阅读说明：本技术 抛光垫及其制备方法、化学机械研磨设备 (Polishing pad, preparation method thereof and chemical mechanical polishing equipment ) 是由 郭宇轩 赵晟佑 于 2019-10-22 设计创作，主要内容包括：本发明提供了一种抛光垫及其制备方法、化学机械研磨设备,属于半导体技术领域。抛光垫的制备方法包括：制备抛光垫过渡结构,所述抛光垫过渡结构形成有多个凹槽,所述多个凹槽的开口位于所述抛光垫过渡结构的同一侧表面；利用无机纳米粒子填充满所述抛光垫过渡结构的凹槽；在所述抛光垫过渡结构上浇筑液态聚合物与固化剂的混合物,抽去液态聚合物和所述凹槽内的空气；将所述抛光垫过渡结构置于高于等于第一温度阈值的环境中,固化后的液态聚合物与所述抛光垫过渡结构组成所述抛光垫。本发明能够降低抛光垫的热膨胀系数。(The invention provides a polishing pad, a preparation method thereof and chemical mechanical polishing equipment, and belongs to the technical field of semiconductors. The method for preparing the polishing pad comprises the following steps: preparing a polishing pad transition structure, wherein the polishing pad transition structure is provided with a plurality of grooves, and the openings of the grooves are positioned on the same side surface of the polishing pad transition structure; filling the grooves of the polishing pad transition structure with inorganic nanoparticles; pouring a mixture of liquid polymer and curing agent on the polishing pad transition structure, and pumping out the liquid polymer and air in the groove; and placing the polishing pad transition structure in an environment higher than or equal to a first temperature threshold, wherein the solidified liquid polymer and the polishing pad transition structure form the polishing pad. The invention can reduce the thermal expansion coefficient of the polishing pad.)

1. A method of preparing a polishing pad, comprising:

preparing a polishing pad transition structure, wherein the polishing pad transition structure is provided with a plurality of grooves, and the openings of the grooves are positioned on the same side surface of the polishing pad transition structure;

filling the grooves of the polishing pad transition structure with inorganic nanoparticles;

pouring a mixture of liquid polymer and curing agent on the polishing pad transition structure, and pumping out the liquid polymer and air in the groove;

and placing the polishing pad transition structure in an environment higher than or equal to a first temperature threshold, wherein the solidified liquid polymer and the polishing pad transition structure form the polishing pad.

2. The method of preparing a polishing pad according to claim 1, wherein preparing the polishing pad transition structure comprises:

providing a mold, wherein the mold comprises a mold body and a plurality of raised T-shaped disc structures arranged on one side surface of the mold body, gaps are formed between adjacent disc structures, and the mold can be melted under the environment higher than a second temperature threshold value;

filling the gap with at least two inorganic nanoparticles of different particle sizes;

pouring a mixture of liquid polymer and curing agent on the mold, and pumping out the liquid polymer and air in the gap;

placing the mold in an environment equal to or lower than a third temperature threshold to solidify the liquid polymer;

and raising the ambient temperature to be above the second temperature threshold, melting the mold, and forming the polishing pad transition structure by the solidified liquid polymer.

3. The method of claim 2, wherein one of the at least two different sizes of inorganic nanoparticles is 500nm, and the other is 25 nm.

4. The method of claim 1 or 2, wherein the inorganic nanoparticles are titanium dioxide nanoparticles or silicon dioxide nanoparticles, and the liquid polymer is Polydimethylsiloxane (PDMS).

5. The method of producing a polishing pad according to claim 1 or 2, wherein the molar ratio of the liquid polymer to the curing agent is 1: 10.

6. the method for producing a polishing pad according to claim 2,

the first temperature threshold is 60 ℃, the second temperature threshold is 0 ℃, and the third temperature threshold is 0 ℃.

