JPH10217114A - Wafer polishing method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the intra-plane uniformity in polishing a wafer by allowing an overflowing abrasive to stagnate in the specified position on a polishing pad, and thereby preventing the overflowing abrasive from stagnating in the gaps between the pad and the wafer periphery. SOLUTION: A polishing device 40 is composed of a surface plate 44 equipped with polishing pad 43, a holding mechanism 42 for wafer 50, and a supply mechanism 41 for an abrasive. By this device 40 with surface plate 44 rotated, a wafer 50 is polished when it slides on the pad 43 in contacting with the abrasive. At this time, the abrasive is hindered from overflowing onto the pad 43. The wafer 50 is polished by allowing it to make contact with the abrasive which is in impregnation in the pad 43.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for polishing a wafer and a polishing apparatus therefor.

[0002]

2. Description of the Related Art An example of a conventional method for polishing a wafer and an apparatus for polishing a wafer will be described with reference to FIGS. 3 to 5, the same components are denoted by the same reference numerals. In order to explain the outline of the configuration of the polishing apparatus 10, FIG.
FIG. 3B shows an arrow view from the line AA ′ shown in FIG. As shown in the figure, the polishing apparatus 10 includes an abrasive supply mechanism 11 for an abrasive, a wafer holding mechanism 12 for holding a wafer 20, and a polishing platen 14 on which a polishing pad 13 is mounted. Then, in order from the bottom, the polishing platen 14
Is formed in a short column shape, the polishing pad 13 is formed in a disk shape, and the wafer holding mechanism 12 is formed in a short column shape.
The diameter of the upper surface of the polishing pad 13 is longer than the diameter of the lower surface of the polishing pad 13. During polishing, the abrasive supplied from the abrasive supply mechanism 11 in an amount exceeding the amount that can be impregnated into the polishing pad 13 forms an abrasive layer 30 on the polishing pad 13.

[0003] Here, the wafer 2 is
A method of polishing 0 will be described. First, the abrasive supply mechanism 11
Supplies an abrasive to the polishing pad 13 from. While the polishing agent is impregnated in the polishing pad 13, a part thereof overflows on the polishing pad 13 and stays there to form the polishing agent layer 30. Next, the polishing platen 11 on which the polishing pad 13 is mounted and the wafer holding mechanism 12 approach each other from a separated state and rotate independently at the same rotation speed in the same direction. Then, at least the wafer 20 held by the wafer holding mechanism 12
The polishing pad 13 and the wafer holding mechanism 12 are sufficiently close to each other while rotating until the polishing pad 13 and the abrasive layer 30 formed on the polishing pad 13 come into contact with each other, and the wafer holding mechanism 12 swings while pressing the polishing pad 13. Move. The wafer 20 held by the wafer holding mechanism 12 slides on the abrasive layer 30 due to the rocking accompanied by the pressing, and is polished.

The composition of the polishing pad 13 required for the above polishing will be described with reference to FIG. Usually, the polishing pad 13 includes a fiber layer 13a made of a nonwoven fabric and a base layer 13b as shown in FIG. 4A, and a foam layer 13c made of a foam as shown in FIG. 4B. There is a base layer 13d. Therefore, the polishing pad 13 has a hollow portion in the upper layer and is impregnated with an abrasive or the like.

Here, in order to easily understand the state in which the wafer holding mechanism 12 presses the polishing pad 13 through the wafer 20 during polishing, an enlarged sectional view of a part of the wafer 20 and the polishing apparatus 10 is shown. FIG. 5 is a cross-sectional view of a main part. If the thickness of the wafer 20 is, for example, 720 μm as shown in the figure, about 10 μm is compressed, a step is generated in the polishing pad 13, and a gap 1 is formed between the outer periphery of the wafer 20 and the polishing pad 13.
5 results. Therefore, the abrasive that has overflowed without being completely impregnated into the polishing pad 13 and remains on the polishing pad 13 as the abrasive layer 30 enters the gap 15 along the upper surface of the polishing pad 13 and stays there.

Further, as shown in FIG. 5, the polishing pad 13 being polished is pressed and compressed, so that the abrasive of the compressed thickness oozes out on the polishing pad 13 and overflows. To stay further. For this reason,
When the polishing agent overflows on the polishing pad 13, the wafer 20 is polished in a state where the polishing agent constantly stays in the gap 15.

[0007]

However, it is difficult to uniformly polish a wafer with a conventional polishing apparatus and a conventional polishing method.

This is because the polishing agent constantly overflows on the polishing pad during polishing. The overflowing abrasive passes over the polishing pad and stays in the gap between the outer peripheral portion of the wafer and the polishing pad generated during polishing, and the abrasive staying in the gap comes into contact with the outer peripheral portion of the wafer to polish. .

