CN113458966A - Polishing pad and manufacturing method thereof - Google Patents

Abstract

The invention relates to the technical field of semiconductor device processing, and discloses a polishing pad and a manufacturing method thereof. The polishing pad has a good polishing effect of the composite polishing pad, and can avoid the risk of foaming, falling off and the like of the composite polishing pad in the polishing process.

Description

Polishing pad and manufacturing method thereof

Technical Field

The invention relates to the technical field of semiconductor device processing, in particular to a polishing pad and a manufacturing method thereof.

Background

The high-speed development of the integrated circuit industry drives the digital and intelligent development of various industries such as artificial intelligence, internet of things, smart phones, MEMS and the like, the demand on various chips is increased sharply, and the continuous innovation of the advanced process of the integrated circuit is further promoted by the development trend of miniaturization, integration and low power consumption of the chips. The manufacturing process is improved, that is, more transistors can be inserted into a smaller chip, the operation efficiency of the processor is increased, and meanwhile, the power consumption is kept low, so that the method is suitable for various electronic devices and is used for meeting the future requirements on lightness and thinness. And the flattening of semiconductor crystal planes with higher accuracy is the basis for the realization of advanced processes.

The Chemical Mechanical Polishing (CMP) technology is the only technology that can realize global planarization at present, can meet the harsh requirements of 7nm chip manufacturing process, and has been widely applied in the semiconductor field. The CMP technique combines the physical grinding action of the superabrasive with the chemical etching action of the polishing slurry, and employs a polishing pad to planarize the surface of the substrate to be polished.

Currently, most used in CMP is a composite polishing pad, which is composed of a buffer layer and a polishing layer. In general, the buffer layer and the polishing layer are made of two materials, wherein the surface layer (i.e., the polishing layer) has a higher rigidity and hardness and a certain roughness, and the bottom layer (i.e., the buffer layer) has a lower rigidity and hardness and is more flexible. The composite polishing pad utilizes a high-hardness surface to bear polishing slurry for polishing, and utilizes a soft bottom layer to uniformly disperse applied pressure, so that an excellent polishing effect is realized. However, in the polishing process, the presence of high temperature, high shear force and chemical reagents has a great influence on the bonding layer of the composite polishing pad, so that the composite polishing pad has risks of foaming, falling off and the like, and further has a negative influence on the polishing process.

Disclosure of Invention

The purpose of the invention is: provided are a polishing pad and a method for manufacturing the same, which can prevent the risk of foaming and peeling during polishing while having a good polishing effect of a composite polishing pad.

In order to achieve the above object, according to one aspect of the present invention, there is provided a polishing pad comprising a substrate, a plurality of cells distributed in the substrate, the cells having a diameter size that is distributed in a gradient manner in a thickness direction of the substrate, and the cells having a diameter size that is gradually decreased from a bottom layer of the substrate toward a surface layer of the substrate, the cells having a uniform diameter size in a direction perpendicular to the thickness direction of the substrate.

Further, the substrate is made of a polyurethane material; the diameter size of the foam pores is 10-150 μm, and the adjacent foam pores are independent or connected with each other through pores.

Furthermore, the matrix is distributed with at least two kinds of the foam holes with different diameters, the diameter size of the foam hole positioned on the surface layer is 10-80 μm, and the diameter size of the foam hole positioned on the bottom layer is 80-150 μm.

Furthermore, a plurality of mutually independent open holes are distributed on the polishing surface of the base body, and the openings of the open holes are positioned on the polishing surface.

Furthermore, the diameter of the open pore is 10-50 μm, and the depth is 5-45 μm; the porosity of the polishing surface is 20-50%.

Furthermore, abrasive particles are arranged in the matrix.

Furthermore, the abrasive particles are made of ceramic materials, the abrasive particles are spherical, and the diameter of the abrasive particles is less than or equal to 50 nm.

Further, the thickness of the matrix is 1-2.5 cm, and the density of the matrix is 0.7-0.9 g/cm 3; the polished surface of the substrate has a hardness of 40-80 Shore D at a temperature of 25 ℃ or lower and an elongation at break of 50-300%.

