RU2215820C2 - Method of microwave-plasma-enhanced deposition of dielectric films on metallic surfaces with small radius of curvature - Google Patents

Abstract

FIELD: plasma technology. SUBSTANCE: invention, in particular, relates to deposition of dielectric films with crystalline phase inclusions and can find use when manufacturing different tools, in particular for medical application. Method involves synthesis in crossed streams of plasma-forming and silicon-containing gases on a surface being treated preheated to 80-200 C by IR radiation or near the surface. IR radiation is oriented against plasma stream and the surface is arranged in parallel to radiation and rotated round its longitudinal axis. Heated surface is preliminarily insulated from installation body, affected by crystalline material stream, and positive relative plasma constant electric potential is introduced. EFFECT: enabled formation of thickness-uniform dielectric coatings with crystalline inclusions on small-curvature radius metallic tools. 3 ex

Description

 The invention relates to the field of deposition of dielectric films with inclusions of the crystalline phase on metal surfaces, which can be used in various sectors of the economy as a processing surface. For example, in medicine, when removing calcium cholesterol deposits on the inner surfaces of blood vessels using a flexible drill, less solid than crystalline inclusions in the film; crystalline or amorphous surfaces, volumes, deposits, etc.

A known method of microwave plasma deposition of a dielectric film of silicon nitride in crossed gas flows of plasma and silicon-containing gas (SiH ₄ and N ₂ ) on the surface of a semiconductor material (Dzioba. S., Meikle. S., Streater RW, J. Electrochem. Soc. ( USA), oct. 1987, vol. 134, 10, 603-2599). The substrate is heated using the contact resistive method to a temperature of 250-400 ^o C.

 However, this method does not allow to obtain coatings on metal surfaces with a small radius of curvature, because it is impossible to evenly heat the surface to be treated.

A known adopted as a prototype method of microwave plasma deposition of dielectric films on metal surfaces with a small radius of curvature (RU, patent, 2117070, C 23 C 14 / 06.10.08.98). The method includes synthesis in crossed streams of plasma-forming and silicon-containing gases near (or on) heated by infrared radiation to a temperature of 80-200 ^o With the treated surface. In this case, the IR radiation is directed towards the plasma flow, and the surface is perpendicular to the plasma flow and rotate around its longitudinal axis.

This method allows you to apply "smooth" dielectric films on metal surfaces with a small radius of curvature, but does not allow you to apply films with inclusions of the crystalline phase (for example, silica SiO ₂ ) due to the fact that the crystals simply can not be held on a metal surface with a small radius of curvature.

The present invention solves the problem of creating a surface-treating metal tool with a small radius of curvature having a uniformly thick dielectric coating of Si ₃ N ₄ or SiO ₂ with crystalline inclusions.

The problem is achieved in that in the known method of microwave plasma deposition of dielectric films on metal surfaces with a small radius of curvature, including the synthesis in crossed flows of plasma-forming and silicon-containing gases near (or) heated by infrared radiation to a temperature of 80-200 ^o With the treated surface moreover, the infrared radiation is directed towards the plasma flow, and the surface to be treated is perpendicular to it and rotated around its longitudinal axis, the new is that the heated rhnost previously isolated from the installation housing it is further directed to crystalline material stream and fed plasma relative positive constant electric potential.

 The potential value is determined by the granulometric composition of the crystalline phase. The larger the size of the crystals, the greater the potential must be supplied.

 The application of sufficiently thick (3 μm) coatings with inclusions of the crystalline phase up to 20 μm on “developed” surfaces and their long-term preservation over time suggests that internal stresses are insignificant or even absent due to their relaxation in the indicated temperature conditions during deposition.

During the deposition of an amorphous dielectric film into the plasma (nitrogen N ₂ or oxygen O ₂ ) the crystalline phase, we charge it (each crystal) negatively. This is explained by the fact that any solid body placed in a plasma is negatively charged due to the fact that plasma electrons have mobility higher than plasma ions. This is what is called the "floating" plasma potential. Thus, we have a positively charged surface on which it is necessary to deposit a film and a negatively charged crystalline phase, which are electrostatically attracted to each other and held on the surface due to the electrostatic field, since the charge from the surface of dielectric single crystals does not drain well, and this time is quite it is enough that the formed amorphous phase “sticks” the crystal to the surface with its subsequent overgrowing. Thus, dielectric films with inclusions of the crystalline phase are deposited on a surface with a small radius of curvature.

