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Fiji1

Fiji1 is a load-locked, plasma-enabled atomic layer deposition (ALD) system. Coupled with Fiji2, Fiji1 is a Fiji F202 system from Cambridge Nanotech and is used for plasma assisted ALD of various dielectric and metallic films. The system can accommodate pieces up to an 8" wafer. Fiji1 is currently classified as semi-clean.

Picture and Location

 map of fiji-l and fiji-r location in snf

Fiji1 and Fiji2 are physically contained in a single frame, although each tool is completely separate and autonomous from the other.  They are located at the end of the first aisle on your left as you enter from the gowning room.

Background

 Atomic layer deposition (ALD) is a type of chemical vapor deposition that utilizes a cycling of different precursor gases to produce monolayers of a particular solid film.  In conventional LPCVD as performed in the SNF furnaces the precursor gases are mixed continuously and are so reactive that the solid films are formed everywhere including occasionally in above the substrate surface.  Conversely, in ALD first one precursor is introduced which will ideally completely and with self-limitation coat the substrate with a single molecular layer.  The second precursor again in a self-limiting process reacts with the first molecular layer at the surface to produce a monolayer of the desire material.  The key is finding a chemistry for the ALD precursors that can react at under the appropriate pressures and thermal energy the system can deliver, but will not desorb from the surface in the reactor conditions.  This "energy window" for proper ALD growth is shown schematically in below (fromAtomic Layer Deposition for Nanotechnology by Arthur Sherman):

ALD energy window

 

Because of the self-limiting nature of the sequential percursors, ALD systems can achieve near monolayer-at-a-time growth conditions with extreme uniformity over large areas.  Additionally, the thin films have tremendously conformal coatings even under extreme topology.  The films in general are dense and provide excellent interface preservation.  However, the deposition rate is exceedingly slow (in general on the order of an Angstrom/minute) and this technique is not ideal for films thicker than a few tens of nanometers.

With the addition of plasma, the ALD window is no longer only dependent on temperature to supply the appropriate energy for a reaction to take place.  Because of this many recipes are possible at temperatures not possible with thermal processing only.  Additionally, some ALD processes can be achieved only by plasma assistance.

A more detailed introduction to ALD can be found in this presentation (given by Dr. J Provine 11/1/12 at Stanford University):  ALD Introductory Tutorial 2012-11-01

A summary of more in-depth ALD processing information can be found in this presentation (given by Dr. J Provine 11/1/12 at Stanford University): ALD In Depth Tutorial 2012-11-01

 

Process Capabilities

Cleanliness Standard

 The Fiji1 is classified as semi-clean.  The temperature range of the chamber is determined largely by the materials to be used.  The minimum temperature is set by the requirement that a positive thermal gradient exist from the precursor to the substrate (this prevents undesired condensation and potential valve clogging).  Thus the precursor input lines/manifold must be hotter than the precursor and the chamber must be hotter than the manifold/input lines.  The upper temperature limit is hard limited by the software at 350C for the chuck and 200C for the input line/manifold.  In an effort to maintain cleanliness in the system the following materials are not allowed:

1.       Polymers not specifically approved by the superuser.

2.       Samples from gold-contaminated equipment

3.       Wet samples

4.       Glass

5.       Plastic, including Teflon

6.       Non-encapsulated particles

7.       Chips that are so small they will come off the substrate and fall into the pump line.

A Note on III-V Materials

Traditionally III-V materials in SNF are classified as gold contaminated.  However, because the Fiji1 operates at low temperatures III-V materials can be used in the Fiji1 under the following conditions (failure to adhere to these rules will result in removal from use of the tool):
1. The III-V materials in question do not violate any of the above restrictions
2. Users wishing to use III-V materials must speak directly to the quality circle about their plans before beginning to use these materials in the system.
3. III-V materials should never touch the inside of the deposition chamber or the tweezers that are used in the chamber.  A clean Si, SiN, or SiO2 substrate must be used as a carrier wafer.  
 

