While I admire your enthusiasm, it is highly unlikely that you can build, even low resolution, integrated circuits without a fairly large capital investment (probably a minimum of tens, if no hundreds, of thousands of dollars). The process requires a number of steps, each of which reqires specialized equipment, high purity (possibly poisonous) materials and a high degree of accuracy and precision.
Here is a web page that gives a quick overview of the IC manufacturing process:
If you would like an interesting and challenging next step in your hobby, you could either 1) try making multi-layer circuit boards, or
2) start working with FPGAs.Multi-layer circuit boards will move you a step closer to the IC manufacture process (ICs require several layers to be built up on a silicon wafer: at least, for PNP type devices, a P-type substrate, a set of N-type regions in the substrate, another set of P-type regions in the N-type regions, an insulating layer on top of the entire thing and, finally, a metal interconnect layer between PNP devices).
FPGAs give you the chance to construct actual chips that can compete with relatively modern custom devices (you can get, with carefull design, devices operating in the tens of megahertz). While this has little to do with the physical challenges of building ICs, it gives you the chance to experience some of the logical design challenges.