In order to achieve the above object, according to another aspect of the present invention, there is provided a method of manufacturing a polishing pad, for manufacturing the polishing pad according to any one of the above aspects, the method comprising the steps of:

s101, preparing a sheet-shaped polymer blank from a polyurethane prepolymer, a curing agent, a filler and/or an additive;

s102, placing the polymer blank prepared in the step S101 into a high-pressure reaction kettle, introducing a physical foaming agent, controlling the temperature and the pressure of the reaction kettle to keep for a period of time, fully mixing the polymer blank and the physical foaming agent, and then releasing the pressure of the reaction kettle to normal pressure under the condition of high temperature and no foaming;

s103, rapidly placing the polymer blank processed in the step S102 on a single-sided hot table to form a temperature gradient so as to promote the polymer blank to foam in a gradient manner to form a plurality of cells.

In order to achieve the above object, according to another aspect of the present invention, there is provided a method of manufacturing a polishing pad, for manufacturing the polishing pad according to any one of the above aspects, the method comprising the steps of:

s201, preparing a sheet-shaped polymer blank from the polyurethane prepolymer, the curing agent, the filler and/or the additive;

s202, melting or solution blending the polymer body obtained in the step 201 with another incompatible or partially compatible polymer or small molecular substance to obtain a blend system;

s203, placing the blend system obtained in the step S202 in a mold with a temperature gradient for heat treatment for a period of time, and then rapidly cooling;

and S204, etching the blend system processed in the step S203 for a certain time by adopting a solvent dissolution etching method, cleaning the blend system by using ethanol, and fully drying the blend system in an oven.

Compared with the prior art, the polishing pad and the manufacturing method thereof have the advantages that: the diameters of the foam holes of the polishing pad in the thickness direction of the substrate are distributed in a gradient manner, and the diameters of the foam holes perpendicular to the thickness direction of the substrate are uniform, so that the hardness of the polishing pad is reduced along with the increase of the diameters of the foam holes in the thickness direction of the polishing pad, and the polishing effect of the polishing pad is gradually transited from a hard polishing pad to a soft polishing pad; meanwhile, the polishing pad forms a surface layer (polishing layer) and a bottom layer (buffer layer) with different hardness according to the difference of the diameter size of the pores, namely, the area with the large diameter of the pores is the bottom layer with lower hardness, the area with the small diameter of the pores is the surface layer with higher hardness, two materials with different hardness are not needed for bonding, and no bonding layer is arranged, so that the phenomenon that the polishing pad foams and falls off due to the action of high temperature, high shear and chemical reagents in the polishing process is avoided, and the product yield is improved.

Drawings

FIG. 1 is a schematic cross-sectional view of a polishing pad according to a first embodiment of the present invention;

FIG. 2 is a schematic cross-sectional view of a polishing pad according to a second embodiment of the present invention.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

In the description of the present invention, it should be understood that the terms "central", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., used herein are used in the orientation or positional relationship indicated in the drawings, which are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted" and "connected" are to be interpreted broadly, e.g., as being either fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Example one

As shown in fig. 1, according to one embodiment of the present invention, there is provided a polishing pad including a substrate 100, a plurality of cells 110, 120, 130 distributed in the substrate 100, wherein the diameter size of the cells 110, 120, 130 is distributed in a gradient manner along the thickness direction of the substrate 100, and the diameter size of the cells 110, 120, 130 is gradually decreased from the bottom layer of the substrate 100 to the surface layer of the substrate 100, and the diameter size of the cells in the direction perpendicular to the thickness direction of the substrate 100 is uniform.

