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Some Important Information

  • Listed below are chemicals that can be found in the SMFL. Some are available for general use and some belong to specific research projects.
  • There are chemicals in the cleanroom that do not belong to the SMFL. Permission from the owner is required before use. They will be marked with the owner's name.

(warning) If the chemical you need is not on this list, it must be signed off by the SMFL first before it comes into the facility!

  • This information is not intended to be the ultimate source for safety information, merely a starting point

Lithographic Chemicals

CD 26 Developer
Ethyl Lactate
  • Common solvent found in many photoresists. This chemical replaced cellusolve acetate as a safer solvent for photoresists.
  • Used as an edge bead remover in photoresist processing.
  • Main solvent in FujiFilm OiR620-10M Photoresist and FujiFilm HPR504 Photoresist
HPR504 Broadband Photoresist
HMDS
  • Hexamethyldisilazane
  • HMDS is an organic, flammable solvent and is used to treat substrate surfaces prior to photoresist coating (primarily positive resist).
  • When an organic photoresist with a high surface tension is coated over a hydrophilic, low surface tension surface (such as silicon dioxide), dewetting and adhesion problems can occur. Exposure of the low surface tension substrate surface with HMDS will chemically convert the surface to raise it's surface tension to match the organic photoresist.
  • Over exposure to the HMDS can also result in adhesion problems.
  • In the automatic coat/develop tracks, it is used in full strength.
  • On the manual spin coaters, a diluted version is used (MicroPrime MP-P20 ).
LOR Liftoff Photoresist

Material that is coated under photoresist to provide a undercut layer for liftoff processes

OiR 62M i-line Photoresist
P20
  • A diluted version of HMDS used for adhesion promotion when manual dispensing
  • Manufactured by Shin-Etsu MicroSi- Product name is MicroPrime MP-P20
  • Composition is 20% HMDS, 80% PGMEA

PGMEA
  • Full chemical name is Propylene Glycol Methyl Ether Acetate.
  • Common solvent found in many photoresists. Replaced cellusolve acetate as a safer solvent for photoresists.
  • Used as an edge bead remover in photoresist processing.


Polyimide
  • Polyimide is an organic compound consisting of repeating imide molecules.
  • Polyimides are used in different industries but have the characteristics of thermal stability, good chemical resistance, excellent mechanical properties. Kapton and Vespel are two examples of polyimide formulations
  • It is used in the semiconductor industry to take advantage of these properties in a variety of applications.
  • Usually formulated as a spin on material that can be set up a positive or negative acting photoresist. Very thick films can be deposited - 10's of microns.
S1800 Series Broadband Photoresist
SU8
  • An epoxy based, chemically amplified, negative acting photoresist.
  • Cured films are highly resistant to solvents, acids and bases and have excellent thermal stability
  • Well suited for permanent use applications.

Acids

Ammonium Fluoride
Fluoroboric Acid
Hydrochloric Acid
  • SMFL incoming solution is 38%.
  • Used in the RCA Clean process
  • Used for decontamination clean after Potassium Hydroxide (KOH) etches.
Hydrofluoric Acid
  • Poses a serious safety concern. See the SMFL Safety Information about Fluorine Poisoning Compounds
  • Used primarily in the etching of silicon dioxide
  • Comes in a variety of strengths.
    • Highest concentration in the SMFL is 49% - immediately dangerous - tightly controlled
  • Can be used in dilute form during the RCA Clean for removal of the chemically grown native oxide.
Nitric Acid
  • Use with caution! Very strong oxidizer, corrosive and toxic
  • Used in a variety of etchant mixtures. SMFL incoming solution is 70%
  • Reacts strongly with flammables - keep away from solvents.
Phosphoric Acid
  • Basic component of Aluminum etchants.
  • SMFL incoming solution is 85%.
  • Used for other etching & etchant mixtures. Hot phosphoric acid is used for silicon nitride etching.
Sulfuric Acid

Specialty Etches

Aluminum Etch
  • Mixture of Nitric Acid, Acetic Acid, Phosphoric Acid and water.
  • Is manufactured in formulations with and without surfactants.
Buffered Oxide Etch (BOE)
  • Caution - treat as if this chemical were Hydrofluoric Acid - Poses similar risks.
  • BOE is a mixture of Hydrofluoric Acid with Ammonium Fluoride used to etch silicon dioxide in a more controlled fashion than just hydrofluoric acid.
    • It is a mixture of 49% HF & 40% NH4F - common mixtures range from 5:1 (NH4F:HF) to 50:1.
    • May contain surfactants for wetting and etching of small features.
    • Extra fluorine acts as a buffer to preserve etch rate due to load effects or bath aging over just a HF bath.
    • As the ratio gets stronger, the ammonium fluoride comes out of solution at higher temperatures.
      • A 5:1 mixture will form crystals in the bath at temperatures below 64F
Freckle Etch
  • Freckle Etch is a specialty etchant that is used to remove residual silicon nodules left after etching aluminum-silicon films used in PVD Sputtering.
  • The silicon present in these PVD films is not soluble is wet aluminum etchants and will form nodules on the wafer surface.
Pad Etch
  • Caution - treat as if this chemical were Hydrofluoric Acid - Poses similar risks.
  • Pad Etch is an ammonium fluoride mixture used to etch oxide that has been deposited over aluminum.
  • Once through the oxide, the pad etch will not harm the underlying Al as quickly as an HF etch would.
  • Is manufactured in formulations with and without surfactants.

