The application of phasefluid based intelligent fluids® in the field of photoresist stripping was studied. Due to their highly dynamic inner structure, phasefluids penetrate into the polymer network of photoresists and small gaps between resist layer and substrate and lift off the material from the surface. These non-aggressive stripping fluids were investigated regarding their efficiency in various resist stripping applications including initial results on copper metallization. Furthermore intelligent fluids® have been evaluated on an industry standard high volume single wafer cleaner. A baseline process on 300 mm wafers has been developed and characterized in terms of metallic and ionic impurities and defect level. Finally a general proof of concept for removal of positive tone resist from 300 mm silicon wafers is demonstrated.
Electron optics can assist in the fabrication of semiconductor devices in many challenges that arise from the ongoing decrease of structure size. Examples are augmenting optical lithography by electron beam direct write strategies and high-throughput imaging of patterned structures with multiple beam electron microscopes. We use multiple beam electron microscopy to image semiconductor wafers processed by electron beam lithography.
The usage of phase fluid based stripping agents to remove photoresists from silicon substrates was studied. Photoresists are required for many silicon based technologies such as MEMS patterning, 3D-Integration or frontend and backend of line semiconductor applications . Although the use of resists is very common, their successful integration often depends on the ability to remove the resist after certain processing steps. On the one hand the resist is changing during subsequent process steps that can cause a thermally activated cross-linking which increases the stripping complexity. Resist removal is also challenging after the formation of a hard polymer surface layer during plasma or implant processes which is called skin or crust . On the other hand the choice of stripping chemistry is often limited due to the presence of functional materials such as metals which can be damaged by aggressive stripping chemistries .
The usage of phasefluid based stripping agents to remove photoresists from silicon substrates was studied. Due to their highly dynamic inner structure phasefluids offer a new working principle, they are penetrating layers through smallest openings and lift off the material from the surface. These non-aggressive stripping fluids were investigated regarding their cleaning efficiency as well as contamination behavior to enable usage in semiconductor and MEMS manufacturing. A general proof of concept for the usage of phasefluids in resist stripping processes is shown on silicon coupons and BKM’s are given for different resist types. In addition a baseline process on 12inch wafers has been developed and characterized in terms of metallic and ionic impurities and defect level.
A dual hard mask concept for high resolution patterning has been evaluated with focus on highly selective etching processes for semiconductor manufacturing. The integration of thin SiO2 and ZrO2 hard mask materials enables highly selective patterning via plasma etch processes for future technology nodes. The patterning sequence is demonstrated for hole arrays with sizes down to 25 nm using a 50 nm thin resist which leads to the fabrication of trenches in silicon with aspect ratios up to 20:1. Alternative ZrO2 based materials were investigated with focus on surface roughness reduction since it influences the final line etch roughness. Here Si-doped ZrO2 (ALD) and spin-coatable ZrO2 were compared to the pure and crystalline ZrO2 as main selective material.
Using electron beam direct write (EBDW) as a complementary approach together with standard optical lithography at
193nm or EUV wavelength has been proposed only lately and might be a reasonable solution for low volume CMOS
manufacturing and special applications as well as design rule restrictions. Here, the high throughput of the optical litho
can be combined with the high resolution and the high flexibility of the e-beam by using a mix & match approach (Litho-
Etch-Litho-Etch, LELE). Complementary Lithography is mainly driven by special design requirements for unidirectional
(1-D gridded) Manhattan type design layouts that enable scaling of advanced logic chips. This requires significant data
prep efforts such as layout splitting.
In this paper we will show recent results of Complementary Lithography using 193nm immersion generated 50nm
lines/space pattern addressing the 32nm logic technology node that were cut with electron beam direct write. Regular
lines and space arrays were patterned at GLOBALFOUNDRIES Dresden and have been cut in predefined areas using a
VISTEC SB3050DW e-beam direct writer (50KV Variable Shaped Beam) at Fraunhofer Center Nanoelectronic
Technologies (CNT), Dresden, as well as on the PML2 tool at IMS Nanofabrication, Vienna. Two types of e-beam
resists were used for the cut exposure. Integration issues as well as overlay requirements and performance improvements
necessary for this mix & match approach will be discussed.