Bulk MEMS Layout 2017 Dr. Lynn Fuller, Casey Gonta, Patsy Cadareanu Webpage:

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1 ROCHESTER INSTITUTE OF TECHNOLOGY MICROELECTRONIC ENGINEERING Bulk MEMS Layout 2017 Dr. Lynn Fuller, Casey Gonta, Patsy Cadareanu Webpage: 82 Lomb Memorial Drive Rochester, NY Department webpage: Bulk_MEMS_Layout_2017.ppt Page 1

2 INTRODUCTION This document shows layout details for the 2017 Bulk MEMS class project. Pressure sensors and other devices based on a thin diaphragm (10um) of single crystal silicon can be realized. Resistors in the diaphragm will exhibit large changes in resistance in response to stress through the piezoresistance effect. This version of the process has three photolithographic layers applied to the top side of the wafer and one to the back side of the wafer. The starting wafer is a special double sided polished 150mm SOI wafer with 10 um silicon on a 1um buried oxide (BOX) on a 500um handle wafer. Page 2

3 GENERIC DEVICE CROSS SECTION n - type p - type 1 um BOX 10um hole etched from back side 500um Diffusion (Green) Layer 1.gds #1 Backside Hole (Purple Outline) Layer 2, gds#4 Contact Cut (White) Layer 3, gds#6 Metal (Blue) Layer 4, gds#7 Outline (Yellow Outline), gds# 9 Outline is only for layout, drawing a 4.5mm by 4.5mm outline, the maximum area for individual device designs. Page 3

4 STARTING WAFER N-type, Phosphorous, (100), 10um+/-1um, 1-10 ohm-cm BOX Oxide 1um +/-5% Handle Wafer Thickness 500um +/- 10um 1-10 ohm-cm 150mm diameter SOI wafers, Polished both top and bottom Page 4

5 10 mm MEMS MULTICHIP PROJECT TEMPLATE Total 10 mm by 10 mm including 1 mm for sawing into 4 chips. Wafer sawing is easier if all chips are the same size R1 R3 R2 R4 Your Design 4.5mm by 4.5mm design space for each project 4 different projects 5 mm Page 5

6 10 mm Total 10 mm by 10 mm including 1 mm for sawing into 4 4.5mm by 4.5 mm chips BULK MEMS CHIP FINAL LAYOUT Page 6

7 PRESSURE SENSOR + HEATER Pressure Sensor Heater Overlay and Resolution Diffused Resistors Length = 200um Width = 20 um Note: upper left is not connected so individual resistances can be measured. Page 7

8 BULK MEMS PROCESS FLOW 1. Starting wafer, 10um SOI 2. Grow 5000Å oxide, Recipe PH03 level 0, Marks 4. ET06 Wet Etch Alignment Marks 5. Strip resist and clean 6. Grow another 5000Å oxide, Recipe PH03 level 1 Diffusion + Hand Coat back of wafer with PR + oven bake 8. ET06 Wet Etch Oxide 9. ET07 Resist Strip, Solvent Strip 10. CL01- RCA Clean 11. IM01 - Implant 2E15, B11, Energy 80Kev 12. OX Å Dry Oxide, Anneal 13. PH03 level 2 Contact Cut + Hand coat back of wafer with PR + oven bake 14. ET29 Etch CC Oxide 15. ET07 - Resist Strip, Solvent Strip 16. CL01 RCA Clean two HF dips 17. Sputter metal 1um, 30min 18. PH03 level 3 Metal 19. ET55 Metal Etch wet 20. Strip Resist Solvent Strip 21. Sinter wafers 22. PH03 level 4 Back Hole +Hand Coat Front with PR +oven bake 23. Etch Oxide in Holes on Back 24. STS Etch Silicon from Back 25. TE01 wafer level testing 26. SAW1 Saw wafers 27. Packaging and Testing 28. Documentation Page 8

9 CALCULATION OF EXPECTED OUTPUT VOLTAGE +5 Volts R1 R3 R2 R4 Vo1 Gnd Vo2 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 Page 9

10 PRESSURE SENSOR CHIP Pressure Sensor Heater Overlay and Resolution Diffused Resistors Length = 200um Width = 20 um Note: upper left is not connected so individual resistances can be measured. Page 10

11 PRESSURE SENSOR CHIP Diffused Resistors Length =??? um Width =?? um Diaphragm 1000 um Page 11

12 PRESSURE SENSOR CHIP Page 12

13 FLOW CHANNEL WITH HEATERS Page 13

ELECTRICAL MEASUREMENTS Measured resistance: Rtop = 3.538 Kohm Rright = 3.537 Kohm Rbottom = 3.

