CN111390752A

CN111390752A - Polishing pad

Info

Publication number: CN111390752A
Application number: CN201910018649.9A
Authority: CN
Inventors: 徐士杰; 许进旺
Original assignee: Powerchip Technology Corp
Current assignee: Powerchip Technology Corp
Priority date: 2019-01-02
Filing date: 2019-01-09
Publication date: 2020-07-10
Also published as: TWI679083B; TW202026101A

Abstract

The invention discloses a grinding pad, which is provided with a circular grinding surface, a plurality of semicircular first grooves which are positioned in the grinding surface and distributed outwards at a certain interval from the center of the grinding surface in the form of concentric circles, the first grooves positioned in the grinding surface of one semicircle and the first grooves positioned in the grinding surface of the other semicircle are arranged in staggered concentric circles, and a plurality of circular second grooves which are spirally distributed at a certain interval angle, and the second grooves are respectively intersected with the first grooves.

Description

Polishing pad

Technical Field

The present invention relates to polishing pads, and more particularly, to a polishing pad with a specific groove pattern design that increases polishing rate and reduces the number of defects generated during polishing.

Background

In a semiconductor manufacturing process, a Chemical Mechanical Polishing (CMP) manufacturing process is mainly used to completely planarize a layer structure formed in an existing manufacturing process, so that a subsequent manufacturing process is easier to perform. Generally, the CMP process is performed by providing a polishing slurry with a mixture of chemicals on a polishing pad, applying a pressure to the object to be polished to press the object onto the polishing pad, and moving the object and the polishing pad relative to each other. The surface of the object is removed by the mechanical friction generated by the relative movement and the chemical action of the grinding fluid, so that the surface of the object is gradually flattened, thereby achieving the purpose of flattening. The CMP process is essentially an anisotropic process, which is mainly achieved by mechanical action in the CMP process, so that the polishing uniformity can be determined according to different characteristics of the polishing pad.

In the CMP process, a polishing slurry is used to polish the wafer, wherein the polishing slurry contains SiO abrasive particles₂,Al₂O₃Or CeO₂The grinding particles of the material can achieve the grinding effect. Because of their small particle size, such abrasives tend to coagulate to form large particles that can cause scratch defects during CMP. In addition, the pores of the polishing pad are easily clogged by the polishing slurry and the polishing by-products after many uses, so a good polishing pad must have good retention of the polishing slurry to achieve high-efficiency polishing, and also discharge the polishing by-products smoothly for good polishing reproducibility.

Disclosure of Invention

In view of the above-mentioned shortcomings of conventional polishing pads and the desired improvements, the present invention provides a novel polishing pad with a special groove pattern design to quickly fill the entire polishing pad with slurry and discharge byproducts, thereby increasing the polishing rate and reducing the generation of scratches.

The invention provides a polishing pad, which has a circular polishing surface, a plurality of semicircular first grooves located in the polishing surface and distributed outwards at a certain interval from the center of the polishing surface in the form of concentric circles, the first grooves located in one semicircle and the first grooves located in the other semicircle are arranged in staggered concentric circles, and a plurality of circular second grooves are spirally distributed at a certain interval angle, and each second groove is intersected with the first grooves.

These and other objects of the present invention will become more readily apparent to those skilled in the art after reading the following detailed description of the preferred embodiments, which are illustrated in the various figures and drawings.

Drawings

The accompanying drawings are included to provide a further understanding of embodiments of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate some embodiments of the invention and together with the description serve to explain its principles. In these figures:

FIG. 1 is a schematic view of a polishing system according to one embodiment of the present invention;

FIG. 2 is a schematic cross-sectional view of a polishing pad according to an embodiment of the invention; and

FIG. 3 is a plan view of a polishing pad in accordance with a preferred embodiment of the present invention.

It should be noted that all the figures in this specification are schematic in nature, and that for the sake of clarity and convenience, various features may be shown exaggerated or reduced in size or in proportion, where generally the same reference signs are used to indicate corresponding or similar features in modified or different embodiments.

