Chapter
5.17
Tystar
17
Low Stress Nitride and High Temperature Oxide
LPCVD Furnace
(Non-MOS)
(tystar17)
1.0
Title
Tystar17 Low Stress Nitride and High Temperature Oxide LPCVD
Furnace (Non-MOS)
2.0
Purpose
Tystar17 is a Non-Mos LPCVD furnace specially designed for
depositing Low Stress Nitride Film, and on a as needed basis for deposition
of High Temperature Oxide (HTO) at
temperatures below 850°C, Stoichiometric nitride (stress > 1000MPa), and
Oxynitride films.
Note; Non-Mos wafers are not allowed in a MOS-clean nitride tube,
Tystar9.
3.0
Scope
This document provides operational
procedures of Tystar17, recipe downloading from FCS10 furnace computer, and
user level troubleshooting.
4.0
Applicable Documents
4.1
Chapter
5.0 of the lab manual (Tystar LPCVD Furnaces).
4.2
TYTAN Furnace System Manual, includes FCS10, TCU, MFS460 (Copy in
Office)
4.3
The “hazardous gas booklet” at the station, which explains the
safety concerns for the specific gases used in Tystar17 (includes MSDS).
4.4
Tystar17
Process Characterization Report.
5.0
Definitions & Process Terminology
5.1
MOS Furnace: This kind of furnaces is used to fabricate of MOS devices (IC),
whose performance can be greatly impacted by trace contaminants. Wafers
processed in MOS clean furnaces should absolutely be MOS compatible (IC
device). Absolutely no metal film in any MOS Furnace, except the MOS sintering
furnace, which allows only Al film.
5.2
Non-MOS Furnace: This kind of furnaces is used for Non-MOS
clean process (Non IC) such as; MEMS or similar application (Tystar 17 is a
Non-Mos furnace).
5.3
LPCVD: Low Pressure Chemical Vapor Deposition.
5.4
Stoichiometric (Standard) Nitride: Chemically
balanced silicon nitride Si3N4 that usually has tensile
film stress over 1000 MPa.
5.5
Low Stress Nitride (LSN) : Silicon rich nitride, which has film
stress around 300 MPa or lower.
5.6
Oxynitride: SiOxNy whose oxygen and nitrogen contents
and the refractive index are determined by the gas flows during deposition
process.
5.7
High Temperature Oxide (HTO): Silicon oxide formed by the
reaction of N2O and DCS. The oxide property is comparable to the
thermal oxidation process, but does not consume the silicon substrate, as the
thermal oxidation does.
6.0
Safety
Follow general safety guidelines in the lab and the specific
safety rules as per follows:
6.1
Tystar17 utilizes high electric power (high amperages)
heating elements. Do not touch high
power electrical part inside panels of the furnace.
6.2
Special care must be taken when the process aborts. In some
special circumstances, the tube may go into “SPECIAL HOLD”. In either case,
inform process staff immediately. The process staff will decide whether the
process can be continued, and/or take proper actions to remedy the situation. Do
not try to open the tube, since there may be toxic hazardous gases in it.
6.3
All new recipes have to be approved by the process staff, before
they can be used on any Tylan or Tystar furnaces.
6.4 Burn Hazard. Furnace cantilevers,
boats, and wafers come out of the furnace are very hot. Wear face shield when loading/unloading
wafers. Proceed with caution.
7.0
Statistical/Process Data
7.1
Microlab web page.
7.2
Problem and comment section under equipment section of the wand.
7.3
Enable message for Tystar17.
8.0
Available Process, Gases, Process Notes
All wafers should be cleaned in clean piranha bath (sink6), and
before they can be loaded into Tystar17 furnace. The only exception to this rule is for
wafers that are just coming out of another Tystar/Tylan furnaces going straight
into this furnace with no delays in between.
Available Processes
8.1
Low Stress Nitride (LSN) Deposition.
8.2
Stoichiometric Nitride Deposition.
8.3
HTO and Oxynitride processes are being developed.
8.4
Please contact process staff for any customized process(es) you
may need.
