RF Etch Monitor. Introduction

Transcription

1 RF Etch Monitor Introduction A newly designed RF Matching Controller & RF Etch Monitor replaces the old OEM design of the RF Matching Controller and the RF Etch Monitor. OEM RF Matching Controller: - Analog electronic circuit generates the PLASMA signal (when some Self Bias Voltage has been achieved and Request for power is present), - Analog electronic circuit controls DC motors for Tuning capacitors based on Magnitude and Phase signals from the Discriminator unit, OEM RF Etch monitor: - RF Etch Monitor has been designed to ensure that the RF etch performs correctly. - If the RF Etch process performs correctly, the BIAS signal falls within a selected percentage deviation from the POWER COMMAND signal. If the BIAS signal falls outside this deviation, the Monitor alerts the System Controller and RF etch process stops with Message OUT OF REGULATION - Digital/Analog electronic circuit generates AT POWER signal based on BIAS and POWER COMMAND signals during ENABLE phase during ETCH Stage. - This circuit just copies the PLASMA signal during RF OFF, SETTLING TIME, POWER RAMP and DELAY phase of ETCH stages. The newly designed RF Matching Controller & RF Etch Monitor: - Microcontroller based design integrates function of OEM RF Matching Controller and RF Etch Monitor - Integrated 256x64 pixels graphics screen (VFD), - Shows RF Generator parameters (Forward and Reflected Power, DC voltage on output), - Easily configurable RF Matching System tuning of Phase and Magnitude Capacitors with Preset feature, - Shows Time Chart for POWER COMMAND and BIAS signals, - The system is fully configurable and reprogrammable, - This system allows the user to monitor the whole etch process (intermediate phases included) and can also highlight unexpected events

2 Description There are two basic function of the RF Etch Monitor: - Motors driving for Matching Network Magnitude and Phase Tuning Capacitors based on signals from Discriminator, - Self Bias monitoring during whole Etch Process within a selected deviation. Driving of the Tuning Motors is based on the simple algorithm but it is fully adjustable by menu parameters. It normally runs automatically all the time, but there is also a way to control the Tuning Motors manually. There are five basic screens to monitor the majority of parameters for the whole RF Etch Process and for setting up RF Etch Monitor Parameters. - Operation Screen with RF Generator Parameters - Operation Screen with Control and Bias Signals - Trace Screen 125 Sec Range - Trace Screen 250 Sec Range - Menu RF Etch monitor is fully working regardless of the selected screen and its function is not affected during setting or changing of parameters. Screens are activated by Navigation switch according to this table: - 2 -

3 Operation Screen with RF Generator Parameters Operation Screen with Control and Bias Signals Trace Screen 250Sec Range Trace Screen 125 Sec Range Menu - 3 -

4 Operation Screen Present Forward Power (provided by the generator) in Watts 2 Present Reflected Power (provided by the generator) in Watts 3 Present Self Bias Voltage Feedback Reading (provided by the generator) in Volts Computer (Process Controller) Command Signal for Control of Self Bias 5 Direct Self Bias Voltage on the Etch Electrode 6 Position of the Phase/Magnitude Matching Network Capacitor 7 Phase/Magnitude Detector (Discriminator) Output 8 Arrow Symbols indicates The Phase/Magnitude Motors moving for the control of the Phase/Magnitude Tuning Capacitors AT symbol indicates Self Bias monitoring within allowed deviations this symbol is flashing in case of Self Bias is out of tolerance but within the time limit 10 Flash symbol indicates Plasma present in the Etch Chamber 11 Symbol indicates the State of Etch Process (S1, S2, RP, E1, E2) - 4 -

5 Operation Screen manual control of the Phase/Magnitude Tuning Capacitors Switch to manual control of the Phase/Magnitude Tuning Capacitors is possible in any Operation Screen (with RF Generator parameters or with Control/Bias signals) by holding of button more than 1 second. There is the flashing symbol on the Operation Screen to warn that the Automatic Mode is switched off Manual Control Symbol The Tuning Capacitors are controlled by buttons according to this table: Move the Magnitude Tuning Capacitor Right (Up) Move the Magnitude Tuning Capacitor Left (Down) Move the Phase Tuning Capacitor Right (Up) Move the Phase Tuning Capacitor Left (Down) Exit Manual Tuning Mode The Manual Control Mode is switched back to the Automatic Control Mode immediately by using of button or after preset time delay automatically

6 Trace Screen Dotted line History of the Command Signal for Control of Self Bias 2 Self Bias Voltage Axis (0-100% range) 3 Time axis 125 second history range 4 Symbol indicates the State of the current Etch Process (S1, S2, RP, E1, E2) Dotted line History of the Upper limit for Self Bias 6 Dotted line History of the Lower limit for Self Bias 7 Solid Line History of the Self Bias (thickness of the line represents variation of the signal within the time period resolution (0.5 seconds for 125 seconds range and 1 seconds for 250 seconds range) 8 Time axis 250 second history range 9 Solid line - AT Power signal history 10 Dotted line Self Bias is out of tolerance but within the time limit - 6 -

7 Menu Using of the Navigation switch one of 9 submenus can be selected. Selected Submenu has to be confirmed by button. For each Submenu the Navigation Switch is used according to this table: Move the Cursor to the next upper item (Up) Move the Cursor to the next lower item (Down) Change the selected Item Value Up (Increase) Change the selected Item Value Down (Decrease) Exit the Submenu with saving of the changes confirmation Every changed value must be confirmed before it takes effect: Some values has been changed! Save new data to EEPROM? YES / NO - 7 -