Description of the symbols

100 grinding system

102 polishing pad

104 wafer

106 grinding disc

108 wafer carrier

110 abrasive surface

112 abrasive surface

114 grinding media

116 inlet

118 grooves

120 grinding layer

122 backing layer

124 first trench

124a portion

124b part

126 second trench

126a first set of second trenches

126b second set of second trenches

Points a, b, c, d

d1 distance

α pitch angle

D diameter

F acting force

R1 rotating shaft

R2 rotating shaft

Detailed Description

FIG. 1 is a schematic diagram of a polishing system 100 suitable for use with a polishing pad 102 to polish articles, such as a wafer 104, in accordance with one embodiment of the present invention. The polishing system 100 may include a polishing pad 106 on which the polishing pad 102 is mounted. The abrasive disk 106 is rotatable about a rotation axis R1. The polishing system 100 also includes a wafer carrier 108 that rotates about a rotational axis R2 and holds the entire wafer 104 during polishing. The wafer 104 has a polishing surface 110 that faces the polishing surface 112 of the polishing pad 102 during polishing and is planarized. The wafer carrier 108 rotates the wafer 104 and provides a downward force F to press the polishing surface 110 of the wafer 104 against the polishing pad 102, such that the polishing surface 110 and the polishing pad 102 have a desired pressure therebetween. A polishing medium 114, such as a slurry, may be supplied to the polishing surface 112 of the polishing pad 102 through an inlet 116. During polishing, the polishing pad 102 and the wafer 104 rotate about their respective rotational axes R1, R2, and the polishing medium 114 drips onto the rotating polishing surface 112 and is distributed evenly across the entire surface, including the gap between the wafer 104 and the polishing pad 102, by centrifugal force.

Next, fig. 2 is a schematic cross-sectional view of a polishing pad according to an embodiment of the invention. As shown in FIG. 2, the polishing pad 102 includes a plurality of grooves 118 formed in a polishing layer 120 having a polishing surface 112, thus defining a groove pattern. Each of the grooves 118 may actually have a predetermined cross-sectional shape and size suitable for a particular polishing design, and thus, the rectangular cross-sectional shape of the grooves 118 shown in fig. 2 is merely exemplary. The polishing layer 120 is supported by a backing layer 122, which may be formed with the polishing layer 120 or separately. The material of the polishing layer 120 may include, but is not limited to, a polymer plastic such as polyurethane (polyurethane), polybutadiene (polybutadienee), polycarbonate (polycarbonate), polymethacrylate (polymethylacrylate), and the like.

Referring now to FIG. 3, therein is shown a plan view of the polishing pad 102 in accordance with a preferred embodiment of the present invention. FIG. 3 illustrates the groove patterns defined on the polishing pad 102 of the present invention, and the following embodiments illustrate the detailed features and functional effects of the groove patterns. The trench pattern of the present invention is mainly composed of a plurality of first trenches 124 and a plurality of second trenches 126. As shown in fig. 3, the first grooves 124 are semi-circular arcs in the form of concentric circles distributed outwardly from the center of the abrasive surface 112 at a distance d1 (e.g., 5.2 millimeters (mm)) to the circumference of the abrasive surface 112. The first grooves 124 are divided into a portion 124a located in the left semicircle of the polishing surface 112 and a portion 124b located in the right semicircle of the polishing surface 112, and the first grooves 124a of the left semicircle and the first grooves 124b of the right semicircle are alternately arranged in concentric circles and are discontinuous. More specifically, the first groove pattern of the semicircular arc of the concentric circle is arranged such that the end points a of the left semicircular portion 124a and the end points b of the right semicircular portion 124b are staggered along the diameter D of the polishing surface 112 at the intersection of the left and right semicircles. In the present invention, the discontinuous design of the plurality of semi-circular staggered grooves can effectively increase the efficiency of the polishing liquid flowing to the surface of the polishing pad, and the polishing rate is improved.

In other embodiments, the end points of the left semicircular first groove 124a and the right semicircular first groove 124b may not be located at the diameter D. As shown by the dashed circle in fig. 3, the left semicircular first trench 124a may also partially overlap with the right semicircular first trench 124b in a staggered manner, depending on the actual requirements and the design of the invention.

In addition to the grooved design of the first trench 124, the depth of the first trench 124 also varies in its design. In the embodiment of the present invention, the depth of each first trench 124 gradually becomes deeper from two end points (e.g., end points a or b) to the middle of the trench, and the depth may be between 0 and 2 millimeters (mm). The deeper groove design helps to retain the slurry in the middle of the groove, which significantly improves slurry retention on the polishing pad compared to the conventional groove without depth variation.

