Aluminum nitride (AlN) could be a kind of comprehensive high performance new ceramic material. It has a series of excellent features, such as excellent thermal conductivity, a reliable electrical insulation, low dielectric constant , dielectric loss, non-toxic and matching with the silicon thermal expansion coefficient. And it’s considered as a new generation of the semiconductor substrate and also the ideal materials of the electronics packaging , and has received wide attention by the researchers at home and abroad.
In theory, the thermal conductivity of AlN is 320 W/(m), actual thermal conductivity of industrial preparation of polycrystalline aluminum nitride is up to 100 ~ 250 W/(m), the value is five ~ ten times to a traditional alumina substrate, close to the thermal conductivity of beryllium oxide, but owing to its high toxic, beryllium oxide was gradually stopped to be used in the industrial production. The comprehensive performance of aluminum nitride ceramic is good compared with many alternative ceramic materials, it is very suitable for the semiconductor substrate and structural packaging material with an enormous application potentiality in the electronic industry.
High resistivity, high heat conductivity and low dielectric constant are the most basic requirements of substrate in integrated circuit for packages. Encapsulation should match well with silicon substrate with good thermal matching, easy to be formed, high surface smoothness, easy to be metalized , easy processed characteristics and certain mechanical properties and low cost, etc. Most ceramics is ionic bond and covalent bond strong material, has excellent comprehensive performance and is commonly used in electronic packaging substrate materials, has high insulation performance and excellent high frequency characteristics. At the same time, linear expansion coefficient and electronic components are very similar with stable chemical performance and high thermal conductivity. For a long time period, most of the high power hybrid integrated circuit substrate material used Al203 and BeO ceramic, but Al203 substrate has the characteristics of low thermal conductivity and thermal expansion coefficient and Si mismatching; BeO, although it has excellent comprehensive performances, its high production cost and virulent disadvantage limit its application. Therefore, from the factors such as performance, cost and environmental protection, both of them can not fully meet the needs of the development of modern power electronic devices.
Electronic thin film material is the basis of microelectronics technology and electronic technology, so the studying of all kinds of new electronic thin film materials is becoming a hot attention spot to many researchers. AlN, which is found in the 1860 s, can be used as electronic thin film materials, and has wide application. In recent years, wide bandgap semiconductor material and the electronic devices represented by Ⅲ A family of nitrides have a fast development, known as third generation of semiconductor after the first generation represented by Si semiconductor and the second generation represented by GaAs semiconductor. AlN as typical Ⅲ A family of nitride has obtained more and more the attentions of the researchers at home and abroad. At present, many countries compete to invest a lot of manpower and material resources to study AlN thin films. Because the AlN has many excellent properties including wide band gap, strong polarization, 6.2eV forbidden band width to make it has broad application prospect in the machinery, microelectronics, optical, and electronic components, surface acoustic wave (SAW) device manufacturing, high frequency broadband communications and power semiconductor devices and other fields. A variety of excellent properties of AlN determine its various applications, such as piezoelectric thin film , electronic devices , integrated circuit encapsulation, dielectric isolation and insulation material , used as the blue light, ultraviolet light-emitting material, it is the current research hotspot.
Aluminum nitride (AlN) with high thermal conductivity, the theory of thermal conductivity is 320 w/(m • K), the actual value is up to 260 w/(m • K), 10 ~ 15 times of alumina ceramics , the relative low dielectric constant, (about 8.8) and reliable electrical insulation resistivity (> 1016 q, m – 1), high temperature resistance, corrosion resistance, non-toxic, good mechanical properties and thermal expansion coefficient of matching with the silicon (20 ℃ ~ 500 ℃, 4.6 x 10-6 K – 1) and a series of excellent properties, more and more widely applied in many high technology fields, which in many cases require AlN for abnormity and micro parts, but the traditional mold and isostatic pressing process cannot be prepared ceramic parts of complex shape, plus the AlN ceramic material inherent low ductile and brittle and difficult to machining flaws, made using traditional machining method is difficult to preparation of the complex shapes of AlN ceramic parts. In order to fullly take the advantages of AlN , to broaden its application scope, the good settlement of the complex shape of AlN ceramic forming technology is the key step.
