JP5920976B2 - Silica particles and method for producing the same, resin composition for semiconductor encapsulation and method for producing the same - Google Patents

Description

  The present invention relates to silica particles and a method for producing the same, a resin composition for encapsulating a semiconductor, and a method for producing the same, and more particularly to a production method capable of producing silica particles having a small particle size and high purity.

  Conventionally, a resin composition in which silica particles are contained in a resin such as a thermosetting resin is known. By including and dispersing silica particles in the resin, the heat resistance of the resin composition can be improved and the physical strength can be improved.

  By the way, the miniaturization of the process of the semiconductor element is progressing year by year. Semiconductor elements can be expected to improve performance by miniaturizing the process, such as improving volume efficiency, reducing power consumption, and improving operating speed.

  Thus, in order to stably improve the performance of the semiconductor element, it is necessary to ensure the thermal stability of the semiconductor. By doing so, the durability of the semiconductor element can be improved. For example, in order to protect the semiconductor element, sealing with a resin composition is performed, but the thermal characteristics and mechanical characteristics of the resin composition directly affect the durability of the semiconductor element.

  A resin composition in which silica particles are dispersed as described above may be adopted as such a resin composition. However, as the process for producing a semiconductor element is miniaturized, the particles of silica particles dispersed in the resin composition are used. It is also required to reduce the diameter. For example, for a semiconductor device processed by a process on the order of several nm to several tens of nm, it is required to similarly employ silica particles having a particle diameter of several nm to several tens of nm.

  Here, as a method for producing silica particles having a particle size of about several nanometers to several tens of nanometers, a method of producing water glass as a raw material (Patent Document 1), a method using alkoxide as a silica precursor as a raw material, etc. It has been known.

  By the way, with the miniaturization and high integration of semiconductor elements, the influence of external α rays and the like is increasing. For example, when a memory element is taken as an example of a semiconductor element, the memory element retains the type of data to be stored depending on the presence or absence of charge accumulation. The type of data changes depending on the amount of electric charge that changes depending on the alpha rays, resulting in unexpected data changes. In addition, since the magnitude of the current flowing through the semiconductor element is also reduced, the current (noise) generated by the α rays is relatively larger than the magnitude of the signal, and there is a risk of malfunction. Therefore, the resin composition for sealing the semiconductor element is also required to have a small α-ray generation amount.

  Conventionally, as a method for producing high-purity silica particles, a method of producing a highly pure silicon compound such as high-purity metallic silicon or silicon tetrachloride and then producing a silica particle from a high-purity silicon compound has been adopted. It had been. For example, it is possible to suitably obtain sub-micrometer to micrometer order silica particles from a method of oxidizing metal silicon to obtain silica particles, and from a method via alkoxide to a nanometer to several tens of nanometer order. Things were obtained favorably.

Japanese Patent No. 3463328

  In the above circumstances, the present inventors evaluated the properties after dispersing nanometer-order silica particles in the resin composition. As a result, it has been found that the physical properties of silica particles having high purity and of nanometer order may not be sufficient.

  The present invention has been devised in order to solve the above-discovered problems, and it is an object to be solved to provide a method for producing silica particles capable of producing silica particles having high purity and high physical properties. To do.

  Conventionally, when trying to obtain silica particles having a volume average particle diameter in the range of 2 nm to 100 nm and reducing the α-ray generation range or reducing the concentration of impurities such as uranium and thorium, After obtaining high purity, a method for obtaining high purity silica by producing alkoxide from high purity metal silicon, silicon silicon produced by producing a silicon compound such as silicon tetrachloride from silicon silicon that is easy to purify. By improving the purity of the compound, silica particles having a high purity were produced by a method of obtaining silica after reducing the amount of α-ray source such as uranium.

