RAITH 50 Technical Description

Transcription

1 RAITH 50 Technical Description Universal Electron Beam Lithography Tool Version page 1 of 28

2 INTRODUCTION RAITH 50 is a state-of-the-art high performance high-resolution lithography tool, which has been specifically designed for the University community. It has been optimized to serve the needs of researchers and scientists in a large range of micro- and nanostructuring applications. Priority in system design was given to versatility, ease of operation and economical setup to ensure a system use also for very specific and demanding tasks. The system operates under high end PC control, utilizing a Windows (1) NT networking environment. The complete software control of the instrument combines straightforward CAD layout design capabilities and direct pattern exposure with full access to all parameters of the advanced electron beam column. This makes the RAITH 50 ideally suited to mix & match applications on chip level, i.e. in electronic engineering, as well as to direct write tasks for fabricating advanced mesoscopic devices. These functionalities are complemented by state-of-the-art SEM imaging and integrated metrology capabilities, allowing line width and pattern placement control with the same tool. (1) (2) (3) Windows DXF GDSII is the registered trademark of Microsoft Inc. is the registered trademark of Autodesk Inc. is the registered trademark of Calma GE Version page 2 of 28

3 1 SYSTEM DESCRIPTION 1.1 General overview The RAITH 50 consists of the following main subsystems: Digital controlled LaB 6 -based electron column SEM sub system and Windows NT user interface Pattern generation and PC based lithography user interface Vacuum chamber, clean vacuum system and plinth X-Y-Z fully automated laser interferometer controlled sample stage The RAITH 50 lithography tool consists of self standing plinth which supports the chamber, stage, and electron optical system as well as the high vacuum system, high voltage units and system control electronics. It is equipped with a standard vibration isolation system for noisy lab environments more dedicated solutions are available on special request. A SEM/pattern generation console houses the networking components and pattern generation systems. On the console desk itself is the dual PC SEM and lithography control system. The small footprint the machine offers is advantageous when laboratory or clean room space is at a premium. 1.2 Electron optical column The RAITH 50 has a high resolution, solid and robust electron optical column. The column is carefully shielded to prevent interferences from stray fields. The standard LaB 6 electron emitter combines high beam brightness with high stability in beam current. The gun head is differentially pumped and protected by an automated gun isolation valve. The system can be operated in a voltage range between 0.2 and 30 kv and allows magnification settings in SEM mode of 20X to 400,000X. All settings are digitally controlled, stored and optimized, which is ideal for the wide range of patterning requirements in research and development. The beam current can be varied between 5 pa to approximately 20 na. In each case these changes can be made directly from the (SEM) PC. Writing fields can be selected digitally from 0.5 µm to 1000 µm. Writing field calibration can be performed automatically utilizing the laser interferometer. Digital addressing in Version page 3 of 28

4 the writing field is up to a maximum resolution of 16-bit by 16-bit. Any multiple of the minimum step size can be chosen directly, either numerically or pixel wise. An electrostatic beam blanker is integrated into the column and is synchronized to the exposure process via the Pattern Generator. Blanking occurs between individual elements of exposed structures (e.g., fractured trapezoids or line segments) and at the end of an exposure sequence. Furthermore, in the process of alignment, the beam is blanked at all times apart from mark scanning and subsequent pattern placement. The scan coils of the column can be driven via the Pattern Generator to a maximum speed of 4 MHz. The exposure dwell time range lies between 250 ns and 8 ms, with less than 2 ns minimum resolution. Maximum flexibility is then available for different resist types and associated sensitivities. Dose levels applied to any structure in the pattern can be controlled almost continuously. This especially is important for proximity effect corrections. 1.3 Lithography capability and control systems The system operates under Windows NT on a separate lithography control computer that is linked to the SEM control by a dedicated network interface. Due to the Windows format and software infrastructure, the user can create their own application specific sequences. Wide-ranging applications are reflected in the software user interface. Generally, different program modules for driving hardware, interfaces or data management can be linked together, if required, for fully automatic, sophisticated exposure sequences. Structures can be designed and exposed with the same software platform. The exposure can easily vary from single devices in single freely selectable writing fields up to large (up to 45 mm) capabilities. These can be one level direct write applications up to chip and small wafer scale Mix & Match tasks. Larger areas will be automatically fractured into corresponding equally sized stitching fields, e.g. required for mask making application. The main exposure mode is vector scan. Structures can be exposed line by line or in meander scan. Special exposure modes can be chosen such as single pixel lines (exposed lines with the width of one pixel) or dots. These can be exposed in any orientation. Special exposure schemes exist for exposing bit maps in raster mode (holograms) and others. Version page 4 of 28

