In some implementations, a method of fabricating an integrated circuit includes obtaining first data for a first chip containing a first version of the integrated circuit, determining that a transistor should be coupled with another transistor, selecting one or more masks for coupling the transistor with the other transistor to adjust the threshold voltage of the transistor, obtaining second data for a second chip containing a second version of the integrated circuit, determining that the second version of the integrated circuit meets one or more requirements, and preparing a final integrated circuit design for production based on the second version of the integrated circuit.