The PHI VersaProbe operates with two essential software programs: PHI Summitt and Vacuum Watcher. A third program, MultiPak, handles data reduction.

Transcription

1 PHI VersaProbe Scanning XPS System I. Overview The PHI VersaProbe operates with two essential software programs: PHI Summitt and Vacuum Watcher. A third program, MultiPak, handles data reduction. PHI Summitt controls the movement of the sample stage, the analysis setup and acquisition, and the control of the ion gun and neutralizer gun. Vacuum Watcher is a separate program that interacts with PHI Summitt and is used to load and transfer samples and differentially pump the ion gun for sputtering. Summitt and Watcher should always be open (running) on the instrument. Do not close these programs without specific instructions from a lab supervisor. If Summitt crashes, it can be closed and reopened. If problem persists after restart, contact a lab supervisor. Make sure Summitt is not already open and minimized before opening. Two open versions will cause problems. Never close Watcher. It remains open even if Summitt is restarted. If instructed to restart the computer, open Watcher first, then Summitt. II. Features The VersaProbe XPS is capable of x-ray beam spot sizes from 10um-200um and a High Power setting with a beam spot of roughly 1400x300um. Secondary electron images (SXI) can be acquired to locate specific features to be analyzed. Computer controlled X, Y, Z, Tilt and Rotate stage control. Auto Z alignment for optimization of x-ray impact and electron extraction. Angle-resolved measurements can be done to analyze ultra thin films (with 1 holder only). Sputtering can be done to analyze thicker films or remove surface contamination. System has both Ar+ and C60 sputter guns. Dual beam (electrons and ions) for charge neutralization of insulating samples. 1

2 III. Mounting Samples 1 and 2 mounts are available. CuBe clips or double-sided tape can be used to adhere samples to the mounts. Use the smallest piece of tape possible to avoid excessive outgassing. Silver or Carbon paint (allowed to dry) is also an option for mounting. Molybdenum masks can be secured to avoid using tape or paint. For angle-resolved experiments, must use 1 holder. IV. Sample Introduction (See Figures 1 and 2.) 1. Watcher -> Press Backfill Intro. Will close valve over turbo pump and open N2 gas to fill chamber. Lift cap and place sample onto fork with tongs. For 1 holders, hold tongs with top groove and slide bottom groove onto fork. Check o-ring on underside of cap, remove any dust or fibers with a clean wipe, and replace cap. 2. Watcher -> Press Pump Intro. N2 valve closes, Roughing pump acts on intro chamber, when vacuum is ready, turbo will be opened. A timer starts counting in Watcher. 20 minutes are allowed for roughing, and then a new timer starts for the turbo. Wait for timer to finish and Task Pump Intro complete message in Watcher. The gauge for the Intro chamber will read until ~10-2 Pa and then read 0. While waiting for intro chamber to reach desired vacuum level: Enable the PHI in Badger. (Will allow use of optical microscope and CCD camera on sample.) Set up file for saved data. Summitt -> Push Folder button at bottom left of Acquisition Settings window. Save in C:\Data. Check Summitt to make sure previous user did not leave undesirable settings. (I.e. No sputter is selected, Neutralize is off. In Summitt -> Image window, under SXI/AutoZ tab, make sure Neutralizer and Ion Gun Neut. are deselected if not desired.) Summitt -> Image window: Select desired Xray beam settings to be used later for AutoZ and for acquisition in the SXI/AutoZ and X-Ray tabs. 3. Summitt -> At bottom of Image window, choose Stage tab. Press Intro to move the stage to the home position for sample introduction. An Intro dialog box will open and indicate that the stage is moving. If the X, Y, Z coordinates of the stage are visible in the Summitt Image window, the numbers will be red when the stage is moving. 2

3 When stage has stopped moving, follow instructions in Intro dialog box (see next step below). FIG 1: Vacuum Watcher Intro Procedure FIG 2: Summit Image Window, Stage Tab Intro Procedure (5) (8) (3) 3

