Speaker: Hao-Wen Chuang ( 莊浩彣 ) Advisor: Assistant Prof. Chung-Hao Tien Assistant Prof. Yi-Pai Huang Display Institute, National Chiao Tung University, Hsinchu, Taiwan Apr 光學元件精密製造與檢測 第十三章 薄膜品質檢測 13.1~13.2 國家實驗研究院 儀器科技研究中心

2 Advanced Display Optics Lab Optical properties of thin film - transmittance - reflectance - scattering - absorption Ellipsometry Spectrometer (Envelope method) Outline

3 Advanced Display Optics Lab UV/Vis/NIR Spectrophotometer Lamp area: Tungsten-halogen and deuterium or xenon only Monochromator: continuous spectrum  single wavelength filter wheel + grating grating in lines/mm (resolution) Double-grating: higher resolution & accuracy Monochromator: continuous spectrum  single wavelength filter wheel + grating grating in lines/mm (resolution) Double-grating: higher resolution & accuracy Sample area: Double beam Detector area: UV and Vis – PMT or silicon photodiode NIR – Peltier cooled PbS Detector area: UV and Vis – PMT or silicon photodiode NIR – Peltier cooled PbS 分光光譜儀

4 Advanced Display Optics Lab Transmittance (%T)  Polish thin film (1) normal incidence (2) sample’s area larger than spot size - if not, use aperture - if less than 1 mm, use beam condenser oblique incidence: Polarized effect occurs after passing through spectrometer  Shift of spectrum Add depolarized crystal  unpolarized and random light

5 Advanced Display Optics Lab Reflectance (%R)  Polish thin film – specular reflectance Relative reflectance Standard mirror is for near normal angle (<10°) Absolute reflectance VN type or VW type baseline correction: M1  M2’  M3’  L1 defined as 100% reflectance M1  M2”  sample  M3”  L1 energy loss VW type for high reflectance and larger sample VN type for low reflectance and small sample VW type for high reflectance and larger sample VN type for low reflectance and small sample

6 Advanced Display Optics Lab Scattering (I) scattering transmittancediffuse reflectance Integrating sphere diameter: 60 mm or 150 mm

7 Advanced Display Optics Lab Scattering (II)  Haze ( 霧度 )

8 Advanced Display Optics Lab Absorption If thin film is on polish substrate, no scattering OD (optical density) T and R without ST, R, and S

9 Advanced Display Optics Lab Optical properties of thin film - transmittance - reflectance - scattering - absorption Ellipsometry Spectrometer (Envelope method) Outline

10 Advanced Display Optics Lab Ellipsometry Ellipsometry measures the change of polarization upon reflection to determine the refractive index and thickness of thin film. 1945, Alexandre Rothen non-destructive and contactless Applications: (1) semiconductor manufacturing - thinner gate oxide (2) lithography & etching - Deep-UV; etching end-point (3) TFT-LCD - residual stress

11 Advanced Display Optics Lab Classification of Ellipsometer Null ellipsometer rotate P, C and A to get null light intensity Rotating element photometric ellipsometer slowly rotating polarizer or analyzer or compensator at fixed frequency (5~50Hz) Phase-modulation ellipsometer use phase modulator (like a fast-switching compensator) advantagesdisadvantages Nullsimple, cheap, higher accuracy time-consuming RotatingIndependent of wavelength shift of rays Phase-modulationIn-situnoise

12 Advanced Display Optics Lab Ellipsometer  Basics of Ellipsometer Fresnel Reflection Coefficient:

13 Advanced Display Optics Lab Calculations light sourcepolarizerisotropic sample analyzerdetector where substitute to get measure Numerical analysis…

14 Advanced Display Optics Lab Optical properties of thin film - transmittance - reflectance - scattering - absorption Ellipsometry Spectrometer (Envelope method) Outline

15 Advanced Display Optics Lab Spectrometer (Envelope method)  Swanepoel - finite substrate Transmission spectrum of bare substrate Ts(λ), Transmission spectrum (normal incidence) of whole system, n>n s, in the area for k=0 and n>>k k can be neglected n>n s, in the area for k=0 and n>>k k can be neglected

16 Advanced Display Optics Lab Spectrometer (Envelope method) thickness refractive index Extinction Coefficient or Absorption coefficient

17 Advanced Display Optics Lab Conclusions Transmittance – spot size adjusted by aperture or beam condenser Reflectance – Relative Reflectance needs standard mirror. Absolute reflectance: VN type or VW type Scattering can be measured by integrating sphere. Ellipsometry measures the change of polarization upon reflection to determine the refractive index and thickness of thin film. Envelope method for Spectrometer is an alternative way to obtain optical constants of thin film.

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