Bases

Potassium Hydroxide
  • Used for bulk etching of silicon. SMFL incoming solution is 45%.
  • Potassium (an alkali metal ion) will severely degrade device performance and represents a contamination threat to the lab.
  • KOH may be used only at Phosphoric & KOH Wet Bench.
  • Any substrate that has been exposed to KOH must go through an HCl decontamination process before going on to other tools in the lab.
Ammonium Hydroxide
  • Used in the RCA Clean process
  • SMFL incoming solution is 29%.
Tetramethyl Ammonium Hydroxide
  • Commonly known by its acronym TMAH
  • Warning May be fatal if swallowed, inhaled or absorbed through skin
  • TMAH is used in an alkali solution (corrosive) in the development of photoresist. It is known as a Metal-Ion Free developer as compared to other photoresist developers based on Sodium Hydroxide (NaOH). The sodium ion represents a contamination threat to integrated circuits.
  • Typical concentrations for photoresist developers are <5% solutions.
  • TMAH is also a isotropic etchant of silicon and etches preferentially along the silicon crystal planes.


Solvents / Strippers

NMP
  • Acronym for N-Methyl-2-pyrrolidone
  • Common component of many photoresist strippers such as Remover PG and PRS-2000
PRS 2000
  • References
Remover PG
  • Tools
    • Used at the Manual Processing Wetbenches

Other

Hydrogen Peroxide
  • Use with caution! Very strong oxidizer
  • Hydrogen peroxide decomposes to form water and oxygen. The decomposition rate varies with temperature, contaminants and pH (higher temp and higher pH speed up the process)
  • Hydrogen peroxide must be stored in properly vented containers.
  • Used in the making of Piranha Clean and in the RCA Clean process
Parylene

Parylene is a polymer that when heated under low pressure will deposit on surfaces.

  • It has good coating properties and is used in a variety of applications in MEMs, Bio-MEMs, & semiconductor applications
Spin on Glass

Spin on glass is a generic term that describes a variety of compounds.

  • Dielectric Applications

Dry Etch Gases

Boron Trichloride

Boron Trichloride is highly toxic.

*Boron trichloride is used in the aluminum dry etch process. It etches the native Al2O3 layer so that the chlorine can etch the aluminum.

Chloroform
  • Chloroform is used in the dry etching of aluminum. It is used in the formation of polymer sidewalls to give anisotropic etch profiles.
  • Chemical formula is CHCl3.
Chlorine

Chlorine is highly toxic, corrosive, and a strong oxidizer.

  • Chlorine is used for dry etching of aluminum.
Sulfur Hexafluoride
  • Chemical formula is SF6
  • Typically used for etching silicon and silicon nitride.
  • Much heavier than air - Mythbusters and others have done cool experiments with this "invisible water"
Tetrafluoromethane
  • Chemical formula is CF4
  • Typically used for dry etching of silicon dioxide.
Trifluoromethane
  • Chemical formula is CHF3
  • Typically used for dry etching of silicon dioxide.
Xenon Difluoride
  • Chemical formula is XeF2
  • Used for dry etching of silicon in bulk release MEMs applications
  • Very strong oxidizer.
  • Can react with water/moist air to form hydrogen fluoride.
  • Do not let XeF2 come in contact with combustibles/organic solvents.

Deposition Gases

Ammonia
  • Chemical formula is NH3
  • At room temperature, ammonia is a gas with very pungent odor.
  • Used in conjunction with Dichlorosilane to grow silicon nitride
Dichlorosilane

Dichlorosilane is highly flammable and toxic

  • Chemical formula is H2SiCl2 - or known by the acronym of DCS
  • DCS is mixed with [ |ammonia (NH3)|Listing of Chemistry#Ammonia] in LPCVD chambers to grow silicon nitride
Silane
  • Chemical formula is SiH4
  • At room temperature, silane is a gas, and is pyrophoric
  • Used as a source of silicon for the growth of polysilicon in LPCVD.
Tetraethyl Orthosilicate
  • Also known by the acronym TEOS - Chemical formula is Si(OC2H5)4
  • Used as a source of silicon for PECVD deposition of silicon dioxide.
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