TWI823069B - Gold evaporation materials - Google Patents

Abstract

The gold evaporation material of the present invention is a granular gold evaporation material used in a vacuum evaporation method. It is characterized in that: the average crystal grain size of the gold evaporation material is 0.1mm or more, and the oxygen content is 10wtppm or less. And the hydrogen content is below 5wtppm. The subject of the present invention is to provide a gold evaporation material, which is a granular (bead) gold evaporation material used in a vacuum evaporation method, and can suppress the bumping phenomenon during vacuum evaporation.

Description

Gold evaporation materials

The invention relates to a gold evaporation material used in a vacuum evaporation method.

Vacuum evaporation is one of the film-forming technologies. It is a technology that heats the evaporation material in a vacuum so that the evaporation material becomes gas molecules and adheres to the substrate, thereby forming a thin film. It can be evaporated (film-formed) on glass, plastic, film, metal, etc. The vacuum evaporation method is widely used in the formation of components in electronic parts, semiconductor devices, optical films, magnetic devices, LEDs, organic EL, LCD, etc. As the evaporation material, noble metals such as gold, silver, platinum, and palladium or non-ferrous metals such as copper, aluminum, chromium, and tin can be used. Furthermore, not only metals can be formed into films, but also non-metals such as oxides can be formed into films.

Previously, when evaporation materials were filled into a crucible and melted using electron beams, impurities contained in the evaporation materials volatilized, causing a bumping phenomenon (also called spatter), causing particles to adhere to the substrate. Regarding the problem of this bumping phenomenon, Patent Document 1 describes a method of preventing bumping by reducing impurity elements. Furthermore, Patent Document 2 describes a method of adding additive metal. Furthermore, Patent Document 3 proposes a method of controlling the amount of oxygen on the outermost surface. Prior technical literature patent documents

Patent document 1: Japanese Patent Application Publication No. 1-180961 Patent Document 2: International Publication No. 2017/199873 Patent Document 3: Japanese Patent Application Publication No. 2000-212728

[Problem to be solved by the invention]

The subject of the present invention is to provide a gold evaporation material, which is a granular (bead) gold evaporation material used in a vacuum evaporation method, and can suppress the bumping phenomenon during vacuum evaporation. [Technical means to solve the problem]

One aspect of the present invention that can solve the above problems is a granular gold evaporation material used in a vacuum evaporation method. It is characterized in that the average crystal grain size of the gold evaporation material is 0.1 mm or more, and the oxygen content is is 10 wtppm or less, and the hydrogen content is 5 wtppm or less. Another aspect that can solve the above problem is a granular gold evaporation material used in a vacuum evaporation method, which is characterized in that 1 g of the gold evaporation material contains foreign matter particles of 1 μm or more. The number is less than 5,000. [Effects of the invention]

According to the present invention, the bumping phenomenon can be effectively suppressed when the gold evaporation material is melted, thereby reducing particles adhering to the substrate. Therefore, it can help improve the yield of products.

Regarding the gold evaporation material used in the vacuum evaporation method, gold with a purity of 99.9 wt% or more is usually used as a raw material, and the gold raw material is melted in a ceramic crucible such as alumina or a carbon crucible in the atmosphere. Then, the gold melt is dropped from the nozzle connected to the bottom of the crucible into water or an organic solvent for rapid cooling, thereby producing granular gold evaporation materials (also called gold particles or gold beads). In this way, gold evaporation materials with relatively few impurities can be produced.

However, even when such gold evaporation materials with relatively few impurities are used, there will still be a bumping phenomenon in the early stages of evaporation. The pre-evaporation time will become longer, or the condition settings of the evaporation device must be changed, resulting in The problem of reduced production efficiency. In particular, since gold is relatively expensive as a material, there is a problem that the longer the pre-evaporation time is, the higher the cost will be. In addition, there is also a problem that the device or the crucible is contaminated due to the bumping phenomenon, which increases the frequency of device cleaning.

The inventors of the present invention conducted intensive research on this problem, and as a result obtained the following insights: There is a correlation between the average crystal grain size of the granular gold evaporation material used in the vacuum evaporation method and the oxygen and hydrogen content. By making the average The increase in crystal particle size can reduce the oxygen and hydrogen content, and by reducing the oxygen and hydrogen content, the bumping phenomenon can be suppressed. In addition, the inventors of the present invention conducted intensive research on the above-mentioned problem from another viewpoint, and as a result obtained the following findings: In the process of evaporating the granular gold evaporation material by electron beam melting or the like, foreign matter floats in the melt. The surface covers the melt surface and causes bumping, and by reducing the foreign matter, the bumping phenomenon can be suppressed. Based on these findings, the present invention provides the following embodiments.

