Thin film formation method

Abstract

This provides a new method for coating inorganic materials into thin films. [Solution] An inorganic thin film 3 is formed on the surface of the workpiece 1 by controlling the surface charge of the inorganic colloidal particles while polishing the surface of the workpiece 1 with inorganic colloidal particles. For example, cationic water 5 containing inorganic colloidal particles and metal cations is supplied to the surface of the workpiece 1, and the surface of the workpiece 1 is polished with a polishing disk 10. This causes the metal cations contained in the cationic water 5 to adsorb to the surface of the inorganic colloidal particles, lowering the surface potential of the inorganic colloidal particles and weakening the repulsive force between the inorganic colloidal particles and the workpiece 1, creating a state in which they are more likely to bond. This allows the inorganic compounds converted from the inorganic colloidal particles to bond to the surface of the workpiece 1, forming a thin film. In this way, an inorganic thin film 3 can be formed on the surface of the workpiece 1 by polishing the workpiece 1.

Description

[Technical Field]

[0001] The present invention relates to a thin film forming method. By law It is related to. [Background technology]

[0002] Traditionally, coatings have been used for a variety of purposes, including protection (such as dust prevention, rust prevention, improved weather resistance, and improved abrasion resistance); design (such as adding gloss, improving color development, and preventing fingerprints); and functionality (such as anti-fouling, anti-static, and heat / insulation). Coating agents can be broadly categorized into organic and inorganic materials. While organic coatings deteriorate quickly and require regular maintenance, inorganic coatings are less susceptible to deterioration and can maintain their performance for long periods of time. For this reason, inorganic coatings are often used in fields that require high durability, such as semiconductors, optical devices, and heat-resistant components.

[0003] Known examples of techniques for coating inorganic materials into thin films include chemical vapor deposition (CVD), physical vapor deposition (PVD), the sol-gel method, plasma spraying, etc. In the field of semiconductors, chemical mechanical polishing (CMP) is known as a technique for planarizing thin films formed by techniques such as CVD (see, for example, Patent Document 1).

[0004] In the polishing method described in Patent Document 1, ionized water generated by electrolysis of pure or ultrapure water and an abrasive containing abrasive particles are supplied to a polishing cloth, and the polishing cloth is used to polish the main surface of a semiconductor wafer having a film formed thereon. Here, if the film to be polished is metal, acidic ionized water is used for polishing, while if the film to be polished is oxide, nitride, polycrystalline silicon, or single-crystal silicon, alkaline ionized water is used for polishing. For example, a SiO2 film is deposited on the semiconductor wafer by the CVD method, and then the SiO2 film is polished by the CMP method using the above-mentioned method to planarize the surface of the semiconductor wafer.

[0005] There is a known paper that describes the formation of an amorphous silica thin film on the surface of Tianshan stone during the polishing process (see, for example, Non-Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 3311203 [Non-patent literature]

[0007] [Non-Patent Document 1] Journal of the Japan Society for Abrasive Technology, Vol. 68, No. 2, pp. 88-89, published August 1, 2024. "Analysis of thin films formed simultaneously on the surface of Tianshan stone during the polishing process using synchrotron radiation" Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a new method for coating inorganic materials into thin films. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, in the present invention, the surface of the workpiece is polished with inorganic colloidal particles, and an inorganic thin film is formed on the surface of the workpiece by controlling the surface charge of the inorganic colloidal particles. [Effects of the Invention]

[0010] The present invention configured as described above can provide a completely new method of coating the surface of an object to be polished with an inorganic material in the form of a thin film by polishing the object. [Brief explanation of the drawings]

[0011] [Figure 1] 1A to 1C are diagrams for explaining a thin film forming method according to an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram illustrating control of surface charge of inorganic colloidal particles by cations. [Figure 3] 1 is a schematic diagram showing a state in which a reaction product and an inorganic thin film are formed on the surface of an object to be polished. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment of the present invention will now be described with reference to the drawings, in which: Figure 1 is a diagram for explaining a thin film forming method according to this embodiment.

[0013] As shown in FIG. 1, in this embodiment, for example, a rotating disc-shaped polishing disk 10 is used to polish the surface of an object 1 (a base material on which a thin film is to be formed) with inorganic colloidal particles at a predetermined pressure, and an inorganic thin film 3 is formed on the surface of the object 1 by controlling the surface charge of the inorganic colloidal particles. The predetermined pressure is, for example, 1 kilopascal (1 kN / m 2 ) or more is sufficient.

[0014] In the example shown in Fig. 1, the surface area of ​​the workpiece 1 is larger than the surface area of ​​the polishing surface of the polishing disc 10. In order to polish an area of ​​the workpiece 1 that is larger than the polishing surface of the polishing disc 10 (which may be the entire surface of the workpiece 1 or a part of it), the workpiece 1 moves horizontally relative to the polishing disc 10, whose horizontal position is fixed. The horizontal movement of the workpiece 1 is performed by a predetermined moving mechanism, the configuration of which is not shown in the figure.