Available Gases
8.5
Dichlorosilane/DCS (SiH2Cl2): Used as a
source of silicon in all Tystar 17 processes. Decomposition of DCS supplies silicon
for LSN, HTO, Nitride and Oxynitride films.
8.6
Ammonia (NH3): Used as a source of nitrogen in the
nitride process. NH3 is also used post
deposition step to neutralize HCl, which is a byproduct of DCS decomposition.
8.7
Nitrous Oxide (N2O): Used as a source of oxygen for
Oxynitride film deposition.
8.8
Nitrogen (N2): Used for process pressure control, tube
purging, and venting the tube back to atmospheric pressure.
Process Notes
8.9
The maximum temperature for Tystar17 is 850°C. Any attempt to
go above this temperature will result in damaging the O-rings used for the
vacuum sealing.
8.10
The standby temperature for Tystar17 is 650°C. Avoid opening
the tube for more than 30 minutes, which may cause the tube temperature to drop
significantly. In such case, the stress accumulated in the films, deposited on
the tube’s inner wall over the time, may crack the tube.
8.11
All the product wafers processed in Tystar17 should be loaded
facing the back of the furnace (pump direction) for better film uniformity. On
the contrary, all the dummy wafers are loaded facing the door side of the
furnace. This is because the dummy wafers eventually concave towards the
polished side, when the total film deposited on them reach a few micron in thickness. This
arrangement makes it easier to pick dummies on the polished side with a vacuum
wand. It also makes it easier to tell them apart from the product wafers.
8.12
Because the low stress nitride process generates a lot of
particulates in the vacuum plumbing system. During the venting period to bring
the tube pressure to the atmosphere, some particulates may back stream to the
tube and wafers. To minimize this problem, a special shunt device is built into
the gate valve, which allows for small amount of nitrogen flow in the direction
of the pump, hence keeping the particles at the back of the furnace, away from
wafers during venting steps. A pressure gauge is installed to monitor the
performance of the shunt device. This pressure display is located on the lower
panel of the Bank 5 furnaces, above the other two pressure displays assigned to
Tystar19 and 20 furnaces. If the pressure drops below a certain value, the
shunt needs to be serviced. Make sure to report problems, if the reading is
below 4 Torr.
8.13
All Tystar 17 recipes use 4-letter step ID’s, instead of 4-digit
numbers used in the past. The commonly used ID’s are noted below:
IDLE: IDLE state STRT: process StaRT
LOAD: LOAD/unload
wafers BTIN: BoaT moves INto the tube
BPP#: Before
nucleation PumP # BPG#: Before deposition PurGe #
DTEQ: Deposition Temp
EQuilibrium FNH3: start Flowing NH3
FDCS: starts Flowing
DCS DEPO: DEPOsition
PNH3: Post deposition
NH3 Purge APP#: After deposition PumP #
APG#: After deposition
PurG # WAIT: WAIT for user’s action (EVENT)
ABRT: ABoRT sequence SHLD: Special
HoLD
9.0
Overall Furnace Operation
9.1
General Information and Menu Key Pad Explanation
Tystar17 furnace is a five-zone LPCVD
furnace. It operates as a stand-alone unit that comprises of three modules:
wafers load/unload module, furnace/process tube module, and gas control
module. It has it’s own computer,
FCS10, whose display panel and keypad
are located on the left side of the wafer load/unload module. The furnace operation is controlled by using
the special function buttons and a series of menu commands. The furnace
temperature is controlled by the TCU computer board that runs a proprietary PID
algorithm. The temperatures of all 5 furnace zones, i.e. Load, Load/Center,
Center, Source/Center, and Source, can be independently set. The process gases
is controlled by the MFS460 controller that has five hardware interlocks to
insure the safety of the operation.
9.1.1
Front panel special function buttons and keypad description (see Section 11.1 for the
schematics of the front panel):
ABORT: ***USE ONLY IN EMERGENGY***, e.g. fire,
toxic gas leak. DO NOT use this key to abort a recipe in progress. If you must
stop a recipe, please contact a super-user or process staff. They know the
proper procedure for stopping process/evacuating toxic gases from the furnace.
This action requires password, as well.
