Presentation on theme: "Measuring film thickness using Opti-Probe"— Presentation transcript:
1 Measuring film thickness using Opti-Probe Weilan Ladeau3/01/03
2 Opti-Probe Theory Reflection and Refraction Intensities Polarizations Phase delayBrewster’s angletan (ib)= ni/no
3 Phase delay The length 2d of the extra travel The velocity of light propagation in the filmThe wavelength of the light
4 Brewster’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.
5 BPR ( 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.
7 Diode 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.
8 Diode 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
9 Profile Response of the array results Profile symmetrical Software folds profile and takes average
10 S & P Polarizations Rays on XZ and YZ planes are linearly polarized. Rays on other planes elliptically polarizedEasier to calculate rays on two planes.
11 S & 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
12 Thickness Estimation Know n1 of film Count # of cycles in A profile Maximum in reflectivity occurs:
13 We 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