JP2879092B1 - Evaluation method of wettability of metal melt using microgravity environment - Google Patents

Abstract

A method for evaluating the wettability of a metal melt without measuring a contact angle and a surface tension is provided. SOLUTION: The shape of the same metal melt left standing on a substrate under normal gravity and microgravity is measured, and the shape of the metal melt under normal gravity and the shape under microgravity are measured. The wettability is measured from the change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for evaluating the wettability of a metal melt using a microgravity environment. More specifically, the present invention relates to a method for evaluating wettability from a change in the shape of the same metal melt under ordinary gravity and microgravity.

[0002]

2. Description of the Related Art In refining metals, manufacturing semiconductor single crystals, joining substrates to substrates by soldering, etc., it is necessary to grasp the wettability between the metal melt and the container or substrate in order to improve the efficiency of the manufacturing process and the wetting. It is important in solving the resulting engineering problem.
Analysis of physical phenomena such as the flow of high-temperature melt and heat transfer by computer simulation using a supercomputer in recent years is extremely important in understanding and improving the processes of crystal growth and metal solidification of semiconductor materials. It has become an effective means. However, in these simulations, it is essential that various precise thermophysical properties of the metal melt are clarified.

As an intuitive numerical value representing the wettability of a metal melt, an angle formed between the metal melt and a substrate, that is, a contact angle is used, but it is useful for comparing the wettability of various systems. As a general numerical value, the amount of reduction in surface free energy upon wetting, that is, the work required to retract or separate the contact interface between the substrate and the metal melt by a unit area is used. Let the surface tension of solid and liquid be γ
s, γL, assuming that the interfacial tension between the liquid and the solid is γsL, the work corresponding to the wetting when the metal melt is in contact with the substrate in the form of drops is called adhesion work (Wa), Wa = γs + γL−γsL (1) According to Young's equation, the relationship of γsL−γs + γLcosθ = 0 holds between γs, γL, γsL and the contact angle (θ), so from the equations (1) and (2), Wa = γL ( 1 + cos θ) (3), and the adhesion work can be obtained by measuring the values of the surface tension γL of the liquid and the contact angle θ. [For example, "Surface tension", first edition (1980), p. 76 (Kyoritsu Shuppan Co., Ltd.)].

In general, methods for measuring the surface tension of a liquid include a capillary rising method obtained from a height at which a metal melt rises in a capillary, a static drop method obtained from a droplet shape of the metal melt placed on a substrate, and an electromagnetic method. There is a droplet vibration method obtained from the frequency of a floating metal droplet. In most cases, the contact angle is measured by a static drop method that measures the angle of a droplet resting on a solid surface [for example, “Surface tension”, first edition (1980), 57 pages (Kyoritsu Shuppan Co., Ltd.); Kusuhiro Mukai, "Ceramics", 10, P558
(1975)].

[0005] The measurement of the surface tension and contact angle of a metal melt is as follows.
In most cases, the measurement is performed by the static droplet method because of limitations in measurement technology such as the necessity of adjusting the measurement atmosphere at a high temperature. The contact angle is treated as if it were a physical constant determined by the combination of solid and liquid.
It changes greatly depending on the fine surface roughness. The contact angle (advance contact angle: θa) formed at the portion where the liquid droplet advances is large, and the contact angle formed at the receding portion (retreat contact angle: θ)
It is often observed that r) is small, and the contact angle can take any angle between these, depending on the conditions. In addition, the surface tension of the metal melt often varies greatly depending on the operator due to factors such as the need for correction during calculation and the susceptibility to impurity oxygen entering from the substrate and the furnace tube during measurement. Occurs. therefore,
The adhesion work required by the combination of the surface tension and the contact angle will include greater variations.

[0006]

