JP2000349053A - Polishing pad with groove - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make faster the polishing speed on the surface of a wafer by a chemical mechanical polishing method by a method wherein at least a polishing face part is formed of a foamed plastic, the polishing face part is provided with a groove and the surface roughness of the polishing face part is specified. SOLUTION: In this polishing pad which is used, at least a polishing face part is formed of a foamed plastic, and a polishing face 11 is provided with grooves 12. A dressing operation is performed to the polishing face 11 of the polishing pad in such a way that the surface roghness of the polishing face 11 is at 0.5 to 15 μm in terms of surface roughness prescribed in JIS-B0601. Then, by using the polishing pad, a material to be polished is polished. In the grooves 12, a depth D (as the height of every protrusion 13 existing between the adjacent grooves), a width W, a groove pitch(p) and the width S of every protrusion 13 are set. It is preferable that the depth D of every groove is set at 0.1 mm or higher so as to be a range of 4/5 or lower of the thickness of the pad, that the width W of every groove is set at 0.1 to 5.0 mm and that the groove pitch(p) is set to be 1.0 to 50 mm. It is more preferable that the depth D of every groove is set at 0.1 to 1.0 mm, that the groove width W of every groove is set to be 0.15 to 0.3 mm and that the groove pitch(p) is set to be 1.5 to 10 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a polishing pad used for flattening irregularities on a wafer surface by a chemical mechanical polishing method.

[0002]

2. Description of the Related Art When a semiconductor device is manufactured, a conductive film is formed on a wafer surface and patterned by a photolithography / etching technique to form a wiring layer.
Steps of forming an interlayer insulating film on the wiring layer are performed, and these steps cause irregularities made of a conductor or an insulator such as a metal on the wafer surface. In recent years, miniaturization of wiring and multi-layer wiring have been promoted for the purpose of increasing the density of semiconductor integrated circuits. With this, technology for flattening unevenness on the surface of a wafer has become important.

[0003] As a method of flattening the irregularities on the wafer surface, a conventional method of chemical mechanical polishing (Chemical Mec.
hanical Polishing (CMP) is employed. C
The MP method is a technique in which a surface to be polished such as a wafer surface is pressed against a polishing surface of a polishing pad and polished using a slurry-type abrasive in which abrasive grains are dispersed. The polishing apparatus used in the CMP method is, for example, as shown in FIG.
A polishing table 2, which supports the workpiece 3, a support table 4 which supports the workpiece 3, and an abrasive supply mechanism 5. Polishing pad 1
Is attached to the polishing platen 2 by, for example, attaching with a double-sided tape T. The polishing platen 2 and the support table 4 are arranged so that the polishing pad 1 and the workpiece 3 respectively supported are opposed to each other, and are provided with rotating shafts 21 and 41, respectively. A pressure mechanism for pressing the workpiece 3 against the polishing pad 1 is provided on the support base 4 side.

[0004] A polishing pad is mounted on a polishing platen of such a polishing apparatus, and "dressing" is performed to scrape the polishing surface of the polishing pad with a diamond dresser or the like. Done. In a conventional flattening process for unevenness on a wafer surface, a polishing pad made of foamed polyurethane is used.

In the CMP method, it has been proposed to provide a groove on a polishing surface of a polishing pad for the purpose of increasing a polishing rate or the like. For example, JP-A-5-1469
No. 69 describes that a large number of concentric circular grooves are formed.

[0006]

However, there is still room for improvement in the polishing rate in the above prior art. An object of the present invention is to increase the polishing rate of a wafer surface by the CMP method.

[0007]

In order to solve the above-mentioned problems, the present invention provides a polishing pad for chemical mechanical polishing in which at least a polishing surface portion is formed of foamed plastic and has a groove on the polishing surface. Roughness is JIS
-0.5 μm or more 1 with surface roughness specified in B0601
Provided is a polishing pad characterized by having a thickness of 5 μm or less.

