TWI651377B - Chemical mechanical polishing liquid and preparation method thereof - Google Patents

Abstract

The invention provides a chemical mechanical polishing liquid and a preparation method thereof. The chemical mechanical polishing liquid includes cerium oxide nano particles prepared by hydrothermal synthesis, a dispersant, deionized water, a lubricant, and a pH adjuster. When preparing a chemical mechanical polishing liquid, the cerium dioxide nano particles formed by the hydrothermal synthesis method are put into a regenerative furnace for annealing, water, a dispersant are added, and the friction between the cerium dioxide nano particles is reduced by a lubricant. Finally, The pH value can be adjusted to 7.0. Through this preparation method, the particle size of the cerium dioxide nano particles is made uniform, and the removal efficiency of the polishing liquid is further increased by the lubricant, the quality of the chemical polishing liquid is improved, and the operation is convenient and simple.

Description

Chemical mechanical polishing liquid and preparation method thereof

The invention relates to the grinding field of a semiconductor manufacturing process, in particular to a chemical mechanical polishing liquid and a preparation method thereof.

With the upgrading of wafer manufacturing process technology and the reduction of wire and gate sizes, the lithography technology has become increasingly demanding for the flatness of the wafer surface. IBM introduced the development of CMOS products in 1985 and successfully applied them in 1990. In 64MB DRAM production. Since 1995, chemical mechanical polishing (also known as chemical mechanical polishing (CMP)) technology has developed rapidly and is widely used in the semiconductor industry; its principle is to combine chemical corrosion and mechanical removal, which is currently in mechanical processing. The only technology that can achieve global planarization of the surface.

Referring to FIG. 1, since the polishing pad in the CMP is made of a material such as polyurethane, the surface of the polishing pad is deformed during the polishing process, and the contact area 11A of the polishing pad 11 in direct contact with the substrate 12 does not produce a polishing effect. Therefore, the polishing efficiency of the non-contact area 11B determines the polishing rate of the entire polishing sheet. As shown in FIG. 1, if the particle size dispersion of the cerium oxide 13 in the polishing liquid is large, for the non-contact area 11B, only the larger-sized particles participate in mechanical grinding, and the polishing efficiency is low. At the same time, nano-particles with larger particle sizes also cause polishing damage to the polished surface, which is not conducive to the high-precision polishing of inorganic insulating films.

As an important rare earth compound, cerium dioxide has been widely used in environmental detection instrument sensitive materials, automobile exhaust catalysts, oxygen storage materials, fuel cells and other fields due to its special physical and chemical properties. In recent years, with the rapid development of the integrated circuit industry, CMP technology, as the only technology capable of realizing global planarization, has become a key technology in the field of IC manufacturing. The polishing solution using cerium dioxide as an abrasive can chemically react with SiO ₂ , and chemically bond Si-O-Ce to polish SiO ₂ , so the removal rate of SiO ₂ is fast. And unlike polishing pastes such as colloidal SiO _{2 that} need to be stored in alkaline solutions, cerium dioxide-based polishing solutions can be stable under neutral pH conditions, so they are isolated in shallow trenches, and interlayer dielectric (ILD) polishing, etc. There are a wide range of applications in the planarization step.

In addition, since the hardness of cerium oxide is lower than that of silicon oxide particles and alumina particles, it is not easy to cause surface damage, so it can also be used for mirror polishing of light masks, optical lenses, and III-IV gallium arsenide wafers. In the cerium oxide-based CMP polishing liquid, in order to obtain a faster polishing rate and a higher surface flatness, cerium oxide nano particles with a small amount of trace metal contaminants, a spherical shape, and a uniform particle size distribution are urgently needed.

In semiconductors, there are many substrate materials made of single crystal silicon. Single crystal silicon is a single crystal of silicon with a basically complete lattice structure. For chemical mechanical polishing of single crystal silicon, traditional chemical mechanical polishing solutions The material removal rate on the surface of crystalline silicon is not high, and it is easy to cause mechanical damage to single crystal silicon. Therefore, how to better use cerium oxide particles in chemical mechanical polishing processes, especially in the chemical mechanical polishing process of single crystal silicon, Become an urgent issue.

In order to achieve the above object, the present invention provides a chemical mechanical polishing liquid and a preparation method for solving the above problems.

The invention provides a chemical mechanical polishing liquid, which is prepared by hydrothermal synthesis method. Cerium dioxide nano particles, dispersant, deionized water, lubricant and pH adjuster.

