TWI807395B - Gold evaporation material - Google Patents

Abstract

A gold evaporation material, which is a gold evaporation material used in a vacuum evaporation method, is characterized in that: the surface roughness Ra is 10 μm or less, and the number of microcracks with an area circle equivalent diameter of 0.1 mm or more is 1 piece/g or less. An object of the present invention is to provide a gold vapor deposition material used in a vacuum vapor deposition method, which can suppress a bumping phenomenon (splash phenomenon) during vacuum vapor deposition.

Description

Gold evaporation material

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 that becomes gas molecules adheres to the substrate, thereby forming a thin film. Evaporation (film formation) can be carried out 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 ELs, LCDs, etc. As the vapor deposition material, precious 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 but also non-metals such as oxides can be formed into films.

Conventionally, when the vapor deposition material is filled into a crucible and melted using an electron beam or the like, impurities contained in the vapor deposition material volatilize to cause a bumping phenomenon (also called splash) and particles adhere to the substrate. Regarding the problem of this bumping phenomenon, Patent Document 1 describes reducing impurity elements to prevent bumping. In addition, Patent Document 2 describes a method of adding an additive metal. Furthermore, Patent Document 3 proposes a method of controlling the amount of oxygen on the outermost surface. [Prior Art Literature] [Patent Document]

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

[Problem to be Solved by the Invention]

The object of the present invention is to provide a gold vapor deposition material used in a vacuum vapor deposition method, which can suppress the bumping phenomenon during vacuum vapor deposition. [Means to solve the problem]

An aspect of the present invention that can solve the above-mentioned problems is a gold evaporation material used in a vacuum evaporation method, characterized in that the surface roughness Ra is 10 μm or less, and the number of microcracks with an area circle equivalent diameter of 1 mm or more is 1 piece/g or less. [Effect of Invention]

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

The gold evaporation material used in the vacuum evaporation method usually uses a gold material with a purity of 99.9 wt% or more as a raw material, and melts the gold material in a ceramic crucible such as alumina or a carbon crucible in the atmosphere. After melting, the molten gold is poured into a mold to make ingots, and the obtained ingots are drawn into wire rods, and then cut into specific lengths to form pellets (rods, pellets). Then, the surface of the particle is washed with an acid or an organic solvent to remove impurities attached to the surface. Through the above steps, a granular gold vapor deposition material with relatively few impurities can be produced.

However, even when the vapor deposition material of gold with relatively few impurities is used in this way, bumping phenomenon occurs at the initial stage of vapor deposition, and the pre-evaporation time before actual vapor deposition becomes longer, or the condition setting of the vapor deposition device must be changed, resulting in a problem of lower production efficiency. In particular, since gold is relatively expensive as a material, there is a problem that if the pre-evaporation time becomes longer, the cost will increase accordingly. In addition, there is also a problem that the frequency of cleaning the device is increased due to contamination of the device or the inside of the crucible due to bumping.

The inventors have worked hard to study this problem, and as a result obtained the following insight: the bumping phenomenon at the initial stage of vapor deposition can be suppressed by adjusting the properties of the vapor deposition material of gold. Based on this knowledge, an embodiment of the present invention is a gold vapor deposition material used in a vacuum vapor deposition method, characterized in that the surface roughness Ra is 10 μm or less, and the number of holes with an area circle equivalent diameter of 0.1 mm or more is 1 hole/g or less. The vapor deposition material of gold adjusted in this way has the excellent effect of suppressing the bumping phenomenon at the initial stage of vapor deposition.

The surface roughness Ra of the vapor deposition material of gold according to the embodiment of the present invention is 10 μm or less. Although the reason why the bumping phenomenon at the initial stage of vapor deposition can be suppressed by adjusting the surface roughness has not yet been determined, it is considered that by reducing the surface roughness of the vapor deposition material, gas components such as oxygen, nitrogen, carbon, and hydrogen can be suppressed from adhering to the surface of the vapor deposition material, and the bumping phenomenon caused by these gas components can be suppressed. The surface roughness is 10 μm or less, preferably 3 μm or less, more preferably 1.6 μm or less, most preferably 0.6 μm or less.

The gold vapor deposition material of the present embodiment has an area circle equivalent diameter of 0.1 mm or more microcracks whose number is 1 piece/g or less. If microcracks exist, gaseous components such as oxygen, nitrogen, hydrogen, and carbon in the environment, or oil, etc., tend to adhere there, causing bumping at the initial stage of vapor deposition. In particular, if there are multiple microcracks with an area circle equivalent diameter of 0.1 mm or more, the bumping phenomenon tends to increase rapidly. Therefore, the number of microcracks with an area circle equivalent diameter of 0.1 mm or more is set to be less than 1/g, and preferably the number of microcracks with an area circle equivalent diameter of 0.1 mm or more is set to 0/g. Furthermore, if the number of microcracks per 1 g is below the decimal point, discard it.

The gold vapor deposition material of this embodiment can be produced in the following manner. Fill a carbon crucible with gold with a purity of 4N (99.99wt%) or higher, melt it in the atmosphere, in a vacuum or in an inert gas environment (preferably in a vacuum), pour the melt into a carbon mold, and cool it at room temperature to make a gold ingot. Here, if the melt contains a gas component during melting, the gas is released during solidification, and shrinkage cavities are generated in the ingot. This shrinkage cavity may become the starting point of microcracks during the wire drawing (drawing) process in the subsequent step. Therefore, in order to prevent shrinkage cavities during solidification, it is solidified at a rate of 1 to 1000°C/min from melting to solidification. Secondly, the obtained gold ingot is drawn into a wire shape, and then the surface roughness of the wire-shaped gold material is adjusted by lathe processing, and the final finishing process is performed to produce gold vapor deposition materials (particles).

