ksa ICE - Integrated Control for Epitaxy

Transcription

1 Introduction The k-space Integrated Control for Epitaxy system (ksa ICE) is a modular in-situ metrology tool designed for today s MOCVD reactors. It combines proven ksa MOS, ksa BandiT, and ksa RateRat patented technologies, as well as an emissivity corrected pyrometry (ECP) module. By integrating these various measurement modules into a single optical head, ksa ICE is capable of measuring real-time temperature, reflectivity, growth rate, film thickness, substrate curvature and film stress during MOCVD deposition, annealing, and etching. Each measurement capability is modular, so capabilities can be added or removed as needed. The patented temperature measurement modules available within ksa ICE are independent measurements of the wafer / wafer pocket temperature via emissivity corrected pyrometry (-ECP), ECP in-situ calibration and wafer carrier temperature via blackbody spectrum analysis (-BB), and the absolute semiconductor material temperature (even for GaN films or bulk GaN substrates) via band edge thermometry (-BE). The patented curvature/bow measurement technique (-MOS) is performed by monitoring the substrate curvature with an array of parallel laser beams, detecting stress-induced changes via relative laser spot spacing on a high resolution CCD detector. The laser is also used in combination with a high speed photo detector to monitor and fit the surface reflectivity (-R), yielding real-time film thickness, growth rate, and optical constants (n, k). The system is ideally suited for real-time feedback to process control systems via its standard TCP/IP interface. An optional analog I/O module is also available. ksa ICE Product Specifications May 2014 Page 1 of 8

2 ksa ICE Modules and Real-time Analysis Capabilities ksa ICE -ECP -MOS -R -BB -BE Emissivity Corrected Pyrometry Curvature Reflectivity/Growth Rate Blackbody Band Edge Measurement Capabilities Emissivity Corrected Pyrometry Temperature (-ECP) Reflectivity, Film Thickness, and Growth Rate (-R) Wafer Curvature and Stress (-MOS) Blackbody Temperature Calibration ( -BB) Semiconductor Band-Edge Temperature ( -BE) Spectral/Static Film Thickness and Growth Rate ( -BE) Surface Roughness ( -BE) Description Measures the collected blackbody radiation intensity of a sample at a specified wavelength with a photo diode and integrates the measured signal into the standard pyrometry equations to determine temperature. Surface reflectance is determined in real-time via an LED at the same measurement wavelength and is used in real-time to correct the surface emissivity for accurate temperature measurement. Measures reflected laser intensity during growth and provides real-time optical constants (n, k), deposition rate, and film thickness via a patented Virtual Interface fitting algorithm. User is able to generate a thin-film deposition recipe, so multiple layers can be properly fit in real-time. Each layer can be triggered via an external trigger signal, or can be time-based to enable end point control. Measures differential spot spacing of a 1D, parallel laser beam array reflected off the sample surface to determine real-time substrate curvature/radius of curvature/wafer bow and film stress. Utilizes patented k-space Multi-beam Optical Sensor (MOS) technology. Measures the spectral blackbody radiation signature of a sample over a wide wavelength range (using NIR-range spectrometer), and curve fits the response in real time to Planck s equation to determine absolute temperature. This is a selfcalibrating technique: no temperature reference is required and is used in-situ to calibrate an ECP module. Measures the temperature-dependent semiconductor optical absorption edge (band gap dependence on temperature) and uses calibration files (generated at k-space in a vacuum furnace) to determine absolute semiconductor film/substrate temperature (not wafer pocket temperature). Analysis of below-gap spectral interference fringes to determine film thickness and growth rate in real-time during film deposition. Requires at least 1 µm of materials to be deposited, but can then be used to monitor very small (~ 1 nm) incremental changes in thickness. Analysis of the above-gap diffusely scattered light signal from the wafer surface provides a quantitative measurement of surface roughness. ksa ICE Product Specifications May 2014 Page 2 of 8