An embodiment of the present invention is a granular gold evaporation material used in a vacuum evaporation method, and the average crystal grain size is preferably 0.1 mm or more. More preferably, it is 0.5 mm or more. If the average crystal grain size is too small, the number of crystal grain boundaries will increase, and gas components such as oxygen and hydrogen described below will be easily occluded along the grain boundaries. The absorbed gas components may cause bumping when used as evaporation materials. It is speculated that if there are few crystal grain boundaries, the diffusion rate of gas within the grains will be very slow and it will be difficult to solid dissolve within the grains. Therefore, the larger the average crystal grain size is, the better, and it is preferably 0.1 mm or more. More preferably, it is 0.5 mm or more. Furthermore, the ideal state is single crystal.

The granular gold vapor deposition material according to the embodiment of the present invention preferably has an oxygen content in the gold vapor deposition material of 10 wtppm or less. Oxygen may invade into the evaporated material along the grain boundaries and be absorbed inside. Also, when the gold melt is dropped into water and rapidly cooled, the gold in the melt reacts with the water, and Au+H ₂ O becomes AuO+H ₂ , causing the surface of gold to be covered with an oxide film. Therefore, it is preferable to reduce the oxygen content, and it is preferable to set it to 5 wtppm or less.

The granular gold vapor deposition material according to the embodiment of the present invention preferably has a hydrogen content of 5 wtppm or less in the gold vapor deposition material. As described above, there are cases where the molten gold reacts with water to generate hydrogen, and the generated hydrogen invades along the gold grain boundaries and is absorbed in a supersaturated manner. This hydrogen causes a bumping phenomenon when used as a vapor deposition material, so it is desirably reduced, and is preferably set to 3 wtppm or less.

Furthermore, the gold vapor deposition material of this embodiment is characterized in that the number of foreign matter of 1 μm or more contained in 1 g of the gold vapor deposition material is 5,000 or less. Evaporation materials are produced by atmospheric melting of gold raw materials in a crucible and rapid cooling of the melt. However, oxides such as SiO ₂ , MgO, and Al ₂ O ₃ may be mixed in as dust in the atmosphere. , C (carbon), etc. may be mixed in from the crucible. These remain in the gold melt in the form of foreign matter and cause bumping when used as evaporation materials. If 1 g of gold evaporation material contains less than 5,000 foreign matter of 1 μm or larger, it can be said that the bumping phenomenon can be suppressed to a certain extent. Preferably, the number of foreign matter larger than 1 μm is 1,200 or less.

The vapor deposition material of this embodiment can be produced as follows, for example. Fill the carbon crucible with gold raw material with a purity of 4 N (99.99 wt%) or above and melt it. Then, the melted gold in the crucible is dropped into water from the bottom of the crucible, and the granulated gold is used as the evaporation material (beads). What is important at this time is to add a coagulant such as borax to the gold melt and adjust its amount to absorb foreign matter. Thereby, foreign matter in the melt is concentrated using the coagulant as a starting point. The added borax stays on the liquid surface, so a small amount of gold remains in the nozzle during granulation. Although the amount of residue also depends on the amount of melting, it is preferably 0.1 g to 100 g. In this way, part of the gold containing the coagulant remains, so the gold particles are not contaminated by the coagulant or foreign matter.

The gold melt is dropped from the bottom of the crucible into water for rapid cooling to produce granulated gold. At this time, the crystal particle size or oxygen, Hydrogen content. For example, the longer the falling distance, the more grain boundaries there will be due to polycrystallization due to slow cooling during the falling process. Furthermore, if there are many grain boundaries, hydrogen generated by the reaction of the gold melt and water will easily invade along the grain boundaries and be absorbed in an oversaturated manner. In addition, if the melt temperature is more than 100°C higher than the melting temperature, the content of oxygen or hydrogen will increase. The higher the melt temperature, the greater the content of these gas components.

(Measurement method of average crystal particle size) The granular gold vapor deposition material (bead) is cut at the cross section (the position where the largest area becomes the largest area), and the cross section of the bead is cut and/or ground to reveal the grain boundaries. Then, grinding etc. are performed, and the cross-section is observed using an optical microscope. In order to easily observe the grain boundaries, the magnification of the optical microscope was set to 10 times or 50 times. Then, straight lines were drawn vertically and horizontally so that they passed through the center of the enlarged photograph obtained using an optical microscope, and the number of crystal grains cut by each straight line was counted. Furthermore, the grains at the end of the line segment are counted as 0.5. Then, the length of each vertical and horizontal straight line is divided by the number of crystal grains to determine the average vertical and horizontal crystal grain diameters. In addition, since each bead has a different size or weight, 10 beads are randomly selected and the average value of the 10 beads is taken as the average crystal particle size.

