Modeling Proposal: 

Working with our manufacturing team and evaluating our wafer start and technology 

profiles, we have determined that we could build a model using the following approach: 

a.	 Analyzing our fab wafer production profiles and technologies, we find that we 

have two technology corridors: aluminum and copper technologies. 

b.	 These in turn, can be broken down into several primary technology recipes. The 

recipes are representative of the overall fabricator routing used for the primary 

technology recipe. 

a.	 As a logic foundary fab, there are many subcategories of recipes, but they 

adhere tightly to the primary recipe. 

i.	 The main process steps and recipes are consistent within the given 

technology recipe. 

ii.	 Customizations tend to involve the addition of different memory 

components which have less levels/complexity and use less 

gas/cm2, so the primary technology would give a conservative 

estimate. 

iii.	 The IBM BTV fab is likely a worse case example, as it has both 

aluminum and copper technologies. 

b.	 A memory fab or a logic fab building defined products to a defined 

technology recipe will likely have only a single technology corridor and 

two or three primary technology recipes. 

c.	 Once the primary technology recipes are identified the routing can be analyzed, 

the process steps identified, and the PFC gas use for each process step and gas 

type can be calculated. It will be necessary to assign an uncertainty to the 

estimation of the gas use based on the recipe calculation. 

d.	 The gas quantities used per wafer pass by technology recipe and process step will 

be cumulated to generate a total gas consumption per wafer start per primary 

technology recipe type. 

e.	 Gas use will then have to be apportioned to the process type based on records/tool 

connections/estimates. 
 

 

 

 

 

 

The data will then be compiled into a table as follows. Each cell would have a value 

where that process step was used in the primary technology recipe. 

Process Type Gas Use by gas type for Time Period (kg) 

Technology Wafer 

Count for 

time 

period 

Remote 

Plasma 

Clean 

In-situ 

Clean 

Thermal 

Clean 

Wafer 

Clean 

Etch 

Aluminum1 

Aluminum2 

Copper1 

Actual Gas 

Use 

The following data types with specified uncertainties would need to be developed: 

 Measurement 

Variability 

Apportionment Variability 

Process 

Variability 

Apportionment 

of process type 

by tool 

Gas Use by 

Process Type: 

From Recipe 

Flowmeter: 

Recipe vs. 

Actual use. 

How variable is 

the specific 

process use 

Actual Gas Use 

by Process 

type: Cylinder 

Records 

Tolerances in 

Scale and heel 

measurements 

Where a single 

measured 

source supports 

multiple 

process types. 

Process 

Emissions 

Factors 

Number of 

samples and 

variance in 

each data set. 

Wafer Count 

Uncertainties: 

Measurement: Where the measurement device: flow meter or scale will introduce 

uncertainty into the measured result. 

Apportionment of process types to a single supply source: Where a single 

distribution system (cylinder or bulk) supplies multiple tools with multiple process 
types, the gas use will have to be apportioned to the different process types connected 

to that distribution system. 

Gas Use by Process Type within the recipe: It will be necessary to estimate the 

uncertainty/variability in the process category around the primary recipe for the 

process type. (this will be based on the variability in the recipes within the process 

type – high for etch and low for clean).