Robert Storch

The multipole resonance probe: characterization of a prototype

The multipole resonance probe (MRP) was recently proposed as an economical and industry compatible plasma diagnostic device (Lapke et al 2008 Appl. Phys. Lett. 93 051502). This communication reports the experimental characterization of a first MRP prototype in an inductively coupled argon/nitrogen plasma at 10?Pa. The behavior of the device follows the predictions of both an analytical model and a numerical simulation. The obtained electron densities are in excellent agreement with the results of Langmuir probe measurements.

The Multipole Resonance Probe: Progression and Evaluation of a Process Compatible Plasma Sensor

A robust and sensitive plasma sensor, the multipole resonance probe (MRP), and its process compatibility are presented and discussed in this paper. Based on its innovative concept and simple model describing the system “probe-plasma”, three steps of development are introduced. 3D electromagnetic field simulations are applied as an indispensable tool for an economical and efficient investigation and optimization of different sensor layouts. Independent of the chosen sensor design, a developed pulse-based measurement device yields an economical signal generation and evaluation. Electron density profiles, determined with the MRP and the pulse-based system utilized in a capacitive coupled plasma, confirm and demonstrate the simulation results and the measurement concept, respectively.

The multipole resonance probe: Realization of an optimized radio-frequency plasma probe based on active plasma resonance spectroscopy

A diagnostic concept is presented which enables the simultaneous determination of plasma density, electron temperature, and collision rate in low-pressure gas discharges. The proposed method utilizes a radio-frequency driven probe of particular spherical design which is immersed in the plasma to excite a family of spatially bounded surface resonances. An analysis of the measured absorption spectrum S(ω) of the probe provides information on the distribution of the plasma in its vicinity, from which the values of the plasma parameters can be inferred. In its simplest realization, the probe consists of two dielectrically shielded, conducting hemispheres, which are symmetrically driven by a radio-frequency source, and the excited resonances can be classified as multipole fields, which allows an analytical evaluation of the measured signal. A comparison of the analytical results, 3D-field simulations, and first measurements of a prototype show the functionality of the presented probe concept.

A novel radio-frequency plasma probe for monitoring systems in dielectric deposition processes

This paper presents a novel industry compatible plasma probe for monitoring systems in dielectric deposition processes. The probe is based on the so called active plasma resonance spectroscopy and allows an extensive evaluation of different important plasma parameters, needed for the supervision and control of the plasma deposition process. Due to its assembly, the probe is insensitive against additional dielectric coating. Hence, the measurement performance is not affected. 3D-electromagnetic field simulations of the probe in a pseudo plasma deposition process, as well as the measurement with a prototype in a real deposition process show a good agreement with the expected behaviour and confirm the applicability of the probe as a monitoring tool for dielectric deposition processes.

The multipole resonance probe: Evolution of a plasma sensor

A robust and sensitive plasma probe, the multipole resonance probe (MRP), and its importance for industrial purposes is presented and discussed in this paper. Based on its innovative concept and its simple model of the system ”probe-plasma”, a novel wall-mounted sensor is introduced. This sensor represents an optimized design of one sector of the MRPs assembly and is investigated within 3D-electromagnetic field simulations and compared to measurements of the MRP in an argon plasma. The resulting wall-mounted sensor can be designed for a desired application, which operates within a limited frequency range. The presented sensor covers a density range of approximately ne = 1016 m-3... 1017 m-3, which is sufficient for the considered process.

A multisection ultra wideband directional coupler in multilayer broadside coupled stripline technology

In this paper, we present a multisection directional coupler providing a tight coupling of 10 dB with an equal ripple of 0.8 dB across the frequency range of 360 MHz to 5.8 GHz, which corresponds to a relative bandwidth of 177 %. To maximize coupling and reduce dispersion effects, the coupler uses broadside coupled striplines in a multilayer setup. The four ports of the coupler are connected via standard SMA-connectors through a stripline to microstrip transition that does not make use of vias. The design process is verified by EM simulations and measurements performed on a prototype.

Synthesis Concepts of Signals With High Spectral Purity for the Use in Impulse Radar Systems

This paper focuses on the synthesis of ultralow-noise signals for the use in a timebase of impulse radar systems. These systems are used in manifold applications and their accuracy is strongly dependent on the spectral purity of the timebase. Current systems use either phase-locked loops (PLLs) or direct digital synthesizers (DDSs). These PLLs comprise an excessive amount of components and recent DDSs still have a low spurious-free dynamic range (SFDR). Therefore, this paper presents two new approaches for the direct synthesis. They are based on frequency dividers with both short division factor sequences and noise-shaping techniques. Ideas for spur avoidance and noise reduction are described to improve the noise behavior in terms of SFDR and phase noise. The presented approaches have been realized in hardware and measurement results are depicted. For the system using frequency dividers with short division factor sequences, the best results are a SFDR better than 117 dB at a signal frequency of 10.7 MHz. The phase noise level is below -140 dBc/Hz at offset frequencies greater than 1 kHz. Regarding the frequency dividers with noise-shaping techniques, no discrete spurious are visible. The phase noise level at offset frequencies greater than 7 kHz is below -150 dBc/Hz. These results are comparable with state-of-the-art PLL concepts and thus confirm the approaches.

Ultra low noise signal synthesis for the use in a FMCW MIMO radar system

A great number of spatially distributed transceiver chips within multiple-input multiple-output radar systems make the reference signal synthesis as well as its distribution to an emerging topic. Therefore, we introduce a synthesizer based on the concept of fractional-N division which is able to provide a linear frequency ramp around 200 MHz. Furthermore, an ultra wideband phase-locked loop (PLL) is presented using this synthesizer and featuring a bandwidth of 22 GHz centred around 85 GHz. For stabilizing the PLL over the complete bandwidth a passive auxiliary circuit has been developed. The system achieves a phase noise below -78 dBc/Hz at 10kHz offset over its complete bandwidth.

A DC to 5 GHz TDR pulse generating unit with a highly stable timebase for use in a plasma diagnostic measurement system

A pulse based system for generating and processing an ultra-wideband radio frequency signal for the use within a plasma diagnostic measurement system called multipole resonance probe is presented. For fulfilling the fairly high demands on the required frequency range a new integrated truly differential ultra-wideband pulse generator was developed. This generator achieves a pulse width of less than 70 ps resulting in a bandwidth of about 5 GHz. As an appropriate subsampling of this ultra-wideband pulse is only possible with a timebase offering an extremely low phase noise level a new concept was developed. This concept shows a phase noise level of about -150 dBc/Hz @ 50 kHz offset at a signal frequency of 21.4 MHz. These results prove the feasibility of the developed components for an application within the plasma diagnostic concept.

Spectral properties of time domain reflectometry systems

Time domain reflectometry (TDR) systems are widely used to perform accurate distance measurements. The crucial component that determines accuracy and repeatability within these systems is the timebase. For an optimal design it is mandatory to have a precise knowledge about the impact of errors within the timebase on the measurement result. Besides the influence of stochastic errors this paper mainly deals with the analysis of deterministic errors. A mathematical model will be derived which can be used to optimize timebases only by means of the spectral properties of the signals. This model is compared to measurement results verifying the usefulness of the approach.