JPH10128653A - Device and method for polishing wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer polishing device generating a uniform polished characteristic of flatness or the like between each wafer and a uniform wafer polished amount in a surface. SOLUTION: A device comprises a wafer holder 12 horizontally holding a wafer 11 down facing rotated, abrasive cloth 14 opposed in parallel to the wafer holder 12 to polish the wafer, rotary polishing surface plate 16 holding the cloth 14 from a lower surface to have a rotary mechanism, supply pipe 18 supplying a slurry-shaped abrasive to a surface of the cloth 14, and a dresser 42 having a lift means lowering down an abrasive surface by a prescribed dress depth distance in each wafer polishing. Just after replacing a grinding plate of the dresser with a new plate, in accordance with advancing dressing, thickness of the cloth 14 is decreased, to be shallowly cut in accordance with progress of dressing. As a result, an upper surface of the cloth 14 has average roughness equivalent to an upper surface dressed by the dresser decreasing dressing power by wearing of an abrasive grain.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer polishing apparatus and a wafer polishing method which are most suitable for a chemical mechanical polishing method, and more particularly, it is possible to make the polishing characteristics between each wafer and the in-plane polishing amount of the wafer uniform. The present invention relates to a wafer polishing apparatus and a wafer polishing method.

[0002]

2. Description of the Related Art In recent years, as semiconductor devices have become more highly integrated, wiring widths of semiconductor elements have been increasingly miniaturized. As a result, wafer surface flattening technology having excellent flatness has been required, and chemical mechanical polishing has been required. The law is drawing attention. Here, a configuration of a conventional wafer polishing apparatus for polishing a wafer surface by a chemical mechanical polishing method will be described with reference to the drawings. FIG. 11 is a side view showing a conventional wafer polishing apparatus. The conventional wafer polishing apparatus 10 includes a wafer holder 12 that holds and rotates a wafer 11 downward, a polishing cloth 14 that faces the wafer holder 12 in parallel and polishes the wafer, and a rotary polishing apparatus that holds and rotates the polishing cloth 14 on the upper surface. A surface plate 16 and a supply pipe 18 for supplying a slurry-like abrasive 17 to the surface of the polishing cloth 14 are provided. The wafer holder 12 has a polishing head 20 for holding a wafer.
And a pressing device 23 having a retractable polishing head cylinder 22 vertically coupled to the polishing head 20 and having a rotating mechanism for rotating the polishing head 20 while applying a pressing force.
And are provided. The polishing cloth 14 is a rotary polishing platen 16.
It is fixed on the upper surface with double-sided tape. In addition, the wafer polishing apparatus 10 includes a dresser 24 for grinding and dressing the polishing pad 14. The dresser 24 includes a grinding plate 28 having a grinding surface formed by diamond abrasive grains 26 formed on a lower surface, a rotating shaft 30 for rotating the grinding plate 28,
A pressing / rotating mechanism 32 is provided above the rotating shaft 30, has a lifting mechanism and a horizontal moving mechanism, and applies a constant load to the grinding plate 28 via the rotating shaft 30. The lower end of the rotating shaft 30 of the dresser 24 and the grinding plate 28 are connected by a universal joint 34, and are configured as a tilt mechanism that allows the grinding plate 28 to be inclined to the surface of the polishing pad 14 during grinding.

When a wafer is polished using the wafer polishing apparatus 10, the rotary polishing table 16 is rotated at a predetermined rotation speed, and the polishing head 20 is pressed and controlled at a predetermined rotation speed by a polishing head cylinder 22. The wafer 11 is held by the polishing head 20 and is rotated at a predetermined rotation speed while controlling the pressing force. On the other hand, in order to maintain the surface shape of the polishing cloth 14 in a predetermined shape, after the polishing of the wafer 11 is completed, while rotating the grinding plate 28 of the dresser 24 at a predetermined rotation speed,
By pressing the polishing cloth 14 so as to have a predetermined constant pressure, the polishing is performed by grinding (hereinafter, referred to as a dress) to maintain the average roughness of the upper surface of the polishing cloth within a certain range.

[0004]

However, the conventional wafer polishing apparatus has the following problems. First, polishing characteristics such as flatness of a polished wafer differ between wafers processed before and after dressing, and the polishing characteristics of the wafer vary between wafers. Second, the in-plane uniformity of the polished wafer is poor. In view of the circumstances described above, an object of the present invention is to provide a wafer polishing apparatus and a wafer polishing apparatus in which polishing characteristics such as flatness are uniform among wafers and the polishing amount is uniform in a plane. Is to provide a way.

