LOCOS Slideshow
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Transcript of LOCOS Slideshow
![Page 1: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/1.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 1
Simplified Example of aLOCOS Fabrication Process
Prof. A. MasonElectrical and Computer Engineering
Michigan State University
![Page 2: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/2.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 2
LOCOS Defined
• LOCOS = LOCal Oxidation of Silicon• Defines a set of fabrication technologies where
– the wafer is masked to cover all active regions– thick field oxide (FOX) is grown in all non-active regions
• Used for electrical isolation of CMOS devices
• Relatively simple to understand so often used to introduce/describe CMOS fabrication flows
• Not commonly used in modern fabrication– other techniques, such as Shallow Trench Isolation (STI)
are currently more common than LOCOS
![Page 3: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/3.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 3
LOCOS –step 1
Form N-Well regions• Grow oxide• Deposit photoresist
Layout view
Cross section view
p-type substrate
NWELL mask
NWELL mask
oxide photoresist
![Page 4: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/4.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 4
LOCOS –step 1
Form N-Well regions• Grow oxide• Deposit photoresist• Pattern photoresist
– NWELL Mask– expose only n-well
areas
Layout view
Cross section view
p-type substrate
NWELL mask
NWELL mask
oxide photoresist
![Page 5: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/5.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 5
LOCOS –step 1
Form N-Well regions• Grow oxide• Deposit photoresist• Pattern photoresist
– NWELL Mask– expose only n-well
areas
• Etch oxide• Remove photresist
Layout view
Cross section view
p-type substrate
oxide
![Page 6: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/6.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 6
LOCOS –step 1
Form N-Well regions• Grow oxide• Deposit photoresist• Pattern photoresist
– NWELL Mask– expose only n-well
areas
• Etch oxide• Remove photoresist• Diffuse n-type
dopants through oxide mask layer
Layout view
Cross section view
p-type substrate
n-well
![Page 7: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/7.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 7
LOCOS –step 2
Form Active Regions• Deposit SiN over
wafer• Deposit photoresist
over SiN layer
ACTIVE mask
ACTIVE mask
SiN photoresist
p-type substrate
n-well
![Page 8: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/8.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 8
LOCOS –step 2
ACTIVE mask
ACTIVE mask
SiN photoresist
Form Active Regions• Deposit SiN over
wafer• Deposit photoresist
over SiN layer• Pattern photoresist
– *ACTIVE MASKp-type substrate
n-well
![Page 9: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/9.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 9
LOCOS –step 2
ACTIVE mask
SiN photoresist
Form Active Regions• Deposit SiN over
wafer• Deposit photoresist
over SiN layer• Pattern photoresist
– *ACTIVE MASK
• Etch SiN in exposed areas– leaves SiN mask
which blocks oxide growth
p-type substrate
n-well
![Page 10: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/10.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 10
LOCOS –step 2
ACTIVE mask
p-type substrate
n-well
Form Active Regions• Deposit SiN over
wafer• Deposit photoresist
over SiN layer• Pattern photoresist
– *ACTIVE MASK
• Etch SiN in exposed areas– leaves SiN mask
which blocks oxide growth
• Remove photoresist• Grow Field Oxide
(FOX)– thermal oxidation
FOX
![Page 11: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/11.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 11
LOCOS –step 2
ACTIVE mask
p-type substrate
n-well
Form Active Regions• Deposit SiN over
wafer• Deposit photoresist
over SiN layer• Pattern photoresist
– *ACTIVE MASK
• Etch SiN in exposed areas– leaves SiN mask
which blocks oxide growth
• Remove photoresist• Grow Field Oxide
(FOX)– thermal oxidation
• Remove SiN
FOX
![Page 12: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/12.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 12
LOCOS –step 3
Form Gate (Poly layer)
• Grow thin Gate Oxide– over entire wafer– negligible effect on
FOX regions
gate oxide
![Page 13: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/13.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 13
LOCOS –step 3
Form Gate (Poly layer)
• Grow thin Gate Oxide– over entire wafer– negligible effect on
FOX regions
• Deposit Polysilicon• Deposit Photoresist
gate oxide
POLY mask
POLY mask
polysilicon
![Page 14: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/14.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 14
LOCOS –step 3
Form Gate (Poly layer)
• Grow thin Gate Oxide– over entire wafer– negligible effect on
FOX regions
• Deposit Polysilicon• Deposit Photoresist• Pattern Photoresist
– *POLY MASK
• Etch Poly in exposed areas
• Etch/remove Oxide– gate protected by
poly
gate oxide
POLY mask
POLY mask
![Page 15: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/15.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 15
LOCOS –step 3
Form Gate (Poly layer)
• Grow thin Gate Oxide– over entire wafer– negligible effect on
FOX regions
• Deposit Polysilicon• Deposit Photoresist• Pattern Photoresist
– *POLY MASK
• Etch Poly in exposed areas
• Etch/remove Oxide– gate protected by
poly
gate oxide
![Page 16: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/16.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 16
LOCOS –step 4
Form pmos S/D• Cover with
photoresist
PSELECT mask
PSELECT mask
![Page 17: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/17.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 17
LOCOS –step 4
Form pmos S/D• Cover with
photoresist• Pattern photoresist
– *PSELECT MASK
POLY mask
PSELECT mask
![Page 18: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/18.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 18
LOCOS –step 4
Form pmos S/D• Cover with
photoresist• Pattern photoresist
– *PSELECT MASK
• Implant p-type dopants
• Remove photoresist
p+ dopant
POLY mask
p+ dopant