[0009] To supplement here, the usual abrasive is a dispersion of silicon oxide or cerium oxide having a diameter of several tens to several hundreds nm in an alkaline aqueous solution. The abrasive easily stays in the usual gap between the abrasive and the abrasive.

[0010] As described above, a gap is formed between the outer peripheral portion of the wafer and the polishing pad, and the overflowing abrasive stagnates in the gap. There is no gap similar to the above, and there is no room for the abrasive to stay. Therefore, the amount of the abrasive supplied to the wafer varies depending on the portion, and the polishing rate of the wafer becomes non-uniform.

The overflowing abrasive not only hinders the uniformity of the polishing, but also may be discharged from the polishing pad to the outside without being used for polishing, so that the cost of the unused abrasive is undesirable. . For this reason, the overflow of the polishing agent should be reduced, but it is necessary for stabilizing the holding of the wafer and for removing foreign substances that cause scratches.

Although the wafer holding mechanism is provided with a guide ring, the retention of the abrasive in the gap can be reduced, but the overflow cannot be reduced.

Nevertheless, the production of a 1 μm-accurate wafer, the flattening of the wiring layer interval during the 0.1 μm-accuracy device process, the flattening of the bonding surface during the SOI structure production process, and the production of a silicon thin film are described above. This is a problem because polishing is performed.

[0014]

SUMMARY OF THE INVENTION The present invention is a method for polishing a wafer and an apparatus for polishing a wafer which have been made to solve the above-mentioned problems.

That is, in the case of a method for polishing a wafer, a polishing pad is mounted on a rotating polishing table, and a wafer held by a wafer holding mechanism is arranged on the polishing pad, and a polishing agent is provided. And polishing the wafer by sliding on the polishing pad while bringing the wafer into contact with the polishing agent, wherein the polishing agent supplied to the polishing pad is polished on the polishing pad. A polishing method for a wafer, characterized in that the polishing agent is supplied in a state in which the polishing pad does not overflow, and in the case of a wafer polishing apparatus, a polishing platen on which a polishing pad is mounted, and a polishing plate above the polishing pad. A wafer holding mechanism for arranging a wafer held in the polishing pad, a polishing agent supply mechanism for supplying a polishing agent on the polishing pad, and an amount of polishing agent that can be impregnated in the polishing pad. A polishing apparatus of a wafer consisting of an adjusting mechanism of abrasive adjusting regulating the abrasive overflows onto the polishing pad at a predetermined position by supplying Te.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a wafer polishing method and a wafer polishing apparatus according to the present invention will be described with reference to FIGS. 1 and 2, the same components are denoted by the same reference numerals. First, in order to explain the configuration of the polishing apparatus 40 of the first embodiment, FIG. As shown in FIG. 1A, the polishing agent supply mechanism 41, the wafer holding mechanism 42, and the adjustment mechanism 45 are arranged above the polishing pad 43, respectively. FIG.
FIG. 1B shows a cross-sectional view taken along a line BB ′ in FIG. 1A and perpendicular to the upper surface of the polishing pad 43. As shown in FIG. 1B, the polishing apparatus 40 includes a polishing agent supply mechanism 41, a wafer holding mechanism 42, and an adjustment mechanism 45 above the polishing pad 43. The adjustment mechanism 45 is supported by a support mechanism 45a, and the wafer holding mechanism 42 holds the wafer 50 during polishing. The polishing platen 44 is formed in a short column shape, the polishing pad 43 is formed in a disk shape, and the wafer holding mechanism 42 is formed in a short column shape having an area smaller than the upper surface of the polishing platen 44 in order from the bottom. During polishing, the abrasive supplied from the abrasive supply mechanism 41 stays on the polishing pad 43 closer to the abrasive supply mechanism 41 than the adjustment mechanism 45 to form the abrasive layer 60.

The range in which the wafer 50 slides on the polishing pad 43 is shown as a polishing track 46 in FIG. In FIG. 1A, the polishing track 46 is represented by an annular shape having a width of the wafer diameter. However, in addition, an annular shape having a width wider than the wafer diameter, a circular shape having a radius longer than the wafer diameter, or a wafer diameter is represented. It becomes a one-stroke curve or the like with the line width.

The adjusting mechanism 45 is not limited to the prismatic shape and the arrangement position shown in FIG. 1, but is formed so as to be in contact with the entire area of the polishing track 46 during one rotation of the polishing pad 43, so as to hold the wafer. What is necessary is just to arrange | position to the abrasive supply mechanism 41 side rather than the mechanism 42. Therefore, the shape of the adjusting mechanism 45 may be, for example, a spatula or a spatula-like shape,
It is preferable that the arrangement position straddles the center of the surface of the polishing pad 43.

