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MICROELECTROMECHANICAL SYSTEMS ( MEMS ) HARIKRISHNA SATISH.T.

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Presentation on theme: "MICROELECTROMECHANICAL SYSTEMS ( MEMS ) HARIKRISHNA SATISH.T."— Presentation transcript:

1 MICROELECTROMECHANICAL SYSTEMS ( MEMS ) HARIKRISHNA SATISH.T

2 Introduction: MEMS stands for Micro-electromechanical systems, a manufacturing technology that enables the development of electromechanical systems using batch fabrication techniques similar to those used in integrated circuit (IC) design. MEMS stands for Micro-electromechanical systems, a manufacturing technology that enables the development of electromechanical systems using batch fabrication techniques similar to those used in integrated circuit (IC) design. They can range in size from micrometers to millimeters They can range in size from micrometers to millimeters MEMS integrate mechanical elements, sensors, actuators and electronics on a silicon substrate using a process technology called micro fabrication. MEMS integrate mechanical elements, sensors, actuators and electronics on a silicon substrate using a process technology called micro fabrication. Micro electro mechanical System (MEMS) is making and combining of miniaturized mechanical and electrical components on a common silicon substrate through micro fabrication technology. Micro electro mechanical System (MEMS) is making and combining of miniaturized mechanical and electrical components on a common silicon substrate through micro fabrication technology.

3 How MEMS work? The sensors gather information by measuring mechanical, thermal, biological, chemical, magnetic and optical signals from the environment. The sensors gather information by measuring mechanical, thermal, biological, chemical, magnetic and optical signals from the environment. The microelectronic Ics act as the decision-making piece of the system, by processing the information given by the sensors. The microelectronic Ics act as the decision-making piece of the system, by processing the information given by the sensors. Finally, the actuators help the system respond by moving, pumping, filtering or somehow controlling the Finally, the actuators help the system respond by moving, pumping, filtering or somehow controlling the surrounding environment to achieve its purpose. surrounding environment to achieve its purpose.

4 Manufacturing process:

5 The MEMS materials: The MEMS materials: Primarily silicon its compounds Primarily silicon its compounds other materials are quartz crystal, glass, metals such as aluminum, titanium, tungsten and copper other materials are quartz crystal, glass, metals such as aluminum, titanium, tungsten and copper polymers such as photo resist. polymers such as photo resist. What is Micromachining ? What is Micromachining ? Micromachining is a parallel (batch) process in which dozens to tens of thousands of identical elements are fabricated simultaneously on the same wafer. Micromachining is a parallel (batch) process in which dozens to tens of thousands of identical elements are fabricated simultaneously on the same wafer. Divided into three major categories: basic, advanced, and nonlithographic processes. Divided into three major categories: basic, advanced, and nonlithographic processes.

6 Basic process flow in micromachining: Basic process flow in micromachining: Figure : Illustration of the basic process flow in micromachining: Layers are deposited; photoresist is lithographically patterned and then used as a mask to etch the underlying materials. The process is repeated until completion of the microstructure.

7 BASIC PROCESS TOOLS Deposition Process Epitaxy: Epitaxy is a deposition method to grow a crystalline silicon layer over a silicon wafer, but with a differing dopant type and concentration Silicon Contain source gas [SiH 4 /SiCl 4 /SiH 2 Cl 2 ] Impurity dopants [AsH 3 ; PH 3 ] (Controlled) High Temperature ( ) [Controlled] Wafer Scale p-n junction for Controlled electrochemical etching

8 Oxidation: High-quality amorphous silicon dioxide is obtained by oxidizing silicon in either dry oxygen or in steam at elevated temperatures (850º–1,150ºC) Si + O 2 / Steam SiO 2 Si + O 2 / Steam SiO 2 It is Depend on Temperature, Oxidizing environment and Time. It is Depend on Temperature, Oxidizing environment and Time. Sputter Deposition: Sputter Deposition:

9 Evaporation Heated at high Temperature Heated at high Temperature (Scanning at high voltage electronic beam) (Scanning at high voltage electronic beam) (Water cooling of the target and (Water cooling of the target and shielding from X-ray) shielding from X-ray) Al, Si, Ti,Cr, Al 2 O 3 Evaporation Condenses on a substrate to form a film