[0008] According to this polishing pad, since the surface roughness of the polishing surface is within the above-mentioned predetermined range, the slurry-like abrasive can be easily held uniformly on the pad surface. As a result, when the polishing pad of the present invention is used, the polishing rate can be increased as compared with the case where a conventional grooved polishing pad is used. The preferred range of the surface roughness of the polished surface is JIS-B0601
Is 0.5 μm or more and 7 μm or less in the surface roughness specified in the above.

The foamed plastic forming at least the polishing surface portion of the polishing pad has an average diameter of bubbles of 1 μm or more and 150 μm or less and a porosity of 50% or more and 1 cm ^3.
It is preferable that the number of bubbles per unit is 10 ⁶ or more. Since the foam of this structure has a very thin cell wall, the presence of the foam on the polishing surface makes it easy to keep the surface roughness of the polishing surface within the above range. A more preferable range of the average diameter (average cell diameter) of the cells of the foamed plastic is 1 μm or more and 100 μm or less, a more preferable range of the porosity is 60% or more, and an even more preferable range is 6%.
5% or more, a particularly preferred range is 70% or more. Further, the closed cell rate (volume ratio of closed cells in all cells including open cells) of the foamed plastic is preferably 50% or more (more preferably 70% or more).

[0010] The present invention also provides a polishing apparatus characterized in that the polishing pad of the present invention is mounted. The present invention also provides a method of manufacturing a semiconductor device, characterized in that a step of flattening irregularities on a wafer surface by a chemical mechanical polishing method is performed using the polishing pad of the present invention.

[0011] The present invention also provides a chemical mechanical polishing method using a polishing pad having at least a polishing surface portion formed of a foamed plastic and having a groove on the polishing surface. JIS-
0.5 μm or more with a surface roughness specified in B0601
The present invention provides a chemical mechanical polishing method characterized in that dressing is performed so as to have a thickness of not more than μm, and then a polishing target is polished using the polishing pad.

The shape of the grooves on the polishing surface of the polishing pad of the present invention may be a large number of concentric shapes, lattice shapes, radial shapes, spiral shapes, and the like. FIG. 1 is a cross-sectional view showing a polishing surface side portion of a polishing pad 1 having a groove 12 in a polishing surface 11. As shown in this figure, the dimensions indicating the shape of the groove 12 include a depth (height of the convex portion 13 existing between adjacent grooves) D, a width W, and a groove pitch (a distance between adjacent grooves). ) P and the width (span) S of the projection 13.

The depth D of the groove is preferably in the range of 0.1 mm or more and 4/5 or less of the pad thickness. Groove width W
Is preferably 0.1 mm or more and 5.0 mm or less. The distance (groove pitch) p between adjacent grooves is 1.0 m
It is preferable that it is not less than m and not more than 50 mm. More preferable groove depth D is 0.1 mm or more and 1.0 mm or less, more preferable groove width W is 0.15 mm or more and 0.3 mm or less, and more preferable groove pitch p is 1.5 mm or more and 10 m.
m or less.

In the polishing pad of the present invention, it is preferable that the ratio (S / D) of the span (width of the projection 13) S to the groove depth (height of the projection 13) D is 1 or more and 100 or less. This reduces the shear strain during polishing, thereby improving the polishing uniformity. (S / D) is 1 or more and 10 or more.
It is more preferable to select the groove depth, groove width, and groove pitch within the above ranges so as to be 0 or less.

As a method of forming the groove, a cutting method or a stamping method may be used, but it is preferable to employ a cutting method in order to sharpen the shape of the groove. Examples of the cutting method include processing with a lathe or a milling machine. In order to form the roundness at the corner between the opening end of the groove and the polishing surface (the corner at the tip of the convex portion), it is preferable to employ an embossing method.

At least the polishing surface portion (the portion on the polishing surface side in the thickness direction of the polishing pad of the present invention, for example, the portion from the polishing surface 11 to the position to be the bottom surface of the groove 12 shown by reference numeral 10 in FIG. ) Is formed of foamed plastic. The portion formed of foamed plastic may be only the polishing surface portion of the polishing pad, or the entire polishing pad may be formed of foamed plastic.