4 4. Watcher -> Push Transfer Sample A Task Message window will open. Press Yes to confirm sample transfer. Gate valve (V1) will open. Wait until white line has moved to open position on gate valve to confirm before moving sample. Another Task Message window will open prompting to insert sample. Carefully push transfer rod into chamber by grasping black handle and sliding it until the stop position. Push OK on Task Message Window. Sample should be on fork, positioned just above the stage in the main chamber. 5. Summitt -> Push Up [Z] in the Intro dialog box. The stage will move Z upward to grab the sample holder. The Intro dialog box will indicate that the stage is moving. 6. If the stage has successfully grabbed the sample and is no longer moving, carefully pull the transfer rod out of the chamber to the stop position. 7. The gate valve (V1) will automatically close. If stage is not aligned to the sample correctly, and a problem arises during Up [Z], push Abort in the Intro dialog box and manually drop Z. To drop Z: Summitt Image Window-> type a small number in the Z(mm) box on the Stage tab and push Move. Contact a lab manager for help. 8. Summitt -> In the Intro dialog box, push Set (Sample Inf.) to update sample thickness and holder size, thereby enabling collision protection for the extractor lens and good Z-height alignment. Push OK to close box. Auto Z FIG 3: Summit Image Window, Auto Z FIG 4: Stage Controller 4

5 V. AutoZ Alignment (Figure 3). 1. Manually raise stage until samples are focused in CCD image. Height for a bare holder is 17mm. a. Raise stage to Z= 17- sample thickness (i.e. 16.5mm for typical wafer). b. Summitt -> In Image window, Stage tab, type new value into Z(mm). Push Move button and stage will move. 2. Viewing through glass windows and CCD camera image, translate to desired sample with digital joystick (Stage Controller, Figure 4.). 3. Summitt -> SXI/AutoZ tab in Image window. Pick the desired x-ray settings for AutoZ. 200um file is typical-- larger spot gives better statistics. (HP option is not available for AutoZ.) a. Auto Z viewer should be on and Point should be selected. b. If sample is likely to charge, may need Neutralizer and Ion Gun Neut. See Section VII: Starting the Ion Gun. 4. Summitt -> Image Window, push AutoZ to start routine. If need to stop AutoZ routine, press AutoZ button again. Watch progress counts should increase until maximum. The stage height will rise for routine increments and then decrease and rise again in smaller steps until done. Push Ok and close AutoZ window when finished. a. If final height is not on desired sample, repeat when centered on desired sample. b. If AutoZ routine fails, manually lower Z to a lower starting position (push Move after entering new value) and retry. c. Best result when have more than 1000cps in AutoZ. d. Do not do AutoZ on a tilted sample. AutoZ is already calibrated for tilt. VI. Data Acquisition 1. To perform a survey scan, type SUR into the Region Name box in the Summitt Acquisition Setting window. Change the default parameters as needed. Typical settings include: Pass Energy: 117.4eV (gives 1.5eV energy resolution) Range: eV, or eV if needed Energy Step: 1eV Time/Step: 20ms 1 repeat; 3 total cycles (upper left). 2. To perform a high resolution scan, type desired element and transition into Region Name (i.e. C1s, O1s, Ag3d5 ) a. Press Element Table to open periodic table to select elements/transitions. Push Add for desired transition. b. Change the default parameters as needed. Typical settings include: 5

6 Pass Energy: 23.5eV Range: varies by element, can push Test Acquire to ensure peak is within region. Energy Step: 0.1eV Time/Step: 50ms Repeats: Add repeats to regions that need better statistics. c. For faster option, can choose Unscan at bottom of Summitt-> Acquisition Setting window. 3. Place a check in box at left side of each line to be acquired. 4. Do not collect SUR and high resolution regions at the same time/under same file name. 5. Summitt-> Image Window, XRAY tab, choose the spot size/power to be used for scan. HP or 200um spots give best statistics and most counts, but may need smaller spot for localized area or acquisition within sputtered region. See Figure Summitt-> Acquisition Settings Window (LHS). Push Acquire to start. 7. To use Ion Gun for sputtering or charge compensation, see Section To analyze data, see the MultiPak manual. Choose X-ray spot size FIG 5: Summit Image Window, X-RAY VII. Starting the Ion Gun Neutralization or Sputtering (Figures 6-9) For the purpose of sputtering or neutralizing, must follow steps 1-2e to start the Ion Gun. 1. Watcher -> Push Diff vlv Open, opens V4 to start pumping Ion Gun (will stop pumping on intro chamber). 2. Summitt-> Image window (RHS), Ion Gun tab (FIG 6): a. For charge neutralization, choose Neutralize file under Neutralize heading. 6

