Preparation method of semiconductor-grade quartz sand

Abstract

The invention relates to a preparation method of semiconductor-grade high-purity quartz sand. The preparation method comprises the following steps: by taking ethyl silicate as a main material and high-purity water greater than 14 megohm as a hydrolytic agent under crosslinking catalysis of organic acid, carrying out hydrolysis crosslinking polymerization on ethyl silicate to generate a polymeric silicate-silicic acid polymer, and carrying out solid-liquid separation to obtain a precursor; and carrying out temperature-controlled calcination on the precursor through a specific temperature control program to finally obtain the semiconductor-grade high-purity quartz sand.

Description

Technical Field

[0001] The present invention relates to a method for preparing semiconductor-grade quartz sand Background Art

[0002] Quartz sand mainly consists of silicon dioxide (SiO 2 ), which has stable chemical properties, is insoluble in acids (but slightly soluble in KOH solution), has a melting point as high as 1750 °C, and has high fire resistance. It is usually milky white or colorless and translucent, with a greasy luster. Its Mohs hardness is 7, it is hard, and has strong wear resistance. The density is about 2.65 g / cm³, and the bulk density varies depending on the particle size.

[0003] The application of high-purity quartz sand in the semiconductor industry is very crucial, and the specific applications include:

[0004] Wafer production: High-purity quartz sand is used to manufacture quartz crucibles, which are important containers for producing polysilicon and monocrystalline silicon, and silicon materials are the basic raw materials for semiconductor integrated circuits. In the process of silicon wafer manufacturing, high-purity quartz sand products such as quartz tubes, quartz boats, and quartz rings are used in key steps such as silicon wafer diffusion, oxidation, and cleaning in high-temperature furnaces.

[0005] Photomask substrate: High-precision quartz glass substrates are the main basic materials for photomask substrates, which are used in the lithography process. The technical barriers are relatively high, and it is one of the bottlenecks restricting the minimum line width.

[0006] Packaging materials: High-purity quartz sand is the main encapsulation material in the semiconductor industry. When used in combination with epoxy resins, curing agents, various additives, etc., it can save packaging costs.

[0007] Electronic substrate materials: High-purity quartz sand is also used as electronic substrate materials for preparing monocrystalline silicon and polysilicon, which are the basis for semiconductor device manufacturing.

[0008] High-temperature process steps: In the high-temperature areas during semiconductor chip manufacturing, such as diffusion steps, the quartz glass materials used need to have excellent high-temperature resistance, and these materials are often produced by the electrofusion method.

[0009] Low-temperature process steps: In the low-temperature areas of semiconductor manufacturing, such as etching processes, the quartz materials used are produced by the gas fusion method.

[0010] Quartz devices: Quartz devices used in silicon wafer and wafer manufacturing can be divided into two categories: high-temperature area devices and low-temperature area devices, such as furnace tubes, diffusion tubes, glass boat racks, etc. in the high-temperature area, and quartz rings in the low-temperature area.

[0011] Semiconductor-grade silicon dioxide meets very high standards in terms of purity, crystal structure, impurity content, surface roughness, etc. Summary of the Invention

[0012] In order to solve the problems in the production of semiconductor-grade quartz sand, we have designed a preparation method for chip-grade quartz sand.

[0013] This invention is divided into two parts. The first part is the preparation of the precursor, and the second part is the calcination of the quartz sand.

[0014] Put raw materials such as tetraethyl orthosilicate, crosslinking catalyst, and high-purity water into the reaction tank, start stirring, and mix evenly.

[0015] The crosslinking catalyst is formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, citric acid, benzoic acid, phenylacetic acid, salicylic acid, gallic acid, tartaric acid. Acetic acid, oxalic acid, malonic acid, and salicylic acid are preferred.

[0016] The ratio of tetraethyl orthosilicate to the crosslinking catalyst is 100:1 - 300:1, preferably 150:1 - 200:1.

[0017] The ratio of tetraethyl orthosilicate to high-purity water is 1:0.7 - 1:2.5, preferably 1:0.83 - 1:1.67.

[0018] Slowly heat up the above-mentioned mixed materials.

[0019] Heat up to 45 - 55°C and stop heating.

[0020] When reflux starts to appear in the reflux condenser, open the jacket of the reaction kettle to cool down and control the temperature of the reaction kettle.

[0021] The reaction temperature is 40 - 110°C, preferably 68 - 94°C

[0022] Keep warm under these conditions. The holding time is 2 - 12 h, preferably 4 - 8 h.