In a preferred embodiment, for polishing single crystal silicon, the cerium oxide nano particles prepared by the hydrothermal synthesis method are single crystals.

In a preferred embodiment, the dispersant is a water-soluble polymer compound with a pH value in the range of 5.0 to 8.0.

In a preferred embodiment, the dispersant is selected from polyvinyl alcohol or polyacrylic acid or ammonium polyacrylate.

In a preferred embodiment, the pH adjusting agent is a potassium hydroxide solution or a nitric acid solution.

In a preferred embodiment, the lubricant is spherical polystyrene nano particles, carbon nano particles, or layered graphene and molybdenum disulfide.

The invention also provides a method for preparing a chemical-mechanical polishing liquid, which includes the following steps: annealing molding: placing the cerium dioxide nano particles formed by the hydrothermal synthesis method in a muffle furnace for annealing; and preparing the polishing liquid: The annealed cerium oxide nano particles were added with deionized water, a dispersant, and a lubricant in this order, followed by stirring, and then a pH adjuster was added to adjust the pH of the polishing solution to 7.0.

In a preferred embodiment, the annealing temperature in the annealing and forming step is 500 ° C., and the annealing time is 3 hours (h).

In a preferred embodiment, the concentration of the cerium source solution in the cerium oxide nano particles formed by the hydrothermal synthesis method is less than 0.5 mol / L (mol / L), and the particle size of the cerium oxide nano particles after annealing is 260 nanometers (nm) ~ 1900nm.

In a preferred embodiment, the weight ratio of the cerium dioxide nano particles to the lubricant is 100: 1 to 1000: 1.

Compared with the prior art, the present invention has the beneficial effects that the chemical mechanical polishing liquid and the preparation method thereof provided by the present invention include the cerium oxide nano particles prepared by hydrothermal synthesis, a dispersant, Deionized water, lubricant and pH adjuster. It was found in the study that the polishing efficiency of spherical cerium oxide particles for single crystal silicon wafers is higher than that of spherical SiO ₂ , which is conducive to ultra-precise surface processing of single crystal silicon wafers. Therefore, the hydrothermally synthesized cerium dioxide nano particles are single crystals, and their particle size uniformity is better than the existing dissolution method and electrolytic method, which is conducive to the rapid removal of the polished surface and reduces the mechanical damage of the polished surface. The lubricant has the effect of reducing the friction between cerium dioxide particles, which increases the relative movement between the cerium dioxide particles and the polished surface, further improving the polishing efficiency.

11‧‧‧Polishing pad

11A‧‧‧Contact area

11B‧‧‧ Non-contact area

12‧‧‧ substrate

13‧‧‧Cerium oxide

Figure 1 is a schematic diagram of a conventional chemical mechanical polishing procedure.

FIG. 2 is a scanning electron microscope (SEM) photograph of cerium dioxide nano particles according to an embodiment of the present invention.

FIG. 3 shows an X-ray diffraction (XRD) pattern of cerium dioxide nano particles according to an embodiment of the present invention.

FIG. 4 is a SEM photograph of a ceria nanoparticle according to an embodiment of the present invention.

The present invention is further described in detail below with reference to the drawings and specific embodiments. The advantages and features of the present invention will be clearer according to the description of this case and the scope of patent application. To be clear, The drawings are in a very simplified form, and all use inaccurate proportions, which are only used to facilitate and clearly explain the purpose of the embodiments of the present invention.

Examples

Example one

This embodiment provides a chemical-mechanical polishing liquid, including cerium oxide nano particles prepared by hydrothermal synthesis, a dispersant, deionized water, and a pH adjuster.

Wherein, the dispersant is a water-soluble polymer compound with a pH value in the range of 5.0 to 8.0, and polyacrylic acid is used in this embodiment.

Among them, the selected pH adjusting agent is a potassium hydroxide solution.