![Page 19: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/19.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 19
LOCOS –step 5
Form nmos S/D• Cover with
photoresist
POLY mask
NSELECT mask
p+p+ p+
n
![Page 20: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/20.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 20
LOCOS –step 5
Form nmos S/D• Cover with
photoresist• Pattern photoresist
– *NSELECT MASK
POLY mask
NSELECT mask
p+p+ p+
n
![Page 21: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/21.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 21
LOCOS –step 5
Form nmos S/D• Cover with
photoresist• Pattern photoresist
– *NSELECT MASK
• Implant n-type dopants
• Remove photoresist
n+ dopant
POLY mask
n+ dopant
p+p+ p+
n
n+ n+ n+
![Page 22: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/22.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 22
LOCOS –step 6
Form Contacts• Deposit oxide• Deposit photoresist
CONTACT mask
p+p+ p+
n
n+ n+ n+
CONTACT mask
![Page 23: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/23.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 23
LOCOS –step 6
Form Contacts• Deposit oxide• Deposit photoresist• Pattern photoresist
– *CONTACT Mask– One mask for both
active and poly contact shown
CONTACT mask
p+p+ p+
n
n+ n+ n+
CONTACT mask
![Page 24: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/24.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 24
LOCOS –step 6
Form Contacts• Deposit oxide• Deposit photoresist• Pattern photoresist
– *CONTACT Mask– One mask for both
active and poly contact shown
• Etch oxide
p+p+ p+
n
n+ n+ n+
![Page 25: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/25.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 25
LOCOS –step 6
Form Contacts• Deposit oxide• Deposit photoresist• Pattern photoresist
– *CONTACT Mask– One mask for both
active and poly contact shown
• Etch oxide• Remove photoresist• Deposit metal1
– immediately after opening contacts so no native oxide grows in contacts
• Planerize – make top level
p+p+ p+
n
n+ n+ n+
![Page 26: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/26.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 26
LOCOS –step 7
Form Metal 1 Traces• Deposit photoresist
p+p+ p+
n
n+ n+ n+
METAL1 mask
METAL1 mask
![Page 27: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/27.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 27
LOCOS –step 7
Form Metal 1 Traces• Deposit photoresist• Pattern photoresist
– *METAL1 Maskp+p+ p+
n
n+ n+ n+
METAL1 mask
METAL1 mask
![Page 28: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/28.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 28
LOCOS –step 7
Form Metal 1 Traces• Deposit photoresist• Pattern photoresist
– *METAL1 Mask
• Etch metal
p+p+ p+
n
n+ n+ n+
metal over poly outside of cross section
![Page 29: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/29.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 29
LOCOS –step 7
Form Metal 1 Traces• Deposit photoresist• Pattern photoresist
– *METAL1 Mask
• Etch metal• Remove photoresist
p+p+ p+
n
n+ n+ n+
![Page 30: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/30.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 30
LOCOS –step 8
Form Vias to Metal1• Deposit oxide• Planerize oxide• Deposit photoresist
p+p+ p+
n
n+ n+ n+
VIA mask
VIA mask
![Page 31: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/31.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 31
LOCOS –step 8
Form Vias to Metal1• Deposit oxide• Planerize• Deposit photoresist• Pattern photoresist
– *VIA Mask
p+p+ p+
n
n+ n+ n+
VIA mask
VIA mask
![Page 32: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/32.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 32
LOCOS –step 8
Form Vias to Metal1• Deposit oxide• Planerize• Deposit photoresist• Pattern photoresist
– *VIA Mask
• Etch oxide• Remove photoresist
p+p+ p+
n
n+ n+ n+
![Page 33: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/33.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 33
LOCOS –step 8
Form Vias to Metal1• Deposit oxide• Planerize• Deposit photoresist• Pattern photoresist
– *VIA Mask
• Etch oxide• Remove photoresist• Deposit Metal2
p+p+ p+
n
n+ n+ n+
![Page 34: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/34.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 34
LOCOS –step 9
Form Metal2 Traces• Deposit photoresist
p+p+ p+
n
n+ n+ n+
METAL2 mask
METAL2 mask
![Page 35: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/35.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 35
LOCOS –step 9
Form Metal2 Traces• Deposit photoresist• Pattern photoresist
– *METAL2 Maskp+p+ p+
n
n+ n+ n+
METAL2 mask
METAL2 mask
![Page 36: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/36.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 36
LOCOS –step 9
Form Metal2 Traces• Deposit photoresist• Pattern photoresist
– *METAL2 Mask
• Etch metal
p+p+ p+
n
n+ n+ n+
![Page 37: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/37.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 37
LOCOS –step 9
Form Metal2 Traces• Deposit photoresist• Pattern photoresist
– *METAL2 Mask
• Etch metal• Remove photoresist
p+p+ p+
n
n+ n+ n+
![Page 38: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/38.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 38
LOCOS –step 10+
Form Additional Traces• Deposit oxide• Deposit photoresist• Pattern photoresist• Etch oxide• Deposit metal• Deposit photresist• Pattern photoresist• Etch metal• Repeat for each
additional metal
p+p+ p+
n
n+ n+ n+
p-type substrate
![Page 39: LOCOS Slideshow](https://reader036.fdocuments.us/reader036/viewer/2022081506/55cf949e550346f57ba33e94/html5/thumbnails/39.jpg)
LOCOS Fabrication Illustration
Prof. A. Mason Page 39
Simplifications from complete process
• skipped several substrate doping steps– channel implant to adjust threshold voltages– surface implant to increase breakdown voltage
• no LDD, lightly-doped drain• no deposition of contact interface materials• metal patterning simplified
– more complex “lift-off” process often used
• no overglass (thick top dielectric) layer• no bonding pad layer• simplified use of dark/clear field masks and
positive/negative photoresist