3 ICE Optical Components and Modular Enclosure ksa ICE uses customized optics for maximizing each signal for the highest performance required for the specific measurement and wavelength range. The curvature module (-MOS) utilizes a wavelength-tuned etalon to generate an array of parallel laser beams from a single diode laser source. The reflectivity module (-R) uses a high efficiency beam splitter and collimating optics to ensure high speed and high S/N reflectance signal, while the temperature module (-ECP, -BB, or -BE) use hot and cold mirror optics to ensure that signals are optmized in specific wavelengh ranges, while having no impact on the other measurements. All optics are rigidly mounted to reduce vibrational noise. All components are stabilized and/or temperature controlled to maximize lifetime and signal stability during measurements. -R: Photo Diode Output -MOS: CCD for laser array imaging -ECP: Photodiode -R and -MOS: Laser Input -ECP: LED Input -BB: Signal Output Typical ksa ICE-ECP-R-MOS Optical Head Design Specifications Other ICE configurations and mounting hardware are available upon request. It is HIGHLY recommended that an angled viewport is utilized to minimize back reflection of the k-space light sources. k-space can provide angled viewports in standard sizes if needed. If the -BE option is requested, an additional module is added to the above-shown ICE optics head. This module includes a broadband light source, which then requires a slightly larger viewport geometry (compared with the standard ksa ICE system) for taking diffuse reflectance measurements. Please contact k-space for further details on the -BE viewport requirements. ksa ICE Product Specifications May 2014 Page 3 of 8

4 Typical Hardware Layout The ksa ICE hardware configuration for a ksa ICE-ECP-R-MOS unit with an additional ECP head is shown in the layout below. This configuration requires a single CPU/hardware rack (standard 4U height). Additional ECP heads (up to five total) or ICE heads (up to 4 total) may be added for multi-zone or multi-reactor control and require two additional 2U rack control units (not shown). MOCVD Reactor Requirements Optical Access: An angled viewport (k-space can supply angled viewports upon request) of at least 4 degrees is required. Standard ksa viewport sizes include 1.33 o.d. (mini-conflat) and larger, slit-style viewports (for Veeco k465i and Aixtron G- series reactors). k-space can manufacture custom mounts for non-standard viewport flanges. Minimum clear aperture diameter of 1.8 mm is required for -ECP, 2.3 mm for -MOS curvature measurements. Contact k-space for -BE module open access requirements. Synchronization of Data During Rotation: Add-ons From user supplied home pulse: 3-24 V, positive or negative going pulse. Minimum pulse width of 50 µs. If no home pulse is supplied by customer/reactor, ksa can supply the synchronization in one of two ways: - Synchronize based on platen/wafer reflectivity signal (ICE-R) - Synchronize using optical-trigger mounted in proximity to rotation spindle (ICE-TRG) Additional ICE Modules: Up to 5 separate ECP-only heads can be added, or 3 full ksa ICE heads. Mapping: A scanning detector (ICE-MWSD) option is available for units with slit type optical access which covers one wafer carrier radius. This capability allows for full platen scanning and wafer mapping. ksa ICE Product Specifications May 2014 Page 4 of 8

5 ICE System Specifications Curvature (-MOS) Reflectivity (-R) Temperature (-ECP, -BE, -BB) Measurement Down to km -1 +/- 0.1% ECP: +/- 0.2 ºC (> 450 ºC) Resolution BE: +/- 0.5 ºC (GaN/MQW film temperature) BB: +/- 0.2 ºC (bare wafer or platen, > 400 ºC) Film thickness +/- 1 nm after 200 nm +/- 1 nm after 200 nm +/- 1 nm after 3000 nm Spot Diameter or Collection Area on Wafer Up to 1 x 4 laser spot array (Each spot is ~0.8 mm diam.) mm mm 2 Calibration Type Cable Length and Type Light Source Sensor ksa-supplied calibration Known reflectivity ECP: with integrated or external BB module mirror(s) or wafer wafer (i.e. sapphire, BE: based on substrate calibration file silicon) BB: based on blackbody curve fitting 10 m CAT5 Ethernet cable 20 ft power/data cable ECP: 10 m 600 µm LOH Fiber with steel jacket BE/BB: 10 m 600 µm HOH Fiber with steel jacket (bifurcated) Laser Wavelength: 660 nm nominal (550 nm and 405 nm ECP: 950 nm HBLED lasers available upon request) BE: 300 W Xenon Light Source Laser Output Power: >30 mw, measured directly at laser BB: none required output. Beam Geometry: Circular Gaussian output with integrated long focal length lens cell Operation Mode: Constant current output Stability: 0.2% Interline transfer CCD, removable cover glass, selectable electronic shutter, on-chip integration capability, sensor area is 2/3 format (8.8 mm x 6.6 mm). Larger format and higher resolution CCD s available upon request Amplified silicon photo detector ECP: Amplified silicon photo detector, 950 nm collection BE: nm 512 element VIS Si-CCD spectrometer BB: nm 128 element, temperature stabilized NIR InGaAs Spectrometer Signal/Noise 12-bit 56 db or better 60 db or better 16-bit Exposure Time: 1 µs to 20 ms (patented autointensity control) Up to 2 MHz ms typical (patented auto-intensity control) Data Acquisition Hz typical Hz typical Hz typical. External TCP/IP Interface Communications and I/O Interface 2x Digital Triggering Inputs (DB-9 Connector) 1x Rotational Trigger Input (BNC) Optional USB Analog Module: 2X 0-10V Analog Output (DB-9 Connector) Control Unit 19 4U rack with single ksa ICE system. Additional 4U controller module(s) are required for multi-head systems. Computer ksa-supplied Windows 7 Professional 64-bit, QuadCore Processor, 4GB DDR3 SDRAM, 500GB (minimum) SATA Hard Disk, 512MB DVI+HDMI Video Card, Gigabit Ethernet, USB2, USB3, DVD +/-RW, USB keyboard, USB optical mouse, 22 flat panel monitor. Computer specifications are subject to change at any time. Other light sources, sensors, and corresponding optics can be implemented in order to accommodate other applications and materials. ksa ICE Product Specifications May 2014 Page 5 of 8

