JP2001219364A - Abrasive pad, polishing method and method of manufacturing work piece by using abrasive pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constantly keep the deformation characteristic of an abrasive pad in polishing to stably polish a wafer. SOLUTION: A through hole is formed from a surface of the abrasive pad to the abrasive pad of a lower layer so that the gas or the liquid included in the abrasive pad of the lower layer are movable through the through hole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In the field of manufacturing semiconductor devices, miniaturization of elements and increase in the number of elements to be integrated have progressed, and it has become common knowledge that wiring is multilayered. In the case of multi-layered wiring, simply overlapping wiring via an interlayer insulating film causes unevenness on the surface of the interlayer insulating film, which affects exposure processing and the like.

[0003] Therefore, in the multilayer wiring technique, a major issue is how to improve the flatness of an interlayer insulating film (for example, an SiO2 film).

As a technique for improving the flatness of the interlayer insulating film,
For example, a CMP (Chemical Mech) for polishing the surface of an interlayer insulating film using a polishing liquid rich in solid phase reactivity with the interlayer insulating film.
Anical Polishing) technology is known.

As a polishing pad, a polishing pad having a two-layer structure as shown in FIG. 2B is widely used. That is, the upper polishing pad is formed of a hard polishing pad for reducing the unevenness of the wafer surface, and the lower pad is formed of a soft polishing pad for matching the upper polishing pad to the wafer. As the lower polishing pad, a nonwoven fabric having excellent elastic recovery characteristics is widely used. In the polishing process using a polishing pad, the wafer to be processed passes while being pressed onto the polishing pad, so the polishing pad is elastically deformed during polishing, and the polishing pad starts elastic recovery when the wafer has passed. I do. further,
When the polishing pad makes one rotation, the polishing pad is pressed against the wafer again to start deformation. That is, the polishing pad is periodically deformed and recovered by the polishing pressure from the wafer. On the other hand, during polishing, the surface of the polishing pad is covered with the polishing slurry. The polishing slurry contacts the surface of the polishing pad and the side surface of the polishing pad, and also touches the underlying polishing pad. The gas contained in the lower layer pad by polishing flows into and out of the atmosphere from the outer periphery of the polishing pad with the deformation and recovery of the lower layer polishing pad. At this time, the slurry enters the lower polishing pad together with the gas flow in and out, and the slurry permeates the lower polishing pad from the outer periphery toward the center.

For this reason, for example, every time a predetermined number of wafers are polished, a dummy wafer is set in a polishing apparatus, and the dummy wafer is polished with a polishing pad. If the sex has declined,
The polishing conditions are being reviewed. If the polishing uniformity cannot be improved by reviewing the polishing conditions, the polishing pad is replaced.

[0007] In the current polishing pad, after a formed pad is subjected to a punching process or a groove process, a double-sided adhesive layer is formed on the back surface of the polishing pad.

However, when a polishing pad is attached to a polishing apparatus for polishing, as the number of polished wafers increases, the polishing slurry enters the lower polishing pad.

The lower polishing pad into which the polishing slurry has entered repeatedly undergoes compression and recovery movements during polishing due to the polishing pressure from the wafer. If gas remains near the center of the lower polishing pad, the polishing slurry can move toward the center of the polishing pad, and the compression and recovery movement of the polishing pad during polishing of the polishing slurry in the polishing pad is reduced. The polishing pad is hardly restrained, and the elastic properties of the polishing pad are hard to change. However, if the polishing slurry penetrates to the vicinity of the center of the lower polishing pad as the number of polished wafers increases, the polishing slurry becomes difficult to move, so that the vertical movement of the polishing pad is restricted, and the elastic characteristics of the polishing pad change. Due to the change in the elastic properties, the uniformity of the polishing amount of the wafer changes. That is, if the conventional polishing pad increases the number of polished wafers, the uniformity of the polishing amount deteriorates. It is necessary to confirm the stability of the non-uniformity of the polishing amount, which is not preferable from the viewpoint of manufacturing efficiency.

[0010]

In recent years, there has been a demand for a technique for maintaining the polishing performance of a polishing pad at a higher level.

