Polishing pad

Abstract

The present invention provides a polishing pad including an upper pad on which a groove is formed and a lower pad below the upper pad, in which the polishing pad has a Cp value of 0.10 to 1.3 represented by Equation 1.

Description

Technical Field

[0001] The present invention relates to a polishing pad. Background Art

[0002] Chemical mechanical polishing (CMP) is the core process for flattening and mirror-finishing wafers or glass panels. Polishing is performed through the mechanical and chemical action of a polishing pad and a slurry containing nanoparticles.

[0003] Figure 1 Schematic diagram of a CMP apparatus. The CMP apparatus performs polishing by pressing the polishing object 2 (e.g., a wafer) against the surface of a waste polishing pad 6 fixed to a rotary table 1 (platen) while the carrier 3 securely holds the polishing object 2. Specifically, while the carrier 3 and the rotary table 1 rotate independently, a liquid slurry (abrasive) is applied from a nozzle 5 to the polishing pad 6, thereby performing chemical polishing and mechanical polishing. Furthermore, as the dresser 4 is pressed against the polishing pad at a position separated from the polishing object 2 during the polishing process, the surface of the polishing pad is roughened, and thus the surface state of the polishing pad remains rough.

[0004] Polishing pads are one of the main consumables used in the chemical mechanical polishing process. They are made of soft polymer materials to improve the surface mirror processing performance and contain many grooves and pores on their surface to effectively discharge the polishing by-products generated during the polishing process and supply slurry.

[0005] Because polishing pads are constantly exposed to mechanical friction between the high-hardness nanoabrasive particles and the material being polished, the micropores on the surface become clogged and the surface irregularities responsible for polishing are worn away, resulting in a decrease in polishing performance over time. Therefore, a pad resurfacing process that periodically polishes the surface is used to prevent degradation of polishing performance.

[0006] Since there is no realistic recycling program for polishing pads that have been used for a period of time, polishing pads are treated as industrial waste. However, due to the increasing consumption of polishing pads and the environmental pollution caused by the disposal of polishing pads, further research on recycling methods such as recycling is needed.

[0007] As conventional techniques for recycling waste polishing pads, there are known methods of compensating for worn portions of waste polishing pads using compensation materials, methods of recycling waste polishing pads by disassembling and reassembling components constituting the waste polishing pads, such as an upper pad and a lower pad, and the like.

[0008] However, these methods are not economically viable in terms of recycling efficiency for spent polishing pads. Furthermore, in this recycling process, the existing polishing surface is ground and flattened, and new grooves are formed on the flattened surface. Because the pressure and friction applied during the grinding process can damage the pore shape of the flattened surface, there is a problem in ensuring sufficient roughness on the polishing surface of the recycled polishing pad.

[0009] [Prior art literature]

[0010] [Patent Document]

[0011] Korean Patent Publication No. 10-2020-0139907 Summary of the Invention

[0012] Technical issues

[0013] The present invention is designed to solve the above-mentioned problems of the prior art.

[0014] An object of the present invention is to provide a polishing pad having polishing performance comparable to that of a new polishing pad and having excellent flatness even if a waste polishing pad is recovered and used.

[0015] Another object of the present invention is to provide a recycled polishing pad having excellent polishing performance produced by a recycling method.

[0016] Technical Solution

[0017] In order to achieve the above object, the present invention provides a polishing pad comprising:

[0018] an upper pad having a groove formed thereon and a lower pad located below the upper pad,

[0019] Here, the polishing pad has a Cp value of 0.10 to 1.3 represented by the following equation 1.

[0020] [Equation 1]

[0021] Cp = compression ratio × thickness change rate / 100

[0022] Beneficial effects

[0023] According to the present invention, since the spent polishing pad is recycled through a simple process, the polishing pad provides very excellent recycling efficiency and polishing performance comparable to that of a new polishing pad.

[0024] Furthermore, according to the present invention, since the polishing pad has excellent polishing performance, the polishing pad can be used in a CMP process without performance degradation due to recycling. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1is a perspective view showing the structure of a typical CMP apparatus.

[0026] Figure 2 is a cross-sectional view illustrating a method of manufacturing a polishing pad according to one embodiment of the present invention.