The foamed plastic usable for the polishing pad of the present invention includes olefin resins, fluorine resins,
Polycarbonate resin, acrylic resin, nylon resin,
Foams using one or a mixture of two or more selected from styrene resins and the like as a base material are exemplified. As the olefin-based resin, for example, high-density polyethylene, low-density polyethylene, and polyethylene such as linear low-density polyethylene, ethylene-propylene copolymer, polypropylene,
Poly-4-methyl-pentene and ionomer resins.

Examples of the fluorine-based resin include polyvinyl fluoride, polyvinylidene fluoride, and vinylidene fluoride.
Tetrafluoroethylene copolymer, vinylidene fluoride
Hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-
Hexafluoropropylene copolymer, tetrafluoroethylene-perfluoromethyl-perfluorovinyl ether copolymer, tetrafluoroethylene-perfluoroethyl-perfluorovinyl ether copolymer, tetrafluoroethylene-perfluoropropyl-perfluorovinyl ether copolymer Coalescence and the like.

In the polishing pad of the present invention, it is preferable to use a fluorine resin as the foamed plastic.

[0020]

Embodiments of the present invention will be described below. Foamed sheet made of fluororesin, whose base material is polyvinylidene fluoride (foamed sheet A)
And a material whose base material is a polyvinylidene fluoride-hexafluoropropylene copolymer (foamed sheet B) was produced by the following method.

First, a polyvinylidene fluoride resin (melting point 168 ° C., MFR 2.9 (230
12.5 kg) was formed into a 1.1 mm thick sheet. Next, the sheet was irradiated with an electron beam of 15 Mrad using an electron beam irradiation machine of 500 KV to perform cross-linking to obtain a cross-linked polyvinylidene fluoride sheet.

Next, the sheet is placed in a pressure vessel, and 1,1,1,2-tetrafluoroethane is introduced as a foaming agent into the pressure vessel and maintained at 70 ° C. for 30 hours. The blowing agent was absorbed. Next, put this sheet in a heating furnace equipped with a far-infrared heater,
The temperature was kept at 200 ° C. for 90 seconds. As a result, a foamed sheet of crosslinked polyvinylidene fluoride (foamed sheet A) was obtained.

The foamed sheet B is made of a vinylidene fluoride-hexafluoropropylene copolymer resin (melting point 156 ° C., MFR 5.1 (230 ° C., 12.5 kg)) as a raw material resin.
Was prepared in the same manner as in the case of the foamed sheet A except for the above. However, the heating holding time after absorbing the foaming agent was set to 70 seconds. When the expansion ratio and average cell diameter of each of the foam sheets A and B were measured by the following method, the expansion ratio of foam sheet A was 4 times and the average cell diameter was 125.
μm, and the foaming ratio of the foamed sheet B is 3.8 times,
The average bubble diameter was 8 μm.

Regarding the expansion ratio, the density M1 (g / g) of the crosslinked polyvinylidene fluoride sheet before impregnation with the blowing agent was used.
cm ³ ) and the density M2 (g / cm
³ ) was measured, and the ratio of the two (M2 / M1) was calculated as the expansion ratio. ASTM-D357 for average cell diameter
6 was measured. First, an arbitrary portion of the obtained foamed sheet is cut, and a micrograph of the cut surface is taken. Next, draw a 1cm straight line (grid line) on this photo,
The number N of bubbles existing on the grid line is counted, and the average bubble diameter (μm) is calculated using the following equation (2).

Average bubble diameter = (grid line length (μm)
/N)/0.616 Using the foamed sheets A and B thus obtained, a polishing pad was prepared and a polishing test was performed as follows. (Example 1) After buffing both surfaces of the foamed sheet A with a # 240 belt sander, the foamed sheet A was cut into a shape (circle having a diameter of 610 mm) in accordance with a polishing platen of a polishing apparatus to be mounted. A double-sided tape was applied to the back surface (the surface opposite to the polished surface) of the cut foam sheet. A large number of concentric grooves (groove width 0.2 mm, groove depth (D) 0.5 mm, groove pitch 1.5 mm, span (S)) are formed on the surface (surface to be polished) of this foam sheet by cutting. 1.3 mm, S / D =
2.6) was formed. The formation range of the groove was set to a radius of 12.5 mm or more to the outer periphery of the circular polished surface. Thus, a polishing pad having a groove formed on the surface (polishing surface) of the foamed sheet was obtained.

