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Tweezers Cleaning

This module describes tweezers cleaning for plastic and metal tweezers. The cleaning of tweezers is important in the control of contamination throughout the lab.

Tweezers Clean Videos

There are two training videos are available for labmembers to view; one for the cleaning of metal tweezers and the other for the cleaning of plastic or Delrin tweezers.  Although the videos go over the cleaning procedure in depth, they are not a substitution for the written material.  Labmembers are expected to have read and understood the Tweezers Cleaning Procedures

before starting to clean tweezers.

Tweezers Cleaning Procedures

Purpose:

To give the new user information about the different types of tweezers used in the facility and information on how to clean them appropriately.

General Policies:

Tweezers are generally divided into two main groups; those to be used for standard nonmetal processing (Si, SiGe, Quartz or Sapphire) and those used for standard metal processing (Al, Ti or W).

Tweezers are available in the stockroom.

Most furnaces and LPCVD's have designated quartz vacuum wands for loading and unloading wafers at the station. Use of the wands at those stations is optional, but the appropriate tweezers must be used. An example of tweezers use as opposed to wand use for loading would be if the wand is broken, or wafers are polished on both sides.

The tweezers must be cleaned before using them. In most cases the storage box must be cleaned too. A description of the correct cleaning procedures follows below.

Tweezers types and categories:

Dirty Nonmetal:

These are Teflon coated stainless steel tweezers. They are for handling NONMETAL wafers (wafers that are either Si, SiGe or Quartz that do not and never have had metal on them). They may be used at any time EXCEPT for wafers that have had a prediffusion clean and are ready to be loaded into a furnace or deposition system.

Clean Nonmetal:

These are for loading wafers into the furnaces (if you cannot use the quartz wand). They must be Delrin (plastic) not metal and they must have been cleaned according to the procedure below. They may only be used to handle wafers which have been through the full prediffusion clean at wbdiff and are ready to load into one of the Tylan furnaces or LPCVD's. Exceptions are the metal side of the LTO and tylanfga where it is assumed that the wafers have metal on them.

Clean Metal:

These are used for loading wafers into tylan3 or tylanfga (if you cannot use the quartz wand, i.e. the wand is broken or you are using double polished wafers). They must be Delrin and they must be cleaned according to the procedure below. They are only to be used to handle wafers which have been through the complete cleaning procedure at wbsilicide or wbmetal and are ready to load.

Clean Metal/LTO:

These are teflon coated stainless steel tweezers and are the best choice for loading the metal side of the LTO boat. They MAY NOT be used for loading tylan3 or tylanfga (use the quartz wands or CLEAN METAL Delrin tweezers for that).

Tweezers Cleaning Procedures:

There are designated beakers for the cleaning of tweezers. Any staff member can show you where it is. All tweezers cleaning is done at wbnitride or litho solvent wetbench.  Make sure that you inspect your tweezers frequently.  With time they may start to flake and cause particles to fall onto your work.  Re-clean any tweezers you think may have been contaminated.

When cleaning plastic tweezers it might make sense to clean several pairs.  These clean tweezers may be used as back-ups for when the clean tweezers unwittingly get contaminated.

Delrin (plastic) Tweezers:

  1. Remove trace metals for 5 min in unheated 5:1:1 H2O:H2O2:HCl.
  2. Rinse for 4 min in DI water.
  3. Remove organics for 5 min in unheated 5:1:1 H2O:H2O2 :NH4OH
  4. Rinse for 4 min in DI water.
  5. Blow dry using N2 gun at the wetbench nitride.
  6. Place tweezers in a clean storage box with the tips oriented toward the end of the box marked TIPS. This will insure that contaminates from gloved hands and fingers will not transfer to the ends of the tweezers which will be in contact with the wafers.
  7. Extra pairs may be stored in a clean zip-lock bag.

Teflon Coated Stainless Steel Tweezers:

  • Carefully examine the tweezers before cleaning for slices, peeling or cracks in the Teflon coating. Replace them if you find flaws.
  • Never use metal tweezers which do not have a Teflon coatings. They are a source of contamination in the Lab.
  • Teflon coated tweezers and all tools which come in contact with wafers must be thoroughly degreased in solvents before use in the Lab.
  • Degrease by soaking in Acetone, Methanol, and Isopropyl Alcohol for 10 minutes each. Use the Nalgene beaker available in the litho area.  Staff can help you locate the beaker. Do the cleaning at the litho solvent bench.
  • Blow dry using N2 gun at the solvent bench.
  • Place tweezers in a clean storage box with the tips oriented toward the end of the box marked TIPS. This will insure that contaminates from gloved hands and fingers will not transfer to the ends of the tweezers which will be in contact with the wafers.

Tweezers Storage Box Preparation:

  • Boxes are cleaned out using Isopropyl Alcohol (squeeze bottle is ok) and given an air or blow dry. The box is then LABELED in the following way;
  • TIP is written on top of the box on one end. This marks where the working end of the tweezers will be orientated each time they are placed into the box. This prevents contaminates from handling from getting on the tips.
  • Your NAME must be written on the top of the box.
  • The TYPE of tweezers is marked on the top of the box, i.e. clean metal, dirty nonmetal, etc.

Nonstandard Material Tweezers:

  • If you are processing with nonstandard materials (that is, working mostly at the general wetbench) you MUST have designated tweezers for that work. You will need a dirty pair and a clean pair if you plan to clean substrates for deposition systems or other clean processes. You should clean these tweezers in your own glassware using the methods described above.
  • Carefully label the box and write on the handle end in black marker the name of the material they will be used for (gold, KOH, Pt, Cr, Pd, PtSi, Cu, Co, ITO, GaAs, Ni, FeCl, etc...) So that you or someone else in the Lab does not use them and unknowingly contaminate wafers and/or equipment. THIS IS VERY IMPORTANT! Failure to do this could ruin months of work by your fellow facility users and shutdown equipment.

Do not use other people's tweezers without their express permission.

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