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^-a). 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^-a). 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^-a. 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 t1 achieved at spin speed w1, one can estimate the thickness t2 at spin speed w2 using the relation: <br> t1*w1^2 = t2*w2^2 => t2 = t1 * w1^2/w2^2. <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> t1*w1 = t2*w2 => t2 = t1 * w1/w2. <br> | The coated thickness, t, as a function of the spin-off speed, w, follows an inverse power-law t=k*w^-a. 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 t1 achieved at spin speed w1, one can estimate the thickness t2 at spin speed w2 using the relation: <br> t1*w1^2 = t2*w2^2 => t2 = t1 * w1^2/w2^2. <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> t1*w1 = t2*w2 => t2 = t1 * w1/w2. <br> | ||
=Automatic dispense= | =Automatic dispense= | ||