Photoresist adhesion effect of resist reflow process

Making a sub-100nm contact hole pattern is one of the difficult issues in the semiconductor process. Compared with another fabrication process, the resist reflow process is a good method of obtaining a very high resolution contact hole. However, it is not easy to predict the actual reflow result by simulation because very complex physics and chemistry are involved in the resist reflow process. We must know accurate physical and chemical constant values and many fabrication variables for better prediction. We made a resist reflow simulation tool to predict approximate resist reflow as functions of pitch, temperature, time, and array, among others. We were able to observe the simulated top view, side view, and changed hole size. We used the Navier-Stokes equation for resist reflow. We varied the reflow time, temperature, surface tension, and three-dimensional volume effect of our old model. However, photoresist adhesion is another very important factor that was not included in the old model. Thus, the adhesion effect was added on the Navier-Stokes equation, and such a case showed distinct differences in the reflowed resist profile and contact hole width from the case of the no adhesion effect.