硅衬底GaN基LED薄膜芯片的应力调制

Stress Modulation of GaN Based LED Thin Film Chip on Silicon Substrate

将Si衬底GaN基LED外延薄膜经晶圆键合、去硅衬底等工艺制作成垂直结构GaN基LED薄膜芯片,并对其进行不同温度的连续退火,通过高分辨X射线衍射（HRXRD）研究了连续退火过程中GaN薄膜芯片的应力变化。研究发现：垂直结构LED薄膜芯片在160~180℃下退火应力释放明显,200℃时应力释放充分,GaN的晶格常数接近标准值。继续升温应力不再发生明显变化,GaN薄膜的晶格常数只在标准晶格常数值附近波动。扫描电子显微镜给出的bonding层中Ag-In合金情况很好地解释了薄膜芯片应力的变化。

Vertical structured thin film GaN LEDs on Si substrate were fabricated by wafer boding and substrate removing process. The LED chips were annealed at various temperatures,and highresolution X-ray diffraction（ HRXRD） measurements were performed to analyze the stress in GaN films. The results show that the annealing within 160-180 ℃ can obviously reduce the stress in GaN thin film,and the stress can be fully released at 200 ℃ and the measured lattice constants are close to the standard values of bulk GaN. Annealing at higher temperatures,the lattice constants of the GaN films only slightly fluctuate around the standard values. Scanning electron microscope（ SEM） was used to analyze the cross-sectional morphology of the bonding layers. The evolution of the stress in GaN film can be well explained by the alloying degree of the Ag-In layers.