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Revision 2 - 5 May 1999, David Sigmon

Plasma-Therm ICP

Trainers

An ICP (inductively coupled plasma) etcher can be used to etch a variety of materials. This ICP is equipped with two chambers -- one is dedicated to deep silicon trench etchine using a proprietary process. The other is used for silicon dioxide and polymer etching.

Both chambers are pumped with turbomolecular pumps for low pressure operation. Etching is performed with a RF (radio frequency) induced plasma of various gases.

The left chamber is intended for polymer / oxide etching and is equipped with chlorine (Cl₂), boron trichloride (BCl₃), hydrogen (H₂), argon (Ar), oxygen (O₂), and tetrafluoromethane (CF₄).

Operating Instructions

I. Loading

Operator Login

Login to the machine.
Press the STANDBY button at the bottom of the screen if it is not already lit.
Highlight Utilities, Loadlock, Vent.
Select Windows, Loadlock Diagram. The loadlock pressure will be displayed in the diagram. The system cannot measure pressures above about ten torr. If the pressure is between ten torr and atmospheric pressure, the system will indicate a pressure of "VACCUM." Wait for the pressure to reach "ATMOSPHERE," then open the loadlock. If the system does not display "ATMOSPHERE" after five minutes, try gently lifting the loadlock handle. Do not attempt to force the loadlock open. If the loadlock will not open, contact MiRC technical staff.
Load sample into the center of the chamber.
Close the loadlock cover.

II. Operating

Select Utilities, Select Active Chamber, and select the chamber you are going to use.
If you do not already have a recipe and a batch, see the Recipes and Batches sections of this document. Highlight Process, Batch. The batch window will appear. Select File, Load. Select the batch you want to load.
Press the READY button at the bottom of the screen.
After READY parameters have been applied, hold the loadlock cover down and press the RUN button at the bottom of the screen. Note: If you don't care about the chamber temperature, you can skip the first step of the recipe by pressing END STEP.

Note: Do not press abort without reading these instructions.

If you must abort your process, you may press abort while the process is running. The system will ask "Abort process?" Make sure that these are the exact words used in the message before answering. You may answer yes to "Abort process." You will then be asked "Abort batch?" Never answer yes to "Abort batch?" If you do, your sample will be trapped inside the process chamber and will have to be removed by MiRC staff.

III. Unloading

After the process is over, press the STANDBY button at the bottom of the screen.
If your batch does not automatically vent, highlight Utilities, Vent.
Unload sample from the chamber.
Highlight Utilities, Loadlock, Pump Loadlock.
Highlight Utilities, Logout.

Warning: If one of the following conditions occurs, immediately stop operating the ICP and place a "machine down" sign on the system. Contact MiRC technical staff immediately. Severe (several thousand dollars) damage can result if the system is operated with wafer fragments in the chamber.

If you find that your wafer is broken or chipped when you remove it from the ICP.
If your wafer does not return to the loadlock when the ICP tries to unload it.
If the ICP gives a "Loadlock tray not present" alarm.

Recipes

Overview

In general, your recipe should have four steps: an initial step, two process steps, and an end step. The initial step evacuates the chamber, removing the air inside, and brings the chamber to the process temperature. The first process step performs your process without RF power for about 30 seconds. This fills the chamber with the process gasses and removes any remaining air from the chamber before the actual process starts. It also allows the chamber pressure and gas flows time to stabilize. Because the RF power is off, no processing will actually take place during this step. The second process step performs the process.

Instructions

From the Process menu, choose Chamber, New to create a new recipe or Edit to edit an existing one. A list of the recipe steps will be displayed on the right side of the screen. To edit a step, double click on it. To create a new step, select the step that will go after the new step and click the appropriate button for the type of step you want at the bottom of the screen.

Initial Step

Initial Step

All recipes start with an initial step. This step will evacuate the chamber and bring the chamber to the desired operating temperature.

Set the pressure to 1.0 x 10^-2 Torr and set the time to 30 seconds. This will cause the system to evacuate as much air from the chamber as possible before starting the process. Do not attempt to use pressure setpoints below 1.0 x 10^-2 torr. The chamber will be evacuated as much as possible regardless of the setpoint.

Set the temperature to your desired process temperature. Note that the temperature is measured in degrees Celsius.

You must enter a name for your process in the Name box. The name may be up to eight charactors long.

You may describe your recipe in the Description box. The first few words will be displayed by the filename when you are loading your recipe.

Process Step

You will usually want two process steps. They should be identical with a few exceptions. The process step dialog box has five major areas: time, temperature, pressure, gas flow, and power.