Here, a method of polishing the wafer 50 using the polishing apparatus 40 of the first embodiment will be described. First, an abrasive is supplied from the abrasive supply mechanism 41 to the polishing pad 43. This polishing agent is supplied in an amount exceeding the amount that can be impregnated into the polishing pad 43, and a part of the polishing agent overflows and stays on the polishing pad 43 to form the polishing agent layer 60. Next, the polishing platen 41 on which the polishing pad 43 is mounted and the wafer holding mechanism 42 approach each other in a separated state and rotate independently at the same rotational speed in the same direction.

By this rotation, the adjusting mechanism 45 disposed in close contact with the polishing pad 43 serves as a wiper for the polishing pad 43 to spread the abrasive evenly and to stay on the upper surface of the polishing pad 43 on the upper side in the rotation direction. In other words, on the polishing pad 43, with the adjustment mechanism 45 as a boundary, the overflowing abrasive is retained on the upper surface in the rotating direction, but the abrasive is adjusted so as not to be retained on the lower surface. In order to further facilitate the adjustment of the polishing agent, the adjusting mechanism 45 may be provided with a pH measuring function to determine the concentration of the polishing agent 43 which usually shows alkalinity in the polishing pad 43.

With the polishing agent on the polishing pad 43 adjusted, the polishing pad 43 and the wafer holding mechanism 42 are sufficiently close to each other, and the wafer 50 contacts the lower surface in the rotation direction. Then, as in the conventional case, the wafer 50 is
The wafer 50 is polished on the polishing pad 43 while coming into contact with the polishing agent impregnated in the polishing pad 43 by sliding on the lower surface in the rotation direction of the region of the polishing track 46 on the polishing pad 3.

During polishing, the adjusting mechanism 45 also prevents the polishing agent of the compressed thickness of the polishing pad 43 from oozing onto the surface of the polishing pad 43 and overflowing by pressing the polishing pad 43 in advance. It is possible.
As a result, the wafer 50 is polished in a state in which the abrasive does not overflow, and the in-plane uniformity of the amount of the abrasive supplied to the surface to be polished of the wafer 50 is improved.

FIG. 2 is a plan view of a main part of a polishing apparatus 10 according to a second embodiment. In FIG. 2, components that are the same as those in FIG. 1A and have the same function are denoted by the same names and the same reference numerals, and description thereof is omitted. As shown in FIG. 2, an adjusting mechanism 45 is provided on the outer circumference of the polishing track 46.
And an auxiliary adjusting mechanism 47 for stopping the abrasive on the side of the abrasive supply mechanism 41 in contact with the surface.

In FIG. 2, the shape of the auxiliary adjustment mechanism 47 is a part of an annular shape. However, since the auxiliary adjustment mechanism 47 is provided to prevent the abrasive from overflowing from the polishing pad 43, the shape and arrangement shown in FIG. It is not limited to. In other words, the auxiliary adjustment mechanism 47 is larger than the wafer holding mechanism 42 in the polishing agent supply mechanism 41.
What is necessary is just to arrange | position so that an abrasive | polishing agent may be surrounded with the adjustment mechanism 45 by the side. For this reason, the shape of the auxiliary adjustment mechanism 47 may be, for example, a shape obtained by cutting a part of a tire mold.

A polishing method resulting from the provision of the auxiliary adjusting mechanism 47 will be described below, and the other polishing procedures are the same as those in the first embodiment, and a description thereof will be omitted. The auxiliary adjustment mechanism 47 is provided with the polishing pad 43 together with the adjustment mechanism 45.
The auxiliary adjusting mechanism 47 also functions as a weir for the abrasive flowing out from above the polishing pad 43 to the outside. Therefore, the abrasive is surrounded by the adjusting mechanism 45 and the auxiliary adjusting mechanism 47,
The polishing agent layer 60 is stored on the polishing pad 13 on the upstream side in the rotation direction with respect to the adjustment mechanism 45.

The abrasive of the abrasive layer 60, which is stored and surrounded by the adjusting mechanism 45 and the auxiliary adjusting mechanism 47, is evenly spread to the adjusting mechanism 45 with the rotation of the polishing pad 43, and is successively formed on the polishing pad. 43 is impregnated in the hollow portion where the abrasive can be impregnated. For this reason, the polishing pad 43 can be impregnated with the polishing agent more efficiently than before, and the amount of the polishing agent used can be reduced.

A third embodiment will be described with reference to FIG. First, the configuration of the polishing apparatus of the third embodiment is obtained by removing the adjusting mechanism 45 and the supporting mechanism 45a from the polishing apparatus 40 shown in FIG. All examples are provided.

