Cryogenic aerosol cleaning of photomasks

Banerjee, Siddhartha; Lin, Chien-Cheng; Su, Sean; Chung, Hye-Young; Brandt, Werner V.; Tang, K.

doi:10.1117/12.617081

Cited by 5 publications

(3 citation statements)

References 3 publications

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“…[3][4][5][6][7] All alternatives for cleaning wafers, including those few utilizing nonaqueous fluids, 1,8 require some means of supplying the energy necessary to remove a particle from a siliconwafer surface, 6 in addition to chemical action of the cleaning solution. 9 Standard methods of providing mechanical energy include undercutting, 10 brush scrubbing, 7,11,12 megasonics, 3,5,13,14 cryogenic aerosols, 15,16 and fluid jets. 17 Chemical undercutting of the particulate contamination by etching connecting bridges between the particle and substrate ͑in the case of chemical bonding͒ significantly improves particle-removal efficiencies ͑PREs͒ compared to simple rinsing.…”

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confidence: 99%

Silicon-Wafer Cleaning with Aqueous Surfactant-Stabilized Gas/Solids Suspensions

Андреев

Freer

Larios

et al. 2011

J. Electrochem. Soc.

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As feature sizes in the microelectronics industry diminish, cleanliness becomes an ever more important requirement. In response to these challenges, a novel wet-cleaning technology was developed at Lam Research Corporation to remove strongly adhered contaminants. An alkaline, foamed aqueous dispersion of insoluble platelet solids flows in linear shear past a particle-contaminated surface. Contaminant removal increases with solids concentration, foam quality, process time, and shear rate and can approach 100%. Particle-removal experiments indicate that dispersed solids are necessary for contaminant removal. Exponential decline of adhered particles with number of immersion/withdrawal events and a linear increase in the rate of particle removal with solids concentration indicate that the removal mechanism is binary collision between the insoluble fatty-acid platelets and Si 3 N 4 contaminant particles. Foam or surfactant solution alone is not effective in particle removal. A binary-collision rate model is derived to relate particle detachment to contact time. The binary-collision rate law agrees well with experimental removal data and provides a powerful design tool to assess the role of cleaning parameters, including process time, shear rate, dispensing flow rate, system geometry, solids concentration, and foam quality.Conventional metal-oxide-semiconductor manufacture of microelectronic devices can require over 100 process steps entailing deposition, removal, and alteration of material. For each step, processing, handling, and transport of the silicon wafers generates or transfers particulate contamination that can adversely affect device performance. The impact of particulate contamination can be drastic, significantly diminishing device yield; the trend toward smaller etch features exacerbates the problem as a single Ͻ100-nm contaminant particle can render a chip inoperative. In addition to efficient contaminant removal, cleaning processes must not damage features on the wafer and must not lose native material from the surface ͑film loss͒. Accordingly, an entire subindustry, primarily focused on wet cleaning, has emerged to remove particulate contamination. 1,2 Contaminant removal relies on the relative magnitudes of adhesion and detachment forces. Hence, successful detachment depends not only on particle-substrate chemistry but also on contaminant morphology and size. 3-7 All alternatives for cleaning wafers, including those few utilizing nonaqueous fluids, 1,8 require some means of supplying the energy necessary to remove a particle from a siliconwafer surface, 6 in addition to chemical action of the cleaning solution. 9 Standard methods of providing mechanical energy include undercutting, 10 brush scrubbing, 7,11,12 megasonics, 3,5,13,14 cryogenic aerosols, 15,16 and fluid jets. 17 Chemical undercutting of the particulate contamination by etching connecting bridges between the particle and substrate ͑in the case of chemical bonding͒ significantly improves particle-removal efficiencies ͑PREs͒ compared to simpl...

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confidence: 99%

Silicon-Wafer Cleaning with Aqueous Surfactant-Stabilized Gas/Solids Suspensions

Андреев

Freer

Larios

et al. 2011

J. Electrochem. Soc.

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“…A successful cleaning procedure must effectively remove particulate contamination from a wafer surface but not damage existing structures. Many successful cleaning procedures have been developed, including undercutting, brush scrubbing, − megasonics, − cryogenic aerosols, , and fluid jets . However, these procedures can induce damage for small feature sizes.…”

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confidence: 99%

Meniscus-Shear Particle Detachment in Foam-Based Cleaning of Silicon Wafers with an Immersion/Withdrawal Cell

Андреев

Prausnitz

Radke

2010

Ind. Eng. Chem. Res.

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New experimental data collected at Lam Research Corporation and theoretical analyses are presented for aqueous-foam cleaning of silicon wafers contaminated with strongly adhered 90 nm Si 3 N 4 particles . We analyze the distribution of contaminant removal along the wafer surface and the influence of foam quality in a vertical rectangular slot upon wafer immersion/withdrawal. At zero foam quality, particle removal along the wafer surface is uniform. Increased foam quality leads to improved overall removal. Removal, however, is no longer uniform with larger detachment rates toward the bottom of the wafer. To explain the observed nonuniform particle removal, we adopt a binary-collision model that demands a linear dependence of removal rate on the surface shear rate. Perturbation analysis provides the distribution of the wall shear rate along the wafer surface in an unfoamed solution. Calculations show that the wall shear rate on the wafer surface is strongly peaked in the meniscus just above the liquid-filled slot. Thus, with no foam present, removal in the meniscus zone dominates the overall removal process. Because the time of exposure to this high shear is the same for all parts of the surface, we obtain uniform cleaning. With foam bubbles present, the wall shear rate in the slot is enhanced, leading to significant removal in the bulk of the slot. Because the residence time of a wafer in the bulk cleaning solution varies for different parts of the wafer, contaminant removal in the bulk of the slot depends on the vertical position. Combined particle removal in the meniscus zone and in the slot leads to the observed nonuniform distribution of contaminant particles remaining on the wafer surface. Increasing foam quality increases the slot wall shear rate and, hence, the removal rate inside the immersion/ withdrawal cell.

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“…Specifically, any etch-based process will not be tolerated, as substrate layers are too thin and roughness limits are too strict to accept the consequences of etching. At the same time, the critical particle size will drop, and fluidmechanical based cleans will be increasingly ineffective at imparting the required removal force on the particles due to boundary layer effects [1][2][3][4][5][6][7][8] As particle size is scaled down from the micron to the nanometer scale, a number of challenges arise which limit experimental and theoretical descriptions of the adhesion. One of these challenges involves immobilizing a nano-scale particle onto the AFM cantilever for adhesion force measurement.…”

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confidence: 99%