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MOCVD半導體製程即時監控系統
- 1. MOCVD半導體製程即時監控系統 Speaker: Ju-Yi Lee Departmentof Mechanical Engineering, National Central University, Taiwan.
- 2. Outline 1. Introduction 2. Principle 3.System configuration 4. Experiments & Results 5. Conclusion
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- 5. Background • Thin filmdeposition • Metal Organic Chemical Vapor Deposition Application - Solar cell - Power chip Process condition - High temperature - High vacuum Deposition Chemical Vapor Deposition MOCVD PECVD Physical Vapor Deposition Evaporation Sputtering Vapor Deposition Liquid Phase Epitaxy Wafer Curvature Growth Rate Film Uniformity Wafer Temperature Source: itri
- 6. Literatures review (Growthrate & Temperature) • Thin film growth rate measurement Quartz crystal microbalance a Reflectance interferometry b • Temperature measurement Two-color and Multi-wavelength pyrometry c a: C. S. Lu and O. Lewis, “Investigation of film ‐ thickness determination by oscillating quartz resonators with large mass load”, 1972. b: J.A. Dobrowolski, “Optical Properties of Thin Films and Coating” Chap.42 of Handbook of Optics, McGraw-Hill, Inc, 1995. c: B. Müller, U. Renz, “Development of a fast fiber-optic two-color pyrometer for the temperature measurement of surfaces with varying emissivities”, Review of Scientific Instruments, 2001. Source: ADVANTEST Source: c
- 7. Literatures review (Temperatureon surface) • Wafer materials：Si, Sapphire, SiC, etc. • GaN/InGaN layer measurement Material transmittance 400 nm wavelength No Fabry-Pérot interferometer
- 8. Literatures review (Wafercurvature) • LayTec EpiCurveTT： Curvature range: -7000 km-1(convex) to +800 km-1(concave) Aspherical bowing curvature measurements with an Advanced Resolution option Source:LayTec
- 9. Commercial products • FRT,kSA, LayTec, etc. • The accuracy of equipment： e.g., LayTec EpiTT » Typical growth rate accuracy better than ±1% » Typical wafer temperature accuracy better than ±1℃
- 10. Purpose • Monitor ofwafer parameters Growth rate & Temperature monitoring devices Enhance quality Cost down Source: LayTec
- 11. PRINCIPLE Measurement of Growthrate Blackbody Radiation Theorem Measurement of Temperature Curvature measurement
- 12. Measurement of Growthrate • Index of refraction and growth rate nfsolven nTn w G 24 nGw 4 sL RRR 0 T w 2 2 2 2 0 2 0 )( )( )( )( s s L nn nn nn nn R 021214214122f(n) 222234 LsssLssssLsLL RnnnnRnnnnnRnnRnR )cos(21 )cos(2 00 002 ss ss RRRR RRRR rR nGtnd 22 Substrate Light Ii Reflected Light Io 2 22 2 2 0 2 0 2 0 02 00 )( )( )( )( s s s s ss nn nn NN NN rR nn nn NN NN rR
- 13. Blackbody Radiation Theorem 01000 2000 3000 4000 5000 6000 7000 0 5 10 15 20 25 30 600℃ 700℃ 800℃ 900℃ 1000℃ 1100℃ 1200℃ (nm) E b (Wm-2 sr-1 nm-1 ) • Planck’s law 1 1 , 2 5 1 T cb e c TE • Kirchhoff’s law • Real-body radiation TETE breal ,, 1 1 1c 2c : Planck’s first constant : Planck’s second constant : Absorption : Reflectance : Transmittance : Emissivity
- 14. Measurement of temperature •Opaque & Specular substrate 1 T = 1 Tcal - l c2 ln s scal R 1 • Temperature equation • Thermal signal s = C0 eEb = C0 e c1 l5 exp - c2 lT æ è ç ö ø ÷ r A r s Filter Detector 0C : System constant cal: Calibration parameter
- 15. PD PC DAQ NBF(switch) Lens Lens BS LD Lock-in Amplifier Wafer View port Vacuum Chamber FG System configuration(Temperature& Growth rate) Lens Lens BS NBF Wafer LD LD Lens PD NBF BS Wafer PD Measurement system schematic diagram and optical configuration 400 nm 635 nm 940 nm
