standard operating manual - hong kong university of

NANOSYSTEM FABRICATION FACILITY (NFF), HKUST

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Standard Operating Manual ___________________________________________________________

STS ICP Compound Semiconductor Etcher


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Contents

1. Picture and Location

2. Process Capabilities

2.1 Cleanliness Standard

2.2 Possible Etching Materials

2.3 Process Specification

3. Contact List and How to Become a Qualified User

3.1 Emergency Responses and Communications

3.2 Training to Become a Qualified User

4 Operating Procedures

4.1 System Description

4.2 Safety Warnings

4.3 Operation Precautions and Rules

4.4 Initial Status Checks

4.5 Initial System Checks

4.6 Preparation before Etching

4.7 Recipe Selection

4.8 During the Run

4.9 Process Recording during the Process

4.10 Clean up

4.11 Check out


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1. Picture and Location

Fig. 1: STS ICP Compound Semiconductor Etcher

This tool is located at NFF Phase II Room 2240.

2. Process Capabilities

2.1 Cleanliness Standard

STS ICP compound semiconductor etcher is classified as Non-Standard equipment

2.2 Possible Etching Materials

1. GaN


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2. Sapphire

3. III-V semiconductor

4. Silicon

2.3 Process Specification

What the STS ICP compound semiconductor etcher CAN do

Sapphire, GaN and III-V compound semiconductor material of,

1. 2 inches full substrate

2. Small samples

All the substrate or samples should be placed on a specific 6” top plate for etching

What the STS ICP compound semiconductor etcher CANNOT do

1. Substrate larger than 2 inches in diameter

2. Tiny samples that can be blow away.

3. Dirty samples that will contaminate the top plate

4. Metal film etching

3. Contact List and How to Become a User

3.1 Emergency Responses and Communications

In case of emergency issues, please contact NFF staffs,

1. Preason Lee – Deputy Safety office (x7900),

2. CK Wong – senior technician (x7226)

In case of technical help, please contact NFF staffs,


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1. CK Wong – senior technician (x7896)

2. Casper Chung –technician (x7896)

3. Brial Kwok – technician (x7896)

3.2 Training to Become a Qualified ICP compound semiconductor User

Please follow the procedures below to become a qualified user:

1. Read all materials provided on the NFF website of the ICP compound

semiconductor etcher.

2. E-mail to NFF requesting ICP compound semiconductor operation training.

4. Operating Procedures

4.1 System Description

The STS ICP system is used to etch GaN, sapphire, III-V compound semiconductor

material, which offer anisotropic etch with low undercut.

The ICP system uses inductive coupled design, so high density plasma can be formed in

the process chamber, this in return capable for III-V compound semiconductor material

etching. Cl2 and BCl3 gases are used for the etching, and He gas is used for backside

cooling to ensure better control of the etch rate, selectivity and profile.

4.2 Safety Warnings

1. If the equipment failure while being used, never try to fix the problem by

yourself, please contact NFF etching module staffs


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2. In emergency, please push any one of the red emergency buttons (Fig. 2) to

interrupt the equipment power, and report to the NFF staffs immediately. DO

NOT attempt to resume the equipment on before the problem is solved.

3. If something going wrong during process and you are not sure what happened,

please check and write down the alarm/warning message and report to NFF

etching module staffs. Alarm/warning message will be displayed at the bottom of

the display (Fig.3). DO NOT attempt to resume the equipment on before the

alarm/warning message is verified.

Fig. 2: Emergency button Fig.3: Alarm/Warning message

4.3 Operation Precautions and Rules

1. Please reserve the time slot on your own, and make sure you use your own time

slot to do the etching process.

2. The system can be reserve from Monday to Friday, 9:00~18:00

3. Reservation will be forfeited if the user has not show up for 10 minutes and it

may cause $200 penalty.

4. Do not operate the equipment unless you are properly trained and approved by

NFF staffs


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5. Please fill all the details of the log-sheet attached, i.e. date, name, project number,

email, project details, material to be etch…

6. Do not leave an on-going etching process unattended

7. Do not skip any cycle purge steps during the process

8. Do not change details of the recipe, if you need to start a new recipe, please

consult NFF etching module staffs

4.4 Initial Status checks

1. Please check the status of ICP Compound semiconductor etcher shutdown notice

posted in the NFF reservation website.

2. According to the reserved time slot, please check-in the equipment on your own

3. After check-in the equipment, please check correct name and project number that

printed on the etching module LCD screen (Fig. 4).

