Tungsten metal material is the highest melting point of nature metal (3410°c), at the same time with high-strength, high hardness, low resistivity characteristics. Tungsten metal materials resistant to high temperature, impact resistance, wear resistance, thermal stability, to ensure that the device at high temperature stability of the work, is the MEMS device processing and manufacturing of structural materials good choice, especially for high-temperature and other harsh or extreme environment. Tungsten Metals Traditional tungsten materials use physical or chemical deposition methods to form thin films, but the thickness of thin films is generally no more than 2 microns due to the process limitation and stress, which affects the design and manufacture of the device. If the tungsten metal material is used as structural material instead of the traditional monocrystalline silicon material to make MEMS switches, MEMS resonators, MEMS probes, micro-EDM electrodes and other devices, Tungsten Metals these devices will have more excellent electrical, mechanical and high-temperature resistance characteristics because of the characteristics described above. Tungsten metal is the main material of microelectronic chip test probes, and with the reduction of chip pitch, Tungsten Metals probes and probe cards also need to be miniaturized with new micro-machining methods, compared with the current single crystal Silicon microprobe (card), tungsten metal material formed by micro-probe (card) with high hardness, low wear rate, low resistance, high reliability. Because of the high density and hardness of tungsten metal materials, the etching rate of traditional reactive ion etching process is very low, and the transverse drilling is also larger, Tungsten Metals it is not possible to achieve large depth and high aspect ratio etching in relatively short time, which can not meet the manufacturing demand of MEMS devices. Therefore, the application of tungsten metal materials is mostly in the integrated circuit technology, through physical or chemical deposition method to prepare a layer of thickness less than 2 micron film, then the traditional reactive ion etching process is used to fabricate a part of the device, such as a metal grating, a metal interconnect, a metal diode, a combination of etched gas or gas used in CF4, cf4+02, Cl2, cl2+02, SF6, sf6+02, NF3, ccl4+02, etc.
The etching method used involves flat panel plasma etching (PE), reactive plasma etching (RIE), electron cyclotron resonance plasma etching (ECR), etc., because the plasma density is relatively low (less than IOICI-IO12CNT3), the energy is low, the etching rate produced is generally much less than 1 microns per minute. Tungsten Metals At present, there is no report on the use of tungsten metal materials as the main structure of the MEMS devices, while the existing thin film tungsten material etching process is generally low, anisotropy difference, becoming the main bottleneck. For the processing of tungsten metal material, it is not reported that the process of etching with high rate and aspect ratio can be achieved.
Tungsten is a commonly used refractory metal, density 19.35, melting point 3410°c, boiling point 5660°c. Tungsten has large hardness, high density and good high temperature strength. At room temperature, tungsten is stable in the air, and 400 ℃ begin to lose luster, forming a blue-black compact tungsten oxide protective film. At 740 ℃, the tungsten trioxide was transformed from three-oblique crystalline system to a quadrilateral crystal system, and the protective film was destroyed. Tungsten is oxidized to tungsten dioxide in water vapor above 600 ℃. Tungsten is not easily eroded by acid, alkali and aqua regia at room temperature, Tungsten Metals but is dissolved in mixed acids of concentrated nitric acid and hydrofluoric acid. Tungsten can be rapidly eroded by oxidizing molten salts such as sodium nitrate.
The average content of tungsten in the crust is 1.3x10-6, the average content of granite is 1.5x10-6. Tungsten in the natural world is mainly a six-valence cation, its ionic radius is small, high electricity price, with strong polarization ability, easy to form a complex anion, Tungsten Metals so tungsten mainly in the form of complex anions [wo4]2-, and $literal, mn2+, + and other cations to form black tungsten ore or scheelite. The important minerals of tungsten are tungstate, and only 20 kinds of tungsten and tungsten minerals are found in the crust, black tungsten Ore group: Tungsten Manganese ore, tungsten iron ore, black tungsten ore; Scheelite Group: scheelite (calcium tungsten ore), molybdenum scheelite, copper scheelite; tungsten Chinese minerals: tungsten hua, water tungsten hua, high-speed railway tungsten Hua, yttrium tungsten Hua, cu-W, tungsten-aluminum ore; rare tungsten Minerals: tungsten galena, oblique tungsten lead, molybdenum, tungsten, zinc, tungsten, bismuth, antimony, tungsten, titanium, yttrium thorium ore (including tungsten), tungsten sulfide ore. The only black tungsten ore (Fe, Mn) WO4 and scheelite have the economic value of mining.
Tungsten metal wire, rods, sheets, etc. used to make light bulbs, Tungsten Metals electronic tube components and arc welding electrodes.