How to make a Carrier Wafer for the Fiji

Currently the best starting point for a carrier wafer for the fiji is not entirely understood.  Instead of being a cross-flow system like the Savannah, the Fiji has a top down air flow.  As a recommendation, please discuss your carrier wafer needs with the superusers and make suggestions.  For now, a good starting point is making a similar carrier wafer to those used in the Savannah:
 
1. Grow about 100nm SiOon a Si <100> wafer.  SiO2 can be deposited, but needs to be on both front and back.
2. Pattern SiO2 with resist.  The pattern should be a larger area than your piece as this pattern defines your pocket.
3. Dry etch SiO2. Note: wet etch does not work because you need to keep the backside oxide.
4. Strip the photoresist.
5a. Wet etch Si wafer with SiO2 as a mask in TMAH heated to about 90C for a few hours.  This makes a recess with depth dependent on your initial mask because TMAH stops on the Si 111 planes.  The chips can sit on the crystal smooth angled sidewalls of the trenches, which are very flat allowing good thermal conduction from the substrate, and hence the substrate heater, to your chip.
5b. You could also try a DRIE of Si to define your pocket.  Here the etch would be vertical and your pocket would have an approximately horizontal floor.
 
Processing small chips
To process a small chip (< 1cm x 1cm) you should also prepare a carrier wafer as they will blow off the chuck and into the exhaust line.

Performance of the Tool

What the Tool CAN do

  • Deposit high quality metal oxides
  • Deposition of oxide free metal nitrides and elemental metal films with low contamination
  • Tightly controlled thickness through monolayer at a time growth.
  • Thin film deposition with angstrom precision
  • Ultra-conformal deposition thermal processing
  • Depositions assisted by H2, N2, or O2 plasmas.
  • Uniform coverage on aspect ratios of roughly 20:1 for plasma deposited films


What the Tool CANNOT do

  • Deposit thick films.  This is because of both the slow deposition rates and the expense of material precursors.
  • Films thicker than 50nm require prior approval from the quality circle.

  • Selective ALD is a difficult issue and current research topic...it should not be expected that materials will deposit on only certain materials.
  • ALD of certain films has not been demonstrated (Au for instance).  If you want to try something not currently available, please consult the quality circle or the ever-expanding ALD literature.


The System

The Fiji system consists of two identical chambers (Fiji1 and Fiji2), which are completely separate and autonomous.  The differences between the systems are their cleanliness level (Fiji1 is semi-clean) and the presence of an ozone generator (only available on Fiji1).  THE OZONE GENERATOR FOR FIJI1 IS NON-FUNCTIONAL.  They each have the following components (diagram courtesy of Cambridge Nanotech):


Fiji diagram

NOT PICTURED:
  • A vacuum loadlock chamber
  • A pump to maintain low pressures in the chamber and remove unreacted precursor
  • A electronic control box (called the "e-box") that controls all of the heaters, valves, etc and communicates with the control computer via USB
  • A control computer (a non-networked PC running Windows 7)
  • H2, N2, and O2 gas lines for plasma


Possible Films

The films available on the Fiji1 is determined by the precursors installed in the system.  In general, anything possible on the Savannah or the Fiji2 is possible on the Fiji1.  The Fiji1 tool is currently maintained without a DI water source so primarily plasma assisted recipes are recommended.  If you need to run a thermal film on the tool, please discuss with Michelle Rincon (mmrincon@stanford.edu) or J Provine (jprovine@stanford.edu) to discuss.  The list of available precursors is maintained on this page and also on a file on the desktop of control computer.  The file on the computer is the final word on what precursors are installed on the system currently.  In the event that this website and the file on the computer disagree - follow the document on the control computer.

Current films available (in stock precursors):
*Please note film deposition rates listed are specified to one significant digit for estimation purposes.  For applications with tight thickness specifications it is recommended the user perform some process characterization to ensure precise depositions.