According to the diligent research of the present inventors, although silica particles produced from alkoxide can be produced with satisfactory α-ray source amount and particle size, physical properties (typically true density, water glass) In the silica particles produced from the above, it was 2.2 g / cm ³ , and nanosilica synthesized from metal alkoxide has a low density and a lot of porous). For example, when the density is low, it is difficult to exhibit sufficient mechanical properties. However, silica particles produced from water glass have not been freed of α-ray sources such as uranium, and generation of α-rays cannot be avoided. Here, it was difficult to remove α-ray sources such as uranium in the state of water glass.

  However, in the past, there was no requirement to obtain silica particles with a higher true density, even though silica particles with a small particle size and a small amount of α-rays were required. That was not done.

As a result of intensive studies by the present inventors for the purpose of solving this problem, high purity and high physical properties are both achieved by producing silica particles from high-purity metallic silicon once through water glass. The following invention was completed by finding out what can be done.
(1) A silica particle that solves the above problems has a true density of 2.1 g / cm ³ or more, an α-ray generation amount of 0.001 c / cm ² · h or less on the surface of a single particle, and an aluminum content of 50 ppm to 5000 ppm. The volume average particle size is 2 nm to 100 nm.

  In the present specification, the “true density” is a value measured independently for primary particles. That is, even when a void is included in the primary particles, the value is measured together with the void. Specifically, the measurement is performed as follows. After the sample is put in the sample holder with a gas displacement density meter AccupycII (manufactured by Shimadzu Corporation), helium gas is filled, and the true density is calculated from the helium gas filling amount and the sample weight.

In this specification, “α ray generation amount” is a value measured by the following method. The α-ray generation amount was calculated from a value obtained by using a LACS-4000M manufactured by Sumika Chemical Analysis Center as an apparatus, adjusting the measurement area from 1000 cm ² to 4000 cm ² , applying the applied voltage to 1.90 kV, and counting for 99 hours.
(2) Silica particles that solve the above problems have a true density of 2.1 g / cm ³ or more, a thorium content of 30 ppb or less, a uranium content of 1 ppb or less, an aluminum content of 50 ppm to 5000 ppm, and a volume average particle size. It is characterized by being 2 nm to 100 nm.

These (1) and (2) can be added with the components shown in the following (3). (3) The total content of thorium and uranium is 1 ppb or less.
(4) A method for producing silica particles that solves the above problems is a method for producing the silica particles according to any one of the above (1) to (3). And the refinement | purification process which obtains the silicon containing material which is either metal silicon and the silicon compound which reduced the quantity of alpha ray source, and the alkali metal silicate solution which manufactures an alkali metal silicate solution from the said silicon containing material It has a manufacturing process and the aqueous silica sol formation process which forms aqueous silica sol from the obtained alkali metal silicate solution, It is characterized by the above-mentioned.

The manufacturing method disclosed in (4) can add the constituent elements described in the following (5). (5) In the aqueous silica sol forming step, (a) the colloidal silica has a particle size of 4 to 30 nm, a pH of 2 to 9, and an aluminum content of 0 in terms of Al ₂ O ₃ / SiO ₂ molar ratio. A step of adding an alkali aluminate aqueous solution to a silica sol having a ratio of ˜0.0008 so that the Al ₂ O ₃ / SiO ₂ molar ratio exceeds 0.0006 but is 0.004 or less, (b) (A) a step of heating the silica sol obtained in the step at 80 to 250 ° C. for 0.5 to 20 hours, (c) a step of the silica sol obtained in the step (b) above with a cation exchange resin or a cation exchange resin and an anion. A step of producing an acidic silica sol having a pH of 2 to 5 by contacting with an ion exchange resin.
(6) The silica particles that solve the above-described problems can be produced by the production method (4) or (5).
(7) The resin composition for semiconductor sealing which solves the said subject disperse | distributes the silica particle as described in any one of said (1)-(3) and (6), and the said silica particle. And a resin composition.
(8) The manufacturing method of the resin composition for semiconductor sealing which solves the said subject is the process of manufacturing a silica particle with the manufacturing method as described in said (4) or (5), and the obtained silica particle. And a step of dispersing in the resin composition.