[0027] Figure 3 is a flow chart of a method of making a polishing pad according to one embodiment of the present invention.

[0028] Figure 4 is a schematic diagram of a polishing pad according to one embodiment of the present invention.

[0029] Figure 5 is a graph illustrating a method for calculating the compressibility of a polishing pad according to one embodiment of the present invention. DETAILED DESCRIPTION

[0030] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention. However, the present invention can be implemented in various forms and is not limited to the embodiments described in this specification. Throughout this specification, similar components will be represented by the same reference numerals.

[0031] When a component is referred to as being “connected to, coupled to, or mounted in” another component, it should be understood that it can be directly connected to or mounted in the other component, but other components may exist between them. On the other hand, when a component is referred to as being “directly connected to, disposed in, or mounted in” another component, it should be understood that no other components exist between them. Meanwhile, other expressions describing the relationship between components, such as “on top of,” “directly above,” “between,” “directly between,” “adjacent to,” “directly adjacent to,” etc., should also be interpreted similarly.

[0032] Figure 2 is a cross-sectional view illustrating a method of manufacturing a polishing pad according to one embodiment of the present invention, Figure 3 1 is a flow chart of a method for recovering a polishing pad according to one embodiment of the present invention. Figure 2 and Figure 3 A method of making a polishing pad according to the present invention is described.

[0033] like Figure 2 As shown in FIG, the method for manufacturing a polishing pad according to the present invention comprises the following steps:

[0034] a) separating the adhesive layer 14 on the lower surface of the lower pad 13 from the waste polishing pad 100;

[0035] b) grinding the polishing surface on which the groove 15 of the waste polishing pad 100 is formed, and then flattening the polishing surface;

[0036] c) forming grooves 17 on the polishing surface of the flat waste polishing pad;

[0037] d) An adhesive layer 14 is formed on the lower surface of the lower pad 13 of the spent polishing pad.

[0038] As conventional techniques for recycling waste polishing pads, there are known methods of compensating for worn portions of the polishing pad using a compensating material, methods of recycling the polishing pad by disassembling and reassembling components constituting the polishing pad such as an upper pad and a lower pad, and the like.

[0039] However, these methods are difficult to use in practice due to low recovery efficiency and subsequent low economic feasibility.

[0040] The present invention restores the pore shape damaged during the grinding process through a grinding treatment, thereby providing excellent roughness to the polishing surface, thereby having a feature of providing polishing performance comparable to that of a new polishing pad.

[0041] In one embodiment of the present invention, the smoothing step of step b) can be performed by grinding down 0.3 mm to 1.3 mm, preferably 0.3 mm to 1.0 mm, more preferably 0.3 mm to 0.8 mm from the bottom of the groove.

[0042] In one embodiment of the present invention, the thickness of the flat polishing pad in step b) may be 2 mm or more, preferably 2.0 mm to 3.0 mm, more preferably 2.5 mm to 2.9 mm.

[0043] In the polishing pad manufactured in this manner, the thickness of the upper pad can be 0.6 mm to 1.7 mm, preferably 0.9 mm to 1.7 mm, more preferably 1.2 mm to 1.6 mm, most preferably 1.4 mm to 1.6 mm.

[0044] Furthermore, in the polishing pad, the thickness of the lower pad may be 0.7 mm to 1.4 mm, preferably 0.8 mm to 1.3 mm.

[0045] In one embodiment of the present invention, the method for recycling a spent polishing pad may not include a separate dressing process. In the prior art, a dressing process is performed to restore damaged roughness. However, the dressing process does not restore damaged pores, but rather creates roughness by scraping the pores of the polishing surface. Therefore, the polishing surface roughness may not be formed at all, and the effect may not last long.

[0046] The present invention solves this problem by a method of grinding damaged parts, thereby providing sufficient roughness for the polishing surface and also maintaining the effect for a long time.

[0047] In one embodiment of the present invention, a process of cleaning the waste polishing pad may be further performed between step a) and step b). In this case, the cleaning method is not particularly limited and may be performed by methods known in the art.

[0048] In one embodiment of the present invention, the upper pad of the spent polishing pad may be made of a porous polyurethane material, but is not limited to this material.

