The high-throughput EBM-mask writer, EBM-8000P has been developed for mature node mask market. The EBM-8000P inherits basic architectures from the previous EBM-8000 system, i.e. electron optics with 50kV acceleration voltage, 400A/cm2 current density, variable shaped beam (VSB), and also, user interface such as JOB control system, mask handling system, which are equivalent to our latest single electron beam mask writers.
The EBM-8000P has two models, the EBM-8000P/H, which is equivalent to the conventional EBM-8000, and the EBM-8000P/M, which aims for high throughput.
The mask-writing throughput depends largely on the beam shot size and the current density, based on the generation of mask nodes. The EBM-8000P/M achieves high throughput and enough accuracy for 45-20 node by enlarging the maximum shot size while maintaining a current density of 400A/cm2.
Therefore, it is possible to achieve throughput that is 1.5 to 2 times faster than the conventional 70A/cm2 mask writer (such as EBM-6000) which is for 45-20nm node.
In the half pitch (hp) 16nm generation, the shot count on a mask is expected to become bipolar. The multi-patterning
technology in lithography seems to maintain the shot count around 300G shots instead of increase in the number of
masks needed for one layer. However, as a result of mask multiplication, the better positional accuracy would be
required especially in Mask-to-Mask overlay. On the other hand, in complex OPC, the shot count on a mask is expected
to exceed 1T shots.
In addition, regardless of the shot count forecast, the resist sensitivity needs to be lower to reduce the shot noise effect so
as to get better LER. In other words, slow resist would appear on main stream, in near future. Hence, such trend would
result in longer write time than that of the previous generations. At the same time, most mask makers request masks to
be written within 24 hours. Thus, a faster mask writer with better writing accuracy than those of previous generations is
With this background, a new electron beam mask writing system, EBM- 9000, has been developed to satisfy such
requirements of the hp 16nm generation. The development of EBM-9000 has focused on improving throughput for
larger shot counts and improving the writing accuracy.
EBM-9000 equipped with new features such as new electron optics, high current density (800A/cm2) and high speed deflection control has been developed for the 11nm technology node(tn) (half pitch (hp) 16nm). Also in parallel of aggressive introduction of new technologies, EBM-9000 inherits the 50kV variable shaped electron beam / vector scan architecture, continuous stage motion and VSB-12 data format handling from the preceding EBM series to maintain high reliability accepted by many customers. This paper will report our technical challenges and results obtained through the development.
Many lithography candidates, such as ArF immersion lithography with double-patterning/double-exposure techniques,
EUV lithography and nano-imprint lithography, show promising capability for 22-nm half-pitch generation lithography.
ArF immersion lithography with double-patterning/double-exposure techniques remains the leading choice as other
techniques still lack the conclusive evidence as the practical solution for actual production. Each of the prospective
lithography techniques at 22-nm half-pitch generation requires masks with improved accuracy and increased complexity.
We have developed a new electron beam mask writer, EBM-8000, as the tool for mask production of 22-nm half-pitch
generation and for mask development of 16nm half-pitch generation, which is necessary for the practical application of
these promising lithography technologies.
The development of EBM-8000 was focused on increasing throughput and improving beam positioning accuracy. Three
new major features of the tool are: new electron gun with higher brightness to achieve current density of 400 A/cm2,
high speed DAC amplifier to accurately position the beam with shorter settling time, and additional temperature control
to reduce the beam drift.
The improved image placement accuracy and repeatability, and higher throughput of EBM-8000 have been confirmed
by actual writing tests with our in-house tool.
We previously proposed a new method to correct critical dimension (CD) errors appearing in large-scale integrated circuit (LSI) fabrication processes, such as long range loading effect, local flare, and micro loading effect. The method provides high accuracy correction dimensions when using the pattern modulation method (method correcting CD errors by controlling figure sizes of LSI patterns). Now the case that several processes cause CD errors when a layer of an LSI pattern is fabricated on a wafer is discussed. These CD errors are corrected by generalizing the method proposed previously and taking the sequence of processes into account. It is shown from numerical calculation that the method can suppress the CD error to less than 0.01 nm with three iterations, under the condition that the maximum CD errors by micro loading effect and flare are 10 nm and 20 nm, respectively. It is strongly suggested that our methods will provide the necessary CD accuracies in the future.
In order to comply with the demanding technology requirements for 45 nm half pitch (HP) node (32 nm technology
node), Nuflare Technology Inc. (NFT) has developed Electron-beam mask writing equipment, EBM-6000, with
increased current density (70A/cm2), while its other primary features basically remain unchanged, namely 50 kV
acceleration voltage, Variable Shaped Beam (VSB)/vector scan, like its predecessors [1-5]. In addition, new
functionalities and capabilities such as astigmatism correction in subfield, optimized variable stage speed control,
electron gun with multiple cathodes (Turret electron gun), and optimized data handling system have been
employed to improve writing accuracy, throughput, and up-time. VSB-12 is the standard input data format for
EBM-6000, and as optional features to be selected by users, direct input function for VSB-11 and CREF-flatpoly
are offered as well.
In this paper, the new features and capabilities of EBM-6000 together with supporting technologies are reported to
solidly prove the viability of EBM-6000 for 45 nm HP node.