An object of the present invention is to provide a method for evaluating the wettability of a metal melt without measuring the contact angle and the surface tension.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, while measuring the shape of the same metal melt left standing on the substrate under normal gravity and microgravity, the shape of the metal melt under normal gravity and microgravity And measuring the wettability from the change in the shape of the metal melt.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The method for evaluating the wettability of a metal melt according to the present invention determines the work of adhesion from the change in the shape of the same metal melt placed on a substrate under ordinary gravity and microgravity. Things. FIG. 1 schematically shows the shape of a metal melt placed on a substrate under ordinary gravity and microgravity. Under normal gravity, the metal melt has a shape close to an ellipse, but under microgravity, it has a shape close to a sphere. At this time, the contact point between the metal melt and the substrate moves, and the interface area between the metal melt and the substrate decreases.
The work that has been lost when reducing the interfacial area is adhesion work, which corresponds to the loss of potential energy when the metal melt changes from normal gravity to microgravity. The contribution of the substrate to the potential energy of the metal melt under normal gravity differs depending on the position of the metal melt. Pa in FIG.
The part of rt1 is a part that does not move under ordinary gravity and microgravity. The part of Part 2 in FIG. 1 is a part that is held by the substrate under normal gravity and separates from the substrate due to loss of potential energy under microgravity. The part of Part 3 in FIG. 1 is a part that is held in space under normal gravity by balancing with surface tension, and moves under the elimination of potential energy under microgravity. The part at Part 1 in FIG. 1 does not move regardless of the change in potential energy, and therefore does not contribute to the reduction of the interface area. The part of Part 3 in FIG. 1 is held in space by the balance between gravity and surface tension under normal gravity, and therefore does not contribute to the reduction of the interface area. Thus, the disappearance of the potential energy at the part of Part 2 in FIG. 1 reduces the boundary area. The work of adhesion can be determined by dividing the loss of potential energy at this site by the reduced interface area.

In the present invention, the metal melt can have any temperature equal to or higher than the melting point. A combination of various metal melts and a substrate is possible, and the metal is preferably a metal that can be handled in a solid state such as indium, tin, and germanium. The substrate is preferably a quartz glass or a mirror surface. It is a smooth substrate such as a polished metal or ceramic plate.

In the present invention, in order to observe the shape of the droplet of the metal melt, a container having a viewing window capable of controlling the measurement atmosphere and heating the sample is required. The measurement atmosphere is
Vacuum or an atmospheric gas such as nitrogen gas or argon gas can be used, and any heating source such as a resistance furnace or an infrared furnace installed outside or inside the container can be used for heating the sample.

In the present invention, any image recording device such as a camera or a video camera can be used as long as it can accurately record the droplet shape of the metal melt placed on the substrate.

In the present invention, the microgravity environment is not limited by the microgravity level and the microgravity time as long as the deformation of the metal melt under normal gravity reaches equilibrium. Preferably, the microgravity level is 10 ^-2 g or less and the microgravity time is 1 second or more.

[0013]

Next, the present invention will be described in more detail with reference to examples. Example (1) Wettability measuring device The wettability measuring device used in this experiment will be described. This apparatus is provided with two Pyrex viewing windows with a diameter of 40 mm on a straight line, with an inner diameter of 150 mm and an outer diameter of 160 m.
A stainless steel chamber having a height of 250 mm and a height of 250 mm. The chamber includes a terminal for supplying power to the electric furnace, a port for introducing a sheath thermocouple, and a port for introducing and discharging an atmospheric gas which also serves as a connection port for a vacuum device. The chamber is 10 ^-3 Torr
The following vacuum atmosphere can be used.

The electric furnace has an inner diameter of 22 mm, an outer diameter of 25 mm,
It has a structure in which a mullite tube having a length of 110 mm and seven turns of a cartane wire having a diameter of 1 mm are installed horizontally in a chamber. The cartane wire is connected to an AC voltage regulator outside the chamber via a copper wire.

The substrate used for evaluating the wettability is set horizontally at the center of the mullite tube. The substrate is fixed in a mullite tube with a silver paste to prevent movement during measurement. The mass of metal is placed on the substrate in the mullite tube.

The shape of the metal melt on the substrate is recorded by continuous shooting with a still camera or video camera installed on one side of the viewing window. The metal melt is illuminated with a light from the other viewing window to make the contour of the metal melt clear.

(2) Measurement of Wettability of Metal Melt Next, the procedure for measuring the wettability of the metal melt performed in this embodiment will be described. The substrate was placed horizontally at the center of the mullite tube in the chamber, and a columnar mass of 50 to 300 mg of indium metal was placed on the substrate. Silica glass (length 10 mm, width 10 mm, thickness 1 mm) was used for the substrate. Next, the inside of the chamber is set to 10 ⁻³ Torr.
And evacuated to atmospheric pressure with argon gas. The ribbon heater and the electric furnace wound around the chamber are energized, and argon gas of about 100 ml / min is passed through the chamber in a state where the temperature around the indium metal does not exceed 120 ° C. Moisture and the like attached to were removed.