5 A major software module is the GDSII database, viewer, and editor. The GDSII database is hierarchically organized. A special file extension allows freely selectable dose factor for each structure element. The hierarchical format can handle very large files and helps storing them efficiently. Editing of imported files in DXF, ASCII or CIF format are available as well as separate pattern creation. For final exposure pattern are fractured automatically with the basic elements being trapezoids. The flexible macro and command control system (based on Microsoft Visual Basic Script) is used to generate and run unattended batch lithography jobs. The syntax of the Script Control is easy to handle and straightforward to use. Storing and recalling these user-defined macros allows for powerful job automation. The Mix & Match (chip and wafer) - mixing optical lithography and (while matching) e- beam lithography - has been employed for many years. Taking advantage of the optical lithography throughput capabilities Mix & Match adds the full benefits that an e-beam system can supply, in particular ultra high resolution and precise pattern placement. Flexible Mix & Match strategies can be constructed via the different functions and modules of the software. Pattern placement can follow via automatic local mark registration or relying only on accurate laser stage positioning or a combination of both. There is no limitation to the size of the optical pattern to which the e-beam structures must be matched (in order to define the necessary devices). Field stitching is generally required for defining larger scale pattern covering an area on the substrate of the order of a few millimeters to many tens-of millimeters (and in some cases over many centimeters.) A typical application is the generation of research level photo masks. Writing field fracturing of the layout is then made on-line or during a preprocessing run, reducing overhead time in large area exposure sequence. Extensive post processing features are available (shrink, overlaps out and frame) to aid the optimization of pattern processing. The various functions can be applied on a hierarchical level. Complex high quality e-beam patterns often require proximity correction. This is especially important for closely packed differently sized pattern elements. The proximity effect is a direct result of the interaction of the electron beam with the resist and substrate in the form of forward and backward scattering, leading to overexposure in areas of pattern where structures are in close proximity to each other. This unique tool has been specifically designed for nano lithography and gives the benefits of accurate pattern exposure in an easy and quick manner alleviating any lengthy time consuming and sometimes impossible guesswork. The simulation feature of this module is a valuable tool to inspect the pattern with respect to proximity effects without starting an Version page 5 of 28

6 exposure. The results can be directly used for small redesigns of critical pattern by means of the integrated graphical editor. 1.4 Stage and sample handling An X,Y,Z laser interferometer stage (utilizing an L-shaped mirror in the X-Y plane ) provides a coverage area of 45 mm by 45 mm. The stage is motorized in all three axes by DC motors mounted on the spindles. Motorization of the Z-axis enables operation at different working distances. Sample loading/unloading is made directly onto the drawer-mounted stage and just takes a few minutes. Samples can be mounted off-line onto one of the sample holders provided with the system. Then the sample holders can be quickly slit into a pre-leveled mounting platform fixed on the stage - minimizing defocusing over large travel distance. The laser interferometer and associated electronics allow a minimum addressable stage movement of 2 nm. Positioning is made in closed loop mode with the DC motors (coarse adjustment within a few microns) and piezo elements mounted on the X and Y spindles carry out the fine positioning. Adjacent field placement accuracies (field size of 100 µm) are below 80 nm (2σ.) Calibration marks mounted on the wafer holder in the plane of the substrate can be used for auto field calibration and stage drift corrections. In automated procedures, auto field calibration and drift corrections can be referenced as required in a macro. A Faraday cup is mounted in plane of the sample on the holder. Variations in probe current can be measured and compensations automatically made in the required exposure dwell time. Version page 6 of 28

