Pitch Dependence of Linewidth in the 0.25 µm Patterns Fabricated Using Positive Chemically Amplified Resist

We investigated the proximity bias characteristic of 0.25 µ m patterns used with three types of positive chemically amplified resists of differing material and properties. To determine the proximity bias characteristics, we examined how the relationship between the pitch and the linewidth varies with post-exposure-bake (PEB) temperature and time. Our experiment revealed that each resist exhibits its own unique proximity bias characteristics. We also found that the proximity bias characteristics of the three resists depended to a large extent on the PEB temperature: the lower the PEB temperature, the greater the resemblance of the proximity bias characteristics to the optical characteristic. Considering this and using the pitch vs. linewidth curve with PEB time as a parameter, we concluded that the proximity bias characteristic of resists largely depends on the diffusion of acids and other thermal effects in the resists. These characteristics resemble optical characteristics as the PEB temperature decreases, the acids diffuse to a lesser extent, and the thermal effects decrease.