The invention also provides a method for preparing a chemical mechanical polishing liquid, which includes the following steps: Step 1: Weigh 1.08 grams (g) of ammonium cerium nitrate and disperse it in 12 milliliters (mL) of deionized water, and then add 0.63 g of polyvinylpyrrolidone. Stir well to a homogeneous solution for 30 minutes; Step 2: Use a micro-sampler to slowly add 0.14 mL of ammonia hydroxide (addition rate is 10 μl / min (10 μL / min)) to the configured solution in step 1. Keep the solution continuously stirred during the process; Step 3: Place the configured solution in a 40mL reaction kettle, and place the reaction kettle in a programmable controller (PLC) controlled oven at 5 ° C / min (° C / min). The heating rate is increased to 200 ° C and maintained for 24 hours, and then naturally cooled to room temperature; Step 4: Take out the reaction precipitate, wash it with deionized water, ethanol, and centrifuge, put it in an oven and dry at 60 ° C; Step 5: The dried product was put into a muffle furnace and annealed to form CeO ₂ nano particles with good crystallinity. The annealing temperature was 500 ° C. and the annealing time was 3 hours. Please refer to FIG. 2. The scanning electron microscope results show that the prepared cerium dioxide nanoparticles are single crystals with uniform morphology and size, uniform particle size distribution, and a particle size of 340 nm. Referring to Figure 3, X-ray diffraction (XRD) analysis of the product obtained after annealing shows that it is consistent with the cerium dioxide standard card (JCPDS34-0394), and there are no other peaks, so it can be seen The particle size of cerium dioxide nano particles is relatively uniform. The transmission electron microscope selective area diffraction (SAED) results also show that the cerium dioxide nano particles have good crystallinity. Step 6: Add step 5 to high-speed dispersed deionized water (stirring speed greater than 300 rpm) to form The weight ratio of cerium oxide nano particles, cerium oxide nano particles and deionized water is 1: 100. After the dispersion is uniform, add the polyacrylic acid dispersant and continue stirring. The polyacrylic acid concentration is 0.01 mol / L (mol / L), add a layered molybdenum disulfide lubricant after uniform preparation, the layered molybdenum disulfide lubricant has a surface area ranging from 1 μm ² to 100 μm ² and a thickness of less than 3 nm. The weight ratio of cerium dioxide nano particles to the lubricant is 500: 1, increase the stirring speed to 500 rpm, continue stirring for 30 minutes, and finally adjust the pH of the polishing solution to 7.0 by adding a pH adjuster to obtain a cerium oxide polishing solution based on uniform nano particles.

Example two

Step 1: Weigh 1.08g of cerium ammonium nitrate and disperse it in 12mL of deionized water, then add 0.63g of polyvinylpyrrolidone, and stir thoroughly to a homogeneous solution after 30 minutes; Step 2: Place the configured solution in a 40mL reaction kettle, place The reaction kettle was placed in an oven controlled by PLC and heated to 200 ° C at a heating rate of 5 ° C / min, and kept for 24 hours, and then naturally cooled to room temperature; Step 4: Take out the reaction precipitate, wash it with deionized water, ethanol and centrifuge, put it in an oven and dry it at 60 ℃; Step 5: Put the dried product into a reheating furnace and anneal to form a well-crystallized dioxide Ce nano particles. The annealing temperature was 500 ° C, and the annealing time was 3 hours. Please refer to Figure 4. Scanning electron microscopy results show that the prepared cerium oxide nanoparticles are single crystals with uniform morphology and size, uniform particle size distribution, and a particle size of 1.9 μm. Step 6: Deionized water dispersed at high speed (stirred Add the ceria nano-particles formed in step 5 to the rotating speed greater than 300 revolutions per minute. After the dispersion is uniform, add the polyacrylic acid dispersant and continue to stir. The polyacrylic acid concentration is 0.01mol / L. After the preparation is uniform, add the layered graphite. As a lubricant, the layered graphene lubricant has a surface area ranging from 1 μm 2 to 100 μm 2 and a thickness of less than 3 nm. The cerium dioxide nano particles and the layered lubricant are 500: 1, and the stirring speed is increased to 500 rpm, and the stirring is continued for 30 minutes. Minutes, and finally adjusted the pH of the polishing solution to 7.0 by adding a pH adjuster to obtain a cerium oxide polishing solution based on uniform nano particles.

