Tystar Oxidation & Anneal Furnace Operation - Login | Nanolab, UCLA

Rev 4/14/04
Tystar Oxidation & Anneal Furnace Operation
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1.0 INTRODUCTION:
This document covers the operation of Tystar's oxidation and anneal tube (Tube 5) located in
UCLA's Nanoelectronics Research Facility. It sits in the left side bank of 4 tubes each of which
has its own heaters, and closed-loop temperature control, associated quartzware and load
system, and each of which has its own gas flow control system. Tube 5 is a general purpose
tube for anneals, drives and oxidations and does not require the same level of cleanliness as
Tube 1. Tube 5 is also of the older style which uses a process controller rather than tube
computer. The tube numbering and process assignments are as follows:
Right side bank
Topmost tube Tube 1 Anneal, Dry & Wet Oxidation- Very clean and
lightly doped samples only
2nd Tube from top Tube 2 Silicon Nitride (standard or low stress)
3rd Tube from top Tube 3 Polysilicon (doped or undoped)
Bottom tube Tube 4 Low Temp Oxide (LTO-doped or undoped)
Left Side Bank
Topmost tube Tube 5 Anneal, Drive and Oxidation for
heavy doped samples
2 nd Tube from top Tube 6 Currently not used
3 rd Tube from top Tube 7 Currently not used
Bottom Tube Tube 8 N2 sinter or Vacuum anneal (350-600C)
This system uses hazardous gases and high temperatures and therefore could cause serious
injury if any action is attempted without THOROUGHLY understanding the system. Refer to
the appendix (LPCVD Furnace Shut Down and Emergency Procedures) for safety related
information.
NOTE: While tubes 2,3 and 4 are LPCVD furnaces utilizing vacuum and toxic gases, tube 1
and 5 are atmospheric furnaces that do NOT use a pump or any kind of vacuum. They also do
NOT use any toxic gases and are therefore simpler systems to run than the other tubes. Tube
1 and 5 do use hydrogen and oxygen which are very flammable and potentially explosive
gases, however.
Successful deposition requires extreme cleanliness for anything that goes directly into the tube
or anything that touches anything which goes into the tube. Therefore:
• NEVER touch boats or wafer with your hands even if you are wearing gloves.
Use ONLY the appropriate boat holder. Boat Holder must be clean also.
• Use ONLY clean tweezers or vacuum wand dedicated for that tube. Clean these
implements often using alcohol, DI water and clean wipes.
• ALWAYS clean wafers using either piranah or RCA type clean right before loading
them into the tube. (NOTE: For the LTO tube ONLY a substitute clean for metallized
wafers may be used, otherwise the metal may be attacked.) Wafers must be Clean
and Dry. Use spin rinse dryer whenever possible. Never load a contaminated wafer
or boat into the tube as this will contaminate the tube as well.
• Wafers and boats coming out of the tube are extremely hot. Do NOT set them on
clean wipes, vinyl gloves or anything else which will melt. Set hot items on clean
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stainless steel bench or on dedicated quartz carrier.
• NEVER store flammable solvents (e.g. squeeze bottles etc.) at the LPCVD load
station; a fire could be started.
• ALWAYS wear a mask when loading and unloading your wafers into tube to
minimize contamination from your breath.
• ALWAYS minimize the time that the boat and loader remains out of the furnace
and makes sure the purge nitrogen is set to 3.5 liters whenever the tube door is
open to keep room air out of the tube.
• ALWAYS store dummy wafers in the tube which they are assigned. Dummy wafers
not needed for a run may be safely stored at the load station in a clean quartz
carrier. Promptly return dummies back to the appropriate tube when your run is
finished. NOTE: Tube 5 does NOT use dummy wafers.
2.0 SUBSTRATE CLEANING:
Wafers going into Tube 5 must be free from organics (e.g. photoresist etc.) and metals and
must have gone through a piranah clean or RCA clean just prior to loading or some other
approved clean (see staff for appropriate clean). Do NOT clean wafers the day before making
a run but rather within 3 hours of beginning a run. For the RCA clean see lab usage guide. For
the piranah clean, consult the piranha clean specification.
3.0 TYMGARD FURNACE CONTROLLER
The oxidation tube consists of a front panel mounted on the load side of the tube and a
remote controller located at the back of the tube. The remote serves as a manual override for
the front controller and should always be in the auto mode (manual light off), otherwise the
front panel will alarm and a recipe cannot be run. If the front panel is not responding to your
commands, verify the remote is in manual mode. If not press the manual button until the light
goes out. The remote unit may also be used to verify gas flow settings. Caution: The scrolling
front panel gas readouts show set points NOT actual flows.