This polishing pad is mounted on a polishing platen of a polishing apparatus (“434-STZ” manufactured by Nanotech Machines Co., Ltd.) (attached using a double-sided tape on the back surface), and #
Dressing was performed for 3 minutes using a 240 electrodeposited diamond ring. The surface roughness Ra of the dressed polished surface (the maximum height of the irregularities specified in JIS B0601) was measured using a profiler “HRP-100” manufactured by KLA-Tencor, and was 4.1 μm.
m.

FIG. 2 is a cross-sectional view showing a state after dressing of the polishing surface portion 10 of the polishing pad.
This corresponds to an enlarged view of the portion. As shown in this figure, a large number of bubbles 15 are present on the polishing surface 10 of this polishing pad,
Bubbles 1 existing near polishing surface 11 due to dressing
5a is destroyed, and fluff 11a is generated on the polishing surface 11. Most of the bubbles 15 existing on the polishing surface 10 were closed cells.

Next, a wafer having a diameter of 6 inches was mounted on a support of the polishing apparatus, and polished using a slurry-type abrasive ("ILD-1200" manufactured by Rodel). A silicon oxide film formed by a CVD method using TEOS (tetraethylorthosilicate) as a source gas was provided on the outermost surface of the wafer, and the surface of the silicon oxide film was polished. The polishing conditions were such that the rotation speed of the polishing platen was 58
rpm, the rotation speed of the support table was 62 rpm, and the load applied between the polishing surface of the polishing pad and the surface to be polished of the wafer by the pressing mechanism of the support table was 500 g / cm ² .

The polishing rate and uniformity of this polishing were measured using “NANOSPECAFT” manufactured by Nanometrics.
It was measured by the following measurement method. That is, the thickness of the silicon oxide film is measured at nine locations in the wafer surface before and after polishing, and the amount of decrease in the thickness at each location is calculated. The polishing rate is calculated as a value obtained by dividing the average value of the film thickness reduction amounts by the polishing time. The polishing uniformity is determined by the maximum value G of these film thickness reduction amounts.
It is calculated by the following equation using _max , minimum value _Gmin, and average value _Gave .

Uniformity (%) = ((G _max −G _min ) / 2)
G _ave ) × 100 As a result, the polishing rate was 3290 ° / min, and the polishing uniformity was 12.9%. (Embodiment 2) The same polishing pad as in Embodiment 1 was used.
For 3 minutes using a diamond electrodeposition ring. The surface roughness R of this dressed polished surface
a (the maximum height of the irregularities specified in JIS B 0601) was measured by the same method as in Example 1, and it was found that 9.2 was obtained.
μm.

Next, the same wafer as in Example 1 was mounted on the support table, and the silicon oxide film surface of this wafer was polished in the same manner as in Example 1. However, in this polishing, the polishing pad at the start of the polishing of the wafer (after dressing) was used in Example 1.
And different. When the polishing rate of this polishing was measured by the same method as in Example 1, it was 1950 ° / min. (Example 3) A polishing pad having a groove formed on the surface of the foamed sheet was obtained in the same manner as in Example 1 except that the foamed sheet B was used instead of the foamed sheet A.

This polishing pad was mounted on a polishing platen of the same polishing apparatus as in Example 1, and dressed for 3 minutes using a # 240 diamond electrodeposition ring. The surface roughness Ra of the dressed polished surface (JIS B 060)
1) was measured by the same method as in Example 1 and found to be 1.8 μm. Next, the same wafer as in Example 1 was attached to the support table, and the silicon oxide film surface of this wafer was polished by the same method as in Example 1. However, in this polishing, a polishing pad at the start of polishing of a wafer (after dressing) is different from that in the first embodiment.

The polishing rate and uniformity of the polishing were determined in Example 1.
The polishing rate was 4130 ° /
Min, and the polishing uniformity was 8.3%. (Embodiment 4) The same polishing pad as that of Embodiment 3 was used.
For 3 minutes using a diamond electrodeposition ring. The surface roughness R of this dressed polished surface
a (maximum height of unevenness specified in JIS B 0601) was measured by the same method as in Example 1, and found to be 6.7.
μm.

