To study and control the behaviour of the spins of electrons that are moving through a metal or semiconductor is an outstanding challenge in the field of 'spintronics', where possibilities for new electronic applications based on the spin degree of freedom are currently being explored. Recently, electrical control of spin coherence and coherent spin precession during transport was studied by optical techniques in semiconductors. Here we report controlled spin precession of electrically injected and detected electrons in a diffusive metallic conductor, using tunnel barriers in combination with metallic ferromagnetic electrodes as spin injector and detector. The output voltage of our device is sensitive to the spin degree of freedom only, and its sign can be switched from positive to negative, depending on the relative magnetization of the ferromagnetic electrodes. We show that the spin direction can be controlled by inducing a coherent spin precession caused by an applied perpendicular magnetic field. By inducing an average precession angle of 180 degrees, we are able to reverse the sign of the output voltage.

Electrical detection of spin precession in a metallic mesoscopic spin valve

Provided is a method for forming fine pattern free from shear of pattern caused by charging and high in dry etch resistance by using a high molecular organic film containing an organometallic complex or a metallic salt in single-layer or multi-layer resist process and treating the surface of this film with a reducing agent to form a metallic layer on the surface.

Fine pattern forming method

Publisher Summary This chapter provides an overview of the new techniques for fabrication at a size scale below 100 nm. A number of nanometer-scale devices and scientific studies have become possible with these techniques, and research in this field has seen a number of recent successes. The chapter focuses on the limits and applications of the nanometer-scale fabrication techniques, not their practicality for current device production. The chapter presents the three-dimensional techniques that seem to permit fabrication of structures smaller than 10 nm. However, there are a variety of effects that limit their resolution. The most obvious is penumbra because of limited collimation of the ion beam or evaporant flux. This effect can be eliminated at the cost of reduced flux by simply using apertures or moving the source further from the sample. The chapter also describes the utilization of the third dimension and new three-dimensional lithographic approaches. Such approaches are of clear advantage for achieving high-aspect-ratio patterns, high resolution, and good line width control over a large field of view. When three-dimensional approaches are combined with other self-aligning or self-limiting processes, very powerful device micro-fabrication approaches can be developed.

Chapter 4 - Nanometer-Scale Fabrication Techniques

Metal features with 10‐nm linewidths were produced on thick GaAs substrates using electron beam lithography. A single layer of polymethylmethacrylate (PMMA) was exposed by an approximately 2‐nm‐diam electron beam with energies ranging from 20 to 120 keV. Gold‐palladium lines less than 20 nm wide, and 15 nm thick, with center‐to‐center spacings of 70 nm, were produced over 15‐μm square fields at all electron beam energies by lift off. The exposure latitude increased significantly for higher electron energies, with 10‐nm‐wide metal lines formed using a 120‐keV writing beam.

10‐nm linewidth electron beam lithography on GaAs

Surface‐Initiated Polymerization on Nanopatterns Fabricated by Electron‐Beam Lithography

A trilevel electron beam resist has been used to make 25‐nm metal features on thick silicon substrates. Using this metal as a mask for reactive ion etching, silicon structures 0.33 μm deep have been fabricated. The resist consists of a thin upper layer of polymethylmethacrylate (PMMA), a middle layer of Ge, and a lower layer of co‐polymer of methylmethacrylate and methacrylic acid, P(MMA/MAA). High‐resolution patterns are written in the upper resist layer and are transferred to the lower layers by reactive‐ion etching. Completed resist stencils have 300‐nm high walls with near‐vertical profiles and are suitable for liftoff processing.

50−nm silicon structures fabricated with trilevel electron beam resist and reactive‐ion etching

Resist features as small as 200 A and gold lines as narrow as 400 A separated by 800‐A center to center have been fabricated on thick silicon. substrates. A two‐layer electron‐sensitive resist structure is employed consisting of an upper layer of polymethyl‐methacrylate and a lower layer of a copolymer of methacrylic acid and methyl methacrylate. Use of the more electron‐sensitive lower layer results in an undercut which provides clean lift‐off of the evaporated gold. Degradation in the pattern resolution by electrons backscattered from the substrate is minimized by the presence of the lower resist layer. This method provides the finest resolution lift‐off patterns reported.

400‐Å linewidth e‐beam lithography on thick silicon substrates

High resolution electron beam lithography has been used to fabricate ion implanted buried channel MOSFET's with gate lengths ranging from 0.4 µm to 700 A. Similar devices were also fabricated on the same chip using optical lithography with gate lengths of 2.5 µm. These devices include some with the smallest lithographically defined gates ever made in silicon; similar devices should help define the limits to miniaturization in semiconducting devices.

P. Grabbe

Papers

50−nm silicon structures fabricated with trilevel electron beam resist and reactive‐ion etching

400‐Å linewidth e‐beam lithography on thick silicon substrates

Buried channel MOSFET's with gate lengths from 2.5 µm to 700 Å

P. Grabbe

Papers

50−nm silicon structures fabricated with trilevel electron beam resist and reactive‐ion etching

400‐Å linewidth e‐beam lithography on thick silicon substrates

Buried channel MOSFET's with gate lengths from 2.5 &#181;m to 700 &#197;

Buried channel MOSFET's with gate lengths from 2.5 µm to 700 Å