Preparation method of SiO2 sol polishing solution

Abstract

The invention relates to a preparation method of a SiO2 sol polishing solution, which comprises the following steps: by taking one of tetraethyl orthosilicate and tetramethyl orthosilicate as a silicon source, spraying and combusting by using compressed air, spraying and collecting the generated SiO2 into a collecting tank by using deionized water to form hydrosol, circularly spraying the hydrosol in the collecting tank by using a circulating pump, and when the solid content of SiO2 in the collecting tank reaches 15% (wt%), stopping the spraying of the hydrosol in the collecting tank. The SiO2 sol polishing solution is exported as the SiO2 sol polishing solution; the particle size of the SiO2 sol is smaller than 100 nm, and the SiO2 sol is spherical or sphere-like and meets the requirements of high-end CMP (chemical mechanical polishing) liquid.

Description

Technical Field

[0001] The present invention relates to a preparation method of SiO 2 sol-gel polishing liquid, belonging to the technical field of electronic materials for chip manufacturing. Background Art

[0002] For the polishing of substrates for chips, wafers, and the polishing process in chip processing, there are strict requirements for the uniformity of CMP (Chemical Mechanical Polishing) polishing liquid microspheres and impurities (including but not limited to metal ions).

[0003] Currently, international leading wafer foundries are advancing towards more advanced process technologies such as 7nm, 5nm, and even 3nm. The domestic leading wafer foundry has also achieved mass production of 14nm and started to layout the research and development of processes such as 10nm and 7nm. These advanced logic chip processes will require more polishing steps. For example, the key CMP process required for logic chip processes below 14nm will reach more than 20 steps, and the number of polishing liquids used will increase from five or six polishing liquids in the 90nm process to more than twenty. The TIR (Total Indicator Reading, the difference between the highest point and the lowest point on the polished surface of the silicon wafer) of the flatness of wafer fine polishing should be one-twentieth of the line width, approximately 0.3 - 0.4nm; for the polishing in the subsequent chip preparation process, SiO 2 sol-gel polishing liquid is required; currently, such high-performance CMP polishing liquids are mainly prepared by Cabot in the United States.

[0004] To prepare SiO 2 sol-gel, it can be prepared by using gaseous SiO 2 or SiO 2 prepared by precipitation method and then redispersed. However, for SiO 2 sol-gel used as CMP polishing liquid, it is necessary to ensure that the SiO 2 sol-gel particles are not larger than 100nm, the particle morphology is spherical, and the content of impurity ions is not greater than 10ppb. For SiO 2 powder prepared by precipitation method, it cannot be used because the particle size is too large; gaseous SiO 2 , is the primary particles with a particle size of 7 - 40nm obtained by high-temperature hydrolysis and condensation of organohalosilane in a hydrogen-oxygen combustion flame. As the particles move away from the flame and the temperature decreases, the particles collide, adhere, and sinter with each other to form aggregates. The silica aggregates are formed by fusing numerous particles together, with an irregular shape, mainly branched, and containing chloride ions at the ppm level. As a raw material for CMP polishing liquid, it is obviously not suitable.

[0005] To solve the above problems and prepare a high-performance SiO 2 sol-gel polishing liquid, the present invention is specifically completed. Summary of the Invention

[0006] The object of the present invention is to provide a preparation method of a SiO sol polishing liquid with a particle size less than 100 nm, spherical shape, and an impurity ion content not greater than 10 ppb. 2

[0007] To achieve the above object, the present invention specifically adopts the following steps: Using tetraethyl orthosilicate or tetramethyl orthosilicate as the silicon source, compressed air is provided by an air compressor for spray combustion, and the generated SiO 2 is collected in a collection pool by spraying deionized water and becomes a hydrosol, and the hydrosol in the collection pool is circulated and sprayed by a circulation pump; The air entering the air compressor must be filtered to prevent large particle impurities from appearing in the polishing liquid due to floating dust in the air, which may cause scratches on the polished crystal surface; When the solid content of SiO in the collection pool 2 reaches 15% (wt%), it is exported as a SiO 2 sol polishing liquid, and deionized water is replaced again.

[0008] The advantages of the present invention are as follows: Using tetraethyl orthosilicate or tetramethyl orthosilicate as the silicon source, and spraying and burning with filtered compressed air, nano-silica particles are prepared and quickly brought into the collection pool by the sprayed water film, ensuring uniform particles. There is not enough time for them to collide and fuse with other particles in the flame, and a nano-SiO 2 sol polishing liquid can be prepared; in addition, no impurity ions are introduced; the production process is economical and practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is the field emission electron scanning photograph of the SiO 2 sol polishing liquid prepared in Example 1; Figure 2 is the field emission electron scanning photograph of the SiO 2 sol polishing liquid prepared in Example 2. EMBODIMENTS

[0011] The present invention will be further described below in conjunction with specific embodiments: Using tetraethyl orthosilicate or tetramethyl orthosilicate as the silicon source, horizontally spraying and burning with filtered compressed air, arranging 10 inverted U-shaped nozzles above it along the flame direction, spraying deionized water, and the deionized water and SiO 2The particles are collected in the collection tank to form a sol, which is injected into the spraying device again by a circulating water pump and sprayed out through a spray head, and so on in a cycle; when the solid content of the sol is detected by a turbidimeter to be 15% (wt%), the spray combustion is stopped and the cycle is stopped; the SiO 2 sol polishing liquid is discharged and deionized water is re-injected. Examples

[0012] The SiO 2 sol polishing liquid prepared by using tetraethyl orthosilicate as the silicon source, from Figure 1 It can be seen that the SiO 2 sol particles are spherical, with a particle size within 100 nm, mainly distributed between 40 and 60 nm; the contents of impurity ions potassium, sodium, and iron that may be introduced are detected by ICP-MS (inductively coupled plasma-mass spectrometry), and the cumulative amount is less than 10 ppb. Examples

[0013] The SiO 2 sol polishing liquid prepared by using tetramethyl orthosilicate as the silicon source, from Figure 2 It can be seen that the SiO 2 sol particles are spherical-like, with a particle size within 100 nm, mainly distributed between 50 and 70 nm; the contents of impurity ions potassium, sodium, and iron that may be introduced are detected by ICP-MS (inductively coupled plasma-mass spectrometry), and the cumulative amount is less than 10 ppb.

[0014] It should be noted that the above specific embodiments can enable those skilled in the art to understand the present invention more comprehensively, but do not limit the present invention in any way. Therefore, although the embodiments of this specification have described the present invention in detail, those skilled in the art should understand that the present invention can still be modified or equivalently replaced; and all technical solutions and their improvements that do not depart from the spirit and scope of the present invention should be covered by the protection scope of this invention patent.

Claims

1. A preparation method of a SiO2 sol polishing liquid, characterized in that Using one of tetraethyl orthosilicate and tetramethyl orthosilicate as the silicon source, spraying and burning with compressed air provided by an air compressor to generate SiO 2 Spraying with deionized water and collecting it in a collection pool to form a sol, and using a circulation pump to circulate and spray the sol in the collection pool. When the solid content of SiO in the collection pool 2 reaches 15% (wt%), it is used as SiO 2 sol polishing liquid is exported.

2. The preparation method of a SiO2 sol polishing liquid according to claim 1, characterized in that The air entering the air compressor must be filtered.

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