A polyurethane polishing pad and a method of making the same

Abstract

The application belongs to the technical field of chemical mechanical polishing of semiconductors, and provides a polyurethane polishing pad and a preparation method thereof.The polyurethane polishing pad comprises at least a polishing layer and a buffer layer, and the polishing layer comprises the following raw materials in parts by weight: polyurethane prepolymer 60-100 parts, filler 1-10 parts, and curing agent 10-30 parts, wherein the filler is mesoporous silica grafted graphene oxide filler.By using mesoporous silica grafted graphene oxide as the filler, the mesoporous silica is grafted to the surface of the graphene oxide, which greatly improves the dispersibility of the graphene oxide in the polyurethane prepolymer system, so that the graphene oxide can better play its role.This filler not only utilizes the heat conduction performance of the graphene oxide, but also adds mesoporous silica with a hollow structure, which is also conducive to improving the heat conduction performance of the polishing pad.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical mechanical polishing of semiconductor, in particular to a polyurethane polishing pad and a preparation method thereof. BACKGROUND

[0002] Chemical mechanical polishing (CMP) is a surface planarization processing technology which utilizes chemical and mechanical effects simultaneously in the process of semiconductor integrated circuit. In the process of integrated circuit manufacturing, part of the uneven surface comes from the deposition of silicon dioxide or silicon nitride film on the surface of the previously patterned silicon wafer. In the conventional CMP, the wafer is installed on a support device and is in contact with the polishing pad in the CMP equipment. The support device provides controllable pressure to the wafer to press the wafer on the polishing pad. An external driving force makes the polishing pad rotate relative to the wafer. At the same time, a polishing solution is provided between the wafer and the polishing pad, and the surface of the wafer is polished and flattened through the action of the polishing pad surface and the polishing solution.

[0003] The polishing pad is an important component in the CMP process. The polishing pad is usually composed of a polyurethane-based resin, and fillers are added to the polyurethane-based resin to improve the hardness and wear resistance of the polishing pad. CN116160355B discloses a heat dissipation polishing pad and a preparation method thereof, which comprises the following steps: curing a polyurethane mixture to form a polishing layer; the polyurethane mixture comprises a polyurethane prepolymer, a curing agent, microspheres and modified graphene, the modified graphene comprises at least one of hydroxylated graphene and aminated graphene; the microspheres are hollow spheres, and the microspheres comprise at least one of a copolymer and a homopolymer of ethylene, polyacrylonitrile, polycarbonate, silicone resin and polyester. The above method improves the thermal conductivity of polyurethane by adding graphene and microspheres in the polishing layer, improves the heat dissipation performance of the polishing pad, and further improves the uniformity of the heat dissipation of the polishing pad by improving the dispersion performance of the graphene and the microspheres in the polishing layer through the hydroxyl and amino groups on the modified graphene, thereby reducing the wafer polishing temperature and improving the wafer surface polishing quality. However, the modification of graphene by hydroxylated graphene and aminated graphene limits the dispersion of modified graphene in the polyurethane resin, and the function of graphene cannot be fully utilized. SUMMARY

[0004] Therefore, the present application aims to provide a polyurethane polishing pad and a preparation method thereof to solve the problems of poor dispersion of fillers in the polyurethane prepolymer system and single functionality of fillers.

[0005] To achieve the above-mentioned purposes, the technical scheme of the present application is as follows:

[0006] In one aspect, the present application provides a polyurethane polishing pad, comprising at least a polishing layer and a buffer layer, the polishing layer comprising the following raw materials by weight: 60-100 parts of polyurethane prepolymer, 1-10 parts of filler, and 10-30 parts of curing agent, wherein the filler is mesoporous silica grafted graphene oxide filler; the preparation method of the mesoporous silica grafted graphene oxide filler comprises the following steps:

[0007] Ultrasonic dispersion of mesoporous silica in ethanol for 5-8 min, then add silane coupling agent and stir for 6-8 h, centrifugal, washed with ethanol, vacuum drying to obtain mesoporous silica treated by silane coupling agent;

[0008] Ultrasonic dispersion of graphene oxide in dimethylformamide solution for 1-3 h, then add mesoporous silica treated by silane coupling agent and continue to ultrasonic for 2-3 h, after ultrasonic, stir at 100-110℃ for 3-5 h, after stirring, filter and wash with ethanol, vacuum drying to obtain mesoporous silica grafted graphene oxide filler.