SUMMARY OF THE INVENTION An object of the present invention is to provide a polishing pad and a polishing pad which can constantly and stably polish the uniformity of the amount of polishing of a workpiece continuously from the start of use of the polishing pad. It is to provide a method.

[0012]

According to a first aspect of the present invention, there is provided a polishing pad for polishing a workpiece by moving the workpiece relative to the workpiece. A hole is formed from the surface of the pad to connect the lower polishing pad to the polishing pad, and polishing is performed using the polishing pad.

[0013] A second polishing pad structure for achieving the above object is a polishing pad structure for polishing a workpiece by moving relative to the workpiece, wherein the polishing pad has a lower layer from the surface of the polishing pad. The hole connecting the polishing pad has a structure in which only the surface layer of the polishing pad is closed, so that at the start of polishing, liquid such as slurry does not enter through the hole formed near the center of the polishing pad, and As the polishing number increases and the wear of the polishing pad progresses due to the dressing work of the polishing pad, the polishing pad is formed near the center of the polishing pad, the closed portion is consumed, and a hole is formed near the center of the polishing pad. It is to be done.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A polishing pad and a polishing method according to the present invention will be described below with reference to the drawings.

First, the structure of a polishing pad according to a first embodiment will be described with reference to FIG.

In the polishing pad of this embodiment, as shown in FIG. 1, an adhesive layer 4 is formed on the back surface of the upper polishing pad 1. Further, a hole 2 penetrating the upper polishing pad 1 and the adhesive layer 4 is formed. The upper polishing pad 1 is integrated with the lower polishing pad 3 via an adhesive layer 4. The back surface of the lower polishing pad 3 is supported on a rotatable surface plate 8 via an adhesive layer 5. Further, a grinding fluid supply pipe 9 for supplying a slurry 10 onto the upper polishing pad 1 is provided.

Next, a polishing method using the above-described polishing pad will be described with reference to FIG.

Here, the workpiece to be polished is an 8-inch Si having an SiO2 interlayer insulating film formed on the surface.
The wafer 6 is assumed.

In the embodiment of the present invention, the wafer 6 is polished under the following conditions. Opening diameter of polishing pad: diameter 15 mm (formed at center of polishing pad) Number of rotations of rotating table: 100 r / min Number of rotations of wafer chuck: 90 r / min Polishing time: 1 min / sheet Polishing pressure: 30 kpa Polishing liquid: particle size Alkaline solution containing about 12% of 30 nm silica abrasives Supply of polishing liquid: 200 ml / min Dresser rotation speed: 80 r / min Dressing pressure: 10 kpa

As the polishing pad, the polishing pad of the present invention and a conventional polishing pad were used. In the present embodiment, the size of the hole is 15 mm in diameter.
It may be 30 mm. From the start of polishing, dressing of the polishing pad was performed in parallel with polishing of the wafer. The dressing was a so-called in-process dressing performed simultaneously with the polishing of the wafer. For measuring the polishing efficiency of the polished wafer, an optical film thickness measuring device (Nanometrics 5000, manufactured by Nanometrics) was used. The value obtained by subtracting the film thickness after polishing from the thickness of the insulating film before polishing was divided by the polishing time was defined as the polishing efficiency. Further, the polishing amount distribution U was obtained by (Equation 1).

[0021]

(Equation 1)

In equation (1), Vmax is the maximum polishing amount, Vmin is the minimum polishing amount, and Vave is the average polishing amount.

FIG. 2 compares the effect of slurry intrusion on the polishing pad when polishing is performed when the conventional polishing pad is used for polishing and when the polishing pad of the present invention is used for polishing. FIG. As shown in FIG. 2A, when the polishing pad of the present invention was used, when the slurry 10 entered the lower layer pad 5, the slurry 10 freely entered and exited through the hole 2. On the other hand, as shown in FIG. 2B, when the conventional polishing pad is used, when the slurry 10 enters the lower layer pad 5, the slurry 10
Enters and exits only from the outermost periphery of the lower polishing pad 5.