MENU: Display the main menu (See the Appendix for the description of all menu commands)
NEXT PAGE: Used to display more information/instructions
on the display. Use when prompted, otherwise the computer will freeze and you
will need to find a process staff to reboot it.
CMD: Used for certain special functions.
(Mostly used with GS commands, Section
9.1.2)
Arrow Keys: Used when prompted to select a recipe. Do
not use it as a DEL/BACKSPACE key when entering alphanumerical inputs.
Otherwise the computer will freeze and you will need to find a process staff to
reboot it.
Alpha-
Numeric Keys:
Used to enter process parameters, e.g. gas flows, pressure, deposition time,
and etc.
ENTER: Used to enter the menu command or
alphanumerical inputs.
CLEAR: Used to clear the error on the
alphanumerical key input.
RUN: Run the recipe loaded in the
computer memory.
HOLD: Hold a recipe step at its present
process condition. Press RUN to resume the process.
EVENT: Acknowledge the process to go to
the next step of the recipe when the current step time has not finished yet.
e.g. after you finish loading the wafers and want to close the furnace door.
Some of the process step cannot be EVENTed.
BOAT IN/OUT: Move the boats in/out of the process tube
manually, independent of the recipe. These are toggle switches, i.e. push once to
turn on and the second time to turn off. If both are ON at the same time, then
the boats stop moving.
ALARM ACK: Silences an alarm, but does not correct the
alarm condition. Alarm conditions are displayed on the bottom line of the
screen. In most cases, the computer will clear the alarm conditions by itself.
If not, report the problem on the WAND.
9.1.2
Commonly used MENU commands (press MENU button, then enter the two
letter commands):
DS Displays the current status of the
furnace. An example is shown in Section
11.2.
DH Displays the process history from the
last time the RUN button was pressed to present time.
DR Displays the contents of the
selected recipe.
GS Changes the Display to graphic mode. It
shows large characters with only selected process information. Use CMD button
to select process parameters to be displayed.
RL Loads process recipes. You will be
prompted to use the Arrow Keys to select a recipe. Afterward, press ENTER
button twice. The computer will prompt you to enter process parameters, if/when
needed.
9.1.3
Process Gas Flow Interlocks
When any of the following five interlocks
turns ON, no process gas, except nitrogen, will flow. If the ANTLK is on, the
nitrogen cannot flow either.
DNTLK Door interlock. When ON, it indicates that
the tube door is not closed properly.
ANTLK Above atmosphere pressure interlock. When
ON, the tube pressure is above 760 Torr.
BNTLK Below process pressure interlock. When ON,
the process pressure is above 2 Torr.
VNTLK Vacuum interlock. When ON, it indicates that
the vacuum system is not working.
GNTLK Gate interlock. When ON, the gate valve
between the vacuum pump and process tube is closed.
9.2
Available Recipes
There are four process recipes available on this furnace. A staff or
super users should be consulted whenever a new recipe is needed. The John
Goldman computer is used for setting up new recipes. No one should ever upload
a recipe from the menu driven terminal to John Goldman computer.
9.2.1
STANDBYA.017: Standby recipe. It purges a small amount
of nitrogen through the process tube at low pressure to keep it clean.
9.2.2
LSNSTDA.017: Standard Low Stress Nitride LPCVD. The deposition condition is
fixed (100DCS/25NH3/140mTorr/835°C). Enter only the deposition time, based on your target
film thickness, when loading recipe.
9.2.3
LSNVARA.017: Variable Low Stress Nitride LPCVD. The process gas flows and
pressure are specified by the user, while the temperature is fixed at 835°C. The recommended DCS
flow is 100sccm, and you can reduce the NH3 flow to obtain lower stress in the
film.
9.2.4
STDNITA.017: Stoichiometric Nitride LPCVD. The process condition is fixed
(25DCS/75NH3/300mTorr/800°C). The stress can reach above 1000MPa.