  Since the above-mentioned silica particles have a true density in the above-described range, they exhibit high physical properties. Therefore, it is suitable for use in applications (such as a resin composition for semiconductor encapsulation) that require high mechanical properties.

  The silica particles of the present invention and the production method thereof, and the semiconductor sealing resin composition and the production method thereof will be described in detail below based on the embodiments.

(Silica particles)
The silica particles of the present embodiment have a true density of 2.1 g / cm ³ or more, desirably 2.2 g / cm ³ or more. For example, silica particles produced via silane which is a conventional production method show a value of about 1.6 g / cm ³ and can be clearly identified. It is presumed that the silica particles produced via silane have a low true density because the crystal structure is not dense. Here, what can be manufactured with the manufacturing method of the silica particle of this embodiment demonstrated later is one of the silica particles of this embodiment.

The silica particles of this embodiment satisfy at least one of the following (a) and (b). (A) It is desirable that the α ray generation amount on the surface of a single particle is 0.001 c / cm ² · h or less. (B) It is desirable that the thorium content is 30 ppb or less, the uranium content is 1 ppb or less, and particularly the sum of the thorium and uranium contents is 1 ppb or less. That is, it means that the amount of α rays generated is limited. Such a range is a value that can hardly be achieved unless the purity is improved.

  The silica particles of this embodiment have an aluminum content of 50 ppm to 5000 ppm. By making the aluminum content within this range, the silica surface is activated and the surface treatment is facilitated.

  As desirable lower limits of the aluminum content, 500 ppm, 100 ppm and 50 ppm can be exemplified, and as desirable upper limits, 1000 ppm, 3000 ppm and 5000 ppm can be exemplified. Aluminum may be included in any way, but is expected to be included in the form of alumina. In addition, aluminum is contained in silica particles together with silica in primary particles, and secondary particles in which primary particles of alumina are combined with primary particles of silica particles (aluminum content outside the above range). It does not exist as.

  The silica particles of this embodiment have a volume average particle size of 2 nm to 100 nm. The volume average particle size is measured by a laser scattering method. The preferred lower limit for the volume average particle diameter is 5 nm or 10 nm, and the preferred upper limit is 50 nm or 100 nm.

The silica particles of the present embodiment preferably have a sphericity of 0.9 or more, and more preferably 0.95 or more. The sphericity is measured by taking a photograph with an SEM, and calculating from (Sphericality) = {4π × (Area) ÷ (Ambient Length) ² } from the area and circumference of the observed particle. calculate. The closer to 1, the closer to a true sphere. Specifically, an average value measured for 100 particles randomly extracted using an image processing apparatus (Sysmex Corporation: FPIA-3000) is employed.

(Method for producing silica particles)
The manufacturing method of the silica particle of this embodiment is a method of manufacturing the silica particle of this embodiment mentioned above. This production method includes a purification step, an alkali metal silicate solution production step, and an aqueous silica sol formation step.

  The purification step is a step of reducing the amount of α-ray source in the silicon-containing material (metal silicon, silicon compound) as a raw material. In this specification, “α-ray source” refers to an element that emits α-rays, and the degree of reduction is such that the silica particles of the above-described embodiment can be produced. The reduction method is not particularly limited. For example, a method using a silicon compound that is easy to purify, a zone melting method, a method of depositing a single crystal, and the like can be mentioned. Further, these methods can be performed a plurality of times or combined.