Next, the same wafer as in Example 1 was mounted on the support table, and the silicon oxide film surface of this wafer was polished in the same manner as in Example 1. However, in this polishing, the polishing pad at the start of the polishing of the wafer (after dressing) was used in Example 1.
And different. When the polishing rate of this polishing was measured by the same method as in Example 1, it was 2310 ° / min. (Example 5) As in Example 1, after buffing both sides of the foamed sheet A, cutting it into a predetermined shape, and attaching a double-sided tape to the back side, the front side (the polished side) of this foamed sheet was used. Surface), a number of concentric grooves (groove width 0.2 mm, groove depth (D) 0.5 mm, groove pitch 3.
0 mm, span (S) 2.8 mm, S / D = 5.6). The groove formation range was the same as in Example 1. Thus, a polishing pad having a groove formed on the surface (polishing surface) of the foamed sheet was obtained.

This polishing pad was mounted on a polishing platen of the same polishing apparatus as in Example 1, and was dressed for 3 minutes using a # 240 diamond electrodeposition ring to obtain a polished surface having a surface roughness Ra (JIS B 0601) was set to 4.1 μm, which is the same as in Example 1. Next, the same wafer as in Example 1 was attached to the support table, and the silicon oxide film surface of this wafer was polished by the same method as in Example 1. However, in this polishing, the polishing pad at the start of the polishing of the wafer (after dressing) was used in Example 1.
And different.

The polishing rate and uniformity of this polishing were determined in Example 1.
The polishing rate was 3170 ° /
And the polishing uniformity was 7.7%. (Example 6) As in Example 1, after buffing both sides of the foamed sheet A, cutting out the sheet into a predetermined shape, and attaching a double-sided tape to the back side, the surface of the foamed sheet A (the polished surface). Surface), a large number of concentric grooves (groove width 0.2 mm, groove depth (D) 0.5 mm, groove pitch 4.
5 mm, span (S) 4.3 mm, S / D = 8.6). The groove formation range was the same as in Example 1. Thus, a polishing pad having a groove formed on the surface (polishing surface) of the foamed sheet was obtained.

This polishing pad was mounted on a polishing platen of the same polishing apparatus as in Example 1, and was dressed for 3 minutes using a # 240 diamond electrodeposition ring to obtain a polished surface having a surface roughness Ra (JIS B 0601) was set to 4.1 μm, which is the same as in Example 1. Next, the same wafer as in Example 1 was attached to the support table, and the silicon oxide film surface of this wafer was polished by the same method as in Example 1. However, in this polishing, the polishing pad at the start of the polishing of the wafer (after dressing) was used in Example 1.
And different.

The polishing rate and uniformity of this polishing were determined in Example 1.
The polishing rate was 2970 ° /
Min, and the polishing uniformity was 4.0%. (Example 7) As in Example 1, after buffing both sides of the foamed sheet A, cutting out the foamed sheet into a predetermined shape, and attaching a double-sided tape to the back side, the surface of the foamed sheet A (hereinafter referred to as a polished surface). Surface), a lattice-like groove (groove width 0.2 mm, groove depth (D) 0.5 mm, groove pitch 4.5) by cutting.
mm, span (S) 19.52 mm, S / D = 48.
8) was formed. Thus, a polishing pad having a groove formed on the surface (polishing surface) of the foamed sheet was obtained.

This polishing pad was mounted on the polishing platen of the same polishing apparatus as in Example 1, and was dressed for 3 minutes using a # 240 diamond electrodeposition ring to obtain a polished surface having a surface roughness Ra (JIS B 0601) was set to 4.1 μm, which is the same as in Example 1. Next, the same wafer as in Example 1 was attached to the support table, and the silicon oxide film surface of this wafer was polished by the same method as in Example 1. However, in this polishing, the polishing pad at the start of the polishing of the wafer (after dressing) was used in Example 1.
And different.

