Gig Ohm Resistors Fabrication Process
ROCHESTER INSTITUTE OF TECHNOLOGY
MICROELECTRONIC ENGINEERING
Gig Ohm Resistor Process Details
Dr. Lynn Fuller/Paul John
Webpage: http://people.rit.edu/lffeee
Microelectronic Engineering
Rochester Institute of Technology
82 Lomb Memorial Drive
Rochester, NY 14623-5604
Tel (585) 475-2035
Fax (585) 475-5041
Email: Lynn.Fuller@rit.edu
MicroE Webpage: http://www.microe.rit.edu
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
3-24-2008 GigOhmResistors.ppt
Page 1
Gig Ohm Resistors Fabrication Process
INTRODUCTION
This project is to design and make Gig Ohm Resistors. The process
will use ion implanted (Boron) poly silicon resistors. The design is
for discrete devices of size suitable for automated pick and place
surface mounting for printed circuit board assembly. The individual
resistors are 2mm x 3mm and eight different designs are arranged in
an array which will be cut into individual chips at the end of the
process. The first run will use aluminum metal. Future runs will use
a metal stack of aluminum, chrome, nickel, and solder.
Applications for resistors of this high value are MOSFET biasing of
high input impedance amplifiers, charge sensors for piezoelectric
(quartz) pressure sensors, and more. In these applications the exact
value is not usually important.
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Page 2
Gig Ohm Resistors Fabrication Process
LAYOUT
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Page 3
Gig Ohm Resistors Fabrication Process
ALIGNMENT KEY LOCATIONS, CHIP SIZE, ETC.
Lower Left Corner =(0,0)
Upper Right Corner = (9400,6400)
Step Size in X = 9.6 mm
Step Size in Y = 6.6 mm
Center of Die = (4700 , 3200)
Location of PA alignment Mark = Center of Die = (4700,3200)
B scope (Y-Direction) Fine Alignment 20P4F Island Center = 4955,3680
B scope (Y-Direction) Fine Alignment 20P4F Window Center = 4955,3500
C scope (X-Direction) Fine Alignment 20P4F Island Center = 4550,3700
C scope (X-Direction) Fine Alignment 20P4F Window Center = 4350,3699
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Page 4
Gig Ohm Resistors Fabrication Process
PROCESS STEPS
Gig Ohm Resistor process
1. ID01 scribe
2. CL01 RCA clean
3. OX05--- 30,000 wet oxide
4. CV01 deposit poly
5. IM01 – Ion Implant poly Si
6. PH03 – 1 – poly
7. ET08 poly etch
8. ET07 strip resist
9. CL01 RCA clean
10. OX08 – poly reox
11. CV03 – LTO
12. OX08 DS anneal
13. PH03 – 2 CC
14. ET10 etch CC
15. ET07 strip resist
16. CL01 RCA Clean, modified
17. ME01 Deposit Metal
18. PH03 -3- metal
19. ET05 etch metal
20. ET07 strip resist
21. SI01 SINTER
22. TE01 Test 1
23. SA01 Saw Wafer
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Page 5
Gig Ohm Resistors Fabrication Process
STARTING WAFER P-TYPE, 35 OHM-CM
For this project the starting silicon wafer type and resistivity is not that important
because the resistors will be made of poly silicon on an insulating oxide layer.
The starting wafer is only a substrate for the thin films on its surface.
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Page 6
Gig Ohm Resistors Fabrication Process
ID01 - IDENTIFY WAFER (SCRIBE WAFER)
D1
Paul John
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Page 7
Gig Ohm Resistors Fabrication Process
RCA CLEAN
APM
H2O – 4500ml
NH4OH–300ml
H2O2 – 900ml
75 °C, 10 min.
DI water
rinse, 5 min.
DI water
rinse, 5 min.
HPM
H2O–4500ml
HCL-300ml
H2O2 – 900ml
75 °C, 10 min.
H20 - 50
HF - 1
60 sec.
DI water
rinse, 5 min.
What does RCA
stand for?