7 1.5 Vacuum system The high vacuum system is automatically controlled and monitored via the SEM control computer. An ion getter pump maintains the gun pressure while an automatically operated pneumatic column isolation valve separates the gun from the chamber. The main chamber is pumped by a turbo molecular pump that provides a working vacuum in the range of 10-4 Pa. The gun chamber and vacuum readings, vacuum ready and valve status are shown in the vacuum menu and optionally in the status menu of the SEM control computer screen. Penning gauges are used for high vacuum measurement. 1.6 SEM mode and controls The SEM mode is used to take top quality images, store and archive them. It runs under Windows NT on a separate SEM control computer. Digital control is provided for all SEM parameters from the keyboard and mouse. The system is designed for multi user access. User defined parameters can be stored and recalled for later sessions. Lens settings are controlled from the keyboard. Beam voltage and current settings can also be freely chosen. Version page 7 of 28

8 2 SUMMARY OF SPECIFICATIONS Lithography resolution 80 nm lines and 80 nm spaces * Image resolution 4 30 kv, obtainable Overlay accuracy (alignment) < 80 nm * # Field stitching < 80 nm * # Writing speed Beam current drift Beam drift 4 MHz <= 1% / hr (at ± 0.5 C) <= 5 nm/min (at ± 0.5 C) * Standard specifications met at time of instrument acceptance using a 100 µm by 100 µm writing field in developed PMMA of thickness less or equal than 100 nm. # Magnitude is measured mean value plus twice the standard deviation (mean+2σ.) Version page 8 of 28

9 3 TECHNICAL DESCRIPTION 3.1 Stage and Chamber Chamber High vacuum chamber, large enough to accommodate up to 4 wafers. Overall dimensions: 284 mm diameter, 280 mm depth Type of stage 3-axes X-Y-Z high vacuum stage with: laser interferometer position sensing in X and Y precision L-shaped plane reference mirror interferometer measuring path completely inside the vacuum (no environmental compensation required) rotary encoder position sensing in Z Travel range 45 mm travel in each X and Y 20 mm overall travel in Z Motor drives Stage travel velocity Laser interferometer resolution Laser source Closed loop positioning control Stage settling time Encapsulated DC tacho motors directly mounted on drive spindles. Motors enabled through microprocessor controlled Motor Controller, which also incorporates manual joystick control. up to 5mm/s 2 nm Frequency stabilized 633 nm HeNe laser. Coarse motion with DC tacho motors to within 0.2 µm of destination position followed by integrated fine movement with piezo elements, both operating in closed loop with interferometric position sensing. 5 µm piezo fine shift range 2 nm positioning resolution 1 khz cycle time 1 s Version page 9 of 28

10 Sample loading Sample leveling Large area sample holders are directly placed onto the sample platform on top of the laser stage. The stage is mounted in drawer-fashion to one side of the instrument s chamber. Sample mounting platform is pre-leveled at factory. 3.2 Sample handling Holders Universal holder with clamping devices for small pieces and other types of specimen up to 45 mm and 10 mm height. Stub holder for 13 mm SEM stubs 2 wafer carrier * (optional). 3 wafer carrier *, w/ or w/o Faraday cup accessory (optional). 4 wafer carrier *, w/ or w/o Faraday cup accessory (optional). * Note that stage travel is limited to 45 mm in X and Y so coverage over entire wafer surface is not possible. Current measurement Dedicated Faraday cup built into Universal holder and 2 wafer carrier. Pico ammeter with IEEE interface used for PC readout. Calibration targets 3.3 Vacuum system Control Field alignment calibration, alignment marks for drift compensation and faraday cup for current measurement mounted in the plane of the sample/substrate. Fully automatic high vacuum system with automatic column isolation valve. Pumping scheme Main chamber: Standard foreline pump in combination with turbo molecular pump (240 l/s) Bake out Electron gun: Ion getter pump for permanent clean high vacuum in gun region secured by a pneumatic gun isolation valve Integrated bake out control and equipment for electron gun Version page 10 of 28

