Sigma SQC-122c manual Chapter Operation Sensor Setup

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Chapter 2

Operation

2.4Sensor Setup

The theory of operation for a quartz crystal sensor is quite simple. The sensor initially oscillates at its natural frequency, typically 6MHz. As material is deposited on the substrate, it is also deposited on the sensor. Depending on the density of the deposited material, and the amount of material deposited, the sensor’s frequency will drop from its initial frequency. The rate and thickness can be calculated from this frequency shift.

Sensor setup involves selecting the sensor(s) to be used, setting the Min/Max crystal frequencies, and adjusting the Tooling Factor. Sensors are assigned to each film, as described in Section 2.2, Defining a Film. See Section 3.5 for information on setting up dual shuttered sensors.

In the System Params menu, Max Frequency is the initial frequency of a new crystal, typically 6.0e+06 Hz (6 MHz). Due to manufacturing tolerances, some crystals may oscillate above 6MHz initially, which would be detected as a sensor error. Setting the Max Frequency slightly above the nominal value, to say 6.1MHz, will avoid this problem with no effect on instrument accuracy.

Min Frequency is the frequency where the SQC-122c will flag a sensor as bad. For a 6MHz crystal, the Min Frequency is typically 5 MHz.

Crystal failure is often predicted by brief periods of “mode hopping,” where the crystal briefly makes an abrupt change in frequency, or stops oscillating altogether. Some materials will cause crystals to fail or mode hop well before 5MHz. It is good practice to set the Min Frequency to a value that indicates crystal failure well before most crystals actually fail.

To better determine impending crystal failure, Crystal Quality and Stability parameters are also available for each Film. See Chapter 3, Film Menus for more information on setting Crystal Quality and Stability.

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Contents SQC-122c Thin Film Deposition Controller User’s Guide Safety Symbols Safety InformationWarranty Information Limitation of WarrantyReturn Policy Chapter Operation Table of Contents Chapter Quick StartChapter Menus Chapter OptionsAppendix Thin Film Process Overview Chapter Quick Start IntroductionChapter Quick Start Front Panel Chapter Quick Start Rear Panel Power Input FuseChapter Quick Start System Connections Chapter Quick Start Installation Power Chapter Quick Start Process SetupQuick Setup SelectEdit Mode Layer Chapter Quick StartExit to Main Chapter Quick Start Depositing a Film This page left blank for your notes Chapter Operation Introduction DefinitionsDefining a Film POWER% POWER% Deposition Controls Menu Layer Edit Menu Chapter Operation Defining a ProcessChapter Operation Chapter Operation Sensor Setup Tooling U n d e r 1 0 0 % Chapter Operation Chapter Operation Source Setup Chapter Operation Running a Process Chapter Operation Next Menu Zero THICKNESSkA RATEA/s 824 55.3 Chapter Operation Loop Tuning Chapter Operation No Readings, or Erratic Readings from Sensors Chapter Operation TroubleshootingPoor Rate Stability Incorrect Rate or Thickness MeasurementThis page left blank for your notes Chapter Menus Introduction Chapter Menus Main Menu Default, power-up Main Screen display is shown belowNext SetupMenu Quick FilmChapter Menus Next Menu Screens Exit to Main Edit Chapter Menus Quick Setup MenuPrev Layer Next LayerChapter Menus Main Screen Prev Menu Select Edit Delete Control Knob Chapter Menus Process MenusInsert Layer Control Knob Main Screen Prev Menu Edit Cut PasteExit to Main Prev Menu Edit Control Knob POWER%Chapter Menus Main Screen Prev Menu Edit Delete Control Knob Chapter Menus Film MenusExit to Main Prev Menu Edit Exit to Main Prev Menu Edit THICKNESSkA RATEA/s Deposition Controls Menu Chapter Menus Chapter Menus Chapter Menus Chapter Menus System Parameters Menu Chapter Menus Chapter Menus Mapping Menu Chapter Menus I/O SetupInputs Explanation high input causes Relays Explanation closes whenThis page left blank for your notes Full Rack Extender Installation Chapter Options IntroductionOption Card Appendix Material Parameters General Specifications Appendix SpecificationsMeasurement SourceDisplay Connector Wiring Relay Pins Input PinsAppendix O Connections Appendix Appendix Handheld Remote Controller Appendix EC Declaration of Conformity Complies with the Essential Health and Safety RequirementsDeclares that the product Uses the following standards