Exposure to Volatile Organic Compounds and Possibility of Exposure to By-product Volatile Organic Compounds in Photolithography Processes in Semiconductor Manufacturing Factories원문보기
Objectives: The purpose of this study was to measure the concentration of volatile organic compound (VOC)s originated from the chemicals used and/or derived from the original parental chemicals in the photolithography processes of semiconductor manufacturing factories. Methods: A total of four photo...
Objectives: The purpose of this study was to measure the concentration of volatile organic compound (VOC)s originated from the chemicals used and/or derived from the original parental chemicals in the photolithography processes of semiconductor manufacturing factories. Methods: A total of four photolithography processes in 4 Fabs at three different semiconductor manufacturing factories in Korea were selected for this study. This study investigated the types of chemicals used and generated during the photolithography process of each Fab, and the concentration levels of VOCs for each Fab. Results: A variety of organic compounds such as ketone, alcohol, and acetate compounds as well as aromatic compounds were used as solvents and developing agents in the processes. Also, the generation of by-products, such as toluene and phenol, was identified through a thermal decomposition experiment performed on a photoresist. The VOC concentration levels in the processes were lower than 5% of the threshold limit value (TLV)s. However, the air contaminated with chemical substances generated during the processes was re-circulated through the ventilation system, thereby affecting the airborne VOC concentrations in the photolithography processes. Conclusion: Tens of organic compounds were being used in the photolithography processes, though the types of chemical used varied with the factory. Also, by-products, such as aromatic compounds, could be generated during photoresist patterning by exposure to light. Although the airborne VOC concentrations resulting from the processes were lower than 5% of the TLVs, employees still could be exposed directly or indirectly to various types of VOCs.
Objectives: The purpose of this study was to measure the concentration of volatile organic compound (VOC)s originated from the chemicals used and/or derived from the original parental chemicals in the photolithography processes of semiconductor manufacturing factories. Methods: A total of four photolithography processes in 4 Fabs at three different semiconductor manufacturing factories in Korea were selected for this study. This study investigated the types of chemicals used and generated during the photolithography process of each Fab, and the concentration levels of VOCs for each Fab. Results: A variety of organic compounds such as ketone, alcohol, and acetate compounds as well as aromatic compounds were used as solvents and developing agents in the processes. Also, the generation of by-products, such as toluene and phenol, was identified through a thermal decomposition experiment performed on a photoresist. The VOC concentration levels in the processes were lower than 5% of the threshold limit value (TLV)s. However, the air contaminated with chemical substances generated during the processes was re-circulated through the ventilation system, thereby affecting the airborne VOC concentrations in the photolithography processes. Conclusion: Tens of organic compounds were being used in the photolithography processes, though the types of chemical used varied with the factory. Also, by-products, such as aromatic compounds, could be generated during photoresist patterning by exposure to light. Although the airborne VOC concentrations resulting from the processes were lower than 5% of the TLVs, employees still could be exposed directly or indirectly to various types of VOCs.
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문제 정의
The authors evaluated possible exposure toby-products by the method available in the laboratory. The purpose of this experiment was to assess whether the by-products derived from photolithography processes could be included in the VOCs detected in photolithography.
However, a comprehensive study on worker exposure to the chemical substances that can be generated during the fabrication processes has not yet been reported. The purpose of this study was to measure the concentration of volatile organic compound (VOC)s originated from the chemical used and/or derived from the original parental chemicals in the photolithography processes of semiconductor manufacturing factories.
This study consists of an investigation into the possibility of worker exposure to organic compounds in photolithography processes and an evaluation of VOC concentrations in the air that resulted from these processes. The possibility of worker exposure to organic compounds was investigated through a review of the chemical substances used in the processes and an experiment to identify the by-products generated during the processes.
제안 방법
Table 4 shows the concentration of VOCs in the air from four photolithography processes in the three semiconductor manufacturing factories. Among the detected VOC components,only VOCs that had the TLVs of the ACGIH were evaluated in this study. For example, methyl-3-methoxy propionate, a component of raw materials, was detected but not evaluated.
There will be differences between the decomposition products produced by radiant energy and by thermal energy. The authors evaluated possible exposure toby-products by the method available in the laboratory. The purpose of this experiment was to assess whether the by-products derived from photolithography processes could be included in the VOCs detected in photolithography.
This study investigated decomposition products indirectly through experiments using thermal energy instead of radiant energy due to the difficulty of experimenting with UV light. Various types of aromatic compound, such as benzene,toluene, phenol, and cresol, were identified through a thermal decomposition experiment involving a photoresist which consisted of Novolak resin (cresol-formaldehyde resin), methyl-3-methoxypropionate, a phenol polymer, and a photosensitive material.
대상 데이터
A total of four photolithography processes in 4 Fabs (one process for 5 inch wafer Fab, two for 8 inch wafer Fabs, and one for 12 inch wafer Fab) at three different semiconductor manufacturing factories in Korea were selected for this study in 2009. Because the semiconductor industry has made progress with the development of fabrication techniques for larger-sized wafers, which have improved productivity, we selected those Fabsthat used these new techniques.
The thermal decomposition experiment was conducted in a fume hood facility. An Erlenmeyer flask,personal air samplers (Gilian model, LFS-113DC, SensidyneInc., Clearwater, FL, USA), and a hot plate were used for the experiment. 5 mL of the photoresist was added to a flask and the initial temperature of the hot plate was set to 150℃ in order to evaporate the organic solvent (methyl-3-methoxypropionate).
Sensitizers are compounds, such as diazonaphthoquinone, that undergo a chemical change upon exposure to radiant energy, such asUV light [8]. Several types of organic resin including Novolak resin, which is most commonly used for photoresists, were used in the process. A variety of organic solvents, such as ethyl benzene, ethyl lactate, n-butyl acetate, and propylene glycol monomethyl ether (PGME), were used as solvents of photoresists.
The tested photolithography processes used tens of chemical substances, including photoresists, which consisted of resins,organic solvents, a photo-sensitive compound, and additives. Notably, various types of organic compound, such as ketones,alcohols, acetates, ethers, amines, and aromatic compounds,were used as solvents, developing agents, and thinners in the process.
이론/모형
The concentrations of VOCs in the air caused by the photolithography processes were evaluated by a sorbent tube/thermal desorption/chromatography-mass spectrometer system (ST/TD/GC-MS). In this study, VOCs were evaluated with the threshold limit value (TLV)s of the American Conference of Governmental Industrial Hygienists (ACGIH). Tenax tubes were used as sorbent tubes to collect VOCs from the air.
The samples were analyzed by a gas chromatography-mass spectrometer (GC-MS, Agilent model 6890N-5973N,Agilent Technologies, Santa Clara, CA, USA) with reference of the International Organization for Standardization standard of 16017-1 for the sampling and analysis of VOCs [15]. Nondetectable values were substituted as “L (limit of detection)/2” for estimating the average concentration [16].
성능/효과
In conclusion, tens of chemical substances were used during the photolithography processes. Decomposition products,such as aromatic compounds, also could be generated during the patterning of photoresists by exposure to light.
후속연구
It was difficult to discern the effects of byproducts upon the airborne VOCs concentrations. Therefore, further study on byproducts is required. Also, though the Tenax tubes, which were used to collect airborne VOCs in this study, are apt to collect wide-ranging VOCs, there may have been a limitation in sample collection for very light organic compounds that were less than 5 (C5) in the carbon number.
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