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Wet Bench Flexcorr-3 and -4, wbflexcorr-3 and -4

This wet bench is used for wet chemical (corrosives) processing of standard and non-standard (flexible) materials like glass, wafer pieces, devices with gold or non-standard metals. It is also used for non-CMOS compatible processing, such as KOH etching. With the appropriate, dedicated glassware, KOH cleanup can be done to decontaminate wafers for later CMOS-compatible processing. Features: * Hot plate for heating solutions in beakers * Constant temperature bath * HF tank * Separate drain for HF waste disposal

Picture and Location


wbflexcorr-3 and -4
The tool is located at B4 on the Lab Map.

Process Capabilities

Cleanliness Standard

The wbflexcorr-3 and -4 appears in all three equipment groups (clean, semiclean, and gold). Processing may require dedicated labware.

Since wafer processing is done manually in glassware (or more appropriately, "labware") the Equipment Group (clean, semiclean, or gold) is really determined by the cleanliness of the labware.
Labware at this station is considered gold contaminated. In order for wafers processed at this bench to be allowed into clean or semiclean equipment, the labware used must be fused silica or "quartz" (which does not contain sodium normally found in normal lab glassware.)
For clean equipment, the labware must never have been in contact with solutions or materials containing alkali (Na, K, Li) or any metals.
For semiclean equipment, labware must never come into contact with alkali nor any non-standard metals (standard metals are acceptable.) Labmembers must obtain their own clean or semiclean labware, and must label and store it to prevent possible contamination through general use.



Substrates may be of most any type, size, shape and any material up to 6 inch.
GaAs is not allowed for processing here (GaAs processing is only allowed at the wbflexcorr-1 and-2).


Materials control policies are governed by equipment groups; for the description of this policy, click <here>.
This wet bench is for standard and non-standard materials, like glass wafers, wafer pieces or substrates, gold or other non-standard films.

Performance of the Tool

What the Tool CAN do

Wet Bench wbflexcorr-3 and-4 is for wet chemical (corrosives) processing of standard and non-standard materials (flexible) like glass with gold or non-standard metals for pieces and wafers up to 6 inch.

SNF standard etchants are allowed at this bench, for standard processing only. Consult staff if your work requires non-standard processing conditions (such as elevated temperatures, unusually extended process times, or mixing of chemicals), even if standard SNF etchants and chemicals are to be used. 

Processing includes wafer cleaning using piranha or SC1/SC2, KOH or TMAH etching of silicon, oxide etching using HF, metal etching such as aluminum, gold, or chrome and etching of non-standard substrates such as glass. With appropriate, dedicated quartzware, KOH cleanup can be done to decontaminate wafer for later processing in CMOS-compatible equipment.
All processing is done manually in station-dedicated or labuser-provided labware (beakers, dishes, etc.), there are no automated wafer processing modules.
The station contains one hot plate, a constant temperature circulating bath for heating solutions in beakers, a sink for rinsing, and HF tank, HF drain, and an aspirator for disposal of corrosive waste.

What the Tool CANNOT do

GaAs is not allowed for processing here (GaAs processing is only allowed at the wbflexcorr-1 and-2).


Solvents are not allowed at this bench (solvent processing must be done at one of the solvent benches).


How to Become a User


  1. Read all material on the SNF website concerning the wet bench general, including Background, Process Capabilities, Operating Procedures and Process Monitoring.
  2. View the Delrin Tweezer Cleaning (9 minutes, 37 Mbytes).
  3. Print the SNF Shadowing Form and the wet bench general checklist on clean room paper and contact a qualified user of the wet bench to arrange to ‘shadow’ them while they use the tool. You are responsible to be with that labmember for the full time they are operating the tool, and it would be intelligent to ask questions and try to become as familiar as possible with the wet bench during this ‘shadowing.’  You may have to shadow the qualified user more than one time. The qualified user and you will have to sign the SNF Shadowing Form.
  4. Contact SNF training contact on the Equipment Summary page. There is a written test for the tool.

Operating Procedures



This is a WAFAB brand wet bench. This station contains from the left to the right:

One DI water rinse sink which drains into the plenum and than into the acid waste neutralization system (AWN).

wbflexcorr-1 sink


One covered HF disposal module which drains into the HF waste collection system.