Film   NOTES Tools Deposition rate (A/cycle) @ temp) Thickness Nonuniformity over 2 100mm wafers)  Precursor 1  Precursor 1 temperature   Precursor 2 
Thermal Al2O3  Well characterized Fiji3, Fiji2, Savannah 1 @ 200C 1% Trimethylaluminum  Unheated   H2O  
Plasma Al2O3   Well characterized  Fiji1, Fiji2 1 @ 200C 0.50% Trimethylaluminum   Unheated   O2 plasma  
Thermal TiO2  Being characterized Fiji3, Fiji2, Savannah 0.4 1% Tetrakis(dimethylamido)titanium(IV)  75C   H2O  
Plasma TiO2  Being characterized Fiji1, Fiji2 0.4 2% Tetrakis(dimethylamido)titanium(IV)   75C   O2 plasma  
Plasma TiN  Well characterized  Fiji1, Fiji2 0.5   Tetrakis(dimethylamido)titanium(IV)  75C   N2  plasma
Plasma WN  In development Fiji1, Fiji2     Bis(ter-butylimino)bis(dimethylamino)tungsten(VI)  60C (TBD)   N2 plasma
Thermal HfO2  Well characterized Fiji3, Fiji2, Savannah 1.0 1% Tetrakis(dimethylamido)hafnium   75C    H2O 
Plasma HfO2   Well characterized Fiji1, Fiji2 1.0 1% Tetrakis(dimethylamido)hafnium(IV)   75C   O2  
Thermal ZrO2   In development  Fiji3, Fiji2, Savannah 0.8 1% Tetrakis(dimethylamido)zirconium(IV)   75C   H2O  
Plasma ZrO2  In development Fiji1, Fiji2     tetrakis(dimethylamido)zirconium(IV)   75C   O2 plasma 
Thermal Ta2O5  In development  Fiji3, Fiji2, Savannah     Tris(ethylmethylamido)tert-butylamido)tantalum (V) 105C H20  
Plasma Ta2O5   In development  Fiji1, Fiji2     Tris(ethylmethylamido)tert-butylamido)tantalum (V) 105C O2 plasma  
Plasma TaN   In development  Fiji1, Fiji2     Tris(ethylmethylamido)tert-butylamido)tantalum (V) 105C H2 plasma    
Plasma SiO2  Being characterized  Fiji1, Fiji2 0.8 1% Tris[dimethylamino]Silane   Unheated   O2 plasma  
Thermal Pt   Being characterized  Fiji1, Fiji2, Savannah 0.4 (plus substrate dependent nucleation)   Trimethyl(methylcyclopentadienyl)platinum(IV)   80C   O2  
Plasma Pt   Being characterized  Fiji1, Fiji2 0.5   Trimethyl(methylcyclopentadienyl)platinum(IV)   85C   O2 plasma  
Thermal Ru   In development  Fiji1, Fiji2, Savannah     Bis(ethylcyclopentadienyl)ruthenium(II)  TBD   O2 and H2  
Plasma NiO   In development  Fiji1, Fiji2     bis(cyclopentadienyl)-nickel   TBD   O2 plasma 
Thermal ZnO In development Savannah     Diethylzinc Unheated   H2O  
Silanization No characterization       APTES (3-Aminopropyl)triethoxysilane    
Indium Oxide No characterization       Cyclopentadienylindium(I)    
GaN No characterization       Trimethylgallium    
Thermal SnO2 Being characterized Fiji2     Tetrakis(dimethylamido)tin Unheated O2 plasma 
Thermal FeO
In development
Fiji2


Ferrocene (BIS(CYCLOPENTADIENYL)IRON) 60C
O2 Plasma
FeO
In development
Fiji2


Fe amidinate (accudep Iron)
TBD

Thermal Y2O3
In development
Fiji2


Tris(Cp)Y
165C
H2O
La2O3
In development
Fiji2


Tris(i-propylcyclopentadienyl)lanthanum
TBD

BaO
In development
Fiji2


Bis(pentamethylcyclopentadienyl)barium, 1,2-dimethoxyethane adduct
TBD

BaO
In development
Fiji2


Bis(n-propyltetramethylcyclopentadienyl)barium
TBD

Co3O4
In development
Fiji2


Bis(cyclopentadienyl)cobalt(II) TBD

Thermal SrO
In development
Fiji2


Bis(1,2,4-tritertiarybutylcyclopentadienyl)strontium
110C



For the list of currently installed precursors consult the Fiji1 control program and badger for the most recent changes.

  • If the precursor or film you want is not shown here, please contact the quality circle.  New materials and special runs can be possible as needed and with appropriate planning.

