EpiSoft MBE & Deposition Control System

What is EpiSoft?
EpiSoft Applications
EpiSoft Description
SerialFrame Universal Hardware Interface
EpiCAD Software

What is EpiSoft?

    Initially developed for MBE applications, EpiSoft provides a unique approach to deposition process and overall system control. It is built around the principle of defining the growth process in terms of deposition events (growth rates, doping levels...) as opposed to low level parameters (temperature, voltage, flow rate...); we call this growth-oriented approach SOC (Structure-Oriented Control):

  • SOC defines the structure in terms of a series of "events" (e.g. thickness or time specified steps) analogous to "drawing" the required structure. "High" level parameters (such as thickness, growth rate, doping level) are internally converted to "low" level values (such as temperature, voltage) as they are required.

Summary

EpiSoft comprises 2 parts:

  • SerialFrame Interface Unit. This connects the control and deposition systems via serial, digital and analogue interfaces.  SerialFrames offer unlimited expansion.
  • EpiCAD software.
    • Controls deposition process and the system
    • Control via growth-related parameters (SOC)
    • Powerful, integrated calibration management
    • Unprecedented process definition via event driven paradigm
    • On-the-fly process modification
    • Full user-defined data logging. Graphical data review
    • User-defined process/system protection via comprehensive alarms
    • Support for multi-zone sources, inter-source dependencies...
    • Host of advanced features such as dual sensor control (e.g. substrate temperature control via pyrometer & thermocouple), automatic source drift protection, watchdogs, parameter "tweaks" during deposition and much more...
  • SOC permits unprecedented ease of definition of, and control over, deposited features. For example, a linear composition ramp can be defined in a single step, as opposed to the complex list of temperatures required by low level parameter definition. More importantly, the required data profile can be much more precisely applied than is possible using manual (low-level) programming, as the required low level parameter values are calculated in real-time, at run time.
  • Growth data can be simply and intuitively analysed graphically: for example by comparison of intended composition, growth rate, doping levels with actual values.

    SOC is achieved through maintaining detailed "calibration" information (easily modified to reflect source digression) between the high and low level parameters within the EpiCAD software, which is only applied at the moment of communicating with the deposition system. The benefits of SOC extend well beyond the above:

  • All aspects of controlling the system can use SOC, from vacuum pressure monitoring to gas flow control, from shutter/valve status to real (as opposed to indicated) substrate temperature
  • Data is logged and presented in graphical format. This allows intuitive understanding of structural information, such as variation in composition, rate changes...
  • Recipes (EpiLists) can be re-used without modification across systems and irrespective of the calibration conversions between growth (SOC) values and low level parameter values
  • SOC allows automated correction for source instabilities/drifts, such as MBE source depletion
  • SOC makes possible sharing of expertise across labs and even between different deposition systems.
  • Sophisticated alarm conditions and actions can be readily defined and invoked to ensure correct and safe operation of the systems.

EpiSoft Applications

    EpiSoft has a 25 year history in controlling MBE and other deposition systems:

  • Used by some of the world's leading research and production facilities
  • Has been applied to most material systems: III-V, mixed-IV, II-VI, metals, HTSC, organics, using a wide range of technologies (solid-source, gas-source, laser ablation...)
  • Provides a unified interface for most technologies: effusion sources, e-beam sources, sputtering, gas lines, ablation...
  • Installed on all leading manufacturers (Omicron Nanotechnology, Veeco, VG, Riber...) as well as custom systems

EpiSoft Description

    The EpiSoft system comprises 2 parts: the PC-based EpiCAD software and the SerialFrame hardware interface unit which connects the PC to the deposition system components.

  The SerialFrame is a DIN-rail mounted "PLC" style interface with almost infinite expansion. It communicates with the PC using over the USB bus. A typical configuration comprises:

  • 12V dc power supply to power all units. (Universal 96-250Vac input range).
  • A Serial8 interface unit with user-configurable serial ports (RS232, RS422 or RS485).
  • An SFDig10 unit providing 18x relays (e.g. for shutter or valve control) and 4x opto-isolated digital inputs for interlocking 
  • An SFAn10 unit providing 4x 12bit analogue outputs, 8x 16bit differential analogue inputs & 12x opto-isolated digital inputs for interlocking.
  • Most applications can be more than adequately controlled using the above configuration, but Serial8, SFDig10 and SFAn 10 units can be added as required.  

SerialFrame Hardware Interface

All aspects of the SerialFrame, such as serial settings (baud rate, parity etc.), analogue ranges, comms watchdogs are user-selectable from within the EpiCAD software.

SFDig10 Specification:

  •  DIN 9M plastic housing with 54 screw terminals for easy soldering-free wiring
  • 12Vdc powered from DIN-rail power supply
  • Max Power consumption: 4W (all relays on)
  • 18x relays: 14 as Form A (normally open), 4 as Form C (normally open and closed)
  • Max switched voltage: 125Vac, 60Vdc; max switching current 1A; max switching power 62.5VA/300W
  • Fast relay response time: typically <5ms from EpiCAD command to relay activation
  • 4x opto-isolated digital inputs for interlocking. Input sensitivity 4-32Vdc. Input resistance 2.2kΩ

SFAn10 Specificiation:

  • DIN 9M plastic housing with 54 screw terminals for easy soldering-free wiring
  • 12Vdc powered from DIN-rail power supply
  • Max Power consumption: 4W (all relays on)
  • dc:dc power supply isolation from main 12V input to analogue circuitry to avoid earth loops
  • 4x 12 bit analogue outputs. -0.2V to 10.2V mapped as 0-100%. Output updated with 1ms of receiving settings.
  • 8x 16 bit analogue inputs. Input protection: ±15V (unit off), ±33V (unit on).
  • Each analogue input has the following user options: gain setting of 1x (±10V), 2x, 4x & 8x (±1.25V), low pass filter.
  • User zero and gain calibration of analogue path (software)
  • 12x opto-isolated digital inputs for interlocking. Input sensitivity 4-32Vdc. Input resistance 2.2kΩ

EpiCAD Software

    EpiCAD is an object-oriented environment based around user-definition of P-Loops (process loops), ports (communication ports), sensors (digital input events) and flags (digital output events). Each object has a range of user-defined attributes which allow it to simulate operation of a deposition component (such as substrate, source, dopant, interlock, shutter, valve...). EpiCAD contains a knowledge base as to how the different objects interact in a real deposition process.

    In addition to SOC discussed above, EpiCAD provides a host of features including:

  • The Calibration Maintenance facility provides SOC with the relationship between high and low level parameters via a range of weighted fitting functions, and fast, easy re-calibration which mimics the way many deposition sources operate. Even consumption-based auto-correction of source depletion is supported.
  • EpiList editors use an intuitive event based paradigm to allow fast creation of deposition "recipes" of unlimited size. Thanks to SOC, all recipes are reusable without modification, even if source calibrations have changed! Includes automatic error checking, on-the-fly recipe editing during run, nested repeat sequences and much more...  
  • Data Acquisition. This fully user-defined facility provides for continuous logging of all system data, as well as separate recipe-related data acquisition. Data is presented graphically with full user-definition of resolution, zoom, time-span etc. Data can be exported as ASCII for spread-sheet import.
  • Comprehensive, multi-level user-defined alarm condition and actions for system protection and security
  • Slaving of process loops, for example, for automated operation of multi-zone sources
  • Dual sensor operation, for example, thermocouple AND pyrometer control over substrate temperature
  • Definition and assignment of multiple valve combinations to growth conditions (e.g. as line run, vent, purge, off...)
  • AND MUCH MORE!