Wbflexcorr-1 and -2, HF drain



One HF tank to etch pieces up to one 6 inch cassette which drains into the HF waste collection system.

HF tank

One hot plate and one constant temperature bath (CTB) used for heating acids or bases in glass or quartz beakers.

hot platre and ctb


The wet bench also contains two N2 guns and two DI water hand sprayer.

N2 gun DI water gun

Each of these modules has its own micro-controller unit, mounted in the overhead control panel.

The aspirator,  rinse sink, and the wet bench plenum (over which all the modules sit and collects runoff from the benchtop) drain into the acid waste neutralization system.


Because many commonly used etch processes are quite long yet may not require the operator to be present at all times (for example, KOH etching all the way through silicon), the wbflexcorr-3 and -4 is set up to allow two users at once and, thus, has two names: wbflexcorr-3 and wbflexcorr-4.


Safety - Chemical Hazards

Any of the SNF-standard, non-solvent etchants may be used this bench. Any non-SNF-approved etchants must undergo safety and contamination review by the Prom Committee. Because this is a shared bench, you must read the Material Safety Data Sheets and be aware of the hazards, not only of the chemicals you are using, but also for chemicals that are commonly used. Because mixing and pouring of chemicals into open containers are performed at this wet bench, users must be keenly aware of the potential handling hazards of these chemicals. Be aware that this bench is an entirely manual station, without safety features of other wet benches to prevent chemical mixing, spills, or other potential problems. Above all, users must understand and practice safe chemical handling procedures for working at this station.

The primary hazard classifications for some of the chemical mixtures which may be used at this bench are:

Aluminum Etch Al 80:3:15 NP, 60 to 80% Phosphoric Acid, 5 to 15% Acetic Acid, 1 to 5% Nitric Acid, water, and CMOS grade Surfactant <1% - Primary Oxidizer, corrosive, air/water reactive

Chrome Cr Etch 1020AC (Transene): 20 % Ceric Ammonium Nitrate, 10 % Acetic Acid, and Water 70 % -Primary Oxidizer, corrosive

Gold Au Etch TFA (Transene): Potassium Iodide (KI) 42 %, Iodine (I2) 10 %, Water 48 % - Toxic

70% - 90% sulfuric acid (H2SO4)/hydrogen peroxide(H2O2) (piranha) - Corrosive, oxidizer, air/water reactive
50:1 HF = 2% Hydrofluoric Acid - Corrosive, toxic

49% HF Hydrofluoric Acid - Corrosive, toxic

20:1 BOE, 38% Ammonium fluoride (NH4F), Hydrofluoric acid 2.5%, 60% water - Corrosive, toxic

6:1 BOE, 34% Ammonium fluoride (NH4F), Hydrofluoric acid 7%, 59% water- Corrosive, toxic

SRS-100 (replaces PRS3000) N-Methyl-2 pyrrolidone (NMP) ~60%, Tetramethylene sulfone ~30%, Isopropanolamine ~10% - Flammable, mildly corrosive

PRS-1000, 2-(2-Ethoxy-ethoxy)ethanol (10-30%), sulfolone (25-45%), 1-Methyl-2-Pyrrolidinone (35-55%), Tetraethylene Glycol (1-10%), monomethanolamine (<0.1%) - Flammable, mildly corrosive

85% H3PO4, Phosphoric Acid - Corrosive, oxidizer, air/water reactive

45% KOH, Pottasium Hydroxide - Corrosive

25% TMAH, Tetra Methyl Ammonium Hydroxide- Corrosive


5:1:1 H2O:H2O2:NH4OH - Oxidizer, corrosive

5:1:1 H2O:H2O2:HCl - Oxidizer, corrosive

For more information about primary hazard classifications, consult the SNF Safety Manuals one and two.

Remember: because of fire/explosion risk, flammables should not be mixed with corrosives or oxidizers.

