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PREPARED BY: Eric Chang DATE: 09/20/00Jr. Devlp. Engr.

APPROVED BY: Dr. You-Sheng LinMicrolab Manager

MICROLAB OPERATING PROCEDURE

DEKTAK® IIASURFACE PROFILE MEASURING SYSTEM

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Figure 1. System Layout

EXTERNALMONITOR

MAINMONITOR

KEYBOARDSAMPLESTAGE

STYLUS

VIDEO CAMERA

X THUMBWHEEL

FOCUS KNOB

Y THUMBWHEELLEVELINGTHUMBWHEEL

PRINTER

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DEKTAK IIA SURFACE PROFILE MEASURING SYSTEM

1.0 SCOPE

This document establishes the procedures for surface profile measurements using theDektak surface profilometer in the Undergraduate Microfabrication Laboratory (Microlab).

2.0 APPLICABLE DOCUMENTS

Dektak logbookDektak IIA Installation, Operation and Maintenance Manual

3.0 MATERIALS AND EQUIPMENT

Dektak IIA surface profilometer (scanning unit + main monitor & keyboard)External monitor (located above the main monitor) and video cameraThermal printerLeveling waferTweezers

4.0 GENERAL

4.1 Dektak IIA Overview

The Dektak IIA is an advanced surface profile measuring system. It drags a diamond-tipped stylus across the measuring surface, accurately measuring vertical features rangingin height from 50 Å to 131 µm. See Fig. 1 for the system layout.

4.2 Guidelines

The main unit should be ON at all times.

Turn off the main monitor (using the VIDEO key) and the external monitor when not inuse.

DO NOT lower the stylus (∆∇∆∇ key) without a substrate on the sample stage. Alwaysreplace the leveling wafer when you are finished.

Measure only clean samples.

Always raise the stylus before making gross adjustments in the sample position.

DO NOT move a sample during a scan.

If the stylus appears to have debris on the tip, contact Microlab staff.5.0 PROCESS PREPARATION

5.1 Calibration Verification

5.1.1 Check the user logbook to determine that the machine is ok to use. Also checkthe last calibration date. If the calibration was performed more than 2 monthsago, contact Microlab staff.

5.1.2 If needed, turn on the power switches to the main unit (located on the backside),external monitor (in front), and printer (on top). When first powered on, the mainmonitor reads:

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SLOAN DEKTAK IIA REV. SO-DCHECKSUM ERROR. SET POINTS LOST.

Allow the unit to warm-up for 15 minutes after power-on.

5.1.3 If you do not see anything on the main monitor, press the VIDEO key underDISPLAY/STYLUS to switch on the text screen of the main monitor.

5.1.4 Record the date and sample information in the logbook.

5.2 Set/Check Scan Parameters

5.2.1 Press the PROG key under SET-UP on the keyboard.

5.2.2 Program the appropriate scan length, speed, range, and profile. Use the arrowkeys under DIRECTION on the keyboard and the numerical keys to change theparameters. Press ENTER whenever making changes.

Select NO for Auto Leveling.

See Appendix I for detailed information on programming the scan menu.

NOTE: It is important to select an appropriate scan length. Once the scan starts, thestylus cannot be stopped before it reaches the set length. Therefore, neverset the scan length longer than necessary.

6.0 PROCEDURE

6.1 Sample Placement

Sample positioning is achieved by turning the thumbwheels located on the front and sideof the sample stage, as shown in Figure 1. The stage provides full 360° rotation of thesample.

6.1.1 Move the stage forward along the Y-axis, by turning the right thumbwheelclockwise, until your sample can be placed near the center of the stage.

6.1.2 Using tweezers, remove the leveling wafer and place your sample on the centerof the stage.

6.2 Sample Positioning and Viewing

6.2.1 Use the X and Y thumbwheels to move the stage until the sample is positionedbelow the stylus.

6.2.2 Press the ∆∇ ∆∇ key under DISPLAY/STYLUS to lower the stylus. The externalmonitor (above the main monitor) displays the image from the mounted videocamera. Turn the focus knob such that the stylus tip and its reflection are sharp

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and centered on the screen. DO NOT move the stage by a large amount while thestylus is lowered.

