Effect of temperature on photoresist critical dimension during puddle development

We have investigated the effect of a temperature change on photoresist critical dimension (CD) in a wafer during puddle development. The wafer temperature was decreased by the evaporation latent heat of developer solution during puddle development, and the rate of temperature decrease of the peripheral area was higher than that of the central area in the wafer. The temperature of the peripheral area was approximately 1.3°C lower than that of the central area after 60 s. The temperature distribution was caused by the difference in heat capacitance in the wafer, which was mainly influenced by the wafer chuck. We investigated the influence of temperature on photoresist CD in the wafer, using a diazonaphthoquinone (DNQ)/novolac photoresist. Photoresist CD changed with temperature at a rate of approximately 5nm/°C, and the CD of the peripheral area became smaller than that of the central area over time. We can improve the CD distribution by controlling the temperature during puddle development or by using a photoresist with a dissolution rate that is less sensitive to temperature.