Based on the scheme, the diameters of the foam holes 110, 120 and 130 in the thickness direction of the substrate 100 are distributed in a gradient manner, and the diameters of the foam holes perpendicular to the thickness direction of the substrate 100 are uniform, so that the hardness is increased along with the increase of the diameters of the foam holes in the thickness direction of the polishing pad, and the polishing effect is gradually transited from a hard polishing pad to a soft polishing pad, namely, the process from rough polishing to fine polishing can be realized in one polishing process of one polishing pad, and the polishing pad has a good polishing effect; meanwhile, the polishing pad forms a surface layer (polishing layer) and a bottom layer (buffer layer) with different hardness according to the difference of the diameter size of the pores, namely, the area with the large diameter of the pores is the bottom layer with lower hardness, the area with the small diameter of the pores is the surface layer with higher hardness, two materials with different hardness are not needed for bonding, and no bonding layer is arranged, so that the phenomenon that the polishing pad foams and falls off due to the action of high temperature, high shear and chemical reagents in the polishing process is avoided, and the product yield is improved.

It should be noted that the cells in the direction perpendicular to the thickness of the substrate 100 have a uniform diameter, which means that the cells in the direction do not need to have a completely equal diameter, and the above effect can be achieved by ensuring that the cells in the direction have a diameter within a certain error range, which can be determined according to practical situations, for example, the cells in the bottom layer of the polishing pad may have a diameter of 120 ± 10 nm.

Specifically, the polishing pad of the present embodiment can be used in the chemical mechanical polishing operation of an optical substrate or a semiconductor substrate, and the base 100 is made of a polyurethane material, specifically, a polyurethane prepolymer strengthening agent; the polyurethane prepolymer comprises at least one or more of polyester polyol, polyether polyol, polycarbonate polyol, polyolefin polyol, polyacrylate polyol and polymer polyol, and is polymerized with at least one or more of Toluene Diisocyanate (TDI), 4 '-diphenylmethane diisocyanate (MDI), hydrogenated 4, 4' -diphenylmethane diisocyanate (HMDI), isophorone diisocyanate (IPDI), p-phenylene diisocyanate (PPDI), naphthalene-1, 5-diisocyanate (NDI) and Hexamethylene Diisocyanate (HDI). Wherein the curing agent is at least one or more of an alcohol compound and an amine compound, such as 1, 4-butanediol, ethylene glycol, propylene glycol, 1, 6-hexanediol, 1, 4-cyclohexanediol, neopentyl glycol, ethanolamine, diethanolamine, 3 ' -dichloro-4 ', 4-diaminodiphenylmethane (MOCA), isobutyl 3, 5-diaminop-chlorobenzoate (DD-1604), diethyltoluenediamine, polypropylenediamine, 3, 5-dimethylthiotoluenediamine (DMTDA), ethylenediamine, diethylenetriamine, 4 ' -methylenebis (3-chloro-2, 6-diethylaniline) (M-CDEA).

The polyurethane material of the polishing pad can be synthesized by adding a catalyst to control the reaction rate of the polyurethane prepolymer and the curing agent. The catalyst species includes at least one or more of an organometallic-based compound and a tertiary amine-based compound. For example tetraethylmethylenediamine, triethylenediamine, triethylamine, tetramethylpropylamine, triethylamine, N-dimethylcyclohexylamine, N-methyldicyclohexylamine, N-methylmorpholine, N-ethylmorpholine, N '-dimethylpiperazine, N' -diethylpiperazine, 1, 3, 3-tetramethylpiperidine, bis (2-methylaminoethyl) ether, tetramethylbutanediamine, pentamethyldipropylenetriamine, trimethylhydroxyethylethylenediamine, dimethylethanolamine, stannous octoate, dibutyltin, dioctyltin, dibutyltin dilaurate, zinc isooctoate, lead isooctanoate, potassium oleate, zinc naphthenate, cobalt naphthenate, iron acetylacetonate, phenylmercuric acetate, phenylmercuric propionate.

As shown in FIG. 1, the diameter of the cells 110, 120, 130 is 10-150 μm, and the adjacent cells are independent of each other or connected with each other through pores, and the independent or connected are selected according to the hardness of the polishing pad, the size of the cells and the combination of actual requirements.

