A three terminal cantilever beam can be used as a switch and also for material and process characterization. This paper deals with process optimization for its fabrication with surface micromachining steps compatible with standard integrated circuit manufacturing technology. The problems encountered in each step of fabrication and possible solutions are discussed in detail. The process makes extensive use of polysilicon deposited by Low Pressure Chemical Vapour Deposition for contacts, sacrificial oxide as well as the structural layer. © 2007 IEEE.

Enakshi Bhattacharya

Department of Electrical Engineering

Chemical vapor deposition

electric conductivity

Electronics industry

Integrated circuits

Micromachining

Optical design

Optimization

Polysilicon

Port terminals

Semiconductor device manufacture

Semiconductor device models

Semiconductor materials

Semiconductor switches

Standards

SURFACE MICROMACHINING

cantilever

INTEGRATED CIRCUIT MANUFACTURING

LOW PRESSURE CHEMICAL VAPOUR DEPOSITION

MICROMACHINED CANTILEVERS

POLY OXIDE

Possible solutions

PROCESS CHARACTERIZATION

PROCESS-OPTIMIZATION

SACRIFICIAL OXIDE

Stiction

Structural layers

Semiconductor devices

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

A novel polysilicon based process for three terminal surface micromachined cantilever

Proceedings of the 14th International Workshop on the Physics of Semiconductor Devices, IWPSD

In this paper, we estimate the stiction force from electrical (current-voltage) measurements on surface micromachined polysilicon cantilever beams. A bias voltage was applied between the beam and the substrate. At the pull-in voltage, the beam collapsed to the substrate and the current rose rapidly from zero. Similarly, at the pull-out voltage during bias sweep back, the current dropped rapidly to zero when the contact between the beam and the substrate was broken. An analytic model for the stiction force was developed in terms of the pull-in and pull-out voltages and was used to estimate a stiction force of about 70 nN from the measured electrical characteristics. This method of characterization is suitable for use in packaged devices. An analytic model was developed to estimate stiction force from optical surface-profile measurements of the curvature of long collapsed cantilever beams in a cantilever-beam array, in the absence of any electrostatic actuation. The force per unit length of about 14 nN/m thus obtained was used to compare the effects of surface roughness on stiction. © 2007 IEEE.

Journal of Microelectromechanical Systems

Estimation of stiction force from electrical and optical measurements on cantilever beams

Stiction is a major failure mechanism during the operation of accelerometers and hence it is important to know the stiction force that the structures encounter during use. We explore the possibility of devising an electrical technique for the direct measurement of in use stiction force. We have designed and fabricated three terminal test structures to measure both vertical and horizontal in use stiction. The measurement is not visual and is based on I-V data with the possibility of automation in the future. The structure consists of cantilever beams of different lengths each with an actuating pad and a detection pad. We measure the pull in voltage applied to the actuating pad, VPI, required to bring the cantilever beam in contact with the detection pad and the pull out voltage, VPO, at which the contact is broken. Using the Finite Element tool, ANSYS, a coupled electromechanical model is developed to determine the stiction force from the pull-in and pull-out voltages. We discuss the measurements in terms of the advantages and the shortcomings. We also discuss the sensitivity of the model to various material and geometric parameters and to the accuracy of the measurement.

Proceedings of SPIE - The International Society for Optical Engineering

A three terminal test structure to measure stiction force using I-V data

Journal of Applied Physics

Growth process and properties of silicon nitride deposited by hot-wire chemical vapor deposition

The various micromachining processes required for microengineering and for the successful realisation of microeletromechanical systems on Si are presented. The techniques presented include bulk and surface micromachining, Si fusion bonding, and the lithography, electroforming and micromoulding (LIGA) process. The paper also includes discussion on the markets, applications and future trends for microenginerated products.

Fulltext

Defence Science Journal

Micromachining for microelectromechanical systems

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures

Critical Review: Adhesion in surface micromechanical structures

Journal	Proceedings of the 14th International Workshop on the Physics of Semiconductor Devices, IWPSD
Open Access	No