Reductie van behuizingsspanningen in een micro-mechanische druksensor

In een micromechanische sensor wordt een zeer kleine flexibele structuur mechanisch vervormd als gevolg van een te meten grootheid. Volgens verscheidene transductieprincipes is het mogelijk om deze vervormingen om te zetten in een elektrisch signaal. Dit meetsignaal is dus een waarde voor de te meten grootheid, een drukverschil in dit artikel. Het is van groot belang dat de mechanische vervorming alleen door het srukverschil bepaald wordt en niet door storingsverschijnselen wordt beinvloed. Het behuizen van gevoelige micromechanische sensoren blijkt vaak dergelijke hinderlijke storingen te introduceren. Veel gevallen zijn bekend waarbij de microsensor na het plaatsen in de behuizing niet meer correct bleek te werken, of zelfs volledig kapot ging. In dit artikel zal een oplossing voor het reduceren van behuizingsspanningen worden aangedragen. Een mechanische ontkoppelzone wordt geintroduceerd, die de behuizingsspanning reduceert, maar de spanning als gevolg van het drukverschil niet beinvloedt

Planarization and fabrication of bridges across deep groves or holes in silicon using a dry film photoresist followed by an etch back

A technique is presented that provides planarization after a very deep etching step in silicon. This offers the possibility for not only resist spinning and layer patterning but also for realization of bridges and cantilevers across deep grooves or holes. The technique contains a standard dry film lamination step to cover a wafer with a 38 mu m thick foil. Next the foil is etched back to the desired thickness of a few micrometres. This thin film facilitates resist spinning and high-resolution patterning. The planarization method is demonstrated by the fabrication of aluminium bridges across a deep groove in silicon

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

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

Membranes fabricated with a deep single corrugation for package stress reduction and residual stress relief

Thin square membranes including a deep circular corrugation are realized and tested for application in a strain-based pressure sensor. Package-induced stresses are reduced and relief of the residual stress is obtained, resulting in a large pressure sensitivity and a reduced temperature sensitivity. Finite element method simulations were carried out, showing that the pressure-deflection behaviour of the structure is close to that of a circular membrane with clamped edge but free radial motion

Novel microstructures and technologies applied in chemical analysis techniques

Novel glass and silicon microstructures and their application in chemical analysis are presented. The micro technologies comprise (deep) dry etching, thin layer growth and anodic bonding. With this combination it is possible to create high resolution electrically isolating silicon dioxide structures with aspect ratio's similar to those possible in silicon. Main applications are chemical separation methods such as high performance liquid chromatography (HPLC) or electrophoresis (HPCE). Beside these channel structures, a capillary connector with very low dead and mixing volume has been designed and fabricated for use in (correlation) electrophoresis, and tested by means of precision of consecutive single injection

Modular concept for fluid handling systems:a demonstrator micro analysis system

A modular planar concept for fluid handling microsystems is presented. The concept is based on a planar Mixed Circuit Board with electrical and fluidic interconnections acting as a substrate for sensor and actuator modules. Several modules realised within this concept are presented, and the design as well as modelling and simulation of the fluidic components and systems is discussed. Furthermore, the general application of this concept in micro analysis systems is considered. Finally, the modular concept is demonstrated by a micro chemical analysis system containing micro-pumps, flow sensors, an optical absorption cell and control electronics

A system to measure 3-directional relative displacements for a biomedical application

A micro system for measuring the relative displacements between a bone and an implant in a prosthetic hip of a human being has been realized. Novel are the small dimensions of the system combined with the possibility to measure relative displacements in three directions. The system consists of a microsensor body, a mechanical transducer element made by precision mechanics, electronics, and the final package. The realization and test results of a prototype system are presented. Typical ranges for these prototypes are ±500 μm for lateral directions and ±50 μm in axial direction