ANSWER
SPIN/RINSE
DRY
PLAY
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Page 8
Gig Ohm Resistors Fabrication Process
RCA CLEAN
RCA Bench
Spin/Rinse/Dry Tool
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Page 9
Gig Ohm Resistors Fabrication Process
GROW 30,000 Å OXIDE
Push at 800 C in N2
Ramp to 1100 C in dry O2
Time = ~900 min. in wet O2
Ramp down to 800 C in N2
Pull at 800 C in N2
30,000 Å SiO2
Use Recipe 430 – Tube 1
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Page 10
Gig Ohm Resistors Fabrication Process
WET OXIDE GROWTH CHART
10
Oxide
Thickness
in microns
1
1300C
0.1
900C
0.01
1
Steam
10
100
Time in minutes
1000
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
BRUCE FURNACE RECIPE 430 – WET OXIDE 30,000Å
Recipe #430
1100°C
Boat Out Boat In
Load
Push
Stabilize
800 °C 800 °C
Ramp-Up
Soak
Anneal
Ramp-Down
Boat Out
Pull
800 °C
25 °C
Interval 0
Any
0 lpm
none
Interval 1
12 min
10 lpm
N2
Interval 2 Interval 3 Interval 4 Interval 5 Interval 6
15 min
10 lpm
N2
30 min
5 lpm
N2
5 min
5 lpm
O2
15 hrs
10 lpm
O2/H2
5 min
15 lpm
N2
Interval 7
Interval 8
60 min
10 lpm
N2
12 min
15 lpm
N2
At the end of a run the furnace returns to Interval 0 which is set for
boat out, 25 °C and no gas flow. The furnace waits in that state
until someone aborts the current recipe or loads a new recipe.
Wet Oxide Growth, Target 30,000 Å
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
30,000 Å OXIDE GROWTH
30,000 Å SiO2
Polysilicon, 3500A
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Page 13
Gig Ohm Resistors Fabrication Process
OXIDE COLOR VERSUS THICKNESS TABLE
Color
Tan
Brown
Dark Violet - Red Violet
Royal Blue
Light Blue - Metallic Blue
Metallic - very light Yellow Green
LIght Gold or Yellow - Slightly Metallic
Gold with slight Yellow Orange
Orange - Melon
Red Violet
Blue - Violet Blue
Blue
Blue - Blue Green
Light Green
Green - Yellow Green
Yellow Green
Yellow
Light Orange
Carnation Pink
Violet Red
Red Violet
Violet
Blue Violet
Yes!
Rochester Institute of Technology
Microelectronic Engineering
Silicon
To observe a valid color, the wafer must be observed perpendicular
to the surface under white (all wavelengths) light or the optical path
length will be different, hence the color will change with the angle.
Thickness
500
700
1000
1200
1500
1700
2000
2200
2500
2700
3000
3100
3200
3400
3500
3600
3700
3900
4100
4200
4400
4600
4700
Thickness
4900
5000
5200
5400
5600
5700
5800
6000
6300
6800
7200
7700
8000
8200
8500
8600
8700
8900
9200
9500
9700
9900
10000
Color
Blue
Blue Green
Green
Yellow Green
GreenYellow
Yellow -"Yellowish"(at times appears to be Lt gray or matellic)
Light Orange or Yellow - Pink
Carnation Pink
Violet Red
"Bluish"(appears violet red, Blue Green, looks grayish)
Blue Green - Green
"Yellowish"
Orange
Salmon
Dull, LIght Red Violet
Violet
Blue Violet
Blue
Blue Green
Dull Yellow Green
Yellow - "Yellowish"
Orange
Carnation Pink
No!