Therefore, in the polishing pad of the present invention, the polishing slurry impregnated in the lower pad can be maintained at a high fluidity.

FIG. 3 shows the deformation characteristics of the polishing pad during polishing. As the wafer passes over the polishing pad, the polishing pad is compressed in the direction of the platen. In addition, when the polishing load is released after passing through the wafer, the deformation of the polishing pad is recovered. As shown in FIG. 3A, when the number of polished wafers was 10, there was no difference in the deformation characteristics of the polishing pad between the case where the polishing pad of the present invention was used and the case where the conventional polishing pad was used. This is because, since the initial stage from the start of polishing, the lower layer polishing pad does not seep into the polishing slurry, and only air is present in the lower layer pad. Next, as shown in FIG. 3B, when the number of polished wafers is 300, when the polishing pad of the present invention is used, the amount of deformation of the polishing pad is 1
The value was almost the same as that of the case of 0 sheets, and the deformation characteristics of the polishing pad did not change.

On the other hand, when the conventional polishing pad is used, the deformation at the time of unloading the polishing load is smaller than the deformation of the polishing pad at the time of pressurization. )
The deformation amount of the polishing pad is displaced by about 5 μm as compared with the case of polishing 10 wafers.

As shown in FIG. 4, when the polishing pad of this embodiment is used, the uniformity of the polishing amount is stable from the start of polishing, and the uniformity of the polishing amount of the wafer is completed when the polishing of 600 wafers is completed. Properties could be stabilized in the range of ± 4 to 5%.

On the other hand, in the conventional polishing pad, the uniformity of the polished amount started to increase from about 200 wafers polished, and it decreased to ± 10% when the number of polished wafers was about 300. When the polishing amount uniformity is controlled at, for example, ± 10%, if it exceeds ± 10%, a problem of over-etching or insufficient etching occurs when forming a contact hole.

In this case, the polishing conditions must be changed in accordance with the change in the characteristics of the polishing pad, and a large amount of dummy wafers and work time are required until the polishing conditions for stably polishing the wafer are set. As described above, in the present embodiment, when the polishing pad 1 is newly used, the deformation characteristics of the polishing pad 1 can be maintained in a stable state from the start of use, and the polishing amount nonuniformity of the wafer can be improved. The increase can be suppressed. In particular, in the present embodiment, as described above, the variation in the polishing amount of the interlayer insulating layer of the wafer is ± 4 to 5%.
Since it can be suppressed to below, for example, the line width is 0.13
The conditions required for an interlayer film of a micrometer ultrafine line can be satisfied.

In the present embodiment, only one hole 2 is provided in the central portion of the polishing pad 1. However, the present invention is not limited to one hole and may be provided by providing a plurality of holes. Similar effects can be obtained.

Next, a second embodiment of the method for manufacturing a polishing pad according to the present invention will be described with reference to FIG.

As shown in FIG. 5, the structure of the upper polishing pad 1 is substantially the same as that of FIG. 1, except that the hole 2b is closed in the vicinity of the surface layer of the upper polishing pad 1 in advance. The polishing pad 1 further includes a dresser 11 that is rotatable about an axis horizontally set on the surface of the upper polishing pad 1 while swinging in the radial direction of the polishing pad 1.

As shown in FIG. 5, the dresser 11 is rotated and pressed against the surface of the upper polishing pad 1 while swinging in the radial direction of the upper polishing pad 1, and the surface of the polishing pad 1 is consumed by dressing. .

In the second embodiment of the present invention, a wafer is polished under the following conditions. Number of rotations of rotary table: 100 r / min Number of rotations of wafer chuck: 90 r / min Polishing time: 1 min / wafer Polishing pressure: 30 kpa Polishing liquid: Alkaline solution containing about 12% silica abrasive grains having a particle diameter of about 30 nm Supply amount: 200 ml / min Dresser rotation speed: 80 r / min Dressing pressure: 10 kpa

As described above, in the present embodiment, when the number of polished wafers increases, the surface of the upper polishing pad 1 is consumed by dressing and the hole 2b is opened, so that it is basically the same as the first embodiment. However, the effect of stabilizing the polishing amount uniformity by the holes 2b can be obtained. For example, when the polishing amount uniformity starts to deteriorate when the number of polished wafers is about 200 as in the prior art in FIG. 4, the depth of the hole is set so that, for example, 150 wafers are polished. Further, each of the above embodiments relates to polishing of the semiconductor wafer 1, but the present invention is not limited to this, and other processes such as a magnetic head wafer and a liquid crystal wafer may be performed. The present invention may be applied to polishing of an object.

