Extreme ultraviolet lithography (EUVL, λ = 13.5 nm) continues to be one of the most important candidates for future technology nodes. For the insertion of EUV lithography into device mass production, higher sensitivity of EUV resists is helpful for better cost of ownership of the EUV tool and light source. However, obtaining low sensitivity (S), high resolution (R), and low line edge roughness (L) simultaneously is very difficult. Many previous experiments by lithographers proved the existence of this "RLS trade-off"1-2. This paper furthers the work related to Photosensitized Chemically Amplified ResistTM (PSCAR)TM**, a chemistry which is trying to break the "RLS tradeoff" relationship. This chemistry was introduced as a new chemically amplified lithographic concept and is accomplished in an in-line track tool with secondary exposure module connected to EUV exposure tool.
PSCAR is a modified CAR which contains a photosensitizer precursor (PP) in addition to other standard CAR components such as a protected polymer, a photo acid generator (PAG) and a quencher. In the PSCAR process, an improved chemical gradient can be realized by dual acid quenching steps with the help of increased quencher concentration. The addition of the PP, as well as other material optimization, offers more degrees of freedom for getting high sensitivity and low LER, but also makes the system more complicated. Thus coupling simulation and experimentation is the most rational approach to optimizing the overall process and for understanding complicated 2-D structures.
In this paper, we will provide additional background into the simulation of PSCAR chemistry, explore the effects of PSCAR chemistry on chemical contrast of complex structures (e.g. T structures, slot contacts, I/D bias for L/S), and explore the sensitivity enhancement levels capable while improving or maintaining lithographic performance. Finally, we will explore modifications of PSCAR chemistry on performance.
A new type of Photosensitized Chemically Amplified Resist (PSCAR) **: “PSCAR 2.0,” is introduced in this paper. PSCAR 2.0 is composed of a protected polymer, a “photo acid generator which can be photosensitized” (PS-PAG), a “photo decomposable base (quencher) which can be photosensitized” (PS-PDB) and a photosensitizer precursor (PP). With this PSCAR 2.0, a photosensitizer (PS) is generated by an extreme ultra-violet (EUV) pattern exposure. Then, during a subsequent flood exposure, PS selectively photosensitizes the EUV exposed areas by the decomposition of a PS-PDB in addition to the decomposition of PS-PAG. As these pattern-exposed areas have the additional acid and reduced quencher concentration, the initial quencher loading in PSCAR 2.0 can be increased in order to get the same target critical dimensions (CD). The quencher loading is to be optimized simultaneously with a UV flood exposure dose to achieve the best lithographic performance and resolution. In this work, the PSCAR performance when different quenchers are used is examined by simulation and exposure experiments with the 16 nm half-pitch (HP) line/space (L/S, 1:1) patterns. According to our simulation results among resists with the different quencher types, the best performance was achieved by PSCAR 2.0 using PS-PDB with the highest possible chemical gradient resulting in the lowest line width roughness (LWR). PSCAR 2.0 performance has furthermore been confirmed on ASML’s NXE:3300 with TEL’s standalone pre-alpha flood exposure tool at imec. The initial PSCAR 2.0 patterning results on NXE:3300 showed the accelerated photosensitization performance with PS-PDB. From these results, we concluded that the dual sensitization of PS-PAG and PS-PDB in PSCAR 2.0 have a potential to realize a significantly improved resist performance in EUV lithography.
Defect reduction has become one of the most important technical challenges in device mass-production. Knowing that
resist processing on a clean track strongly impacts defect formation in many cases, we have been trying to improve the
track process to enhance customer yield. For example, residual type defect and pattern collapse are strongly related to
process parameters in developer, and we have reported new develop and rinse methods in the previous papers. Also, we
have reported the optimization method of filtration condition to reduce bridge type defects, which are mainly caused by
foreign substances such as gels in resist. Even though we have contributed resist caused defect reduction in past studies,
defect reduction requirements continue to be very important. In this paper, we will introduce further process
improvements in terms of resist defect reduction, including the latest experimental data.
On the device manufacturing, the film edge control around the wafer edge has been critical at the point of edge
control of deposited film. So far, the film edge control is operated by the wafer edge exposure system and/or the
edge beam remover. The immersion lithography which is applied to the device generation below 65 nm node
requires more additional and severe items for film edge control. These typical requirements are position control of
coating film and wafer bevel cleanness. For examples, top coat film is widely applied to the immersion lithography.
But this topcoat film is easily peeled off, if top coat film edge should be directly located on the wafer substrate like
Si wafer. Thus, the edge position of topcoat film must be controlled very carefully. And the particle or residues on
the wafer bevel is thought to be one of the causes to generate immersion defect. Wafer bevel must be clean in order
to reduce the immersion defect.
Then we have developed novel application technology in order to solve these kinds of immersion defectivities.
This new application technology is based on rinse solution technology and new hardware concept. This new
application technology can control the edge position of coating film with high accuracy and can reduce the particle
We show the edge position accuracy using our application technology and furthermore, the stability of edge
position accuracy in case of multi-layered resist process. We also show the cleanness of the wafer bevel area at the
same time. And we can achieve the immersion process with wide process latitude with innovative application