7 b. For sputtering, choose desired sputter file. Chart taped to PHI console explains choices. c. Push Standby (will turn on power to sputter gun). d. A dialogue box will open reminding you to push Diff vlv Open. OK. e. On Pfeiffer RVG050 (FIG 7) box near computer monitor, toggle white switch to Set Point. In Ion Gun tab, check Ext.Pressure(mPa) readout and watch until stabilizes ~10mPa. The main chamber pressure will also get worse (1x10-6 ). Choose sputter settings Choose Neutralize file FIG 6: Summit Image Window, Ion Gun FIG 7: Pfeiffer RVG050C Vacuum Control Box 7

8 3. Charge Neutralization a. Summitt-> Image window (RHS), Neutralizer tab (FIG 8). b. Push Standby (will turn on power to electron flood gun). c. Summitt-> Acquisition Settings window (LHS). Under Neutralize, Press ON. Neutralization will begin when spectrum is acquired. d. If need to do AutoZ, check the Neutralize and Ion Gun Neutralize boxes in SXI/AutoZ tab (FIG 3). FIG 8: Summit Image Window, Neutralizer 4. Sputter Modes Manual Sputter o Summitt-> When pressure conditions are ready, pushing Sputter in Ion Gun tab will immediately sputter. o For manual, timed sputter: o choose a low KV sputter file, check timed box, set time, then push Sputter. Depth Profiling (See FIG 9): o Summitt-> Ion gun is in Standby in the Ion Gun tab and desired sputter file is chosen. o Summitt-> Acquisition Setting window -> Check/Enter desired acquisitions. o Summitt-> Acquisition Setting window (LHS)-> Push Alternate in Sputter Mode category. Will open Sputter Setting options below. o Typical Settings: Sputter Time (min)= total time to sputter. 8

9 Interval Time (min)= sputter increments, in units of.5min. Delayed Acq. Time (sec) = Delay before acquisition to allow count rate to stabilize. 3s is typical. Num(Presputter) = How many scans to take before 1 st sputter. 1 is typical. o Now, number of cycles is determined by sputter settings. Add repeats to increase signal for some acquisitions. o Push ACQUIRE to begin depth profile. o The charge neutralizer can be used during depth profiling. FIG 9. Depth Profile Setup 5. To Shut Down Sputtering/Neutralizer a. Summitt-> Acquisition Setting window (LHS)-> Choose No Sputter in Sputter Mode category (FIG 9). b. Summitt-> Acquisition Setting window (LHS)-> Choose Off in Neutralize category (FIG 9). c. Summitt-> Image Window (RHS) -> Ion Gun Tab: Push Off (FIG 6). d. On Pfeiffer RVG050 box (FIG 7), toggle white switch to Limit. Never turn off power to Pfeiffer RVG050! e. Summitt-> Image Window -> Push Off in Neutralizer Tab (FIG 8). 9

10 f. If used neutralizer during AutoZ, go to SXI/AutoZ tab and uncheck Neutralizer and Ion Gun Neut. g. Watcher -> Press Pump Intro so V4 closes and turbo again pumps the intro chamber. VIII. Sample Extraction (See Figures 10-11). 1. Summitt-> Image window-> Press Extract. Sample stage will lower, return to original X, Y and R settings, and then rise to a high Z position. 2. Watcher -> Push Transfer Sample A Task Message window will open. Press Yes to confirm sample transfer. Gate valve (V1) will open. Wait until white line has moved to open position on gate valve to confirm before moving transfer rod. Another Task Message window will open prompting to insert sample. Carefully push transfer rod into chamber and sliding it until the stop position. Fork should slide onto sample holder. Push OK on Task Message Window. 3. Summitt -> Push Down [Z] in the Intro dialog box. The stage will move Z down away from sample holder. The Intro dialog box will indicate that the stage is moving. If the stage is safely below the sample, carefully pull the transfer rod out of the chamber to the stop position. The gate valve (V1) will automatically close. 4. Watcher -> Press Backfill Intro. Will close valve over turbo pump and open N2 gas to fill chamber. With gloves on, remove sample and replace cap. 5. Watcher -> Press Pump Intro. Ensure that Intro chamber is pumped before leaving tool. Disable in Badger. (1) FIG 10: Summit Image Window, Stage Tab Extract Procedure 10

11 FIG 11: Vacuum Watcher Extract procedure (5) (2) (4) 11