[0005]

The present inventor studied the process of dressing the polishing pad by performing a dressing experiment. FIGS. 6 (a), (b) and (c) show, respectively,
It is a side portion enlarged cross-sectional view showing a dress state of a dress early stage when the diamond abrasive grains 26 are worn, a dress state of a dress middle stage, and a surface shape of the polishing pad after the dress is finished.
FIGS. 7A, 7B, and 7C show the initial dress state, the middle dress state, and the surface after the dress immediately after replacing the grinding plate 28 with a new grinding plate 36, respectively. It is a side part enlarged sectional view showing a shape. FIGS. 8A, 8B, and 8C are cross-sectional views showing the undulating state of a new abrasive cloth before, during, and after dressing, respectively. FIGS. b) is a graph showing the pressing force distribution of the dresser 24 near the highest part 37 and the lowest part 38 at the height position of the polishing pad 14 in the middle stage of the dress, respectively.

When dressing is performed using a grinding plate on which diamond abrasive grains have been worn, the polishing pad 14 is cut to a small depth as shown in FIGS. 6 (a) and 6 (b), and is polished as shown in FIG. 6 (c). The upper surface of the cloth was finely sharpened. Next, a new grinding plate 36 having a high dressing ability is placed on the grinding plate 28.
7A and 7B, the polishing pad 14 is deeply shaved by the diamond abrasive grains 35, and the upper surface of the polishing pad 14 is removed as shown in FIG. 7C. It was deeply sharpened and the average roughness was rough. Further, it was also found that the new grinding plate has a variation in the amount of protrusion of the abrasive grains within a range of several μm, and therefore, the thickness to be dressed varies among the new grinding plates. Therefore, the amount of the wafer to be polished by the polishing cloth sharpened with a new grinding plate is
The polishing characteristics such as flatness were larger than the polishing amount of the wafer before the replacement of the grinding plate, and were different from the polishing characteristics before the replacement of the grinding plate. Since a constant load is applied to the dresser 24, as shown in FIGS. 8A and 8B, the polishing pad 14 is dressed at the highest portion 37 and the lowest portion 38 with the same pressing force. On the upper surface of the polishing cloth after the dressing, as shown in FIG. 8C, an uneven height distribution was generated.

Therefore, the present inventor does not apply a fixed load to the dresser, but lowers the polishing surface by a predetermined distance corresponding to the dress depth every time the wafer is polished, and performs a predetermined amount of dressing. It has been found that the dress depth on the upper surface of the polishing pad can be made substantially constant regardless of the wear of the grains. In addition, when the upper surface of the polishing cloth has undulation, by maintaining the dressing surface of the dresser at a predetermined horizontal height position from the rotary polishing platen and grinding, the pressing reaction force applied to the dresser is in a substantially uniform predetermined range. Once inside, the polishing cloth was found to be flat and dressed to a substantially uniform height, completing the present invention.

In order to achieve the above object, a wafer polishing apparatus according to the present invention comprises: a rotary polishing platen which holds a polishing cloth on a horizontal upper surface and rotates around a rotation axis perpendicular to the polishing cloth;
An abrasive supply unit for supplying a slurry-like abrasive to the polishing cloth surface, a wafer holder for holding the wafer and rotating the wafer about a rotation axis orthogonal to the wafer while pressing the rotating polishing cloth, and projecting abrasive grains A grinding plate having a ground surface on the lower surface thereof, and a dresser for grinding and polishing the polishing cloth by pressing the polishing surface against the polishing cloth while rotating the grinding plate around a rotation axis orthogonal to the grinding surface. In the wafer polishing apparatus, the dresser holds the grinding plate such that the grinding surface of the grinding plate is parallel to the upper surface of the rotary polishing platen, and moves a predetermined distance toward the upper surface with the upper surface of the rotary polishing platen as a reference surface. It is characterized in that it is provided with elevating means for lowering the grinding plate and maintaining the grinding surface at that position.

As the elevating means of the present invention, a known elevating device composed of components such as an electric motor and a ball screw can be used. As a preferred embodiment of the present invention, the dresser includes a measuring device for measuring a pressing reaction force received from the polishing cloth when the polishing surface comes into contact with and presses the polishing surface. The measuring device is, for example, a load cell.