Example 1
The process of deposition of silicon nitride (Si ₃ N ₄ ) on metal surfaces with a small radius of curvature (r ~ 0.1 μm, needles) was carried out. Nitrogen (N ₂ ) was used as the plasma-forming gas. A 5% solution of monosilane (SiH ₄ ) in argon (Ar) was used as a silicon-containing gas. Silicon-containing gas was supplied directly to the deposition facility. The needle was heated by infrared radiation to a temperature of 80 ^o C, and the flow of infrared radiation was directed towards the plasma stream. At the beginning of the deposition of an amorphous Si ₃ N ₄ film, a crystalline phase — a quartz (SiO ₂ ) fraction of 0.1–1 μm was fed into the plasma. Moreover, the mechanisms that ensure the rotation of the object around its longitudinal axis were isolated from the installation casing. The value of the positive displacement relative to the plasma on the deposited metal surface (cylindrical surface with a radius of 0.05 mm) was 3 V.

The deposition time was 20 minutes. The magnitude of the microwave power supplied to the plasma was 600 watts. The working pressure in the chamber was 2 • 10 ^-3 Torr.

 The resulting film with inclusions of single crystals uniformly covered the entire surface of the metal, including the tip, was dense, without pores at the points of contact of the single crystal with the metal. Formed a kind of "ruff", covered with an amorphous phase. In the film, inclusions of single crystals less than 1 μm predominated (although individual crystals with sizes of 1 μm were detected).

Example 2
The process of deposition of silicon nitride (Si ₃ N4) on metal surfaces with a small radius of curvature (r ~ 0.05 mm) - a flexible shaft. Nitrogen (N ₂ ) was used as the plasma-forming gas. A 5% solution of monosilane (SiH ₄ ) in argon (Ar) was used as a silicon-containing gas. Silicon-containing gas was supplied directly to the deposition object. A flexible shaft (a spiral of wire r ~ 0.05 mm) was heated by infrared radiation to a temperature of 200 ^o C, and the infrared radiation flux was directed towards the plasma flow. The flexible shaft was perpendicular to the plasma flow and rotated around its own axis. The deposition time was 20 minutes. The flexible shaft and the mechanisms ensuring its rotation around its longitudinal axis were isolated from the installation casing. At the beginning of the deposition of an amorphous Si ₃ N ₄ film, a crystalline phase — a quartz (SiO ₂ ) fraction of 0.1–20 μm was fed into the plasma. The magnitude of the microwave power supplied to the plasma was 600 watts. The working pressure in the chamber was 2 • 10 ^-3 Torr. The positive bias relative to the plasma on the deposited metal surface was 10 V. The resulting film of 3 μm thickness with inclusions of single crystals uniformly covered the entire outer surface of the flexible shaft, was dense, without pores at the points of contact of the single crystals with the metal. In the film (a "ruff" of single crystals coated with an amorphous phase), inclusions of single crystals 0.1–10 μm in size prevailed (and individual crystals with a size of ~ 20 μm).

 Example 3

The process of deposition of silicon dioxide (SiO ₂ ) on metal surfaces with a small radius of curvature (r ~ 0.05 mm) was carried out. As a plasma-forming gas, oxygen (O ₂ ) was used. A 5% solution of monosilane (SiH ₄ ) in argon (Ar) was used as a silicon-containing gas. Silicon-containing gas was supplied directly to the deposition object. The flexible shaft (wire spiral r ~ 0.05 mm) was heated by infrared radiation to a temperature of 190 ^o C, and the infrared radiation flux was directed towards the plasma flow. The flexible shaft was perpendicular to the plasma flow and rotated around its own axis. The deposition time was 36 minutes. The magnitude of the microwave power supplied to the plasma was 800 watts. The working pressure in the chamber was 5 • 10 ^-3 Topr. At the beginning of the deposition of an amorphous film of silicon dioxide (SiO ₂ ), a crystalline phase was fed into the plasma — quartz (SiO ₂ ) fractions of 0.1-30 μm. The magnitude of the positive displacement relative to the plasma on the deposited metal surface was 15V. The resulting film with a thickness of 1.8 μm with inclusions of single crystals uniformly covered the entire external surface of the flexible shaft, was dense, without pores at the points of contact of the single crystals with the metal. In the film (a "ruff" of single crystals coated with an amorphous phase) inclusions of single crystals 0.1–20 μm in size prevailed (and individual crystals with a size of ~ 30 μm).

Claims (1)

The method of microwave plasma deposition of dielectric films on metal surfaces with a small radius of curvature, including the synthesis in crossed streams of plasma-forming and silicon-containing gases near or on a heated infrared radiation to a temperature of 80-200 ^o With the treated surface, while the IR radiation is directed towards the plasma stream and the surface to be machined is perpendicular to it and rotated around its longitudinal axis, characterized in that the heated surface is previously isolated from the installation body , during the deposition process, an additional stream of crystalline material is fed to it, which is supplied to the plasma, and a constant electric potential positive with respect to the plasma is supplied.