Plasma-Therm PECVD A PECVD (plasma enhanced chemical vapor deposition) reacts gases in a RF (radio frequency) induced plasma to deposit materials such as silicon dioxide and silicon nitride. This PECVD has two chambers. One is intended for silicon nitride depositions and has 2% silane in nitrogen (SiH 4 /N 2 ), ammonia (NH 3 ), nitrogen (N 2 ), and 10% tetrafluoromethane in oxygen (CF 4 /O 2 ) connected. The other chamber is intended primarily for silicon dioxide depositions and is connected to 2% silane in nitrogen (SiH 4 /N 2 ), nitrous oxide (N 2 O), ammonia (NH 3 ), and 10% tetrafluoromethane in oxygen (CF 4 /O 2 ), which is used for cleaning the chamber. Typical deposition rates range from 100 Å/s to 400 Å/s. Operating Characteristics Typical Processes Silicon Dioxide Silicon Nitride Silicon Oxynitride See recipe list for more information. Operating Instructions I. Loading 1. Login to the machine. 2. Press the ON button at the bottom of the screen. 3. Highlight Utilities, Select Active Chamber, and choose the appropriate chamber (depends on the process you are running!). 4. Press the STANDBY button at the bottom of the screen. 5. Highlight Utilities, Vent. 6. Listen for the sound the chamber venting. Once you hear the nitrogen escaping from the chamber, lift the chamber door. If the nitrogen does not turn off automatically, highlight Utilities, Close Gates. 7. Load sample into the center of the chamber. 8. Highlight Utilities, Pump Chamber II. Operating
1. If you do not already have a recipe, see the Recipes section of this document. Highlight Process, Load Recipe. 2. Press the READY button at the bottom of the screen. 3. After READY parameters have been applied and press the RUN button at the bottom of the screen. Note: you can skip the first step of your process that lets the source cool down to the set temperature by pressing END STEP. III. Unloading 1. After the process is over, press the STANDBY button at the bottom of the screen. 2. Highlight Utilities, Vent. 3. Listen for the sound the chamber venting. Once you hear the nitrogen escaping from the chamber, raise the chamber door. If the nitrogen does not turn off automatically, highlight Utilities, Close Gates. 4. Unload sample from the chamber. 5. Highlight Utilities, Pump Chamber. Recipes In general, your recipe should have seven steps: an initial step, a purge step, an evacuation step, two process steps, another purge and an end step. The initial step evacuates the chamber and brings the chamber to the process temperature. The purge step continues to evacuate the chamber, ensuring there are no lingering process gases in the process chamber. The evacuation step purges the gas lines, ensuring that there is no unwanted gases in the lines that could possibly contaminate the process plasma. The first process step stabilizes the process gases and pressure without RF power. Due to the RF power being off, no etching will actually take place during this step. The second process step is identical to the stabilization step except the RF power is on. The etching of the process takes place during this step. The end step pumps the system back to base pressure. Instructions From the Process menu, choose Build 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 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 10-30 seconds. This will cause the system to evacuate as much air from the chamber as possible before starting the process. Set the temperature to your desired process temperature. Note that the temperature is measured in degrees Celsius. Room temperature is 25-30 degree Celsius. You should describe your recipe in the Description box. The first few words will be displayed by the filename when you are loading your recipe. Purge Step The purge step removes any lingering gases from the process chamber. This step should be 30-60 seconds long. The pump should be the same pump selected during the initial step. The pressure set point should be 1.0 x 10-2 Torr. There is an option to strike a plasma in this step if it is desired to clear gas from the chamber. Evacuation Step The evacuation step purges gas from the gas lines in the system in order to insure only the desired process gas will contribute to the etch process. This step should be 30-60 seconds long. The pump should be the same pump selected during the initial step. The pressure setpoint should be 1.0 x 10-2 Torr. Process Step All recipes should contain two process steps. They should be identical with a few exceptions. The process step dialog box has four major areas: time, pressure, gas flow, and power. 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 30-60 seconds is acceptable Process Step The second step will actually perform your process. Pressure Select the proper pump from the pull down menu based on your desired process pressure. Set the pressure to the process pressure you want for both process steps. Gas Flow
Set the flow rate for each gas here. The flow rates are given in sccm (standard cm 3 /min). The flow rates should be the same for both process steps. All of the channels are utilizing a 100 sccm mass flow controller (MFC). Power Leave the power set to zero in the first step. Set it to the power you want for your etch process in the second process step. There is a 500W power supply on this tool. The maximum allowable power setting is 80% of the maximum power or 400W. Do not exceed 400W for this step, as the power supply will be unstable above 400W and the lifetime of the power supply will be shortened. End Step All recipes have an end step that evacuates the chamber to the base pressure. The pump should be the same pump selected during the initial step. Set the pressure to 7.0 x 10-2 torr and set the time to 10-30 seconds. View Standard Plasma-Therm Recipes End Step Using 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. Manual Mode 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. Personal Safety To prevent risk of personnel injury, all maintenance and repair procedures must be undertaken by technically qualified person(s) who are fully aware of all relevant safety precaution associated with processing, operating and maintaining the equipment. If you detect any chemical fume from the process chamber, please STOP your process and contact a staff member immediately. Potentially lethal voltages (in excess of 30 volts AC and 50 volts DC) are present on the equipment. If you see any open and broken wire or exposure electrical parts, DO NOT try to fix it. You have to contact a staff member right away. To prevent an uncontrolled hazardous gas flow to the process chamber, which could result in personal injury, DO NOT open the by-pass valve in the gas box when flowing a process gas.