Example three

Step 1: Weigh 1.08g of cerium ammonium nitrate dispersed in 12mL of deionized water and 12mL of ethanol, then add 0.63g of polyvinylpyrrolidone, and stir thoroughly to a uniform solution after 30 minutes; Step 2: Use a microsampler to slowly reduce 0.14mL Add ammonia hydroxide (addition rate is 10 μL / min) to the solution already configured in step 1, and keep the solution continuously stirred during the injection process; Step 3: Put the configured solution into a 40mL reaction kettle, put the reaction kettle into a PLC controlled oven, and raise the temperature to 200 ° C at a temperature increase rate of 5 ° C / min for 24 hours, and then naturally cool to room temperature; Step 4: Take out the reaction precipitate, wash it with deionized water, ethanol and centrifuge, put it in an oven and dry it at 60 ℃; Step 5: Put the dried product into a reheating furnace and anneal to form a well-crystallized dioxide For cerium nanoparticles, the annealing temperature is 500 ° C, and the annealing time is 3 hours. Scanning electron microscopy results show that the prepared cerium oxide nanoparticles are single crystals with uniform morphology and size, uniform particle size distribution, and particle size of 260 nm. Step 6: Deionized water dispersed at high speed (stirring speed greater than 300 rpm) ) Add annealed cerium oxide nano particles, and after uniform dispersion, add polyacrylic acid dispersant and continue stirring, the concentration of polyacrylic acid is 0.01mol / L, and add spherical polystyrene nano particles for lubrication Agent, spherical lubricant particle size range is 20 ~ 200nm, weight ratio of cerium dioxide nano particles to lubricant is 600: 1, increase stirring speed to 500 rpm, continue stirring for 30 minutes, and finally adjust by adding pH The pH value of the polishing liquid is adjusted to 7.0 by the agent, and a cerium oxide polishing liquid based on uniform nano particles can be obtained.

The present invention provides a chemical mechanical polishing liquid and a preparation method thereof. The chemical mechanical polishing liquid includes cerium dioxide nano particles prepared by hydrothermal synthesis, a dispersant, deionized water, and a pH adjuster to prepare a chemical mechanical polishing liquid. At this time, the cerium oxide nano particles formed by the hydrothermal synthesis method are put into a regenerative furnace for annealing, and then water, a dispersant and a lubricant are added, and then the pH value can be adjusted to 7.0. This preparation method makes the cerium dioxide The particle size of the nano particles is uniform, which improves the quality of the chemical polishing liquid, and the operation is convenient and simple.

The content of the specific embodiments described above is used to describe the present invention in detail. However, these embodiments are only used for illustration and are not intended to limit the present invention. Those skilled in the art can understand that various changes or modifications made to the present invention without departing from the scope defined by the scope of the attached patent application fall into a part of the present invention.

Claims (9)

A chemical mechanical polishing liquid, comprising: cerium oxide nano particles prepared by a hydrothermal synthesis method, a dispersant, deionized water, a lubricant, and a pH adjuster; wherein the cerium dioxide nano The particles are single crystals. For example, the chemical mechanical polishing liquid of the first patent application scope is used for polishing single crystal silicon. For example, the chemical-mechanical polishing liquid in the first item of the patent application range is characterized in that the dispersant is a water-soluble polymer compound with a pH ranging from 5.0 to 8.0. For example, the chemical-mechanical polishing liquid of claim 3 in the scope of patent application, characterized in that the dispersant is polyvinyl alcohol or polyacrylic acid or ammonium polyacrylate. For example, the chemical-mechanical polishing liquid of claim 1, wherein the pH adjusting agent is a potassium hydroxide solution or a nitric acid solution. For example, the chemical-mechanical polishing liquid in the first scope of the patent application, wherein the lubricant is spherical polystyrene nano particles, carbon nano particles, or layered graphene and molybdenum disulfide. A method for preparing a chemical-mechanical polishing liquid, which comprises the following steps: annealing and forming: annealing the cerium oxide nano particles formed by the hydrothermal synthesis method in a regenerative furnace, wherein the annealing temperature is 500 ° C. and annealing The time is 3 hours (h); polishing solution production: adding annealed cerium oxide nano particles in order to deionized water, dispersant, and lubricant and stirring, and then adding a pH adjuster to adjust the pH of the polishing solution to 7.0 Wherein, the annealed cerium oxide nano particles are single crystals. For example, the method for preparing a chemical mechanical polishing liquid according to item 7 of the application, wherein the hydrothermal synthesis method forms a cerium source solution concentration in the cerium dioxide nano particles of less than 0.5 mol / L (mol / L) The particle size of the cerium oxide nano-particles after annealing is 260 nanometers (nm) to 1900 nanometers. For example, the method for preparing a chemical mechanical polishing liquid according to item 7 of the application, wherein the weight ratio of the cerium dioxide nano particles to the lubricant is 100: 1 to 1000: 1.