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Tylan Oxidation and Annealing Furnaces, tylan1-4

The Tylan Oxidation and Annealing Furnaces are high temperature atmospheric furnaces made of pure quartz that allow for the introduction and mixing of gases (N2, Ar, O2 and H2) to grow silicon dioxide (SiO2) on silicon wafers. A quartz tube is brought up and maintained at a requested temperature by means of a heating element surrounded by an insulating material and encased in sheet metal. Quartz boats, which support the wafers while they are in the tube, are held aloft in the furnace by two quartz sheathed cantilevers.

Background

 

Process Capabilities (Cleanliness, Materials, Performance)

  • Tylan1 and Tylan2 are for clean work only.  The wafers processed in those furnaces are MOS clean, meaning that they have never had metal deposited on them, have been through a full KOH decontamination procedure and have not been processed in any equipment which is considered contaminated (sometimes referred to as ‘gold contaminated’).
  • Tylan3 is a silicide furnace.  Wafer which have silicides formed of SNF standard metals (Al, Al/Si, Ti and W) which have been deposited in clean metal deposition tools (gryphon and some materials deposited in SCT only) may be processed in tylan3.
  • Tylan4 is a contaminated furnace.  It may be used for non-standard materials and samples that have been processed in contaminated equipment.  All materials must first be authorized by staff.  This is to insure that materials processed in the furnace are compatible with high temperature processing.  Materials should not evaporate on to the tube surface or re-deposit onto other labmembers work.

Each furnace should conform to uniformity specifications of less that 5% variation in oxide wafer-to-wafer over a 50 wafer load and within-a-wafer.

 

Contact List and How To Become a User

Please follow the following procedure to become a qualified user of a tylan or thermco furnace;

 

Read all material on the SNF website concerning the specific furnace, including Background, Process Capabilities, Operating Procedures and Process Monitoring.

 

  1. Contact a superuser (link to superusers list) or qualified user of the furnace to arrange to ‘shadow’ them while they use the tool.  The reservation option on coral will show who will be using the tool in the near future.  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 furnace during this ‘shadowing.’  You may have to shadow the superuser or qualified user more than one time.
  2. During the shadowing session you should have the Shadowing Form for the person you are watching to fill out and an Equipment Checklist (see Training Checklist Section of this document).  You should use this checklist to make sure that the tool is completely covered.  You will have to be able to understand each point on it before the labmember notifies the staff responsible for training that you are ready for training.  Both of you must agree that you are ready.  You may have to shadow a labmember more than once.
  3. Contact the staff trainer to arrange for training on the furnace.
  4. If there is a written test for the tool you will need to hand it in to the staff member before training commences.  There is no test for the tylan oxidation furnaces.
  5. After training you will be given  provisional qualification status.  This allows you to use the furnace during staffed hours, 0600-1800 Mon-Fri only.
  6. Once a superuser or staff member has watched you and you have satisfactory demonstrated the proper use the tool you will be granted a full qualification to use the tool anytime, 24/7.

 

Operating Procedures

 

System Capabilities

  • Number of wafers per run: 50 4 inch wafers and/or 25 3 inch wafers.  Partial wafers may be accommodated; please see staff.
  • Wafer thickness: 250 um to 750 um.  Thicker wafers may be accommodated; please see staff.
  • Temperature range: 750C to 1100C.  Other temperatures may be accommodated; please see staff.
  • Oxide thickness: 50A to 2.0 um.
  • The labmember chooses both the temperature and the time of a furnace run.  Recipes have been written for specific temperatures and a partial listing of recipes is located at http://snf.stanford.edu/Equipment/tylanrecipes/  A full listing of recipes may be found on the disks at the Tycom.
  • To determine the appropriate time, labmembers may refer to the wet and dry oxidation charts in the lab or use the on-line oxide thickness calculator located at http://www.cleanroom.byu.edu/OxideTimeCalc.phtml
  • Labmembers may use either the nanospecs or ellipsometers to measure oxide thickness after the run is complete.  Users then log the results using the coral data collection forms that appear at 'disable' on coral.  You may enter data later by accessing you history information using coral.

