Etching and CVD cleaning in the Electronics Industry

This category represents tiers 2a and 2b of the IPCC methodology outlined in 2006 Guidelines for National Greenhouse Gas Inventories.

How to use this category

Selecting an emissions scenario

To use this category, select the industry sector and process via the sector and process drill down choices. The following choices of process are available:

• 'etching only' - specifies plasma etching of silicon containing materials (Tier 2b)

• 'cvd cleaning only' - specifies cleaning of chemical vapour deposition (CVD) tools (Tier 2b)

• 'aggregated' - specifies weighted average emissions from both etching and cleaning processes (Tier 2a)

Specifying activity data

Users can specify four parameters relating to these processes:

• the quantity of gas used

• the fraction fed into destructive emissions control technologies

• the fraction fed into capture/recovery emissions control technologies

• the fraction remaining in the shipping container (the 'heel fraction').

Calculations within this category also consider a fraction of the specified gas quantity which remains within the shipping container (the 'heel fraction'). By default, a heel fraction of 10% is assumed. In order to override this assumption users can specify a different fraction by setting the heelFraction profile item value, which should be expressed as a decimal between 0-1.

In addition, users can incorporate the effects of emissions control technologies into the greenhouse gas calculation. This is done by specifying the fraction of the total gas quantity which was used in conjunction with capture/recovery and destructive emissions control technologies. To specify destructive emissions control set the appropriate fraction using destroyedFraction profile item value. To specify capture/recovery technologies use the capturedFraction profile item value similarly (expressed as a decimal between 0-1). Discover uses emissions control efficiency factors specific to each technology and gas type (using this IPCC data) to calculate the reduction in emissions and thus the remaining quantity of emissions.

Results and calculation

The returned amounts represent the greenhouse gas emissions associated with the quantity specified. Emissions quantities are returned for both the primary gas used and an number of by-product gas where appropriate. Six quantities are returned, as follows:

• primaryGas: the absolute quantity of emissions associated with the primary gas
• byProductCF4: quantity of CF₄ emitted as a by-product (where appropriate)
• byProductC2F6: quantity of C₂F₆ emitted as a by-product (where appropriate)
• byProductC3F8: quantity of C₃F₈ emitted as a by-product (where appropriate)
• byProductCHF3: quantity of CHF₃ emitted as a by-product (where appropriate)
• CO2e: CO₂e emissions (all gases converted using the appropriate global warming potential and combined into a single quantity)

Notes

N₂O emissions from CVD cleaning

The US Environmental Protection Agency's guidelines for mandatory greenhouse gas reporting include an additional methodology for the use of nitrous oxide (N₂O) in chemical vapour deposition (CVD) cleaning. This methodology simply assumes that all N₂O used emitted during this process.

This methodology is available within this category, and can accessed by specifying 'N2O' as the gas drill choice. This choice is only available in conjunction with the 'cvd cleaning only' process drill choice. There are no emissions control options available with this gas, but users can use the heelFraction profile item value to specify the quantity of N₂O remaining within the shipping container.