High temperature stability of lanthanum silicate dielectric on Si (001)

Integration of a high-κ dielectric into complementary metal-oxide-semiconductor devices requires thermal stability of the amorphous dielectric phase and chemical compatibility with silicon. The stability of amorphous lanthanum silicate on Si (001) is investigated by means of metal-insulator-semiconductor capacitor measurements, back side secondary ion mass spectrometry (SIMS) depth profiling, and high-resolution transmission electron microscopy (HRTEM) after a 1000°C, 10s anneal in nitrogen ambient. Back side SIMS depth profiling of the TaN∕LaSiOx∕Si gate stack reveals no detectable lanthanum in the silicon substrate, and HRTEM shows stability of the amorphous LaSiOx. An effective work function near 4.0eV is obtained for these gate stacks, making the stack design ideal for n-type metal-oxide-semiconductor device fabrication.

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