MOCVD線上溫度量測技術開發

Abstract

本文應用熱輻射理論與相關的量測技術，開發具反射率修正之輻射高溫即時量測系統，並探討低輻射溫度範圍(400-600oC)的量測精確度改善。金屬有機化學氣相沈積(MOCVD)製程中，混合均勻的氣體反應物自基板獲得足夠熱能，發生化學反應，沈積於晶圓表面。基板表面溫度會影響磊晶速率、均勻度、薄膜厚度、晶圓彎曲等，磊晶造成的缺陷無法以後續製程降低或消除。若能即時量測晶圓表面溫度，回饋系統進行補償，是提升MOCVD製程技術的不二法門。本研究依據普朗克黑體輻射定理，實驗量測高溫矽晶圓試片的近紅外線(950 nm)熱輻射訊號，並採用相同波長之半導體雷射即時量測試片表面的反射率，修正放射率估算溫度。在低輻射溫度範圍，量測系統的訊噪比低，需以多溫度點修正方式，提高量測精確度。另外採用Sakuma-Hattori方程式，以曲線擬合方式估算溫度。在500-600 oC範圍內，前者精確度可達±2.66 oC，後者可達±6.47oC。

This thesis studies the thermal radiation theory and applies its measuring technology for developing the in-situ high-temperature pyrometry with the reflectance correction. Measuring accuracy and precision improvements of the low radiation in 400-600°C are also investigated. In metal organic chemical vapor deposition (MOCVD) process, the mixed gases can react chemically and deposit on the wafer surface by applying sufficient heat. Therefore, temperature distribution of the wafer surface can affect the growth rate, epitaxial uniformity, thin film thickness, and wafer curvature, etc.. Moreover, owing to the generated defects during epitaxial process that cannot be reduced or eliminated by the following process and also influences the quality of end product, real-time feedback of temperature from wafer surface can compensate and improve this situation. This method also is one way to promote MOCVD process technology. Based on the Planck's theory of blackbody radiation, the near infrared (950 nm) thermal radiation signal is measured from the surface of silicon wafer specimen through the experimental method of geometrical optics. Reflectance of wafer surface used for the purpose of temperature correcting is also measured by using semiconductor laser with the same wavelength. In the temperature range of low radiation (400-600°C), because of lower signal-to-noise ratio, more measured temperatures are required for improving the accuracy and precision. In addition, the Sakuma-Hattori equation is used for estimating temperature via nonlinear regression. In the range of 500-600°C, the accuracy of former is up to ±2.66°C, and that of later is up to ±6.47 °C.