HF-based chemicals may cause serious, delayed tissue damage upon skin contact. The mechanism of action is the depletion of calcium from muscle and bone by free fluoride, which can readily pass through skin. If skin contact with HF-based chemicals is suspected, rinse the affected area thoroughly, and then immediately apply calcium gluconate gel to the affected area, following the SNF guidelines for first aid for HF exposure in the SNF Lab Manual Part II. HF-kits containing tubes of gel (along with instructions for use) are located in plastic bags at each wet station.

Safety - Equipment Hazards

Input power is 208 volts AC, three phase at 30 amps. Only qualified personnel are allowed to work on the electrical parts of this system. If any electrical problems are seen with this system, press the EMERGENCY POWER OFF button, shut the system down, and contact Maintenance staff.

Safety - Process Hazards

General process hazards involve handling of chemicals and materials which come into contact with chemical used at this station. Wet benches are potentially the most dangerous operations in the lab, this particular one more so than the other because processing is completely manual. Be sure you understand all hazards and proper handling procedures before working at this or any other wet bench.

Safety - Interlocks

The wbflexcorr-3 and -4 bench has NO safety interlocks to protect personnel from chemical and process hazards described above.

Safety - Alarms

The sink, aspirator, and plenum drain into the general lab acid waste neutralization (AWN) system. These modules may be used only when the AWN is functioning. When there is a problem with the AWN, the yellow light (above wbflexcorr-1 and-2 or wbnonmetal) will flash and no processing at any of the acid/base wet benches is allowed.


Preparation - Gloves

When working with chemicals, which includes transferring chemicals from the storage area to the wet bench and back, pouring chemicals, or transferring cassettes in and out of chemical baths, cleaning the baths or bench, it is mandatory to wear gloves in following order:
1. Latex gloves, not chemical resistant (if you have allergies to Latex wear thin Nitril gloves instead)

2. Yellow chemically-resistant Nitril gloves, for chemical protection (check for holes)

3. Yinyl gloves, to protect the wet bench from potential contamination (important while working with clean labware, remember vinyl gloves are not chemical resistant)

After handling chemicals, vinyl gloves must be changed before handling cassettes.

For general use when not working directly with chemicals, vinyl gloves can be worn directly over latex gloves. The station-dedicated cassettes, handles, the inside of the wafer boxes and their lids, are all to be kept free of contamination. A glove touching anything else is considered contaminated. Remember, the benchtop and the control panels are considered contaminated.
Change gloves frequently and especially whenever any contamination might be suspected.

Preparation - Personal Protective Equipment (PPE): face shield, chemicals apron, gloves

When working with chemicals, which includes transferring chemicals from the storage area to the wet bench and back, pouring chemicals, or transferring cassettes in and out of chemical baths, cleaning the baths or bench, it is mandatory to wear Personal Protective Equipment (PPE) in following order:

1. chemicals apron

2. face shield (over safety glasses)

3. yellow chemically-resistant Nitril gloves (check for holes)


Find more detailed information about safety, PPE, and chemical handling procedures in the SNF Laboratory Manual Part II:


Cassettes and other Labware

Gold contaminated labware and cassettes at wbflexcorr-3 and -4l do not have any markings; some have been cut in half for ease of use in beakers.

Cassettes and handles with one red button are used for etching "clean" silicon wafers in KOH. The labware is labeled: clean KOH only.

Cassettes and handles with two red buttons  are used for etching "clean" silicon wafers in TMAH. The labware is labeled: clean TMAH only.

Any cassettes with different buttons or circular cutouts belong to other wet bench stations and so must not be used at wbflexcorr-3 and -4 because they will become contaminated. (Another note: please handle Teflon cassettes with care -- they cost about $500 each to replace.)

Most labware found at wbflexcorr-3 and -4 is considered gold-contaminated; any substrates processed in this labware is considered gold-contaminated thereafter. You may use your own personally labeled, dedicated labware to prevent contamination of substrates. In order to be "clean" compatible, the labware must never have been in contact with solutions or materials containing alkali (Na, K, Li) or any metals. To be "semiclean", labware must never come into contact with alkali nor any non-standard metals (standard metals are acceptable.) Personal labware must be stored in personal storage space or will be considered contaminated. Dedicated "clean" (uncontaminated) labware must be made of either fused silica ("quartz") or electronics-grade Teflon. Standard Pyrex-brand glassware, which contains up to 5% sodium, is unacceptable as "clean" labware.