The polishing rate and uniformity of this polishing were determined in Example 1.
The polishing rate was 2040 ° /
Min and the polishing uniformity was 12.5%. (Comparative Example 1) As in Example 1, both sides of the foamed sheet A were buffed, cut into a predetermined shape, and a double-sided tape was attached to the back surface. A polishing pad was used as it was without forming grooves on the surface of the foam sheet.

This polishing pad was mounted on the polishing platen of the same polishing apparatus as in Example 1, and was dressed for 3 minutes using a # 240 diamond electrodeposition ring to obtain a polished surface having a surface roughness Ra (JIS B 0601) was set to 4.1 μm, which is the same as in Example 1. Next, the same wafer as in Example 1 was attached to the support table, and the silicon oxide film surface of this wafer was polished by the same method as in Example 1. However, in this polishing, the polishing pad at the start of the polishing of the wafer (after dressing) was used in Example 1.
And different.

When the polishing rate of this polishing was measured by the same method as in Example 1, it was 1030 ° / min. Comparative Example 2 As in Example 1, both sides of the foam sheet A were buffed, cut into a predetermined shape, and a double-sided tape was attached to the back surface. However, the buffing was performed using a # 80 belt sander. Then, the same groove is formed in the same range as in Example 1 on the surface (surface to be a polishing surface) of the foamed sheet, so that a polishing pad having a groove formed on the surface (polishing surface) of the foamed sheet I got

This polishing pad was mounted on a polishing platen of the same polishing apparatus as in Example 1, and polished as it was without dressing. Next, the same wafer as in Example 1 was attached to the support, and the silicon oxide film surface of this wafer was polished in the same manner as in Example 1. However, in this polishing, a polishing pad at the start of polishing of a wafer (after dressing) is different from that in the first embodiment.

When the polishing rate of this polishing was measured in the same manner as in Example 1, it was 800 ° / min. The test results are summarized in Table 1 below.

[0045]

[Table 1]

As can be seen from this table, in Examples 1 to 7 in which polishing was performed using the polishing pad of the present invention, polishing was performed using a polishing pad whose surface roughness was out of the range of the present invention. The polishing rate can be made higher than in Comparative Examples 1 and 2 in which the polishing was performed.

[0047]

As described above, according to the polishing pad, the polishing apparatus, and the chemical mechanical polishing method of the present invention, the polishing speed of the wafer surface by the CMP method can be further increased. Further, according to the method of manufacturing a semiconductor device of the present invention, it is possible to reduce the time required for the step of flattening irregularities on the surface of a wafer by a chemical mechanical polishing method.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a polishing surface side portion of a polishing pad having a groove on a polishing surface.

FIG. 2 is a sectional view showing a state after dressing of a polishing surface portion of a polishing pad obtained in an example, and corresponds to an enlarged view of a portion A in FIG. 1;

FIG. 3 is a schematic configuration diagram illustrating an example of a polishing apparatus used in a CMP method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polishing pad 2 Polishing surface plate 3 Material to be polished (wafer) 4 Support base 5 Polishing agent supply mechanism 10 Polishing surface part 11 Polishing surface 11a Fluff 12 Groove 13 Groove between grooves 15 Bubbles D Groove depth W Groove width p Groove pitch S span

Claims (4)

[Claims] 1. A polishing pad for chemical mechanical polishing, wherein at least a polishing surface portion is formed of foamed plastic and has a groove on the polishing surface, wherein the polishing surface has a surface roughness of a surface roughness specified by JIS-B0601. A polishing pad having a size of 5 μm or more and 15 μm or less. 2. A polishing apparatus comprising the polishing pad according to claim 1. 3. A method for manufacturing a semiconductor device, wherein a step of flattening irregularities on a surface of a wafer by a chemical mechanical polishing method is performed by using the polishing pad according to claim 1. 4. A chemical mechanical polishing method using a polishing pad having at least a polishing surface portion formed of foamed plastic and having a groove on the polishing surface, wherein the polishing surface of the polishing pad has a surface roughness of JIS-
0.5 μm or more with a surface roughness specified in B0601
A chemical mechanical polishing method characterized in that dressing is performed so as to be not more than μm, and then a polishing target material is polished using the polishing pad.