4. If you failed to check in the machine, there is an interlock, and you cannot

operate the machine.

5. Before operate the machine, please make sure you have read and fill the details

of the check list.


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Fig.4: Reservation and Equipment check-in status LCD

4.5 Initial system checks

- Make sure the system is logged in STANDARD mode.

- Make sure there is no alarm/warning message is given out at the bottom of the display.

- Check the equipment is ready (Fig. 5) for the etching process in the main PC screen:

1. DP (dry pump) is turned ON

2. TB (turbo pump) is turned ON

3. GV (High vacuum gate valve) is OPEN

4. MP (load lock mechanical pump) is turned ON


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- Check any wafer left in the chamber or load lock chamber

If you have any questions on the above procedures, please contact module staffs for help.

Fig. 5: Process screen with equipment status

4.6 Preparation before Etching

You are advised to do the following steps before start do the etching process.

1. Confirm the gases involves in the etching process, this is because CH4 and SF6

gases share the same gas pipe. There is a label indicates the gas pipe is currently

occupied by CH4 or SF6 (Fig. 6). If you need to swap between CH4 and SF6,

please consult NFF staff.

2. Make sure the shutoff valves of the Cl2 and BCl3 gas delivery system are opened,


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so that the gas can be delivered to the system.

3. Check the cooling chiller located behind the main console is ON, and default

temperature is 20oC (Fig. 7)

4. Clean the back side of carrier top plate with IPA (Fig.8).

5. Perform a 10-20 minutes “O2 Clean” process before etching process.

Fig. 6: CH4/ SF6 gas usage indicator

Fig.7: Cooling Chiller Fig.8: Carrier top plate

4.7 Recipe Selection

Please make sure you select a right recipe, using wrong recipe may get unexpected

results. Please read the following Recipe Loading procedures:


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1. Click on the RECIPE button in the PC Process Control Window (Fig. 5), then the

recipe menu will be displayed (Fig. 9)

2. Check the recipe name you need. If not, click on the OPEN button, and select the

right recipe from the pull down menu (Fig. 10).

Fig.9: Recipe Menu Fig.10: Open Recipe

3. In the recipe menu, click on the etching step (Fig.11), then there are few pages of

parameters, please confirm all the parameters including etch time, pressure, gas

flow and RF power are correct:

i. General page: Only Process time is allowed to change (Fig. 11)

Fig. 11: Recipe General Page

ii. Pressure page: Check the process pressure set point. Sometimes, it is


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represents in percentage of valve opening angle (APC%). If you need to

change the pressure, please consult module staffs. (Fig. 12)

Fig. 12: Recipe Pressure Page

iii. Gases flow page: Check the gases flow are correct. If you need to change

the gases flow, please consult module staffs (Fig.13). However, illegal gases

combination will cause series damage to the equipment and personnel, e.g.

CH4 gas is prohibited when O2 gas is introduced (Fig. 14).

Fig. 13: Recipe Gases flow page Fig.14: Illegal gases combination

iv. RF page: Check the RF power set point. If you need to change the power,

please consult module staffs. (Fig. 15)


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Fig.15: Recipe RF power page

4. After set the etching time, confirm all the parameters are correct, then save and

quit this menu.

5. Back to the PC Process Control Window, click on the SELECT button, select the

recipe (Fig. 5) just saved, and the data will be loaded into the memory for

etching process.

6. Confirm the recipe is loaded into the memory (Fig. 5)

7. If the recipe you want to use is not listed in the menu, please consult NFF

module staffs.

Also, user has their own responsibility to record all the details parameters of recipe; we

will not provide you data-log check services.

4.8 Process Run

There are two methods to run the process, 1) manually, and 2) automatically.


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1) Manual Operation

Manual operation involves the following steps:

i) load lock chamber vent

ii) set substrate

iii) pump down and wafer loading

iv) run etching recipe

v) wafer unloading and load lock vent

i) Load lock chamber vent: Verify the Load-lock chamber is in vacuum or not. If the

chamber is in vacuum, click the VENT button in PC Transfer Window (Fig.16). During

venting, a chamber releasing warning message will be display at the bottom of the

screen (Fig 17).

Fig. 16: Manual operation in Transfer Window


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Fig.17: Chamber releasing message

ii) Set substrate: place substrate or samples on the carrier plate, and set the plate on the

load lock arm (Fig. 18).