In order to polish a wafer using the wafer polishing apparatus according to the preferred embodiment of the present invention, each time one wafer is polished, the grinding plate is lowered by a predetermined distance, for example, a dress depth. It is brought into contact with the polishing cloth held on the upper surface of the rotary polishing table. Next, when the grinding plate is rotated to dress the polishing cloth, the dressing of the polishing cloth is completed when the pressing reaction force measured by the measuring device falls within a predetermined range substantially uniformly within the plane of the polishing cloth. As a result, even immediately after replacing the grinding plate with a new one, the average roughness formed on the upper surface of the polishing cloth by dressing is the same as the average roughness formed when the abrasive particles wear and the dressing ability is reduced. Become. Therefore, the polished characteristics such as flatness of the wafer polished after the dressing are substantially the same as the polished characteristics of the wafer polished before the dressing.

Further, in order to use a wafer polishing apparatus according to a preferred embodiment of the present invention to make a polishing cloth having undulations on the upper surface, such as a new polishing cloth, to have a uniform horizontal height in the plane, a grinding plate is required. Is lowered, and the polishing surface is brought into contact with the thinnest region of the polishing cloth held on the upper surface of the rotary polishing platen, and is maintained in a state of being slightly pressed. Next, when the grinding plate is rotated to sharpen the polishing cloth, the grinding speed is high at the peaks of the polishing cloth due to the high pressure of the dresser, and the grinding speed is low at the valleys due to the low pressure of the dresser. As the dressing process progresses and the unevenness of the upper surface of the polishing cloth becomes smaller, the fluctuation width of the pressing reaction force measured by the measuring device becomes smaller. Further, when the pressing reaction force measured by the measuring device falls within a predetermined range substantially uniformly within the plane of the polishing pad, the dressing of the polishing pad is terminated. As a result, the horizontal height of the polishing cloth is uniform in the plane, and when the wafer is subsequently polished, the polishing amount of the wafer can be uniform in the plane.

[0012]

Embodiments of the present invention will be described below in more detail with reference to the accompanying drawings. Example 1 In this example, a dresser is provided with a load cell for measuring a pressing reaction force received from a polishing cloth by a grinding plate, and a mechanism for lowering a grinding surface by a predetermined dress depth distance every time a wafer is polished. This is an example of a polishing apparatus and an example of using the present wafer polishing apparatus to dress the average roughness of the upper surface of a polishing cloth within a predetermined range. FIG. 1 is a side view of the wafer polishing apparatus of the present embodiment. In the wafer polishing apparatus 40 of the present embodiment, a part of the dresser 42 is different from the dresser 24, and the other is the same as the conventional wafer polishing apparatus 10. Therefore, in the present embodiment, the same components are denoted by the same reference numerals. The description is omitted.

The dresser 42 includes a grinding plate 28 having a grinding surface on which diamond abrasive grains 26 are implanted and formed parallel to the upper surface of the rotary polishing platen 16 and a grinding plate 28 which is vertically connected to the grinding plate 28. Rotating shaft 4 to rotate
3, a pressing device 44 for lowering the grinding plate 28 by a predetermined distance via the rotating shaft 43 to apply a pressing force to the grinding surface, and a load cell 46 for measuring a pressing reaction force received by the pressing device 44.
And The lower end of the rotating shaft 43 is fixed to the grinding plate 28 in place of the tilt unlike the related art, so that the grinding plate 28 is always kept horizontal.

After polishing the wafer, the diamond abrasive grains 2
The worn grinding plate 6 is maintained at a position lowered by a predetermined distance, for example, the dress depth, from the position just dressed, and is brought into contact with the polishing cloth 14 held on the upper surface of the rotary polishing platen to dress. . FIG. 2 (a), (b) and (c)
5A and 5B are partial enlarged side sectional views showing a dress state in an initial stage of a dress, a dress state in a middle stage of the dress, and a surface shape of the polishing pad after the dressing, respectively, due to worn abrasive grains 26.
As shown in FIGS. 2A and 2B, the upper surface of the polishing pad 14 is shaved to a small depth. As a result, as shown in FIG. Next, after another wafer is newly polished, the grinding plate 28 of the dresser 42 is replaced with a new grinding plate 35, and dressing is performed using a dresser having extremely high dressing ability. 3A, 3B, and 3C respectively show a dress state in an initial stage of dressing, a dressing state in a middle stage of dressing by abrasive grains 36 of a grinding plate 35,
FIG. 3 is a side cross-sectional enlarged view illustrating a surface shape after a dress is completed. As shown in FIG. 3A, in the initial stage of the dress, the polishing pad 14 is shaved deeply, and the dress speed is high. As the dress progresses, the thickness of the polishing cloth 14 decreases, and FIG.
As shown in the figure, it is shallow. As a result, when the dressing is completed, the upper surface of the polishing cloth 14 is dressed with the worn diamond abrasive grains 26 as shown in FIG.
It has the same average roughness as the upper surface of the polishing cloth shown in (c).

