Presentation on theme: "Measuring film thickness using Opti-Probe"— Presentation transcript:
1Measuring film thickness using Opti-Probe Weilan Ladeau3/01/03
2Opti-Probe Theory Reflection and Refraction Intensities Polarizations Phase delayBrewster’s angletan (ib)= ni/no
3Phase delay The length 2d of the extra travel The velocity of light propagation in the filmThe wavelength of the light
4Brewster’s angleBrewster's angle is the angle of incidence for which the reflected intensity is 0 for the p-polarized rays.Provides information on the index, n1 of the film.
5BPR ( Beam Profile Reflect meter) Measures reflectivity as a function of angle of incidence on the wafer.The intensity of reflected light is the square of the total amplitude of waves.BPR can be used to measure thickness, n of a film.
7Diode laser and Lens Single wavelength (6750 A) Using two objective lens (5X and 80X)Forms a column of light before entering lensCone shaped upon exitThe angle of incidence of a ray is related to its distance to the center of the beam.
8Diode laser and Lens Light collected by a linear diode. Diodes mm apartEach diode measures the light intensity resulting form interference pairs of ray #1 & ray #2
9Profile Response of the array results Profile symmetrical Software folds profile and takes average
10S & P Polarizations Rays on XZ and YZ planes are linearly polarized. Rays on other planes elliptically polarizedEasier to calculate rays on two planes.
11S & P PolarizationsP-polarized rays collected on B-array aligned // to X directionS-polarized rays collected on A-array aligned // to Y directionProfiles complement each other giving us more information
12Thickness Estimation Know n1 of film Count # of cycles in A profile Maximum in reflectivity occurs:
13We obtain following values: Filmn1r2Cos(r2)Oxide1.5370.8011574ANitride2270.8915340APolySi4130.9733751A~ n1*8000A for once full cycle in profileThickness = m*ni*8000A; m=# of cycle in profile