5.2
DELAY Step
The delay step is any period during the cycle when
the lamps in the oven are off and purge gas is flowing through the system.
Delays are used most frequently at the beginning of a cycle, after the door
closes, and at the end of the cycle, just before the door opens. A simple cycle
is usually programmed with two delay steps. The initial delay is used to purge
the heating chamber before wafer heating begins. The second delay step allows
time for the wafer to cool in an inert environment before the robot removes it
from the oven. For each delay step the operator can specify the duration from 0
-6000 seconds, the amount of purge gas flow, and the purge line to be used.
5.3
RAMP Step
The
programmed ramp step is the period of time during the cycle when temperature is
rising or falling from one steady temperature condition to another. This
illustrates two programmed ramp steps: One ramp-up step, as wafer temperature
approaches steady state, and another ramp-down step, at the end of the steady
state period. The ramp step may be programmed from 0 to 200°C. For each
programmed ramp step the operator can specify the ramp speed, in degrees per
second, and the final temperature at the end of the ramp. Purge gas flow and
the desired purge line can also be specified.
5.4
STEADY Step
The third type of the step is the steady step, which the wafer
temperature is kept constant for a specified period of time. This step must be
included for anneal processes ≥ 800ºC, which cannot easily be controlled
without a preheat step (STEADY STEP).
Therefore, use a 30 second preheat step at 450ºC before ramping up to
your final anneal temperature/s (≥ 800ºC). Programmable parameters for the steady state step include the
steady state temperature and the duration of the steady state period. Steady
state temperature may be programmed from 0-1400ºC. Steady state time may be programmed from 0-6000 seconds. In order
to enhance heating uniformity, the gas flow should not exceed 20 mm during the
steady state period.
5.5
FINISH Step
The fourth type of the
step is the finish step, which is the last step of the process. This step is to
stop the process. The operator can specify the purge gas flow on and off after
process finished. Finish state time is always 0.
Any process recipe
can be divided into three basic components or steps: the DELAY step, the RAMP step and the STEADY
state step.
6.0
Safety
Heatpulse
6.1
Do not operate the tool at temperatures above 850ºC (recommended
maximum process temperature, ≤ 800ºC).
6.2
Do not exceed 800ºC anneals without permission on heatpulse1.
6.3
Do not touch chamber wall or process wafers that have just been
unloaded from the chamber, as they will be at elevated temperatures. The
standby temperature is at around 200ºC; hence process wafers are hot and can
burn you.
6.4
Do not use the system if chamber wall temperature (default 15ºC)
is higher than set point. Cooling water will have to be refilled before system
can be used.
6.5
AG Heatpulse is a cold-wall system, where only the sample and the
filaments reach an elevated temperature; the thermocouple must be attached to a
test wafer.
7.0
Statistical/ Process Data
7.1
Problem and comment section under equipment section of the wand.
7.2
Enable message for heatpulse1.
8.0
Available Processes, Gases, Process Notes
8.1
General Information
8.1.1
For anneal process temperatures ≥ 800ºC, make sure to
include a 30 second preheat step at 450ºC.
8.1.2
Run at least 2 dummy runs to get consistent temperature control
whenever process temperature is changed. Heatpulse temperature control
algorithm learns and optimizes PID constants and stores them.
8.1.3
Before processing, purge chamber for a minimum of 3 minutes at 50
mm with process gas. Reduce flow to a minimum of 20 mm during process. This
prevents thermocouple (TC) failures.
8.1.4
Annealing temperature range is 300ºC to 800ºC and time is limited
to 180 sec. If longer anneal time is
needed, allow chamber to cool down first and then repeat the process.
8.1.5
Process gases available – Ar, N2, O2, N2/H2.
8.1.6
Users who wish to use the programming features for more
complicated anneal profiles should read the manual and talk to the Superuser.
Furthermore, since this machine is used for very different purposes, check with
the Superuser to make sure that your usage will not adversely affect any other
research.
8.1.7
Heatpulse1 is for a general anneal processing tool that includes
GaAs processing. PZT material must be processed in their own dedicated PZT
chamber. Any materials or processes
that may contaminate these tubes will require the user to purchase his/her own
annealing tube. Refer to Appendix A.2, if you need the anneal
chamber tube changed.
8.1.8
Two thermocouple styles
are available:
1) A T shaped thermocouple, which is held by
fused silica posts on the wafer tray and located in close proximity to a
4" wafer.
2)
A 4" SensArray brand wafer with
imbedded thermocouple which holds small samples and die.
Thermocouple
lifetimes are greatly reduced at high temperatures in an O2
atmosphere. Microlab policy requires lab members who want to anneal above
1050ºC in O2 purchase their own thermocouples from the office and to
be trained on how to install their tc. A request for training should be sent
to: heatpulse1 at silicon.eecs.berkeley.edu.
8.1.9
For accurate control and monitor of the sample temperature,
thermocouple located inside the annealing chamber is hooked via a feedback loop
to the controller, and the computer provides a soft copy of the temperature
profi1e.
