© march 10, 2008, dr. lynn fuller, professor bulk micromachined mems laboratory page 1 rochester...

© March 10, 2008, Dr. Lynn Fuller, Professor

Bulk Micromachined MEMS Laboratory

Rochester Institute of TechnologyMicroelectronic Engineering

ROCHESTER INSTITUTE OF TECHNOLOGYMICROELECTRONIC ENGINEERING

Rev. 3-10-2008 MEM_BULK_2007_08.ppt

Bulk Micromachined Laboratory Project

Dr. Lynn Fuller,Ivan Puchades

Webpage: http://people.rit.edu/lffeee Rochester Institute of Technology

82 Lomb Memorial DriveRochester, NY 14623-5604

Tel (585) 475-2035Fax (585) 475-5041

Email: [email protected] Department webpage: http://www.microe.rit.edu

http://people.rit.edu/lffeee

mailto:[email protected]

http://www.microe.rit.edu/

http://www.microe.rit.edu/




OUTLINE

Lab Project ExpectationsLab requirementsDesign considerationsMaskmakingTesting ApproachTest Results




LAB PROJECT EXPECTATIONS

Objective: design, fabricate and test a MEMS device utilizing the provided process flow.

Lab project is 50% of grade Meet all required project timelines 33% Weekly attendance and participation 33% Quality of work 33%

Project timelines Design calculations and 1st Draft layout design 2rd week Final layout design in dropbox 3rd week Report theory section and test plan 5th week Final presentation 11th week Final report 11th

week




LAB REQUIREMENS AND TOOLS

Design: Mentor graphics IC Layout in CE VLSI lab

Account to be provided by TA during second week Review mems_cad bulk_20072.pdf posted on

http://people.rit.edu/lffeee/emcr870.htm Fabrication

Complete safety training and pass safety exam by 3rd week http://smfl.microe.rit.edu/events.php

Complete your lab notebook, sign each page, date each page, diary format, comments and observations, etc.

Fabrication schedule will be reviewed and emailed to students on Fridays. Email TA ([email protected]) with available hours

during the week. One 3-hour block (AM or PM) is required per week plus the 1 hour review session on Friday at 1:00pm

http://people.rit.edu/lffeee/emcr870.htm

http://smfl.microe.rit.edu/events.php




RIT MEMS BULK PROCESS

1 P+ Diffused Layer (90 Ohm/sq)1 Poly layer (40 Ohm/sq)1 metal layer (Al 1µm thick)30-40 µm Si diaphragmTop hole




DESIGN GUIDELINES

Microelectromechanical SystemsThe basic unit of distance in a scalable set of design rules is called

Lambda, For the current MEMS process is ten microns (10 µm)

The process has eight mask layers, they are:

P++ Diffusion (Green)(layer 1)Poly Resistor (Red)(layer 2)Contact (Gray)(layer 3)Metal (Blue)(layer 4)Diaphragm (Purple) (layer 5)

/tools/ritpub/process/mems_bulk_072




DESIGN CONSIDERATIONS

Building blocks of a microfluidic system (lab on a chip)

[24] Pinget, M. et al, “Multicentre trial of a programmable implantable insulin pump in type 1 diabetes”, Int. J. of Anaesthesian, vol. 6, pp. 843-846, 1994.




POSSIBLE DEVICES

Thermally actuated bimetallic micro-pumpThermally actuated bimetallic micro-pump with resistors for sensing and feedbackPressure Sensor, diffused resistors or poly resistorsThermocouples (Thermopile) on diaphragm with built-in heaterOptical PyrometerHeater on diaphragm either poly or diffused resistor heaterHeater plus temperature sensor (diffused heater, poly resistor sensor)Heater plus interdigitated chemical sensorHumidity sensorGas flow sensor single resistor anemometerGas flow sensor with heater and two resistorsTransistors and logic




POSSIBLE DEVICES

Pressure sensor Flow sensor

Thermocouples Micro-pump




DESIGN AREA

Design for a 2mm wide by 25 or 100µm tall channel. Probe pads and connections must be as large as

possible and away from channel, pads on one side is good, bigger is better.

Design space is 4mmx4mm.

4mm

4mm




PREVIOUS CLASS DESIGN




MASK ORDER FORM

Individual Student Designs are sent to a dropbox to be combined with other designs.

Click:File/Cell/Save/as:

/dropbox/MEMS_07_08/your_name_design

Example:/dropbox/MEMS_07_08/lynn_fuller_mirror




PREVIOUS LAB SECTION 1X ARRAY




PREVIOUS MASKS




ETCHED BULK MEMS PROCESS FLOW

3-15-07

1 Obtain qty 10, 4” n-type wafers 29 RCA Clean2 Wafer grind to 250um - 300um 30 Deposit 6000Å Poly LPCVD3 Polish back side 31 Spin on Glass, N-2504 CMP Clean 32 Poly Diffusion, Recipe 1205 RCA Clean 33 Etch SOG6 Grow masking oxide 5000 Å, Recipe 350 34 4 pt Probe7 Photo 1: P++ diffusion 35 Photo 3, Poly8 Etch Oxide, 12 min Rinse, SRD 36 Etch poly, LAM4909 Strip Resist 37 Strip resist