Fig 1 shows the controls and their functions for the front panel. This controller is capable of
storing 23 recipes or 145 program steps not counting Recipe 0. Each recipe is given a
consecutive number 1, 2... 23.
3.1 Idle Mode (Recipe 0)
Recipe 0 is dedicated for the manual or idle mode. This allows valves, boat loader and
temperature to be immediately controlled from Recipe 0 without running a recipe. The idle
mode is also achieved by using Recipe 0. The idle mode is:
3.5L Nitrogen flow (5 liter max)
0 H2H/O2-High hydrogen/oxygen flow ratio (6 liter max high hydrogen
0 H2L/N2-Low hydrogen/nitrogen flow ratio (500 sccm max low hydrogen)
0 O2 Hi-High oxygen flow (3 liter max high oxygen)
0 O2 Lo-Low oxygen flow (500 sccm max low oxygen)
800°C Standby temperature with Auto Temp and Load on
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The furnace will remain in this mode until either a recipe is run or Recipe 0 is modified. There
is no time limit for recipe 0. Recipe 0 will automatically be entered when a program finishes
running or when the abort key is pressed.
Fig 1 Tube 5 Process Controller
To change the idle mode conditions to 4.5L of N2 at 900°C idle: (NOTE: This is done as an
exercise only; the furnace should normally be left in the idle mode as described above.)
1 Press Program button. (Program lite comes on and LCD asks Recipe ?).
2 Press "0 " followed by "Enter". (This tells the program to work on Recipe 0).
3 The LCD shows "N2 carrier 0000" which is the current nitrogen carrier flow in sccm.
4 Press "Enter" until "N2 3500" is displayed.
5 Press "4500" followed by "Enter" to change N2 flow to 4500 sccm.
6 The display now shows "O2 0000" since there is no oxygen flowing. Press "Enter"
to skip this step.
7 The display now shows "H2/O2 0000" since there is no hydrogen flowing. Press
"Enter" to skip this step.
8 The display now shows "TCA 0000" since no TCA is flowing. Press "Enter" to skip
this step.
9 The display reads "Temp C 800". Press "0900 Enter" to change the temperature to
900°C. (Note the temperature deviation meter to the right of the panel will go
negative and the heater LED will go full on as the furnace immediately begins to
ramp to 900 °C. The display now reads "OFST2..." which is a number
preprogrammed by management and should not be changed. You can continue to
press "Enter" to scroll back through the changes you made. Correct any
mistakes at this time.
10 To exit the Program Mode simply push the Status button. The display will
automatically scroll through the settings as follows:
- R00S01IDLE
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- N2 carrier 000
- N2 4500
- O2 0000
- H2/O2 0000
- TCA 0000
- Temp C 0900
NOTE: Always exit the Program Mode before leaving the furnace.
12 Following the above procedure change the idle mode back to the initial conditions.
To preview the idle mode conditions:
Either press "Enter" and continue to do so to single step through the recipe. This prevents the
status from automatically scrolling.
OR
Press "Preview" key followed by "0" and "Enter". Press "Enter" again to single step through the
program.
To return to automatic scrolling of status press "Status" key.
3.2 TYMGARD Function Switches (see Fig 1).
ABORT The ABORT switch immediately stops the run sequence and directs control to the
abort step. Each recipe must have an abort step called Step 0. The abort step is executed only
if the ABORT switch is pushed or when the external input is activated. When the abort step is
complete (finished), the TYMGARD returns to the Idle step (recipe 0) conditions.
ALARM ACK Alarms are indicated by a alarm message on the display and by the sounding of
an audible alarm. The ALARM ACK (alarm acknowledge) switch silences the audio alarm. If
there is more than one alarm condition, the ALARM ACK switch can be used to single step
through the display of alarm messages.
EVENT FUNCTION Each of the ten event function switches represents a different relay. Each
will typically be labeled with its function (e.g. N2, O2, etc.). These switches are functional only
during programming. They can be used to directly control the outputs while in the Program
mode of recipe 0 (Manual mode). The LEDs associated with the event switches indicate the
status of the output relays; the LED is on if the relay is on and off if the relay is off.
For the Nanolab's system, the following parameters (events) are programmable
1 N2 : Used to purge the tube with nitrogen (up to 5000 sccm). This
should always be at 3500 sccm during idle or when tube is open to
atmosphere.
