喷淋式MOCVD反应器中AlN的生长速率和化学反应路径的数值模拟研究

利用数值模拟方法,结合反应动力学和气体输运过程,研究喷淋式MOCVD反应器中AlN的生长速率和气相反应路径与反应前体流量(NH₃和 H₂)、进口温度、压强、腔室高度等参数的关系。研究发现:薄膜生长前体和纳米粒子前体的浓度决定了不同的生长速率和气相反应路径。在低Ⅴ/Ⅲ比(2 000)、高H₂流量(12 L/min)、高进口温度(700 K)、低压强(2 kPa)、低腔室高度(5 mm)等条件下,气相反应路径由加合路径和热解路径并存,生长速率较高。反之,化学反应路径则由加合路径主导,生长速率较低。上述参数对反应路径的影响原因包括:气体流量(NH₃和H₂)较大,反应前体被带出生长区域或被稀释;低压强和低腔室高度使粒子碰撞频率降低、驻留时间缩短,进而削弱了寄生反应;进口温度导致温度梯度的变化。

Numerical Simulation Study on Growth Rate and Gas Reaction Path of AlN-MOCVD with Close-Coupled Showerhead Reactor

By numerical simulation and combining reaction kinetics and gas transport process, the effects of gas flow rate (NH₃ and H₂), inlet temperature, pressure and chamber height on the growth rate and gas reaction path of AlN-MOCVD with close-coupled showerhead reactor were studied. It is found that the concentrations of AlN film precursor and nanoparticle precursor determine the growth rate and the gas reaction path. Under the conditions of low Ⅴ/Ⅲ ratio(2 000), high H₂ flow rate (12 L/min), high inlet temperature(700 K), low pressure(2 kPa) and low chamber height(5 mm), the reaction is dominated by both the adduct path and the pyrolysis path, and the growth rate is relatively high. On the contrary conditions, the reaction is dominated by the adduct path and the growth rate is rather low. There are different reasons for the effects of the above parameters on the reaction path, such as, the high NH₃ flow rate brings the precursor out of the growth zone and the high H₂ flow dilutes the reaction precursors in the growing region; the low pressure and low chamber height reduce the particle collision frequency and residence time, and weaken the parasitic response; the inlet temperature causes a change in the temperature gradient.