The measurement apparatus, measurement conditions, etc. used for the evaluation of the gold vapor deposition material of this embodiment are as follows. (Measurement method of surface roughness) The device and measurement position used in the measurement of surface roughness are shown below. Measuring device: Contact Surface Roughness Measuring Device (Tokyo Seiki Manufacturing Co., Ltd.) Type: SURFCOM 130A JIS standard: JIS B 0601-2001

(Determination method of microcracks) The surface of the vapor deposition material of gold was observed using an optical microscope. The observed portion of the surface is to observe the entire surface of the vapor deposition material. In order to observe microcracks with an area circle equivalent diameter of 0.1 mm or more, the magnification of the microscope is set to 20 times. Randomly select 10 vapor deposition materials to be observed, and observe the entire surface of each vapor deposition material, calculate the number of microcracks with an area circle equivalent diameter of 0.1mm or more, and calculate the total number of 10, and calculate the number of microcracks per 1g from the total number and the total weight of 10 vapor deposition materials. Furthermore, generally, vapor deposition materials (particles) have various sizes or weights. It should be noted that although this case uses particles with a diameter of about 5 cm, a length of about 8 cm, and a weight of about 3.0 g as an example, it is not intended to limit the vapor deposition materials of the present invention to the above-mentioned size or weight.

(Evaluation of Knocking Phenomenon) If bumping occurs when the vapor deposition material is melted with an electron beam, the vapor deposition material will adhere to the inside of the vapor deposition device, reducing the weight of the vapor deposition material. Therefore, the bump phenomenon can be evaluated by measuring the weight loss of the evaporated material after melting. Put about 40g of vapor deposition 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 6kW, electron beam irradiation time: 2 minutes, and measure the weight loss after melting. Furthermore, under the melting conditions, almost no loss due to evaporation occurs. In addition, when the weight loss rate is less than 0.01 wt%, it is judged as ◎ (very good), when the weight loss rate is 0.01 to 0.1 wt%, it is judged as 0 (good), when the weight loss rate is 0.1 to 1 wt%, it is judged as △ (poor), and when the weight loss rate is 1 wt% or more, it is judged as × (very poor). [Example]

Next, examples and the like of the present invention will be described. In addition, the following examples represent only representative examples, so the present invention should not be limited to these examples, and should be interpreted within the scope of the technical idea described in the specification.

(Sample No. 1 to 15) A gold material with a purity of 4N (99.99wt%) is filled into a carbon crucible and melted in the atmosphere. The melt is poured into a carbon mold and cooled at room temperature to produce a gold ingot. At this time, a heater is installed on the mold, and the cooling rate is adjusted. Next, the gold ingots produced by adjusting the cooling rate were subjected to wire drawing, and then cut into diameters of 5 mm and lengths of 8 mm to produce vapor deposition materials (particles). Thereafter, lathe processing is performed on the surface of each produced particle to adjust the roughness of the surface.

For the obtained particles (sample number 1-15), randomly select 10 particles per sample, observe the entire surface with an optical microscope, calculate the number of microcracks with an area equivalent diameter of 0.1mm or more, and convert it into the number per 1g. The results are shown in Table 1. Next, each pellet was put into a copper crucible, electron beam melting was carried out under the above-mentioned conditions, and the amount of weight loss was measured. The above results are shown in Table 1. It can be considered that, as shown in Table 1, if the number of microcracks with an area-equivalent diameter of 0.1 mm or more is more than one per 1 g, the rate of weight loss is large, and bumping occurs more often. Moreover, the tendency for the weight loss rate to become high was seen as the surface roughness Ra becomes larger. [Table 1] Sample serial number Surface roughness Ra of vapor deposition material The number of microcracks with an area circle equivalent diameter of 0.1mm or more Evaluation of Bumping Phenomenon* μm piece/g 1 0.6 0 ◎ 2 1 0 ◎ 3 1 1 ○ 4 1 3 △ 6 3 0 ◎ 7 3 1 ○ 8 3 2 △ 9 6.3 0 ○ 10 6.3 1 ○ 11 6.3 3 ╳ 12 10 0 ○ 13 10 2 △ 14 10 5 △ 15 12 2 ╳ *◎: Weight reduction rate of less than 0.01 wt%, ○: Weight reduction rate of 0.01-0.1 wt%, △: Weight reduction rate of 0.1-1 wt%, ╳: Weight reduction rate of 1 wt% or more [industrial applicability]

According to the present invention, the bumping phenomenon can be suppressed when the vapor deposition material of gold is melted, thereby reducing particles adhering to the substrate. The gold vapor deposition material of one aspect of the present invention can be widely used in the formation of components in electronic parts, semiconductor devices, optical thin films, magnetic devices, LEDs, organic ELs, LCDs, etc. using vacuum evaporation methods.

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

Claims (2)

A gold vapor deposition material, which is a gold vapor deposition material used in a vacuum vapor deposition method, has a surface roughness Ra of 10 μm or less, and when observing the surface of vapor deposition material particles with a diameter of 5 mm and a length of 8 mm, the number of microcracks with an area circle equivalent diameter of 0.1 mm or more is 1 or less per 1 g of vapor deposition material particles. The vapor deposition material of gold as claimed in Claim 1 has a surface roughness Ra of 3 μm or less.