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- 18. Air film simulation •以空氣膜實驗來模擬薄膜沉積，並驗 證系統量測能力 • 以位移台去推動楔形稜鏡來模擬薄膜 生長之情形 時間範圍 (秒) 折射率 折射率 差量 (%) 空氣膜 成長速率 (nm/s) 位移平台 移動速率 (nm/s) 成長速率 差量 (%) 0-30 1.0042 0.39 26.06 26.18 -0.46 30-60 1.0041 0.39 26.37 26.29 0.30 60-90 1.0045 0.40 59.08 59.32 0.40 90-120 1.0044 0.40 59.10 59.01 0.15 120-150 1.0039 0.39 83.21 83.70 -0.58 150-180 1.0040 0.39 83.25 83.62 -0.42空氣膜實驗架構圖
- 19. ZnO thin filmdeposition Index of refraction Thin film thickness (mm) Reference Measured Reference Measured 1.998 1.96 0.2727 0.272* Relative difference: 2% Relative difference: 0.3% Table. 1 Measurement results of the ZnO thin film Measured thickness = Growth rate × depositing time = 0.1515 Å /s × 5 hr • The ZnO thin film deposit on the silicon wafer • Monitor the growth rate, refractive index, thickness of ZnO ZnO deposit on the wafer by radio-frequency sputter Reflectance Curve of ZnO film
- 20. Wafer temperature measurement CP400 nm 940 nm (a). (b). (b)-(a) (c). (c)-(a) 455.4 450.5 -4.9 456.5 1.1 542.1 540.4 -2.3 541.3 -0.8 615.5 615.1 -0.4 615.7 0.2 701.7 702.0 0.3 701.8 0.1 781.6 780.8 -0.8 781.2 -0.4 858.5 858.6 0.1 858.6 0.1 943.0 943.2 0.2 943.1 0.1 Table. 2 The Measurement results and compare with commercial pyrometer, (a) measured by commercial pyrometer, CP, (b) by 400 nm NBF, and (c) by 940 nm NBF. (unit: °C). Measurement system set on the heating chamber 600 650 700 750 800 850 900 950 1000 -3 -2 -1 0 1 2 3 Time(s) Temperature(℃) System resolution：0.67 ℃ at 580 ℃ • Heating single silicon wafer by the heating vacuum chamber • Monitor the wafer surface temperature and analysis the system resolution
- 21. 高速旋轉下晶圓溫度量測 0 0.06 0.120.18 0.24 0.3 0.36 0.42 0.48 0.54 0.6 500 520 540 560 580 600 620 640 660 Time(s) Temperature(?) PMT-200rpm 轉速/ 光偵測器 200rpm 400rpm 800rpm PDA 0.42℃ 0.46℃ 0.56℃ APD -0.58℃ -1℃ 0.48℃ PMT -0.24℃ -0.56℃ 0.2℃ 與靜止時量測矽晶圓溫度(550.1℃)差量 於200rpm下資料擷取圖形 晶圓 載盤 • 因製程需求，晶圓在製程時需要以旋轉來達 到良好的薄膜均勻性 • 將一矽晶圓放置於加熱腔體，待加熱穩定後， 進行不同轉速的驗證系統 • 接收940 nm波段熱輻射來進行量測 • 400 nm波段之熱輻射訊號太弱，再進行旋轉 量測時無法解析
- 22. 膜厚/溫度量測系統整合 成長速率 (nm/s) 未發射率補 償之 直流項溫度 (℃) 具發射率補 償之 直流項溫度 (℃) 差量 (℃) 13.11 602.35 600.152.2 29.71 602.25 600.15 2.1 • 膜厚量測所得反射率，經由克希荷夫定律推得其 發射率，藉由此發射率來校正溫度量測結果。 整合系統量測架構圖 溫度歷時曲線與補償前後差量結果
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- 24. 藍寶石晶圓翹曲量測 • 量測藍寶石晶圓翹曲與表面輪廓重 建 量測 位置 10mm 高度值 (μm) 15mm 高度值 (μm) 20mm 高度值 (μm) 25mm 高度值 (μm) 30mm 高度值 (μm) 35mm 高度值 (μm) 1(黑) 3.676.28 8.30 8.21 6.13 3.28 2(紅) 5.21 8.01 9.84 9.75 7.52 4.48 3(藍) 7.04 9.94 12.11 11.42 9.31 6.29 4(粉) 5.58 8.74 11.42 10.61 8.03 4.74 5(綠) 4.45 7.64 9.32 8.82 6.34 3.12 pitch:100 μm
- 25. 於高速旋轉下晶圓翹曲量測 • 放置一藍寶石晶圓於旋轉平台上進行旋轉 • 分別進行700rpm、1100 rpm、1500 rpm轉速下的晶 圓翹曲量測 700rpm 1100rpm 1500rpm
- 26. Conclusion • An in-situmonitoring system for MOCVD process • Performance(compared with commercial pyrometer) Thin film parameters measurement » Relative difference of refractive index < 2% » Relative difference of thickness < 0.3% Temperature measurement » Relative difference is less than 1% » Measurement limit：above 450 ℃ Wafer curvature measurement » Relative difference is about 1%
- 27. Conclusion • Future works Improvedynamic measurement Modular & Compatible High quality hardware - Cooling system - Low noise
- 28. Thank you foryour listening Acknowledge: This research was supported by the Ministry of Science and Technology, Taiwan (MOST 104-2218-E-008-002)