CN103896287B - A kind of aspherical silicon dioxide gel and preparation method thereof - Google Patents

Abstract

The invention relates to the field of CMP technical polishing, in particular to a non-spherical silica sol and a preparation method thereof. The invention provides a non-spherical silica sol, which includes a liquid medium and sol particles, and the sol particles are formed by aggregating 2 to 10 silica colloidal particles. The beneficial effect of the product is that non-spherical silica seeds are formed through the induction of divalent metal ions. A thin layer of polystyrene (polymerized from styrene) is coated on the surface of the seed crystal. Since the seed is non-spherical, the curvature of the surface varies from place to place, both positive and negative. In places with negative curvature (that is, depressions), the surface tension is high, and polystyrene is not easy to cover, so a cavity is left to expose silicon dioxide. The continuously added silicic acid will preferentially attach to the surfaces where the silica is exposed, and undergo dehydration polymerization, finally forming large granular silica colloidal particles aggregated from 2-10 small particles.

Description

A kind of non-spherical silica sol and preparation method thereof

technical field

The invention relates to the field of CMP technical polishing, in particular to a non-spherical silica sol and a preparation method thereof.

Background technique

As the semiconductor industry develops along Moore's Law, chip integration increases exponentially over time, and performance also increases exponentially. Driving the processing technology to move towards higher current density, higher clock frequency and more interconnection layers. Due to the reduction of device size and the reduction of focal depth of optical lithography equipment, the flatness of acceptable resolution on the wafer surface is required to reach the nanometer level. In order to solve this problem, the chemical mechanical polishing (CMP) technology capable of achieving global planarization has become one of the important key processes of semiconductor manufacturing in one fell swoop. During the implementation of CMP technology, the polishing pad and the wafer are relatively rotated, and the polishing liquid flows between the two, so as to achieve the purpose of global planarization.

Among many applications of the CMP process, the polishing of silicon oxide dielectric materials has always occupied a very important position. There are mainly two types of abrasives in traditional CMP polishing slurries, namely fumed silica and colloidal silica, and colloidal silica is mostly spherical. The calcined silica is in the form of polygonal crystals. Although the edges and corners help to improve the polishing rate, the damage to the rigidity of the sheet is too serious, and the polished sheet has many scratches. The spherical colloidal silica abrasive scratches the surface of the chip very little, but the further improvement of the polishing rate has become a bottleneck restricting its application.

In order to increase the polishing rate without damaging the surface, non-spherical colloidal silica has attracted more and more attention. Many researchers have made many beneficial attempts. In CN101626979A, Toyoda Omori of Nissan Chemical Industry Co., Ltd. developed a kind of silica particles in an elongated shape, and the aqueous sol of the particles has very good coating properties. In the patent CN101402829A, Shi Weide invented a potato-shaped silicon dioxide particle, which has a large friction coefficient, a fast polishing rate, low hardness of the dried solid, and few scratches on the polishing sheet.

Contents of the invention

The present invention aims to overcome the deficiencies in the prior art, and provides a novel non-spherical silica sol and its preparation method. The obtained sol particles are non-spherical, and the shape is peanut-shaped in which 2 to 10 small particles are aggregated. Or quincunx shape, the particle size is 30-100nm, the friction coefficient is large, and the polishing efficiency is high. It has been verified that the use of the silica sol of the present invention can increase the polishing rate by more than 40%, and at the same time, there are fewer scratches on the polishing sheet.

In order to achieve the above object, the present invention provides a non-spherical silica sol in the first aspect, which includes a liquid medium and sol particles, and the sol particles are formed by aggregating 2 to 10 silica colloidal particles.

The non-spherical silica sol is characterized in that: the particle diameter of the silica colloidal particles is 30-100nm observed by scanning electron microscope, and the particle diameter measured by dynamic laser scattering (DLS) is 30-50nm; the liquid The medium is water with a pH of 8-10.

Preferably, the sol particles are aggregated from 2 to 10 colloidal silica particles and are in the shape of peanuts or plum blossoms.