 

Furnace Assignments

  • Tylan1 and Tylan2 are for clean work only.  The wafers processed in those furnaces are MOS clean, meaning that they have never had metal deposited on them, have been through a full KOH decontamination procedure and have not been processed in any equipment which is considered contaminated (sometimes referred to as ‘gold contaminated’).
  • Tylan3 is a silicide furnace.  Wafer which have silicides formed of SNF standard metals (Al, Al/Si, Ti and W) which have been deposited in clean metal deposition tools (gryphon and SCT, in some cases, only) may be processed in tylan3.
  • Tylan4 is a contaminated furnace.  It may be used for non-standard materials and samples which have been processed in contaminated equipment.  All materials must first be authorized by staff.  This is to insure that materials processed in the furnace are compatible with high temperature processing.  Materials should not evaporate on to the tube surface or re-deposit onto other labmembers work.  .

 

Cleanliness Standards

  • Substrates allowed; Si, SiGe, SOI and quartz.  No glass or plastic wafers.  All wafers must be clean and free of fast diffusers (metals, sodium KOH, etc) for tylan 1 and 2.  Materials that could contaminate tylan4 are not allowed. For example, no photoresist.  Wafers must be fully inspected for complete photoresist removal following any lithography process before the pre-diffusion clean starts.
  • Wafer must have undergone a complete pre-diffusion clean within 60 mins of loading into an oxidation furnace.  The pre-diffusion clean is described in these web pages; Process Modules for Diffusion Cleans.
  • The following cleans are allowed.
  1. A full pre-diffusion or LPCVD clean done at wbdiff
  2. A full pre-diffusion or LPCVD clean done at wbsilicide is acceptable for wafers going into Tylan3 only

 

User Protocol

  • These systems tend to be high-use tools, so please honor or remove any reservations you have made.
  • Try keep to a four hour limit per furnace per day during prime-time (Mon-Fri, 0800-1800).  Try to arrange to long oxidations or anneals on the weekend or over night.
  • For the oxidation furnaces, since a pre-diffusion clean is mandatory, one can easily if a labmember is not going to use their reservation.  You may use the reservation if the person who has signed up is not at least cleaning wafers 15 minutes into the reservation.  Please make your best effort to verify the person is not ready to use the system.  Also, if a furnace is not reserved, go ahead and reserve it for your use.

 

Check System Status - Standby Conditions

  1. Check the furnace status on coral; is it on shutdown?  Is there a problem message?  Is it enabled by another labmember?  Check out any problems that may have been reported with process or maintenance staff.  Do not use a furnace that has been shutdown.  Check the coral comments.  Here you will find the monthly qual results.
  2. Enable the furnace.
  3. Go to the furnace and using the STATUS button verify that the system is in ‘Ready’ mode.  You will not be able to load a recipe until ‘Ready’ mode has been achieved.
  4. If the furnace is in ‘Run’ mode, press the STATUS button until the recipe name is displayed.  If the program running is TLCCLEAN and it is at Step 40 with no time running, press ALARM ACK twice to get into ‘Ready” mode.  These programs are run once a week to clean the furnace in-situ, and they have long hold steps.
  1. Look around the furnace deck and adjacent tables for any handwritten notes from previous users of the furnaces.

 

Loading a Recipe (Program)

