Pei & Worth

1NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing

Global Warming Science:Status and Statistics

Phyllis Pei

Walter Worth

Sematech

1999 Arizona Board of Regents for The University of Arizona

Pei & Worth

2NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing

Perfluorocompounds (NF3, SF6, C2F6, CF4, CHF3)

• Have long atmospheric lifetimes

• Stable, non-toxic

• Strong infrared absorbers

• Continuing emissions will likely accumulate with unknown consequences

• Some, such as C2F6, are made solely for use in semiconductor manufacturing

• Most PFC gas is not “consumed” in the etch and CVD processes

Pei & Worth

3NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing

Key Greenhouse GasesAffected by Human Activity

GAS UNITPre-Industrial(1750-1800)

Present(1990)

AtmosphericLifetime (Yrs)

CO2 ppmv 280 353 50-200

CH4 ppmv 0.8 1.72 10

N2O ppbv 288 310 150

CFC-11 pptv 0 280 65

CFC-12 pptv 0 484 130

PFCs pptv 0 100 700-50,000

ATMOSPHERIC CONCENTRATION

NOTE: H2O has largest greenhouse effect, but is not affected by human sources and sinks

Pei & Worth

4NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing

PFC Lifetimes and GWPs

GAS ATMOSPHERICLIFETIME (years)

GWP

CF4

50,000 6,300

C2F

610,000 12,500

SF6

3,200 24,900

CHF3

250 12,100

NF3

~740 8,000

CO2 (reference) 50-200 1

GWP = Global Warming Potential @ 100 year time horizonSource: IPCC

Pei & Worth

5NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing

Global Warming Potential (GWP)

The following equation is used to calculate GWP:

GWPt=

t

0

a i c i dt

a c dtco2 co2

t

0where:

a1 = the instantaneous radiative forcing resulting from a unit increase in the atmospheric concentration of trace gas, i

c1 = concentration of trace gas, i, remaining in the atmosphere at time, t, after release of unit mass at t=0

t = number of years over which the calculation is performed

Pei & Worth

6NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing

Million Metric Tons Of Carbon Equivalents (MMTCE)

MMTCE = 12 x Kg x GWP100

44 109

GWP100 = global warming potential at 100 yr. time horizon

Kg = weight of PFC emitted

Pei & Worth

7NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing

Global Warming Calculations

Wavelength & Molecular Size & Lifetime

[ Rad. Forcing & Conc. & Time ]

{ [GWPt] & Mass }

{ Million Metric Tons Carbon Equivalent }

Pei & Worth

8NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing

U.S. Greenhouse Gas Emissions

Each source, although small,

contributes to thewhole

Pei & Worth

9NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing

PFC Emissions/Use Chart

Global PFCEmissions from

AluminumIndustry

U.S. PFCEmissions from

AluminumIndustry

U.S.SemiconductorIndustry Use of

PFCs

33,000

7,500 3000

5,00010,00015,00020,00025,00030,00035,00040,00045,000

Global PFCEmissions from

AluminumIndustry

U.S. PFCEmissions from

AluminumIndustry

U.S.SemiconductorIndustry Use of

PFCs

Data Source: EPA & DataquestTons/year

Pei & Worth

10NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing

1993 PFC Purchases

(U.S. Semiconductor Industry)

CF4 C2F6 NF3 SF6 Total

Estimated U.S. Total 67 177 18 45 307

% of Total 22 58 6 14 100

1993 Purchases of PFCs (metric tons)

Pei & Worth

11NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing

Chronology - PFC Technology Development

1994 - Tested first commercial PFC thermaldestruction device (Delatech’s CDO)

- Alzeta develops and installs first inwardly-fired burner at SEMATECH

- MIT starts screening PFC alternative chemicals

1995 - Alzeta licenses burner technology to Edwards

- IBM demonstrates 50% C2F6 reduction by process optimization

Pei & Worth

12NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing

Chronology - PFC Technology Development (Cont’d)

- Edwards develops and SEMATECH tests prototype burnbox

- MIT successfully destroys destruction of PFCs in microwave reactor

- Novellus and 3M develop C3F8 as C2F6 replacement

1996 - Beta testing of PFC capture technologies• Air Products/Radian at TI• Air Liquide at TI• BOC at IMEC

Pei & Worth

13NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing

Chronology - PFC TechnologyDevelopment (Cont’d)

- Schumacher unveils potential PFC alternative (TFAA)

- C3F8 is being evaluated in fabs at TI and AMD as drop-in replacement for C2F6

- Edwards improves burnbox to destroy CF4, tested at Motorola

- DuPont announces PFC replacement studies