14 ELECTRICAL MEASUREMENTS Measured resistance: Rtop = Kohm Rright = Kohm Rbottom = Kohm Rleft = Kohm Measured Voltages: Vo1 = V Vo2 = V Vo1-Vo2 = 31.0 mv Rhos ~= 150 ohm/sq Page 14

15 EXPRESSION FOR RESISTANCE R = Ro [ 1 + p L s xx + p T (s yy + s zz )] where Ro = (L/W)(1/(qµ(N,T) Dose)) p L is longitudinal piezoresistive coefficient p T is transverse piezoresistive coefficient s xx is the x directed stress, same direction as current s yy is the y directed stress, transverse to current flow s zz is the z directed stress, transverse to current flow In the <110> direction p L (E -11 /Pa) p T (E -11 /Pa) Electrons holes (100) wafer <110> directions Page 15

16 HEATERS AND TEMPERATURE SENSORS Thermocouple Heater Resistor Sensor Page 16

SEEBECK EFFECT When two dissimilar conductors are connected together a voltage may be generated if the junction is at a temperature different from the temperature at the other end of the conductors

17 SEEBECK EFFECT When two dissimilar conductors are connected together a voltage may be generated if the junction is at a temperature different from the temperature at the other end of the conductors (cold junction) This is the principal behind the thermocouple and is called the Seebeck effect. DV = a 1 (T cold -T hot ) + a 2 (T hot -T cold )=(a 1 -a 2 )(T hot -T cold ) Hot Where a 1 and a 2 are the Seebeck coefficients for materials 1 and 2 Material 1 Material 2 Cold DV Nadim Maluf, Kirt Williams, An Introduction to Microelectromechanical Systems Engineering, 2 nd Ed Page 17

18 VLSI DESIGN LAB Page 18

GETTING STARTED WITH LAYOUT EDITOR IC Usually the workstation screen will be blank, press any key to view a login window. Login or switch user and then login.

19 GETTING STARTED WITH LAYOUT EDITOR IC Usually the workstation screen will be blank, press any key to view a login window. Login or switch user and then login. Login: username (RIT computer account) Password: ******** The screen background will change and your desktop will appear. On the top of the screen click on Applications then System Tools then Terminal. A window will appear that has a Unix prompt inside. Type the command module load mentor Type ic <RET>, it will take a few seconds, then the Pyxis Layout user interface will appear. Maximize the Pyxis Layout window. Page 19

USING THE HP WORKSTATIONS AND MENTOR GRAPHICS CAD TOOLS - PROCESS AND GRID In the session menu palette on the right hand side of the screen, under Layout, select New, using the left mouse button.

) At the top left of the window check that the process is ritpmos not Default.

20 USING THE HP WORKSTATIONS AND MENTOR GRAPHICS CAD TOOLS - PROCESS AND GRID In the session menu palette on the right hand side of the screen, under Layout, select New, using the left mouse button. For cell name type device#. Set the process by typing /tools/ritpub/process/mems-2014 in the process field. Leave the Rules field blank. Click OK (twice?) At the top left of the window check that the process is ritpmos not Default. If not correct go to top banner click on Context>Process>Set Process The Layer Palette should show the layers you expect to used for your device layout. (Diffusion, Oxide Contact and Metal) On top banner select Setup>Preferences>Display>Rulers/Grid Set Snap to 10 and Rochester 10 Institute as shown. of Technology (or other values as necessary) Click OK Page 20

21 SET UP LAYER PALETTE Change colors, fill, line and names Page 21

LAYER NAMES, NUMBERS AND COLORS Layer # 1 4 6

22 LAYER NAMES, NUMBERS AND COLORS Layer # Set up layer palette as shown Draw a box in each layer Check that layer number is correct Select a single box, read message Page 22

23 DRAW OUTLINE OF THE 4500um by 4500 um AREA Draw the outline 4500um by 4500um Once your design is complete add boxes for each layer in the four corners to define the size of the layout for each layer. Add a small box for each layer and align it exactly in the lower left corner of the outline box. (~ 10um x 10um) Do similar in the other 3 corners of the outline box. (Copy, Paste, Rotate.. Move) Page 23

24 USING THE HP WORKSTATIONS AND MENTOR GRAPHICS CAD TOOLS WORKSPACE, LOCATION Hit minus sign twice to zoom out..+ to zoom in see workspace as shown below The plus mark + is (0,0) the small dots are the 10 um grid the large dots are the 100um grid. The mouse curser is shown by the diamond and is at (100um,100um) as indicated by the cursor position at the top of the workspace. Page 24

USING THE HP WORKSTATIONS AND MENTOR GRAPHICS CAD TOOLS SELECTING OBJECTS Select Easy Edit, Select Shape. Draw boxes by click and drag of mouse. Unselect by pressing F2 function key.

