Robert Andok

Advanced patterning techniques for nanodevice fabrication

The key elements in the fabrication of future devices are lithography and pattern transfer. The continuous advances in miniaturization and increasing integration densities are a direct result of improved lithographic resolution and overlay accuracy. Electron beam direct write and e-beam projection lithography are potential candidates for the mass production of microelectronic devices with critical dimensions below 100 nm. To realize these nanometer patterns by this technology, the performance of exposure tools and resist materials should be increased. In this paper, the method of direct write e-beam lithography is demonstrated and critical issues are discussed.

The AZ 5214E Resist in EBDW Lithography and its Use as a RIE Etch–Mask in Etching Thin Ag Layers in N2 Plasma

Abstract In this article we describe the electron-beam direct-write (EBDW) lithography process for the AZ 5214E photoresist which is, besides its sensitivity to UV radiation, sensitive also to electrons. An adapted process flow is provided. At the same time we examine the resistance of this resist to RIE and its suitability as an etch-mask for etching thin Ag layers in N2 plasma. A comparison with several chosen resists (PMMA, ma-2405, ma-N 1402, SU-8 2000) is provided.

CAPACITANCE ANALYSIS OF THE STRUCTURES WITH THE a-Si:H(i)/c-Si(p) HETEROJUNCTION FOR SOLAR-CELL APPLICATIONS

Abstract In this paper we present the capacitance study of the intrinsic amorphous silicon/crystalline silicon heterostructure with the aim to gain insight on the heterointerface properties of a passivated silicon heterojunction solar cell. It is shown that due to the high density of defect states in the amorphous layer the structure has to be analyzed as a heterojunction. Using the analysis, the following values have been determined: conduction-band offset of 0.13 eV, electron affinity of 3.92 eV, and density of defect states in the intrinsic amorphous silicon being that of 4.14 X 1021m—3.

RIE of the polyimide micromechanical structures

Polyimides are commercially available materials which are widely used in various aspects of microelectronics. In this work, we show the use of a polyimide as a material suitable for the formation of micromechanical structures and its modification by reactive ion etching.

Limitations of variable shaped electron beam lithography for advanced research and semiconductor applications

This paper reports on the study of limitations of variable shaped electron beam lithography (EBL) as flexible high-resolution pattern generators for the fabrication of high quality photomasks required for many applications in sensors and microsystems development, including packaging applications. For this purpose, the case of 50×50 nm2 electron beam shape at 40 keV electron energy and a high-resolution e-beam resist Hydrogen Silsesquioxane (HSQ) were utilized. Various process parameters, which determine the accuracy of the resist profiles and the size of structures, such as solubility rates, dependences of the linewidth on the exposure dose, lithographic resolution, etching capabilities of HSQ and their influence on the limitations of variable shaped EBL, are studied.

Study of negative electron beam nanoresist HSQ on GaAs substrate

The aim of this paper is to characterize Hydrogen Silsesquioxane (HSQ) inorganic negative electron resist on GaAs substrate at 40 keV electron energy. The influence of process parameters on resist profiles was investigated with the aim of obtaining vertical sidewalls. The values of the proximity effect function parameters (β_f, β_b and η_E) were calculated using Monte Carlo approach. Observation of HSQ resist profiles were done for a set of linewidth dimensions.

Simple patterning method of sub-micro- and nanometer structures for gas sensor

In this study, a simple patterning method of submicrometer structures is proposed for gas sensor development. Comb-like electrodes patterned in thin Pt layer were proposed to measure gas sensor electrical conductivity. Negative resist SU-8 was used as a masking layer for ion etching of electrodes in 35 nm Pt layer on sapphire substrate. This method was applied for the patterning of the comb-like structures with submicrometre dimensions for gas sensor conductivity measurements.

Estimation of exposure parameters of chosen e-beam resists using variable shaped e-beam pattern generator

In this article we present results from lithography experiments on PMMA (positive tone), and HSQ Fox-12 and SU-8 (negative tone) resists carried out on the ZBA variable shaped e-beam pattern generators. In order to obtain the necessary information needed for the optimization of the exposure control Point Spread Function PSF, several lithography tests are mentioned. The carried out measurements and analysis of the results help us in obtaining important information about the resists and exposure processes and enable us to practically verify the suggested methods of parameters extraction for a reliable exposure model.

Material optimization of the alignment marks for the EBDW lithography

We present results of material optimization for the alignment marks used in the Electron-Beam Direct-Write (EBDW) lithography. Such marks have been proposed both for negative (grooves) as well as for positive (elevated) topographies. The primary mask for the alignment mark patterns is done by photolithography and e-beam lithography. The negative topography of the marks was transferred by Deep Reactive Ion Etching (DRIE), while the positive topographies were realized by evaporation of various metals followed by lift-off process. We measured signals at characteristic beam-steps when the e-beam scans across the mark. This was done on two scanning positions. Out of these measurements we obtained the detection signal characteristics for different fiducial alignment marks with positive and negative topographies, respectively.

New progressive method suitable for the exposure optimization of large and complex defect-free chips direct written by ZBA 21 e-beam tool

The use of a new progressive method suitable for the exposure optimization is investigated for large and complex defect-free chips direct written by ZBA 21 electron beam pattern generator together with all corresponding microprocesses. Well controlled and resolved details (spaces) between individual quasi-square structures of the final large area neural holography chip were achieved in the range of about 50 nm.