Characterization and control of organic airborne contamination in lithographic processing

Dallas, Andrew J.; Graham, Kristine; Clarysse, Marc; Fonderle, Vic

doi:10.1117/12.473438

Cited by 10 publications

(6 citation statements)

References 22 publications

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“…10 In all areas, except for downstream of the Donaldson Lithoguard filters, PFTAAs and fluorocarbons were the dominant organic contaminant found by approximately a factor of 10. It was shown that even after three years of operation, the chemical filters in the Donaldson Lithoguard unit still maintained >98% removal efficiency for PFTAAs and fluorocarbons.…”

Section: Resultsmentioning

confidence: 99%

“…10 In one of our previous studies, perfuorinated compounds, such as PFTAAs, were found in the cleanroom/lithography area at a concentration of 100 ng/L of air and within the upstream filter side of the stepper at a concentration of 96 ng/L of air. 10 At these elevated concentrations, these compounds can cause multiple issues such as coating surfaces, decreasing processing performance, filter blinding, and significantly reduce filter life and efficiency for other AMC. Additionally, since PFTAAs adsorb strongly in the ultraviolet, these high concentrations will significantly impact the light transmission integrity.…”

Section: Introductionmentioning

confidence: 99%

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An investigation of perfluoroalkylamine contamination control

Dallas

Zastera

2009

Metrology, Inspection, and Process Control for Microlithography XXIII

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Perfluoroalkylamine (PFAA) contamination has been observed to be a growing contamination issue in semiconductor fabs due to the increased tolerances demanded by next generation lithography processes. These contaminants are found within the cleanroom, process environments and within various tools and enclosures. As a result, effective control of PFAAs in lithographic processing and other critical environments are becoming an important filtration problem. This work was undertaken to evaluate filter performance for the removal of PFAAs and to provide an optimal filtration solution. The filter breakthrough performance of perfluorotributylamine (PFTBA), a common heat transfer fluid, is investigated over a range of environmental conditions for several commercially available adsorbent materials. The results from these accelerated tests indicate that PFAAs can be effectively removed with activated carbon-based chemical filters.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An investigation of perfluoroalkylamine contamination control

Dallas

Zastera

2009

Metrology, Inspection, and Process Control for Microlithography XXIII

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“…23 Acid treatment using CA was found to effectively deal with both basic and organic fractions of molecular contamination in lithographic environment. 24 CA was the material of choice because other acids such as phosphoric acid, hydrochloric acid and sulphuric acid are also sources of inorganic molecular contaminants themselves.…”

Section: Introductionmentioning

confidence: 99%

Citric acid-modified carbon chemical filtration for cleanroom air quality control: Study on N-methyl-2-pyrrolidone and the interference of co-existing toluene

Lee

Kuo

et al. 2015

Indoor and Built Environment

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Airborne molecular contaminants strongly affect the cleanroom air quality by severely degrading the image quality of semiconductor devices. This study aims to investigate the removal of N-methyl-2pyrrolidone (NMP), an organic alkali compound that commonly appeared in cleanroom environment and used for photoresist stripping in integrated circuit fabrication processes, through adsorption by the citric acid (CA)-modified activated carbon chemical filters. Increase in CA concentration showed positive correlation to the quantity of CA coating but had negative influences on specific surface area. Immersion of carbon particles in solutions containing 3 M CA for 3 h yielded the most chemical modification according to the intensity of carbonyl and hydroxyl functional groups attached onto the carbon surface. NMP adsorption breakthrough studies demonstrated that NMP adsorption by virgin activated carbon was ineffective. Increase in the extent of CA modification resulted in greater adsorption capacity of NMP owing to increased quantity of carbonyl functional groups on its surface. Binary-component adsorption tests involving NMP and toluene vapours revealed that the CA-modified filters had little adsorption capability for toluene as compared to virgin filters. On the other hand, NMP was competitively favourable for adsorption on CA-modified filters, even when these filters were pre-saturated with toluene. The results of this research could be of value to cleanroom or building maintenance operators for technical and environmental improvements in future system design.

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“…9,[10][11][12][16][17][18][19][20] Many of these studies have focused on the outgassing (including photo-induced outgassing) of organic contaminants from photoresists. 10,12,[16][17][18] These organic contaminants reduce system transmittance by partially absorbing the light energy at the specific radiation wavelength by being in the beam path or adsorbed to the lens surface (see inset Figure 1).…”

Section: Introductionmentioning

confidence: 99%

“…Other specific contaminants of importance, hexamethyldisiloxane (HMDSO) and trimethylsilanol, are effectively removed by activated carbon and modified activated carbon. 1,9,19 Basic and acidic contaminants are generally removed using the mechanism of chemical adsorption (chemisorption). This mechanism involves a strong interaction between the contaminant and specific active sites on the surface of the substrate.…”

Section: Introductionmentioning

confidence: 99%

New concerns with the design of filters for the protection of lithography optics

et al. 2003

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The optimal medium in which DUV resists are exposed is becoming increasingly under investigation by lithography tool manufacturers. These medium requirements have created even more design restrictions for effective filtration methods. Traditional airborne molecular contamination control in tracks and exposure tools has focused on the removal of weak bases that poison the resist. Newer concerns, including; the degradation of optics, changes in resist sensitivity, the index of refraction and the demands of tighter geometry's, all contribute to the need for quantification and control of gas-phase contamination within exposure tools. As a result, filter manufacturers are required not only to remove a broader spectrum of contaminants (e.g. organic and acid gases), but to supply removal efficiency data, under a variety of conditions including; variable challenge concentrations, mixed stream contamination, humidity (dew points), flow rates, and temperatures. The paper will address these new concerns focusing on the efficiency effects of relative humidity for various contaminant streams using a variety of filter media. In addition, the removal of hydrophilic compounds such as ammonia and sulfur dioxide when drying an air stream will also be considered. This ongoing study has contributed to the design of a point-of-use air-shower filter used to protect lithography lenses. Preliminary field tests by a major manufacturer indicate that the removal of the specified bases, acids and total organics is below detection limits of <0.1 ppb.

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Characterization and control of organic airborne contamination in lithographic processing

Cited by 10 publications

References 22 publications

An investigation of perfluoroalkylamine contamination control

An investigation of perfluoroalkylamine contamination control

Citric acid-modified carbon chemical filtration for cleanroom air quality control: Study on N-methyl-2-pyrrolidone and the interference of co-existing toluene

New concerns with the design of filters for the protection of lithography optics

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