for 2 minute to partially dry the solvent transferred to a 400 u00b0 c hot plate for 2 minutes and then transferred to a 430 u00b0 c hot plate for 2 minutes the time and temperature schedule should be sufficient to render the film insoluble and burnout sacrificial porogen near the surface the wafer is then allowed to cool and was returned to the spinner at 28 a solution of hosp u2122 diluted to achieve a film thickness of 250 a u00b0 at a spin speed of 3000 rpm is applied to the wafer and spun at 3000 rpm for 30 seconds to produce etch stop layer 7 fig1 after spinning at 30 third hot plate bake the wafer is placed on a hot plate at 150 u00b0 c for 2 minute to partially dry the solvent it is then moved to a 400 u00b0 c hot plate for 2 minutes to partially crosslink the film this time and temperature is sufficient to render the film insoluble at 32 a second layer of porous silk is applied in a manner similar to the first layer to produce layer 9 fig1 porous silk is applied to the wafer and the wafer is spun at 3000 rpm for 30 seconds at 34 fourth hot plate bake the wafer is placed on a 150 u00b0 c hot plate for 2 minute to partially dry the.