[0023] After the heat preservation is completed, cool down to 40°C, centrifuge to obtain the pre-polymer, and wash it with an appropriate amount of high-purity water after centrifugation.

[0024] The number of rinsing times is 1 - 6 times, preferably 2 - 3 times; the mass ratio of the water volume for each rinsing to tetraethyl orthosilicate is 1:5 - 1:100, preferably 1:15 - 1:80.

[0025] Dry the pre-polymer according to the programmed temperature rise drying conditions.

[0026] The vacuum degree for drying is -0.06_-0.1 MPa, preferably -0.085_-0.098 MPa; the holding time is 2 - 8 h, preferably the holding time is 4 - 6 h; the temperature is 40 - 120°C, preferably 60 - 80°C.

[0027] The pre-polymer is calcined under programmed temperature conditions, and the calcination temperature has three stages.

[0028] The first stage is the dehydration stage, with a temperature of 200 - 450 °C and a heat preservation time of 1 - 6 hours, preferably 300 - 350 °C and a heat preservation time of 2 - 4 hours.

[0029] The second stage is the decarbonization stage, with a temperature of 500 - 800 °C and a heat preservation time of 1 - 8 hours, preferably a temperature of 600 - 700 °C and a heat preservation time of 3 - 5 hours.

[0030] The third stage is the dehydroxylation stage, with a temperature of 900 - 1400 °C and a heat preservation time of 0.5 - 4 hours, preferably a temperature of 1000 - 1100 °C and a heat preservation time of 1 - 2 hours.

[0031] The calcined product is cooled down according to the programmed cooling. After cooling down to below 80 °C, the product is obtained.

[0032] The cooling rate is 1 - 10 °C, preferably 4 - 6 °C. Description of the Drawings

[0033] Figure 1 It is a schematic flow diagram of a preparation method for semiconductor-grade high-purity quartz sand. Detailed Embodiments

[0034] In order to make the objectives, technical solutions and advantages of the present invention more obvious, the following examples are combined to further elaborate on the present invention in detail. It should be understood that the specific examples described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] A preparation method for semiconductor-grade quartz sand

[0036] Example 1

[0037] 41.6 kg of tetraethyl orthosilicate is added to a 100 L reaction kettle, then 15 kg of high-purity water is added, and then 30 ml of glacial acetic acid is added, and they are stirred evenly. The temperature is slowly raised to 50 °C, the temperature increase is stopped, and the reaction is allowed to spontaneously increase the temperature to 81 °C, and reflux heat preservation is carried out for 5 hours. The temperature is lowered to 40 °C. Centrifugation is carried out with a centrifuge. After high-speed drying, it is washed with 1 L of high-purity water, and the washing is repeated three times to obtain the pre-polymer.

[0038] The centrifuged pre-polymer is put into a vacuum drying device, the vacuum degree is controlled at -0.092 MPa, the heating device is turned on, and the temperature is raised to 80 °C for drying for 6 hours.

[0039] The above-mentioned product is put into a calcination furnace, the temperature is raised to 350 °C and heat preservation is carried out for 2 hours; then the temperature is raised to 600 °C and heat preservation is carried out for 3 hours; finally, the temperature is raised to 1100 °C and heat preservation is carried out for 1.5 hours.

[0040] After heat preservation, cool down to 80°C at a rate of 5°C / min. 10.5 kg of product is obtained.

[0041] Example 2

[0042] Add 41.6 kg of tetraethyl orthosilicate to a 100 L reactor, then add 20 kg of high-purity water, and then add 30 g of oxalic acid. Stir evenly. Slowly heat up to 48°C, stop heating, and let the reaction spontaneously heat up. The temperature rises to 82°C, and keep it under reflux for 4 h. Cool down to 40°C. Centrifuge with a centrifuge, spin-dry at high speed, wash with 0.8 L of high-purity water, and repeat the washing three times to obtain the pre-polymer.

[0043] Put the centrifuged pre-polymer into a vacuum drying device, control the vacuum degree at -0.096 MPa, turn on the heating device, heat up to 80°C, and dry for 5 h.

[0044] Put the above-mentioned product into a calcination furnace, heat up to 300°C, and keep it for 3 h; then heat up to 700°C and keep it for 5 h; finally heat up to 1050°C and keep it for 1 h.

[0045] After heat preservation, cool down to 80°C at a rate of 6°C / min. 11.2 kg of product is obtained.