8 Display This Submenu is used for setting of parameters regarding to VFD. Display brightness: One of 7 levels of VFD brightness can be selected. Higher brightness can shorten the lifetime of VFD however. Screen saver time: 5 mins (OFF, 1, 2,..., 99) mins For saving of VFD to avoid static pictures and subsequent phosphor degradation the screens can be periodically changed between Operation and Trace Screen. Power off time: 2 mins (OFF, 1, 2,..., 99) mins In case of no process on the tool, the RF Etch monitor can be switched to the Power off Mode to minimize the energy consumption and VFD saving. The RF Ecth Monitor will be switched on automatically when the next process will start. Etch Monitor The RF Etch Monitor automatically detects all stages of the whole Etch Process: Settle Time Ramp Time Etch Time For more precise setting of parameters for process monitoring, the Settle and Etch Time are divided into two parts. This should be useful to cover Self Bias voltage stabilization time after start of process (Plasma ignition) or changing of power (after ramping). There is a table in this Submenu for defining of windows, when the Etch Process is good AT POWER Signal

9 S1M S2M RPM E1M E2M S1P S2P RPP E2P E1P S1 S2 RP E1 E2 S1T E1T S1T: 7 E1T:5 s S1P:50 S2P:10 RPP:20 E1P:20 E2P:10 % S1M:20 S2M:10 RPM:20 E1M:20 E2M:10 % These values are editable in range and for S1T and E1T the values are in seconds, and for S1P, S1M, S2P, S2M, RPP, RPM, E1P, E1M, E2P, E2M the values are in percentage of power (100% means Volts Self Bias Voltage) S1: The first part of the Settle Time begins when the Control Signal changes from 0 to 10% and ends after S1T time interval S2: The second part of the Settle time beginning immediately after S1 and ending when the Control Signal started to rise RP: The Ramp Time is during rising of the Control Signal to desired the Self Bias Level E1: The first Part of the Etch Time begins immediately after RP and ends after E1T time interval. E2: The second part of the Etch Time begins immediately after E1T and ends when the Etch Process is finished

10 Etch Settings Bias min. Level to turn off plasma: 3 (0..213) The minimum value of the Self Bias Voltage to detect Plasma in Chamber condition Control min. Level to turn off plasma: 3 (0..213) The minimum value of the Control Signal to detect request for some process Time-out to turn off plasma: 5s (0..255) The time delay, how long can be the Etch process out of defined tolerances before switch of AT POWER Signal Turn off Etch monitor: NO YES Disable the Etch Process Monitoring Chart Preferred time base on chart: 250s 125s To select which of the Trace Screens (125 seconds or 250 seconds range) will be used for changing with Operation Screen for Screen Saver Option Display BIAS line: ENABLE DISABLE Enables or disables to show Self Bias Voltage history on the Trace Screen solid line Display CTRL line: DISABLE ENABLE Enables or disables to show Control Signal history on the Trace Screen dotted line Display EDGE lines: ENABLE DISABLE Enables or disables to show Edge of Control Signal History Tolerances on the Trace Screen dotted line Display AT POWER line: ENABLE DISABLE Enables or disables to show AT POWER Signal history on the Trace Screen

11 Motor Motor sample time: 100 ms ( ) How often are Tuning Motors switched ON and OFF (minimum ON or OFF time) Motor safety delay: 250 ms ( ) Time delay before the Tuning Motor changes direction Motor start level: 15 (0..110) Minimum signal level from discriminator to start the Tuning Motor Motor stop level: 5 (0..110) Maximum signal level from discriminator to stop the Tuning Motor Man. Control time-out: 5 min (OFF, ) Preset Time delay before the Manual Tuning Mode is automatically switched back to the Automatic Tuning Mode For some processes for easy plasma stabilization during settle time it is better to pre-tune matching network before a plasma strike in chamber. Other This feature allows doing it. Preset value for Phase: 75 % (0..100) Preset value for Magnitude: 25 % (0..100) Hysteresis preset for values: 2 % (1..25) This is dead band for preset values. The real preset value will be specified value plus/minus this hysteresis value. Move to preset when no Plasma: NO YES Enable or Disable this feature. Movement of the Tuning Capacitors to the preset values is done every time, when there is no plasma in chamber. This provides to have the Matching Network pre-tuned every time before a plasma strike. Free RAM: 1465 Bytes Reset all EEPROM values to default: NO YES

12 Set all Factory Settings Generator s baud rate: 9600 ( k2) This value must be the same like RF Generator Setting. Preferred Main screen type: ADC GEN To select which of the Operation Screens (with RF Generator parameters or with Control and Bias Signals) will be used to change Trace Screen for Screen Saver Option Help/Legend Exit Menu Short built description of how to operate the RF Etch Monitor Goes back to the last Operation or Trace Screen

13 Installation Installation of the newly designed RF Etch monitor is very easy. All that needs to be done is to replace the OEM RF Matching Controller with the new RF Etch Monitor. To upgrade the Sputters equipped with the OEM RF Etch Monitor it is easier to leave it there, but the OEM RF Etch Monitor has to be switched on at all times! Last step is to connect the serial cable between RF Generator and the new RF Etch Monitor. All the factory settings should be suitable for most of sputters and processes