Referring again to FIG. 3, in addition to the first grooves 124, the groove pattern of the present invention further includes second grooves 126. in the embodiment of the present invention, as shown in FIG. 3, the second grooves 126 are circular and are spaced apart from each other by a pitch angle α that is spirally distributed about the center of the polishing surface 112. more specifically, as used herein, the term "pitch angle" is defined as the distance between two concentric points, i.e., the point c and the point d on adjacent second grooves 126, and the pitch angle α is the angle between two lines drawn by the two points as a straight line with the center of the circle.

Moreover, it can be seen that the second grooves 126 are further divided into a first group of second grooves 126a and a second group of second grooves 126b, which are respectively distributed in the inner and outer circles of the polishing surface 112, wherein the pitch angle of the first group of second grooves 126a in the inner circle is smaller than the pitch angle of the second group of second grooves 126b in the outer circle. In the embodiment of the present invention, the inner circle is located 15 to 100 millimeters (mm) from the center of the polishing surface 112, and the outer circle is located 100 to 300 mm from the center of the polishing surface. The pitch angle of the first group of second grooves 126a is set to 30 degrees, and the pitch angle of the second group of second grooves 126b is set to 45 degrees. Thus, the number of the first set of second trenches 126a is greater than the number of the second set of second trenches 126 b. It should be noted that the setting of the outer and inner race diameters and the pitch angles described herein are for illustrative purposes only and are not intended to be limiting.

In the present invention, the second grooves 126 having a circular arc-shaped spiral distribution will help promote the movement of slurry and byproducts on the polishing surface 112 during polishing. More specifically, the first set of grooves 126a on the inner circumference of the polishing pad allows the slurry to be supplied to the center of the polishing pad to quickly and uniformly spread over the entire polishing surface 112 as the polishing pad rotates, while the second set of grooves 126b on the outer circumference of the polishing pad has a smaller number but a larger distance therebetween so that the by-products generated during polishing can be discharged out of the polishing pad as the polishing pad rotates without hindrance.

In addition to the above features, in the preferred embodiment of the present invention, the width of the semicircular arc-shaped first groove 124 is significantly smaller than the width of the circular arc-shaped second groove 126, for example, the width of the first groove 124 is set to 0.5 millimeter (mm), and the width of the second groove 126 is 2 mm. The reason for this is that the first grooves 124 have a larger number of grooves and a smaller width because the main function of the grooves is to retain the polishing slurry to provide the polishing effect. The second grooves 126 have a smaller number of grooves but a wider width because they can rapidly and uniformly transmit the slurry and rapidly and smoothly remove the polishing by-products, as described above. It should be noted that the setting of the first trench width and the second trench width described herein is only for illustrative purposes and is not limited thereto.

The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in the claims of the present invention should be covered by the present invention.

Claims

1. A polishing pad, comprising:

a polishing layer for polishing a substrate in the presence of a polishing medium, the polishing layer having a circular polishing surface;

a plurality of first grooves in the polishing surface, wherein the first grooves are semi-circular arc-shaped, are distributed outwards from the center of the polishing surface to the circumference of the polishing surface at a certain interval in the form of concentric circles, and are arranged in a staggered concentric circle with the first grooves in the other semicircle; and

and a plurality of second grooves in the polishing surface, wherein the second grooves are arc-shaped and spirally distributed at certain intervals, and each second groove is intersected with the first grooves.

2. The polishing pad of claim 1, wherein the second grooves are further divided into a first group of second grooves and a second group of second grooves distributed in the polishing surface at inner and outer circles, respectively, and the pitch angle of the first group of second grooves is smaller than the pitch angle of the second group of second grooves.

3. The polishing pad of claim 2, wherein the polishing surface of the inner circle is located 15-100 mm (mm) away from the center of the polishing surface, and the polishing surface of the outer circle is located 100-300 mm (mm) away from the center of the polishing surface.

4. The polishing pad of claim 2, wherein the pitch angle of the first set of second grooves is 30 degrees and the pitch angle of the second set of second grooves is 45 degrees.

5. The polishing pad of claim 1, wherein the depth of each first groove gradually increases from the two ends of the first groove to the middle of the first groove.

6. The polishing pad of claim 5, wherein the first grooves have a depth of 0 to 2 millimeters (mm).

7. The polishing pad of claim 1, wherein the first grooves in the semi-circle partially overlap the first grooves in the other semi-circle.

8. The polishing pad of claim 1, wherein the first grooves have a width of 0.5 millimeters (mm) and the second grooves have a width of 2 mm.

9. The polishing pad of claim 1, wherein the pitch of the first grooves is 5.2 millimeters (mm).