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LOGITECH PM5 LAPPING & POLISHING MACHINE

Primary contact: Chih Chen X54593

PREPARED BY: Chih Chen DATE 6-15-2000 Assoc. Devlp. Engr.

ExtensionSuperusers:

Hung Nguyen X57338

Paulo S. Motta X45774

Jeff Yao X45435

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1.0 SCOPE

This document establishes the procedures for lapping and polishing of silicon, GaAs, InPand other substrates in the Nanoelectronics Laboratory.

2.0 APPLICABLE DOCUMENTS

Logitech logbook and maintenance logSystem Component Operation Manuals

3.0 MATERIALS AND EQUIPMENT

Logitech PM5 SystemPrecision JigAutofeed cylinderGlass substrateAbrasive Al2O3 powdersChemcloth, 12” in diameterPolishing Cloth fir planarizationChemlox CMP solutionChemical-resist cylinderColloidal silicaWax-Ocon-195Opticlear-Isopropyl AlcoholGloves, cleanroomCleanroom wipesCleanroom mask

4.0 GENERAL

4.1 Logitech PM5 The Logitech CMP uses abrasive slurry and chemicalsolution to lap and polish silicon, GaAs, InP, and other substrates inNanoelectronics Lab.

4.2 Precision Jig The unit measures the thickness of sample during lapping,and shuts down the machine automatically after lapping the programedamount of material.

4.3 Machine Maintenance Maintaining a smooth and convex plate surface isneeded to obtain uniform lapped surface. Maintaining a clean environmentis necessary to obtain a uniform surface finish. To avoid scratches on theplate surface and exclude agglomerated particles, these steps are to befollowed:

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4.3.1 Pay great attention when placing test blocks and the precision jig onthe lapping plates. Never make scratches or chips on the lappingplates.

4.3.2 Always clean the cylinder, stage, glass substrates and the jigthoroughly and completely whenever changing one slurry toanother.

4.4 Emergency Power Shut Off

4.4.1 Push in the "Stop" button which is located on the front of themachine.

PROCESS PREPARATION

5.1 Sample Mounting Before lapping, samples must be mounted on glass substrates.Samples must be mounted on the flat side of the glass substrate which is indicatedby an arrow marker “∧ “ on the edge of the glass substrate.

5.1.1 Clean the glass substrates with opticlear, then alcohol, and rinse by DIwater. Blow dry or wipe dry with clean room wipes.

5.1.2 Place sample on the substrate facing down. Measure the thickness of thesample by the dial micrometer on the table next to the machine. SeeAPPENDIX Ia for the operation procedure of the dial.

5.1.3 Place the glass substrate on the hotplate and turn the temperature to 100set point (150 for black wax). After ~10 min or when the temperaturereading is 70 to 80°C, proceed to the next step.

5.1.4 Place a very small amount of wax in the center of the glass substrate withthe metal spatula (stored in the tool box). For most applications the whitewax, (ocon-195 in a can at the station), should be used. For very smallsamples or when thinning down to < 20um, the black stick wax may beused.

5.1.5 Spread the wax uniformly on an area slightly larger than the sample to bemounted. Place your sample face down on the wax and slide the sample alittle bit to get uniform wax thickness with the sample ultimately centeredon the substrate.

5.1.6 Apply pressure and/or weight on the sample if necessary. Weight shouldnot be used on soft materials e.g., III-V compounds. Place a piece of filterpaper on the sample and gently place the weight on the paper. Turn thehot plate off and wait for at least 20 minutes.

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5.1.7 Take the substrate off the hotplate. Put it on the table and let it cooldown. Use wiper with Opticlear to clear the wax around the mountedsample.

5.1.8 Measure the thickness of the sample after mounting. Compared with thethickness obtained in step 5.1.2, the wax thickness should be noted.

5.2 Slurry Preparation In order to obtain a reasonable lapping rate and acceptablesurface roughness, a proper abrasive slurry sequence should be determined inadvance.

5.2.1 Check the abrasive size left in the cylinder. If the slurry in the cylinder

is the size you want to use, shake it well before you use. Add moreslurry if needed. The total amount of slurry should NEVER exceedthe grooved line on the cylinder, as indicated by the arrow in Fig. 1.

