Comparison between equilibrium cooling and thermal shock

摘要

One of the harsh environments that a photoresist experiences is that of cold temperature. Cooling a photoresist coating constrained on a substrate often results in a sizable stress. This stress is important to understand since it is the driving force for coating failure. A membrane deflection technique was used to measure the stress of a photoresist coating as a function of temperature. The resulting stress was compared to the ultimate properties as a function of sub-ambient temperature. It is shown that failure occurred when the cooling stress exceeded the ultimate strength. Cooling over a temperature range of 30 to 65$DGR@C was performed slowly (over a period of 6 hours) as well as suddenly (simulating a thermal shock). Using an incremental elastic approach a relationship between equilibrium cooling and thermal shock is presented. This relationship between stresses associated with equilibrium cooling and thermal shock is used to describe the typical decrease in mechanical performance of coatings in a thermal shock environment.