11 region Gauging Penning gauge for high vacuum measurement in main chamber. Ion current pressure readout in gun region. Vacuum The ultimate vacuum in the specimen chamber is in the 10-4 Pa range. Indication Gun and chamber vacuum readings, vacuum ready and valve shown in the menu and optionally in the status menu. 3.4 Electron beam column and optics Electron source Operating vacuum of source Filament life Beam energy range Beam current range Blanking Image resolution Beam current drift Beam position stability Objective lens LaB 6 Crystal 10-6 Pa range 1000hrs (typically) 200eV to 30keV Selectable between 5pA- 20nA Electrostatic beam blanker with rise time of about 50 ns and repetition rate of MHz. Fixed arrangement for all operating voltages and beam currents. 4 30kV Gaussian spot <= 1%/h (room temperature < ± 0.5 C) <= 5nm/min (room temperature < ± 0.5 C) average value over 30 minutes Thermally stabilized by water cooling Version page 11 of 28

12 3.5 Deflection system Principle Single step high speed electromagnetic scan system, optimized for minimum field distortions, hysteresis and dynamic effects. Field size range 0.25 µm minimum 1000 µm maximum 20 µm to 400 µm recommended for lithography Minimal addressable step size Field Size / (16-bit) Field size adjustment Corrections made for rotation, orthogonality and zoom. Corrections can be entered manually or in an automated mode using metrology functionality of laser interferometer stage. 3.6 Scan generation Lithography pattern generator Principle Real time high speed digital Pattern Generator with integrated DSP and high speed Cache memory. SCSI data link to control PC (5 MB/s data transfer rate.) Fast on-line processing and exposure of primitives sent by control computer. Thermally controlled and electrically isolated analog amplifiers. Real-time write field corrections. Synchronized control of electrostatic beam blanker unit. Operation Vector scan as standard, trapezoids exposed line-by-line or by meander scan. Can expose arbitrary shaped single pixel lines and dots. Also capable of bit-map/raster scan and polar coordinates. Shapes of individual Rectangles, triangles, any polygons of any orientation Version page 12 of 28

13 pattern Beam blank control and shape. Lines and curves (multiple or single pixel wide) at any orientation. Dots, circles, cones. Alphanumerical text. Shapes generated by mathematical functions. Precisely synchronized to exposure with no measurable jitter. Software provides for programmable lead and stop times to compensate time effects from electron beam scan system. Dwell time and resolution 250 ns minimum dwell time. 8 ms maximum dwell time. < 2 ns resolution Dose control Dose control for any element of the pattern has a resolution between 10% and 0.1% of the clearing dose. (Depending on the dwell time.) Scan resolution 16 bit x 16 bit in both X and Y. Step size Writing speed Freely selectable, but minimum possible step size is: field size /65536 (i.e., 16-bit.) Variable from 125 Hz to 4 MHz Field alignment Based on SE image or line scan acquisition using the ET- SE detector. 8-bit A/D conversion with 1 µs sampling time for each pixel. Writing field calibration and correction is performed online after a single calculation step by a matrix of 6 multiplying 16-bit D/A converters. Adjustments are accessible in both axes for offset, scale, and angular orientation. (This method of field alignment does not affect either the accuracy or the speed of any exposure.) Version page 13 of 28

