Specific Process Knowledge/Lithography/Coaters/Spin Coater: RCD8 processing: Difference between revisions
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The spin-off cycle determines the thickness of the resist coating. The thickness is primarily a function of the spin-off speed and the spin-off time, both following an inverse power-law (y=k*x<sup>-a</sup>). The acceleration to the spin-off speed also influences the thickness, but the effect is dependent on previous steps. The spin-off is usually a simple spin at one speed, but it may be comprised of several steps at different spin speeds. After spin-off, the wafer is decelerated. | The spin-off cycle determines the thickness of the resist coating. The thickness is primarily a function of the spin-off speed and the spin-off time, both following an inverse power-law (y=k*x<sup>-a</sup>). The acceleration to the spin-off speed also influences the thickness, but the effect is dependent on previous steps. The spin-off is usually a simple spin at one speed, but it may be comprised of several steps at different spin speeds. After spin-off, the wafer is decelerated. | ||
The coated thickness, t, as a function of the spin-off speed, w, follows an inverse power-law, t=k*w<sup>-a</sup>. The constant, k, is a function of the resist viscosity and solid content, and the spin-off time. The exponent, a, is dependent on solvent evaporation, and is usually ~½. This means that from the thickness | The coated thickness, t, as a function of the spin-off speed, w, follows an inverse power-law, t=k*w<sup>-a</sup>. The constant, k, is a function of the resist viscosity and solid content, and the spin-off time. The exponent, a, is dependent on solvent evaporation, and is usually ~½. This means that from the thickness t<sub>1</sub> achieved at spin speed w<sub>1</sub>, one can estimate the thickness t<sub>2</sub> at spin speed w<sub>2</sub> using the relation: <br> t<sub>1</sub>*w<sub>1</sub><sup>2</sup> = t<sub>2</sub>*w<sub>2</sub><sup>2</sup> => t<sub>2</sub> = t<sub>1</sub> * w<sub>1</sub><sup>2</sup>/w<sub>2</sub><sup>2</sup>. <br> For SU-8, however, a is observed to be ~1 (probably due to the low solvent content and/or the formation of skin). In this case, the relation simply becomes: <br> t<sub>1</sub>*w<sub>1</sub> = t<sub>2</sub>*w<sub>2</sub> => t<sub>2</sub> = t<sub>1</sub> * w<sub>1</sub>/w<sub>2</sub>. <br> | ||
=Automatic dispense= | =Automatic dispense= | ||