(Measurement method of oxygen and hydrogen content) Analytical device: Horiba Manufacturing Co., Ltd. EMGA-600W Analysis method: Pulse furnace heating and melting in inert gas; Infrared absorption method

(Method for determination of foreign matter) Dissolve the granular gold evaporation material (beads) in aqua regia, evaporate the dissolved residue to dryness, put it into pure water, and use a particle counter based on the light scattering method to measure the number of foreign matter larger than 1 μm. Furthermore, the result of foreign matter analysis is oxides of Si, Al, Mg, etc. or C (carbon). In addition, since each particle of beads has a different particle size or weight, 10 beads are randomly selected, 10 beads are dissolved, the total number of foreign matter is measured, and the number of foreign matter per 1 g is calculated based on the total weight of 10 beads. .

(Evaluation of bumping phenomenon) If a bumping phenomenon occurs when the vapor deposition material is melted by electron beam, the vapor deposition material will adhere to the inside of the vapor deposition device, thereby reducing the weight of the vapor deposition material. Therefore, by measuring the weight loss of the melted vapor deposition material, the bumping phenomenon can be evaluated. Put about 40 g of evaporated material into a copper crucible, conduct electron beam melting under the conditions of vacuum degree of 1×10 ^-1 Pa, electron beam irradiation power of 6 kW, and electron beam irradiation time of 2 minutes, and conduct melting The subsequent weight loss was measured. Furthermore, under these melting conditions, almost no loss due to evaporation occurs. In addition, when the weight reduction rate is less than 0.01 wt%, it is judged as ◎ (very good), when the weight reduction rate is 0.01 to 1 wt%, it is judged as ○ (good), and when the weight reduction rate is 1 wt% or more, it is judged as × (very good). Difference). [Example]

Next, embodiments and the like of the present invention will be described. Furthermore, the following examples are only representative examples, so the present invention is not limited to these examples and should be interpreted within the scope of the technical ideas described in the patent application.

(Sample No. 1~9) Fill 1000 g of gold raw material with a purity of 4 N (99.99 wt%) or above into a carbon crucible, and use a high-frequency induction coil installed on the outer periphery of the crucible to melt the gold raw material. At this time, the melt temperature of each sample was adjusted as shown in Table 1. Furthermore, borax is added as a coagulant to the gold melt. The amounts added to each sample are shown in Table 1. Then, the melted gold in the crucible is dropped into water from the bottom of the crucible to produce granular gold, which is used as a vapor deposition material. At this time, for each sample, the distance from the bottom of the crucible to the water surface and the remaining amount of the gold melt containing the coagulant were adjusted. The above contents are summarized and shown in Table 1.

For the gold evaporation material of each sample obtained, the number of foreign matter larger than 1 μm, average crystal particle size, oxygen content, and hydrogen content were measured using the above measurement method. The results are shown in Table 1. Furthermore, the gold evaporation material of each sample after measurement was put into a copper crucible, irradiated with an electron beam under the above conditions, and melted, and the weight reduction rate after melting was measured. The results are shown in Table 1. It can be seen that if the number of foreign objects larger than 1 μm exceeds 5,000, the weight loss caused by the bumping phenomenon will be relatively large.

[Table 1] Sample number Melt temperature Falling distance Coagulant (borax) Residue amount average crystal particle size oxygen Hydrogen Number of foreign objects above 1 μm Evaluation of bumping phenomenon ℃ cm g g mm wtppm wtppm pieces/g 1 1120 20 10 10 2.1 <1 <1 110 ◎ 2 1000 20 5 1 1 <1 <1 520 ◎ 3 1300 20 5 1 0.5 1 <1 1010 ◎ 4 1300 50 5 0.5 0.3 2 1 3150 ○ 5 1300 50 1 0.5 0.1 5 3 4900 ○ 6 1400 60 1 - 0.07 10 5 5000 ○ 7 1420 70 1 - 0.01 15 6 7000 × 8 1420 120 - - 0.006 20 8 11500 × 9 1500 200 - - 0.002 35 10 21000 × [Industrial availability]

According to the present invention, the bumping phenomenon can be suppressed when the evaporation material is melted, thereby reducing particles adhering to the substrate. The evaporation material of this embodiment can be widely used to form elements in electronic components, semiconductor devices, optical films, magnetic devices, LEDs, organic EL, LCDs, etc. using the vacuum evaporation method.

without

[Fig. 1] is a photograph of a gold evaporation material (bead) according to one aspect of the present invention.

Claims (3)

A gold evaporation material, which is a granular gold evaporation material used in a vacuum evaporation method. It is characterized in that: the average crystal grain size of the gold evaporation material is more than 0.1mm, and the oxygen content is less than 10wtppm. And the hydrogen content is below 5wtppm. For example, the gold evaporation material of claim 1, wherein the oxygen content is 5 wtppm or less. For example, the gold evaporation material of claim 1 or 2, wherein the hydrogen content is 3wtppm or less.