[0036]

According to the present invention, since the through holes are formed from the surface of the polishing pad to the underlying polishing pad, the polishing pad is used immediately after the polishing pad is replaced and until the use of the polishing pad is completed. Since the elastic characteristic is stabilized and the polishing amount distribution can be stabilized, the yield of the polished wafer is improved. Further, since it is not necessary to inspect a monitor wafer for inspecting the deterioration state of the polishing amount distribution, inspect a polished wafer, or change polishing conditions for correcting the deterioration of the polishing amount distribution, throughput is improved, and manufacturing cost is improved. Can be reduced.

Further, according to the present invention, the portion which closes only the vicinity of the surface layer of the polishing pad prevents liquid such as slurry from entering through a hole formed near the center of the polishing pad at the start of polishing, thereby preventing the wafer from being polished. The number of polishing increases to a certain extent, the closed portion penetrates when the consumption of the polishing pad progresses by dressing work of the polishing pad,
Uniform polishing on a plurality of wafers appropriately corresponding to the number of polished wafers can be achieved. This has the effect of improving the wafer yield.

[Brief description of the drawings]

FIG. 1 is a view showing a structure of a polishing pad according to a first embodiment of the present invention.

FIG. 2 is a diagram comparing the effect of slurry intrusion into the polishing pad when polishing is performed when a conventional polishing pad is used for polishing and when the polishing pad of the present invention is used for polishing. .

FIG. 3 is a diagram showing the relationship between the number of polished wafers and the dynamic viscoelastic characteristics of the polishing pad for the polishing pad according to the first embodiment of the present invention and the conventional polishing pad.

FIG. 4 is a diagram showing the relationship between the number of polished wafers and the non-uniformity of the polished amount of the wafer between the polishing pad according to the first embodiment of the present invention and the conventional polishing pad.

FIG. 5 is a view showing a structure of a polishing pad in a second embodiment according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Upper polishing pad, 2 ... Hole, 2b ... Hole, 3 ... Lower polishing pad, 4 ... Adhesive layer, 5 ... Adhesive layer, 6 ... Wafer, 7 ... Wafer chuck, 8 ... Polishing surface plate, 9 ... Slurry supply pipe , 1
0: slurry, 11: dresser.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Hideki Sato 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture F-term in Hitachi, Ltd. Production Engineering Research Laboratory F-term (reference) 3C058 AA07 AA09 AA14 AA19 AC04 BA07 CB01 CB03 DA17

Claims (5)

[Claims] 1. A polishing pad for polishing a workpiece by relatively moving the workpiece relative to the workpiece, wherein a hole is formed near the center of the polishing pad from the front surface to the rear surface. pad. 2. A polishing pad for polishing a workpiece by relative movement with respect to the workpiece, wherein a hole is provided in a central portion of the polishing pad, and a predetermined thickness is provided near a surface of the polishing pad. A polishing pad characterized by being left closed. 3. A polishing method for polishing a workpiece by relatively moving the polishing pad with respect to the workpiece, wherein the polishing pad has a hole near the center of the polishing pad formed from the front surface to the back surface. A polishing method characterized in that a workpiece is polished by using a polishing method. 4. A polishing method for polishing a workpiece by moving a polishing pad relative to the workpiece, wherein a hole is provided near a center of the polishing pad, and a surface near the surface of the polishing pad is provided. A polishing method characterized in that a workpiece is polished using a polishing pad that is closed while leaving a predetermined thickness. 5. A method of manufacturing a workpiece, comprising a step of relatively moving the polishing pad according to claim 1 or 2 and the workpiece to polish the workpiece.