半绝缘SiC单晶电阻率均匀性研究

采用非接触电阻率面分布(COREMA)方法对本实验室生长得到的2英寸(50 mm)4H和6H晶型半绝缘SiC单晶片进行电阻率测试,结果发现数据的离散性大,低者低于测试系统下限105Ω.cm,高者高于其上限1012Ω.cm,甚至在同一晶片内会出现小于105Ω.cm,105~1012Ω.cm和大于1012Ω.cm的不同区域,而有的晶片则电阻率的均匀性较好。将SiC电阻率测试结果与二次离子质谱(SIMS)对晶体内主要杂质V,B和N含量测试结果相结合,初步探讨得到引起掺钒SiC单晶电阻率的高低及均匀性的变化由补偿方式决定,在深受主补偿浅施主模式下,V的浓度控制在2×1016~3×1017cm-3,N的浓度控制在1×1016cm-3左右,深受主钒充分补偿浅施主氮,制备得到的SiC单晶具有半绝缘性,且电阻率均匀性好。

Study on the Resistivity Uniformity of the SI SiC

The uniformity of the resistivity in SI2" (50 mm) 4H-SiC and 6H-SiC crystals grown in our laboratory by physical vapor transport process under high purity condition. The resistivity of all these wafers was measured by SemiMap COREMA-WT (contactless resistivity mapping) at room temperature. It is found that the resistivity of SiC varies widely with different wafers, from 10~5Ω·cm to larger than 10~(12)Ω·cm, even in the same wafer with different areas, the values may be below 1 × 10~5Ω·cm, between 1 × 10~5 ～ 1 × 10~(12)Ω·cm,and over 1 × 10~(12)Ω·cm, some wafers with very uniform resistivity axe also achieved. Secondary ion mass spectroscopy (SIMS) was used to determine the impurities of boron, nitrogen and vanadium which play an important role in terms of resistivity. In general, as long as the vanadium concentration is controlled at 2×10~(16)～3×10~(17)cm~(-3) and the nitrogen concentration is 1 × 10~(16)cm~(-3), which means the vanadium act as deep acceptor to compensate all donor nitrogen impurity, SI SiC with high resistivity uniformity can be obtained.