5.2.2 To make a new slurry, open the cap carefully with the screwdriver in thetool box. Untighten the four screws for the flux controller, as shown inFig. 2. To take the valve out of the cylinder, turn the valve headcounterclockwise. Dump the old slurry into the slurry waste bottle.NEVER DUMP SLURRY DOWN THE SINK. Clean the cylinder,cap, and valve thoroughly. Put the valve back when done.

5.2.3 Make up Al2O3 abrasive slurry of desired particle size by mixing – ml DIwater and 1.5 cups of powders in a beaker. Stir the solution entirely withthe Teflon boat holder in the fume hood. Pour the slurry into the cylinderwith a funnel. Add more water into cylinder until the level reaches thegrooved line. However, keep slurry volume more than half of themaximum to obtain constant feeding rate.

5.2.4 Tighten the cap and close the header completely by turning headerclockwise. Then open it by turning it counterclockwise for about one turn.

5.3 System Setup

5.3.1 Check the slurry waste bottle under the machine is less than 90% full.

5.3.2 Verify the vacuum exhaust at the Magnhelic gauge in fume hood is >0.

5.3.3 Clean the jig thoroughly with clean room wipers and alcohol.

NOTE: Always use DI water and wipers to clean plates, slurry chute, jog holder, andconditioning plates before using them, and always clean them again when switching slurry.

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5.3.4 Put the cylinder on the autofeed stage, making sure that it sits on bothrubber rollers appropriately.

5.3.5 Remove slurry chute, jig holder, and slurry scraper assembly.

5.3.6 Select the proper plate you want to use. The function of the plates istabulated below:

Plate Function Sample MaterialsGrooved Iron Lapping Si/Glass

Glass Lapping / Polishing GaAs, InPStainless Steel w/Pad Polishing/Planarization Oxide/Nitride/Metals

Polyurethane Rough Polshing Silicon/Glass

5.3.7 Install the plate you choose by matching the three pins of the plate to thethree holes on the plate stage. Be careful to keep your hands always in thegroove, so that you do not pinch your fingers, as shown in Fig. 3.

5.3.8 Install slurry chute, jig holder, and slurry scraper assembly, as seen in Fig.4. Please note that the wheels of jig holder never touch the plate.

6.0 PROCEDURE

6.1 Conditioning Plate The purpose of this process is to make the lapping platesmooth, so that the sample can be lapped uniformly. Always use 9 µm or largersize of Al2O3 slurry for conditioning the plates.

NOTE: Use iron conditioning plate for grooved iron plate; Use grooved ironconditioning plate for iron plate; Use grooved glass conditioning plate for glass plate.

6.1.1 Turn on the main power of the machine.

6.1.2 Turn on vacuum by flipping the toggle switch on the vacuum pump locatedunder the machine.

6.1.3 Press “POWER ON/OFF” bottom on the control panel, then press“START” bottom to rotate the plate. Increase the rotation rate to 3 rpmby pressing the “44”bottom.

6.1.4 Press “ABRASIVE AUTOFEED ON/OFF” bottom, the slurry will feedautomatically. Adjust the feeding rate by turning the valve on the cylinderclockwise (decrease) or counterclockwise(increase). Adjust the slurryfeeder, so that the slurry drops at the position of 3 inch away from thecenter of the lapping plate.

6.1.5 When the slurry wets about 10% area of the plate, stop the rotation bypressing “STOP” bottom.

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6.1.6 Place the right “test block” on it very carefully to avoid scratching theplate. The position of the test block is crucial. Its edge should suspendout of the plate for about 0.75 inch. Never adjust such that the outer edgeof the conditioning plate is entirely inside the outer outer edge of thelapping plate. Tight jig holder. Put weight on it carefully, as seen in Fig. 5.

6.1.7. Press “START”, and then the “44” bottom to slowly increase rotationspeed to 2-4 rpm. Check whether the test block and weight are held by thejig holder smoothly and firmly. If not, take the weight and test block out,and then adjust the position of the jig holder. Repeat the procedure 3 to 4to get the right setup.

6.1.8 Increase the speed to 70 rpm(for iron plate, and 50 rpm for glass plate).Condition the plate for 20 minutes.

6.1.9 When done, press “STOP”. Take the weight and test block off. Clean thetest block by DI wafer and wipers. Dry it by wipers or nitrogen blow dry.

