TWI840151B - How to use chemical mechanical polishing pads - Google Patents

Abstract

A method for using a chemical mechanical polishing pad includes the following steps: capturing at least one image of each of a plurality of chemical mechanical polishing pads. Calculating a porosity of each of the chemical mechanical polishing pads using the images. Selecting one of the chemical mechanical polishing pads. Determining a polishing liquid having a specific abrasive particle size range or a dresser having a specific abrasive particle size range based on the porosity value of the selected chemical mechanical polishing pad.

Description

How to use chemical mechanical polishing pads

The present invention relates to a method for chemical mechanical polishing pad, and more particularly to a method for using the chemical mechanical polishing pad.

Polishing and grinding processes are commonly used in the semiconductor industry. In order to achieve better flatness and higher precision on the wafer surface, the Chemical-Mechanical Planarization (CMP) process, also known as Chemical-Mechanical Polishing, is mostly used. It removes irregular structures on the wafer surface after deposition or etching steps to achieve the purpose of flattening. Common polishing pads are made of foamed cured polyurethane. The porous structure of the polishing pad is mainly used to retain the polishing liquid and exert the polishing effect, but it will also be filled with debris during the polishing process, resulting in passivation and a decrease in roughness, which reduces the material removal rate. In other words, the holes in the polishing pad play an important role in the CMP process, especially the shape, distribution and size of the holes, which will affect the suitable polishing liquid and the suitable dresser. I490083 discloses a CMP polishing pad, comprising (a) a polishing layer having a polishing surface and a back surface opposite to the polishing surface; the polishing layer having at least one cured opaque thermosetting polyurethane block and at least one porous block; the at least one cured opaque thermosetting block having a porosity of from about 10% to about 55% by volume; the at least one porous block having (1) a top opening positioned below the polishing surface, (2) a bottom opening coplanar with the back surface, and (3) a plurality of straight vertical sidewalls extending from the top of the pore to the bottom of the pore. The invention relates to a method for preparing a polishing layer having a bottom opening extending from the bottom opening of the pore; the at least one pore block is filled with a cured plug of a thermosetting polyurethane local area transparent material having a light transmittance of less than 80% at a wavelength of 700 to 710 nanometers and directly chemically bonded to a thermosetting polyurethane opaque area; (b) a non-porous removable release sheet covering at least a portion of the back side of the polishing layer; and (c) an adhesive layer interposed between the polishing layer and the release sheet; the adhesive layer is capable of adhering the polishing layer to a polishing platform of a CMP device after the release sheet is removed.

On the other hand, the following patent documents have been proposed for the determination of the porosity of porous structure materials. For example, Taiwan Invention Patent Publication No. TW 202101791 provides a piezoelectric film that can achieve high durability and an electroacoustic conversion film that can obtain sufficient sound pressure relative to an input operating voltage. The aforementioned piezoelectric film comprises a polymer composite piezoelectric containing piezoelectric particles in a matrix comprising a polymer material and electrode layers arranged on both sides of the polymer composite piezoelectric. The polymer composite piezoelectric is divided into two parts in the thickness direction by observing the cross section in the thickness direction with a scanning electron microscope. When the porosity is measured in the two regions respectively, the porosity ratio obtained by dividing the porosity of the region with high porosity by the porosity of the region with low porosity is greater than 1.2, thereby solving the problem.

The prior art can also be found in Chinese invention patent publication No. CN 114972227 A, which discloses a method for measuring the porosity of a grinding wheel, which is completed according to the following steps: 1) surface treatment of a grinding wheel sample: Since the components of the grinding wheel sample belong to different conductive materials, the surface of the grinding wheel sample is firstly treated with an ion plating agent for gold spraying, and the treated grinding wheel sample is placed on the stage of a scanning electron microscope; 2) the surface of the grinding wheel sample is photographed; 3) the porosity of the grinding wheel surface is analyzed; 4) the porosity of the grinding wheel surface is verified. Compared with the prior art, the beneficial effects of the present invention are: the present invention has the characteristics of low cost, simple structure and easy use, and at the same time, by combining optical processing and software, the cumbersome steps during detection are simplified and the detection efficiency is improved.

Nevertheless, the prior art does not match the polishing pad with different polishing fluids or dressers according to the characteristics of the polishing pad, and thus cannot bring into play the optimized performance of material removal or dressing the polishing pad.

The main purpose of the present invention is to solve the problem in the prior art that the polishing pad is not matched with different polishing liquids or dressers according to the characteristics of the polishing pad.

To solve the above problems, the present invention provides a method for using a chemical mechanical polishing pad, comprising the following steps: capturing at least one image of each of a plurality of chemical mechanical polishing pads; calculating a porosity of each of the chemical mechanical polishing pads using the images; selecting one of the chemical mechanical polishing pads; and, according to the value of the porosity of the selected chemical mechanical polishing pad, determining a polishing liquid having a specific abrasive particle size range, or a dresser having a specific abrasive particle size range.

