KEYWORDS: Optical alignment, Electron beam direct write lithography, Optical lithography, Metals, Semiconducting wafers, Process control, Signal detection, Electron beam lithography, Control systems, Silica
Techniques to introduce of electron beam direct writing (EBDW) technology into the volume production lines for the 65
nm process technology are shown and discussed. In order to apply these techniques in a harmonious way, partial
modifications to the current production line infrastructures are required, because those infrastructures have been
optimized for the conventional photolithography technology. One of the large differences is with the alignment. For the
gate layer, the appropriate solution is to have an additional process step to remove SiO2 material filled in the shallow
trench isolation alignment marks before the patterning. For the dual damascene process at the metal layers, careful
consideration of the choice between the indirect alignment or the direct alignment is necessary, when the metal layer is
aligned to the previous via layer underneath. We expect that these techniques can be used for the advanced node devices
as well, while some new structures would be applied on these devices. In addition to the optimizing the alignment mark
structures, the appropriate adjustment of EBDW system parameters by advanced process control (APC) is required, in
order to have enough overlay accuracy at the actual production use. Although such process control systems are normally
optimized to photolithography, we have confirmed that APC system can be also used for the EBDW technology for
appropriate overlay accuracy control. Furthermore, the alignment budget in our systems is created and the alignment
accuracy in our future system is estimated based on it. Based on the findings from these discussions, we expect that the EBDW with e-beam-only alignment will be applicable for the production of the 11 nm half-pitch process technology node and the beyond.
KEYWORDS: Optical alignment, Electron beam direct write lithography, Electron beams, Overlay metrology, Control systems, Semiconducting wafers, Metals, Back end of line, Backscatter, Electron beam lithography
Techniques to appropriately control the key factors for a character projection (CP) based electron beam direct writing technology for mass production are shown and discussed. In order to achieve accurate CD control, the CP technique using the master CP is adopted. Another CP technique, the Packed CP, is used to obtain suitable shot count. For the alignment on the some critical layers which normally have an even surface, the process removing SiO2 material filled in the alignment marks is added and then the alignment marks can be detected using electron beam. The proximity effect correction using the simplified electron energy flux model and the hybrid exposure are used to obtain enough process margins. As a result, the sufficient CD accuracy, overlay accuracy, and yield are obtained on the 65 nm node device. Due to the proper system control, more than 10,000 production wafers have been successfully exposed so far without any major system downtime. It is shown that those techniques can be adapted to the 32 nm node production with slight modifications. It is expected that by using the Multi Column Cell exposure method, those techniques will be applicable to the rapid establishment for the 14 nm node technology.
We investigated a high-resolution chemically amplified resist for introducing a multi-column cell electron-beam directwriting
system into the manufacturing of sub-14 nm technology node LSIs. The target of total blur, which leads to an
exposure latitude above 10%, is less than 13.6 nm for 14 nm logic node LSIs. We divided the total blur into three terms,
forward-scattering, electron-beam and resist. At a 40 nm-thick resist, the forward-scattering blur was calculated as 1.0
nm in lithography simulation, and beam blur was estimated to be 7.1 nm from the patterning results of hydrogen
silsesquioxane. We found that there is a proportional relation between resist blur and acid diffusion length by using a
new evaluation method that uses a water-soluble polymer. By applying a chemically amplified resist with a short acid
diffusion length, resist blur decreased to 14.5 nm. Even though total blur is still 16.2 nm, we have already succeeded in
resolving 20 nm line and space patterns at an exposure dose of 79.6 μC/cm2.
KEYWORDS: Electron beam direct write lithography, Optical alignment, Electron beams, Control systems, Semiconducting wafers, Overlay metrology, Metals, Photoresist processing, Backscatter, Electron beam lithography
Techniques to appropriately control the key factors for a character projection (CP) based electron beam direct writing
(EBDW) technology for mass production are shown and discussed. In order to achieve accurate CD control, the CP
technique using the master CP is adopted. Another CP technique, the Packed CP, is used to obtain suitable shot count.