[0015] The object to be polished 1 is an inorganic material. The inorganic material may be a metal or a non-metallic inorganic material. In this embodiment, as an example, the object to be polished 1 is described as being made of iron (Fe). Note that as long as the portion of the object to be polished 1 is made of iron, the other portions may be made of any material.

[0016] The inorganic colloidal particles may be colloidal particles of an inorganic compound. In this embodiment, as an example, the inorganic colloidal particles are described as SiO2 colloidal particles. The inorganic compound in the form of colloidal particles is the raw material of the inorganic thin film 3 formed on the surface of the workpiece 1 to be polished, and when SiO2 colloidal particles are used, the inorganic thin film 3 formed on the surface of the workpiece 1 to be polished is an SiO2 thin film.

[0017] The surface charge of the SiO2 colloid particles is controlled by supplying cations while polishing the workpiece 1 with the SiO2 colloid particles. The cations are, for example, monovalent, divalent, or trivalent metal cations. In this embodiment, as an example, cationic water 5 containing SiO2 colloid particles is supplied to the surface of the workpiece 1, and the surface of the workpiece 1 is polished with a polishing disk 10, thereby polishing the workpiece 1 with the SiO2 colloid particles contained in the cationic water 5 and controlling the surface charge of the SiO2 colloid particles with the metal cations.

[0018] Figure 2 is a diagram for explaining the control of the surface charge of SiO2 colloidal particles by metal cations. Note that Figure 2 is a schematic illustration for explanatory purposes, and the size of each element does not reflect reality. The same applies to Figure 3, which will be explained later.

[0019] As shown in Figure 2, when the surface of the workpiece 1 is polished with SiO2 colloid particles 5a, a reactant 2 is generated on the surface of the workpiece 1 from the oxide on the metal surface and the SiO2 colloid particles 5a. If the workpiece 1 is made of iron, the reactant 2 generated is a compound of iron, silicon, etc. The surface of this reactant 2 is negatively charged. In addition, the surfaces of the SiO2 colloid particles 5a contained in the cationic water 5 are also negatively charged. Therefore, in the absence of metal cations as shown in Figure 2(a), a repulsive force acts between the reactant 2 and the SiO2 colloid particles 5a.

[0020] In contrast, when metal cations 5b are present as shown in Figure 2(b), the SiO2 colloid particles 5a react with the metal cations 5b, and the surface charge of the SiO2 colloid particles 5a becomes very small. In other words, the surface potential of the SiO2 colloid particles 5a is lowered by the adsorption of the metal cations 5b onto the surface of the SiO2 colloid particles 5a. This is what is meant by controlling the surface charge of the SiO2 colloid particles 5a.

[0021] At the same time that the surface charge of the SiO2 colloid particles 5a becomes very small, the surface charge of the reactant 2 also becomes very small due to reaction with the metal cations 5b. Therefore, the repulsive force between the reactant 2 and the SiO2 colloid particles 5a becomes small, and the energy barrier when the SiO2 colloid particles 5a approach the reactant 2 becomes very low. As a result, a van der Waals force (attractive force) is generated between the reactant 2 and the approaching SiO2 colloid particles 5a, and the two are strongly bonded (adhered) to each other.

[0022] The metal cations 5b contained in the cationic water 5 may be monovalent, divalent, or trivalent, and by increasing the concentration of the metal cations 5b contained in the cationic water 5, the control of the surface charge can be more effectively achieved.

[0023] 3 is a schematic diagram showing the state in which an inorganic thin film 3 has been formed on the surface of the workpiece 1 (more precisely, on the surface of the reactant 2; the same applies below). As explained in FIG. 2(b), when the SiO2 colloid particles 5a are bonded to the reactant 2 and pressure is applied by the polishing disc 10, the SiO2 colloid particles 5a are compressed, a dehydration condensation reaction proceeds, and the SiO2 colloid particles 5a are transformed into SiO2 as the water molecules are released, forming an SiO2 thin film 3 on the surface of the reactant 2.

[0024] As described above, by carrying out the thin film forming method of this embodiment, an inorganic thin film-containing laminate is produced, as shown in Fig. 3, on the surface of the object to be polished 1 (for example, a base material at least the surface portion of which is made of Fe), which comprises a reactant 2 (for example, a compound of iron and silicon, etc.) made from the object to be polished 1 and inorganic colloidal particles 5a (for example, SiO2 colloidal particles), and an inorganic thin film 3 (for example, SiO2 thin film) formed on the upper surface thereof. Note that for convenience, the reactant 2 is not shown in Fig. 1.

[0025] As explained in detail above, according to this embodiment, it is possible to provide a completely new method of coating the surface of the object 1 to be polished with an inorganic material in the form of a thin film by polishing the object 1 to be polished.

[0026] In the above embodiment, an example has been described in which cationic water 5 containing inorganic colloidal particles is supplied to the surface of the workpiece 1 and the surface of the workpiece 1 is polished with the polishing disc 10, but this method is not limited to this. For example, a polishing disc 10 may be used in which an abrasive containing SiO2 colloidal particles is disposed on the polishing surface. In this case, the cationic water 5 supplied to the workpiece 1 may contain metal cations, and does not necessarily have to contain inorganic colloidal particles.

