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Measuring film thickness using Opti-Probe

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Presentation on theme: "Measuring film thickness using Opti-Probe"— Presentation transcript:

1 Measuring film thickness using Opti-Probe
Weilan Ladeau 3/01/03

2 Opti-Probe Theory Reflection and Refraction Intensities Polarizations
Phase delay Brewster’s angle tan (ib)= ni/no

3 Phase delay The length 2d of the extra travel
The velocity of light propagation in the film The wavelength of the light

4 Brewster’s angle Brewster'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.

6 BPR optics diagram

7 Diode laser and Lens Single wavelength (6750 A)
Using two objective lens (5X and 80X) Forms a column of light before entering lens Cone shaped upon exit The 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 apart Each 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 polarized Easier to calculate rays on two planes.

11 S & P Polarizations P-polarized rays collected on B-array aligned // to X direction S-polarized rays collected on A-array aligned // to Y direction Profiles 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:
Film n1 r2 Cos(r2) Oxide 1.5 37 0.80 11574A Nitride 2 27 0.89 15340A PolySi 4 13 0.97 33751A ~ n1*8000A for once full cycle in profile Thickness = m*ni*8000A; m=# of cycle in profile

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