Specifically, as shown in fig. 1, three sizes of cells 110, 120, 130 whose cell diameters increase in a gradient from the bottom layer to the surface layer are formed in the substrate 100; h1, H2 and H3 represent thickness values of three layers with different hardness, wherein H1 represents a surface layer thickness value, H3 represents a bottom layer thickness value, the thickness direction of the polishing pad can be divided into two or more layers with different hardness according to the distribution of cell diameters, and the thickness value of each layer can be adjusted; accordingly, at least two different diameter sizes of cells are distributed in the substrate 100.

In this embodiment, as shown in FIG. 1, the cells 110 located in the skin layer have a diameter size of 10 to 80 μm, and the cells located in the base layer 130 have a diameter size of 80 to 150 μm. The polishing effect is better in this range.

As shown in fig. 1, a plurality of independent open holes 111, 112 are distributed on the polishing surface 113 of the base 100, openings of the open holes 111, 112 are located on the polishing surface 113, and the polishing surface 113 is located between the adjacent open holes 111, 112. Through setting up the ability that the open pore can improve the polishing pad and store up the polishing solution and increase the surface roughness of polishing face, make the polishing pad more adapt to the processing needs.

Specifically, the diameter of the open pore is 10 to 50 μm, and the depth thereof is 5 to 45 μm (i.e., the distance from the polished surface 113 to the lowermost end of the open pore); the porosity of the polishing surface 113 is 20-50%.

In this embodiment, the thickness of the substrate 100 is 1 to 2.5cm, and the density of the substrate 100 is 0.7 to 0.9g/cm 3; the polished surface 113 of the substrate 100 has a hardness of 40 to 80Shore D at 25 ℃ or lower and an elongation at break of 50 to 300%.

Example two

As shown in fig. 2, a second embodiment of the present invention provides another polishing pad, which is different from the first embodiment in that: abrasive particles 210 are disposed in the substrate 200, specifically, the abrasive particles 210 are made of a ceramic material, the ceramic material may be silicon dioxide, cerium dioxide, titanium dioxide or aluminum oxide, the abrasive particles 210 are spherical, and the diameter of the abrasive particles 210 is less than or equal to 50 nm. The polishing pad is modified by adding the abrasive particles 210, and the abrasive particles 210 exposed on the surface of the polishing pad form a new polishing surface, so that the removal rate in the polishing process can be effectively improved.

Other contents of this embodiment are the same as those of the first embodiment, and are not described herein again.

The polishing pads of the first and second embodiments can be used in the following scenarios: the polishing method comprises the steps of placing a polishing pad and an object to be polished in a CMP polishing machine, injecting polishing slurry into the CMP polishing machine, and simultaneously enabling the polishing pad and the object to be polished to rotate relatively, so that the object to be polished is polished.

EXAMPLE III

The third embodiment of the present invention provides a method for manufacturing a polishing pad, which is used for manufacturing the polishing pad of the above embodiments, and the method includes the following steps:

s101, preparing a sheet-shaped polymer blank from a polyurethane prepolymer, a curing agent, a filler and/or an additive;

specifically, poly-1, 4-butanediol adipate (PBA) and Toluene Diisocyanate (TDI) can be proportionally put into a three-neck flask to react for 2 hours at 80 ℃ to obtain a polyurethane prepolymer, wherein the NCO% of the polyurethane prepolymer is 5-12%. 1, 4-butanediol is selected as a curing agent, and dibutyltin dilaurate is selected as a catalyst, wherein the dosage of the 1, 4-butanediol and the dibutyltin dilaurate is 5 wt% and 0.5 wt% respectively based on the total mass of the polyurethane prepolymer. Silica nanoparticles having a particle diameter of 30nm were selected as the abrasive particles 210 (if the abrasive particles 210 were added), and the addition amount thereof was 10 wt%. And uniformly blending the polyurethane prepolymer, the curing agent, the catalyst and the abrasive particles, pouring the mixture into a mold, and curing and molding at 130 ℃ to obtain a sheet polyurethane blank.

