Two different pattern curing techniques were developed to stabilize first lithographic images for the single-etch double
patterning process. The first method uses a surface curing agent (SCA) that is coated on top of the patterned surface to
form a protective coating layer during the curing bake process. It was found that the surface curing process with SCA
offers minimum CD changes before and after the double patterning process. Virtually no CD change was observed with
the first lithographic images at various curing bake temperatures ranging from 120 ~160°C indicating the curing reaction
is limited on the patterned surface. The second method uses a thermal cure resist (TCR) that is a special 193nm
photoresist with a crosslinkable functional group to form an insoluble network upon heating at higher temperature. A
single-step curing process of the first lithographic images was achieved using TCR by baking the patterned images at
180°C for 60sec. A cross-line contact hole double patterning method was used to evaluate these two different curing
techniques and both SCA and TCR successfully demonstrated their capability to print 45nm contact holes with excellent
CD uniformity in immersion lithography (1.35NA) with a 45nm half pitch mask. It was also confirmed that both SCA
and TCR can be extended to the top-coat free immersion double patterning process using an embedded barrier layer
Optics contamination is a concern for extreme ultraviolet (EUV) lithography. To protect EUV optics, all materials used
in EUV vacuum exposure chambers must be screened prior to use. Photoresists are a concern since a freshly coated
wafer will be introduced into the chamber approximately every minute in a high volume production tool. SEMATECH
and the International EUV Initiative (IEUVI) have begun a resist outgassing benchmarking experiment to compare
different outgassing methodologies. Samples of the same batch of resist were sent to eight researchers. The results show
a large variation of four orders of magnitude in the amount of measured outgassing products. The next steps are to
correlate outgassing measurements to witness plate experiments.
In this study we investigate the pattern collapse mechanism of dense patterns with resolution under 60nm printed in Extreme Ultra Violet (EUV-IL) and Electron Beam Lithographies (EBL). Pattern collapse occurs when physical properties of the material can't imbalanced the capillary force exerted on the pattern during the drying of the rinse liquid. In former simulation models, the height of the pattern at which collapse occurs (critical height, Hc) was predicted using either elastic deformation properties, or plasticizing limit value of the resist. Experimental observations of unstuck patterns, lead us to develop 2 new models considering the adhesion properties of the resist film on the substrate. By comparing simulated to experimental results for varying pattern pitchs printed in 2 Chemically Amplified Resists (CARS), we show that pattern collapse behaviour of EUV-IL and EBL patterns is not only ruled by rigidity or strength of the resist but can be perfectly described with equation defining the unsticking of a non bending pattern. Finally by using surfactinated solution on sub-60nm dense patterns, great improvements in Hc values and increase of process window latitude are shown. However, due to larger capillary force, this efficiency decreases with pattern pitch and appears limited on patterns width smaller than 40 nm.
Future lithography tools will have to address the 32 nm node. EUV lithography at 13.4 nm wavelength is the technology that may achieve such resolution if chemically amplified EUV resists show high enough resolution capabilities. However for sub 100 nm line width patterns, the pattern collapse, generated during the drying step of the developing process, becomes a serious limiting phenomenon. We performed ultra high resolution exposures of EUV positive chemically amplified resists using either electron beam lithography (EBL), or EUV interferometry Lithography (IL) produced in a synchrotron. Two theoretical models have been compared with experimental results. One is mainly dealing with adhesion failure and the other with the line deformation. Adhesion failure occurs when capillarity pressure on the pattern become stronger than the attractive Van der Walls forces assuring the pattern adhesion on the substrate. Mechanical failure occurs once the lines deflection exceeds the mechanical breaking resistance of the resist. We highlighted that pattern collapse mode depends on resist thickness. Collapsing of patterns with thickness>100 nm are properly fitted with the deformation model of the resist; whereas for pattern height under 60 nm, experimental results obtained by EUVIL and EBL are properly predicted with the adhesion failure model. To push resolution further and avoid pattern collapse, we targeted to expose sub 100 nm thick resist films. AFM3D measurements on EBL patterns show that reducing the resist thickness increases their top Line Width Roughness (LWR) testifying of physical resist properties variations in the resist interfacial layers. However we pointed out an optimum resist thickness, hence an optimal dilution. By tuning developer normality and puddle time, straight resist profiles were obtained. Finally we reached dense 40/40 nm lines in XP9947W150 resist using both exposure tools and validate the process compatibility with future etching steps by transferring 40/40 nm dense lines patterned with EBL into a metallic hard mask.
Resist poisoning is one of the key issues linked to low-k dielectric and copper integration. This phenomenon tends to be amplified in dual damascene architecture, where both processes and materials are incriminated, especially when porous low-k dielectrics are integrated. In this paper we present and implement the dose to clear compensation method, easily undertaken with standard lithography and metrology tools, to evaluate quantitatively 248 and 193nm photo-resist poisoning on both MSQ and porous MSQ substrates. We show the amplification of resist poisoning due to the reservoir effect in porous MSQ, and address the role of the porosity in the phenomenon. We demonstrate the efficiency of the method in evaluating hard masks compatibility, wet and dry stripping processes, and its ability in screening photo-resist in term of poisoning sensitivity.