SiO2
© March 24, 2008, Dr. Lynn Fuller
Silicon
Page 14
SiO2
Gig Ohm Resistors Fabrication Process
TENCORE SPECTRAMAP
Measure Oxide Thickness
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Page 15
Gig Ohm Resistors Fabrication Process
REFLECTANCE SPECTROMETER
NANOSPEC FILM THICKNESS MEASUREMENT
INCIDENT WHITE LIGHT, THE INTENSITY OF THE
REFLECTED LIGHT IS MEASURED VS WAVELENGTH
3000 Å OXIDE
7000 Å OXIDE
MONOCHROMATOR
& DETECTOR


WHITE LIGHT SOURCE
OPTICS
WAFER
Rochester Institute of Technology
Microelectronic Engineering
Oxide on Silicon
Nitride
Neg Resist
Poly on 300-1200 Ox
Neg Resist on Ox 300-350
Nitride on Oxide 300-3500
Thin Oxide
Thin Nitride
Polyimide
Positive Resist
Pos Resist on Ox 500-15,000
© March 24, 2008, Dr. Lynn Fuller
Page 16
400-30,000 Å
400-30,000
500-40,000
400-10,000
300-3500
300-3500
100-500
100-500
500-10,000
500-40,000
4,000-30,000
Gig Ohm Resistors Fabrication Process
STEP ETCH APPARATUS
BUFFERED HF
Lower 1/4 inch every 45 seconds
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
ETCH STEPS IN OXIDE ON C1
5000 Å
BARE SILICON
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
DEPOSIT LPCVD POLY SILICON
Polysilicon, 3500A
LPCVD, 610C, ~45min
30,000 Å SiO2
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
DOPE POLY SILICON BY ION IMPLANT
Polysilicon, 3500A
30,000 Å SiO2
Wafer 1 Dose =
Wafer 2 Dose =
Wafer 3 Dose =
Wafer 4 Dose =
50kEV, Boron, B11 from BF3 gas
Dose ~1e12
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
VARIAN 350 D ION IMPLANTER (4” AND 6” WAFERS)
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
B11 IMPLANT FOR BORON THRESHOLD ADJUSTS,
STOP, P-WELL
BF2
I µA
USE THIS PEAK
50
40
B11
BF+
30
20
PLAY
B10
10
10
Rochester Institute of Technology
Microelectronic Engineering
11
19
30
48 49
ION MASS (AMU)
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
PHOTO 1 RESISTOR
Polysilicon, 3500A
30,000 Å SiO2
Coat with ~1.0µm Photoresist
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
COAT PHOTORESIST ON SSI TRACK
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Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
COAT.RCP
Page 24
Gig Ohm Resistors Fabrication Process
EXPOSE RESIST ON CANON STEPPER
i-Line Stepper  = 365 nm
NA = 0.52, s = 0.6
Resolution = 0.7  / NA = ~0.5 µm
20 x 20 mm Field Size
Depth of Focus = k2 /(NA)2
= 0.8 µm
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
DEVELOP RESIST ON SSI TRACK
Polysilicon, 3500A
30,000 Å SiO2
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Page 26
Gig Ohm Resistors Fabrication Process
ETCH POLY SILICON ON LAM 490
30,000 Å SiO2
Polysilicon, 3500A
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Use Lam 490
Recipe FACPOLY
SF6 140 sccm
O2 40 sccm
Gap 1.5 cm
Power 140 watts
325 mTorr
150 Sec/wafer
Page 27
Gig Ohm Resistors Fabrication Process
STRIP PHOTORESIST ON BRANSON ASHER
30,000 Å SiO2
Polysilicon, 3500A
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Page 28
Gig Ohm Resistors Fabrication Process
RCA CLEAN
APM
H2O – 4500ml
NH4OH–300ml
H2O2 – 900ml
75 °C, 10 min.
DI water
rinse, 5 min.
DI water
rinse, 5 min.
HPM
H2O–4500ml
HCL-300ml
H2O2 – 900ml
75 °C, 10 min.
H20 - 50
HF - 1
60 sec.
DI water
rinse, 5 min.
What does RCA
stand for?