14 3.6.2 SEM inspection mode Types of scanning Raster scan: Multiple non interlaced electron scan speeds TV rate scan with optional sliding or frame averaging Spot mode: Line scan: Scan rotation: Freely defined in X and Y Repetitive scan of line on sample 360 scan rotation at all scan rates Magnification(SEM mode) Image processor Noise reduction: 20 to 400,000 times The image processor allows to store 3 images and process 1. The standard resolution is 702 x 484 pixel and can be upgraded to 1404 x 968 pixel. Pixel and frame averaging 3.7 SEM image display functions Display Image overlays System Menus Image annotation Hardcopy Archiving Image and control menus displayed on 17 colour monitor. Images are integrated via frame grabber hardware Data zones, customized data zones; magnification bar, beam energy, etc. Status and control of main system functions Range of functions available, e.g. text from keyboard Video printer unit Hard disk, floppy disk, network connection (TIFF files) 3.8 Secondary electron (SE) detectors Version page 14 of 28

15 ET-SE Detector Controls Chamber mounted Everhardt-Thornley SE detector with variable acceleration voltage Automatic contrast/brightness with manual override 3.9 Control data system and user interface Lithography Pattern generation and SEM mode operation are based on a networked dual PC data system with the following specifications: SEM control data system Central processor Intel Pentium II or better. Operating system Microsoft Windows NT 4.0 Application software Digital control of lenses, beam voltage, filament and vacuum system. Comprehensive suite of functions to enable highresolution images and data handling thereof. Communications ports Disk drives Networking Display Centronics parallel port and 2 serial ports. Up-to-date hard disk, floppy disk, CD-ROM. Network card RJ45 standard. 17 high resolution monitor Lithography control data system (minimum configuration) Central processor Memory Intel Pentium III / AMD Athlon or better. 128 MB RAM (minimum). Operating system Microsoft Windows NT 4.0 Application software RAITH 150 lithography package. Version page 15 of 28

16 Communications ports Disk drives Centronics parallel port and 2 serial ports. Floppy disk, 15 GB IDE hard disk, and up to date high speed IDE CD-Writer/ROM. Networking Two PCI network cards (BNC/RJ45) standard. One connected to SEM PC and one connected to external house net (if available). Display 19 high resolution CAD-class monitor. Version page 16 of 28

17 4 LITHOGRAPHY SOFTWARE AND SYSTEM CONTROL PACKAGE The software suite is graphically based, 32-bit code that operates under Windows NT. It employs multiple desktops to support distinct lithography tasks and user preferences. The platform consists of a variety of functional modules that also provide a seamless link to the SEM and column control. 4.1 GDSII database Hierarchically organized data base using extended GDSII format which also allows dose information and further special structure types (e.g. single pixel lines, bitmaps and text formats). Externally prepared CAD files in GDSII-, most (AutoCad) DXF- and CIF-format and ASCII data can be converted to the internal GDSII format. 4.2 Viewer/Editor Fully graphical oriented hierarchical operating viewer and editor. This unique approach is based internally on the extended GDSII file format and allows flexible and extremely fast data handling ranging from a single pattern up to complete chip designs with megabyte file lengths. The viewer/editor comprises the following features: View and design of i.e. rectangles, polygons, circles, ellipsoids, lines, dots, paths in one and more process levels and hierarchical layers Creation of ASCII text pattern and related functions (i.e. for documentation of time & dates) Mathematical function generator for arrays of curved lines Generation of hierarchical structures Creating, moving, zooming, deleting, adding, repeating and referencing structures Elementary cell repetition to realize complex repetitive pattern with minimized amount of data Post processing tools as i.e. shrink, frame, overlap removal, etc. Image overlay options on design 4.3 Exposure module Program package for exposing all types of design data directly from the extended GDSII data base. Version page 17 of 28