The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention. Unless the context indicates otherwise, the singular forms "a", "an" and "the" used herein may also include plural forms.

This article adopts a flow chart to illustrate the steps performed according to the embodiment. It should be understood that each step does not necessarily have to be performed exactly in the order described in this article. On the contrary, these steps can be performed in reverse order or simultaneously. At the same time, other steps can also be added to the process, or one or more steps can be removed from these processes.

According to an embodiment of the present invention, the surface images of a plurality of chemical mechanical polishing pads are captured, and the captured images of the chemical mechanical polishing pads are analyzed to obtain the porosity of each chemical mechanical polishing pad. The chemical mechanical polishing pads are graded according to the porosity values, and different polishing liquids are provided for polishing, or different trimmers are provided for trimming. The following is an example of a polyurethane foamed chemical mechanical polishing pad, but in other examples, it can also be applied to chemical mechanical polishing pads with other porous structures.

This case can be applied to multiple chemical mechanical polishing pads with unknown porosity, and can also be applied to multiple chemical mechanical polishing pads with known specifications. In the former, the difference in porosity is relatively large, and the method of the present invention can be used to measure the porosity of each chemical mechanical polishing pad, and then the polishing or grinding process can be optimized according to the porosity. In the latter, although there are known specifications, the specifications of chemical mechanical polishing pads on the market mostly express porosity in ranges, and even if they are chemical mechanical polishing pads of the same specification, there will still be differences in porosity based on changes in the process, and this difference will still affect the polishing or grinding process. By using the method of the present invention, the porosity of chemical mechanical polishing pads of the same specification can be further measured, and the polishing or grinding process can be optimized according to the porosity.

Referring to FIG. 1 , which is a schematic diagram of an embodiment of the present invention, the method of the present invention is to capture an image 30a of a polished surface 21 of a chemical mechanical polishing pad 20 by an image capture device 10. In one embodiment, the image capture device 10 is a scanning electron microscope (SEM). The image 30a may be a partial area or the entire area of the polished surface 21, and the image 30a may refer to an original image that has not been post-processed. In one example, the image capture device 10 may be a scanning electron microscope, or may be a high-magnification optical zoom camera, an optical microscope equipped with a digital camera, or a digital microscope device. After capturing the image 30a of the polishing surface 21 of the CMP pad 20, the image capturing device 10 transmits the image 30a to an image processing device 40. In one example, the image processing device 40 may be a computer.

In one example, the image processing device 40 sets the grayscale of pixels in the image 30a that are greater than a specific critical grayscale value as a grayscale maximum value, and sets the grayscale of pixels that are less than the specific critical grayscale value as a grayscale minimum value, thereby realizing binarization processing of the image 30a, thereby converting the image 30a into a post-image 30b with a flake feature. Then, the porosity of the post-image 30b can be calculated by using Image J image processing software.

The user can select an appropriate polishing liquid 50 from a variety of different polishing liquids to polish a wafer 60 according to the porosity of the chemical mechanical polishing pad 20; or, after use, select an appropriate dresser 70 from a variety of different dressers to dress the chemical mechanical polishing pad 20.

In one example, assuming that a plurality of chemical mechanical polishing pads with unknown porosity are used, after obtaining the porosity (hereinafter expressed as volume percentage) of the chemical mechanical polishing pad 20, the chemical mechanical polishing pad 20 is graded according to the porosity value. assuming that a plurality of chemical mechanical polishing pads with known specifications are used, according to the specification, the porosity is between 25% and 35%, after obtaining the porosity of the chemical mechanical polishing pad 20, the chemical mechanical polishing pad 20 is graded according to the porosity value.

For the chemical mechanical polishing pad with high porosity, since the retention rate of the polishing liquid is high, it is suitable for use in the process with a high polishing degree requirement. Therefore, the hole will be more blocked after use, so it is suitable to use a dresser with a smaller abrasive particle size range. Conversely, for the chemical mechanical polishing pad with low porosity, since the retention rate of the polishing liquid is low, it is suitable for use in the process with a low polishing degree requirement. Therefore, the hole will be less blocked after use, so it is suitable to use a dresser with a larger abrasive particle size range. Therefore, the particle size range of the abrasive particles of the polishing liquid 50 becomes smaller as the porosity of the chemical mechanical polishing pad 20 becomes higher; and the particle size range of the abrasive particles of the polishing liquid 50 becomes larger as the porosity of the chemical mechanical polishing pad 20 becomes lower.

Refer to FIG2 , which is a schematic diagram of the process steps of the first embodiment of the present invention. The present invention discloses a method for using a chemical mechanical polishing pad, and the description of each step is as follows.

Step S101: Capturing images of polishing pads. A user captures at least one image (ie, the original image) of each of a plurality of chemical mechanical polishing pads using an image capturing device.

Step S102: Calculate the porosity of the polishing pad. The user converts the original images of the chemical mechanical polishing pads through an image processing device and calculates the porosity of each of the chemical mechanical polishing pads.

