Importance of Ultra High- Purity Gases for Semiconductor Fabrication
Sharad Garg
Air Quality & Emissions | Bio-fuels | Power-to-X | Green Hydrogen & Derivatives | Carbon Capture Utilization & Storage | Battery & Semiconductor Manufacturing
Ultra-high purity gases are essential throughout the semiconductor supply chain. In fact, for a typical fab, high purity gases represent the biggest material expenditure after silicon itself.
Wafer contamination caused by undetected impurities in the gas supply can cost semiconductor companies production wastage, delay in supply, production line suspension and loss in revenue. In some cases, semiconductor companies have had to scrap large quantities of wafers causing millions of dollars in lost revenue. With shortages of semiconductors damaging automotive makers and tech giants, there is increasing pressure to minimize and even eliminate such defects. Strict procedures and quality control measures are put in place to ensure that ultra-high-purity gases are delivered to the manufacturing process.
The most commonly used bulk gases in semiconductor manufacturing are nitrogen, helium, hydrogen and argon.
Nitrogen
The semiconductor industry is a major consumer of nitrogen. A modern semiconductor fabrication plant can expect to use as much as 50,000 cubic meters of nitrogen per hour for general-purpose inerting and purging gas, protecting sensitive silicon wafers from reactive oxygen and moisture in the air
Helium
Helium is a noble gas. This means, like nitrogen, helium is chemically inert – but it also has the added advantage of being highly thermally conductive, useful in semiconductor manufacturing for efficiently conducting heat away from energetic processes
Hydrogen
Hydrogen is used extensively throughout electronics manufacturing, and semiconductor production is no exception. In particular, hydrogen is used for:
*Annealing: Silicon wafers are routinely heated to high temperatures and slowly cooled in order to repair (anneal) the crystal structure.
*Epitaxy: Ultra-high purity hydrogen is used as a reducing agent in the epitaxial deposition of semiconductor materials such as silicon and germanium.
*Deposition: Hydrogen can be incorporated into thin silicon films to make their atomic structure more disordered and help increase their electrical resistivity.
*Plasma Cleaning: Hydrogen plasma is particularly effective at removing tin contamination from light sources used in UV photolithography.
Argon
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Argon is comparatively easy to ionise therefore commonly used as a primary plasma gas for etching and deposition reactions in semiconductor fabrication.
Conventionally, advances in semiconductor technology are achieved by dimensional scaling, with new generations of semiconductor technology characterized by smaller feature sizes. This produces multiple benefits: more transistors packed into a given volume, improved current flow, lower power consumption and faster switching.
However, as the critical dimensions are driven downward, semiconductor devices become more and more delicate. In a world where the positions of single atoms are important, fault tolerance thresholds are incredibly tight. Modern semiconductor processes therefore demand the highest possible purity from process gases.
Part per trillion impurity analysis of UHP gases plays a vital role in improving product quality, and Thermo Scientific API-MS systems have been used for over 30 by gas manufacturers and semiconductor companies.
?Fast online measurement (two-minute analysis cycle time) enables immediate response to gas supply upset conditions
?Superior sensitivity with ppt detection capability provides gas analysis suitable for the most stringent quality requirements
?Provides a more complete analysis of impurities, including H2, CO, CO2, H2O, O2, CH4, Kr and Xe
?APIX Quattro offers fully integrated multi-analyzer operation providing rapid contamination detection for up to four UHP gases
Analytics is the key to process optimization and specialty gases being the biggest material expenditure after silicon need a reliable and real-time monitoring. Thermofisher's APIX/APIMS δQ and APIX/APIMS Quattro? Ultra High Purity (UHP) Electronic Gas Analyzers -one solution for all the contaminants up to ppt levels and 2min analysis cycle time.