Within the EU FP7 program MAGIC, Fraunhofer CNT was involved in the development of maskless lithography (known as “ML2”) tools based on multibeam principles and their integration into CMOS manufacturing. CNT’s project partner IMS Nanofabrication developed a high-energy ML2 approach known as PML2 (Projection Maskless Lithography) using up to 250.000 electron beams in parallel (figure 1). In 2010, the last year of the MAGIC project, we demonstrated in collaboration with Globalfoundries and IMS Nanofabrication (Vienna, Austria) a possible future patterning approach for the 22 nm technology node and beyond: “Complementary Patterning”.

Yan Borodovsky of Intel was the first who coined this term. He presented a realistic solution of a combination of optical 193 nm immersion/EUV lithography and EBDW at the LithoVision Symposium. Silicon gratings of 50 nm half pitch on 300 mm wafers were provided by Globalfoundries. The resist mask was patterned by optical 193 nm immersion lithography using quadrupole illumination. The resist features were transferred into the silicon bulk via a standard hard mask. The result of this first silicon etch step can be seen in figure 2.
At Fraunhofer CNT the pre-structured wafers were coated using a special HSQ resist process which allows a smooth capping and void-less filling of the silicon grating. HSQ coated 300 mm wafers were sent to IMS Nanofabrication to be exposed using the PML2 Alpha tool, and compared to exposures on Vistec SB3050DW at CNT. The layout to cut the lines was designed by Fraunhofer CNT. It basically simulates a realistic SRAM or logic Metal interconnect layer to be cut gaps, vias or contacts into 1-D GDR (one-dimensional gridded design rule) lines. The result of the second Litho step is shown at the center of figure 2.
After e-beam lithography the wafers were cleaned and etched at Fraunhofer CNT using advanced Ar/NF3 based plasma process in a magnetically enhanced reactive ion etching (MERIE) chamber gaining an etching selectivity HSQ:Si of about 1:10. The cross-sectional view on a small cut hole clearly shows sufficient etching depth. In conclusion, Fraunhofer CNT, Globalfoundries and IMS Nanofabrication successfully demonstrated the feasibility of complementary patterning using 193i lithography and multi-EBDW in a mix-and-match approach.