Step S103: Select a polishing pad. The user selects one of the chemical mechanical polishing pads.

Step S104: Determine the polishing liquid to be used according to the porosity value of the polishing pad. The user determines a polishing liquid with a specific abrasive particle size range according to the porosity value calculated for the selected chemical mechanical polishing pad. In one example, the porosity of the polishing pad has a volume percentage of 22% to 49%, and the abrasive particle size range of the polishing liquid is between 5nm and 300nm; the porosity of the polishing pad has a volume percentage of 0% to 22%, and the abrasive particle size range of the polishing liquid is between 0.2um and 50um.

Step S105: Polishing the wafer using a polishing pad and a polishing liquid. The user performs chemical mechanical polishing on a wafer according to the selected chemical mechanical polishing pad and the polishing liquid that matches the chemical mechanical polishing pad.

Refer to FIG3 , which is a schematic diagram of the process steps of the second embodiment of the present invention. The present invention discloses a method for using a chemical mechanical polishing pad, and the description of each step is as follows.

Step S201: Capturing images of polishing pads. The user captures at least one image (ie, the original image) of each of a plurality of chemical mechanical polishing pads using an image capturing device.

Step S202: Calculate the porosity of the polishing pad. The user converts the original images of the chemical mechanical polishing pads through an image processing device and calculates the porosity of each of the chemical mechanical polishing pads.

Step S203: Determine the selected dresser according to the porosity value of the polishing pad. The user determines a dresser with a specific abrasive particle size range according to the porosity value calculated for the selected chemical mechanical polishing pad. In one example, the porosity of the polishing pad has a volume percentage of 22% to 49%, and the abrasive particle size range of the dresser is between 30um and 400um; the porosity of the polishing pad has a volume percentage of 0% to 22%, and the abrasive particle size range of the dresser is between 200um and 1800um.

Step S204: trimming the polishing pad using a trimmer. The user trims the chemical mechanical polishing pad using the trimmer that matches the chemical mechanical polishing pad.

In summary, the present invention can detect the porosity of the polishing pad through the aforementioned method to obtain the matching standard of the porosity with the particle size of the abrasive particles of the polishing liquid, and the matching standard of the porosity with the roughness of the dresser, and objectively select a dresser with appropriate cutting force to dress the polishing pad, and select an appropriate polishing liquid so that the removal rate and surface profile of the polishing can be maintained stable.

10: Image capture device 20: Chemical mechanical polishing pad 21: Polishing surface 30a: Image 30b: Post-image 40: Image processing device 50: Polishing liquid 60: Wafer 70: Dresser S101, S102, S103, S104, S105, S201, S202, S203, S204: Steps

『Figure 1』 is a schematic diagram of an embodiment of the present invention. 『Figure 2』 is a schematic diagram of the process steps of the first embodiment of the present invention. 『Figure 3』 is a schematic diagram of the process steps of the second embodiment of the present invention.

10: Image capture device

20: Chemical mechanical polishing pad

21: Polished surface

30a: Image

30b: Post-production of images

40: Image processing device

50: Grinding fluid

60: Wafer

70: Dresser

Claims (10)

A method for using a chemical mechanical polishing pad comprises the following steps: Capturing at least one image of each of a plurality of chemical mechanical polishing pads; Using the images to calculate a porosity of each of the chemical mechanical polishing pads; Selecting one of the chemical mechanical polishing pads; and Determining a polishing liquid having a specific abrasive particle size range or a dresser having a specific abrasive particle size range based on the porosity value of the selected chemical mechanical polishing pad. A method as described in claim 1, wherein the particle size range of the abrasive particles in the polishing liquid is inversely proportional to the porosity of the chemical mechanical polishing pad. A method as described in claim 2, wherein when the volume percentage of the porosity of the polishing pad is between 22% and 49%, the particle size range of the abrasive particles of the polishing liquid is between 5nm and 300nm. A method as described in claim 2, wherein, when the volume percentage of the porosity of the polishing pad is between 0% and 22%, the particle size range of the abrasive particles of the polishing liquid is between 0.2um and 50um. A method as described in claim 1, wherein the abrasive particle size range of the dresser is inversely proportional to the porosity of the chemical mechanical polishing pad. A method as described in claim 5, wherein the volume percentage of the porosity of the polishing pad is between 22% and 49%, and the particle size range of the abrasive particles of the matching dresser is between 30um and 400um. A method as described in claim 5, wherein the volume percentage of the porosity of the polishing pad is between 0% and 22%, and the particle size range of the abrasive particles of the matching dresser is between 200um and 1800um. A method as described in claim 1, wherein the chemical mechanical polishing pads are classified into at least one high porosity and one low porosity according to their respective porosities. The method of claim 1, wherein the image is a scanning electron microscope photograph. A method as described in claim 1, wherein the chemical mechanical polishing pad is a polyurethane foamed chemical mechanical polishing pad.

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