The invention relates to a ceramic body. The invention also relates to a method of manufacturing a ceramic body.
Ceramic bodies have particular properties rendering them suitable for many applications. For example, ceramic bodies in the form of blocks or rods are available, for example, for use as refractory materials. A very important further use of ceramic bodies is their application as carriers or substrates. These substrates generally consist of a thin layer of sintered ceramic material, such as aluminium oxide (Al.sub.2 O.sub.3), magnesium oxide (MgO), beryllium oxide (BeO), aluminium nitride (AlN) or silicon carbide (SIC). By virtue of their favourable electrically insulating properties such substrates are used in passive and active electrical components, such as resistors, capacitors, transformers and power transistors.
The known ceramic bodies generally exhibit a combination of a number of favourable and a number of unfavourable properties. For example, substrates of relatively impure aluminium oxide and magnesium oxide have the advantage that they are cheap. However, such substrates exhibit a rather poor heat conduction. Due to this poor heat conduction they are unsuitable for use as substrate material in electrical components in which a high development of heat occurs, which heat must be dissipated via the substrate. A further disadvantage of these oxidic ceramic materials is that they have a relatively high coefficient of expansion, rendering them less suitable for a number of applications, in particular in the field of silicon semiconductor technology. The coefficient of expansion of silicon ranges from 4 to 5.
Beryllium oxide, aluminium nitride and silicon carbide have a much higher heat conduction than aluminium oxide and magnesium oxide and, hence, can more suitably be used as a heat-dissipating substrate or `heat sink` of an electrical component. In addition, ceramic bodies of aluminium nitride and silicon carbide have a coefficient of expansion which corresponds more to that of silicon, so that they are more suitable for use as substrates in the silicon semiconductor technology. However, the ceramic aluminium nitride technology is difficult due to the poor reproducibility and problems relating to purity. As a result, ceramic substrates of pure aluminium nitride are relatively expensive. Ceramic substrates of silicon carbide are also relatively expensive because the material is difficult to process. In addition, ceramic silicon carbide has a relatively high dielectric constant, so that this material is relatively unsuitable for use as a substrate in electrical components. Finally, ceramic bodies of beryllium oxide have the important disadvantage that they are toxic.