[0049] In one embodiment of the present invention, the groove 17 may have a depth of about 0.8 mm to about 1.0 mm, but the depth of the groove is not limited thereto. The groove may have a uniform depth or may have different depths. The process of forming the groove may be carried out by methods known in the art.

[0050] The present invention provides a recycled polishing pad recycled by the above method.

[0051] The recycled polishing pad of the present invention restores physical properties by grinding the polishing surface to a specific thickness, thereby providing excellent roughness to the polishing surface for a long period of time.

[0052] In the following, reference will be made to Figure 4 The polishing pad produced in the present invention is exemplarily described.

[0053] The present invention provides a polishing pad including an upper pad having grooves formed thereon and a lower pad located below the upper pad, wherein the polishing pad has a Cp value of 0.10 to 1.3 represented by the following Equation 1.

[0054] [Equation 1]

[0055] Cp = compression ratio × thickness change rate / 100

[0056] The polishing pad includes an upper pad 11 having grooves formed thereon. The upper pad 11 includes a polishing surface having a plurality of first grooves 17. The grooves 15 support a large slurry flow on the surface of the polishing pad. The grooves 17 have a depth of about 0.8 mm to about 1.0 mm.

[0057] The upper pad 11 may be made of a porous polyurethane material and may have holes supporting trickles, but is not limited thereto.

[0058] In some embodiments, the polishing pad may include a first adhesive layer 12 , a subpad 13 , and a second adhesive layer 14 .

[0059] The lower pad 13, located below the upper pad, can be made of a material that has a resilient force against the force applied to the base, and uniformly supports the upper pad 11 by buffering this force. The lower pad 13 can be, for example, a polyurethane foam pad, an impregnated felt pad, a microporous polyurethane pad, a sintered polyurethane pad, or a polyolefin foam pad, but is not limited thereto. Typically, the lower pad 13 has a lower hardness than the upper pad 11. Furthermore, the lower pad 13 can have a greater compressibility than the upper pad 11.

[0060] The first adhesive layer 12 may be located between the upper pad 11 and the lower pad 13 to attach the lower pad 13 to the upper pad 11. The second adhesive layer 14 may be provided between the lower pad 13 and the platen to fix the polishing pad 100 to the rotating table (platen) of the polishing apparatus. Figure 1 ). The first adhesive layer 12 and the second adhesive layer 14 may include a pressure-sensitive adhesive (PSA) or a hot melt adhesive (HMA). For example, the pressure-sensitive adhesive may be an adhesive containing a polyacrylic acid component, an epoxy component, or a rubber component, or a double-sided pressure-sensitive tape in which the adhesive material is applied to both sides of a substrate (e.g., a PET film or felt), but is not limited thereto. For example, the hot melt adhesive may be a cured reactive hot melt adhesive, but is not limited thereto.

[0061] The polishing pad has a Cp value of 0.10 to 1.3 expressed by Equation 1 below.

[0062] [Equation 1]

[0063] Cp = compression ratio × thickness change rate / 100

[0064] The inventors of the present invention found that when grinding the upper layer of the upper pad to reuse the waste polishing pad, the thickness of the upper pad and the lower pad of the polishing pad each has a specific range, so that the compression rate of the entire polishing pad and the thickness change rate of the entire polishing pad can have different values, and after quantifying these values, the polishing performance and flatness of the recycled polishing pad can have good values ​​based on the result value of multiplying these values.

[0065] As a result, the polishing pad of the present invention is characterized in that the recycled polishing pad has good polishing performance when the Cp value represented by the following Equation 1 is 0.10 to 1.3.

[0066] When the compression rate is expressed as %, the Cp value uses only the numerals excluding % as a value. In addition, a percentage value obtained by dividing the thickness change rate expressed in % by 100 is used.

[0067] For example, in the case of a polishing pad having a compression rate of 1.4% and a thickness variation rate of 26.5%, the Cp value is 0.37, which is 1.4 times 0.265.

[0068] In the present invention, the Cp value may be 0.10 or more, 0.13 or more, 0.20 or more, 0.35 or more, 0.65 or more, 0.85 or more, 1.0 or more, and 1.20 or more, and may be 1.3 or less, 1.0 or less, 0.80 or less, 0.60 or less, 0.45 or less, and 0.20 or less.

