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APV for Lanz VPO 50 HMDS wafer priming oven (HMDS oven)


Document Responsible: Pia Bomholt            

Date: 20/1 2014


1)    Purpose/Formål

The purpose of this APV instruction is to ensure that employees at iNANO are aware of the potential dangers that exist when working with the HMDS oven located inside the cleanroom facility. The aim of this APV instruction is also to prevent personal injury to maintenance personnel of the  HMDS oven. All users who work on the HMDS oven should be aware of the potential hazards listed


2)    The Instrument/Instrumentet

Hydrophilic surfaces such as silicon dioxides, silicon nitrides, glass samples, and certain metals that have surface oxides adsorb a few monolayers of water. Polymeric photoresists are very hydrophobic and adhere poorly to hydrophilic surfaces which often have surface adsorbed water. Therefore, to promote the adhesion between photoresists and samples with hydrophilic surfaces, dedicated instruments and processes are required. The HMDS oven is an vacuum instrument that allow the introduction of a vapor priming chemical and the vacuum chamber can be heated up to 200 degrees C. The instrument carries out the following process; after loading the wafers/samples into the oven, the chamber is evacuated down to 2 mtorr, and the wafers are heated up to 170 degrees C. At this temperature, adsorbed water molecules have sufficient thermal energy to be released from the surface. This process step is also referred as the “dehydration” step. Subsequently, the priming chemical HMDS vapor (bis(trimethylsilyl)amine also called hexamethyldisilazane) is introduced into the vacuum chamber. The HMDS reacts with oxygen groups on the sample surface and forms a monolayer of (CH3)3-Si-O groups. The process is completed after nitrogen purge and evacuation cycles that remove any excess HMDS from the oven. The wafers are coated with chemical groups that are covalently linked to oxide groups on surfaces and render the sample surface hydrophobic for promoting the adhesion of resists.


3)    Hazardous Conditions/Risiko

The oven can be hot and cause burns.


4)    Protective Clothing/Beskyttelsesdragt

For normal process operation standard cleanroom protective closing is sufficient. For handling HMDS reagent, the super-user is required to use facemask and protective gloves that are resistant to HMDS.


5)    Identification/Identifikation

The following chemicals can be found in the HMDS oven.


Toxic: HMDS (bis(trimethylsilyl)amine or hexamethyldisilazane)

Users are normally not exposed to HMDS. The HMDS reagent must be loaded by the super-user. HMDS is contained in a 500 mL glass container. It is labelled with the below pictograms:


Hazard statements from MSDS:

H225 Highly flammable liquid and vapor.

H302 + H332 Harmful if swallowed or if inhaled

H311 Toxic in contact with skin.

H314 Causes severe skin burns and eye damage.

H412 Harmful to aquatic life with long lasting effects.


6)    Maintenance/Vedligeholdelse


6.1) Adding HMDS

For handling the HMDS reagent, the super-user is required to use facemask and protective gloves that are resistant to HMDS.


6.2) Pump Safety

Work under exhaust and HMDS protective gloves.


7) Electrical Safety/ El sikkerhed

The instrument is powered by 3 phase 400V electrical supply. The instrument is CE marked. However, unauthorized use and repairs can compromise electrical safety and can be deadly.