Process Step

Time

The first process step should be set to "Fixed Time" This step will be used to stabilize the chamber conditions. The time for this step is not critical, but 30 seconds is good.

The second step will actually perform your process. You must set this step to "Fixed Time" and set the time here. Variable time does not work on this system.

Temperature

Set the temperature to your desired process temperature for both process steps. Note that this should probably be the same as the temperature set in the initial step.

Pressure

Set the pressure to the process pressure you want for both process steps. If you are operating the RIE at lower pressures you will need to set the pump to the turbo pump. Otherwise use the mechanical pump.

Gas Flow

Set the flow rate for each gas here. The flow rates are given in sccm (standard cm³/min). The flow rates should be the same for both process steps.

Power

Leave the power set to zero in the first step. Set it to the power you want for your process in the second process step.

End Step

End Step

All recipes have an end step that evacuates the chamber. Set the pressure to 1.0 x 10^-2 torr and set the time to 30 seconds. When you modify a process, you only change the copy on the disk. If the process is already loaded, you will need to reload it for your changes to be reflected.

Batches

I. Instructions

To create or edit batch, select Process -> Batch -> New or Edit. To add a step, click on the button for the type of step you want to add. To delete a step, select it and click Delete. You will need to add a load step, an unload step, and an end step.

Batch Editor

Pump Loadlock

This will be the first step in the batch. It is automatically included.

Load Chamber

To add a load chamber step, click on the button with the arrow pointing to R or L depending on which chamber you want to use. R stands for right. L is left. A process step will be added after the load step automatically. You will be prompted for a recipe to run.

Process

A process step runs a recipe you have already written. One will be added when you add the load chamber step, but you can add another by pressing the appropriate process button for the chamber you are using.

Unload

The unload step moves the sample back into the loadlock. Press the button with the arrow pointing to the lock to add an unload step.

Vent / End

There are two types of end steps: vent and end. A vent step will vent the loadlock automatically and an end step will not. The last step in a batch must be a end or vent step.

Using Manual Mode

Manual Mode

Manual mode allows one to directly control the system parameters without creating a recipe. This can be useful for developing new processes. To operate the system in manual mode press STANDBY at the bottom of the screen. Make sure that the chamber is currently being pumped. Then select Service, Manual Mode. The manual mode window will appear.

This window is divided into four sections: Temperature, Pressure, Gas, and RF Control. Each of these sections is summarized below.

Temperature

This sets the temperature of the bottom and top sections of the chamber. Note that it will take a while for the temperatures to change after you change the settings.

Gas

This sets the flow rates for each of the gases. The gas flow will not start until you press the Gas button at the top of the display.

Pressure

This sets the chamber pressure. The chamber pressure will not be regulated until you press the Pressure button at the top of the display. You must have at least one gas on before you can turn the pressure on.

RF Control

This controls the power. Config should be set to "RIE" and Mode should be set to "Power." Set sets the power in watts. If Time is set to zero, the power will run indefinitely once it is turned on. If Time is set to anything else, the system will run for the time set and then shut off the power, gas, and pressure. Run indicates how long the power has been on. The power will not come on until you press the RF button at the top of the display.

Troubleshooting

The menu option I want to select is grayed out.

Some menu options are not available depending on which mode the system is in. Try switching between the "ON," "STANDBY," AND "READY" modes with the buttons at the bottom of the screen.

The alarm is going off.

To silence the alarm, press the ALARM SILENCE button at the lower right corner of the screen. At the bottom center of the screen, there is a box labeled "Alarm" that will tell you why the alarm is going off.

The reflected power is high or I get an "RF1 detected off" alarm.

If you know that the pressure you are using has worked before, try pressing HOLD one time only to make the system try again. If it still doesn't work, contact an MiRC staff member. DO NOT PRESS HOLD MORE THAT ONCE If you keep pressing hold, you may cause serious and expensive damage to the power supply.

If the reflected power is too high, the process will stop and the alarm will sound. Usually, if you still have high reflected power, the chamber needs to be cleaned. You can do this by running the batch named clean using the instructions above. You will want to remove your sample from the system before you do this.

If you are trying to run the system at a pressure you have never used before, and it still will not run after you clean it, this probably means that the system can not operate at the pressure you are using. You need to use another pressure. If you have run the system with the pressure and gas flows you are using before, contact MiRC staff for assistance.

My wafer broke in the chamber

Wafer fragments that remain in the chamber can severely damage the ICP. Put a "machine down" sign on the system and contact MiRC technical staff immediately.