7. The method of claim 6, wherein the mold is ice.

8. The method of claim 1, wherein the inorganic nanoparticles have a particle size of 25 nm.

9. A polishing pad produced by the method for producing a polishing pad according to any one of claims 1 to 8.

10. The polishing pad of claim 9, wherein the polishing pad is comprised of polydimethylsiloxane PDMS and silica nanoparticles, and the polishing pad has a coefficient of thermal expansion of 40-60ppm/° c.

11. A chemical mechanical polishing apparatus comprising the polishing pad according to claim 9 or 10.

Technical Field

The invention relates to the technical field of semiconductors, in particular to a polishing pad, a preparation method thereof and chemical mechanical polishing equipment.

Background

In the process of wafer preparation, with the upgrading of the process technology, the size between the conducting wire and the grid electrode is continuously reduced, and the requirement of the photoetching technology on the flatness of the surface of the wafer is higher and higher. Chemical Mechanical Polishing (CMP) techniques are rapidly being developed and are widely used in planarization applications for semiconductor wafers, memory disks, and high-precision optical materials. Chemical mechanical polishing (cmp), which is also called chemical mechanical polishing, is a technique combining chemical etching and mechanical removal, and is the only technique that can achieve global planarization of a surface in current machining. The conventional CMP process is as follows: the material to be processed is fixed on a bracket, the material to be processed is pressed on a polishing pad fixed on a machine table under certain pressure in a mode that the surface to be polished faces downwards, and the material on the surface of a workpiece is removed by utilizing the mechanical cutting of abrasive particles and the chemical corrosion of an oxidant under the existence of polishing liquid by means of the relative rotation of the material to be processed and the polishing pad, so that a smooth surface is obtained. Wherein, the polishing pad is directly contacted with a silicon wafer and polishing solution in the chemical mechanical polishing, and the performance and the action of the polishing pad directly influence the chemical mechanical polishing result. In the polishing process, the silicon wafer rotates at a high speed on the surface of the polishing pad, a large amount of heat is generated, the polishing pad is heated and expanded to deform, and the polishing effect is seriously influenced.

Disclosure of Invention

The invention aims to provide a polishing pad, a preparation method thereof and chemical mechanical polishing equipment, which can reduce the thermal expansion coefficient of the polishing pad.

To solve the above technical problem, embodiments of the present invention provide the following technical solutions:

in one aspect, an embodiment of the present invention provides a method for preparing a polishing pad, including:

preparing a polishing pad transition structure, wherein the polishing pad transition structure is provided with a plurality of grooves, and the openings of the grooves are positioned on the same side surface of the polishing pad transition structure;

filling the grooves of the polishing pad transition structure with inorganic nanoparticles;

pouring a mixture of liquid polymer and curing agent on the polishing pad transition structure, and pumping out the liquid polymer and air in the groove;

and placing the polishing pad transition structure in an environment higher than or equal to a first temperature threshold, wherein the solidified liquid polymer and the polishing pad transition structure form the polishing pad.

Optionally, preparing the polishing pad transition structure comprises:

providing a mold, wherein the mold comprises a mold body and a plurality of raised T-shaped disc structures arranged on one side surface of the mold body, gaps are formed between adjacent disc structures, and the mold can be melted under the environment higher than a second temperature threshold value;

filling the gap with at least two inorganic nanoparticles of different particle sizes;

pouring a mixture of liquid polymer and curing agent on the mold, and pumping out the liquid polymer and air in the gap;

placing the mold in an environment equal to or lower than a third temperature threshold to solidify the liquid polymer;

and raising the ambient temperature to be above the second temperature threshold, melting the mold, and forming the polishing pad transition structure by the solidified liquid polymer.

Optionally, one of the at least two different inorganic nanoparticles has a particle size of 500nm and the other has a particle size of 25 nm.

Optionally, the inorganic nanoparticles are titanium dioxide nanoparticles or silicon dioxide nanoparticles, and the liquid polymer is Polydimethylsiloxane (PDMS).