 

Contact List and How to Become a User

Contact List

The following people make up the Tool Quality Circle:

  • Process Staff: Michelle Rincon (mmrincon at snf dot stanford dot edu)
  • Maintenance:  Michelle Rincon (mmrincon at snf dot stanford dot edu)
  • Super-Users:  J Provine (jprovine at stanford dot edu)

 

Training to Become a Tool User

Fiji1 and Fiji2 have a the same training protocol.  If you are qualified for one, you will be simultaneously be qualified for the other.

Becoming a Fiji1/2 operator is a three stage process.

  1. Shadowing.  Contact a current user of the Fiji (either 1 or 2) and request that they introduce you to the system and demonstrate the use of the system for you.  If you do not know a Fiji user, contact the user list (fiji1 at snf dot stanford dot edu or fiji2 at snf dot stanford dot edu) or check badger for upcoming user reservation.  It is up to the user if they are willing to have you shadow them.  If you have trouble finding someone to shadow, please feel free to contact the quality circle for help.  (Helpful hint:  Be familiar with the information here on the wiki before you shadow and be sure to ask lots of questions during the shadowing.)
  2. Written Quiz.  After shadowing a user, contact Michelle Rincon or J Provine to take the short written quiz for the Fiji1/2.  The quiz is closed book and all the information should be known to a someone who has studied the online documentation and has gone through a shadowing.
  3. Oral Qualification Exam.  After the written quiz has been passed, you may schedule a final oral qualification exam with a superuser.  At this exam you are expected to demonstrate your ability to run the tool safely and appropriately without any input.  Once this final stage is satisfactorily passed, you will be given full access and utilization for the Fiji1 and Fiji2 as an operator.

Additional training is required to become an engineer.  At the engineer level you can compose and save new recipes as opposed to an operator when you can only edit recipes.  Perhaps more importantly, as an engineer you may adjust set-points on the Fiji.  These set-points are designed to protect the machine from ill use.  As such only those who complete the necessary training to become an engineer will be granted access at that level.

To become a Fiji1/2 engineer you must complete these steps:
  1. Provide a project proposal outlining the needs of the engineer status and the parameters under which you will use the system.
  2. Read all documentation relevant to the Fiji system.
  3. Pass a closed book exam about the concerns both safety- and process-wise related to changes in the Fiji process conditions and set-points.

Operating Procedures

Basic Operation Instructions

Reservations

  1. Make reservation in badger.
  2. At least 24 hours prior to reservation time, make a comment in the maintenance section to request the specific precursors you would like to use for your run.  The precursors are swapped frequently so do not assume that a precursor that is on the tool when you make your reservation will still be there when you are going to be running.  If your reservation is for the weekend, please make the comment by the end of the day Thursdays.
Initial Checks
  1. Enable the system on badger.  Check the maintenance comment labeled "precursor status" to verify your precursor is available.  Do not operate the system without being enabled on badger.  Wafers found in the system without badger enabled will be removed at the discretion of the enabling user.
  2. Check that the system is in working condition:  the loadlock is pumped down, all the heaters enabled and within range, the precursor lines have the materials you need, and the reaction chamber is pumping to below 100mTorr with a carrierflow set to 0 sccm for both the Ar lines.  If any of these features are not found to be in range, report the situation on badger.  
  3. Load your desired recipe:  right click on the recipe in the control software and select from the Windows file list.
  4. Edit your recipe as needed:  see the More on Recipes subsection for more information about writing and editing recipes.

Loading and Unloading Wafers (Details given in instructions below diagrams) :

    Fiji unload

ALD diagram- neutral in load lock

ALD diagram- Transfer plate INTO chamber

Loading the substrate

 