For the alignment on the some critical layers which have the normally an even surface, the alignment methodology differ
from photolithography is required. The process that etches the SiO2 material in the shallow trench isolation is added and
then the alignment marks can be detected using electron beam even at the gate layer, which is normally on an even
surface. The proximity effect correction using the simplified electron energy flux model and the hybrid exposure are used
to obtain enough process margins. As a result, the sufficient CD accuracy, overlay accuracy, and yield are obtained on the
65 nm node device. The condition in our system is checked using self-diagnosis on a regular basis, and scheduled
maintenances have been properly performed. Due to the proper system control, more than 10,000 production wafers have
been successfully exposed so far without any major system downtime. It is shown that those techniques can be adapted
to the 32 nm node production with slight modifications. For the 14 nm node and beyond, however, the drastic increment
of the shot count becomes more of a concern. The Multi column cell (MCC) exposure method, the key concept of which
is the parallelization of the electron beam columns with a CP, can overcome this concern. It is expected that by using the
MCC exposure system, those techniques will be applicable to the rapid establishment for the 14 nm node technology.
T. Maruyama, M. Takakuwa, Y. Kojima, Y. Takahashi, K. Yamada, J. Kon, M. Miyajima, A. Shimizu, Y. Machida, H. Hoshino, H. Takita, S. Sugatani, H. Tsuchikawa
When manufacturing prototype devices or low volume custom logic LSIs, the products are being less profitable
because of the skyrocketing mask and design costs recent technology node. For 65nm technology node and beyond, the
reduction of mask cost becomes critical issue for logic devices especially. We attempt to apply EBDW mainly to
critical interconnect layers to reduce the mask expenditure for the reason of technical output reusability.
For 65nm node production, new 300mm EB direct writer had been installed. The process technologies have also
been developing to meet sufficient qualities and productivities.
The impact of alicyclic protective groups on acid-labile substituents in a vinylphenol-methacrylate-based chemically amplified positive resist was investigated. The resist consists of the copolymer of vinylphenol and adamantyl methacrylate (VP/AdMA) with triflate onium salt as a photo- acid generator. The alicyclic protective groups in our system show a higher reactivity and higher hydrophobicity than those of the tert-butyl group, which is widely used in chemically amplified resists. The resists containing the alicyclic protective group resolved 0.09-micrometer hole patterns at 6 (mu) C/cm2, and a resist with a base additive resolved 0.12-micrometer line and space patterns at 9.0 (mu) C/cm2 using a 50-keV EB lithography system with a 2.38% TMAH aqueous solution as the developer. The dry etching durability of resists containing the alicyclic group was also compared with resists containing the tert-butyl group and with polyvinylphenol (PVP). The dry etching durability of our resists for a C4F8 plasma was 1.3 times superior to that of resist containing the tert-butyl group, and 1.1 times better than that of PVP. This means the thickness of film in pattern fabrication can be reduced to obtain a higher sensitivity and higher resolution.
The effect of an alkali decomposable additive on a chemically amplified (CA) positive electron-beam (EB) resists was studied. HalogenoMethylEster (HME), 1,4- bis(bromoacetoxy) benzene was synthesize and used as an alkali decomposable additive. The hydrophobic HME decomposed with an alkali solution and changed into a hydrophilic, which in turn increased the alkali dissolution rate of the exposed region of the resist and enhanced the resist contrast. In addition, the bromomethyl groups and ester groups are hydrolyzed with a high degree of polarity change. HME having the large dissolution acceleration effect at an exposed region is suitable for application as a positive resist. HME was added to 2-component CA positive EB resist consisting of a base polymer and a photoacid generator. As a result of a high degree of polarity change, HME enhanced the resist contrast with no loss in sensitivity. The delineation of a fine 0.13 micrometers hole-pattern was possible with the addition of HME. The addition of HME rendered the sidewalls smooth and vertical.
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