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The millimeter wave (MMW) sintering of alumina ceramic had been performed. The results revealed that MMW sintered alumina has higher density than that of conventional method on all sintering temperature. However microstructure evaluation demonstrates that grain growth of MM wave annealed alumina is faster than in conventional annealing. It indicates that MM wave enhanced mass transport and solid state reaction rates during sintering. The empirical observations of microwave enhancements have been broadly known as microwave effect. Even though no satisfactory theory existed to explain the effect but the presence the electromagnetic waves (EMW) during microwave heating is clearly the key. In this paper, microwave effect on grain growth of alumina ceramic is presented. Some effective and unique characteristics of the EMW sintering were also discussed as well.

We propose a compensated mesh pattern filling method to achieve highly uniform wafer depth etching (over hundreds of microns) with a large-area opening (over centimeter). The mesh opening diameter is gradually changed between the center and the edge of a large etching area. Using such a design, the etching depth distribution depending on sidewall distance (known as the local loading effect) inversely compensates for the overcentimeter-scale etching depth distribution, known as the global or within-die(chip)-scale loading effect. Only a single DRIE with test structure patterns provides a micro-electromechanical systems (MEMS) designer with the etched depth dependence on the mesh opening size as well as on the distance from the chip edge, and the designer only has to set the opening size so as to obtain a uniform etching depth over the entire chip. This method is useful when process optimization cannot be performed, such as in the cases of using standard conditions for a foundry service and of short turn-around-time prototyping. To demonstrate, a large MEMS mirror that needed over 1 cm 2 of backside etching was successfully fabricated using as-is-provided DRIE conditions.

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