[0009] Further, ultrasonic dispersion of graphene oxide in dimethylformamide solution is carried out at 10-15℃, and the addition of mesoporous silica treated by silane coupling agent is carried out at 10-15℃.

[0010] Further, the particle size of mesoporous silica grafted graphene oxide is D90=100-200 nm.

[0011] Further, the weight ratio of graphene oxide and mesoporous silica treated by silane coupling agent is 5:1.

[0012] Further, ultrasonic dispersion of graphene oxide in dimethylformamide solution is carried out for 2-3 h.

[0013] Further, the silane coupling agent is aminopropyltrimethoxysilane.

[0014] On the other hand, the present application also provides a preparation method of polyurethane polishing pad, using the above-mentioned polyurethane polishing pad, the preparation method comprising the following steps:

[0015] Polyurethane prepolymer is prepared by the reaction of polyisocyanate and polyol;

[0016] The polyurethane prepolymer is mixed with the filler prepared by mesoporous silica grafted graphene oxide, after the curing agent is melted, the two parts are mixed and injected into the mold, after curing, the temperature is reduced to room temperature, and the polishing pad is obtained after demolding;

[0017] After the polishing layer is processed into a groove structure, the polishing pad is obtained by bonding with the buffer layer.

[0018] Further, the curing time is 10-15h and the curing temperature is 100-120℃.

[0019] Further, the polyisocyanate is selected from one or more of diisocyanate, dimethylene phenyl diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, dicyclohexyl methane diisocyanate.

[0020] Further, the curing agent is selected from at least one of aliphatic diamine, aliphatic polyamine, aromatic diol, aromatic polyol, dichloroaniline.

[0021] Compared with the prior art, the polyurethane polishing pad and the preparation method thereof have the following advantages:

[0022] (1) The mesoporous silica grafted graphene oxide is used as the filler, the mesoporous silica is grafted to the surface of the graphene oxide, and the dispersibility of the graphene oxide in the polyurethane prepolymer system is greatly improved, so that the graphene oxide can better play a role.

[0023] (2) The filler can not only utilize the heat conduction performance of the graphene oxide, but also the mesoporous silica added has a hollow structure, which is also beneficial to improving the heat conduction performance of the polishing pad.

[0024] (3) The mesoporous silica grafted graphene oxide added to the polyurethane prepolymer system can improve the mechanical properties of the polishing pad, thereby prolonging the service life of the polishing pad. DETAILED DESCRIPTION

[0025] The application will be further described in conjunction with the specific embodiments. It should be first pointed out that the data in the following experimental examples are obtained by the inventors through a large number of experiments, and only a part of them is shown in the specification due to the limited space, and the ordinary skilled in the art can understand and implement the application based on the data. The examples are only used to illustrate the application and not to limit the scope of the application. In addition, it should be understood that after reading the content of the application, those skilled in the art can make various modifications or modifications to the application, and these modifications or modifications also fall within the scope of the application.

[0026] The graphene oxide used in the application is prepared by hummers method.

[0027] Examples 1-5 are related to the preparation of mesoporous silica grafted graphene oxide filler. Examples 6-10 are related to the preparation of polishing pad.

[0028] Example 1 Mesoporous silica grafted graphene oxide filler

[0029] The 50 g mesoporous silica was ultrasonically dispersed in 4 L of ethanol for 5 min, then 50 mL of aminopropyltrimethoxysilane was added and stirred for 6 h, centrifuged, washed with anhydrous ethanol for 3 times, and vacuum dried to obtain the modified mesoporous silica.

[0030] The 25 g of graphene oxide was ultrasonically dispersed in 8 L of dimethylformamide solution for 1 h, then 5 g of modified mesoporous silica was added and ultrasonically dispersed for 2 h, both of which were carried out in a 10℃ environment; after ultrasonic dispersion, it was stirred at 100℃ for 3 h, after stirring was completed, it was suction filtered, washed with anhydrous ethanol for 3 times, and vacuum dried to obtain the mesoporous silica grafted graphene oxide filler.