The second aspect of the present invention provides the preparation method of the non-spherical silica sol, comprising the following steps:

1) In the active silicic acid solution containing _SiO2 weight percent 2-6%, pH=2.5-4, add water-soluble calcium salt, magnesium salt or their mixture aqueous solution, calcium salt, magnesium salt or their mixture and above-mentioned The weight ratio of _SiO2 in the active silicic acid is 1000-10000ppm, mixed, and shaken and stirred for 0.5-3h;

2) Add an alkali metal hydroxide or a water-soluble solution of an organic base to the aqueous solution prepared in step 1 for mixing, so that the molar ratio of SiO ₂ /M ₂ O is 10-300, and the pH of the solution is 8.5-10.5, wherein M Represents an alkali metal ion or an organic base molecule;

3) heating the solution obtained in step 2, the temperature is 70°C-110°C, and the heating and stirring time is 0.5-6 hours to prepare the starting silica sol;

4) passing the sol obtained in step 3 through a cation exchange bed and an anion exchange bed to further remove ions to make an alkaline silica sol with pH=9-11;

5) Dissolving an appropriate amount of styrene monomer in alcohol, stirring evenly, mixing with the sol obtained in step 4, and adding an appropriate amount of benzoyl peroxide, so that the volume ratio of styrene monomer to sol is 0.1-1:1000, The quality of benzoyl peroxide is 0.1-1g;

6) Stir the mixed solution obtained in step 5 at a temperature of 25-60° C. for 2-6 hours until the styrene is completely polymerized;

7) Add active silicic acid to the sol obtained in step 6. The addition method is: put the starting sol into a conventional heating device with stirring, heat and stir at a temperature of 95-110°C, and steam the water at a speed of 80-100°C. L/hour, add active silicic acid dropwise, the addition rate is 80-100 liters/hour, adopt the constant liquid surface growth method, control the amount of silicic acid added and the amount of evaporated water to be equal. The volume ratio of the amount of silicic acid added to the initial silica sol is 5-10:1, and the addition time is 10-30 hours to obtain a non-spherical silica sol with a silica content of 25-35%.

The third aspect of the present invention provides the application of the non-spherical silica sol in the field of CMP polishing.

The beneficial effect of the product is that non-spherical silica seeds are formed through the induction of divalent metal ions. A thin layer of polystyrene (polymerized from styrene) is coated on the surface of the seed crystal. Since the seed is non-spherical, the curvature of the surface varies from place to place, both positive and negative. In places with negative curvature (that is, depressions), the surface tension is high, and polystyrene is not easy to cover, so holes are left to expose silicon dioxide. The continuously added silicic acid will preferentially attach to the surfaces where the silica is exposed, and undergo dehydration polymerization, finally forming large granular silica colloidal particles aggregated from 2-10 small particles.

detailed description

Embodiments of the present invention are described below through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation modes, and various modifications or changes can be made to the details in this specification based on different viewpoints and applications without departing from the spirit of the present invention.

It should be noted that the process equipment or devices not specifically indicated in the following examples all adopt conventional equipment or devices in the art; all pressure values and ranges refer to absolute pressures.

In addition, it should be understood that one or more method steps mentioned in the present invention do not exclude that there may be other method steps before and after the combined steps or other method steps may be inserted between these explicitly mentioned steps, unless otherwise There are descriptions; it should also be understood that the combined connection relationship between one or more devices/devices mentioned in the present invention does not exclude that there may be other devices/devices before and after the combined devices/devices or those explicitly mentioned Other devices/apparatus can also be interposed between the two devices/apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the sequence of each method step or limit the scope of the present invention. The change or adjustment of its relative relationship is in In the case of no substantive change in the technical content, it shall also be regarded as the applicable scope of the present invention.

Embodiment 1 (common silica sol polishing experiment)

The composition of the polishing solution is as follows:

Colloidal silica particle content: 15wt%

Particle size: 35nm

Salt: no

Chelating agent: no

pH: 10 (adjusted by KOH solution)

The rest is deionized water

Polishing parameters and results are shown in Table 1

Embodiment 2 (using the silica sol polishing experiment of this patent method)

The composition of the polishing solution is as follows:

Colloidal silica particle content: 15wt%

Particle size: 37nm

Salt: no

Chelating agent: no

pH: 10 (adjusted by KOH solution)

The rest is deionized water

Polishing parameters and results are shown in Table 1

Table 1

Comparing the examples, it can be seen that the polishing liquid disclosed in the present invention can greatly improve the removal rate of the silicon dioxide film because of its non-spherical shape and large friction coefficient.

To sum up, the present invention effectively overcomes various shortcomings in the prior art and has high industrial application value.

The above-mentioned embodiments only illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical ideas disclosed in the present invention should still be covered by the claims of the present invention.