[0069] When the Cp value is less than 0.10, the improvement of the pad performance due to recovery as a recovery pad is not significant, and when the Cp value is greater than 1.3, there is a problem of poor polishing performance.

[0070] In one embodiment of the present invention, the polishing pad may have a thickness of 2 mm or more, preferably 2.0 mm to 3.0 mm, and more preferably 2.5 mm to 2.9 mm.

[0071] In one embodiment of the present invention, the thickness of the upper pad may be 0.6 mm to 1.7 mm, preferably 0.9 mm to 1.7 mm, more preferably 1.2 mm to 1.6 mm, most preferably 1.4 mm to 1.6 mm.

[0072] In one embodiment of the present invention, the thickness of the underlying pad may be 0.7 mm to 1.4 mm, preferably 0.8 mm to 1.3 mm.

[0073] In one embodiment of the present invention, the thickness change rate in the above Equation 1 is a ratio of the current thickness to the thickness of the initially manufactured polishing pad and can be determined by the following Equation 2.

[0074] [Formula 2]

[0075] Thickness change rate (%) = (initial pad thickness - pad thickness during analysis) × 100 / initial pad thickness

[0076] In one embodiment of the present invention, the polishing pad may have a polishing performance of 2,000 A / min to 2,650 A / min.

[0077] In one embodiment of the present invention, the underpad may have a compressibility of 1% to 8%.

[0078] In the present invention, the compression ratio can be measured by the following equation 3, and the following equation 3 can be measured by Figure 5 To calculate specifically.

[0079] [Equation 3]

[0080] Compression ratio (%) = (L3-L4) × 100 / L3

[0081] (L3 is the initial thickness of the second cycle when the compression rate is measured in the viscoelastic device, and L4 is the thickness during the second 30-second loading process.)

[0082] Specifically, refer to Figure 5 , when a prepared specimen (5×5 cm) of 1500 g was repeatedly measured twice in a viscoelastic apparatus with a loading time of 30 s and an unloading time of 30 s, respectively, L3 and L4 were set to the initial thickness of the second cycle and the thickness during the second 30-second loading process, respectively.

[0083] The compression rate may be 1% or more, 2% or more, 4% or more, or 6% or more, and may be 8% or less, 6% or less, or 4% or less. When the compression rate is less than 1%, during the CMP polishing process, there is a problem of uneven polishing due to low polishing uniformity across the entire surface of the wafer. When the compression rate exceeds 8%, even if the pad is recycled, the pad life during actual use is too short, making it difficult to apply the pad to the polishing process.

[0084] In addition, when the compression rate is too low, polishing unevenness occurs, so the pad may be designed to ensure polishing uniformity by attaching a pad having compression characteristics to the lower part of a high-hardness top pad.

[0085] In one embodiment of the present invention, the polishing pad may be a recycled polishing pad used by recycling a waste polishing pad.

[0086] Hereinafter, the present invention will be described in detail with reference to Examples. However, embodiments according to the present invention may be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described in detail below. Examples of the present invention are provided to more fully explain the present invention to those skilled in the art.

[0087] Example 1: Recycling of polishing pads

[0088] [Examples 1-1 to 1-6 and Comparative Example 1-1]

[0089] The same type of polishing pad was obtained and discarded after use, and the thickness of the upper pad was measured. The thickness of the upper pad was 1.9 mm, the thickness of the lower pad was 1.4 mm, and the initial thickness of the pad before use was 3.3 mm. The compression rate of the lower pad was 6%.

[0090] For this purpose, the recovery process is carried out as follows.

[0091] First, the adhesive layer bonded to the underlying pad was separated from the spent polishing pad and removed. Next, the spent polishing pad was washed and dried. Next, the polishing surface of the dried spent polishing pad was ground to varying thicknesses using a lathe for each of the Examples and Comparative Examples, and then the polishing surface was flattened.

[0092] Next, the spent polishing pad is recycled by forming grooves on its polishing surface using a groove processing machine (CNC). Then, one side of double-sided tape is attached to the lower surface of the recycled polishing pad, followed by a 1.4 mm thick underpad, completing the recycled pad. The same underpad used initially was used as the underpad.

[0093] The results are shown in Table 1 below.