S102, placing the polymer blank prepared in the step S101 into a high-pressure reaction kettle, introducing a physical foaming agent, controlling the temperature and the pressure of the reaction kettle to keep for a period of time, fully mixing the polymer blank and the physical foaming agent, and then releasing the pressure of the reaction kettle to normal pressure under the condition of high temperature and no foaming;

specifically, the polyurethane blank obtained in step S101 may be placed in a high-pressure reaction kettle, carbon dioxide is introduced into the kettle as a physical foaming agent, the temperature in the kettle is set to 200 ℃, the pressure is set to 12MPa, and the pressure is maintained for 2 hours, so that the physical foaming agent is fully absorbed in the polyurethane blank. And then, releasing the pressure to normal pressure to obtain a polyurethane blank which can fully absorb the carbon dioxide foaming agent.

S103, rapidly placing the polymer blank processed in the step S102 on a single-sided hot table to form a temperature gradient so as to promote the polymer blank to foam in a gradient manner to form a plurality of cells.

Specifically, the saturated green body can be quickly taken out of the high-pressure reaction kettle and placed in a mold with a temperature gradient field for foaming for 1 hour. By controlling the temperature of the mold and the gradient interval, the polishing pad with the polyurethane/silicon dioxide composite structure with the gradient cell structure can be obtained.

Example four

Another method for manufacturing a polishing pad according to a fourth embodiment of the present invention is a method for manufacturing a polishing pad according to the first embodiment, the method including the steps of:

s201, preparing a sheet-shaped polymer blank from the polyurethane prepolymer, the curing agent, the filler and/or the additive;

polyethylene glycol adipate (PEA) is selected as polyester polyol, isophorone diisocyanate (IPDI) is selected as isocyanate, ethylene glycol is selected as a curing agent, and stannous octoate is selected as a catalyst. Specifically, poly-1, 4-butanediol adipate (PBA) and Toluene Diisocyanate (TDI) can be proportionally put into a three-neck flask to react for 2 hours at 80 ℃ to obtain a polyurethane prepolymer, wherein the NCO% of the polyurethane prepolymer is 5-12%. 1, 4-butanediol is selected as a curing agent, and dibutyltin dilaurate is selected as a catalyst, wherein the dosage of the 1, 4-butanediol and the dibutyltin dilaurate is 5 wt% and 0.5 wt% respectively based on the total mass of the polyurethane prepolymer. Silica nanoparticles having a particle diameter of 30nm were selected as the abrasive particles 210 (if the abrasive particles 210 were added), and the addition amount thereof was 10 wt%. And uniformly blending the polyurethane prepolymer, the curing agent, the catalyst and the abrasive particles, pouring the mixture into a mold, and curing and molding at 130 ℃ to obtain a sheet polyurethane blank.

S202, melting or solution blending the polymer body obtained in the step 201 with another incompatible or partially compatible polymer or small molecular substance to obtain a blend system;

specifically, the following steps are carried out according to 3: 1, weighing 1.5kg of the polyurethane and the polyethylene-octene copolymer (POE) in total mass, mixing in an internal mixer XSM-2/80 at the mixing temperature of 200 ℃, the screw rotation speed of 50r/min and the mixing time of 8min to prepare the PU/PEO blend.

S203, placing the blend system obtained in the step S202 in a mold with a temperature gradient for heat treatment for a period of time, and then rapidly cooling;

specifically, the PU/PEO blend sample was placed in a mold with a temperature gradient field for heat treatment for 1 hour, and then removed and placed in an ice water bath for cooling.

And S204, etching the blend system processed in the step S203 for a certain time by adopting a solvent dissolution etching method, cleaning the blend system by using ethanol, and fully drying the blend system in an oven.

Specifically, the blend sample after heat treatment is etched in a 60 ℃ n-heptane solution for 2 hours, then washed by ethanol and fully dried in an oven, and the polyurethane polishing pad with the gradient porous structure can be obtained.