6.1.10 Then use the flatness dial to read the flatness of the test block (seeappendix Ib for the instruction of how to operate the dial). Record theflatness on the logbook.

6.2 Programming Lapping Thickness

6.2.1 Unplug the recharge power wire for the Digital Micrometer Unit.

6.2.2 Turn on the power to the SAMPLE MONITOR and the Digitalmicrometer, DG-925, located in the jig.

6.2.3 Press “SET” on the SAMPLE MONITOR. Use “+” and “−” to enter “thethickness, in microns, to be removed”. Press “SET” again.

6.3 Sample Lapping

6.3.1 Put the glass substrate with sample facing up on the vacuum chuck of thejig. Plug the vacuum hose into the vacuum adapter located on the machine.Check to ensure that the glass substrate is held tightly.

6.3.2 Press “START” bottom to rotate the plate. Increase the rotation rate to 3rpm by pressing the “44”bottom.

6.3.3 Press the “ABRASIVE AUTOFEED ON/OFF” to feed slurry.When the slurry wets about 20% area of the plate, stop the rotation bypressing “STOP” bottom. Make sure that there is enough slurry on thearea where jig sits. If a lot of time has elapsed since the plate condition.stops, run the condition block for a few minutes.

6.3.4 Hold the 2nd and 3rd rings of the jig carefully by your fingers, as shown inFig. 6, then flip your wrist and place it on the plate with great caution, asseen in Fig. 7. Release the second ring of the jig after the jig is securely onthe lapping plate.

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6.3.5 Check if the wheels of the jig holder are in the right position, i.e. match thefirst ring of the jig, as seen in Fig. 8. Never move the jig around on theplate, while the sample is down. Make all needed adjustments whileholding the 2nd and 3rd rings together.

6.3.6 Check if the reading on DG-925 is zero. If not, press “RESET”.If it is still not zero, more weight/pressure may be needed.

6.3.7 If weight/pressure adjustment is needed, use one of your hands lifting upthe second ring, and then use the other hand adjusting the weight byrotating the big screw, as illustrated in Fig. 9. Always lift up sample whenadjust weight/ pressure. Turn it clockwise to increase weight orcounterclockwise to reduce weight.

6.3.8 Press “START” and then “ABRASIVE AUTOFEED ON/OFF” to feedslurry. Increase the rotation rate to 2-4 rpm by pressing the “44”bottom.

6.3.9 Turn on slurry sensor to monitor slurry feeding, which locates under the cylinder head. When the slurry feeding rate is too slow, it will shut down the machine to protect sample from being destroyed.

6.3.10 Examine the reading on DG-925. If it is stable, press “RUN” on Sample Monitor. Then increase the speed to 25 - 35 rpm.

6.3.11 Always close the lid during lapping. In particular, for InP, phosphinecomes out during lapping and polishing.

6.3.12 Check the jig position once in a while. The jig may separate from the jig holder.

6.4 Lapping Completion

6.4.1 The machine shuts down automatically once the set thickness is removed.Press power off to silence the beeping.

6.4.2 Turn off the digital micrometer and the sample monitor.

6.4.3 Hold the 2nd and 3rd rings of the jig by your fingers. Take it out verycarefully. Flip it over and place it on the plastic jig rack onthe table, as shown in Fig. 6.

6.4.4 Unplug the vacuum hose from the adapter. Wait for about 20 seconds.Then take the glass substrate out.

6.4.5 If no polishing needed, clean the machine and the jig thoroughly.

6.4.6 Turn off the main power for the machine

6.4.7 Turn off the power for pump.

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6.4.8 Label the cylinder with the slurry size and the date made.

6.4.9 Recharge the battery of the Digital Micrometer Unit by plug in the 9V DCpower adapter.

6.4.10 Fill out the logbook completely.

6.4.11 If silicon carbon or cerium oxide abrasive is used, make a note on theslurry waste container.

6.4.12 If polishing is required, go to section 7.0. If not, go to Section 9.0for sample removal.

7.0 POLISHING

When a very smooth and reflective surface are required (Ra<100nm), polishing is needed. Prior tothe polishing, the sample has to be lapped by 9 µm (or smaller) abrasive slurry. However, thedigital micrometer does not work during polishing because of the soft polishing pad. Measuring thethickness of the sample once in a while to determine the polishing rate, is required.

