Detection and Control of Gaseous Molecular Pollution in Semiconductor Clean Room

Source of gaseous molecular pollutant AMC

The source of AMC in clean rooms can be divided into external pollution and internal pollution. External pollution generally includes chimney emissions, automobile exhaust emissions, etc., which are usually sucked back into the clean room through the fresh air conditioning box. Its removal method is mainly set in the fresh air conditioning box for acid pollutants and alkaline pollutants can be efficient purification, limited air scrubber for organic compounds and action with acid reducing pollutants, organic compounds of chemical filters.

Internal pollution generally includes chemicals, machinery and equipment, clean room workers, clean room building materials, etc. In particular, the new plant, building structure material, paint, machine internal material, joint sealant, wafer storage box, PC gloves and other plastic materials will have a certain impact on the environment. Its removal mode is mainly through the high efficiency filter air unit (FU), mainly in the microcirculation tuyere set chemical filter.

Detection of gaseous molecular pollutants AMC in clean room

The standard of SEF21-1102 divides the air pollutants in the clean room into four types, one is acidic pollutants, including hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, etc.; The second is alkaline pollutants, mainly ammonia; The third is the coagulable pollutant, refers to the atmospheric pressure boiling point is greater than room temperature and will condense on the surface of the chemical substance, but does not include water; The fourth is doping pollutants, chemical elements that can change the electrical properties of semiconductor substances, such as boron, phosphorus, arsenic and metal ions.

More than a decade ago, the international semiconductor organization combined TRS technology to organize and define the AMC types in the clean room. After 2017, the IRDS equipment and system roadmap was understood by the industry, and AMC species were far from limited to MC, MA, MB and MD.

Gaseous Molecular Pollutants (AMC) Based on international semiconductor equipment and system circuit diagrams, the upper limit concentration of AMC in clean rooms under different process node requirements.

Airborne molecular contaminant (AMC) is a general term for gaseous contaminants that may negatively affect the yield of semiconductor processes.

The current AMC detection methods are generally limited by the low output frequency of instrument data or the small coverage of species. For example, common online chromatography-mass spectrometry usually produces a set of data every 30 minutes, and the cost of consumables and maintenance manpower is high. Another common type of online analysis is spectroscopy, such as laser absorption spectroscopy represented by cavity ring-down spectroscopy (CDS). Due to the limited laser light source, a CRDS device can generally detect only one or several compounds, and the data time resolution is minute level. This is the main reason why the RDS roadmap recommends certain combinations of devices for various classes of AMCs.

The mass spectrometer can cover several major categories of AMC, while obtaining second response and ptV level detection limits. The full spectrum recording of the accompanying high-resolution TOF time-of-flight mass spectrometry enables Vocus CL-TOF to perform data backtracking analysis, which is particularly important in the context of the ever-expanding range of AMCs to be controlled by semiconductors.

In clean room technology, pollution includes not only particles of dust in the strict sense, but also any interfering solids, liquids, gases, heat and electromagnetism, so it is necessary to carefully control the environment related to the producer, which may have a negative impact on the product production process and manufacturing quality.

Removal method

The semiconductor production process contains sophisticated MEMS and integrated circuits, which are particularly strict in the cleanliness of the production environment, so the entire manufacturing process is completed in a tightly controlled clean room environment.

Chemical filter is defined as a filter for the isolation of air molecular pollution, and its principle is achieved through physical and chemical structures. Usually the actual selection is to choose the appropriate chemical filter according to the type of pollutants, concentration and treatment air volume and other conditions. Current chemical filters selectively adsorb gases rather than mechanically "filter" impurities. Adsorption is the adsorption site of gas or liquid molecules on the surface of a solid substance, where the solid substance is the adsorbent, and the adsorbed substance is called the adsorbent. Adsorption can be divided into physical adsorption and chemical adsorption.