  The alkali metal silicate solution manufacturing process is a process of manufacturing an alkali metal silicate solution from a silicon-containing material. Although it does not specifically limit as an alkali metal, Sodium is preferable. As the aqueous sodium salt solution of metal silicate, a so-called water glass can be generally used. Metallic silicon can be dissolved directly in a solution containing an alkali metal, or can be dissolved after reacting metallic silicon with oxygen to form silica. In particular, the use of amorphous silica can improve the solubility. Even crystalline silica can be used by improving the solubility by making it amorphous for the purpose of improving the solubility. As a method for obtaining silica by reacting metallic silicon and oxygen, a method called deflagration method (VMC method) can be adopted. The VMC method has a large specific surface area (particulate) and can obtain amorphous silica. In the VMC method, a chemical flame is formed by a burner in an atmosphere containing oxygen, and metal silicon powder is introduced into the chemical flame in such an amount that a dust cloud is formed, and deflagration is caused to obtain spherical oxide particles. Is the method. When preparing the aluminum content, control the aluminum content with respect to the silicon-containing material in the above-described purification process, or adjust the aluminum content in the alkali metal silicate solution in this step. To do.

  The aqueous silica sol forming step is a step of forming an aqueous silica sol from the obtained alkali metal silicate solution (including the alkaline silica sol). Colloidal silica is formed by adding acid to the alkali metal silicate solution. For example, the pH is preferably 2-9. PH 4-7 is particularly preferable. This silica sol having a pH of 4 to 7 is obtained by treating an alkali metal silicate solution with a cation exchange resin or a cation exchange resin and an anion exchange resin to produce an acidic silica sol having a pH of 2 to 5, followed by an alkali metal hydroxide aqueous solution. It can be produced by adding a base such as aqueous ammonia, amine, aqueous quaternary ammonium hydroxide and adjusting the pH to 4-7. This sol is preferably used immediately after production (for example, step (a). Step (b) and step (c) described below are applied after step (a)).

Here, the SiO ₂ concentration contained in the alkali metal silicate solution is not particularly limited, but is preferably 5 to 50% by mass. The particle size of the produced colloidal silica can be exemplified as 4 to 30 nm in terms of the converted particle size from the specific surface area by the BET method or the specific surface area by the Sears method. The Sears method is a particle converted from a specific surface area by titration with sodium hydroxide as described in ANALYTIC CHEMISTRY Vol. 28 No. 12 (December 1956) p. 1981. This is a diameter measurement method.

As the aqueous aluminate solution used in the step (a), an aqueous solution of sodium aluminate, potassium aluminate, quaternary ammonium aluminate, guanidine aluminate or the like can be used, but aluminate commercially available as an industrial chemical. An aqueous sodium solution is particularly preferred. The Na ₂ O / Al ₂ O ₃ molar ratio of the aqueous sodium aluminate solution is preferably 1.2 to 2.0.

In the step (a), the addition of the aqueous alkali aluminate solution to the silica sol having a pH of 2 to 9 can be performed at 0 to 80 ° C., preferably 5 to 60 ° C. with stirring. Stirring can be performed by a Satake type, a Faudler type, a Disper type stirrer, a homomixer, or the like, but a stronger stirring speed is preferred. The alkali aluminate aqueous solution to be added is preferably used at an Al ₂ O ₃ concentration of 0.5 to 10% by weight. Although the addition time of the alkali aluminate aqueous solution may be long, it is usually within 10 minutes.

In step (a), the amount of alkali aluminate aqueous solution (for example, sodium aluminate aqueous solution) added to the silica sol exceeds 0.0006 in terms of the Al ₂ O ₃ / SiO ₂ molar ratio of the silica sol after the addition, but is 0.004 or less. Is preferred. In particular, it exceeds 0.0008 but is preferably 0.004 or less. The silica sol obtained in the step (a) has a pH of 5 to 11. More preferred is pH 6-10.

  (B) A process is a process of heat-processing the silica sol obtained at the (a) process, and heating temperature is 80-250 degreeC, Especially 100-200 degreeC is preferable. The heating time is preferably 0.5 to 20 hours. For the heating in the step (b), a SUS or glass device and a pressure device can be used.

