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The electric properties of BaTiO 3 -(Bi 1/2 Na 1/2 ) TiO 3 (BT-BNT) solid solution ceramics were studied as a lead-free PTCR (positive temperature coefficient of resistivity) thermistor material usable over 130°C. For determining the maximum switching temperature T s , the phase diagram of BT-BNT binary system was clarified. Two semiconductorization processes and their electric properties are described. The lanthanum(La)-doped BBNT ceramics sintered in air still showed dielectric behaviors, but the niobium(Nb)-doped ones had a low resistivity at room temperature, ρ RT , on the order of 10 3 Ωcm and showed a PTC behavior. Sintering under a low O 2 atmosphere produces BT-BNT ceramics with less than 10 2 Ωcm compared to those prepared in air. Our current research produced the BBNT ceramics with T s values around 210°C by increasing the (Bi 1/2 Na 1/2 ) content in the ceramics.

In order to reduce the on-resistance in vertical power transistors, backside thinning is required after device processing. However, it is difficult to thin an SiC wafer with a high yield rate by conventional mechanical machining because its high hardness and brittleness cause cracking and chipping during thinning. In this study, a small rectangular SiC sample was thinned by plasma chemical vaporization machining (PCVM), which is plasma etching using atmospheric-pressure plasma. As a result, the sample was successfully thinned to 40 m without any cracking or chipping. Furthermore, the surface roughness was improved after thinning, and the edge of the wafer became rounded automatically. Therefore, PCVM can be used as an effective method for thinning SiC wafers.

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