbed, so that the wafer or the like can be polished with high accuracy.
[Brief description of the drawings]
FIG. 1 is a half sectional view of an example of a polishing surface plate portion of a polishing apparatus of the present invention.
FIG. 2 is a bottom view of a polishing surface plate to which a polishing pad of a polishing apparatus of the present invention is attached.
3 is a partially enlarged view of a central portion of a polishing pad deposition surface of the polishing surface plate of FIG. 1;
4 is a cross-sectional view taken along line AA of FIG. 3, in which (a) shows a state in which the pad center holding plate is pushed up into the concave portion at the center of the polishing surface plate, and (b) shows a state in which it is rotated.
FIG. 5 is a schematic longitudinal sectional view showing a wafer polishing apparatus.
FIG. 6 is a schematic plan view showing a wafer polishing apparatus.
[Explanation of symbols]
11 Polishing pad 12 Center holding lower plate 13 Center holding upper plate 13b Projection portion 14 of pad center holding upper plate Pad center holding plate 18 Outer edge holding lower plate 19 Outer edge holding upper plate 20 Pad outer edge holding plate 21 Hook 22 Hook 25 Air cylinder 31 Polishing surface plate 31b Groove 33 provided in recess of polishing surface plate Polishing slurry supply hole 41 Sample stand 42 Wafer mounting portion 43 Retainer 51 Bolt 52 Bolt S Wafer

Claims (4)

In a polishing apparatus including a polishing surface plate having a polishing pad deposition surface, a pad center holding plate for holding the center of the polishing pad, a pad outer edge holding plate for holding an outer edge portion of the polishing pad, and the pad center holding a mechanism for attaching and detaching the plate to the polishing platen, the pad outer retaining plate is connected to each of the plurality of pull portions of said plurality of positions of pads outer holding plate respectively tension, by the action of tension to the polishing pad the A polishing apparatus comprising: a stretching unit that adheres to a polishing surface plate.   The polishing apparatus according to claim 1, wherein the stretching means is configured to pull each of a plurality of pulling portions of the pad outer edge holding plate with a constant tension. The polishing apparatus according to claim 1, wherein the pad center holding plate includes a supply hole for polishing slurry . A polishing method comprising polishing a wafer by attaching a polishing pad to the polishing surface plate of the polishing apparatus according to claim 1 .

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