6 ksa ICE Integrated Software (VER. 1.3X) The ksa ICE software utilizes the user-friendly windows-standard operating environment with extensive error checking and file handling. Data storage in ASCII, Excel or binary file formats facilitate alternative data analysis by user. The ksa ICE software allows for full real-time integration and display of all pertinent acquisition parameters, at all marker positions. Transport of graphics directly to Windows clipboard or exported to Windows Metafile, Tiff or Bitmap format. User configured window layout. Complete TCP/IP interface for custom, real-time data transfer and program control. Analysis only ksa ICE software is a great complement to the ksa ICE system and software and allows for viewing and post-deposition/acquisition analysis. Example ICE Software Layout: MOS: Current Laser Array Image 2 -R: Reflectivity trace over a full rotation (Note the 5 user placed markers) 3 -MOS: Latest Curvature value measured for each marker position 4 -R: Latest Reflectivity value measured for each marker position 5 -BB: Temperature measured by blackbody signal for each marker plotted versus time 6 -BB: Current Blackbody curve fit spectra for Marker 1, with Goodness of Fit parameter 7 -BB: Temperature measured by blackbody signal for Marker 1 plotted versus time 8 -R: Reflectivity measured for each marker plotted versus time 9 -MOS: Curvature measured for each marker plotted versus time ksa ICE Product Specifications May 2014 Page 6 of 8

7 ksa ICE Features: Multi-Wafer Tracking and Marker Positions ksa ICE uses signal intensity changes in the wafer and carrier to visually trace and define wafer positions during rotation. The user is then able to accurately place measurement markers at any position to enable real-time monitoring at that location. Wide markers (as indicated on the right) are available when averaging over a particular wafer or carrier area is desirable for process control. Up to 20 markers may be placed within or across multiple wafers. Dynamic Intensity Control (ksa patented) During film deposition, the surface reflectivity will change due to changes in material properties and/or surface morphology. k-space has developed and patented a software-based algorithm for dynamically adjusting the laser and/or detector integration times to maintain the highest S/N during these changes. This feature comes standard on all ksa ICE systems. Dynamic Platter Synchronization (requires -R, ksa patent pending) k-space has developed the ability to synchronize to the rotating platen by analyzing the reflected laser signal from the reflectivity module (-R) in real-time and internally generating the appropriate trigger signals for all devices. This alleviates the need for a hard trigger source, and solves the problem of slipping platens that are not rigidly attached to the rotation shaft/spindle. ksa ICE Product Specifications May 2014 Page 7 of 8

8 Mapping with Scanning Detector Optics (optional ICE-MWSD) For MOCVD systems with slit style viewports, which provide full optical access to a wafer carrier radius, the ksa ICE optics head can be outfitted with a linear scanning servo drive. By taking data over the entire radius during rotation and sequentially moving the detector optics to each radial position, a full map of any ksa ICE parameter (i.e. curvature, temperature, or reflectivity) is provided for ontool uniformity analysis. ksa ICE Product Specifications May 2014 Page 8 of 8