18 Automatic "on-line" division of arbitrary shaped pattern directly from GDSII format into trapezoids Exposure of all types of arbitrary shaped areas and curves in fast vector scan mode Exposure of single pixel lines and dot arrays Exposure of bitmaps in raster scan mode Selection between a range of exposure modes (meander scan / line scan / scan orientation) Graphical and alphanumerical on-line status control 4.4 Mark recognition and alignment module This module includes the scanning, graphical representation and evaluation of up to four marks per write field at the same time with operator assisted or fully automatic field calibration (see auto align). Free selection, definition and scanning of mark fields with any pixel size Zoom, store, repeat functions for mark scanning and display Manual, semi-automatic and fully-automatic mark recognition and assignment Calculation and implementation of the writing field correction parameters Communication with hardware unit (download multiplying D/A converters) Acquisition and display of a background image 4.5 Sample stage control and alignment The sample stage is under complete digital control and allows fully automated exposure sequences including field stitching and Mix & Match exposures. Alignment to preprocessed chips is supported by simple registration to known global registration marks on the wafer. 4.6 Automatic write field and overlay alignment Detected marks compared with ideal mark reference Deviations from ideal calculated by edge detection technique or cross correlation Mark detection parameters can be optimized by the user Up to four marks in field Version page 18 of 28

19 4.7 Automatic field stitching On line data preparation of hierarchical GDSII layout by fracturing into individual writing fields. Alternatively, preprocessing of large pattern data and direct exposure from file Reduction of beam drift effects in extended exposure runs by automated readjustment procedures employing fixed reference marks. 4.8 Automatic Process Control (APC) module The RAITH 50 system allows to be controlled by a comprehensive set of macro commands and using Java Script (JS). This enables advanced users to build up, save and store versatile operation sequences and i.e. exchange these within the community. Standard macros examples will be delivered with the system. User defined macros in combination with other modules such as auto align and exposure to facilitate automated pattern placement (Mix & Match) on chip and wafer scale. Existing internal macros and commands can still be used. The user written scripts can be edited, debugged and executed directly within a dedicated window on the GUI. Often used sequences can be linked into single button operation. 4.9 Proximity effect correction, simulation and parameter determination The module comprises the following: Pattern post processing for division into meaningful substructures Proximity calculations based on two Gaussian model and methods of Aristov et al. Determination of proximity parameters alpha, beta and eta Proprietary routines which account for the resist development process Correct dose assignment - resulting in evenly spread dose distribution within the complete structure Simulation of pattern exposure including effects from thickness and contrast of resist. Version page 19 of 28

20 4.10 Integrated linewidth control and metrology link Pattern generated by the tool can be checked for achieved line width, pitch and pattern placement applying the following features: Line width and pitch control based on directly measured line scans or retrospectively from acquired images Pattern placement control across single write fields, single chips/dies or across the whole wafer applying the laser interferometric metrology Threshold algorithm and manual assignment of edge locations standard 4.11 Protocol and error handling Actions performed by the operator and the system itself can be documented by a rolling protocol to a logger file. This includes also the documentation of all warnings and error messages within a working session. Critical errors are presented to the operator for evaluation and potential resetting actions Windows-based Help functions All modules, commands and even click-boxes are linked directly to their related helpfiles. Essentially, the entire users manual can be accessed through the various help menus. In a graphically oriented manner these help files inform precisely about the functionality, syntax and operation of the activated feature. In addition to the integrated help menus, the system is delivered with a detailed users manual in hardcopy and software formats Software options: Advanced Metrology Package The Advanced Metrology Package (AMP) is an advanced software suite for performing sample/application specific adaptation linewidth algorithms. The AMP extends the system functionality to provide high performance critical dimension (CD) measurements. It is especially useful for performing measurements on difficult and sensitive samples like resists. (In general, useful on any sample with complex contrast characteristics.) For lithography applications, this package allows for more accurate pattern placement based upon CD measurements performed in "real-time." Version page 20 of 28