[0031] Example 2 Mesoporous silica grafted graphene oxide filler

[0032] The 50 g mesoporous silica was ultrasonically dispersed in 3 L of ethanol for 8 min, then 50 mL of aminopropyltrimethoxysilane was added and stirred for 8 h, centrifuged, washed with anhydrous ethanol for 3 times, and vacuum dried to obtain the modified mesoporous silica.

[0033] The 25 g of graphene oxide was ultrasonically dispersed in 5 L of dimethylformamide solution for 2 h, then 5 g of modified mesoporous silica was added and ultrasonically dispersed for 3 h, both of which were carried out in a 15℃ environment; after ultrasonic dispersion, it was stirred at 110℃ for 5 h, after stirring was completed, it was suction filtered, washed with anhydrous ethanol for 3 times, and vacuum dried to obtain the mesoporous silica grafted graphene oxide filler.

[0034] Example 3 Mesoporous silica grafted graphene oxide filler

[0035] The 50 g mesoporous silica was ultrasonically dispersed in 5 L of ethanol for 8 min, then 50 mL of aminopropyltrimethoxysilane was added and stirred for 8 h, centrifuged, washed with anhydrous ethanol for 3 times, and vacuum dried to obtain the modified mesoporous silica.

[0036] The 25 g of graphene oxide was ultrasonically dispersed in 8 L of dimethylformamide solution for 3 h, then 5 g of modified mesoporous silica was added and ultrasonically dispersed for 2 h, both of which were carried out in a 10℃ environment; after ultrasonic dispersion, it was stirred at 100℃ for 3 h, after stirring was completed, it was suction filtered, washed with anhydrous ethanol for 3 times, and vacuum dried to obtain the mesoporous silica grafted graphene oxide filler.

[0037] Example 4 Mesoporous silica grafted graphene oxide filler

[0038] The mesoporous silica and water were mixed in a ratio of 10:100 by weight, and ultrasonic treatment was performed for 30 min, and then sent to a plasma jet device for pretreatment, the parameters of the plasma jet device were power of 800 W, distance between jet nozzle and liquid surface of 8 m, and time of 2 min, and then centrifugation was performed, and the pretreated mesoporous silica was obtained after washing with anhydrous ethanol for 3 times and vacuum drying.

[0039] The 50 g of pretreated mesoporous silica was ultrasonically dispersed in 5 L of ethanol for 8 min, and then 50 mL of aminopropyltrimethoxysilane was added and stirred for 8 h, centrifuged, washed with anhydrous ethanol for 3 times, and vacuum dried to obtain modified mesoporous silica.

[0040] The 25 g of graphene oxide was ultrasonically dispersed in 8 L of dimethylformamide solution for 3 h, and then 5 g of modified mesoporous silica was added and ultrasonically dispersed for 2 h, both ultrasonic dispersions were performed at 10℃; after ultrasonic dispersion, stirring was performed at 100℃ for 3 h, and after stirring was completed, suction filtration was performed, and the graphene oxide filler grafted with mesoporous silica was obtained after washing with anhydrous ethanol for 3 times and vacuum drying.

[0041] Example 5 graphene oxide filler grafted with mesoporous silica

[0042] The mesoporous silica and water were mixed in a ratio of 10:120 by weight, and ultrasonic treatment was performed for 15 min, and then sent to a plasma jet device for pretreatment, the parameters of the plasma jet device were power of 800 W, distance between jet nozzle and liquid surface of 8 m, and time of 2 min, and then centrifugation was performed, and the pretreated mesoporous silica was obtained after washing with anhydrous ethanol for 3 times and vacuum drying.

[0043] The 50 g of pretreated mesoporous silica was ultrasonically dispersed in 3 L of ethanol for 8 min, and then 50 mL of aminopropyltrimethoxysilane was added and stirred for 8 h, centrifuged, washed with anhydrous ethanol for 3 times, and vacuum dried to obtain modified mesoporous silica.

[0044] The 25 g of graphene oxide was ultrasonically dispersed in 5 L of dimethylformamide solution for 2 h, and then 5 g of modified mesoporous silica was added and ultrasonically dispersed for 3 h, both ultrasonic dispersions were performed at 15℃; after ultrasonic dispersion, stirring was performed at 110℃ for 5 h, and after stirring was completed, suction filtration was performed, and the graphene oxide filler grafted with mesoporous silica was obtained after washing with anhydrous ethanol for 3 times and vacuum drying.