  1. Furnace programs are written by staff only.  If you need a program that you are unable to find on any of the floppy disks at the Tycom, please ask the responsible staff member to write one for you.
  2. To look at the status of all the furnaces type DI ST SY for DIsplay STatus of SYstem.  To look at a specific furnace use DI ST <furnace number>.  This gives you lots of information; is the furnace in Ready or Run mode?  Temperature of the load, center and source areas of the hot zone is displayed.  Also, gas flows can be seen.
  3. At the Tycom make sure you choose the correct floppy disk.  To verify that the desired program is on the disk, type ‘DI DI’ for DIsplay DIsk.
  4. To examine a program type ‘DI RE <recipe name>’ for DIsplay REcipe.  This is a good time to add up the time of all of the steps to get the total time of the recipe. Don’t forget to add the oxidation time you have chosen in the time variable step or steps.
  5. To load the program type ‘LO <recipe name><furnace number>’ for Load recipe.  You may be asked for one or more time variables and they must be inputted in the format hh:mm:ss.  You will need to specify the colons.
  6. Once all the variables have been loaded, the system will go into compile mode.  This may take a minute or so and the screen should read ’GOOD LOAD’ and ‘TASK COMPLETE’.  If there was an error, an improperly input variable for example, you will still get the ‘TASK COMPLETE’ message.  Check carefully that ‘GOOD LOAD’ has appeared as well.  If it hasn’t, you’ll need to load the recipe again.
  7. A word of warning; once you have loaded a program you will not be able to review the variables.  If there is any doubt in your mind about the correctness of the variable, simply reload the program.
  8. One last thing, you may check the status of the furnaces from outside of the lab by going to: http://171.64.100.113:7116/tylan/tylansummary.html  Every five minutes a 'snapshot' of the furnace status is posted on this site.  The user name and password are ; tylan.

Loading Wafers onto the Boats

  1. Push the run button at the furnace control panel –or- at the Tycom type ‘RUN <furnace#>.  This starts the program.  The first step of most programs is to pull the boats out of the furnace at a slow rate.  This takes about five or six minutes to complete, and the cantilever/boat assembly will be hot.  The usual idle temp of the systems is 800C.  Please be careful around it.  (As an aside, if you are going to use temperature lower than 800C, load the program two or more hours in advance so that the system has enough time to decrease and stabilize the new temp.)
  2. Ideally, we do not want the boats to be out of the furnace for more than 15 minutes.  This is to save wear and tear on the heating elements. They are somewhat difficult to replace.  You will need to calculate the total time of your program and note the time the program was started.
  3. Using the correct tweezers is essential.  For wafers polished on a single side, use the quartz vacuum wands that are provided at the furnaces.  In some cases there is more that one type of wand.  Please make sure that you are using the appropriate to your wafer cleanliness level.  For wafers polished on both sides do not use the vacuum wands- they will leave a scratch mark where they touch the surface.  Instead, use clean non-metal plastic (delrin) tweezers.  They must be cleaned according to; Tweezer Cleaning Module.  Use care with the plastic tweezers when unloading the wafers from the boats- they melt quite easily.  Metal tweezers, even Teflon coated are never to be used to load wafers at any of the furnaces.
  4. By convention, wafers are loaded with the frontside facing the furnace door and with the flats oriented up.  This way if there is a problem with your oxidation information about film uniformity can be given to responsible staff.  You may use the flat finder found near the furances to orient the wafers correctly.
  5. After loading the wafers onto the boats, press ALARM ACK to start pushing the boats back into the furnace.  From here on the program is automatic.  This is also the point at which you should note the time of day.
  6. Record the required information (program name, growth time, etc…) in coral at disable.  You may input the thickness data later by double clicking on your history entry in coral.
  7. Monitoring the recipe during the run is a good idea.  Make sure that the boats go completely into the furnace before leaving the area.

 

Unloading the Wafers and Completing the Oxidation Run

  1. The last step of the oxidation recipe is to pull the boats out of the furnace.  The wafers will sit out of the furnace until you give the command to go back into the furnace tube.  So remember to be sure that you are back to attend to the furnace within 15 minutes of the boats coming out.
  2. Unload the wafers after they have cooled enough that they will not melt the delrin tweezers, if you are using them.
  3. Once you have put the wafers into a storage box they are considered dirty and will need to go through a complete pre-diffusion clean if they require aother clean process step.  Many labmembers move their wafers directly from an oxidation step to an LPCVD step (poly or nitride) by loading the wafers into a clean diffusion cassette and taking it to the LPCVD load station.
  4. To end the program and push the cantilevers back into the furnace tube push ALARM ACK.  You will hear an audible alarm.  To stop it, push ALARM ACK once again.
  5. The furnace is now back into the stand by condition and can disable the tool.

