Re-understanding the essence of technology
In wafer manufacturing equipment, susceptor (base tray) is like the supporting frame of a precision oven. Traditional graphite materials will experience particle shedding and thermal deformation at a high temperature of 1700℃. However, the 8-inch SiC coating solution adopted by ASM builds a 20-50μm β-SiC crystal layer on the surface of the graphite substrate through vapor deposition, stabilizing the coefficient of thermal expansion at 4.0×10⁻⁶/℃ (RT-1000℃). It reduces the risk of deformation by 60% compared with pure graphite.
Three breakthrough points in coating technology
1.Gradient transition technology: Through pressure division control of Si-C-H ternary precursors, atomic-level transition from graphite substrate to SiC coating is achieved, avoiding the "eggshell effect" of traditional processes
2.Innovation in crystal orientation control: By adopting the (111) crystal plane selective growth strategy, the surface roughness of the coating Ra is less than 0.3μm, which is 40% higher than the industry standard in terms of flatness
3.Defect self-repair mechanism: By introducing a pulsed Si excess environment in the later stage of deposition, the micro-pores of the coating can be automatically filled, and the porosity can be controlled at <0.8vol%
Practical application value matrix
1.Thermal field uniformity: Measured results show that under the working condition of 1500℃, the temperature difference within the 8-inch wafer area is ≤±1.5℃
2.Service life doubled: Data from a certain Foundry factory shows that compared with traditional pallets, the coated version has extended the preventive maintenance cycle from 1,500 batches to 4,000 batches
3.Pollution control: Ion mass spectrometry analysis shows that the SiC coating reduces the adsorption capacity of metal contaminants (such as Fe, Ni, etc.) by two orders of magnitude
Solutions to industry pain points
In response to the special requirements of epitaxial growth of the third-generation semiconductor GaN-on-SiC, we have developed a backside patterned coating technology - retaining exposed graphite in specific areas of the tray and achieving edge temperature compensation of the wafer through differentiated thermal conductivity, successfully improving the thickness non-uniformity of the epitaxial layer from ±7% to within ±3%.
The future direction of technological evolution
With the delay of the transition of 450mm wafers, 8-inch equipment will exist for a long time. The next-generation coating technology will focus on:
1.Intelligent thermal sensitive coating: Embedded in SiC nanowire sensor network
2.Self-cleaning surface: Bionic lotus leaf effect micro-nano structure
3.Waste pallet recycling: Cold spraying remanufacturing technology