[0094] [Examples 2-1 to 2-5 and Comparative Example 2-1]

[0095] The recycling process was performed using a pad discarded after use as in Example 1, except that the thickness of the upper pad was 1.9 mm, the thickness of the lower pad was 0.8 mm, the initial thickness of the pad before use was 2.7 mm, and the compression rate of the lower pad was 2.5%, and was ground at different thicknesses for each of the Examples and Comparative Examples.

[0096] Then, one side of a double-sided tape was attached to the lower surface of the recovered polishing pad, and then a 0.8 mm thick underpad was attached to complete the recovered pad. As the underpad, the same underpad as that used initially was used.

[0097] The results are shown in Table 2 below.

[0098] [Example 3-1 to Example 3-3 and Comparative Example 3-1]

[0099] The recycling process was performed using a pad discarded after use as in Example 1, except that the thickness of the upper pad was 1.9 mm, the thickness of the lower pad was 1.4 mm, the initial thickness of the pad before use was 3.5 mm, and the compression rate of the lower pad was 15.0%, and was ground at different thicknesses for each of the Examples and Comparative Examples.

[0100] Then, one side of a double-sided tape was attached to the lower surface of the recovered polishing pad, and then a 1.4 mm thick underpad was attached to complete the recovered pad. As the underpad, the same underpad as that used initially was used.

[0101] The results are shown in Table 3 below.

[0102] [Example 4-1 to Example 4-4 and Comparative Example 4-1]

[0103] The recycling process was performed using a pad discarded after use as in Example 1, except that the thickness of the upper pad was 1.55 mm, the thickness of the lower pad was 1.4 mm, the initial thickness of the pad before use was 3.0 mm, and the compression rate of the lower pad was 10.0%, and was ground at different thicknesses for each of the Examples and Comparative Examples.

[0104] Then, one side of the double-sided tape is attached to the lower surface of the recycled polishing pad, and then a lower pad with a thickness of 1.4 mm is attached to complete the recycled pad. As the lower pad, the same lower pad as the one initially used is used.

[0105] The results are shown in Table 4 below.

[0106] Experimental Example 1: Evaluation of Compression Ratio and Polishing Performance of Recycled Polishing Pad

[0107] The results of the compression ratio, thickness change rate, Cp value, and polishing performance of the manufactured recycled pads are summarized as follows.

[0108] Specifically, each recycled polishing pad is attached to Figure 1 the CMP apparatus shown, and the polishing performance of the wafer is evaluated. The results are shown in Tables 1 to 5 below.

[0109] <CMP Process Conditions>

[0110] Polishing table rotation speed (rpm): 120

[0111] Carrier rotation speed (rpm): 120

[0112] Wafer pressure (psi): 3.0

[0113] Slurry flow rate (fumed silica), 240 ml / min

[0114] Polishing time (seconds): 60

[0115] <Method for Measuring Compression Ratio>

[0116] In the present invention, the compression ratio refers to a value indicating the degree of possible volume change of an object when a force is applied to the object. The compression ratio in the present invention is calculated as follows.

[0117] 1) Preparation

[0118] Pad specimen size (width × length): 5 cm × 5 cm

[0119] Viscoelasticity measuring instrument (VMS, GNP Corporation)

[0120] Keep the temperature and humidity constant (25 °C, 50% RH)

[0121] 2) Measurement <000026A><000026B>- Condition: Measurement cycle: 2 <000026C><000026D>Loading time: 30 <000026E>

[0124] Unloading time: 30

[0125] - Calculation: First, the compression ratio is calculated using L3 and L4 as shown in the graph.

[0126] Here, L3 is the initial thickness of the second cycle when the compressibility is measured in the viscoelastic device, and L4 is the thickness during the second 30-second loading.

[0127] Specifically, refer to Figure 5 , when a prepared specimen (5x5 cm) of 1500 g was repeatedly measured twice in a viscoelastic apparatus with a loading time of 30 seconds and an unloading time of 30 seconds, respectively, L3 and L4 were set to the initial thickness of the second cycle and the thickness during the second 30-second loading period, respectively.

[0128] This value refers to the second cycle compression amount. Then, the compression ratio is calculated as shown in the following equation 3.