9.3
Processing a Run (Loading Recipe and Wafers)
Venting the Tube
Tystar17, as well as all other LPCVD furnaces, runs STANDBY recipe
when in idle. The tube is under low pressure and needs to be properly vented
before you can open the door to load/unload wafers. If the tube is not vented,
the tube door is under atmosphere pressure force, which could be over a few
hundred pounds. Do not run any process recipes or try to open the tube door
manually in this case. It will severely damage the furnace.
9.3.1
Enable TYSTAR17 on the WAND.
9.3.2
Make sure the “STANDBYA.017” is running, and the process is at
WAIT step. If the VNTLK is ON, do not run any process, since there is a problem
with the vacuum pump system. Report on WAND.
9.3.3
Press “EVENT”, and the process should advance to BKF1 (Back Fill
#1). It takes 12 minutes for the venting process to finish. Afterwards, the
process ends and the furnace status changes to IDLE mode.
9.3.4
Check the SHUNT pressure on the lower display panel. If the
pressure is below 4 Torr, report on the WAND. In this case, the SHUNT flow may
not be sufficient to prevent the particulates back-stream from the pumping
system to the process tube
Load and Run a Process Recipe
9.3.5
Make sure the process tube is properly vented.
9.3.6
Press MENU button, then enter RL and the screen will show a list
of the available recipes. Use the arrow keys to highlight the recipe that you
plan to load, then press ENTER twice.
9.3.7
The computer will prompt you to enter some process parameters if
needed. Input values of previous run will be displayed for your reference. You
have to enter your value with the same format even if it is same as what is
displayed. Press ENTER after typing each process variable value.
9.3.8
Use the CLEAR key if you need to erase a wrong value,
entered. DO NOT USE THE ARROW KEY TO
MOVE THE CURSOR! This will cause the software to crash and all the recipes
might be lost.
9.3.9
Time is entered in the format of HH.MM.SS. Do not enter “00.00.00”
since it hold the process at the step indefinitely.
9.3.10
Once you have finished entering all of your required values, press
MENUE, then DS to check that the recipe is loaded properly. Press RUN to start
the process. The tube door will open and boats come out.
9.3.11 Put on the face
shield. After the boats move out completely, remove dummy wafers and load your
wafers. The boats will remain out for 20 minutes. If the boat start moving in
and you have not finish loading your wafers, press EVENT before the door
closes, the boat will come out, and you have another 20 minutes.
*** Do not leave the door open for more
than 30 minutes, since it will create a large temperature gradient in the tube
and causes the thick film deposited on the tube wall crack and create
particulate problems. This may also crack the process tube.
In the case that a wafer is broken when
loading, and you need to obtain another clean one, press HOLD then BOATIN. After
you are ready to load again, press BOATOUT and wait for the boat to come out.
Load your wafer, then press RUN and proceed to the following section.
9.3.12
Press EVENT, and boats will start moving into the tube. When the
door closes completely, the tube will be pumped down and the deposition process
start.
9.3.13
If the deposition process successfully complete, it will hold at
HLD1 step and the tube is gets continuously purged with nitrogen and held at
low pressure (650ºC). Press EVENT to start the venting process.
9.3.14
After 12 minutes, the process holds at HLD2 step. Check the SHUNT
pressure following Section 9.3.4.
9.3.15
Press EVENT and the tube door will open and boats will come out.
Repeat Section 9.3.11
to unload your wafers and reload the dummies.
9.3.16
Press EVENT again, and boats will start moving into the tube. When
the door closes completely, the recipe ends. Press ALARMACK to silent the
alarm.
Load and Run the Standby Recipe
9.3.17
Press MENU, then enter RL. Use the arrow keys to highlight the
standby recipe. Press ENTER twice.
9.3.18
Press MENU, then enter DS. Check and make sure that the recipe is
loaded.
9.3.19
Press RUN. You should wait and monitor the furnace until all the
interlocks turn OFF. Disable TYSTAR17 on the WAND when you are done.
9.4
Special Instruction for Processing 6” Wafers
9.4.1
There is only one 6” boat, which can hold 12 wafers, in Tystar17.
Find the 6” dummy wafer box, which is located between Sink 7 & 9. Pick out
certain number of dummies so that the total number of wafers (yours and
dummies) is 12. Clean the dummies with your wafers in Sink9.