6.2.3 Press the ∆∇ ∆∇ key under DISPLAY/STYLUS to raise the stylus. Locate thegeneral area of measurement. Refocus the sample, if necessary.

NOTE: The video image from the camera is rotated 90 degrees clockwise. When thefront thumbwheel is used to move your sample left or right along the X-axis,the image on the external monitor moves up and down respectively.Likewise, when the side thumbwheel is used to move your sample forwardor back along the Y-axis, the image on the monitor moves right and leftacross the screen. The stylus, which scans from front to back, will be seen onthe monitor as moving from left to right.

6.2.4 Lower the stylus again, and use the thumbwheels to CAREFULLY move thefeature to be measured to the right of the stylus tip (looking at the externalmonitor). The scan is toward the positive Y-axis direction (positive X-axis on themonitor). The scan direction CANNOT be changed.

CAUTION: Keep the stylus RETRACTED while moving the sample over long distances.Lower the stylus only when making fine adjustments to find the scan's exactstarting point.

6.2.5 Raise the stylus by pressing the ∆∇ ∆∇ key. The instrument is now ready to make ascan.

6.3 Scan Sample and Measure Surface Profile

6.3.1 Make sure your scan parameters are correct, and press the SCAN key underSET-UP to initiate the scan. On the external monitor, you can see the styluslower and move across the sample surface. On the main monitor, you can see asurface profile trace being generated (vertical vs. horizontal distance on a largescale). When the scan is finished, the plot will be redrawn according to theprogram settings.

6.3.2 If the trace is not level, use cursor leveling (see section 6.4) to redraw the profile.If the trace is at an extreme slope, manual coarse leveling (see section 6.5) isnecessary to obtain accurate results.

6.3.3 If the trace is level, position the R (Reference) cursor at the base of the step andthe M (Measuring) cursor at the top of the step to measure the step height. Pressthe keys labeled R and M under CURSOR to select a cursor. The selected cursoris displayed on the lower-right corner of the main monitor. Use the left and rightarrow keys under DIRECTION to move the cursors. Holding down the FASTkey while moving the cursors makes them travel faster.

The absolute height at each cursor is shown on the screen by R CUR and MCUR, and is followed by the horizontal distance from the starting scan point.VERT shows the vertical distance between the height values at the R and Mcursors. HORIZ shows the horizontal distance between the two cursors.

6.4 Cursor Leveling

If the initial trace is not level, use cursor leveling to redraw the profile.

6.4.1 Position the R (Reference) and M (Measuring) cursors on two points that shouldbe of equal height along the sloping line. Press the keys labeled R and M underCURSOR to select a cursor. The selected cursor is shown on the lower-rightcorner of the main monitor. Use the left and right arrow keys underDIRECTION to move the cursors. Holding down the FAST key while movingthe cursors makes them travel faster.

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6.4.2 Press the LEVEL key under CONTROL and the profile will be redrawn withthe points leveled.

6.4.3 Follow procedure 6.3.3 for measuring the step height.

6.5 Manual Coarse Leveling

Manual coarse leveling is an important aspect of the DEKTAK IIA operation.The closest possible manual leveling will ensure the best instrument performance.

6.5.1 Using either your own sample or the leveling wafer, locate an area of the surfacethat is known to be level, and position it for measuring. See section 6.2 for helpwith sample positioning.

6.5.2 Press the SCAN key under SET-UP.

6.5.3 As the stage is moving and a trace is being generated on the screen, turn theleveling thumbwheel (shown in Fig. 1.) until the profile trace is tracking in ahorizontal line. Clockwise rotation raises the trace and counterclockwise lowersthe trace.

6.5.4 Press SCAN again. The profile must appear completely within the graphicboundaries (with “Range” set to “Auto” in the program menu) to achieve theminimum acceptable manual leveling. If not, repeat the manual levelingprocedure above.

6.5.5 Once the stage is level, proceed to step 6.2 to measure or re-measure yoursample.

NOTE: You may want to adjust the “Range” parameter in the program menu to asmaller scale for finer leveling.

6.6 Printing

The thermal printer can generate a printout of any display on the main monitor. PressingPRINT under DATA on the keyboard will print the entire graphics display.