Labware must be compatible with the etchant to be used. Pyrex glass or quartz is not acceptable for HF or BOE etchants, although it is acceptable for sulfuric/peroxide ("piranha") cleans. Teflon is acceptable for any of the commonly used etchants, although should not be heated (heat is transferred poorly and Teflon will absorb etchant). Polypropylene is not acceptable for piranha (as it melts) although is acceptable for room-temperature HF or BOE etchants. In summary:


Labware material






Will etch




Will etch





Chemically OK
Can't heat


Chemically OK
but may melt


Chemically OK
but may melt

For other etchants and material combinations, you may wish to consult SNF staff.

Equipment Setup 

The Control Panel

The control panel modules are:

HF tank:  Drain on/off

Power This controls power to the control panel. It contains the Emergency Off button (top) and the main power On/Off switch. The main power is left on.

Hood Light. Manual on/off switch.

Aspirator The green "Aspirator" Start button turns on the aspirator system, allowing the user to drain acids or bases. After two minutes, the aspirator will turn itself off or press the red Stop button.

Hot Plate Controller. This controls the heating element on the hot plate.

Constant Temperature Bath. This controls heating of the constant temperature bath.


Make a reservation.

If you would like to use the controlled temperature bath, reserve time for the wbflexcorr-4.

If you are going to use the hot plate or HF tank, make a reservation for the wbflexcorr-3.

For processing at room temperature, reserve the wbflexcorr-3. If this module is not available anymore, reserve time for the wbflexcorr-4. You loose your reservation if you are 15 minutes late.


  • Check the exhaust gauge (magnehelic) for sufficient exhaust, it should read > 0.5 and < 1.5
    (insert picture)
    (located in upper control panel) 

  • Check that the acid waste neutralization system is functioning. When there is a problem with this system, the yellow warning light (there is one over wbflexcorr-1/-2 or wbnonmetal) will flash. If this happens, none of the wet benches may be used, as the waste will not be properly treated.


    AWN alarm

  • Check the bench for any damage or any other obvious problems. Report it on Badger and notify Maintenance if any problems are observed.

  • The benchtop should be clean and dry before you work on it. Thoroughly rinse off any drips (assume they are acid) with the DI hand sprayer, gently dry with the N2 gun and, if necessary, remove residual water with cleanroom wipes. Avoid using cleanroom wipes to clean up unknown drips; these are then considered hazardous waste and must then be handled and disposed of accordingly. Do not leave cleanroom wipes on the bench top.

  • Enable wbflexcorr-3 or wbflexcorr-4. If your process requires the complete bench top or if you do not otherwise want to share the space with other users, make sure to reserve both modules for the time period you require. Even if you do not use the hot plate or the controlled temperature bath, you must enable either wbflexcorr-3 or wbflexcorr-4 for a room temperature process.
    Not more than two users are allowed to use this bench at the same time.

  • Main power should be left on (Main and Sys green lights are on).
    Power controller

  • Light should be left on.


Labeling Containers with Blue "In-use Hazardous Chemical" Tags:


  • Every beaker or open container containing any chemical or water must have a "In-use Hazardous Chemical" tag with it. The purpose of the tag is to identify the contents of the container as well as the labmember who is using the chemical. Fill the tag out before you pour chemicals in a beaker.

  • Compositions of the solutions (including water) must be listed on the tag.

  • Use complete chemical names on the tag (no chemical formulas, no abbreviations, and no jargon such as "piranha").

  • Extra tags are available in the gowning room. 

Transferring Acids or Bases


  • No solvents may be used at this bench (use wbsolvent for processes with solvents.) Only acids and bases or other standard SNF, non-solvent etchants may be used at this bench.
  • In obtaining chemicals, use proper protection (safety glasses, face shield, yellow chemical resistant Nitril gloves, chemicals apron) to transfer chemicals from the storage area to the wet bench. Always double check the labels to ensure you have the correct chemicals!
  • Always use transfer carts (plastic) to transport chemicals; chemicals must never be hand-carried in the lab. Follow the instructions for transporting chemicals, which are posted on the chemicals passthrough door.