Optionally, the molar ratio of the liquid polymer to the curing agent is 1: 10.

optionally, the first temperature threshold is 60 ℃, the second temperature threshold is 0 ℃, and the third temperature threshold is 0 ℃.

Optionally, the mold is ice.

Optionally, the inorganic nanoparticles have a particle size of 25 nm.

The embodiment of the invention also provides a polishing pad prepared by the preparation method of the polishing pad.

Optionally, the polishing pad is composed of polydimethylsiloxane PDMS and silica nanoparticles, and the coefficient of thermal expansion of the polishing pad is 40-60 ppm/DEG C.

The embodiment of the invention also provides chemical mechanical polishing equipment comprising the polishing pad.

The embodiment of the invention has the following beneficial effects:

in the scheme, the polishing pad is formed by the inorganic nano particles and the solidified liquid polymer, and the thermal expansion coefficient of the inorganic nano particles is lower than that of the solidified liquid polymer, so that the overall thermal expansion coefficient of the polishing pad can be effectively reduced, the deformation of the polishing pad caused by thermal expansion can be reduced, and the polishing effect can be optimized.

Drawings

FIG. 1 is a schematic flow chart illustrating a method for preparing a polishing pad according to an embodiment of the present invention;

FIG. 2 is a schematic flow chart illustrating the preparation of a transition structure of a polishing pad according to an embodiment of the present invention;

FIG. 3 is a schematic structural diagram of a mold according to an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a transition structure of a polishing pad according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a polishing pad according to an embodiment of the invention.

Reference numerals

100 mould

110 round table structure

200 polishing pad transition structure

300 polishing pad

Detailed Description

In order to make the technical problems, technical solutions and advantages to be solved by the embodiments of the present invention clearer, the following detailed description will be given with reference to the accompanying drawings and specific embodiments.

The temperature of the polishing pad surface is currently lowered mainly by external action, for example, by cooling water or polishing liquid. However, the heat transfer in the substance takes a certain time, so the effect of external cooling is slower to achieve. And directly reducing the thermal expansion coefficient of the polishing pad can reduce the deformation of the polishing pad caused by thermal expansion, thereby optimizing the polishing effect.

Embodiments of the present invention provide a polishing pad, a method for manufacturing the same, and a chemical mechanical polishing apparatus, which can reduce a thermal expansion coefficient of the polishing pad.

An embodiment of the present invention provides a method for preparing a polishing pad, as shown in fig. 1, including:

step 101: preparing a polishing pad transition structure, wherein the polishing pad transition structure is provided with a plurality of grooves, and the openings of the grooves are positioned on the same side surface of the polishing pad transition structure;

step 102: filling the grooves of the polishing pad transition structure with inorganic nanoparticles;

step 103: pouring a mixture of liquid polymer and curing agent on the polishing pad transition structure, and pumping out the liquid polymer and air in the groove;

step 104: and placing the polishing pad transition structure in an environment higher than or equal to a first temperature threshold, wherein the solidified liquid polymer and the polishing pad transition structure form the polishing pad.

In the embodiment, the polishing pad is formed by the inorganic nano particles and the solidified liquid polymer, and the thermal expansion coefficient of the inorganic nano particles is lower than that of the solidified liquid polymer, so that the overall thermal expansion coefficient of the polishing pad can be effectively reduced, the deformation of the polishing pad caused by thermal expansion can be reduced, and the polishing effect can be optimized. And the polishing pad of the embodiment has the advantages of simple preparation process, low cost and low energy consumption.

