Nothing is Left Here

With ever smaller devices, optical lithography has reached its limit, so other lithography techniques are required to read ... to learn more!

Latest developments in lithograph Photos!

Moore's Law has governed the growth of the semiconductor sector. The main factor of production of complex devices at low cost is lithography. Lithograph optic was reaching the physical limit and thus leads to the development of techniques for alternate. Immersion lithography has recently attracted the interest in industrial research. In other alternatives, many people regard as extreme ultraviolet lithography and nano-imprint lithography as potential successors of optical lithography. Finally, we also explore the potential of x-ray lithography and electron beam lithography as potential candidates.

Immersion Lithography

Around the uniqueness immersion lithograph is seen replacing air with ultrapure water as the medium between the lens and the wafer. This pushes the physical limits of NA for exposure beyond systems NA = 1 for air, given the following report: NA = n = sin alpha d/2f. Ultra pure water is very suitable because it has a refractive index of 1.47, absorption of

Ultravioletti extreme lithography

EUVL uses light sources with wavelength (13.4nm) 10 times less than current wavelength (139nm). This will enable the manufacture of circuit lines smaller than 0.1 microns wide, extensible below 30nm. EUVL masks are reflective masks, shaped with an absorber of EUV radiation placed on top of the ML (multilayer film alternating thin layers of Mo and SI) reflector deposited on a robust and solid substrate, such as a silicon wafer. The main requirement is to make a mask with essentially no defects. The strong absorption of EUV radiation of all the materials poses the main problem in developing a satisfactory photoresist for EUV lithography. . The thin layer imaging is already a mature technology, and then resist is no longer a critical issue. Printed lines as small as 50Nm in photoresist has already been achieved.

Virtual National Laboratory (VNL) formed by three laboratories - Lawrence Livermore, Lawrence Berkeley and Sandia / California, has developed and built a prototype of extreme ultraviolet lithography-ray (EUVL) system called engineering test bed (ETS). ETS has produced models this test with a line spacing ratio of 1:1 with high fidelity down to line widths of 70 nm using its September-2-optics. By adjusting the lighting of the model and the dose of exposure, the team has printed less densely spaced lines with a width of up to 39 nm. E 'then be able to meet production requirements set for chips with 1 billion transistors and up over the years from 2007 to 2010.

X-Ray Lithography

The basis of establishing a typical XLR system is using a synchrotron as a source of x-ray Synchrotron-based XLR provides a broad exposure to doses window, which is very important in ULSI manufacture. Insensibilità to dust is another advantage, that will affect the amount of model defects. The source is an electromagnetic waves, which is generated when high-energy electrons are accelerated. To minimize the absorption of x-ray, the mask substrate consists of a thin membrane consists of materials with a low atomic number. The question regarding this method is here that is necessary for an overlap of precision that meet the requirements of sub-0.1-um ULSI manufacturing, while another problem is the speed of transmission. Of choose correctly median wavelength, proximity x-ray lithography (PXRL) can be extended to 50Nm using relatively large mask / wafer gaps. This objective can be achieved by increasing the energy storage ring, decreasing the angle incident on beamline mirror, and employing a diamond mask substrate. Increasing the median of energy at 2.6 to 2.7keV allows the printing of smaller features up to 35nm using a difficult spectrum, choosing the appropriate materials for the mask and resist match the transmission and absorption in this high energies.

Electron beam lithography

Electron beam lithography apply direct writing method electron beam scan in various materials surface covered with film resist to create models of wide desired on substrates. Given the high energy electron beam (tens of hundred eV), it totally eliminates the diffraction effect, however, that it may give damages to the substrate material. The resolution is now limited aberration electronics, optics and scattering effect is more serious. By scattering effect of correction, it may reach a resolution of about 10-20nm. How pattern generation is carried out through the surface scanning pixel per pixel controlled by Computer Aided Design (CAD), this leads to very slow speed, and then very low productivity. Even though this E-beam direct writing does not require a mask that usually costs much to specific material, sensitive equipment and cost maintains frequent are usually very expensive up to millions of dollars, so mass production is economically unfavorable. These speed and cost considerations limit its application in mass commercial production for 50 nm-sized function, even if it has a high level of resolution. But this technique is used for the production of high quality mask with good resolution and also widely used in research.

Nano-imprint Lithography (NIL)

NIL creates a model to resist relief to resist deforming the shape with embossing, instead of changing the chemical structure resist radiation or the creation of the model of self-assembly. The model is then transferred into the material to be recorded (a wafer If, for example) using resist as a mask. The key advantage of this technique litho is the ability to model sub-25 nm structures on a wide area with a high flow and low cost. Unlike conventional methods, lithography, lithography same footprint does not use any energy beams. Therefore, nano-imprint lithography of the resolution is not limited by the effects of the waves diffraction, dispersion and interference in a resist, and backscattering from a substrate.

There are two jumps of this technology recently. A new UV-based nanoimprint lithography (UV-NIL) was developed and showed to AMO as an alternative to hot embossing technique. The low pressure (researchers at Princeton University, USA, have shown that photocurable nanoimprint lithography (P-NIL) produce lines of polymer resist only 7 nm with a wide step (or the pattern repeat) of only 14 nm. The technique also produced reliable results over the entire surface of a sample of 4 inch wafers.

Comparison

In choosing the most promising technology that could allow 50Nm in size and functionality in a row, we considered the following factors in our decision. They are the cost of technology, the throughput of the method, the amount of bonds that faces at the moment and the possibility of technology for the production of 50Nm feature size.