PVT方法下AlN烧结工艺坩埚盖处氧杂质沉积行为研究

Study on Oxygen Deposition Behavior on Crucible Lid by PVT AlN Sintering Process

AlN晶体中的氧杂质会严重影响晶体性能。因此,氧含量的控制一直是AlN晶体生长工艺中的热点和难点。为了减少AlN晶体中的氧杂质含量,通常在长晶之前使用粉料高温烧结工艺去除大部分的氧杂质。使用XRD及EGA等检测方法,对不同烧结工艺下AlN烧结过程中坩埚盖处的氧杂质沉积行为及其规律进行了对比研究。研究发现,使用低温(900~1 100℃)真空保温与1 500℃的氮气保护下保温相结合的方法可以极大促进氧杂质在坩埚盖处的前期沉积。在氮气保护环境下进一步提升烧结温度至2 000~2 100℃并经过一段时间的保温后,坩埚盖沉积物表面会出现黄褐色AlN结晶层,相应的检测结果表明此阶段坩埚盖处的氧杂质大量挥发,沉积过程已经基本结束。

Oxygen strongly degrades the properties of AlN crystals,thus reducing oxygen concentration in AlN single crystals is a hot topic in the research of AlN crystal growth.Prior to AlN crystal growth,high-temperature sintering process is commonly employed to reduce oxygen concentration in AlN powder source.In this paper,the oxygen deposition behavior on crucible lids under different sintering conditions was investigated by the XRD analysis and EGA measurement.The results show that holding at 900~1 100 ℃ under vacuum together with holding at 1 500℃ under high-purity nitrogen atmosphere for several hours can greatly promote the oxygen deposition on the crucible lid at the early sintering stage.Further increasing the holding temperature to 2 000~2 100 ℃ under high-purity nitrogen atmosphere,the oxygen deposited on the crucible lid decreases dramatically,and a brown colored AlN crystallized layer with very low oxygen concentration will form on the deposition surface,which implies that oxygen impurity in AlN powder source was removed remarkably by combined sintering process.