[0027] Furthermore, in the above embodiment, SiO2 colloidal particles have been described as an example of inorganic colloidal particles, but as mentioned above, the inorganic colloidal particles are not limited to this. The inorganic colloidal particles may be colloidal particles of an inorganic compound that serves as a raw material for the inorganic thin film 3 to be formed on the surface of the workpiece 1 to be polished. For example, the inorganic colloidal particles may be Al2O3 colloidal particles, Na2O colloidal particles, or CaO colloidal particles. In this case, the inorganic thin film 3 formed on the surface of the workpiece 1 to be polished will be an Al2O3 thin film, a Na2O thin film, or a CaO thin film.

[0028] In the above embodiment, iron material has been described as an example of the object to be polished 1, which is an inorganic material, but as mentioned above, the object to be polished 1 is not limited to this. Here, the object to be polished 1 may contain raw materials for the inorganic thin film 3 to be formed on its surface. For example, if the inorganic thin film 3 to be formed on the surface of the object to be polished 1 is an SiO2 thin film, the object to be polished 1 may be an inorganic material containing components that become raw materials for the SiO2 thin film.

[0029] In this case, SiO2 colloidal particles may be supplied from outside the workpiece 1 as in the above embodiment, but they do not have to be supplied. This is because the SiO2 components contained in the workpiece 1 are released as colloidal particles by polishing the workpiece 1. In this case, the SiO2 colloidal particles generated from the workpiece 1 act as an abrasive to polish the workpiece 1. For example, the surface of the workpiece 1 may be polished while cationic water 5 containing metal cations but no SiO2 colloidal particles is supplied to the workpiece 1.

[0030] In the above embodiment, as an example, the object to be polished 1 is an inorganic material having a flat surface, and the polishing surface of the polishing disk 10 also has a flat surface. However, the present invention is not limited to this. For example, the object to be polished 1 may be an inorganic material having an uneven surface, and by polishing the object to be polished with the polishing disk 10 having a flat polishing surface, the surface of the object to be polished 1 may be planarized and an inorganic thin film 3 may be formed on the planarized surface of the object to be polished 1.

[0031] In the above embodiment, an example has been described in which the workpiece 1 moves horizontally relative to the polishing disc 10, whose horizontal position is fixed, but conversely, the polishing disc 10 may move horizontally relative to the workpiece 1, whose horizontal position is fixed. In this case, the workpiece 1 may be immersed in cationized water 5 contained in a water tank, and the surface of the workpiece 1 may be polished while the polishing disc 10 is moved.

[0032] Furthermore, the above-described embodiments are merely examples of specific embodiments for carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereby. In other words, the present invention can be carried out in various forms without departing from the gist or main characteristics thereof. [Explanation of symbols]

[0033] 1 Object to be polished 2. Reactants 3 Inorganic thin film 5. Cation water 5a Inorganic colloidal particles 5b Metal cations 10 Polishing machine

Claims

1. A thin film forming method comprising: supplying cationic water containing inorganic colloidal particles, either SiO2 colloidal particles, Al2O3 colloidal particles, Na2O colloidal particles or CaO colloidal particles, to the surface of an inorganic material to be polished; polishing the surface of the material to be polished with the inorganic colloidal particles using a polishing disk; reducing the surface charge of the inorganic colloidal particles by causing metal cations to adsorb onto the surfaces of the inorganic colloidal particles, thereby bonding the inorganic colloidal particles to reactants generated on the surface of the material to be polished by the polishing, thereby forming an inorganic thin film, either SiO2 thin film, Al2O3 thin film, Na2O thin film or CaO thin film.

2. A thin film forming method comprising: polishing the surface of an inorganic material workpiece using a polishing disk with an abrasive containing inorganic colloidal particles selected from SiO2 colloidal particles, Al2O3 colloidal particles, Na2O colloidal particles, or CaO colloidal particles; while supplying cationic water to the surface of the workpiece; polishing the workpiece while causing metal cations to be adsorbed onto the surface of the inorganic colloidal particles, thereby reducing the surface charge of the inorganic colloidal particles; and bonding the inorganic colloidal particles to reactants generated on the surface of the workpiece by the polishing, thereby forming an inorganic thin film selected from SiO2 thin film, Al2O3 thin film, Na2O thin film, or CaO thin film.

3. A thin film forming method comprising: supplying cationic water to the surface of an inorganic material to be polished; polishing the surface of the object using a polishing disc with inorganic colloidal particles, either SiO2 colloidal particles, Al2O3 colloidal particles, Na2O colloidal particles or CaO colloidal particles, generated from the object; adsorbing metal cations onto the surfaces of the inorganic colloidal particles to reduce the surface charge of the inorganic colloidal particles; and bonding the inorganic colloidal particles to reactants generated on the surface of the object to be polished by the polishing, thereby forming an inorganic thin film, either SiO2 thin film, Al2O3 thin film, Na2O thin film or CaO thin film.

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