Here, the elements of the third embodiment which are shown in FIG. 1 are denoted by the same reference numerals as those shown in FIG. 1, and a method of polishing the wafer 50 using the polishing apparatus 40 is described. explain. First, the supply of the polishing agent is adjusted so that the entire supplied amount is impregnated from the position where the polishing agent is supplied on the polishing pad 43 to the time when the polishing agent reaches the outer peripheral portion of the wafer 50 by rotation. The supply amount of the abrasive is variable depending on the rotation speed of the polishing pad 43, the abrasive impregnation speed, the occupation ratio of the hollow portion, and the like. Thus, the polishing is performed by sliding the wafer 50 on the polishing pad 43 in the same manner as in the first embodiment, without causing the abrasive to overflow onto the polishing pad 43.

Finally, a fourth embodiment will be described with reference to FIG. First, the configuration of the polishing apparatus according to the fourth embodiment is such that the adjustment mechanism 45 and the support mechanism 45a are removed from the polishing apparatus 40 shown in FIG. 1 and an air blow mechanism (not shown) for blowing air onto the polishing pad 43 is provided. It is.

Here, the elements shown in FIG. 1 which are the elements of the fourth embodiment are denoted by the same reference numerals as those shown in FIG. 1, and the polishing method will be described. The wafer 50 is slid on the polishing pad 43 and polished in the same manner as in the first embodiment, while blowing and removing the overflowing abrasive on the polishing pad 43 by blowing air from the air blow mechanism. In this case, it is preferable that the air be blown toward the rotation direction of the polishing pad 43 rather than the wafer holding mechanism 42, and an air blow mechanism may be arranged at a position above the adjustment mechanism 45 in FIG. As an application of the fourth embodiment, a vacuum suction mechanism (not shown) or the like is provided instead of the air blow mechanism, and the overflowing abrasive on the polishing pad 43 is removed by suction. Also in this case, similarly to the case where the air blow mechanism is provided, a vacuum suction mechanism may be arranged at a position above the adjustment mechanism 45 in FIG.

[0031]

According to the present invention described above, the overflowing abrasive is retained at a predetermined position on the polishing pad, so that the overflowing abrasive is retained in the gap between the polishing pad and the outer peripheral portion of the wafer. This improves the in-plane uniformity of wafer polishing. In addition to retaining the overflowing abrasive at a predetermined position on the polishing pad, and impregnating the polishing pad more efficiently than before, the amount of abrasive supplied during polishing reduces the cost of the polishing process. Can be reduced.

By reducing the supply amount of the polishing agent,
Select the polishing pad and adjust the rotation speed of the polishing platen and the supply amount of the polishing agent, etc., to prevent the wafer from becoming unstable or the foreign matter causing the scratch to be adsorbed to the wafer. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a first embodiment.

FIG. 2 is a plan view of a main part of a second embodiment.

FIG. 3 is a schematic view of a conventional example.

FIG. 4 is a sectional view of a polishing pad.

FIG. 5 is a sectional view of a main part of a conventional example during polishing.

[Explanation of symbols]

41 Abrasive supply mechanism 42 Wafer holding mechanism 4
3 Polishing pad 44 Polishing surface plate 45 Adjusting mechanism 60 Wafer

Claims (6)

[Claims] 1. A polishing pad is mounted on a rotating polishing table, a wafer held by a wafer holding mechanism is arranged on the polishing pad, and an abrasive is supplied. A method of polishing a wafer by sliding on the polishing pad while making contact with the polishing pad, wherein the polishing agent supplied to the polishing pad is supplied in a state where the polishing agent does not overflow onto the polishing pad. A method of polishing a wafer, comprising: 2. A polishing platen on which a polishing pad is mounted, a wafer holding mechanism for arranging a wafer held above the polishing pad, and an abrasive supply mechanism for supplying an abrasive onto the polishing pad. A polishing apparatus for polishing a wafer, comprising: a polishing agent adjusting mechanism that adjusts and regulates an overflowing abrasive on the polishing pad to a predetermined position by being supplied in an amount exceeding the amount that the abrasive can be impregnated into the polishing pad. . 3. The wafer polishing apparatus according to claim 2, wherein the polishing agent adjusting mechanism controls the adjustment by blowing off the polishing agent overflowing onto the polishing pad by air. 4. The wafer polishing apparatus according to claim 2, wherein the polishing agent adjusting mechanism sucks the polishing agent overflowing onto the polishing pad by vacuum suction and regulates the polishing agent. 5. The polishing agent adjusting mechanism is characterized in that, after the adjusting mechanism, the polishing agent overflowing on the polishing pad is retained on the surface on the upper side in the rotation direction of the polishing pad, and the adjustment is regulated. 3. The wafer polishing apparatus according to claim 2, wherein: 6. The polishing agent, which is arranged on the upstream side of the polishing agent adjusting mechanism and along the outer periphery of the polishing pad and flows out of the polishing pad from the polishing pad, stays on the polishing pad. 4. The wafer polishing apparatus according to claim 3, further comprising a polishing auxiliary adjusting mechanism for preventing the polishing.