  The contact between the cation exchange resin or the cation exchange resin and the anion exchange resin in the step (c) can be used at 0 to 60 ° C, and 5 to 50 ° C is particularly preferable. The cation exchange resin is preferably a hydrogen-type strongly acidic cation exchange resin, and is easily obtained as a commercial industrial product. As an example, the trade name Amberlite IR-120B can be mentioned. As the anion exchange resin, a hydroxyl type strongly basic anion exchange resin is preferable, and it is easily obtained as a commercial industrial product. An example of this is the trade name Amberlite IRA-410.

  In the step (c), the contact between the silica sol and the ion exchange resin can be preferably carried out by passing the silica sol through a column filled with the ion exchange resin, and the speed of passing the silica sol through the column is the space per hour. A speed of about 1 to 10 is preferable. In the contact of the silica sol with the cation exchange resin and the anion exchange resin in the step (c), it is preferable that the silica sol is first contacted with the cation exchange resin and then contacted with the anion exchange resin. More preferably, it is brought into contact with a resin.

In the step (c), the silica sol obtained in the step (b) can be passed through without dilution, and the SiO ₂ concentration can be passed as it is, but when diluted and passed, or obtained by the step (c). If the SiO ₂ concentration of the silica sol was decreased, it can increase the SiO ₂ concentration by concentration by a method such as a method using a vaporization method or microporous membrane.

  The pH of the acidic silica sol obtained by the step (c) is 2-5. The particle size of the silica sol in each step of (a), (b) and (c) can be determined as a specific particle size from the specific surface area by the BET method or the specific surface area by the Sears method.

(Resin composition for semiconductor encapsulation)
The resin composition for semiconductor encapsulation of this embodiment is a mixture of the above-described silica particles and a resin composition. The mixing ratio of the silica particles and the resin composition is not particularly limited, but the larger the amount of silica particles, the better the thermal stability.

  The resin composition is a composition that can be cured under some conditions. For example, a mixture of a prepolymer and a curing agent. The curing agent may be mixed immediately before the coin. The type of the resin composition is not particularly limited. For example, it is desirable to have an epoxy group, oxetane group, hydroxyl group, blocked isocyanate group, amino group, half ester group, amic group, carboxy group and carbon-carbon double bond group in the chemical structure. These functional groups are functional groups (polymerizable functional groups) that can be bonded to each other by setting suitable reaction conditions, and the resin composition can be cured by selecting appropriate reaction conditions. Suitable reaction conditions for curing include simple heating and light irradiation, generation of reactive species such as radicals and ions (anions and cations) by heat and light irradiation, and bonding between these functional groups. For example, adding a reaction initiator (polymerization initiator) to perform heating or light irradiation. A compound necessary for the polymerization reaction can be added as a curing agent, or a catalyst for the reaction can be added.

  Preferred examples of the resin composition include a monomer that forms a polymer material by polymerization and a polymer material modified with a polymerizable functional group as described above. For example, a prepolymer such as an epoxy resin, an acrylic resin, or a urethane resin before curing is suitable. In particular, when the thermal stability is high, it is desirable that the composition is composed mainly of an epoxy resin.

The silica particles of the present invention and the production method thereof will be described in detail based on examples.
(Test Example 1)
-Purification process and alkali metal silicate solution manufacturing process: Preparation of water glass of high purity (low thorium, low uranium) After dissolving 30 parts by mass of sodium hydroxide in 75 parts by mass of water, Admafine 25H / 75C (volume 45 parts by mass (average particle size 0.5 μm) was added and stirred until dissolved to produce a water glass solution. Admafine 25H / 75C is a silica particle produced by reacting metal silica powder and oxygen. The amount of uranium and thorium used as the raw material metal silicon is less than 1 ppb when the final silica particle is produced. It is generated so that it becomes.
-Aqueous silica sol formation process After adding 0.2 mass% sodium nitrate to the water glass solution mentioned above, pH is adjusted to the range of 4-7 by passing cation exchange resin and anion exchange resin suitably, and pressure reduction Colloidal silica was produced by heating and stirring (90 ° C.) below. Then, 1 mass% sodium aluminate aqueous solution was added and heat-processed. The amount of sodium aluminate aqueous solution added was such that the amount of sodium aluminate relative to colloidal silica (silica sol) was 7000 ppm as alumina. The heating temperature was about 80 ° C., and the heating time was about 3 days.