    Pouring Acids or Bases

    The benchtop should be clean and dry before you work on it. Thoroughly rinse off any drips (assume they are chemicals) with the DI hand sprayer, gently dry with the N2 gun and, if necessary, remove residual water with cleanroom wipes. Avoid using cleanroom wipes to clean up unknown drips; these are then considered hazardous waste and must then be handled and disposed of accordingly. Do not leave cleanroom wipes on the bench top.
  • Before pouring chemicals, plan how you will dispose of used chemicals, especially if you are etching metals. Organize the work bench accordingly.
  • Make sure to label chemicals in beakers, even water, with the "In-use Hazardous Materials" card.
  • Prepare a beaker of water for rinsing your substrates.
  • Now, to pour the chemical. Place the chemical bottle far enough under the hood to prevent fumes from escaping into the lab. Remove the bottle cap and place it topside down on the benchtop, to prevent contamination. Avoid contamination of the bottle: do not touch the inside of the bottle cap or the mouth of the bottle with your gloves. If the cap is inadvertently contaminated, rinse thoroughly before replacing it on the bottle.
  • Using one hand around the neck and the other around the base of the bottle, gently pour the chemical into the beaker or other container. Pour slowly, to avoid any splashing.

    Chemical Handling 

    • Keep all open containers at least 6 inches from the front of the hood to ensure proper exhaust. The red tape line indicates 6 inches.
    • Chemicals must remain at this bench. Open containers with chemicals may not be transferred to or from this bench.
    • If you wish to re-use the chemical later, obtain a clean, chemically compatible container with the screw cap lid. Transfer your chemical to that container, using a funnel. Obtain and fill out a permanent yellow personal chemical identifier label for this container. (See the safety section of the website.)

    How to mix piranha:

    For sulfuric/peroxide "piranha" clean, choose a container (glass or quartz) that is roughly twice the volume of what you plan to pour (boiling piranha tends to "spit".) First pour the concentrated sulfuric acid, then slowly add hydrogen peroxide. Because sulfuric is heavy and viscous while peroxide is thin, they do not always mix well. Mix them by taking an empty cassette or appropriate handle and gently place it in the acid and bring it out several times (don't stir!).

      • After pouring the chemical, replace the cap on the bottle. If any chemical drips onto the outside of the bottle, thoroughly rinse and dry the bottle before returning to the transfer cart. Return unused chemicals or empty bottles to the pass-through as soon as you are done pouring; never leave chemicals at the wet bench or on the transfer cart. Make sure the chemicals are returned to the appropriate labeled shelf (double-check!)


        Heating Chemicals using the hot plate

        (insert picture)

        If you are using the hot plate, enable wbflexcorr-3.
        DO NOT turn the heater on yet.
        Place your glass or quartz beaker on the hot plate, making sure it is filled with your chemical. Do not use beakers made of materials other than glass or quartz which may melt. Do not heat an empty beaker. Do not walk away from the station when heating. Place a thermometer in the solution (make sure it is compatible with your chemical). Don't forget to fill out a blue card and place it next to the hotplate.
        Press green Hot Plate Start button (times out after 2 hours).
        Start with the heater setting at "2 1/2" (never more than 6); this will heat up approximately to 40 C, depending on the chemical mixture, volume, and beaker size. If higher temperature is needed, ramp the temperature setting up SLOWLY.
        After the etch or clean:
        Turn heater knob back to 0.
        Aspirate chemicals.
        Press red Hot plate Sop button.
        Disable wbflexcorr-3.