2 H2H/O2: Used to control hydrogen/oxygen flow ratio for high hydrogen
flows(up to 6 lpm). See recipe sheets for proper flows.
3 H2L/O2: Used to control hydrogen/oxygen flow ratio for low hydrogen
flows(

important that opening of the Tube be kept as short as possible to
prevent contamination. Use Recipe 0 to Load and Unload your
wafers rather than programming this feature into your recipe.
8 VARITM Instead of having a fixed duration time in a step, any step in a
recipe can have a variable time (VARITM). This allows the operator
to defer the selection (choice) of step time until the recipe is to be
run. When programming a recipe, the VARITM switch is used to
declare a step as having variable time. When the recipe is run, the
TYMGARD will request the fixed time of the VARITM steps. The
operator must enter these times before the recipe actually begins
the RUN sequence. Varitime will usually be used for an oxidation
step.
9 STATUS The STATUS switch is used to place the display in the Status
(automatic scan) mode, where the parameters of the recipe step
currently in progress will be displayed sequentially. These elements
include recipe and step number, time remaining in the recipe, time
remaining in the step, and analog setpoint values. The state of the
relays is always shown on the LEDs.
If TYMGARD is in the Status mode, press the ENTER switch to cause the scan to halt at the
present item. Only this item will be displayed, and its value will change as directed by the
recipe. Press the ENTER switch repeatedly and the display will "single step" through the
status items in the normal scan sequence. Press the STATUS switch again and normal auto
scanning will resume.
10 ENTER The ENTER key inputs numerical data. Whenever a numerical
value is to be entered, the number is specified by using the
numerical keys (1,2,3,4,5,6,7,8,9, or 0), and then input by pressing
the ENTER switch. Also, see the STATUS switch operation given
above.
11 RUN The RUN button is used (pushed) to begin the execution of a
recipe sequence. The display will inquire which recipe is to be run,
RECIPE ?
One of the twenty-three recipes may be selected by pushing a numbered key (1, 2, 3 through
23) followed by pushing the ENTER switch. This begins the execution of the control sequence.
If one or more variable time (VARITM) steps are included in the recipe selected, the recipe
sequence starts after the times are entered.
The RUN LED illuminates when the RUN switch is pushed and remains lit throughout the
recipe, including the abort routine. The RUN LED goes out when the TYMGARD returns to Idle
condition.
12 HOLD When the HOLD function is pushed "on," the LED illuminates and
the counting of time is halted. The counting of time begins again
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when the HOLD switch is pressed a second time. While the recipe
is on HOLD, it may be edited (see PROGRAM Switch). The HOLD
switch has no other functions. The front panel HOLD switch cannot
override the external hold input; however, if the front panel HOLD
Switch is used in conjunction with external hold, the status display
honors the front panel command.
13 PREVIEW The PREVIEW switch provides the function to view the contents of
a recipe without the ability to change the recipe. When the
TYMGARD is in the Idle mode (no recipe running), PREVIEW may
be used to index through a recipe to preview the sequence and
setpoints. When the TYMGARD is in the Run mode, the
information in the recipe can be viewed without affecting the
currently energized steps or the timing of those steps. The LED is
illuminated when in the Preview mode. The Preview mode may be
exited by pressing PROGRM, STATUS, or the RUN switch. The
Preview mode may be exited without disturbing a recipe sequence
by pressing the STATUS switch.
14 PROGRAM The PROGRM switch places the TYMGARD into the Edit (program)
mode, enabling recipes to be entered or changed. While in the Edit
mode, the TYMGARD display will prompt the operator for recipe
information. The PROGRAM LED illuminates when this mode is
active. The TYMGARD may be set so that a password (code
number) must be entered to activate this mode. To exit the
Program mode, press the PREVIEW or STATUS Switch. PROGRM
and PREVIEW cannot be on at the same time.
15 RAMP The TYMGARD provides for the linear ramping of any analog
setpoint. The RAMP switch is used during the programming of
setpoint information and is used to denote that the setpoint will
change from its previous value to its new value in the amount of
time programmed into the step. All ramp steps must have a
previous step in order to be programmed. Ramp allows the
temperature, for example, to be increased at a fixed rate (usually
slower). If a higher temperature is called for without using Ramp,
the temperature will be raised as fast as possible (~ 10°C/minute)
until the setpoint is reached.