Therefore, the characteristics to be polished such as flatness are the same between the wafers, and the polished amount of the wafer becomes uniform in the plane. The dresser 42 is provided with elevating means for moving down the polishing surface at a predetermined speed, and the dresser 42 is polished while polishing the wafer.
The same effect can be obtained even if dressing is performed.

Embodiment 2 In this embodiment, the wafer is polished to a uniform thickness by using the wafer polishing apparatus 40 of Embodiment 1 and maintaining the polishing surface at a predetermined horizontal height from the rotary polishing platen. Is an embodiment of a wafer polishing method for dressing as described above.

When undulations are formed on the upper surface of the polishing cloth, such as immediately after replacing the polishing cloth 14 with an unused polishing cloth 48,
First, the grinding plate 28 is lowered to the lowest position 52 at the height of the polishing pad 48, and the state is maintained in which the polishing surface slightly presses the polishing pad. Next, the rotating polishing table 16 and the dresser 42 are rotated to dress the upper surface of the polishing pad 48. FIG.
(A), (b) and (c) are cross-sectional views of the polishing cloth before, during, and after dressing, respectively, and FIG.
(A) and (b) show the vicinity of the highest part 50 and the lowest part 52 of the height position of the polishing pad 48 in the middle stage of the dress, respectively.
It is a graph which shows the distribution of the pressing force of the dresser 42 in the vicinity. As can be seen from FIGS. 5A and 5B, the dresser 42 dresses with a high pressing force at the highest portion 50 and a low pressing force at the lowest portion 52 from the beginning of the dressing, and is shown in FIG. 4B. As described above, the horizontal height position of the dresser 42 is constant. As a result, the polishing cloth 48 is in the initial stage of the dress.
As shown in FIG. 4 (a), it is shaved deeply, and as the dress advances, as shown in FIG. 4 (b), it is shaved shallowly.
When the measurement value of the load cell 46 is monitored and the dressing by the dresser 42 is completed when the pressing reaction force received by the pressing device 44 falls within a substantially uniform predetermined range, FIG.
As shown in (c), the upper surface of the polishing pad 48 is formed in an arc shape having a range of undulations of several μm to several tens μm, and is a flat surface having a substantially uniform height.

Therefore, the characteristics to be polished such as flatness are almost the same as the characteristics to be polished of the wafer polished before dressing. Further, since the stress distribution generated on the wafer during polishing becomes uniform in the wafer surface, the amount of the wafer to be polished becomes uniform in the surface.

[0019]

According to the present invention, the dresser of the wafer polishing apparatus holds the grinding plate so that the grinding surface of the grinding plate is parallel to the upper surface of the rotary polishing platen, and lowers the grinding plate by a predetermined distance. And a raising and lowering means for maintaining the polishing surface at that position, whereby the polishing cloth having undulations on the upper surface can be made flat and uniform in height. The amount can be uniform in the plane. Also, immediately after replacing the dresser's grinding plate with a new one, the average roughness formed on the polishing cloth upper surface by dressing is the same as the average roughness formed when the abrasive grains wear and the dressing ability is reduced. When the wafer is polished after dressing, the wafer polishing characteristics such as flatness become almost the same as the wafer polishing characteristics polished before dressing.

[Brief description of the drawings]

FIG. 1 is a side view of a wafer polishing apparatus according to a first embodiment.

FIGS. 2 (a), (b) and (c) show, respectively,
FIG. 3 is a side enlarged cross-sectional view illustrating a dress state in an initial stage of a dress, a dress state in a middle stage of the dress, and a surface shape of the polishing pad after the dress is completed, according to the first embodiment.

FIGS. 3 (a), (b) and (c) show, respectively,
FIG. 3 is a partially enlarged cross-sectional side view showing a dress state in an initial stage of dressing, a dressing state in a middle stage of dressing, and a surface shape of the polishing pad after dressing by using abrasive grains of a new grinding plate in Example 1.