21 The software (AMP) is integrated into the RAITH user platform under the Windows NT operating system. It includes an extremely flexible linewidth measurement package based on the AnalySIS software package from SIS (Software Imaging Systems) company. The linewidth detection algorithms can be operated in two modes: (1) as an interactive measurement directly on acquired and stored digital images; and (2) as a remote operated functionality integrated into the RAITH user interface. In the interactive mode, the user is essentially running the software manually. In the remote mode, a DDE connection is made between the RAITH software platform and the SIS software package. The DDE connection provides a conduit through which to send and retrieve data between the two platforms. This seamless integration with the versatile Scan Manager allows one to configure, locate, run and store complete CD measurement sequences. Edge detection and linewidth detection schemes can be applied directly on onedimensional linescans as they are acquired by the RAITH scanning system. The data generated from these measurements can then be handled in subsequent steps within the Positionlist. Linewidth calculation schemes can be edited, tested, stored and preconfigured for remote applications interactively, having access to the following key parameters: Algorithm Types threshold and dual-threshold on single linescans peak-to-peak minimum-to-minimum (and combinations with above) linear regression (Toshiba method with baseline) Functionalities line, pitch, distance Edge Identifier percent threshold for left & right Data Types for algorithms single linescan single lines in images multiple lines in images (Y-average) Edge Smoothing polynomial fit for 1D filtering for 1D and 2D signal averaging in 1D and 2D System Features printout of linescans statistical functionality (mean, sigma, removal of "flyers" and more) Version page 21 of 28

22 data export (e.g., to MS EXCEL or other data processing software) Version page 22 of 28

23 5 ACCEPTANCE TESTS Acceptance procedures and tests will be performed for all major technical specifications. The acceptance will be split into a pre-shipment acceptance and an on-site acceptance. The customer is welcome to attend both. 5.1 Electron beam exposure data Minimum guaranteed linewidth A set of straight lines will be designed and exposed in 100 nm PMMA on Si using a 100 µm exposure field. The width of the lines with best suited exposure dose will be demonstrated to be less than or equal to 80 nm lines and 80 nm spaces (FWHM) Stitching and overlay (mix & match) accuracy The overlay and stitching accuracy in lithography will be demonstrated to be better than or equal to 80 nm (mean + 2 sigma) in a procedure as follows: 1. A special test pattern is exposed in an approx. 100 x 100 micrometer writing field on PMMA and stitched together 25 times, 2. Resist development and processing 3. Mark recognition on the processed structures and a second exposure step of a complementary pattern 4. Resist development and processing of the second pattern 5. Automated pattern placement measurement for overlay and stitching structures 6. Statistical evaluation applying EXCEL or other tools 5.2 SEM mode image resolution SEM mode resolution will be demonstrated on an Au on C test sample, or similar, mounted on a stub holder. At 30 kv operation the image resolution will be shown to be less than or equal to 4 nm - standard grey level definition. Version page 23 of 28

24 6 SITE PREPARATION GUIDE This section is meant to aide in preparing the laboratory room for the installation on the instrument. If additional information is necessary, please inquire. The environmental and utility requirements shall be the responsibility of the customer and shall be provided at the time of installation. Failure to comply with these conditions may adversely affect the performance figures quoted in this document. The optimum results can only be guaranteed if the specified environmental requirements are fulfilled. 6.1 Electrical services The central supply cable comes out near the middle of the pump-stand, with a CENON (32 A) type plug. (See applicable drawings at the end of this chapter.) The power line must be fused by a 25 Amp circuit breaker of fusing characteristic K. A Ground Fault sensing device is also recommended. Main power line 230 V +6% -10%, 50/60 Hz single phase, neutral ground 4 kva power consumption provide a 25 Amp fuse NOTE: Recommendation for U.S. customers; if 230 V cannot be met, inquire about a transformer to boost 208 V input to 230 V. Emergency stop Protective ground A special circuit should be provided for an EPO or Emergency Power Off switch. A power switch for the instrument should be within easy reach, preferably next to the door. The RAITH 50 system is subject to regulations for highvoltage installations. Therefore, it must have a second safety ground connector or an equipotential connection via a separate line of at least 4 mm cross section. Other local provisions may also be in effect. 6.2 Gas services Nitrogen Required for venting the chamber. dry nitrogen (purity about %) 2 liter/minute at 1.2 bar (1.3 bar maximum) Version page 24 of 28