16 UNITS The UNITS switch enables the display to show the engineering
units (e.g., typical units for process control) associated with the
various gas and temperature setpoints instead of the values of the
setpoints normally shown. This feature may be used in the
Program and Preview modes and while the display is scanning
during recipe execution. Press the UNIT switch a second time to
revert the display back to showing setpoint values.
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4.0 PROGRAMMING
To enter a recipe into memory, the TYMGARD must be in the Programming mode. Recipe 0
and the twenty-three separate recipes are considered as twenty-four separate program
recipes. Most users will be able to input the desired oxidation or anneal time into the desired
recipe and use it. For special cases, it may be necessary to program a separate recipe.
ALL USER RECIPES MUST BE APPROVED BY LAB MANAGEMENT BEFORE RUNNING
THEM.
The TYMGARD can be placed in the Programming mode by depressing the PROGRM
(Program) Switch followed by a recipe number. There is no code number necessary for our
system. The PROGRM LED will illuminate and the first step of the recipe will be shown on the
display. Only the recipe selected may be edited or input at this time. For instance, if the
TYMGARD is in the Program mode for recipe 2, then only the recipe steps for recipe 2 can be
programmed. Once the TYMGARD is in the Program mode, the output information (recipe)
can be programmed for each step.
The TYMGARD is programmed by setting up each individual step. The next step is followed by
the next, one after the other. This step-by-step programming is continued until the entire
recipe is complete. The last step of the recipe is programmed as Step 0 to distinguish it as the
Abort step, without this step the recipe will not run.
There are ten output relay touch switches called the Contact Closure or Event switches along
the right side of the control panel (see Fig 1). Each of these switches corresponds to an output
relay as labeled on the front panel as previously described.
When programming the TYMGARD, the LEDs, which are illuminated, indicate which event
relay is to be energized for the step being programmed.
The Numerical Entry Keys are used to enter recipe numbers, step numbers, the time interval
for each step, and the setpoint values. The numbers for time are keyed into the display as they
are spoken, in hours, minutes, and seconds.
The ENTER Switch will scroll through the specified setpoint outputs. The existing setpoint
value can be left as it is or the value can be changed by entering a new value. The new value
can also be ramped during the step if the RAMP Switch is pushed just before entering a value.
In the Programming Mode, the beginning of each step is noted by the display as
REC.1 STP.01
For Recipe 1, Step 1, the ENTER Switch must be pushed to start the programming of the step
shown in the display. Optionally, a different step number can be requested by pushing the
appropriate number switches, then pushing the ENTER Switch. (NOTE: To advance to the
next step at any time, press "PROGRM" again.) The time for the step will then be displayed.
Enter the time. The display will show the setpoints. Pushing the ENTER switch will cause the
display to show the next setpoint. After the last setpoint is shown, the first setpoint will be
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displayed again. When the setpoint is shown on the display, it may be changed by pushing the
appropriate number switches. The relay switches may also be pushed to set the relay outputs
that are to be "on" during this step. When Step .01 is complete, step .02 can be reached by
pressing the "PROGRM" Switch.
This programming procedure is repeated until the entire recipe is entered. For the last step, a
zero step is programmed to distinguish it as the Abort step with a time of typically 10 seconds.
Recipe #s 1-14 are reserved for Nanolab standard recipes (Recipe Sheets). They are all
oxidation (dry & wet) steps at temperatures of 850, 900, 950, 1000, 1050 and 1100°C
respectively. The oxidation time is kept variable for each of these recipes so that a user may
simply input this time after choosing the desired recipe and after pressing RUN. These recipes
are pre-approved for any user to run.
Consult the dry or wet oxidation curves in the log book to determine oxide thickness. Userprogrammed
recipes (# 15-23) must be approved by the superuser or lab manager and must
be entered in the recipe section of the log book.
Recipe 0 sets the TYMGARD outputs for the conditions desired when a recipe is not running
(Idle mode). This recipe defines the Idle Mode conditions as previously described. For this
example, the process control recipe is recipe number 3.
5.0 TEMPERATURE:
Temperature is a key parameter for oxide growth. Temperature should be +/- 2° C of setpoint
(preferably +/- 1°C). As long as the AUTO TEMP light is on, the temperature is controlled by
the number input through software. If this light is NOT on, the temperature is controlled by the
3 front panel potentiometers and the Temp1/2 switch. With Temp 1, the upper pots control
and with Temp 2 the lower pots control the temperature. There are 3 pots for each group, with
a 4th pot (extreme leftmost) for overtemp. Do NOT adjust the Overtemp pot. Of the remaining
3, the leftmost is for the front zone, the middle for the center zone and the right for the rear or
source zone. An adjustment of 1 on the center zone corresponds to 1 °C while it takes an
adjustment of 10 on the end zones to change by 1°C. When the deviation meter for each zone
is centered, temperature for that zone is at steady state.