In one embodiment, as shown in FIG. 2, preparing the polishing pad transition structure comprises:

step 201: providing a mold, wherein the mold comprises a mold body and a plurality of raised T-shaped disc structures arranged on one side surface of the mold body, gaps are formed between adjacent disc structures, and the mold can be melted under the environment higher than a second temperature threshold value;

step 202: filling the gap with at least two inorganic nanoparticles of different particle sizes;

step 203: pouring a mixture of liquid polymer and curing agent on the mold, and pumping out the liquid polymer and air in the gap;

step 204: placing the mold in an environment equal to or lower than a third temperature threshold to solidify the liquid polymer;

step 205: and raising the ambient temperature to be above the second temperature threshold, melting the mold, and forming the polishing pad transition structure by the solidified liquid polymer.

The polishing pad transition structure is composed of inorganic nano particles and solidified liquid polymers, and the thermal expansion coefficient of the inorganic nano particles is low, so that the overall thermal expansion coefficient of the polishing pad transition structure can be effectively reduced, the deformation of the polishing pad due to thermal expansion can be reduced, and the polishing effect can be optimized.

In one embodiment, one of the at least two inorganic nanoparticles having different particle diameters is 500nm, and the other is 25 nm. Of course, the particle diameters of the at least two inorganic nanoparticles with different particle diameters are not limited to the above values, and other values may be adopted. The gap is filled with at least two different sizes of inorganic nanoparticles, primarily to maximize the fill of the gap, which maximizes the reduction of the thermal expansion coefficient of the polishing pad transition structure.

Preferably, the inorganic nanoparticles can be titanium dioxide nanoparticles or silicon dioxide nanoparticles, and the thermal expansion coefficients of the titanium dioxide nanoparticles and the silicon dioxide nanoparticles are low, so that the thermal expansion coefficient of the polishing pad can be effectively reduced. Of course, the inorganic nanoparticles used in the present invention are not limited to titanium dioxide nanoparticles and silicon dioxide nanoparticles, and other kinds of inorganic nanoparticles may be used as long as they have a relatively low thermal expansion coefficient (less than 20 ppm/deg.C).

Preferably, the liquid polymer may employ polydimethylsiloxane PDMS.

Preferably, the molar ratio of the liquid polymer to the curing agent is 1: 10. this ratio is used to facilitate the solidification of the liquid polymer.

In a specific example, the first temperature threshold may be 60 ℃, the second temperature threshold may be 0 ℃, and the third temperature threshold may be 0 ℃. Of course, the values of the first temperature threshold, the second temperature threshold, and the third temperature threshold are not limited to the above values, and may be other values.

Preferably, the mold is made of ice, the ice is convenient to obtain, the preparation cost of the polishing pad can be reduced, and the performance of the polishing pad cannot be influenced after the ice is melted. The material of the mold is not limited to ice, and other materials that can be melted at a low temperature (less than 20 degrees celsius) may be used.

Preferably, the particle size of the inorganic nanoparticles filling the grooves of the transition structure of the polishing pad may be 25nm, and of course, the particle size of the inorganic nanoparticles is not limited to this value, and other values may be adopted as long as the grooves of the transition structure of the polishing pad can be filled to the greatest extent.

In one embodiment, taking inorganic nanoparticles as silica nanoparticles as an example, the steps for preparing the polishing pad are as follows:

step 1, providing a mold 100 shown in fig. 3, wherein an upper half portion of fig. 3 is a front view of the mold 100, and a lower half portion of fig. 3 is a top view of the mold 100, wherein 110 is a T-shaped disc structure on the mold 100, a gap is formed between adjacent disc structures 110, and the mold 100 is made of ice;

step 2, filling two types of silicon dioxide nano particles with the particle sizes, wherein one type of silicon dioxide nano particles is 500nm, the other type of silicon dioxide nano particles is 25nm, and filling the particles until the gap is filled;

specifically, silica nanoparticles with the particle size of 500nm are firstly used for filling, and then silica nanoparticles with the particle size of 25nm are used for filling gaps among the silica nanoparticles with the particle size of 500nm, so that filling is ensured, and gaps are reduced.

