A New Cleaning Method by Using Anhydrous HF/CH3OH Vapor System

Izumi, Atsushi; Matsuka, Takeju; Takeuchi, Tomohiko; Yamano, Akihito

doi:10.7567/ssdm.1991.a-3-4

Cited by 2 publications

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“…Vapor HF etching is a recently industrialized approach in IC manufacturing as a pre-oxidation cleaning [60] and an interesting approach in micromachining to release structures without sticking phenomena [44]. The formation of etch residues and water condensation has to be avoided by etching at elevated wafer temperature (40-45 • C) [61] or reduced etching gas pressure or by methanol as a carrier gas [62]. The etch selectivity substantially depends on the HF partial pressure.…”

Section: Sio 2 Etchantsmentioning

confidence: 99%

Silicon dioxide sacrificial layer etching in surface micromachining

Bühler

Steiner

Baltes

1997

J. Micromech. Microeng.

150

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Silicon dioxide sacrificial layer etching has become a major surface micromachining method to fabricate microsensors and microactuators often made of polycrystalline silicon. An overview of the SiO 2 materials available in integrated circuit manufacturing is given, and the SiO 2 etch mechanism and sacrificial layer etch kinetics are reviewed. Selectivity issues important for the proper choice of layers and etchants are addressed discussing the chemical attack of aluminum during long sacrificial SiO 2 layer etching, as an example. Various etchants known from other studies are compared: concentrated and dilute HF, buffered HF (BHF), nitric acid (HNO 3 ) based etchants known as P-etch, R-etch, S-etch, as well as mixtures of HF and HCl, and vapor HF. 'Pad-etch', an acetic acid/ammonium fluoride/ethyleneglycole solution is shown to have an enhanced selectivity against aluminum. Some device examples such as arrays of deflectable micromirrors demonstrate the versatile application of sacrificial oxide etching in surface micromachining.

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Section: Sio 2 Etchantsmentioning

confidence: 99%

Silicon dioxide sacrificial layer etching in surface micromachining

Bühler

Steiner

Baltes

1997

J. Micromech. Microeng.

150

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“…1, and it is the least volatile specie of the reaction 4HF ϩ SiO 2 r SiF 4 and 2H 2 O [1] An extended residence time of H 2 O, condensed on the surface, may lead to reactions with SiF 4 to form particles and nonvolatile liquids on the surface. [13][14][15] It has been shown that vapor etching SiO 2 with HF/H 2 O chemistry results in surfaces with high particle counts. 13,15 Ma et al 14 have shown that the critical step for particle reduction is the continuous desorption of SiF 4 during oxide removal.…”

mentioning

confidence: 99%

“…[13][14][15] It has been shown that vapor etching SiO 2 with HF/H 2 O chemistry results in surfaces with high particle counts. 13,15 Ma et al 14 have shown that the critical step for particle reduction is the continuous desorption of SiF 4 during oxide removal. Izumi et al 15 explain that if SiF 4 is not readily desorbed from the surface it may dissolve in H 2 O and precipitate SiO 2 particles, or SiF 4 may bond with HF to form nonvolatile liquids in the form of H 2 SiF 6 .…”

mentioning

confidence: 99%

“…13,15 Ma et al 14 have shown that the critical step for particle reduction is the continuous desorption of SiF 4 during oxide removal. Izumi et al 15 explain that if SiF 4 is not readily desorbed from the surface it may dissolve in H 2 O and precipitate SiO 2 particles, or SiF 4 may bond with HF to form nonvolatile liquids in the form of H 2 SiF 6 . An aqueous rinse is one approach for removing particles and liquids from the surface after vapor-phase cleaning.…”

mentioning

confidence: 99%

“…A drying agent, such as the aliphatic alcohols (isopropyl alcohol, methanol, or ethanol), may be employed to increase desorption rates of the etch products. 14,15,17 The aliphatic alcohols have higher vapor pressures than water and will desorb from the surface at a much faster rate than water. 17,18 The aliphatic alcohols also increase the desorption rate of water.…”

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confidence: 99%

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Surface Residue Island Nucleation in Anhydrous HF/Alcohol Vapor Processing of Si Surfaces

Carter

Hauser

Nemanich

2000

J. Electrochem. Soc.

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Anhydrous HF/methanol vapor-phase chemistries were employed to etch SiO 2 /Si surfaces at low pressure (5-50 Torr) and ambient temperature. The oxides on Si were formed from the following: (i) RCA chemical cleaning and (ii) UV-ozone treatment. Atomic force microscopy (AFM) and lateral force microscopy (LFM) were used to analyze the HF vapor-cleaned Si surfaces. AFM/LFM displayed residue islands distributed randomly upon the Si surface as a result of vapor-phase cleaning. As a result of etching RCA chemical oxides, the average lateral dimension of the residue islands is 40 nm and the average height of the islands is 6 nm. As a result of etching UV-ozone oxides, the average lateral dimension of the residue islands is 30 nm, and the average height of the islands is 3.5 nm. A decrease in residue island density is observed after the removal of a UV-ozone oxide compared to RCA chemical oxide removal. Secondary ion mass spectroscopy was used to characterize chemical impurities (O, C, F, and N) in the SiO 2 films and and the Si surface after HF vapor-phase cleaning. The constituents of the residue islands have been attributed to nitrogen impurities and silicon atoms imbedded in the passivating oxides. Results indicate that condensation of methanol vapor onto the bare Si surface, after oxide removal, is necessary for residue island formation. We suggest a model in which residue island nucleation occurs from nonvolatile N-Si complexes that form hydrogen bonds with methanol molecules and diffuse into the adsorbed alcohol layer. The molecular impurities then interact and form residue islands. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.216.129.208 Downloaded on 2015-03-22 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.216.129.208 Downloaded on 2015-03-22 to IP

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A New Cleaning Method by Using Anhydrous HF/CH3OH Vapor System

Cited by 2 publications

References 0 publications

Silicon dioxide sacrificial layer etching in surface micromachining

Silicon dioxide sacrificial layer etching in surface micromachining

Surface Residue Island Nucleation in Anhydrous HF/Alcohol Vapor Processing of Si Surfaces

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