**7. Acknowledgements**

I would like to thank Profs. H. Sone, Y. Yin, K. Itoh, Z. Mohamad and T. Tamura, and students of Ms. H. Zhang, Mr. H. Sano, Mr. M. Shirai in Hosaka labo of Gunma University for the experiments, simulation and fruitful discussion, and Mr. K. Noguchi in Dept. of Electronic Eng., Gunma University for technical supports in EB writing and resist process. This research was performed in Kiryu Ohta Toshi Area project supported by the Ministry of Monbukagaku-sho of Japan.

#### **8. References**

24 Recent Advances in Nanofabrication Techniques and Applications

Fig. 5.5. Process flow of 2P (photo polymer) method for nano-imprinting.

**6. Conclusion** 

Fig. 5.6. SEM images of very fine pitch pit arrays in photo-polymer using nano-imprinting with the Si mold made by RI etched Si dot arrays pattern with a pitch of 25 nm x 25 nm drawn by 30 keV electrons with exposure dosages, (a) 28 mC/cm2, (b) 36 mC/cm2 .

I have described an electron beam (EB) lithography using a raster drawing for fabrication of nanometer sized dot or pit arrays, theoretically and experimentally. I considered the possibility to form the nanometer-sized pitch fine dot arrays by the energy deposition distribution (EDD) calculated by the home-made Monte Carlo simulation. The experimental research is done by dependences of 2 resist materials (ZEP520 and calixarene) and thickness on the drawn dot size and pitch in EB drawing. I have used a conventional EB drawing system based on high resolution-scanning electron microscope (HR-SEM). As results using both positive and negative resists with thin thickness. I can demonstrate the possibility to

1. The simulation shows that the EDD profile seems to be cone shape, which is very suitable for formation of nanometer-sized dots using negative resist, while it is not

form nanometer-sized dot and fine pitched dot arrays as follows.

suitable in a case of using positive resist.


**2** 

*Austria* 

**Focused Ion Beam Lithography** 

*Vienna University of Technology – Institute for Solid State Electronics* 

Optical lithography is the unrivalled mainstream patterning method that allows for costefficient, high-volume fabrication of micro- and nanoelectronic devices. Current optical photolithography allows for structures with a reproducible resolution below 32 nm. Nevertheless, alternative lithography methods coexist and excel in all cases where the requirement for a photomask is a disadvantage. Especially for low-volume fabrication of microdevices, the need for a photomask is inefficient and restricts a fast structuring, such as required for prototype device development and for the modification and repair of devices. The necessity of high-resolution masks with a price well above €10k is too cost intensive for the fabrication of single test devices. For this reason 'direct-write' approaches have emerged that are popular for several niche applications, such as mask repair and chip repair. Optical direct-write lithography and electron beam lithography are among the most prominent techniques of direct-write lithography. Less known, but highly versatile and powerful, is the

Optical direct-write lithography uses laser beam writers with a programmable spatial light modulator (SLM). With 500 mm²/minute write speed and advanced 3D lithography capabilities, optical direct-write lithography is also suitable for commercial microchip fabrication. However, with a resolution of 0.6-µm minimum feature size of the photoresist pattern, optical direct-write lithography cannot be considered a nanopatterning method. Electron beam lithography uses a focused electron beam to expose an electron beam resist. Gaussian beam tools operate with electron beams with a diameter below 1 nm so that true nanofabrication of structures is feasible. A resolution of 10 nm minimum feature size of the e-beam resist pattern has been successfully demonstrated with this method. However, special resists are required for e-beam lithography, that are compatible with the high energy of forward scattered, back-scattered and secondary electrons. A common resist for sub-50nm resolution is polymethylmetacrylate (PMMA) requiring an exposure dose above 0.2 µC/µm². For highest resolution (below 20 nm) inorganic resists such as hydrogen silsesquioxane (HSQ) or aluminium fluoride (AlF3) are used, which unfortunately require a high electron exposure dose. Hence, high-resolution electron beam lithography (EBL) is linked to long exposure times which, in combination with a single scanning beam, results in slow processing times. Therefore, this high-resolution method is only used for writing photomasks for optical projection lithography and for a limited number of high-end applications. A resolution to this dilemma may be the use of multi-beam electron tools, as are currently under development. Also electron projection lithography has been under

**1. Introduction** 

ion beam lithography (IBL) method.

Heinz D. Wanzenboeck and Simon Waid

