磷化铟单晶退火及热应力分布的研究

Annealing and Thermal Stress Distribution of InP Single Crystal

磷化铟单晶生长是一种液相转变为固相的过程,晶体生长过程中的热场条件直接影响晶体的热应力、电学均匀性、位错密度、晶片的几何参数。通过实验和理论分析研究热场条件对InP晶体生长的影响,通过晶锭退火、晶片退火、位错测量、应力测量等实验研究、分析位错密度与残余热应力的关系和减除热应力的方法。在InP晶体生长阶段,熔体温度、炉内气体压强、氧化硼厚度、熔体及晶体的形状、炉体结构、加热功率等都是影响晶体生长过程中热场分布的因素。这些因素共同导致晶体内部产生径向和轴向温度梯度,从而产生热应力。晶体长时间处于温度梯度很小的高温状态,能使其应力得到释放并且内部的晶格畸变也会发生变化。通过后期适当的高温热处理可以使晶体内部残余热应力得到释放。采用金相显微镜观察InP样片观察到的位错呈现"十"字状分布,中心和边缘位错低,两者之间的"十"字部分位错高,与晶片残余应力分布基本保持一致。晶体生长过程中,热应力大于临界剪切应力导致的晶格滑移使InP的晶格结构产生畸变,导致晶体内部形成位错。

The process of indium phosphide single crystal growth was a liquid phase into a solid phase. The thermal field conditions during the growth process directly affected the thermal stress of the crystal, the electrical uniformity the dislocation density, the geomettic parameters of the wafer. The effect of the thermal field on growth of InP single crystal by experiment and theory was discussed. Using InP ingot annealing, wafer annealing, dislocation distribution and thermal stress distribution experiment, the relation between dislocation density residual and distribution thermal stress and the way to reduce thermal stress was analyzed. The melt temperature, the press of the atmosphere, the thickness of B2 03 , the shape of melt and crystal, the set of furnace and the power of the heater could af-fect the thermal field during the growth of InP. All these factors bought radial and axial temperature gradient which led to thermal stress in InP ingot. Being annealed in a high temperature with low temperature gradient for a long time, the thermal stress in crystal could release and the lattice distortion could restore. An appropriate high-temperature annealing treatment could reduce the thermal stress. The micrograph of dislocation distribution of the wafers which were observed by metalloscope was like ＂ 十＇＂ cross, which was consistent withthe residual stress distribution. In the crystal growth process, the crystal lattices were distorted when the thermal stress was greater than the critical shear stress, resulting in the internal formation of dislocations in the crystal.