25 connection via PTFE tubes of 6 mm inner diameter Compressed air Required for pneumatic bellows used to support the chamber and to actuate the gun isolation valve. Alternatively, compressed air can be taken from a bottle since consumption to drive the isolation valve is minimal. In normal operation this may be sufficient for up to 6 months. 4-6 bar (static) connection via tubes of 8 mm inner diameter 6.3 Cooling requirements Water supply 2 liter/minute minimum flow rate at a differential pressure of 2 bar between inlet and outlet (overall pressure on system limited to 7 bar maximum) 18 C recommended temperature (permissible range 16 C to 25 C) with regulation to ± 2 C able to maintain cooling capacity of 0.6 kva connections via ½ PVC tubing If using a re-circulating cooling system If cooling from a general water supply line Units may be either air- or water-cooled. Normally each type requires a separate power outlet from the main system (~ 6 A at 230 V or 11 A at 115 V). In either case, recommend the units be set up outside the lab room because air units produce hot air and water units produce noise. Select chillers with care that they operate without vibrations or fluctuations in water pressure, as this affects performance of the lens. Chillers can be purchased thru RAITH as an option. The water line must be pressure controlled and filtered, and is usually drained into an open drain with siphon trap. The tap water consumption is controlled by the system and amounts to approximately 50 liters/hour at maximum cooling power. The water flow must be stopped if the RAITH 50 is switched off completely for a long period of time. The water supply must have the following: main valve water filter 2 manometers pressure regulator magnetic valve ½ nonconductive hose Version page 25 of 28

26 6.4 Room conditions Room size 3.5 m x 5 m with a minimum ceiling height of 2.3 m. (This is regarded as a minimum, suitable only for the instrument and one operator.) Entry doors should be wider or equal to 0.9 m. Recommended to have a 1 m space between system and surrounding walls to aid installation and servicing. Temperature Exhaust The heat output of the instrument is about 4 kw and should be removed by circulating the air. The allowed temperature range for the laboratory is from 20 C to 30 C controlled to ± 0.5. The RAITH 50 uses an oil-free vacuum system. The gas exhausted by the rotary pump during the evacuation of the chamber is drawn off through an exhaust line, which must be placed outside the building. An exhaust filter is often mandatory. Relative air moisture Less than 65 %. Floor vibrations Magnetic fields The velocity of floor vibrations has to be less than 2 µm/sec rms for frequencies observed below 15 Hz. For frequencies above 15 Hz the maximum velocity should not exceed 20 µm/sec rms. Otherwise special equipment should be added (e.g., antivibration platform.) Less than 3 x 10-7 Tesla (= 3 mg) peak-to-peak over the complete Hz frequency range. Also avoid locations subject to varying fields (e.g., near an elevator.)^ Acoustic Noise The acoustic noise should not exceed 40 dba for frequencies below 100 Hz and has to be less than 55 dba for frequencies abouve 100 Hz Version page 26 of 28

27 6.5 Transport and packing Overall system weight is approximately 1,000 kg and will arrive on several shipping pallets. All components are packed into special transport boxes and are secured with plastic foil. Small components, wires, tools, etc., will be packed into paper boxes with foil and are likewise fixed on a pallet. Critical crates are equipped with tilt/tip/shock indicators. Please make note of condition of pallets and crates when shipment arrives. RAITH 50 Top View Version page 27 of 28

28 6.6 Summary of utility and environmental requirements Main power 230 V (U.S. option of 208 V with boost transformer) 3kVA-4kVA consumption dependant on accessories System chiller (water) 230 V, 6 A (or U.S. customers 115 V, 11 A) Nitrogen Compressed air 2 liter/minute at 1.2 bar (0.2 bar over atmospheric) 4-6 bar (static) Ambient temperature C Relative humidity Less than 65 % Floor vibration Magnetic fields Acoustic noise Less than 2 µm/sec rms. at frequencies below 15 Hz Less than 20 µm/sec rms. at frequencies above 15 Hz Less than 3 mg peak-to-peak over Hz range Less than 40 dba at frequencies below 100 Hz Less than 55 dba at frequencies above 100 Hz Version page 28 of 28