Analysis of thermal flow and mass transport in MOCVD round jet chamber

• Main Authors: Cheng-Hao Liu, 劉正皓
• Other Authors: Jyh-Chen Chen
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/13649926460549341073

碩士 === 國立中央大學 === 機械工程學系 === 104 === Metalorganic chemical vapour deposition (MOCVD), with it advantages as better epitaxial layer and high material purity, is a vital process technique for GaN growth in the LED Epitaxy industry.The finite element analysis (FEM) was employed in the current study for experimental comparison, aiming to make the growth rate more close to actual processes and take into account the reaction depletion resulting from the reaction of mass transfer on the surface.The Langmuir equation was adopted to calculate the absorption rate on wafer surfaces among species after the vapor reaction. In addition, MMG was used as the major absorbed species,with one major reaction equation.Over simplicity of round jet was solved first and the slot jet was then applied to the design of deflectors.To improve the inlet flow rate, the flow field analysis on overall chambers was carried out and compared against the simulation to make sure the authenticity of the simulation,with relevant simulation analysis implemented in conditions appropriate for the growth of the thin film.The results of the simulation revealed that the increase in the intake flow rate enabled the gas concentration to move towards the center of the slot jet,making the vortex as the result of inertia even stronger. The optimal Reynolds number of the inlet flow rate should be between 2 and 3. Increase in the carrier plate temperature made the temperature gradient between the inlet and the carrier plate higher.When Rij reached over 5000, vortexes resulting from thermal buoyancy appeared around the carrier plate and affected the flow field.The increase in carrier plate spin significantly inhibited the effect of thermal buoyancy and thus the resulting vortexes.When Rjw was 0.05, thermal vortexes could be effectively inhibited.The increase in pressure was beneficial to growth rate, yet the flow field became much uncontrollable.Unstable flow field easily led to poor evenness.The next step was modifying the outlet based on basic geometrical parameter and outlet geometric parameter.The results indicated that when the outlet was widened to 27.5mm and changed to round style rather than its original single-hole style, better inlet evenness could be obtained and the overall flow field became plug flow.