10 CVD (Chemical Vapour Deposition) Deposition Of Polysilicon :- Deposition Of Polysilicon :- SiH 4 Si + 2H 2 SiH 4 Si + 2H 2 Polysilicon may be grown directly with doping. Deposition of Silicon dioxide :- Deposition of Silicon dioxide :- SiH 4 + O 2 SiO 2 + 2H 2 SiH 4 + O 2 SiO 2 + 2H 2 SiCl 2 H 2 + 2N 2 O SiO 2 + 2N 2 + 2HCl SiCl 2 H 2 + 2N 2 O SiO 2 + 2N 2 + 2HCl Si(OC 2 H 5 ) 4 + 2N 2 O SiO 2 + byproduct Si(OC 2 H 5 ) 4 + 2N 2 O SiO 2 + byproduct 25 p.a -150 p.a In CVD Chamber Oxide Doped Semiconductor High temperature Impurity P 2 O 5

11 Deposition of Silicon Nitrides Deposition of Silicon Nitrides 3SiH 4 + NH 3 Si 3 N H 2 3SiCl 2 H 2 + 4NH 3 Si 3 N 4 + 6HCl + 6H 2 2SiH 4 + N 2 2SiNH + 3H 2 SiH 4 + NH 3 SiNH + 3H 2 Silicon nitride is common in the semiconductor industry for the passivation of electronic devices because it forms an excellent protective barrier against the diffusion of water and sodium ions Silicon nitride is common in the semiconductor industry for the passivation of electronic devices because it forms an excellent protective barrier against the diffusion of water and sodium ions

12 Photolithography Photosensitive material Selectively expose to Light Exposed part (physical property change) Non-exposed part (remain same in physical properties) Perform Etching Deposition of metal or other thin film deposition

13 Etching: In etching, the objective is to selectively remove material using imaged photoresist as a masking template. Wet Etching :- Wet Etching :- Anisotropic Wet Etching : Anisotropic Wet Etching : Substrate Dipped into Removal of material Depending on the Crystallographic orientation KOH Solution

14 Electrochemical Etching

15 Reactive Ion Etching ( RIE ) Reactive Ion Etching ( RIE ) Process of reactive ion etching. Process of reactive ion etching. Substrate Reactor contain several gas Plasma is struck in the mixture Gas molecule into ions React with the surface of the material and etched Placed into

16 Deep Reactive Ion Etching ( DRIE ) Deep Reactive Ion Etching ( DRIE ) SF 6 isotopic Etching (SF 6 & O 2 etches the substrate) C 4 F 8 deposition SF 6 anisotropic etching for floor cleaning

17 Using these processes some micromachining methods are applied on silicon materials are: Using these processes some micromachining methods are applied on silicon materials are: A) Bulk micromachining: Bulk micromachining designates the point at which the bulk of the Si substrate is etched away to leave behind the desired micromechanical elements. The methods commonly used to remove excess material are wet and dry etching, allowing varying degree of control on the profile of the final structures. A) Bulk micromachining: Bulk micromachining designates the point at which the bulk of the Si substrate is etched away to leave behind the desired micromechanical elements. The methods commonly used to remove excess material are wet and dry etching, allowing varying degree of control on the profile of the final structures. B) Surface Micromachining: The MEMS fabrication process based on standard CMOS microelectronic processes. MEMS structures are photo lithographically patterned in alternating layers of deposited polysilicon and silicon dioxide, and then are "released" by dissolving away the silicon dioxide layers. B) Surface Micromachining: The MEMS fabrication process based on standard CMOS microelectronic processes. MEMS structures are photo lithographically patterned in alternating layers of deposited polysilicon and silicon dioxide, and then are "released" by dissolving away the silicon dioxide layers.

18 Applications of MEMS : inkjet-printer cartridges, inkjet-printer cartridges, accelerometer, accelerometer, miniature robots, miniature robots, micro engines, micro engines, inertial sensors, inertial sensors, micro actuators, micro actuators, optical scanners, optical scanners, fluid pumps, fluid pumps, chemical, pressure and flow sensors. chemical, pressure and flow sensors. Application in Radio frequency (RF) Application in Radio frequency (RF)

19 Reference :- By Maluf Nadim and Williams Kirt. By Maluf Nadim and Williams Kirt. An Introduction to Microelectromechanical Systems Engineering. An Introduction to Microelectromechanical Systems Engineering. By committee on Advanced Material and Fabrication. By committee on Advanced Material and Fabrication. Microelectromechanical Systems. Microelectromechanical Systems. The MEMS Handbook. The MEMS Handbook.

20 Thank You Thank You


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