8.1.10
DO NOT anneal aluminum at temperatures above 450ºC in any chamber.
8.1.11
There are two chamber
setups available for heatpulse1 (GaAs and PZT chambers), each consisting of a
fused silica chamber, a fused silica paddle and a K-type thermocouple attached
to a slice of silicon. The silicon chamber is reserved for MOS processing,
silicon material such as SiO2, Si3N4, and
LPCVD furnace films. The PZT chamber is reserved for a piezoelectric material,
Pb zirconate titanate, and other materials, which may exhibit a high vapor
pressure. These two setups are changed by staff at the request of qualified
heatpulse1 users. To request a chamber change e-mail heatpulse1 at
silicon.eecs.berkeley.edu and state which chamber is needed. See Appendix A.2 for more details.
8.1.12
Gas flows are
controlled with a rotometer (glass tube with float) and needle valve. Adjust the
gas flow between 20 mm to 30 mm. A second rotometer is used in the exhaust of
heatpulse1. It should not be adjusted and is used to confirm that the chamber
is properly sealed and not leaking, i.e. gas in = gas out.
9.0
Equipment Operation
9.1
Procedure on Heatpulse Front Panel Control
9.1.1
Enable Heatpulse1 on the wand and check if system POWER switch is
on.
9.1.2
The LAMP CONTROL should be in the Automatic Mode for normal
operation. The Manual Mode is used only for non-standard anneal profiles, when
heating is controlled by the two lamp intensity potentiometers (the inner knob
controls the upper bank and the outer knob controls the lower bank).
9.1.3
Turn on the appropriate gas with the manifold controls below the
Heatpulse.
9.1.4
Set the METER - SELECT to off. The readout now shows temperature
(ignore the decimal). The temperature reading 20.0ºC is actually 20º.
9.1.5
Open the chamber by loosens the two knobs on the door and swings
the arms straight down. Gently pull the door most of the way out. Place your
sample in the 3 throngs of the quartz tray in the chamber and close the door,
resealing carefully (don't force the knobs). If the thermocouple fails due to
O2 contamination, you will be required to buy a new thermocouple.
9.1.6
Adjust the flow meter on the Heatpulse to approximately 50 mm for
3 minutes to reduce atmospheric (slight positive pressure) contamination from
the process chamber (it is necessary to run this procedure).
9.2
Running the RTP with the PC control (single wafer chamber)
9.2.1
Make sure the PC and the PC integrated process control system
is on.
9.2.2
Adjust the process gas to 20 mm, can be as high as 30 mm.
9.2.3
Press Process for
engineer button on the main menu.
9.2.4
Input the lot ID in the Lot-ID dialog box.
9.2.5
Select the desire recipe for alloying or annealing.
9.2.6
Loosen two screws and lower both lever arms until they are
straight down. Carefully pull the chamber door out until you see most of the
quartz tray.
9.2.7
Load a dummy wafer on the quartz tray.
9.2.8
Push the chamber door in and make sure the quartz tray is
all the way in. Do not push hard on
the quartz tray. It is fragile. Raise the lever arms and tighten both
screws to lock the door.
9.2.9
Press START PROCESS button to begin the process.
Check the gas flow and see if it is still at your desire reading on the flow
meter. Readjust it if needed.
9.2.10 When the
system activates the alarm dialog at the completion of the cycle, press OK
button on the screen to deactivate the alarm. You can also exit when the graph
shows the alloying or annealing process is finish.
9.2.11 When finished
the process, wait until temperature is lower than 200°C and then
press SAVE EXIT or STOP NOT SAVE Button.
9.2.12 Repeat step
9.2.8 to 9.2.10 until the PC shows the final STEADY step on the alloying or
annealing process is satisfy. Thermocouple located inside the annealing chamber is hooked via a
feedback loop to the controller, and the computer provides a soft copy of this
temperature profi1e.
9.2.13 Loosen two
screws and lower both lever arms until they are straight down. Carefully pull
the chamber door out until you see most of the wafer.
9.2.14 Unload the
wafer.
9.2.15 Repeat 9.2.6
to 9.2.13 to process another dummy wafer and then repeat to process the actual
wafer.
9.2.16 Push the
chamber door in and make sure the quartz tray is all the way in. Do not push hard on the quartz tray.
It is fragile. Raise the lever arms and tighten both screws to lock the door.
9.2.17 Exit to the
main menu and the program will automatically turn off the cooling air after 5
minutes.
9.2.18 Turn off the
process gas on the flow meter.
9.2.19 Turn off the
process gas
on the manifold controller below the Heatpulse.
9.2.20 Finally, disable
the Heatpulse on the wand.
9.3
Creating
Recipes
9.3.1
Press Recipe
button from the Main Menu. The Recipe Manage Screen will appear.
9.3.2
Select the recipe to
be edited from the file list or type a new recipe name (this will create a new
recipe) in the dialog box.