    1. Vent the loadlock by pushing the "VENT LL" button in the VACUUM section of the control software
    2. Transfer your wafers into the load lock (Be Careful It can be HOT depending on when last in the chamber).  Please wear clean, new gloves when you are in the load lock.  Note if there are any particles present and wipe them up with clean-tech wipes if needed.
    3. 2.1 raise the arm to almost max height
      2.2 insert arm
      2.3 should go in until 1cm or so of maximum arm depth
      2.4 push in with some force until the arm is fully inserted (you will feel a click)
      3.0 without turning, pull out the substrate holder at the same height. Check through the window in the loadlock that the sample carrier and your sample were retrieved.
    4. Close the load-lock lid and pump the chamber by pushing the "TRANSFER SAMPLE" button in the VACUUM section of the control software
    5. Introduce the sample by using the magnetic transfer arm.  NEVER push forcefully in any direction on the transfer arm.  The arm should enter smoothly until obstructed by the gate valve at which point you can lift the substrate carrier by turning the transfer arm.  Keep the arm elevated and push it all the way into the system. 
    6. Lower the arm 1/8th of a turn below the neutral point and fully retract the arm, leaving the sample behind in the chamber.
    7. Click "OK" on the software to close the gate valve.

    Running the process.

     

    1. Check to make sure the chamber reaches base pressure (this should only take a couple of minutes).
    2. When the system has reached base pressure (check that it is similar to what base pressure you found the system in - different by not more than a few mTorr), run your recipe by pushing the "START" button
    3. Check to make sure the pressure pulses of your recipe are in the correct range by monitoring the pressure readout in the control software.  Typical pressure pulses are one hundred mTorr or more above the base pressure.
    4. If you have a plasma component to your recipe, make sure the plasma strikes and the reflected power quickly drops to within a few W of zero.
    5. When the process finishes, check that the base pressure has returned to the initial value.  This checks that the system is not leaking and has returned to its original state.

    Removing the substrate

     

    1. Push the "Transfer Sample" button in the VACUUM section of the control software.
    2. When instructed, insert the transfer arm at the neutral height all the way into the chamber to the stop point.  NEVER force the arm or push with unnecessary force.  You may need to "wiggle" the height a little to ensure the transfer arm correctly mated with the substrate holder.
    3. Lift the substrate holder up approximately a quarter turn, and gently remove the transfer arm fully.  You should feel little to no friction or resistance to this action.  Check through the window in the loadlock that the sample carrier and your sample were retrieved.
    4. Click "OK" on the control software.  
    5. Vent the Loadlock by pushing the "Vent LL" button in the VACUUM section of the control software.

    Retrieving your sample and shutdown

     

    1. Retrieve your samples from the substrate carrier using proper tweezers and gloves (it will be hot, be careful you do not melt anything onto the carrier).  
    2. Shut the lid to the load lock and transfer the empty substrate holder back into the chamber following steps 2-6 of the Loading the substrate section.
    3. Run the standby process (00-STANDBY on each system).  By having the substrate holder in the chamber and running the standby program we improve chamber cleanliness by reducing particles from temperature cycling and keeping a small background flow of Ar in the chamber.  Also the standby program provides quick insurance that all process gases are off except for the carrier.
    4. If the next user asked you to adjust the chamber temperatures for them, please do so.
    5. Disable the system on badger.

    If you need to stop your deposition at any time during the process, press the "STOP" button which will leave the heaters and the pump on but stop the recipe.  It is not necessary to close the control program overall.  If you do accidentally log off the computer or close the control program, open the program up again, run it, and load & run the STANDBY program.


    A Note on Heating and Cooling

    There is no active cooling available on the Fiji and as such it can take a very long time to cool the chamber down.  As an example it is roughly 3 hours to cool from 200C to 140C.  Heating up the system is quicker, but also takes a not insignificant time because of the mass of the chamber.  With this in mind it is good practice to interact with the users scheduled before and after you to help get the heaters set as early as feasible.  
    NOTE:  if you adjust the heaters, but log off on badger, it is perfectly reasonable that someone else can come along, enable the tool, and adjust the heaters for their use.  Bare this and the time to heat and cool in mind when making your reservations.
     

    Reservations

    The following restrictions are in place for reservations on Fiji1:
    1) The maximum reservation window is 7 days.
    2) The maximum primetime reservation any day is 4hours.
    3) The maximum reservations allowed is 24hours.

    Recipes

    The recipes are all maintained in the folder C://Recipes/.  Standard recipes listed in this document are kept in that folder.   

