Takayuki Ohnishi

Mask process correction (MPC) modeling and its application to EUV mask for electron beam mask writer EBM-7000

In electron beam writing on EUV mask, it has been reported that CD linearity does not show simple signatures as observed with conventional COG (Cr on Glass) masks because they are caused by scattered electrons form EUV mask itself which comprises stacked heavy metals and thick multi-layers. To resolve this issue, Mask Process Correction (MPC) will be ideally applicable. Every pattern is reshaped in MPC. Therefore, the number of shots would not increase and writing time will be kept within reasonable range. In this paper, MPC is extended to modeling for correction of CD linearity errors on EUV mask. And its effectiveness is verified with simulations and experiments through actual writing test.

Recent progress of magnetocaloric effect and magnetic refrigerant materials of Mn compounds (invited)

Magnetocaloric and related properties of Ru and Ni substituted (MnFe)2(PSi) are presented. It is found that Ru and Ni are effective doping elements to reduce the thermal hysteresis of (MnFe)2(PSi). The origin of the thermal hysteresis is discussed on the basis of a thermodynamic model. It is shown that the elastic energy is responsible for the thermal hysteresis. We also show recent developments of the production process of Mn compounds in an industrial scale.

Tuning the Curie temperature and thermal hysteresis of giant magnetocaloric (MnFe)2PX (X = Ge and Si) compounds by the Ru substitution

Effects of the Ru substitution on magnetocaloric properties have been studied for MnFeP0.8Ge0.2 and Mn1.2Fe0.8P0.5Si0.5. The parent compounds undergo a first-order magnetic transition near room temperature accompanied by a large thermal hysteresis, , of about 10 K. The substitution of 10–15 at. % of Ru reduces down to 2–3 K. On the other hand, a sharp magnetic transition is preserved by the Ru substitution up to 15% and, as a result, a large magnetic entropy change and a small are achieved. It is found that the refrigerant capacity of the Ru substituted compounds is 1.6–1.8 times as large as that of Gd. These results have proved that the Ru substitution is an effective method to realize Mn-based magnetic refrigerant materials.

Vibrational Stimulated Raman Emission from Dibromomethane as Seed Beam for Four-Wave Rotational Raman Mixing in Hydrogen.

A portion of Nd:YAG laser emission is used as a pump beam for neat dibromomethane to generate vibrational stimulated Raman emission emitting at a Raman shift frequency of 588 cm-1. This beam is aligned to be collinear with the other portion of the pump beam and is used as a seed beam for the generation of numerous rotational stimulated Raman emissions of hydrogen with a Raman shift frequency of 587 cm-1. Because their Raman shift frequencies coincide, a multifrequency laser emission consisting of many rotational lines, in addition to vibrational lines, is generated by four-wave rotational Raman mixing.

Key improvement Schemes of Accuracies in EB Mask Writing for Double Patterning Lithography

Double pattering or exposure methodologies are being adopted to extend 193nm optical lithography. These methodologies require much tighter image-placement accuracy and Critical Dimension (CD) controls on mask than the conventional single exposure technique. Our experiments indicate that the global image placement drift induced by the time elapsed in mask writing is the dominant factor that degrades image-placement accuracy. In-situ grid measurement method is being proposed to suppress this time dependent drift. Resist charging effect is also an important error factor. While it can be reduced by charge dissipation layer (CDL), further feasibility study is required for using CDL to overcome certain side-effects pertaining to CDL. High dose resist improves local CD uniformity and pattern fidelity. However, mask writing time becomes longer with lower sensitivity. To satisfy conflicting issues, throughput and CD uniformity, high sensitivity CAR which has short acid diffusion length is desirable. Shortening acid diffusion length is essential for achieving good pattern resolution as well as good CD uniformity. This paper will address the results of error source analyses and key schemes of accuracy improvements in photo-mask manufacturing using NuFlare Technologys EB mask writers.

Performance and stability of mask process correction for EBM-7000

In order to support complex optical masks today and EUV masks in the near future, it is critical to correct mask patterning errors with a magnitude of up to 20nm over a range of 2000nm at mask scale caused by short range mask process proximity effects. A new mask process correction technology, MPC+, has been developed to achieve the target requirements for the next generation node. In this paper, the accuracy and throughput performance of MPC+ technology is evaluated using the most advanced mask writing tool, the EBM-70001), and high quality mask metrology . The accuracy of MPC+ is achieved by using a new comprehensive mask model. The results of through-pitch and through-linewidth linearity curves and error statistics for multiple pattern layouts (including both 1D and 2D patterns) are demonstrated and show post-correction accuracy of 2.34nm 3σ for through-pitch/through-linewidth linearity. Implementing faster mask model simulation and more efficient correction recipes; full mask area (100cm2) processing run time is less than 7 hours for 32nm half-pitch technology node. From these results, it can be concluded that MPC+ with its higher precision and speed is a practical technology for the 32nm node and future technology generations, including EUV, when used with advance mask writing processes like the EBM-7000.

Proximity Effect Correction for Mask Writing Taking Resist Development Processes into Account

In this paper, a proximity effect correction method for mask fabrication with taking into account resist development processes is proposed. The idea of our method is that the figure size of a developed resist is determined using a suitable function of exposure dose and the normalized deposited energy by backscattering electrons, under the assumption of high acceleration voltage electron beam mask writing. This suitable function should be determined empirically to include the effects of resist development process, and is called development process function in this paper. Methods of deriving the development process function, proximity effect correction equation, and optimum correction dose from the equation are proposed. To check the accuracy of our method, a sample model of development process function is introduced under the condition that the conventional threshold model has an intrinsic error of 8 nm. The method proposed in this paper is found to be able to suppress the correction error of this sample model to less than 1 and 0.2 nm by two and three iterations, respectively. The method proposed in this paper is expected to provide high accuracy proximity effect correction in future mask fabrication.