        Following chemicals and temperatures are allowed, other chemicals or temperatures need staff approval:
        40 C for Aluminum etchant
        80 to 100 C for KOH
        80 C for TMAH
        50 C for the 5:1:1 H2O:H2O2:NH4OH
        50 C for the 5:1:1 H2O:H2O2:HCl
        90 to 120 C for 4:1 or 9:1 sulfuric acid:hydrogen peroxide
        60 C for SRS-100
        40 C for PRS-1000

    Etching Substrates:

      • Prepare your substrates for etching. Various holders for wafers and wafer pieces may be found at the this station. Ensure that whatever you choose to use is compatible with the etchant and that there is no risk of substrates or holders of slipping or being dropped.
      • Set your own timer or stopwatch (timers are not available at this bench).
      • Etch your substrates for the appropriate time.
      • Remove the substrates and place in a rinse beaker.
      • With the rinse beaker in the rinse sink, turn on the gooseneck and allow rinse water to overflow in the rinse beaker for at least five minutes. Alternatively, you may use the DI hand sprayer to rinse a single piece. For very small pieces, you may rinse in a beaker.
      • To dry substrates, you may use the N2 gun.


    Disposing of Used Acids or Bases

    • HF drain

    HF-based acids such as BOE and acid mixtures containing HF must be poured down the HF drain. (These acids must NOT be aspirated or poured down the sink drain). First, carefully lift the HF drain lid. Then, using both hands gently pour the acid waste down the drain, being careful not to splash.  Rinse the etchant container with water three times, pouring the rinse water each time into the waste container. Log the approximate amount and composition of acid drained on the station log sheet, located on the left-side of the bench.

      • AWN system

      All standard acids or bases must be aspirated. Never aspirate HF-based mixtures or metal etchants .
      The temperature of the chemicals must be less than 120 C before aspirating.
      Do not pour these chemicals down the sink drain, as the sink is to be used only for rinsing.
      Remove the aspirator nozzle from its storage space and place the nozzle into the chemical container.

      Press the green "Aspirator" Start button.
      Aspirator start stop

      Once the container is empty, use the DI hand sprayer to rinse the inside. The aspirator will drain the rinse water. Do this three times. If the aspirator times out before you are done, press the green"aspirator" Start button again.
      Lift the aspirator nozzle off the bottom of the container. Hold it either over the container or over the rinse sink. Thoroughly rinse the end of the nozzle with the DI hand sprayer. Continue to hold the aspirator until the nozzle end stops dripping and return the aspirator nozzle to its storage space.

      Press the red "Aspirator" Stop button.
      Rinse the inside and outside of the container in the rinse sink.
      Log the approximate amount and composition of chemicals drained on the station log sheet, located on the left side of the bench.

      We are required by the Stanford University - Utilities Services (Environmental Quality and Water Efficiency) to distribute the Best Management Practices (BMP) fact sheet, you'll find the link here in the Stanford University - Utilities Services folder.
      Please read the fact sheet and reduce the amount of pollutant for example by using smaller quantities of chemicals.

      Hazardous waste collection

      Metal etchants (including gold and chrome etchants) and mixtures containing solvents like SRS100 or PRS1000 must be collected in waste containers, labeled and sent out for hazardous waste disposal and must absolutely not be aspirated or poured down the rinse drain.  Any waste containing toxics and heavy metals must be collected locally. Toxics and heavy metals include, but are not limited to, the following:

      Antimon, Arsenic, Barium, Beryllium, Boron, Cobalt, Manganese, Molybdenum, Selenium, Thallium, Vanadium, Cyanide, Formaldehyde, Gold, Phenols.
      Any chemicals on the Federal List of Acutely Hazardous Chemicals or the California List of Extremely Hazardous Chemicals must also be collected locally. When in doubt, check with the SNF staff.


      If you are working with multiple chemical mixtures, make sure to use separate containers for collecting different types of waste (acid versus base, for example.)
      • Cleaned, empty hazardous waste containers and caps, and blank hazardous waste disposal labels are stored in the service area behind the furnaces left to the flammable cabinet. The containers have been chemically decontaminated by staff and their labels should be defaced. Contact the stockroom staff if containers, caps, or labels are missing. Do not use empty chemical containers from the chemicals pass-through as they are not decontaminated and pose a chemicals hazard.
      • Use a funnel (make sure it is chemically compatible with the etchant) to pour the used etchant into the appropriately labeled waste container. Rinse the etchant container with water four times and pour the rinse water each time into the waste container too.
      • Cap the container, making sure that the outside of the container is clean and dry. Transport the container using the transfer cart. Place the container on the appropriate shelf in the chemicals pass-through. 
      • Stanford EH&S is picking up the hazardous waste bottles only if they are properly labeled.
        EH&S prefers the online waste tag, but a SUNet ID is required. Labmembers without SUNet ID, please fill out the paper waste tag.

