Tzv. Ivanov

Micromachined atomic force microscopy sensor with integrated piezoresistive sensor and thermal bimorph actuator for high-speed tapping-mode atomic force microscopy phase-imaging in higher eigenmodes

This article describes microprobes for noncontact scanning force microscopy that make use of a direct-oscillating thermally driven bimorph actuator with integrated piezoresistive readout sensor. The sensitivity has been increased using direct current for biasing and alternating current for exciting the thermally driven cantilever in a higher flexural mode. The cantilever operates in the phase-shift atomic force microscopy (AFM) detection technique. The main advantage of phase imaging is the higher z resolution at high scan rates and much lower forces than in height imaging with contact AFM. Critical dimensions measurements illustrating the imaging capability and resolution of our new scanning proximal probe are demonstrated.

Scanning proximal probes for parallel imaging and lithography

Scanning proximity probes are uniquely powerful tools for analysis, manipulation, and bottom-up synthesis. A massively parallel cantilever-probe platform is demonstrated. 128 self-sensing and self-actuated proximal probes are discussed. Readout based on piezoresistive sensors and bending control based on bimorph dc/ac actuations are described in detail.

Quantum size aspects of the piezoresistive effect in ultra thin piezoresistors

Proximal probe sensors with an ability to detect extremely small forces (10(-15)-10(-18)N) play significant role in scanning probe microscopy applications. The detection of extremely low forces, require producing micromachined cantilevers with as small as possible spring constants, which is considered by the optimization of the sensor design. In the last year many papers describing the fabrication process of producing ultrathin cantilevers (below 100nm) with integrated piezoresistors for deflection read-out have been published. In the case of such cantilevers the required thickness of piezoresistors is in the range of 50nm. From a quantum mechanical point of view, an electrical carrier transport confinement in direction perpendicular to the cantilever surface can be expected and in this manner we have to consider the quantum size effect. The goal of the project described in this paper is to calculate and determine the piezoresistive coefficients in p type Si thin (under 50nm) piezoresistors taking into account the quantum size effect and to compare them with the corresponding coefficients for bulk material. The calculation of the band structure will use the mathematical apparatus of an exact analytical diagonalization six-band k.p model, modified with the envelope function approximation. The behaviour of the thin piezoresistors employed as integrated deflection read-out will be also discussed. Moreover, critical issues in the realization of piezoresistors formed by MOS transistor channel will be presented.

Thermally driven micromechanical beam with piezoresistive deflection readout

This article reports on the fabrication and characterization of micromachined thermally driven micromechanical beam with piezoresistive readout for Micro- and nanorobotic systems and advanced high speed scanning probe microscopy. The essential contribution of this paper is investigation of the actuating efficiency of an integrated cantilever microheater. To optimize the properties of the developed system we use finite element (analysis) modelling. Obtained theoretical and experimental results were proven using fiber interferometry in combination with electrical characterization of the piezoresistive deflection detector. We found out that the most efficient actuation position of the microheater on the beam is at the cantilever end. We have fabricated samples where the beam deflection was in range of 2 µm (for beam of length 550 µm). The smallest electrothermal driving power causing the deflection of 1 nm was estimated to be in the range of 8 nW.

Chemical recognition based on micromachined silicon cantilever array

We report on the performance of a measurement system for the recognition of individual analytes and their binary mixtures which is based on a multiarray of four micromachined silicon cantivelers actuated at their resonance frequency. The cantilevers have been functionalized by organic polymers [polydimethylsiloxane (PDMS) and polyvinylpyridine (PVP)] and amorphous nitrogen-rich carbon nitride films. We found that the sensitivity and selectivity of the cantilevers coated with CNx films change according to the layer thickness. Our results show that the selected combination of sensitive layers ensures a wide range of specific, reversible and reproducible sensor responses upon exposure to methanol, 2-propanol, water and their binary mixtures. Further, it was found that the differences in recovery times of PDMS and CNx films after exposure to the two alcohols and their mixtures could be used especially for low analyte concentrations as a second characteristic in addition to the resonance frequency shift for th...

Profile simulation of gas chopping based etching processes

A simulation program based on a phenomenological surface etching reaction model and on a reactant transport model including shadowing and diffuse particle reflection at the sidewalls was developed to investigate the dependence of the etching rate and profile quality of gas chopping deep reactive ion etching processes on process parameters and sample temperature. The simulations are in good agreement with the experimental results. The dependence of the heating characteristics on the geometry (area, thickness) of teeny microelectromechanical systems devices or membrane-like silicon samples during microstructuring by means of plasma etching was investigated using finite element simulations. It was found that membrane-like samples are considerably heated unless the membrane area is sufficiently small (<≈5 mm φ) and/or is sufficiently thick (≈500 μm).

AFM cantilever with ultra-thin transistor-channel piezoresistor: quantum confinement

This paper presents a comparison between the piezoresistivity effects on bulk silicon and its modification in the 2D case of the induced channel in the metal oxide semiconductor field effect transistor (MOSFET). The Schrodinger equation used for the calculations in this paper is based on the 6 × 6 kp Hamiltonian, which includes the effect of spin orbit interactions, band mixing, and strain. The effect of confinement is treated from the Schrodinger equation, coupled with the Poisson equation. In such a way, the valence band structure for the p-induced channel in MOSFET is resolved from a numerical self-consistent solution of the Schrodinger-Poisson system of equations. The calculations are made to show what happens when a MOSFET-like piezoresistor is substituted for one of the ordinary resistors of a Wheatstone bridge.

Ion Implantation with Scanning Probe Alignment

We describe a scanning probe instrument which integrates ion beams with the imaging and alignment function of a piezoresistive scanning probe in high vacuum. The beam passes through several apertures and is finally collimated by a hole in the cantilever of the scanning probe. The ion beam spot size is limited by the size of the last aperture. Highly charged ions are used to show hits of single ions in resist, and we discuss the issues for implantation of single ions.

Micromachined piezoresistive proximal probe with integrated bimorph actuator for aligned single ion implantation

The authors report a microfabrication procedure of self-actuated piezoresistive scanning probes (SAPSPs). They are designed for a SAPSP instrument that is integrated with an ion beam for aligned single ion implantation in ultrahigh vacuum. The novelty of the design is an integrated hollow pyramid, instead of a previously mechanically hand mounted pyramid [J. Vac. Sci. Technol. B 23, 2798 (2005)]. The pyramid has dual purpose. First it collimates the ion beam and suppresses secondary particles from the back side of the cantilever, so that secondary particles from the target material can be used for single ion detection. Second the pyramid also provides an atomic force microscope tip for the scanning probe. A crucial step in the fabrication is the back side opening via etching for the hollow pyramid. The fabrication procedure will be discussed in detail.

Single ion implantation with scanning probe alignment

We present results from our development of a single ion implantation technique integrated with a scanning force microscope. Accurate alignment at the 5nm level is a crucial requirement for reliable single ion placement. We address this through integration of the ion beam with a scanning probe tip containing an aperture. Single ion registration is based on detection of secondary electron bursts from single, high charge state ions. We describe formation of scanning probe tips with holes and sensing poles by focused ion and electron beam processing (drilling and thin film deposition). Ion transport studies through apertures show stable transmission for >10h with 1nA scale beam intensities on precollimators.