Electrical engineering, Electronics
– Wafer production
ELECTRICAL ENGINEERING, ELECTRONICS // KILN AND FURNACE ENGINEERING// ON- AND OFFSHORE ENGINEERING // POWER ELECTRONICS // MEASURING SYSTEMS // CONTROL SYSTEMS // WAFER PRODUCTION // ELECTRIC MOTORS // TELECOMMUNICATIONS // LIGHTING SYSTEMS // PHYSICAL RESEARCH // ELECTRONICS – GENERAL
The requirements for wafer fabrication technology are extremely high in respect of the achievable geometric properties and zero contamination.
In semi-conductor technology, equipment components made of oxide and non-oxide materials are generally used in positions that are of key importance for achieving the required geometric properties of wafers. For instance, for 12“ wafers, targets include a thickness of 0.7 mm, a deviation from surface evenness in the order of 10-6 mm and a deflection of maximum 25 µm.
For secure fixing of such wafers on a substrate, frequently large-size plates made of Al2O3 and Si3N4 ceramics are used, which exhibit the general technical quality features listed in the following:
- High purity
- Low alkali content
- High mechanical resilience to pressure and bending
- High modulus of elasticity
- High edge stability
- Thermal strength from cryo-range to beyond 1200 °C
- High thermal conductivity
- High thermal shock resistance
- No thermally induced shape changes
- Specific electrical resistance: >1014 Ω*cm
- Low dielectric losses
- High geometric and topographic precision
- Applicability of substance-to-substance joining methods for high-vacuum-tight material composites
- Reliable long-term use in operating conditions
From Al2O3 ceramics, sandwich structures with high geometric precision can be formed by means of glass soldering. Such a configuration enables the incorporation of channel systems for heating or cooling processes and electrodes for electrostatic fixing of wafers between the plates.
On account of its specific technical properties, Si3N4 ceramic can be recommended not just for substrate components but also for components that have to ensure high resistance to wear and contamination.
In silicon technology, ozone is used as a gaseous cleaning medium as an effective means for killing bacteria in the ambient air. The technical properties of high-purity, dense-sintered Al2O3 ceramic can be efficiently used for this purpose. It also exhibits other properties important for this application, for example:
- Thermal stability: >1700 °C
- Dielectric strength: >20 KV/mm
- Resistance to corrosion caused by ozone
- Realization of high-vacuum-tight ceramic-ceramic composites by means of glass soldering
A generator unit made from this type of material permits, compared to existing systems, a significant reduction in size while maintaining the same output. In this way, a considerable improvement in efficiency is possible in operation.