6.7 Other Useful Functions

The following useful functions are also programmed in the machine:

i. SETTING THE ZERO POINTii. MAGNIFYING A TRACEiii. ARITHMETIC AVERAGE ROUGHNESSiv. MAXIMUM HEIGHTv. AVERAGE HEIGHTvi. AREA-UNDER-THE-CURVEvii. SMOOTHING

See Appendix II in the back of this procedure, or refer to the Dektak IIA Installation,Operation and Maintenance Manual for details.

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6.8 Unload Sample

6.8.1 Making sure the stylus is retracted, move the sample stage outward using the Ythumbwheel until the sample is clear from under the stylus.

6.8.2 Remove the sample with tweezers and load the next sample if applicable (returnto section 6.2).

6.8.3 When finished, replace the leveling wafer on the stage.

6.9 Turn Off the Power

NOTE: The main unit should be ON at all times.

6.9.1 If the profilometer will not be used for a few hours, turn off the power to theexternal monitor and the printer.

6.9.2 Press the VIDEO key under DISPLAY/STYLUS to switch the main monitor tooff mode. Make sure the display is off.

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APPENDIX I

Specifications

Measurement display range: 200 to 655,000 ÅVertical resolution: 5 Å

Scan Menu

Scan ProgramUp to ten programs can be stored in the machine for quick loading of often-used parameters.

Scan LengthScan lengths are available from 50 µµm to 30 mm.

SpeedThree scan speeds are available: Low, Medium, and High. Low speed provides high horizontal resolutionmeasurements (i.e., generates more data points). High speed saves time, but offers lower resolution.Medium speed is most commonly used. The horizontal resolution is tabulated in Table 1.

Table 1. Theoretical Horizontal ResolutionLOW SPEED MEDIUM SPEED HIGH SPEED

SCAN LENGTHIN MICRONS

HORIZONTALRESOLUTION

(µµm/SAMPLE)

NUMBEROF SAMPLES

HORIZONTALRESOLUTION

(µµm/SAMPLE)

NUMBEROF SAMPLES

HORIZONTALRESOLUTION

(µµm/SAMPLE)

NUMBEROF

SAMPLES

50 0.05 1000 0.1 500 0.25 20051-100 0.1 500-1000 0.2 250-500 0.5 100-200101-200 0.2 500-1000 0.4 250-500 1.0 100-200201-500 0.5 400-1000 1.0 200-500 2.5 80-200501-1,000 1.0 500-1000 2.0 250-500 5.0 100-2001,001-2,000 2.0 500-1000 4.0 250-500 10 100-2002,001-5,000 5.0 400-1000 10 200-500 25 80-2005,001-10,000 10 500-1000 20 250-500 50 100-20010,001-20,000 20 500-1000 40 250-500 N/A N/A20,001-30,000 50 400-600 N/A N/A N/A N/A

RangeThis parameter provides a choice between the Auto Ranging feature and a user determined display range.The maximum display range is 655 kÅ. Selecting an Auto Ranging feature automatically ranges the profileto fill 80% of the display.

APPENDIX I (cont.)

ProfileThree different profiles are available, depending upon the sample surface characteristics and themeasurement range to be selected.

Valleys - Provides 90% of the Measurement Range below the zero horizontalgrid line.

Hills and Valleys - Provides 50% of the Measurement Range above the zerohorizontal grid line and 50% below.

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Hills - Provides 90% of the Measurement Range above the zero horizontal gridline.

The profile setting is important. It scales the Measurement Range according to the profile selected. If thesurface characteristics of the sample are unknown, or if the stage or sample is possibly out of level, selectHills and Valleys for most applications.

Auto LevelingThis is used to automatically level a scan where two scan reference points lie on the same plane.

Reference CursorThis sets the horizontal position of the reference cursor and is very useful for measurements on multiple,identical samples or multiple identical measurement locations on the same sample. The cursor position canbe moved later as necessary, so it is not critical to position it at this time.

Measurement CursorThis sets the horizontal position for the measurement cursor in an identical manner to the reference cursor.The measurement cursor should be set at a value greater than the reference cursor.

Reprinted from Dektak IIA Installation, Operation and Maintenance Manual

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APPENDIX IIAPPENDIX II (cont.)

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APPENDIX II (cont.)

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APPENDIX II (cont.)

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APPENDIX II (cont.)

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APPENDIX II (cont.)

APPENDIX II (cont.)

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APPENDIX II (cont.)