Low Pressure Chemical Vapor Deposition

9/3/09 J. Tsakirgis, CNS Nanofab 1

Low Pressure Chemical Vapor Deposition

John Tsakirgis

September 3, 2009


Furnace Banks at CNS

Bank 1

Non Metal AnnealSilicon NitridePoly, AmorphousLow Temp Oxide

Bank 2

Metal AnnealWet/ Dry OxideTEOSFuture


Contamination

• My Responsibility

• User Responsibility

• The integrity of our films and tubes are directly related to what materials we put

inside.


Substrates

• Silicon wafers and samples

• Lower melting point metals

• Clean


Processes available at CNS

• Wet & Dry Oxidation ‐

Atmospheric

• TEOS Oxidation – LPCVD• Low Temp Oxidation – LPCVD

• Silicon Nitride – LPCVD• Poly, Amorphous – LPCVD

• Annealing ‐

Atmospheric


Important Applications for Deposited Films

• Gate Oxide• Gate “metal”

• Passivation• Resistive elements

– Resistors– heaters


Process Control Variables

• Pressure• Temperature

• Gas Flows• Time

• Some variables have no user access


Supporting Gas distribution Systems

Scrubber

Toxic GasMonitoring

Gas DeliveryCabinets


Pumping Stations for Furnaces

Heated Throttle Valve

pumps

ExhaustFlow


CVD-10 Wet Oxidation

• Allowed Materials

• Typical Film Thickness

100 nm to 1 micron

• Batch size

4”/6" wafer

• Oxidation Rate

6.6 nm/min

• Oxidation Gases

H2 * 02 Pyrotechnic Torch

• Typical Gas flows

1000 sccm O2

• Oxidation Pressure

Atmospheric

• Temperature

1100o

C

• Index of Refraction

1.45‐1.47

• Uniformity

< 1% thickness variation over 6" wafer


CVD-10 Dry Oxidation

• Allowed Materials

whole Si wafer?• Typical Film Thickness

100 nm to 1 micron• Batch size

4”/6" wafer• Oxidation Rate

2.4 nm/min• Oxidation Gases

Oxygen• Typical Gas flows

3000 sccm O2• Oxidation Pressure

Atmospheric• Temperature

1100oC• Index of Refraction

1.45‐1.47• Uniformity

< 1% thickness variation over 6" wafer


Dry Oxide? Nice uniform film - mostly

Whoopsy, a fingerprint!Not Good


CVD-11 TEOS


100 nm to 1 micron

• Batch size

4”/6" wafer

• Oxidation Rate

13.3 nm/min

• Oxidation Gases

TetraEthylOrthoSilicate


preset canister flow

• Oxidation Pressure

400 mtorr

• Temperature

700‐750' C


1.42 ‐

1.47

• Uniformity

< 1.5 % over 6" wafer


CVD-8 Low Pressure Oxide (LPCVD)

• Low Temp Oxide


100nm to 1 micron

• Batch size

4/6" wafers

• Deposition Rate

17nm/min

• Deposition Gases

O2 and SiH4


120 sccm / 85 sccm

• Deposition Pressure

300‐375 mtorr

• Temperature

450'C


1.44‐1.47

• Uniformity

<3 % over 6" wafer


Good and Bad Wafer


CVD-6 Silicon Nitride

Stoichiometric


100nm to 1.5 microns

• Batch size

4/6" wafers

• Deposition Rate

.5 ‐

3.5 nm/min


Ammonia / Dichlorosilane

• Typical Gas Ratio

3 NH3 :1 DCS 75:25


250mtorr

• Temperature

770'C


1.98 ‐

2.1

• Uniformity

< 1.5% over 6" wafer


Nice uniform film


CVD 6 Silicon Nitride

Low Stress


100nm to 1.5 microns

• Batch size

4/6" wafers

• Deposition Rate

9.4nm/min


Ammonia / Dichlorosilane


1 NH3 : 3 DCS 25/75


200mtoor

• Temperature

825 –

835’

C


2.0 ‐

2.3

• Uniformity

< 1.5% over 6" wafer

• Stress

< 200 MPa


CVD 7 Standard Poly

• Poly silicon


100 nm to 2 microns

• Batch size

4”/6" wafers

• Deposition Rate

10nm/min


Silane


70‐80 sccm


200‐275 mtorr

• Temperature

600‐650'C


4.0

• Uniformity

<1.5% over 6" wafer


CVD 7 Doped Polysilicon

Phosphorus / Diborane

doping

• Batch size

4/6" wafers

• Deposition Rate

13 nm/min


silane and % phos/diborane


100 sccm 30 sccm


300 mtorr

• Temperature

625' C


4

• Uniformity

<1.5% over 6" wafer


CVD 7 Amorphous

Amorphous


100nm to 2 microns

• Batch size

4/6" wafers

• Deposition Rate

8‐11nm/min


Silane


100 sccm


300 mtorr

• Temperature

< 560'C


N/A

• Uniformity

N/A


CVD- 5 & 9 Annealing Tubes

Temperatures

1100’C

Gases

O2, N2 and Forming Gas

Uniformity

<1% over 6”

wafer oxidation in Non

Metal tube

Metal and Non Metal available


CVD 7 Nanotube Growth

Tubes


100nm to 2 microns

• Batch size

4”/6" wafers

• Deposition Rate

8‐11nm/min


Silane


100 sccm


300 mtorr

• Temperature

< 560'C


N/A

• Uniformity

N/A


Initial Nanowire Growth – the start


CVD-4 Lindbergh Furnace

• Capable of Annealing• Oxidation• Forming Gas

available

• Training available immediately


Lindberg Tube with Thermocouple


Lindberg control panel


Some Projects

• Working with Professor Loncar in trying to find a solution to his poor

optical properties with Silicon Nitride

• Helping Professor Crozier with his development of Nanowire Technology.• Working to establish a TEOS/Nitride stack • Developing doping processes for poly• Working with Mughees Khan in developing low‐stress in Silicon Nitride• Annealing to activate regions after Implants• Manufacturing quartzware for sample processing• Finalize documentation for clean station, operations and training protocol• Proposal in 2 weeks to initiate open use


Cleaning Wafers is good! Here’s where to start


Film Characterization Thickness & Index of Refraction


Film Characterization Stress Measurement


Film Characterization Thickness Measurement – choices!


Film Characterization Resistivity


LPCVD – Current Status

• Assisted Use Tool

• User certification for self‐use starting soon.

• Recipe and Substrate Verification

• 25 and 50 wafer capability of 4/6”

wafers


LPCVD - Going Forward

• Being Innovative

• Don’t be Shy ‐‐‐‐‐

Initiate Dialogue ‐‐‐‐‐

Ask Questions

• Let’s make changes

• Introduce yourself

and what your trying to accomplish and

let me see if I can help.

Documents

Low Pressure Chemical Vapor Deposition