Low-temperature hot-press sintering of AlN ceramics with MgO-CaO-Al2O3-SiO2 glass additives for ceramic heater applications

Aluminum nitride (AlN) is used a ceramic heater material for the semiconductor industry. Because extremely high temperatures are required to achieve dense AlN components, sintering aids such as Y2O3 are typically added to reduce the sintering temperature and time. To further reduce the sintering temperature, in this study, a lowmelting-temperature glass (MgO-CaO-Al2O3-SiO2; MCAS) was used as a sintering additive for AlN. With MCAS addition, fully dense AlN was obtained by hot-press sintering at 1500 degrees C for 3 h at 30 MPa. The mechanical properties, thermal conductivity, and volume resistance of the sintered AlN-MCAS sample were evaluated and compared with those of a reference sample (AlN prepared with 5 wt% Y2O3 sintering aid sintered at 1750 degrees C for 8 h at 10 MPa). The thermal conductivity of AlN prepared with 0.5 wt% MCAS was 91.2 W/m center dot K, which was 84.8 W/m center dot K lower than that of the reference sample at 25 degrees C; however, the difference in thermal conductivity between the samples was only 14.2 W/m center dot K at the ceramic-heater operating temperature of 500 degrees C. The flexural strength of AlN-MCAS was 550 MPa, which was higher than that of the reference sample (425 MPa); this was attributed to the smaller grain size achieved by low-temperature sintering. The volume resistance of AlN-MCAS was lower than that of the reference sample in the range of 200-400 degrees C. However, the resistivity of the proposed AlN-MCAS sample was higher than that of the reference sample (500 degrees C) owing to grain-boundary scattering of phonons. In summary, the proposed sintering strategy produces AlN materials for heater applications with low production cost, while achieving the properties required by the semiconductor industry.

Automated summary

The study used a low-melting-temperature glass (MCAS) as a sintering additive for AlN, successfully reducing the sintering temperature and achieving fully dense AlN materials with properties required by the semiconductor industry.