Recording head field measurement with a magnetoresistive transducer

This paper describes the measurement of recording head fields with the help of a magnetoresistive transducer. Attention is payed to the computer program to simulate the transducer behaviour in inhomogeneous fields (with emphasis on the accuracy) and to the experimental procedure to overcome the difficulties of positioning the transducer in the head gap region accurately. Results of measurements on two audio heads with gaplength 3.3um and 7um are analysed and show a reasonable agreement with the theoretical predictions

Hall-effect device with both voltage leads on one side of the conductor

A Hall effect device has been designed and tested with both voltage contacts on one side of the Hall element. The proposed layout lends itself to placing the device on the edge of a substratum (possible application as position detector and recording read head). The response of the device to inhomogeneous magnetic fields has been calculated and the results are in agreement with experiment

On the calculation of the response of (planar) hall-effect devices to inhomogeneous magnetic fields

The calculation of Hall potentials in a rectangular Hall plate is treated for the case in which the device is subject to a magnetic field B that is inhomogeneous in the y-direction perpendicular to the direction of initial current flow. The potentials are presented in the form φH(→r′) = const. ∫widthB(y)G(y,→r′)dy for the normal Hall effect (→r′ is the position vector).\ud \ud Analytical expressions are given for the weight function G (which depends on the form of the device), together with graphs for a number of typical examples. An analogous expression is derived for the planar Hall effect in ferromagnetic thin films

Measurement system for two-dimensional magnetic field distributions, applied to the investigation of recording head fields

The system described is built around a very accurate positioner into which a sensitive transducer and the object of analysis is mounted. The properties of the applied magnetoresistive transducer are described. This transducer, a very narrow permalloy strip placed at the edge of a glass substratum, can be used to measure both components of the field distribution. The analysis of the measured results can be accomplished with the help of a computer simulation of the transducer response curves. The performance of the system is demonstrated by measurements on a number of ferrite heads and conclusions about the so called 'dead layer'-structures on these heads are given

Investigation of the structure of recording head fields

Head fields of two recording heads (gap lengths 2.1 and 2.8 micrometer) have been measured with the help of a series of magnetoresistive transducers. The widths of these transducers are 1.9, 4.1 and 7.0 micrometer and they have been positioned in the gap field region very accurately using optical methods. The transducer outputs have been compared with computer simulated results. A systematic deviation between theoretical and experimental results may lead to the assumption that the surface of the recording head is magnetically inactive over a few tenths of a micrometer

Realization of mechanical decoupling zones for package-stress reduction

The realization of mechanical decoupling zones around a membrane to reduce package stresses is presented. Wet-isotropic etching with a nitric/fluoridic solution (HNO3/HF/H2O) as well as reactive-ion etching (RIE) with a sulphurhexafluoride/oxygen (SF6/O2) plasma are investigated to realize deep circular grooves. The shape of the cross section of the groove, which determines the shape of the decoupling zone, can be controlled using the RIE method by changing the etch conditions. It is shown that a large undercut at low pressures as well as a small undercut at high pressures is possible with a SF6/O2 plasma, leading to round or steep sidewalls of the grooves, respectively. Finally a completed bare structure containing a membrane and a surrounding decoupling zone is presented

Resonating silicon beam force sensor

A resonating silicon-beam force sensor is being deveoped using micro-machining of silicon and IC-compatible processes. Results are reported here of measurements on the force-to-frequency transfer of bare silicon prototypes. The measurements with forces on the sensor beam up to 0.4 N shows a frequency shift of 3.1 to 5.2 times the unloaded resonance frequency f0(f0 congruent with 3 to 5 kHz), depending on the exact dimensions. Considering these figures, we can predict a frequency shift of 18.3 to 27.6 kHz at the maximum load of 1.0 N for the measured samples. Due to the sample lay-out, a force transfer is present from the externally applied force to the actual pulling force on the sensor beam. Using a simple model to calculate this reduction, we obtain good agreement between the measurements and predictions

Low temperature sacrificial wafer bonding for planarization after very deep etching

A new technique, at temperatures of 150°C or 450°C, that provides planarization after a very deep etching step in silicon is presented. Resist spinning and layer patterning as well as realization of bridges or cantilevers across deep holes becomes possible. The sacrificial wafer bonding technique contains a wafer bond step followed by an etch back. Results of (1) polymer bonding followed by dry etching and (2) anodic bonding combined with KOH etching are discussed. The polymer bond method was applied in a strain based membrane pressure sensor to pattern the strain gauges and to provide electrical connections across a deep corrugation in a thin silicon nitride membrane by metal bridge

Fundamental study on a thin-film ae sensor for measurement of behavior of a multi-pad contact slider

To study the fundamental dynamic characteristics of a multi-pad slider for contact recording, we developed a thin-film piezoelectric acoustic emission array sensor on an Si-suspension with an array pattern similar to that of contact pads. Experiments showed that the sensitivity of the sensor is about 0. 11 V/N (slider thickness: 0.2 mm) and that each array sensor designed here is not influenced by the acoustic waves which occur due to contact with other contact pads, so the contact or non-contact condition of each pad can be measured

Electrostatic microactuators with integrated gear linkages for mechanical power transmission

In this paper a surface micromachining process is presented which has been used to fabricate electrostatic microactuators that are interconnected with each other and linked to other movable microstructures by integrated gear linkages. The gear linkages consist of rotational and linear gear structures and the electrostatic microactuators include curved electrode actuators, comb drive actuators and axial gap wobble motors. The micromechanical structures are constructed from polysilicon. Silicon dioxide has been used as a sacrificial layer and silicon nitride was used for electrical insulation. A cyclohexane freeze drying technique is used to prevent problems with stiction. The actuators, loaded with various mechanisms, have been driven successfully by electrostatic actuation. The work is a first step towards mechanical power transmission in micromechanical system