 

Summary of Tycom Commands

Command
Description
Example
DI ST SY
Display status of system

DI ST SY C
Display status of system continuously (every 20 sec)

CTRL+C
Exit continuous mode

DI ST <number>
Display status of tube <number>
DI ST 1
DI ST <number> CO
Display status of tube <number> continuously
DI ST 1 CO
DI DI
Display directory on disk currently in drive

DI RE <name>
Display recipe <name>
DI WET1000
LO <name> <number>
Load recipe i<name> into tube <number>
LO WET1050 2
DI AL <number>
Display alarms on tube <number>
DI AL 4

 

Training Checklist

  1. Be familiar with basic equipment description.
  2. Know temperature range.
  3. Know min and max oxide thickness.
  4. Be able to locate Handy Dandy Oxide Thickness Calculator on the SNF website.
  5. Be very aware of the cleanliness level of each furnace.
  6. Know allowable materials for each furnace.
  7. Know the proper furnace cleans and their time limits.
  8. Be aware of user protocols.
  9. Show competency in determining whole system and specific furnace status at the Tycom.
  10. Know how to check and load a recipe.  Be familiar with the function of each of the steps in a recipe.
  11. Know how to correctly load wafers using vacuum wand or proper cleanliness tweezers.
  12. Abide by the 15 minute rule.
  13. Demonstrate correct use of nanospec and/or ellipsometer.
  14. Be knowledgeable in the use of coral data collection.

 

Process Monitoring and Machine Qualification

 

Purpose:

to provide verification and trend of a wet oxidation program and wafer-to-wafer and within-a-wafer uniformity of etch over a 50 wafer load.

 

Frequency of the test:

to be completed after major maintenance such as a pull and clean or injector change, or once monthly, or as needed based on user feedback.  Labmembers are encouraged to use this procedure before committing their work to critical runs to check that the furnace is operating correctly.

 

Documentation of results:

to be posted in the Coral equipment archive as a monthly comment for each of the four tylan oxidation furnaces and in the process data section of Coral.

 

Procedure:

 

  1. From the stock room get four wafers for each furnace, tylan1, tylan2 and tylan3.  Get two wafers for tylan4.  Use ‘L’ stock test wafers.
  2. Clean all wafers using standard pre-diffusion clean, 5:1:1 DI:H2O2:HCl last.
  3. Load wet program WET900 into all furnaces.  Time variable is 00:39:00.  This should grow between 900A and 1100A oxide.
  4. Load the wafers into the furnaces flats up (top) and polished sides facing out (load direction).  Arrange the wafers so that they are in the front and back positions of two boats.  See Fig. 1. Tylan4 will have one wafer in the front position of the first boat and one wafer in the back position of the second boat.  This will represent a 50 wafer spread.  See Fig. 2.
  5. Start the program and monitor the gas flows and temperature of the Load, Center and Source TC’s.
  6. After the program has finished (about 2hr) unload the wafers into the appropriately marked box for the furnace tested.
  7. Measure the wafers using the Woolam ellipsometer, Oxide program found in Staff Qual Recipes.   This will set up and automatic 9 point reading for each wafer.  Put the individual readings in a spreadsheet and save.
  8. Using Coral record results by going to History and clicking on the entry.  You'll be asked if you want to adjust the entry- answer no.  You'll next be asked if you want to record Run Data.  Answering yes will step you though the procedure.  Wafer IDs are <furnace number> <wafer position>, for example wafer ID 2-1 is the front wafer from tylan2.
  9. Note the reading for thickness and standard deviations for each wafer in corall comments.

 

ox qual position 1&2

 

 To View Recent Results

Recent monthly qual results may be viewed in graph form on Coral.  Results for a given furnace are given in the average of four wafers (two in the case of tylan4), front to back of the load.

 

  1. Chose a tylan oxidation furnace in Coral.
  2. Using the Process Actions tab chose Display Run Data.
  3. You will be prompted to chose a process.  Click on Furnace Qualifications.
  4. Click on WET900.
  5. Change the date if you'd like to go back more than three months.
  6. Keep the selection on Wafer Mean.
  7. Click on display.

 

 

 

 

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