FIG. 4A, FIG. 4B and FIG.
FIG. 4 shows sectional views of a polishing cloth before dressing, middle dressing and after dressing in Example 2.

FIGS. 5A and 5B are graphs respectively showing the pressure distribution of the dresser at the highest part and the lowest part of the height position of the polishing pad in the middle stage of the dressing.

6 (a), 6 (b) and 6 (c) are respectively
It is a side part enlarged sectional view showing a dress state of a dress early stage of a dress by a worn abrasive grain, a dress state of a dress middle stage, and a surface shape of a polishing pad after a dress is completed.

FIGS. 7 (a), (b) and (c) show, respectively,
It is a side part enlarged sectional view showing a dress state of an initial stage of a dress, a dress state of a middle stage of a dress by abrasive grains of a new grinding plate, and a surface shape of a polishing cloth after a dress.

8 (a), (b) and (c) are respectively
FIG. 1 shows cross-sectional views of a conventional polishing cloth before, during, and after dressing.

FIGS. 9A and 9B are graphs respectively showing the pressure distribution of the dresser at the highest part and the lowest part of the height position of the polishing pad in the middle stage of the dressing.

FIG. 10 is a side view of a conventional wafer polishing apparatus.

[Explanation of symbols]

10 wafer polishing apparatus, 11 wafer, 12 wafer holder, 14 polishing cloth, 16 rotary polishing platen,
17 abrasive, 18 supply pipe, 20 polishing head, 22 polishing head cylinder, 23 pressing device, 24 dresser, 26 diamond abrasive grains, 2
8 Grinding plate, 30 Rotating shaft, 32 Press rotation mechanism, 34 Universal joint, 35 Diamond abrasive grains, 36 Grinding plate, 37 Maximum part, 38 Minimum part, 40 wafer polishing device, 4
2 ... dresser, 43 ... rotating shaft, 44 ... pressing device,
46 load cell, 48 polishing cloth, 50 highest part, 52 lowest part.

Claims (4)

[Claims] A rotary polishing platen for holding a polishing cloth on a horizontal upper surface and rotating around a rotation axis orthogonal to the polishing cloth; an abrasive supply section for supplying a slurry-like abrasive to the polishing cloth surface; A wafer holder for holding the wafer and rotating the wafer around a rotation axis orthogonal to the wafer while pressing against the rotating polishing cloth, and a grinding plate having a grinding surface on the lower surface on which abrasive grains are projected are provided. Grinding the polishing cloth by pressing the polishing surface against the polishing cloth while rotating the grinding plate around the rotation axis to
In a wafer polishing apparatus provided with a dresser for dressing, the dresser holds the grinding plate so that the grinding surface of the grinding plate is parallel to the upper surface of the rotary polishing platen, and uses the upper surface of the rotary polishing platen as a reference surface. A wafer polishing apparatus, comprising: lifting means for lowering a grinding plate by a predetermined distance toward an upper surface and maintaining a grinding surface at that position. 2. The dresser according to claim 1, wherein the dresser includes a measuring device for measuring a pressing reaction force received from the polishing surface when the polishing surface comes into contact with and presses the polishing surface. Wafer polishing equipment. 3. A method for polishing a wafer using the wafer polishing apparatus according to claim 2, wherein the polishing plate is lowered by a predetermined distance each time one wafer is polished, and the rotational polishing is performed. The polishing cloth held on the upper surface of the board is brought into contact with the polishing cloth, and then the grinding plate is rotated to sharpen the polishing cloth, and the pressing reaction force measured by the measuring device is almost uniformly within a predetermined range within the plane of the polishing cloth. A method of polishing a wafer, characterized in that dressing of a polishing cloth is completed when the polishing is completed. 4. A method for polishing a wafer using the wafer polishing apparatus according to claim 2, wherein the polishing plate is lowered when polishing the wafer.
The polishing surface is kept in a state in which the polishing surface is brought into contact with the thinnest region of the polishing cloth held on the upper surface of the rotary polishing platen and pressed slightly, and then the polishing plate is rotated to sharpen the polishing cloth,
A method of polishing a wafer, characterized in that dressing of the polishing cloth is terminated when the pressing reaction force measured by the measuring device is substantially uniformly within a predetermined range in the plane of the polishing cloth.