Fig.18: Set substrate and carrier plate

iii) Pump down and wafer loading: Close the Load-lock chamber door gently after set

your samples and plate. In the PC Transfer Window, click on the Next Carousel text

bar (Fig.16), and type in simple lot name, i.e. project no. Then, press the


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PUMP+MAP button (Fig. 16). Make sure the chamber door was correctly closed;

otherwise the load lock chamber can not be pump down. Wait a few minutes to

evacuate the load lock chamber. When the crossover pressure reached, then click on

the LOAD button, and load lock arm will send the carrier plate into process chamber.

Then, carrier plate sits at the center of process chamber and the clamp down. Finally,

load lock gate valve will be closed, and process chamber will pump down to base

pressure.

iv) Run etching recipe: Normally, an etching recipe includes a few steps:

1) Waiting for base pressure: chamber pressure must be pump down to 0mTorr before

proceed to the next step, readout can be observed from the VAT controller display

(Fig. 19)

Fig.19: Chamber pressure readout


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2) Helium leak up rate check: In order to control the substrate temperature during

etching, Helium gas is introduced to the backside of the carrier plate. Then

mechanical wafer clamp is use to force the carrier plate to the O-ring mounted on the

electrode, so the helium pressure can be keep at specific pressure designed in recipe.

Typically, helium leak up rate displayed cannot exceed 30mTorr/min; otherwise the

process will be halted at this step (Fig. 20)

Fig.20: Helium leak up rate test

3) Waiting for Match: matching unit will move to the pre-set position designed in

recipe.

4) Gas Stabilization: different gas channels will deliver stable gas to the chamber.

5) Etching: RF power will be given, and RF matching unit start to match the impedance

inside the chamber. Effective RF matching can minimize the reflected power, and

increase the forward power until it reached the set point, then plasma ignite, and you

can observed the plasma light through the side viewports and in the PC screen (Fig.

21)


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Fig. 21: Plasma ignite

6) Pump out and Cycle purges: after etching process, chamber must be pump down to

base pressure, and then a series of cycle purge will be carry out in order to remove the

residue gas/hazard gas remain in the chamber.

However, during the etching process, all the etching parameters can be obtained

through the display screen. Also, in the PC Process Control Window, “SKIP/ABORT”

function keys can be used to skip or terminate the process during the run.

V) Wafer Unloading and Load lock Vent

Once the cycle purges completed, click the UNLOAD button to unload the carrier plate

back to the load lock chamber. After the carrier plate is successfully unloaded and the

gate door fully close, click VENT button to vent the chamber. The load lock chamber


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door will be release around 1minute (Fig.21).

2) Automatic Operation

Automatic operation involves the following steps:

i) Load lock chamber vent

ii) Set substrate

iii) Select process sequence

i) Load lock chamber vent: Same as manual operation, verify the Load-lock

chamber is in vacuum or not. If the chamber is in vacuum, click the VENT button

in PC Transfer Window (Fig.16). During venting, a chamber releasing warning

message will be displayed at the bottom of the screen (Fig 17).

ii) Set wafer: same as manual operation, place samples on the carrier plate, and set the

plate on the load lock arm (Fig. 18).

iii) Select process sequence: in PC Sequencer window, click OPEN to open the

sequencer library, and select the right sequence to be use (Fig. 22). To check details

of the sequence, click VIEW to open the sequence editor (Fig.22), which provide

you the information of the recipe inserted. If you cannot find a sequence that

contains the recipe you want to use, please consult NFF staff. Please be reminded a

sequence is not a recipe, it only executes the sample loading/unloading. So, run a

sequence contains wrong recipe will get unexpected result.


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Fig. 22: Sequence selection menu

After confirming the selected sequence in the screen (Fig.23), in PC Sequencer Window,

click on the text bar of the Next Carousel, and input simple log name, i.e. project

number (Fig.23). Next, click RUN button to initiate the process sequence (Fig. 23).

When all the steps executed automatically, you just need to collect back the samples

when the sequence completed.

Fig.23: Sequencer Window


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If there is any problem during sample transfer, in the PC Transfer Window, click

ABORT button to stop the transportation or pump down sequences.

4.9 Process Recording during the process

1. Please be reminded you are required to fill all the details of the log sheets

2. However, if you fail to do this, a punishment will be given

3. Write down any problems or comments in the log sheets

4.10 Clean up

1. Clean up the area

2. Return items to their proper locations

4.11 Check out

Check out the equipment in the NFF equipment reservation website immediately after

use.

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