9.3.3
Press Recipe Edit
to go to the Recipe Edit Screen where recipes can be modified.
9.3.4
Select wafer type: (1) wafer or (2) susceptor.
9.3.5
Fill the engineer name and title (process description) in
each dialog.
9.3.6
Use up arrow key, down arrow key, or mouse to move to the
desire step. Or begin with step 1 to define the recipe step by step. Commands
on the bottom of the screen are self-explanatory.
9.3.7
Move to Step Function column. Press R/S/D/F and then ESC to change the step function (Ramp, Steady,
Delay and Finish).
9.3.8
Move to Time
column to specify the time, in seconds for the delay, ramp and steady steps.
9.3.9
Click Temp column
to enter the steady state temperature. When the ramp step is selected, this
button is used to specify the target temperature when the steady state step
begins. Enter temperature value 0 on the delay step.
9.3.10 Move to Gas1
N2 column. Currently there are no MFC for controlling the process gas. Only
Gas1 N2 column can be selected. Put any number between 1 and 30 will turn on
the gas. 0 will turn off the gas on this step during the process.
9.3.11 Repeat from
9.3.7 – 9.3.10 for multiple step recipes.
9.3.12 Press F10 or Recipe Validate and click OK to validate the recipe.
9.3.13 Press F8 or
Recipe Graph button to look at the
recipe in graph mode, then click Exit.
9.3.14
Press F2 or Save to save the validated recipe.
9.3.15
Press Exit and Exit
again to return to the Main Menu.
Note: The maximum
of the recipe steps limited to 80 steps.
10.0
Troubleshooting Guidelines
10.1
If the temperature overshoot or undershoot for more than 5°C at
the Steady State Period, press Abort button to interrupt the cycle.
Contact maintenance staff and report it on Faults. Do not process further until
the maintenance staff checks it out.
10.2
If the Heatpulse and computer system is off. Turn on the computer
first and wait until the RTA program main menu displays on the computer screen.
Switch on the power on the front panel on the Heatpulse. Switch on the gas
control box power below the Heatpulse. Press Diagnostics button to check
if the system works properly. If it doesn’t, contact the maintenance staff and
report on FAULTS.
11.0
Figures & Schematics
12.0
Appendices
Appendix A
A.1 Changing
the Thermocouple
The thermocouples are both extremely
fragile and very expensive. BE GENTLE with them. Check with the staff if
the thermocouple fails, which generally means the leads have broken and must be
replaced. The thermocouple shall be changed by staff ONLY. Report a
thermocouple failure on faults.
A.2 Changing the Annealing Tube
The annealing tube can
ONLY be changed by the staff. Chamber changes are limited to 2 times/week. The
current setup for heatpulse1 can be verified using the WAND. Type e for Equipment
in the Category window; tab to go to the Tasks window; type E for Read
enable message. When prompted, enter the equipment name (heatpulse1). Check
the current chamber set up: it is shown under the Enable message. Send an
e-mail to heatpulse1, if you need a different tube installed. Report a system
problem on faults.
.A.3 Equipment Information
A.3.1 This
annealing furnace contains 13 high-intensity tungsten-halogen lamps, which are
arranged in upper and lower banks (6 and 7 bulbs, respectively) and housed in
water-cooled, reflective walls. A quartz annealing tube is positioned between
the banks, and is hermetically sealed to the door with an O-ring. flat piece of
quartz attached to the door holds the wafer and allows sample loading into the
isolated annealing chamber. The visible light from the continuous-wave (CW)
lamps passes through the quartz annealing tube and wafer tray and is absorbed
by the sample.
A.3.2 Each
of the thirteen bulbs produces 1.5 kW lamps, and at 100% intensity the computer
limits the input power to 18 kW lamps. The high-intensity of the lamps heats
the sample quickly. Operating range is 200ºC to 800ºC. Times are limited to 180
seconds. The anneal profile can be controlled by either sample temperature or
lamp intensity.
Appendix B
Heatpulse
Alloying and Annealing Recipes
B.1 Alloying
Recipe (Recipe #1)
|
Step
|
R/S/D Chosen
|
Temperature (°C)
|
Time (sec)
|
|
1
|
Delay
|
0
|
100
|
|
2
|
Ramp
|
250
|
30
|
|
3
|
Steady
|
250
|
30
|
|
4
|
Ramp
|
410
|
30
|
|
5
|
Steady
|
410
|
30
|
|
6
|
Delay
|
100
|
170
|
|
7
|
Finish
|
100
|
0
|
B.2 Annealing
Recipe (Recipe #2)
|
Step
|
R/S/D Chosen
|
Temperature (°C)
|
Time (sec)
|
|
1
|
Delay
|
0
|
100
|
|
2
|
Ramp
|
450
|
30
|
|
3
|
Steady
|
450
|
30
|
|
4
|
Ramp
|
900
|
30
|
|
5
|
Steady
|
900
|
30
|
|
6
|
Delay
|
100
|
240
|
|
7
|
Finish
|
100
|
0
|