In summary, the polishing pad and the method for manufacturing the polishing pad provided by the embodiment of the invention have the following advantages:

the cells of the polishing pad vary uniformly in a gradient in the thickness direction of the polishing pad and are uniform in size in a direction perpendicular to the thickness of the polishing pad. That is, it is considered that the polishing effect gradually transits from a hard polishing pad to a soft polishing pad as the cell diameter increases in the thickness direction. That is, it can be considered that the process from rough polishing to fine polishing can be realized in one polishing process of one polishing pad.

The polishing pad can be divided into two or more layers in the thickness direction of the pad according to the diameter distribution of the cells, and comprises a polishing layer and a buffer layer. The polishing pad has the advantages that the bonding layer is not arranged between the polishing layer and the buffer layer of the polishing pad, so that the phenomenon that the polishing pad is foamed and falls off due to the action of high temperature, high shear and chemical reagents in the polishing process is effectively avoided, and the product yield is improved.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and substitutions can be made without departing from the technical principle of the present invention, and these modifications and substitutions should also be regarded as the protection scope of the present invention.

Claims (10)

1. The polishing pad is characterized by comprising a substrate, wherein a plurality of cells are distributed in the substrate, the diameter size of each cell is distributed in a gradient manner along the thickness direction of the substrate, the diameter size of each cell is gradually reduced from the bottom layer of the substrate to the surface layer of the substrate, and the diameter size of each cell in the thickness direction of the substrate is uniform.

2. The polishing pad of claim 1, wherein the substrate is made of a polyurethane material; the diameter size of the foam pores is 10-150 μm, and the adjacent foam pores are independent or connected with each other through pores.

3. The polishing pad according to claim 1, wherein said matrix has at least two different diameter sizes of said cells distributed therein, said cells located in said surface layer having a diameter size of 10 to 80 μm, and said cells located in said bottom layer having a diameter size of 80 to 150 μm.

4. The polishing pad of claim 1, wherein the polishing surface of the substrate has a plurality of independent open pores distributed thereon, and the openings of the open pores are located on the polishing surface.

5. The polishing pad of claim 4, wherein the open pores have a diameter of 10-50 μm and a depth of 5-45 μm; the porosity of the polishing surface is 20-50%.

6. The polishing pad of claim 1, wherein abrasive particles are disposed within the matrix.

7. The polishing pad of claim 6, wherein the abrasive particles are made of a ceramic material, the abrasive particles are spherical, and the abrasive particles have a diameter of 50nm or less.

8. The polishing pad of claim 1, wherein the matrix has a thickness of 1-2.5 cm and a density of 0.7-0.9 g/cm 3; the polished surface of the substrate has a hardness of 40-80 Shore D at a temperature of 25 ℃ or lower and an elongation at break of 50-300%.

9. A method for manufacturing a polishing pad, for use in manufacturing the polishing pad as set forth in any one of claims 1 to 8, comprising the steps of:

s101, preparing a sheet-shaped polymer blank from a polyurethane prepolymer, a curing agent, a filler and/or an additive;

s102, placing the polymer blank prepared in the step S101 into a high-pressure reaction kettle, introducing a physical foaming agent, controlling the temperature and the pressure of the reaction kettle to keep for a period of time, fully mixing the polymer blank and the physical foaming agent, and then releasing the pressure of the reaction kettle to normal pressure under the condition of high temperature and no foaming;

s103, rapidly placing the polymer blank processed in the step S102 on a single-sided hot table to form a temperature gradient so as to promote the polymer blank to foam in a gradient manner to form a plurality of cells.

10. A method for manufacturing a polishing pad, for use in manufacturing the polishing pad as set forth in any one of claims 1 to 8, comprising the steps of:

s201, preparing a sheet-shaped polymer blank from the polyurethane prepolymer, the curing agent, the filler and/or the additive;

s202, melting or solution blending the polymer body obtained in the step 201 with another incompatible or partially compatible polymer or small molecular substance to obtain a blend system;

s203, placing the blend system obtained in the step S202 in a mold with a temperature gradient for heat treatment for a period of time, and then rapidly cooling;

and S204, etching the blend system processed in the step S203 for a certain time by adopting a solvent dissolution etching method, cleaning the blend system by using ethanol, and fully drying the blend system in an oven.

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