Abstract of the diploma project reportNovember 24, 2010

Hanoi, Vietnam

DESIGN, CALCULATION AND SIMULATION 3 DOF CAPACITIVE FORCE SENSOR

Lã Xuân HùngStudent of Mechatronics 2 Class

Institute of Mechanical Hanoi University of Science and Technology

xuanhung.vaeco@gmail.com

ABSTRACT

This paper presents the overview of Micro Electronics Mechanical Systems and design calculation and simulation 3 dof the capacitive force sensor process.Using the ANSYS 12.0 software to simulation and suggest the optimum model for the manufacturing process.

I. INTRODUCTION

Microelectromechanical systems (MEMS) are small integrated devices or systems that combine electrical and mechanical components.

The term "MEMS" was coined around 1987, when a series of three workshops on microdynamics and MEMS was held in July 1987 in Salt Lake City, Utah; in November 1987 in Hyannis, Massachusetts; and in January 1988 in Princeton, New Jersey. These workshops ushered in a new era of microdevices. Equivalent terms for MEMS include "microsystems," which is preferred in Europe, and "micromachines," which is favored in Japan. MEMS is an application driven and technology limited, and has emerged as an interdisciplinary field that involves many areas of science and engineering.

II. WHY MEMS TECHNOLOGYAdvantages offered:- Miniaturiation of existing devices.- Development of new devices based on principles that do not work at lager

scale.- Development of new tools to be interactive with the micro-world.

III. MATERIALS FOR MEMS AND APPLICATION

III.1. MEMS Market[1] Data processing ( print devices…); [2] Transportation Sector; [3] Handheld and Consumer Electronics Industry; [4] Biomedical Appliations; [5]Aerospace, Defence and Homeland Security; [6]Industrial Automation and process Control.

III.2. MaterialsThere are three basic requirements of material selection for MEMS devices:(a) Ability appopriate with manufacturing of semiconductor.(b) Electric characterize as well as mechanical characterize.(c) Low residual stress.

III.3. Applications of MEMS in VietNam+ International training institute for materials science (Hanoi University of

Science and Technology).+ Institute of materials science (Vietnam’s academy of science and technology).+ Micro-nano Library (Vietnam national University HoChiMinh City).

IV. MEMS INDUSTRIAL CHALLENGES AND TRENDS

1) Explore new frontiers. Many new frontiers of research and application were developing: biological research and medical instruments; nano-mems mixed technology.

2) New materials. Besides silicon and semiconductors, many other materials can be used for MEMS

3) Transfer the traditional useful MEMS to large scale applications to establish mass markets. This would build up MEMS industries to support the sustained MEMS research and development.There are two major directions:

+ Reduce the cost, raise yield and efficiency to cultivate mass market.+ Raise system performance to meet the special needs.

4) MEMS Network. There are needs of having many different functional systems and many similar function systems working together to perform required big tasks.

V. THEORY OF STATIC ELECTRICITYThis section to research about static electricity effects and electrostatic force

which occurs on two parallel plate as the normal force and tangential force. Since then built a formula of displacement of the pole based on the relationship between displacement, capacitance and force through changes in capacitance values.

VI. ANALYSYS FORCE SENSOR STRUCTUREStructure:

A R

F

C

B

D

1

DD

2

D

3D

4

C

S

C

R

C

c

C

c

C

p

C

p

C

f

C

f

R

F

+V

p-V

p

1. Cross beam (Fig. a))2. Straight comb (Fig. b))3. Cross beam as crabs (Fig. c))

(a) (b)

(c)

VII. CALCULATE THE FORCE, SIMULATE THE DISPLACEMENT AND FREQUENCY VIBRATION

Use ANSYS to calculate the moment when applied to the sensor cause the change of voltage via structure simulation method. There by suggesting the temporary parameter of sensor.

Cố định

Bản cực trênBản

cực dướ

i

Dầm

thẳng

Răng lược cố

định

Dầm càng cua

Răng lược di trượtCố

định

Bản cực trên

Bản cực trên

Dầm càng cua

VIII. THE PROCESS TECHNOLOGY USED TO MANUFACTURE THE SENSOR

Step 1: PreparationSOI wafer is cleaned by acetone and piranha, heated at about 150-200ºC and

coating the primer layer to improve adhesion between the wafer and the photo resist layer.Step 2: Process to formative the upper- surface

Spin photo resist, soft baking, exposure, rinse, hard baking.Step 3: Deep reactive-ion etching (DRIE)

This is a highly anisotropic etch proces used to create deep, steep-sided holes and trenches in wafers with high aspect radio 20:1. Step 4: Evaporate metallic and wiring up to the Glass PyrexStep 5: Anodic Bonding Step 6: Vapor HF acid to etch Silicon oxide layer.

Major steps for sensor fabrication process

CONCLUSION

This paper presents the overview of Micro Electronics Mechanical Systems , the knowledge of electrostatic effect, step by step stimulation and provide structure geometry of 3 dof capacitive force sensor. But the scheme is only stop the stage of understanding the process of fabrication. Hopefully in the thread I will go into the experimental fabrication of sensor to measure the force applied.

REFERENCE

[1] Nguyen Viet Hung, Nguyen Trong Giang, “Ansys và mô phỏng số trong công nghiệp phần tử hữu

hạn ”, Sciences and engineering Publishing, 2003

[2] M.H Bao, “Micro mechanical transducers: pressure sensors, Acceler-ometers and gyroscopes?,

Handbook of sensors and actuators , vol. 8” Elsevier, Amsterdam, 2000.

[3] Grant McFarland, “Microprocessor Design- A Practice Guide from Design Planning to

Manufacturing”, McGraw-Hill Publishing Companies. Inc, 2006.

[4] Phuc Hong Pham, Dzung Viet Dao, Satoshi Amava, Ryoji Kitada, Susumu Sugiyama, “Straight

movement of micro containers based on ratchet mechanisms and electrostatic comb-drive actuators ”,

Journal of Micro-mechanics and Microengineering, 2006, vol 16, p2532- 2538.