Claims (11)

1. A non-spherical silica sol, comprising a liquid medium and sol particles, the sol particles are formed by gathering 2 to 10 silica colloidal particles, and the preparation method of the non-spherical silica sol includes Follow the steps below: 1) In the active silicic acid solution of _SiO2 , add water-soluble calcium salt, magnesium salt or their mixture aqueous solution, mix and shake and stir; 2) adding an alkali metal hydroxide or a water-soluble solution of an organic base to the aqueous solution prepared in step 1 for mixing, so that the pH of the solution is 8.5-10.5; 3) heating and stirring the solution obtained in step 2 to make a starting silica sol; 4) passing the sol obtained in step 3 through a cation exchange bed and an anion exchange bed to make an alkaline silica sol; 5) Dissolving styrene monomer in alcohol, stirring evenly, mixing with the sol obtained in step 4, and adding benzoyl peroxide, so that the volume ratio of styrene monomer to sol is (0.1-1):1000, The quality of benzoyl peroxide is 0.1-1g; 6) The mixed solution obtained in step 5 is continuously stirred until the styrene is completely polymerized; 7) Add active silicic acid to the sol obtained in step 6 to prepare a non-spherical silica sol with a silica content of 25-35%. 2. A kind of non-spherical silica sol as claimed in claim 1, is characterized in that, described silica colloid particle is 30-100nm through scanning electron microscope observation particle diameter, and the particle diameter that dynamic laser scattering records is 30-50nm; the liquid medium is water, the pH is 8-10. 3 . The non-spherical silica sol according to claim 1 , wherein the sol particles are composed of 2 to 10 silica colloidal particles, and are in the shape of peanuts or plum blossoms. 4 . 4. The preparation method of the non-spherical silica sol according to any one of claims 1-3, comprising the steps of: 1) In the active silicic acid solution of _SiO2 , add water-soluble calcium salt, magnesium salt or their mixture aqueous solution, mix and shake and stir; 2) adding an alkali metal hydroxide or a water-soluble solution of an organic base to the aqueous solution prepared in step 1 for mixing, so that the pH of the solution is 8.5-10.5; 3) heating and stirring the solution obtained in step 2 to make a starting silica sol; 4) passing the sol obtained in step 3 through a cation exchange bed and an anion exchange bed to make an alkaline silica sol; 5) Dissolving styrene monomer in alcohol, stirring evenly, mixing with the sol obtained in step 4, and adding benzoyl peroxide, so that the volume ratio of styrene monomer to sol is (0.1-1):1000, The quality of benzoyl peroxide is 0.1-1g; 6) The mixed solution obtained in step 5 is continuously stirred until the styrene is completely polymerized; 7) Add active silicic acid to the sol obtained in step 6 to prepare a non-spherical silica sol with a silica content of 25-35%. 5. the preparation method of non-spherical silica sol as claimed in claim 4 is characterized in that, described step 1 is specifically, in containing SiO _2-6 % by weight, active silicic acid of pH=2.5-4 In the solution, add water-soluble calcium salt, magnesium salt or their mixture aqueous solution, the weight ratio of calcium salt, magnesium salt or their mixture to the SiO in the above _- mentioned active silicic acid is 1000-10000ppm, mix, and shake and stir for 0.5- 3h. 6. The preparation method of non-spherical silica sol as claimed in claim 4, is characterized in that, described step 2 is specifically, in the aqueous solution that step 1 makes, add the water-soluble compound of alkali metal hydroxide or organic base. The solutions are mixed so that the molar ratio of SiO ₂ /M ₂ O is 10-300, and the pH of the solution is 8.5-10.5, wherein M represents an alkali metal ion or an organic base molecule. 7. The preparation method of non-spherical silica sol according to claim 4, characterized in that, the step 3 is specifically heating the solution obtained in step 2 at a temperature of 70°C-110°C, and the heating and stirring time is 0.5 -6 hours to make the starting silica sol. 8. The preparation method of non-spherical silica sol as claimed in claim 4, it is characterized in that, described step 4 is specifically, the sol gained in step 3 is passed through cation exchange bed and anion exchange bed, further removes ion, makes Alkaline silica sol with pH=9-11. 9. The method for preparing non-spherical silica sol according to claim 4, characterized in that, the step 6 is specifically, continuously stirring the mixed solution obtained in step 5 at a temperature of 25-60° C. for 2-6 h, until the styrene is completely polymerized. 10. The preparation method of non-spherical silica sol as claimed in claim 4, it is characterized in that, said step 7 is specifically, adding active silicic acid to the sol obtained in step 6, and the addition method is: put the initial sol Put it into a conventional heating device with stirring, heat and stir at a temperature of 95-110°C, steam the water at a rate of 80-100 liters/hour, add active silicic acid dropwise, and add the speed at 80-100 liters/hour, using a constant Liquid surface growth method, the amount of silicic acid added is controlled to be equal to the amount of evaporated water; the volume ratio of the amount of silicic acid added to the initial silica sol is (5-10): 1, and the addition time is 10-30 hours to obtain the silica content It is 25-35% non-spherical silica sol. 11. The application of the non-spherical silica sol according to any one of claims 1-3 in the field of CMP polishing.