Thereafter, in order to prevent the movement of the indium metal during the experimental operation such as the movement of the apparatus, the indium metal was heated to a melting point (157 ° C.) or higher and then cooled, so that the indium metal was adhered to the substrate. The flow of the argon gas was stopped, the wettability measuring device was installed in a rack, and the measurement was performed at a facility capable of performing a microgravity experiment. Facilities capable of microgravity experiments include a 490 m drop shaft (gravity level: 10 ^-4 g, time: 10 seconds) at the underground gravity-free experiment center in Kamisunagawa-cho, Hokkaido or a 10-m fall shaft at the Hokkaido Institute of Technology in Sapporo, Hokkaido. Tower (gravity level: ^10-3 g, time:
(1.37 seconds). After the wettability measuring device was installed in a facility where microgravity experiments were possible, the electric furnace was energized to heat the substrate and indium metal from 400 ° C to 800 ° C. The shape of the molten isodium was recorded before falling (under normal gravity) and during falling (under microgravity), the shape of the melt was measured from the obtained image data, and the wetness was quantitatively evaluated.

[0019] (3) of indium melt from normal gravity of varying weight of the molten indium on the wettability silica glass Part2 of Figure 1 in reduction and normal gravity under interfacial area in the change to microgravity FIG. 2 shows the relationship between the potential energies. A linear relationship was established between them, and the work of adhesion at each temperature could be determined from the slope of the straight line. 400 ° C, 600 ° C, 800 ° C
Are 0.197 J / m ² ,
The values were 0.149 J / m ² and 0.134 J / m ² .

Comparative Example According to the present invention, the work of adhesion at the melting point (157 ° C.) extrapolated from the work of adhesion at 400 ° C., 600 ° C. and 800 ° C. was 0.23 J / m ² . On the other hand, the work of adhesion between single crystal quartz and molten indium at 157 ° C. in a vacuum, which was determined by the conventional static drop method, was 0.208 J / m ² , a value similar to the value of the work of adhesion determined in the present invention [For example,
F. I. Harding and D. R. Rossi
ngton, J.M. Am. Ceram. Soc, 53, P
87 (1970)].

COMPARATIVE EXAMPLE When the weight of indium was changed from 50 mg to 300 mg, the contact angle of molten indium on silica glass under ordinary gravity became smaller as the weight of indium increased. Assuming that the adhesion work of this system is represented by the above-mentioned equation (3), the adhesion work depends on the weight of the metal melt because the surface tension is a value specific to the molten metal.
However, since the work of adhesion is determined by the interaction between the metal melt and the substrate, it is irrelevant to the weight of the molten metal, and this system cannot evaluate the work of adhesion by equation (3).

[0022]

According to the method for evaluating the wettability of the financial melt of the present invention, the work of adhesion can be directly measured without the need to measure the contact angle and surface tension, and the wettability can be quantitatively determined. Can be evaluated.

[Brief description of the drawings]

FIG. 1 is a schematic view of a metal melt under normal gravity and under microgravity. The metal melt is divided into three parts by the contribution of potential energy to the substrate under normal gravity.

FIG. 2 shows the amount of reduction in the area of the indium in the change of the indium on silica glass from normal gravity to microgravity at 400 ° C., 600 ° C., and 800 ° C., and P in FIG.
FIG. 6 is a diagram showing the relationship between the potential energy of art2.

──────────────────────────────────────────────────続 き Continuing from the front page (73) Patent holder 598033077 Masaaki Suzuki 5-9-15 Hiraoka 5-chome, Kiyota-ku, Sapporo-city, Hokkaido (73) Patent holder 598033088 Takeshi Okutani 2-Jo-4-6 Uenopporo, Atsubetsu-ku, Sapporo, Hokkaido No. 10 (74) Attorney Toshiaki Ikeura (5) Attorney Toshiaki Ikeura (72) Inventor Hideaki Nagai 2-2-17-1 Tsukikan Higashi-Jo 2-22, Toyohira-ku, Sapporo, Hokkaido Satozuka 2-3, 3-16, 43 (72) Inventor Takashi Tsurue, 5-1, 1-15-1, Nishioka, Toyohira-ku, Sapporo, Hokkaido, Japan (72) Masaaki Suzuki 5-9-1, Hiraoka, Kiyota-ku, Sapporo, Hokkaido No. 15 (72) Inventor Takeshi Okutani Takeshi Nomura No. 2-6-4-10 Uenopporo, Atsetsu-ku, Sapporo, Hokkaido Examiner Nomura Nomura (58) Field surveyed (Int. Cl. ⁶ , DB name) G01N 13/00-13 / 02 JICST Yl (JOIS)

Claims (1)

(57) [Claims] 1. The method of measuring the shape of the same metal melt placed on a substrate under normal gravity and microgravity, and measuring the shape of the metal melt under normal gravity and the shape under microgravity. A method for evaluating the wettability of a molten metal using a microgravity environment, characterized in that the wettability is measured from the change in temperature.