[0045] Example 6

[0046] The polyisocyanate and polyol react to form a polyurethane prepolymer. 100 g of the prepared polyurethane prepolymer is added to the A tank of the casting machine and heated to 60 °C, then 10 g of the mesoporous silica grafted graphene oxide filler prepared in Example 1 is added and mixed well to disperse the filler evenly in the polyurethane prepolymer; 10 g of MOCA is added to the B tank of the casting machine and heated to 120 °C to melt; the two parts are mixed at the head of the casting machine and then injected into the mold, and after 15 h of curing at 110 °C, it is cooled to room temperature, demolded to obtain a polishing layer. After the polishing layer is processed into a groove structure using a groove machine, it is bonded with a buffer layer to obtain a polishing pad.

[0047] Example 7

[0048] The polyisocyanate and polyol react to form a polyurethane prepolymer. 100 g of the prepared polyurethane prepolymer is added to the A tank of the casting machine and heated to 60 °C, then 10 g of the mesoporous silica grafted graphene oxide filler prepared in Example 2 is added and mixed well to disperse the filler evenly in the polyurethane prepolymer; 10 g of MOCA is added to the B tank of the casting machine and heated to 120 °C to melt; the two parts are mixed at the head of the casting machine and then injected into the mold, and after 15 h of curing at 110 °C, it is cooled to room temperature, demolded to obtain a polishing layer. After the polishing layer is processed into a groove structure using a groove machine, it is bonded with a buffer layer to obtain a polishing pad.

[0049] Example 8

[0050] The polyisocyanate and polyol react to form a polyurethane prepolymer. 60 g of the prepared polyurethane prepolymer is added to the A tank of the casting machine and heated to 60 °C, then 1 g of the mesoporous silica grafted graphene oxide filler prepared in Example 3 is added and mixed well to disperse the filler evenly in the polyurethane prepolymer; 20 g of MOCA is added to the B tank of the casting machine and heated to 120 °C to melt; the two parts are mixed at the head of the casting machine and then injected into the mold, and after 15 h of curing at 100 °C, it is cooled to room temperature, demolded to obtain a polishing layer. After the polishing layer is processed into a groove structure using a groove machine, it is bonded with a buffer layer to obtain a polishing pad.

[0051] Example 9

[0052] The polyisocyanate and polyol react to form a polyurethane prepolymer. 100 g of the prepared polyurethane prepolymer is added to the A tank of the casting machine and heated to 60 °C, then 10 g of the mesoporous silica grafted graphene oxide filler prepared in Example 4 is added and mixed well to disperse the filler evenly in the polyurethane prepolymer; 10 g of MOCA is added to the B tank of the casting machine and heated to 120 °C to melt; the two parts are mixed at the head of the casting machine and then injected into the mold, and after 15 h of curing at 110 °C, it is cooled to room temperature, demolded to obtain a polishing layer. After the polishing layer is processed into a groove structure using a groove machine, it is bonded with a buffer layer to obtain a polishing pad.

[0053] Example 10

[0054] The polyisocyanate and the polyol react to form a polyurethane prepolymer. In the A tank of the casting machine, 80 g of the prepared polyurethane prepolymer is added and heated to 60 °C, and then 5 g of the mesoporous silica grafted graphene oxide filler prepared in Example 5 is added and mixed well to uniformly disperse the filler in the polyurethane prepolymer; in the B tank of the casting machine, 30 g of MOCA is added and heated to 120 °C for melting; the two parts are mixed at the head of the casting machine and then injected into a mold, and after being cured at 120 °C for 10 h, it is cooled to room temperature, and then demolded to obtain a polishing layer. After the polishing layer is processed into a groove structure using a groove machine, it is bonded with a buffer layer to obtain a polishing pad.

[0055] Since the reaction of polyisocyanate and polyol to form a polyurethane prepolymer is a conventional prior art and is not the key point of the present application, it will not be described in detail here, and the specific reference can be made to the prior art.