        EH&S Stanford chemical-waste-pickup

        EH&S Stanford waste-tag
      • How to fill out the paper Hazardous waste label:

         Hazardous Waste Tag filled out
        1. Month, day, and year are required. Enter date when material becomes a waste, or when the first drop of waste was put into the container (not the date purchased or the date it was first opened).
        Your name, your phone number and your department are required. Building and room number should be the exact location where waste is kept.
        Bldg.: Paul G. Allen Building
        Room: L109
        Use complete, proper chemical names.  DO NOT use acronyms or trade names ("Cr14 etch") but list all the chemicals in the mix. Stanford EH&S (Environmental Health & Safety) department needs to know what the chemicals are in order to properly sort and dispose of them (and they are not going to know what "Gold Etch" or "AL12" means.)
        Provide an estimate of the % of each constituent so the total equals 100%.
        Check one only
        Note the primary hazard.
        Leave the remaining section blank.

        Here is an example how to fill out the hazardous waste tag for chromium etchant:

        Hzardous Waste Tag filled out
        Attach the Hazardous Waste label to the waste container.


      • Fill out the logsheet.

      • Clean up your workspace. Ensure the benchtop is clean and dry.

      • Leave rinsed labware on the table opposite to this bench. Return dry labware into the appropriate shelf or cabinet.
      • Turn off the heater/stirrers or constant temperature bath.

      • Leave the main power on.

      • Disable wbflexcorr-3 or wbflexcorr-4. 



          • Keep the benchtop clean. Thoroughly rinse off any drips (assume they are chemicals) with the DI hand sprayer, gently dry with the N2 gun. Avoid using cleanroom wipes to clean up unknown drips; these are then considered hazardous waste and must then be handled and disposed of accordingly.

          • Do not leave cleanroom wipes on the bench top. These have a tendency to get sucked up towards the back of the bench by the exhaust, and into the chemical containers which not only contaminates them, but presents a serious fire hazard.

          • Check the bench for any damage or any other obvious problems. Report it on Badger and notify Maintenance if any problems are observed
          • Chemicals aprons and face shields should be checked and changed if any staining or other damage is observed.

            Monthly (Maintenance)

          N2 gun filters should be changed

          Emergency Shutdown

              • In the event of an emergency, the wet bench should be shut down by pressing the EMERGENCY POWER OFF button located on the upper left corner of the control panel. This will shut off all power to the bench.

              • If the exhaust shuts down while there are chemicals in any beakers or other open containers at this station, EVACUATE THE LAB.

                Extended Shutdown

              • Bench top and plenum should be thoroughly rinsed and drained. Main power should be shut off to the system.


                  If you are having any problems with equipment, contact Maintenance.


                    BACKUP EQUIPMENT

                    The Wet Bench wbflexcorr-1 and 2 may be used as a backup.


                    ADDITIONAL PROCESS INFO

                    Aluminum etch:
                    Aluminum (Al) etch: find more information on the wbmetal page

                    Chromium etch:
                    Chromium (Cr) etch 1020AC from Transene:
                    Cr etch times range from 15 seconds to 60 seconds at room temperature
                    compatible with positive and negative photoresists
                    20 % Ceric Ammonium Nitrate, 10 % Acetic Acid, and Water 70 % -Primary Oxidizer, corrosive

                    Gold etch

                    Gold (Au) etch TFA from Transene:
                    Au etch rate at room temperature: 28A/sec
                    Potassium Iodide (KI) 42 %, Iodine (I2) 10 %, Water 48 % - Toxic

                    SRS-100 (in use since October 2015, it replaces PRS3000)
                    SRS-100 is used to remove resist from wafers with  standard metals.
                    Caution, it etches copper.
                    SRS-100 consists of:
                    N-Methyl-2 pyrrolidone (NMP) ~60%,
                    Tetramethylene sulfone ~30%,
                    Isopropanolamine ~10%
                    Primary hazard classifications are: flammable and mildly corrosive and flashpoint is 93C. Please read the MSDS before using it.
                    Wafers must be very dry before going into this resist stripper, otherwise the exposed metal may be etched. Recommended processing temperature and time is 60C for 20 minutes. The SRS-100 resist strip is effective when resist has been used for masking wet aluminum etching. However, resist which has been used to mask implant, AMT oxide etch, or P5000 aluminum etch , or plasma etch is hardened by these processes and will require a special plasma etch prior to SRS-100 to be completely removed.
                    Please read the Technical Note for PRS3000:
           disposal and must absolutely not be aspirated or poured down the rinse drain.

