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Nitrogen implantation of Mo gate was used to fabricate MOS capacitors and CMOS transistors. Initial studies demonstrate that the work function of Mo is sensitive to nitrogen implantation energy. Mo with (110) orientation exhibits a high work function, making it suitable for bulk p-MOSFET gate electrodes. Nitrogen implantation can be used to lower the Mo work function, making it suitable for n-MOSFET gate electrodes. A gate work function reduction of 0.42 eV was achieved for the n-FETs on CMOS wafers. With further optimization, this single metal gate technology may potentially replace conventional poly-Si gate technology for CMOS and can also be used for multipletechnologies.

In this letter, we propose a new metal-gate CMOS technology that uses a combination of two metals to achieve low threshold voltages for both n-and p-MOSFET's. One of the gate electrodes is formed by metal interdiffusion so that no metal has to be etched away from the gate dielectric surface. Consequently, this process does not disturb the delicate thin gate dielectric and preserves its uniformity and integrity. This new technology is demonstrated for the Ti-Ni metal combination that produces gate electrodes with 3.9 eV and 5.3 eV work functions for n-MOS and p-MOS devices respectively.