Multilayer hardmask (MLHM) schemes have been implemented as an indispensable process for ArF lithography which
continues to demand thinner photoresist films. There are many variations of MLHM and semiconductor manufacturers
choose to adopt their own designs, depending on their specific needs and technical advances. The quad-layer stack
consisting of photoresist, organic ARC, CVD Si hardmask, and spin-on carbon underlayer is one of them. Despite the
need for wafer transporting between the spin track and CVD equipment, this scheme is attractive because it can avoid
laborious elaboration of sophisticated etching chemistries for spin-on Si-ARC and carbon underlayer. One of the issues
arising from the mixed film forming process is the thermal stability of carbon underlayer at high temperatures during the
CVD process of the Si hardmask. Organic underlayer which shows high thermal stability is crucial for this mixed
hardmask process. These types of thermally stable organic film can also be used for other applications such as the spacer
patterning technique for pitch size shrinkage. In this paper, we discuss the development of organic resins with high
thermal stability, their physical properties, and their lithographic behaviors in the MLHM schemes.
Amorphous Carbon Layer (ACL) and SiON system has been proven to be a good hardmask
combination. These layers are formed by a high cost, low throughput CVD process. This paper discloses a
reliable, low cost, high throughput process using a simple spin on layer structure. Through manipulation of
various parameters, additional BARC layer is eliminated and the process is further simplified to a tri-layer
structure. Also, PR/SiON/C-SOH (Carbon-Spin-On-Hardmask) system has been compared to PR / Si-SOH
(Si-Spin-On-Hardmask ) / C-SOH system and found their performances are comparable. This indicates the
PR / Si-SOH / C-SOH process is an economical yet comparable substitute.
In recent microlithography of semiconductor fabrication, spin-on hardmask (SOH) process continue to gain popularity as it replaces the traditional SiON/ACL hardmask scheme which suffers from high CoO, low productivity, particle contamination, and layer alignment issues. In the SOH process, organic polymer with high carbon content is spin-cast to form a carbon hardmask film. In the previous papers, we reported the development of organic SOH materials and their application in sub-70 nm lithography. In this paper, we describe the synthesis of organic polymers with very high carbon contents (>92 wt.%) and the evaluation of the spin-coated films for the hardmask application. The high carbon content of the polymer ensures improved etch resistance which amounts to >90% of ACL's resistance. However, as the carbon content of the polymers increases, the solubility in common organic solvents becomes lower. Here we report the strategies to improve the solubility of the high carbon content resins and optimization of the film properties for the SOH application.
In recent years for memory devices under 70nm using ArF lithography, spin-on organic hardmask has become an
attractive alternative process to amorphous carbon layer hardmark (ACL) in mass production due to ACL hardmask's
limited capacity, high cost-of-ownership, and low process efficiency in spite of its excellent etch performance. However,
insufficient plasma etch resistance of spin-on hardmask makes the etch process an issue resulting in inadequate vertical
profiles, large CD bias, and narrow etch process window compared to ACL hardmask. In order to be able to apply these
spin on hardmasks to varies layers including critical layers, the aforementioned problems need to be resolved and
verified using several evaluation methods including etch pattern evaluation. In this paper, we report the synthesis of
novel organic spin-on hardmasks (C-SOH) that incorporate various fused aromatic moieties into polymer chain and the
evaluation of etch performance using dry etch tools. Organic spin-on hardmasks with 79-90 wt% carbon contents were
synthesized in-house. Oxygen and fluorine based plasma etch processes were used to evaluate the etch resistance of the
C-SOH. The results show our 3rd generation C-SOH has etch profiles comparable to that of ACL in a 1:1 dense pattern.
In ArF lithography for < 90nm L/S, amorphous carbon layer (ACL) deposition becomes inevitable process because thin
ArF resist itself can not provide suitable etch selectivity to sub-layers. One of the problems of ACL hardmask is surface
particles which are more problematic in mass production. Limited capacity, high cost-of-ownership, and low process
efficiency also make ACL hardmask a dilemma which can not be ignored by device makers. One of the answers to these
problems is using a spin-on organic hardmask material instead of ACL hardmask. Therefore, several processes including
bi-layer resist process (BLR), tri-layer resist process (TLR), and multi-layer resist process (MLR) have been investigated.
In this paper, we have described spin-on organic hardmask materials applicable to 70nm memory devices. Applications
to tri-layer resist process (TLR) were investigated in terms of photo property, etch property and process compatibility.
Based on the test results described in this paper, our spin-on hardmask materials are expected to be used in mass