Step 3, uniformly mixing the liquid polymer PDMS and the curing agent by stirring, wherein the molecular weight of the PDMS is about 350000, and the component ratio of the PDMS to the curing agent can be 1: 8-1: 20, specifically 1: 10;

step 4, pouring a mixture of liquid PDMS and a curing agent on the mold 100, placing the mold 100 into a vacuum device, removing the liquid PDMS and air in the gap, taking out the mold, placing the mold in an environment with the temperature lower than 0 ℃, and waiting for the PDMS to be cured;

step 5, after curing the PDMS, raising the ambient temperature to room temperature, and melting the mold 100 to form the polishing pad transition structure 200 shown in fig. 4;

step 6, filling silicon dioxide nano particles with the particle size of 25nm into a groove of the polishing pad transition structure 200, pouring a mixture of liquid PDMS and a curing agent on the polishing pad transition structure 200, putting the polishing pad transition structure 200 into a vacuum device, pumping air in the liquid PDMS and the groove, taking out, heating at 60 ℃, and waiting for the PDMS to be cured;

step 7, curing the PDMS to form the polishing pad 300 as shown in FIG. 5.

As shown in FIG. 5, the polishing pad 300 is composed of PDMS and silica nanoparticles, wherein the thermal expansion coefficient of the silica nanoparticles is about 0.6 ppm/deg.C, the thermal expansion coefficient of PDMS is about 300 ppm/deg.C, and the thermal expansion coefficient of the prepared polishing pad is about 40-60 ppm/deg.C, which is greatly reduced compared to the thermal expansion coefficient of the conventional polymer polishing pad. The polishing pad prepared by the embodiment has the advantages of simple process, low cost, low energy consumption, high stability, stable removal rate and the like.

In the embodiment, the polishing pad is prepared by filling the silicon dioxide nanoparticles in the groove structure, and the overall thermal expansion coefficient of the polishing pad is reduced by utilizing the advantage of low thermal expansion coefficient of the silicon dioxide nanoparticles. In addition, the preparation of the polishing pad is realized by casting and curing twice through the specific groove structure, so that the polishing pad also has the advantages of adjustable hardness and good water permeability.

The embodiment of the invention also provides a polishing pad prepared by the preparation method of the polishing pad. The polishing pad of the embodiment has a low thermal expansion coefficient, so that the deformation of the polishing pad caused by thermal expansion can be reduced, and the polishing effect can be optimized. And the polishing pad of the embodiment has the advantages of simple preparation process, low cost and low energy consumption.

In one embodiment, the polishing pad is comprised of polydimethylsiloxane PDMS and silica nanoparticles, and the coefficient of thermal expansion of the polishing pad is 40-60 ppm/DEG C. The coefficient of thermal expansion is greatly reduced compared to existing polymeric polishing pads. The polishing pad prepared by the embodiment has the advantages of simple process, low cost, low energy consumption, high stability, stable removal rate and the like.

Specifically, as shown in fig. 2 and 3, the polishing pad 300 is composed of a polishing pad transition structure 200 and silica nanoparticles filled in grooves of the polishing pad transition structure 200, the polishing pad transition structure 200 is composed of PDMS and silica nanoparticles doped in the PDMS, a thermal expansion coefficient of the silica is about 0.6 ppm/deg.c, a thermal expansion coefficient of the PDMS is about 300 ppm/deg.c, and the thermal expansion coefficient of the polishing pad can be effectively reduced by the silica nanoparticles.

The embodiment of the invention also provides chemical mechanical polishing equipment, which comprises the polishing pad, and the polishing pad of the embodiment has a low thermal expansion coefficient, so that in the process of polishing by using the polishing pad, a silicon wafer rotates at a high speed on the surface of the polishing pad, and after a large amount of heat is generated, the deformation of the polishing pad caused by thermal expansion is small, and the polishing effect can be optimized.

Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The use of "first," "second," and similar terms in this disclosure is not intended to indicate any order, quantity, or importance, but rather is used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.

While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.