    The parameters you can control in a recipe are listed below with comments about each:

    Parameter Notes
    Heater  Each heater has an unique item number and a value given in degrees Celsius.  Do not overheat precursors (all precursors should be below 115C and some should not be heated at all - consult with quality circle if unsure).  The reaction chamber should always be hotter than the manifold which should always be hotter than the precursor lines.  The upper limits on temperature are protected by setpoints internal to the system.
    Flow This controls the flow of through a number of MFC.  The plasma process gases are controlled by these MFCs as are the carrier gases.  It is defined in sccm.  It is not recommended to adjust the standard flow values in recipes. The MFCs for H2, N2, and O2 additionally have a hard off state and should be set to zero and then closed.  This is already established in all recipes on the tool. 
     Pulse This command is for pulsing a precursor line.  It requires an ALD valve number and the amount of time you want the valve open in seconds.  The fastest these valves can fire is roughly .015 seconds, so note that even if you define a shorter time that is likely the valve open time you will get.  (NOTE:  when writing a recipe the time in seconds needs a digit to the left of the decimal place; thus you should use "0.015" instead of ".015" for the minimum duration pulse.) 
     goto Used to define loops in the recipes.  This command takes as an input the step to which the recipe should return. The value for this command defines how many times the loop will run.
     stabilize This command is used to hold a recipe until a heater has reached the desired value.  It takes as input a heater ID number and will wait until that heater demonstrates the set temperature with a degree C over a few seconds. 
     wait This command takes as input a value in seconds that you would like the system to wait before proceeding to the next command. (NOTE:  when writing a recipe the time in seconds needs a digit to the left of the decimal place; thus you should use "0.015" instead of ".015" for the minimum duration pulse.)  
     plasma This command indicates the power that should be generated by the RF plasma system in Watts. 
     stopvalve This command will close or open the output valve for the reaction chamber depending on a Boolean input.  This command is currently not used in any of the standard recipes, but development is beginning for recipes using this feature.
     line ac out Users should not use this command. It changes the heater voltage on precursor heater wraps.

     

    Example 1: Thermal Alumina Recipe 

    The table on the left is how the recipe looks on the tool.  The description on the right describes what each command does.

    Thermal Alumina Example Recipe

    Example 2: Plasma Alumina Recipe

    Plasma Alumina Recipe Example


    Tool Qualification Run

    Frequency

    Once a month the standard recipes will be run and results reported to this website. 

    Procedure

    A freshly RCA cleaned 4" 100 Si wafer will be run for each of the standard recipes for 100 cycles.

    A multi-point spectroscopic ellipsometry measurement will be made on the Woollam.

    The n and k values will be reported along with thickness and wafer uniformity.  If the values are out of the acceptable range, the system will be put into "Yellow" status and the cause will be explored by the quality circle.

    Responsibility

    Qualification runs are the responsibility of the quality circle.  They will be completed, including reporting, during the first week of a given month. 

    Machine Status States

    Red:  The tool is not capable of depositing any films and needs maintenance or verification of proper working conditions.

    Yellow:  The tool is capable of depositing some films or films of non-standard quality.  Reasons could include lack of necessary precursor, issues with the machine (pump, heaters, etc), or contamination that needs to be cleaned.

    Green:  The tool is in working condition for all available films, and those films were found to be within specifications.

    Process Monitoring Results & General Data

    Thermal HfO2 Deposition rate of 1.08A/cycle for standard recipe at 200C


    fiji-l thermal hafnia dep rate   fiji-l thermal hafnia temp dependence
     

    Plasma HfO2 Deposition rate of 1.01A/cycle for standard recipe at 200C

    fiji-l thermal hafnia temp dependence   fiji-l plasma hafnia temp dependence

    The breakdown voltage was found to be .4V/nm for plasma Hafnia films (no anneal) of thickness ~10nm.

    Many thanks to Tim Holme and Cheng-Chieh Chao and the team at QuantumScape for the breakdown data.

    Plasma TiN Deposition rate of 0.4A/cycle for standard recipe

    We have measured conductivities in the range of 15-20microohm-cm for TiN and Auger Electron Spectroscopy shows no oxygen present in the film.
    AFM measurements of 20nm TiN films shows a roughness of .2nm, which is on the order of a polish Si wafer.


    Thermal ZrOxide data (7/12/12)

    Thermal ZrOx Data
    Thanks to Elizabeth Friend from Rambus for the data!
     

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