[0129] [Equation 3]

[0130] Compression ratio (%) = (L3-L4) × 100 / L3

[0131] [Table 1]

[0132]

[0133] *Cp=Compression ratio×Thickness change ratio / 100

[0134] **Pad life: The usable time when the pad usability range is predicted based on Cp

[0135] [Table 2]

[0136]

[0137] [Table 3]

[0138]

[0139] [Table 4]

[0140]

[0141] From the experimental results in Tables 1 to 4 above, it can be confirmed that when each polishing pad sample is ground and recovered to a specific thickness satisfying a Cp value within a specific range of 0.10 to 1.3, polishing performance above a specific level can be ensured.

[0142] However, in the case of Comparative Example 1-1 to Comparative Example 4-1, it was confirmed that the polishing performance was not ensured and it was not easy to use as a recovery pad.

[0143] Furthermore, in the case of Example 1 listed in Table 1, the time taken from the start of use of Example 1-1 as an actual recycling pad to the final level of use of Example 1-6 as a pad is defined as the pad life. Thus, the actual use time of the recycling pad is predicted. For specific calculations, when calculated based on a pad wear rate of 35 m / hr, it can be predicted that approximately 25.7 hours of use will be possible by calculating 0.9*1000 / 35.

[0144] Similarly, in the case of Example 2 shown in Table 2, using the calculation results of the pad life using the pad of Example 2-1 through the pad of Example 2-5, it is predicted that approximately 22.9 hours of use will be possible through the calculation of 0.8*1000 / 35.

[0145] Similarly, in the case of Example 3 shown in Table 3, using the calculation results of the pad life using the pad of Example 3-1 up to the pad of Example 3-3, it is predicted that approximately 8.6 hours of use will be possible through the calculation of 0.3*1000 / 35.

[0146] Similarly, in the case of Example 4 shown in Table 4, using the calculation results of the pad life using the pad of Example 4-1 up to the pad of Example 4-4, it is predicted that approximately 14.3 hours of use will be possible through the calculation of 0.5*1000 / 35.

[0147] In the case of a recycling pad, a usage time of at least 20 hours should be ensured. As in Example 1 or Example 2, when the compression rate of the lower pad falls within the range of 1% to 8%, a sufficient usage time of more than 20 hours is ensured. On the other hand, in the case of Example 3 or Example 4, where the compression rate of the lower pad exceeds 8%, it is confirmed that the usage time of the recycling pad is short, which significantly reduces the effectiveness of the recycling pad.

[0148] [Explanation of Reference Signs]

[0149] 11: Upper pad 12: First adhesive layer

[0150] 13: bottom pad 14: second adhesive layer

[0151] 15, 17: Groove 100: Waste polishing pad

[0152] 200: Recycled polishing pads

Claims

1. A polishing pad comprising: an upper pad having a groove formed thereon and a lower pad located below the upper pad, wherein the polishing pad has a Cp value of 0.10 to 1.3 represented by the following equation 1, [Equation 1] Cp = compression ratio × thickness change rate / 100.

2. The polishing pad according to claim 1, wherein The polishing pad has a thickness of 2.0 mm to 3.0 mm.

3. The polishing pad according to claim 2, wherein The thickness of the upper pad is 0.6 mm to 1.7 mm.

4. The polishing pad according to claim 2, wherein The thickness of the bottom pad is 0.7 mm to 1.4 mm.

5. The polishing pad according to claim 1, wherein The upper pad is made of porous polyurethane material. The polishing pad according to claim 1 , wherein: The underpad is any one or more of a polyurethane foam underpad, an impregnated felt underpad, a microporous polyurethane underpad, a sintered polyurethane underpad or a polyolefin foam underpad.

7. The polishing pad according to claim 1, wherein The lower pad has a compressibility of 1% to 8%.

8. The polishing pad according to claim 1, wherein The thickness change rate in Equation 1 is the ratio of the current thickness to the thickness of the initially manufactured polishing pad.

9. The polishing pad according to claim 1, wherein The polishing pad has a polishing performance of 2,000 A / min to 2,650 A / min.

10. The polishing pad according to claim 1, wherein The polishing pad is a recycled polishing pad used by recycling a waste polishing pad.

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