                    For the procedures of the specific processes which are normally performed at this station, check the Additional Process Info link:
                    Additional Process Info

                    How to etch silicon:
                    - KOH (Potassium Hydroxide) etching of Silicon using the Controlled Temperature Bath (CTB)

                     - Silicon wet etching at SNF

                    How to etch silicon dioxide at SNF.

                    How to etch silicon nitride at SNF.

                    Here are links to two papers from the IEEE regarding etch rates for various etchants and materials including etch rates.  These papers are the standard starting place for wet and dry etching.  Some of the

                    etches, tools and materials will not be applicable for processing done at SNF.

                    Various Etches for wet and Dry Etching- 1996


                    Various Etches for wet and Dry Etching- 2003



                    Short Sheet for the wbflexcorr-3 and -4:

                    1. Make reservation for wbflexcorr-3 or wbflexcorr -4.

                    2. Check exhaust system.

                    3. Check AWN system.

                    4. Make sure there are no chemicals left from the previous user.

                    5. Make sure the bench is dry and clean.

                    6. Enable wbflexcorr-3 or -4. Only two labmembers are allowed to use the bench at the same time.

                    7. Press power on.

                    8. Switch hood light on.

                    9. Switch on ctb or hot plates, make sure the ctb is filled up with water.

                    10. Place empty beakers inside of bench (glass or quartz beakers for heating up chemicals or self heating chemical mixtures; plastic beakers for anything containing HF).

                    11. Prepare Teflon holders.

                    12. Fill out "In Use Hazardous Chemicals" cards", for each beaker one and place cards under beakers or next to it if the hot plate or ctb are being used.

                    13. Fill up rinse beaker with DI water.

                    14. Check apron and Nitril gloves. Clean face shield at wbsolvent using IPA.

                    15. Put on apron, face shield, and Nitril gloves over latex gloves.

                    16. Transfer acids or bases (solvents are not allowed) using plastic cart from chemicals passthrough to wet bench.

                    17. Place chemical bottle inside of bench behind the red tape (6 inch).

                    18. Fill up beakers with chemicals.

                    19. Rinse and dry outside of bottle if contaminated with chemicals.

                    20. Return chemicals to the of passthrough.

                    21. Place wafer using Teflon holder in chemical beaker.

                    22. After the etch, place Teflon holder in rinse beaker.

                    23. Rinse wafer and rinse beaker in sink.

                    24. Dry your wafer using N2 gun (be carefull with pieces).

                    25. Drain any etchant containing HF in HF drain, acids or bases in the AWN system using the aspirator (temperature under 120C), and metal etchants in hazardous waste bottle.

                    26. Rinse all chemical beakers three times with water and drain in appropriate waste collecting system.

                    27. Rinse chemical beaker in sink.

                    28. Leave beakers and holders on table opposite the wbflexcorr-3 and -4 for drying. Never leave labware at the wbflexcorr-3 and -4.

                    29. Rinse and dry bench, you can rinse the hot plates too. Never rinse the heating unit for the ctb.

                    30. Remove Nitril gloves, face shield, and apron.

                    31. Switch off hot plates or ctb if used.

                    32. Discard blue cards.

                    33. Fill out chemical log sheet.

                    34. Disable wbflexcorr-3 or -4.



                    The wbflexcorr-3 and -4 has the following facilities: HF acid waste drain (awhf-f13), acid waste neutralization drain (awn-f15), deionized water (dih2o-f9), scrubber exhaust (exhsc-f16), house nitrogen (hn2-f1) and industrial water (iw-f12).

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