As a result, silica particles having a volume average particle diameter of 10 nm were obtained. The obtained silica particles had a uranium and thorium content of less than 0.1 ppb, similar to Admafine 25H / 75C used as a raw material. The specific gravity was 2.2 g / cm ³ .

(Test Example 2)
The same method as in Test Example 1 except that after adjusting the pH by passing an ion exchange resin, the temperature of heating and stirring under reduced pressure was increased from 90 ° C. to 95 ° C. to obtain silica particles having a volume average particle size of 50 nm. Manufactured with. The obtained silica particles had a uranium and thorium content of less than 0.1 ppb, similar to Admafine 25H / 75C used as a raw material. The specific gravity was 2.2 g / cm3.

(Test Example 3: Silica particles produced from commercially available water glass)
Silica particles were produced in the same manner as in Test Example 1 except that a commercially available water glass (sodium silicate No. 3 manufactured by Fuji Chemical Co., Ltd.) was used. The physical properties of the obtained silica particles are as follows. Volume average particle size is about 10 nm, α-ray: less than 0.03 c / cm ² h, specific gravity 2.2 g / cm ³ , thorium content: 150 ppb, uranium content: 4 ppb The α dose, thorium content, and uranium content were all outside the scope of the present invention.

Claims (7)

True density is 2. 2 g / cm ³ or more,
Α-ray generation amount on the surface of a single particle is 0.001 c / cm ² · h or less,
Aluminum content from 50ppm to 5000ppm,
The volume average particle size is from 2 nm to 100 nm,
Silica particles characterized by that. True density is 2. 2 g / cm ³ or more,
Thorium content is 30 ppb or less, uranium content is 1 ppb or less,
Aluminum content from 50ppm to 5000ppm,
The volume average particle size is from 2 nm to 100 nm,
Silica particles characterized by that.   The silica particles according to claim 1 or 2, wherein the total content of thorium and uranium is 1 ppb or less. A method for producing silica particles according to any one of claims 1 to 3,
a purification step of obtaining a silicon-containing material that is either metal silicon or a silicon compound with a reduced amount of α-ray source;
An alkali metal silicate solution production process for producing an alkali metal silicate solution from the silicon-containing material,
An aqueous silica sol forming step of forming an aqueous silica sol from the obtained alkali metal silicate solution;
The manufacturing method of the silica particle characterized by having. The aqueous silica sol forming step includes
(A) A silica sol having a colloidal silica particle diameter of 4 to 30 nm, a pH of 2 to 9, and an aluminum content of Al ₂ O ₃ / SiO ₂ molar ratio of 0 to 0.0008 Adding an alkali aluminate aqueous solution so that the Al ₂ O ₃ / SiO ₂ molar ratio exceeds 0.0006 but is 0.004 or less,
(B) a step of heating the silica sol obtained by the step (a) at 80 to 250 ° C. for 0.5 to 20 hours,
(C) A step of producing an acidic silica sol having a pH of 2 to 5 by contacting the silica sol obtained in the step (b) with a cation exchange resin or a cation exchange resin and an anion exchange resin,
The method for producing silica particles according to claim 4, wherein: The silica particles according to any one of claims 1 to 3 ,
A resin composition in which the silica particles are dispersed;
The resin composition for semiconductor sealing characterized by having. A method for producing a semiconductor sealing resin composition according to claim 6, comprising:
A step of producing silica particles by the production method according to claim 4 or 5,
A step of dispersing the obtained silica particles in a resin composition;
The manufacturing method of the resin composition for semiconductor sealing which has this.