9.4.2
Load and start your process per Section 9.3.
9.4.3
The 6” boat is located on the front (toward the door) of the 4”
boats. Load all 12 wafers (your wafers and the dummies) into every other slots
of the boat. Do not use the slots on both ends.
9.4.4
Remove all 12 wafers after your process is done. Place the dummies
back into the same dummy wafer box. If the film on the dummies starts peeling,
report on WAND and the process staff will rework them.
10.0
Troubleshooting Guidelines
10.1
The tube is at atmospheric pressure hold (step HLD2). In this
case, there is no film deposition on your wafers.
10.1.1 Cause: The tube door has not closed properly
(DNTLK is ON).
Solution: Make sure there is nothing on the track
blocking the movement of the boats.
Press EVENT three times (The boats will
move out, then in, and the process end).
Run the process again. Press EVENT twice
and the door will start moving in.
If the DNTLK is still ON when recipe reaches BPP1, the system
needs to be checked. Report the problem on WAND.
10.1.2 Cause: The tube failed leak check. (no
interlock is ON)
Solution: Press EVENT three times (The boats will
move out, then in, and the process end).
Run the process again. When the tube door is completely open,
check the door flange and tube’s open-end area for any debris that may result
in leakage. Wipe the flange with Technicloth. To prevent burn injury, pay extra
attention on the hot spots of the boat loader when doing so.
10.2
The tube is at abort hold (step APRG). In this case, the process
was aborted when the process gases were flowing. There is some film deposition
on your wafers.
10.2.1 Cause: One of the process gas flows was out of
tolerance due to delivery system malfunction or gas cylinder getting empty.
Solution: Press MENU, then enter DH. Press ENTER when
prompted for input. The whole process history for this run will be displayed.
Find the root cause for the abort and report on the WAND.
10.2.2 Cause: You
have not enabled the furnace. In this case, find a staff to restart the
process.
10.3
The tube is at special hold (step SHLD).
10.3.1 Cause: When
the process hold at SHLD, it indicates some serious system problem occurred, e.g.
pump failure, tube leakage, while process gases were flowing in the tube.
Solution: Report on the WAND or find a staff
immediately. Do not attempt to fix the situation yourself (including
super-users).
10.4
The door won’t open after the venting
10.4.1 Cause: BOATIN is ON. Someone pressed the button
by mistake.
Solution: Press BOATIN to turn it OFF. Make sure
BOATOUT is ON.
10.4.2
Cause: System malfunction.
Boat loader has problem.
Solution: Report on WAND.
10.4.3
Cause: No nitrogen flow,
and the tube is not vented. On the display, N2 actual is 0, instead of 5000.
Solution: Report on WAND.
10.5
The FCS10 computer does not respond to the keypad input (Computer
Crashed)
10.5.1 Cause: Use the Arrow Keys instead of the CLEAR
to erase the error, when enter, an alphanumeric inputs.
Solution: Report on WAND.
10.5.2 Cause: Press NEXTPAGE twice when loading a
recipe that requires multi-pages of inputs. Usually, this is caused by the old
keypads, not by the user.
Solution: Report on WAND.
11.0
Figures &Schematics
11.1
Front Control Panel of the FCS10 Furnace Computer
11.2
Furnace Status Displayed on the FCS10 Front Panel (Idle state of
the standby recipe)
FNC: DS – Display Process Status STANDBYA.017
MODE: RUN END:
00.00.00 STEP: IDLE ST_TTG: 00.00.00
|
SETPT |
ACTUAL |
SIGNAL |
SETPT |
ACTUAL |
SIGNAL |
SETPT |
SIGNAL |
ACTUAL |
|
|
N2 DCS NH3 N2O N2VAC PRCPR GATEVLV LEAKCHK |
5000 G 0 G 0 G 0 G 0 G 0 H OFF OFF |
5000 0 0 0 0 2079 OFF OFF |
TEMPL TEMPLC TEMPC TEMPPSC TEMPS RMPRATE TCUENA TCUID BOATSPD |
300.0 G 300.0 G 300.0 G 300.0 |