The AUTO TEMP mode should always be used so that the preprogrammed recipes control
the temperature (the previously discussed front panel potentiometers are not used). In addition
to the set temperature, TempC, there are 3 software offsets which must be programmed:
TempL (Load or front zone), Offset2 (center zone) and TempS (source or rear zone). TempL
offset and TempS offset must be programmed in EACH step of EACH recipe and is an
experimentally obtained number. The Offset2 offset must be set during recipe 0 for each
temperature (NOT each step or each recipe). Note: If you are running a standard recipe you
should not have to adjust any offset but if you are running at a different temperature or your
own recipe you must take these offsets into account.. These offsets allow one to compensate
for heat loss at the end zones as well as the extra heat added when the torch is on for wet
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oxidations. Offsets may change slightly from time to time or when the furnace tube is changed.
Consult the log book recipe sheet for latest offsets. Use the preview mode to verify offsets are
correct in the desired recipe. Change them to the log book value if necessary.
When the furnace is opened it is normal for the front zone and center zone to cool off while
the rear zone overheats. Temperature recovery may take up to an hour and these times are
already built into the recipes. Keep in mind that the furnace can be ramped at ~10°C/min while
cooling will be less than 5 °C/min. It is not desirable then to overheat the furnaces.
These furnaces are meant to control between 450-1100°C. Do NOT process outside of
these limits. Additionally, all wet oxide runs must be 800°C - 1100°C.
The center zone should be stabilized (0 on the deviation meter) BEFORE attempting to adjust
the end zones (via TempL or TempS) since the end zones are "slaved" to the center zone.
FURNACE LOADING & UNLOADING:
Although it is possible to incorporate load and unload steps into a recipe, the Nanolab prefers
to Load and Unload from Recipe 0 to avoid any possibility of the furnace being open for
prolonged times. There are 2 quartz boats kept in the tube at all times. For 25 wafers or less,
always use the front boat for best uniformity. (Wafers near the rear will see a higher
temperature during wet oxidations due to the torch temperature.) Dummy wafers are not
required, but a clean bare silicon monitor should be run with your wafers to obtain oxide
thickness. Position of these boats on the cantilever is critical; by using the front boat only and
making sure it just touches the rear boat when you load it, you will guarantee proper boat
placement. Face wafers forward with flats facing up. (Although the process does not require
this, it will help us to troubleshoot problems in the future.) To Load your wafers (after fulfilling
all of the aforementioned requirements):
LOADING:
1 Push PROGRAM button (light comes on), 0, ENTER
2 Verify N2 flow is 3500 cc (3.5L/min); change it if necessary
3 Verify Temperature is 800°C with AUTO TEMP on. Change it if necessary.
4 Verify H2H/O2, H2L/N2, O2 Hi and O2 Lo are off.
5 Verify LOAD light is OFF; push button if it is on.
6 Turn on UNLOAD light by pushing UNLOAD button.
7 Cantilever should slowly come out. The speed is determined by lab management
and should be less than 9 inches/minute. Too fast a speed can result in wafer
warpage or slip.
8 When the cantilever is fully extended, use the steel fork to unload the front quartz
boat onto the quartz sled (the steel bench may be used if the sled is not available).
Do NOT set the hot boat on a wipe or anything else which may melt.
9 Load your cleaned substrates (3 or 4 inch) so that each wafer sits in its own slot and
is perpendicular to the boat. Up to 25 wafers may be loaded in this way. Keep all of
the wafer facing forwards with flats all aligned upwards.
10 Using the steel fork, carefully place the boat back onto the cantilever rods so that it
is in front of and just touches the rear boat. Make sure the boat is centered on the
rods.
11 Turn off UNLOAD by pushing button (you must still be in PROGRAM mode.)
12 Turn on LOAD by pressing LOAD button. Light comes on and cantilever slowly
goes into the furnace tube.
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13 After the cantilever is fully loaded, press "Run" followed by desired Recipe #.
UNLOADING:
1 After finishing your run the alarm will sound. Press the Alarm Acknowledge button
and follow steps 1-12 above to unload your samples and return
system to idle mode. Exit Program mode by pressing STATUS button. Fill out the
Log Book completely and make sure the furnace is in the idle mode with Prgm lite
off.
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