[0056] The polyisocyanate is selected from one or more of diisocyanate, dimethylene phenyl diisocyanate (XDI), naphthalene diisocyanate (NDI), hexamethylene diisocyanate (HDI), dicyclohexyl methane diisocyanate (H12MDI), and the diisocyanate is selected from toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI). The polyol is generally an oligomeric polyol, and commonly used are polyether polyol and polyester polyol. In order to better compare the effects of the prepared polishing pads, the types and amounts of polyisocyanate and polyol used in Examples 6-10 and Comparative Examples 1-2 of the present application are exactly the same. More specifically, the polyisocyanate used in Examples 6-10 and Comparative Example 1-2 is diisocyanate, and the polyol used is polyether polyol.

[0057] The curing agent is selected from at least one of aliphatic diamine, aliphatic polyamine, aromatic diol, aromatic polyol, and dichloroaniline (MOCA).

[0058] Comparative Example 1

[0059] The preparation method of Comparative Example 1 is the same as that of Example 9, and the only difference is that 15 g of the mesoporous silica grafted graphene oxide filler prepared in Example 4 is added.

[0060] Comparative Example 2

[0061] Comparative Example 2 uses the method of Example 1 in CN116160355B to prepare a polishing pad.

[0062] The polishing pads prepared in Examples 6-10 and Comparative Examples 1-2 were used to polish wafers, with a polishing pressure of 8.5 kPa, a polishing pad rotation speed of 65 rpm, a wafer rotation speed of 55 rpm, and the same amount of Celsis CX2000 polishing liquid injected between the polishing pad and the wafer, and the polishing time was 30 min. The polishing temperature, surface roughness, wafer surface scratch condition, and polishing pad wear condition of the wafer surface were detected, and the results are shown in Table 1. The wafer surface scratch condition was observed using an atomic force microscope.

[0063] Table 1

[0064]

[0065] The polishing pads prepared in Examples 6-10 and Comparative Examples 1-2 were used to polish wafers, with a polishing pressure of 8.5 kPa, a polishing pad rotation speed of 65 rpm, a wafer rotation speed of 55 rpm, and the same amount of Celsis CX2000 polishing liquid injected between the polishing pad and the wafer, and the polishing time was 30 min. The polishing temperature, surface roughness, wafer surface scratch condition, and polishing pad wear condition of the wafer surface were detected, and the results are shown in Table 1. The wafer surface scratch condition was observed using an atomic force microscope.

[0066] Table 2

[0067]

[0068] As can be seen from Table 1, when the polishing pads prepared in Examples 6-10 were used to polish wafers, the polishing temperature of the wafer surface was 63-70℃, and the temperature distribution was uniform. In addition to reducing the polishing temperature of the wafer surface, the polishing pads can also ensure a smaller surface roughness and fewer scratches on the wafer surface, which is conducive to improving the polishing quality of the wafer surface.

[0069] Graphene has good thermal conductivity, and when used in a polishing pad, it can increase the thermal conductivity of the polishing pad, thereby improving the heat dissipation performance of the polishing pad and reducing the polishing temperature of the wafer. In Comparative Example 2, the graphene was only modified by hydroxylated graphene and / or aminated graphene, which limited the dispersion performance of the modified graphene in the polyurethane mixture, causing the voids to be not connected, and thus the heat dissipation performance of the polishing pad was also limited, and the polishing temperature of the wafer surface was as high as 75℃. In the present application, mesoporous silica grafted graphene oxide is used as a filler, and the mesoporous silica is grafted to the surface of the graphene oxide, which greatly improves the dispersion of the graphene oxide in the polyurethane prepolymer system. The hollow cavity of the modified mesoporous silica can wrap the graphene oxide layers and inhibit the stacking of the graphene oxide layers caused by van der Waals forces. In addition, this filler not only utilizes the thermal conductivity of the graphene oxide, but also the hollow structure of the added mesoporous silica is also conducive to improving the thermal conductivity of the polishing pad.