[0046] Example 3

[0047] Add 41.6 kg of tetraethyl orthosilicate to a 100 L reactor, then add 22 kg of high-purity water, and then add 35 g of citric acid. Stir evenly. Slowly heat up to 55°C, stop heating, and let the reaction spontaneously heat up. The temperature rises to 83°C, and keep it under reflux for 6 h. Cool down to 40°C. Centrifuge with a centrifuge, spin-dry at high speed, wash with 1.2 L of high-purity water, and repeat the washing three times to obtain the pre-polymer.

[0048] Put the centrifuged pre-polymer into a vacuum drying device, control the vacuum degree at -0.098 MPa, turn on the heating device, heat up to 70°C, and dry for 8 h.

[0049] Put the above-mentioned product into a calcination furnace, heat up to 400°C, and keep it for 2 h; then heat up to 750°C and keep it for 1 h; finally heat up to 1000°C and keep it for 2 h.

[0050] After heat preservation, cool down to 80°C at a rate of 8°C / min. 10.8 kg of product is obtained.

[0051] The test results are shown in Table 1

[0052] Table 1

[0053]

[0054] In the present invention, unless otherwise clearly specified or limited, the first feature being "above" or "below" the second feature may include direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "below", "beneath" and "under" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely means that the horizontal height of the first feature is lower than that of the second feature

[0055] The above describes the present invention and its implementation manners. Such description is not restrictive. What is shown in the drawings is only one of the implementation manners of the present invention, and the actual structure is not limited thereto. Generally speaking, if those of ordinary skill in the art are inspired by it and, without departing from the gist of the present invention, design similar structural manners and embodiments to this technical solution without creative efforts, they shall fall within the protection scope of the present invention.

Claims

1. A method for preparing semiconductor-grade high-purity quartz sand, characterized in that: The following steps are involved: Step 1: Add ethyl silicate, cross-linking catalyst and high-purity water into a reaction tank, start stirring and mix evenly; Step 2, slowly heating the mixed materials; Step 3: When reflux begins to occur in the reflux condenser, the jacket of the reactor is opened to cool down and control the temperature of the reactor; Step 4, keeping warm under the conditions of step 3; Step 5: After the heat preservation is completed, the temperature is lowered to 40°C, and the prepolymer is obtained by centrifugation. After the centrifugation is completed, it is washed with an appropriate amount of high-purity water; Step 6: Dry the prepolymer according to the programmed heating and drying conditions; Step 7, calcining the precursor according to programmed temperature conditions; Step 8: Cool the calcined product to below 80° C. to obtain the product.

2. A method for preparing semiconductor-grade high-purity quartz sand as claimed in claim 1, characterized in that: In step 1, the ratio of ethyl silicate to the cross-linking catalyst is 100:1-300:1; In step 1, the cross-linking catalyst is a combination of one or more of formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, citric acid, benzoic acid, phenylacetic acid, salicylic acid, gallic acid, and tartaric acid.

3. A method for preparing semiconductor-grade high-purity quartz sand as claimed in claim 2, characterized in that: In step 1, the ratio of ethyl silicate to high-purity water is 1:0.7-1:2.

5.

4. A method for preparing semiconductor-grade high-purity quartz sand as claimed in claim 1, characterized in that: The reaction temperature in step 3 is 40-110°C.

5. A method for preparing semiconductor-grade high-purity quartz sand as claimed in claim 1, characterized in that: The insulation time in step 4 is 2-12h.

6. A method for preparing semiconductor-grade high-purity quartz sand as claimed in claim 1, characterized in that: In step 5, high-purity water is used for elution, and the number of elutions is 1-6 times, and the mass ratio of the amount of water for each elution to ethyl silicate is 1:5-1:

100.

7. A method for preparing semiconductor-grade high-purity quartz sand as claimed in claim 1, characterized in that: In step six, the drying vacuum degree is -0.06_-0.1MPa; the insulation time is 2-8h; and the temperature is 40-120°C.

8. A method for preparing semiconductor-grade high-purity quartz sand as claimed in claim 1, characterized in that: The calcination temperature in step 7 includes three stages: The first stage is the dehydration stage, the temperature is 200-450℃, and the insulation time is 1-6h; the second stage is the decarburization stage, the temperature is 500-800℃, and the insulation time is 1-8h; the third stage is the dehydroxylation stage, the temperature is 900-1400℃, and the insulation time is 0.5-4h.

9. A method for preparing semiconductor-grade high-purity quartz sand as claimed in claim 1, characterized in that: The cooling rate in step eight is 1-10°C.

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