25 USING THE HP WORKSTATIONS AND MENTOR GRAPHICS CAD TOOLS SELECTING OBJECTS Select Easy Edit, Select Shape. Draw boxes by click and drag of mouse. Unselect by pressing F2 function key. Highlight a layer in the layer palette prior to drawing boxes. Exit drawing by pressing ESC. Unselect by pressing F2. Selecting multiple objects is defined in Setup>Preferences>Selection Unclick Surrounding the select rectangle to not select the cell outline Page 25

26 DRAWING BOXES AND OTHER SHAPES Select easy edit, right click and select Show Scroll Bars, scroll through the various edit commands such as Shape, Copy, Move, Notch,.. DRAW BOXES by highlighting the layer/color desired than click on Shape and draw a box by click and drag of the mouse. Unselect by pressing F2 function key. The following command will draw a 3000 µm by 3000 µm box with layer 4 color/shading. Put the curser in the workspace and start typing (try typing the number 3). A text line window will pop up. If the command has a typo just start typing again and use the up arrow to recall previous text. command $add_shape([[0,0],[3000,3000]],4) Location of lower left corner Location of upper right corner Box Color The Notch command is useful to change the size of a selected box or alter rectangular shapes into more complex shapes. Page 26

DRAWING CIRCLES DRAW CIRCLES by typing $set_location_mode(@arc) return.

$add_shape($get_circle([0,0],[100,0],300),3) To reset to rectangles type $set_location_mode(@line) return.

27 DRAWING CIRCLES DRAW CIRCLES by typing return. The following command will draw a 100µm radius circle centered at (0,0) using 300 straight line segments. $add_shape($get_circle([0,0],[100,0],300),3) To reset to rectangles type $set_location_mode(@line) return. MOVE, COPY, DELETE, NOTCH, etc: Selected objects will appear to have a bright outline. Selected objects can be moved (Move), copied (Copy), deleted (Del), notched (Notc). When done unselect objects, press F2. Change an Object to another layer: Selected object(s) click on Edit on the top banner, select Change Attributes, change layer name to the name you want. When done press F2 to unselect Page 27

28 USING THE HP WORKSTATIONS AND MENTOR GRAPHICS CAD TOOLS - OTHER ZOOM IN OUT: pressing the + or - sign on right key pad will zoom in or out. Also pressing shift + F8 will zoom so that all objects are in the view area. Select View then Area and click and drag a rectangle will zoom so that the objects in the rectangle are in the view area. MOVING VIEW CENTER: pressing the middle mouse button will center the view around the pointer.\ ADDING TEXT: Add > Polygon Text click on layout where you want it located. Select the text box and Edit > Change > Attributes, change layer to Diffusion.int or some other layer, change pgtext to the text you want, change scale to some number like 3.0 SCREEN PRINT: Click on MGC and select Capture Screen. Enter file name and location such as Lynn.png and Desktop. After saving you can use a flash drive and transfer the file to another computer. LOG OUT: upper right of screen click on name and select LOG OUT Page 28

29 GDS FILE GENERATION Once the cell design is completed export the GDS file for maskmaking. Select Translate on the top banner and then Write GDSII Output file needs full path name and.gds extension. Cell layout name Save to your desktop Page 29

EXPORT CELL DESIGN AS GDS II FILE Export as filename.gds Email to Dr.

30 EXPORT CELL DESIGN AS GDS II FILE Export as filename.gds to Dr. Fuller Cell layout name Save to your desktop Page 30

31 MASK ORDER FORM Dr Fuller RIT BULK-MEMS-2017-Final.gds 4 10mm x 10mm x X yes, 4 levels per plate Page 31

32 MASK ORDER FORM DETAILS Layer Reticle Name Design.gds Layer # s Boolean Function Dark/ Clear Comment 1 st Diffusion 1 1 Inverted Dark Mirror 2 nd Cut 6 6 Inverted Dark Mirror 3 rd Metal 7 None Clear Mirror 4 th Hole 2 2 Inverted Dark No mirror Hole pattern is put on the back side of the wafer so it does not get mirrored. All the other layers are mirrored. Design Layer 9 Out (outline) is not used. It is only for placement of projects on the multi-project reticle template. Page 32

33 LAYER 1 DIFFUSION AND LAYER 2 CUT DIFFUSION.gds #1 CUT.gds #6 Page 33

34 LAYER 3 METAL AND LAYER 4 BACKSIDE HOLE METAL.gds #7 BACKSIDE HOLE.gds #4 Page 34

35 SUMMARY This project allows students to see the entire process for design, fabrication, packaging and testing of a MEMS based Microsystem. Page 35

36 1. Dr. Lynn Fuller s webpage 2. more REFERENCES Page 36

37 HOMEWORK BULK LAYOUT 1. Draw the layout for a MEMS pressure sensor. Use a different color for each layer. Indicate dimensions in um. Page 37

Introduction to Computer Aided Design (CAD) Dr. Lynn Fuller Webpage:

ROCHESTER INSTITUTE OF TECHNOLOGY MICROELECTRONIC ENGINEERING Introduction to Computer Aided Design (CAD) Dr. Lynn Fuller Webpage: http://people.rit.edu/lffeee 82 Lomb Memorial Drive Rochester, NY 14623-5604