[0070] Compared with Example 6, the wafer surface polishing temperature of Examples 7-10 is lower. This is because the graphene oxide in Examples 7-10 is ultrasonically dispersed in the dimethylformamide solution for a longer time during the preparation of the filler, which is conducive to dispersing the graphene oxide into more single sheet structures by the cavitation effect of the ultrasonic waves, making the single sheet graphene oxide better combine with the mesoporous silica and exposing more active functional groups such as epoxy, hydroxyl, carboxyl, carbonyl and ester groups. The filler used in Examples 9-10 is further sent into a plasma jet device for pretreatment during preparation. The mesoporous silica can be better dispersed by the plasma jet technology to better graft with the graphene oxide, and the mesoporous silica can be introduced with oxygen-containing polar groups to improve its hydrophilicity, which helps the filler form an excellent dispersion in the polyurethane prepolymer system and better play the function of the filler.

[0071] The uniformly distributed filler can also improve the mechanical properties of the polishing pad, thereby improving the service life of the polishing pad. As shown in Table 2, compared with the polishing pad of Comparative Example 2, the service life of the polishing pad of Examples 6-10 can be improved to 48-61 h, thereby making the prepared polishing pad have long-term stable polishing performance. However, too much filler is not conducive to its mechanical properties. For example, a large amount of filler in Comparative Example 1 can easily cause scratches on the wafer, and can also make the polishing layer insufficiently elastic, thereby making the polishing pad easily damaged.

[0072] Although the present application is disclosed as above, the present application is not limited thereto. Any person skilled in the art, without departing from the spirit and scope of the present application, can make various modifications and changes, and therefore the protection scope of the present application should be subject to the scope defined by the claims.

Claims

1. A polyurethane polishing pad, characterized in that, The polyurethane polishing pad includes at least a polishing layer and a buffer layer. The polishing layer includes the following raw materials in parts by weight: 60-100 parts of polyurethane prepolymer, 1-10 parts of filler, and 10-30 parts of curing agent, wherein the filler is mesoporous silica-grafted graphene oxide. The preparation method of the mesoporous silica-grafted graphene oxide filler includes the following steps: Mesoporous silica was ultrasonically dispersed in ethanol for 5-8 min, then a silane coupling agent was added and stirred for 6-8 h. After centrifugation, the silica was washed with ethanol and vacuum dried to obtain silane coupling agent-treated mesoporous silica. Graphene oxide was ultrasonically dispersed in dimethylformamide solution for 1-3 hours, and then mesoporous silica treated with silane coupling agent was added and ultrasonication continued for 2-3 hours. After ultrasonication, the mixture was stirred at 100-110℃ for 3-5 hours. After stirring, the mixture was filtered, washed with ethanol, and vacuum dried to obtain mesoporous silica-grafted graphene oxide filler.

2. The polyurethane polishing pad according to claim 1, characterized in that, Graphene oxide was ultrasonically dispersed in a dimethylformamide solution at 10-15°C. Mesoporous silica treated with a silane coupling agent was added and ultrasonication was continued at 10-15°C.

3. The polyurethane polishing pad according to claim 1, characterized in that, The weight ratio of the mesoporous silica treated with graphene oxide and silane coupling agent is 5:

1.

4. The polyurethane polishing pad according to claim 1, characterized in that, Graphene oxide was ultrasonically dispersed in a dimethylformamide solution for 2-3 hours.

5. The polyurethane polishing pad according to claim 1, characterized in that, The silane coupling agent is aminopropyltrimethoxysilane.

6. A method for preparing a polyurethane polishing pad, characterized in that, The polyurethane polishing pad according to any one of claims 1 to 5 is prepared by a method comprising the following steps: Polyisocyanates and polyols react to form polyurethane prepolymers; The polyurethane prepolymer is thoroughly mixed with filler prepared by grafting mesoporous silica onto graphene oxide. After the curing agent melts, the two parts are mixed and injected into a mold. After curing, the mixture is cooled to room temperature and demolded to obtain a polished layer. After the polishing layer is processed into a groove structure, it is bonded to the buffer layer to obtain a polishing pad.

7. The method for preparing the polyurethane polishing pad according to claim 6, characterized in that, The curing time is 10~15h, and the curing temperature is 100~120℃.

8. The method for preparing the polyurethane polishing pad according to claim 6, characterized in that, The polyisocyanate is selected from one or more of diisocyanate, dimethylene phenyl diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate.

9. The method for preparing the polyurethane polishing pad according to claim 6, characterized in that, The curing agent is selected from at least one of aliphatic diamines, aliphatic polyamines, aromatic diols, aromatic polyols, and dichloroaniline.

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