ANSWER
SPIN/RINSE
DRY
PLAY
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Page 29
Gig Ohm Resistors Fabrication Process
OXIDE REGROWTH
500A recipe 250
30,000 Å SiO2
Polysilicon, 3500A
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Page 30
Gig Ohm Resistors Fabrication Process
LPCVD LTO
4000A LTO
Or
4000A TEOS + Densify
30,000 Å SiO2
Polysilicon, 3500A
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
PHOTO – 2 CONTACT CUTS
30,000 Å SiO2
Polysilicon, 3500A
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Page 32
Gig Ohm Resistors Fabrication Process
EXPOSE
i-Line Stepper  = 365 nm
NA = 0.52, s = 0.6
Resolution = 0.7  / NA = ~0.5 µm
20 x 20 mm Field Size
Depth of Focus = k2 /(NA)2
= 0.8 µm
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
ETCH CONTACT CUTS
30,000 Å SiO2
Polysilicon, 3500A
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
STRIP RESIST
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Branson Asher
Page 35
Gig Ohm Resistors Fabrication Process
MODIFIED RCA CLEAN
APM
H2O – 4500ml
NH4OH–300ml
H2O2 – 900ml
75 °C, 10 min.
DI water
rinse, 5 min.
DI water
rinse, 5 min.
HPM
H2O–4500ml
HCL-300ml
H2O2 – 900ml
75 °C, 10 min.
H20 - 50
HF - 1
60 sec
DI water
rinse, 5 min.
H20 - 50
HF - 1
60 sec.
DI water
rinse, 5 min.
SPIN/RINSE
DRY
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
DEPOSIT METAL
CVC 601 Sputter Tool
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Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
PHOTO - 3 - METAL
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Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
SSI COAT AND DEVELOP TRACK FOR 6” WAFERS
SSI coat and develop track
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Page 39
Gig Ohm Resistors Fabrication Process
ASML 5500/200
NA = 0.48 to 0.60 variable
s= 0.35 to 0.85 variable
With Variable Kohler, or
Variable Annular illumination
Resolution = K1 /NA
= ~ 0.35µm
for NA=0.6, s =0.85
Depth of Focus = k2 /(NA)2
Rochester Institute of Technology
= > 1.0 µm for
NA = Engineering
0.6
Microelectronic
i-Line Stepper  = 365 nm
22 x 27 mm Field Size
© March 24, 2008, Dr. Lynn Fuller
Page 40
Gig Ohm Resistors Fabrication Process
ETCH METAL
Wet Etch
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
STRIP RESIST
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Branson Asher
Page 42
Gig Ohm Resistors Fabrication Process
SINTER
Before Sinter
After Sinter
Reduce Contact
Resistance
Native Oxide
Hydrogen, neutral region
Oxygen
Silicon DiOxide
Interface
+ charge region
silicon
atom that lost
an electron
Silicon Crystal
Reduce Surface States
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
PICTURES
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
TEST
R = 1/slope = 106 Gigohms
Rhos = 106 50/1800
= 2.94 Gigohms/square
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
TEST
R=1/slope; Rhos=R / #sqs; Rho=Rhos x thickness (3500Å); Dose=implanter setting
R wafer 4 = 106 G ; Rhos = 2.94 Gohm/sq; Rho = 103K ohm-cm; Dose=1E12 cm-2
R wafer 3 = 339 G ; Rhos = 9.42 Gohm/sq; Rho = 330K ohm-cm; Dose = ?
R wafer 2 = 943 G ; Rhos = 26.2 Gohm/sq; Rho = 917K ohm-cm; Dose = ?
R wafer 1 = 1104 G; Rhos = 30.7 Gohm/sq; Rho = 1075K ohm-cm; Dose = ?
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
SAW WAFER
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
SUMMARY
A process has been created.
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
REFERENCES
1. Silicon Processing for the VLSI Era, Volume 1 – Process
Technology, 2nd, S. Wolf and R.N. Tauber, Lattice Press.
2. The Science and Engineering of Microelectronic Fabrication,
Stephen A. Campbell, Oxford University Press, 1996.
Rochester Institute of Technology
Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
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Gig Ohm Resistors Fabrication Process
HOMEWORK – GIG OHM RESISTORS
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Microelectronic Engineering
© March 24, 2008, Dr. Lynn Fuller
Page 50