10 Spin-on Glass, Borofilm 100, include dummy 38 RCA Clean11 Dopant Diffusion Recipe 110 39 Oxidize Poly Recipe 25012 Etch SOG and Masking Oxide, 20min BOE 40 Deposit 8,000Å TEOS or LTO Oxide13 Four Point Probe Dummy Wafer 41 Photo 4, Contact Cut14 RCA Clean 42 Etch Oxide in BOE, Rinse, SRD15 500Å Pad Ox - recipe 250 43 Strip Resist16 Deposit 1500Å Nitride 44 RCA Clean, include extra HF step17 Coat back of wafer and protect edge 45 Deposit Aluminum, 10,000Å18 Plasma Etch Nitride on front of wafer, Lam-490 46 Photo 5, Metal19 Strip backside resist 47 Etch Aluminum, Wet Etch20 Remove pad oxide - 1min BOE 48 Strip Resist21 RCA Clean 49 Deposit 10,000Å LTO Oxide - ProTEK adhesion22 Grow 5,000Å of oxide - recipe 350 50 Spin coat PROTEK on front of wafer23 Photo 2: Backside Diaphragm 51 Etch Diaphragm in KOH, ~4 hours24 Coat front of wafer and protect edge 52 Strip PROTEK25 Etch oxynitride, 1 min 10:1HF 53 Pad oxide etch to remove 10,000Å LTO26 Plasma Etch Nitride on back of wafer, Lam-490 54 Test27 1.5min 10:1 HF to remove Pad ox28 Remove resist - solvent strip 5min + 5min rinse




PRESSURE SENSOR EXAMPLE

Front Back




FINITE ELEMENT ANALYSIS

Points of Maximum Stress




CALCULATION OF EXPECTED OUTPUT VOLTAGE

R1R3

R2R4

Gnd

+5 Volts Vo2

Vo1

The equation for stress at the center edge of a square diaphragm (S.K. Clark and K.Wise, 1979)

Stress = 0.3 P(L/H)2 where P is pressure, L is length of diaphragm edge, H is diaphragm thickness

For a 3000µm opening on the back of the wafer the diaphragm edge length L is 3000 – 2 (500/Tan 54°) = 2273 µm

Layout




CALCULATION OF EXPECTED OUTPUT VOLTAGE (Cont.)

Stress = 0.3 P (L/H)2

If we apply vacuum to the back of the wafer that is equivalent to and applied pressure of 14.7 psi or 103 KN/m2 P = 103 N/m2

L= 2273 µmH= 25 µm

Stress = 2.49E8 N/m2

Hooke’s Law: Stress = E Strain where E is Young’s Modulus = E

Young’s Modulus ofr silicon is 1.9E11 N/m2

Thus the strain = 1.31E-3 or .131%





The sheet resistance (Rhos) from 4 point probe is 61 ohms/sqThe resistance is R = Rhos L/WFor a resistor R3 of L=350 µm and W=50 µm we find:

R3 = 61 (350/50) = 427.0 ohms

R3 and R2 decrease as W increases due to the strainassume L is does not change, W’ becomes 50+50x0.131%W’ = 50.0655 µmR3’ = Rhos L/W’ = 61 (350/50.0655) = 426.4 ohms

R1 and R4 increase as L increases due to the strainassume W does not change, L’ becomes 350 + 350x0.131%R1’ = Rhos L’/W = 61 (350.459/50) = 427.6 ohms





Gnd

5 Volts

R1=427 R3=427

R2=427 R4=427

Vo2=2.5vVo1=2.5v

Gnd

5 Volts

R1=427.6 R3=426.4

R2=426.4 R4=427.6

Vo2=2.5035vVo1=2.4965v

No stressVo2-Vo1 = 0

With stressVo2-Vo1 = 0.007v

=7 mV




OUTPUT VOLTAGE VERSUS PRESSURE

Pressure (psi)

Vout(mV)

0 5 10 15

4

0

8

12

5-13-02




REFERENCES

1. Process Development for 3 D Silicon Microstructures, with Application to Mechanical Sensor Devices, Eric Peeters, Katholieke Universiteit Leuven, March 1994.]

2. United States Patent 5,357,8033. S.K. Clark and K.D. Wise, “Pressure Sensitivity in

Anisotropically Etched Thin-Diaphragm Pressure Sensors”, IEEE Transactions on Electron Devices, Vol. ED-26, pp 1887-1896, 1979.




FINAL LAB REPORT AND NOTEBOOK

1. Complete your lab notebook, sign each page, date each page, diary format, comments and observations, etc.

2. Write a ~4 page technical paper on this laboratory project. Use the standard IEEE conference proceedings format. See attached format and example paper.

Both Due 1st day of Finals Week

© march 10, 2008, dr. lynn fuller, professor bulk micromachined mems laboratory page 1 rochester...

Documents

week review mems

lynn fuller

rd week http

mems device

rd week final layout

current mems process

tools design

pm slide