If only rough polishing is needed, please see Section 7.2.

7.1 Plate and Polishing Solution Preparation.

7.1.1 Check the note on the stainless steel plate for the materials lapped andpolishing solution used in the previous run. If it is compatible with thematerial and polishing solution you are going to use, use the old polishingpad if possible.

7.1.2 If not, remove the polishing pad by peeling the pad off the plate. Then gluea new one (Chemcloth, 12” in diameter, black in color) on the plate.

7.1.3 Select the proper polishing solution. For Si, use colloidal silica. For GaAsand InP , use Chemlox CMP solution. The colloidal silica is stored in thecabinet for solvent behind the CMP machine.

7.1.4 Select the proper container for polishing solution. Use plastic container forcolloidal silica, which is stored in fume hood next to the CMP machine.Use the cylinder with PLASTIC VALVE for Chemlox CMP solution.

NOTE: DO NOT USE THE CYLINDER WITH METAL VALVE FOR CHEMLOX ORCOLLOIDAL SILICA SOLUTION. THE CYLINDER IS NOT CHEMICALLYRESISTANT.

NOTE: NEVER STORE COLLOIDAL SILICA IN THE PLASTIC CONTAINER OVERONE DAY. DUMP THE REMAINING SOLUTION INTO THE WASTE BOTTLEWHEN DONE.

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7.1.5 Repeat procedures 5.3.1 to 5.3.8 to setup polishing system.

7.1.6 Setting up the Sweeping Arm as follows to achieve better surfacefinishing.

7.1.6.1 Press Sweeping Arm button on the LCD screen.

7.1.6.2 Choose SYSChecks button. The screen should show “System Checks in Progress”.

7.1.6.3 Press Continue button when the system checks are done.

7.1.6.4 Press Edit button.

7.1.6.5 Set Inner Sweep Limit by using “ + “ and “–“ buttons.The lower the number is; the wider the arm sweeps.

7.1.6.6 Choose Next button to go to Outer Sweep limit setting. Adjustrange by using “ + “ and “–“ buttons, so that the sample alwaysstays on lapping plate during sweeping. The higher the number is,the wider the arm sweeps.

7.1.6.7 Press Next button to go to sweep speed setting. Set the speed toapproximately 70%.

7.1.6.8 Press Exit button to exit the Sweeping Arm setting.

7.1.7 Follow the procedure from 6.3.1 to 6.3.12. Skip procedures for using thedigital micrometer (6.3.6, 6.3.8, and 6.3.9).

7.1.8 Press Sweeping Arm button to start sweeping. Adjust the sweep amplitudeand speed if needed.

7.1.9 Press “Exit” button when the polishing is done.

7.1.10 For the purpose of disposing the slurry waste, make a note on the sheet attached to the waste container when colloidal silica or Chemlox solution is used.

7.1.11 Clean the plate and the polishing pad completely. Leave a note on thepolishing plate underside for the materials lapped and polishing solutionused.

7.1.12 Clean the machine and jig thoroughly.

7.1.13 Fill out another record in the logbook for polishing.

7.1.14 Go to Section 9.0 for sample removal.

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7.2 Rough Polshing by Polyurethane Plate

Polyurethane plate with colloidal silica solution can be employed to coarselyPolish silicon or glass.

7.2.1 Conditioning plate.

Before polishing the plate, the plate needs to be conditioned by the stainless steel test block with blades.

7.2.1.1 Follow the procedures from 5.3.1 to 5.3.8 to setup polishingsystem using the Polyurethane plate with the test block.

7.2.1.2 Spread water on the plate by a wash bottle. Make sure that the amount of water is enough to wet all the surface of the plate.

7.2.1.3 Put the test block on the plate, and hold it by jig holder.

7.2.1.4 Spread water on the plate by a bottle. Make sure that water wetall the surface all the time during the conditioning process.

7.2.1.5 Turn on the main power of the machine.

7.2.1.6 Press “POWER ON/OFF” bottom on the control panel, then press “START” bottom to rotate the plate. Increase the rotation rate to 3 rpm by pressing the “44”bottom.

7.2.1.7 Check whether the test block and weight are held by the jig holder smoothly and firmly. If not, take the weight and test block out, and then adjust the position of the jig holder

7.2.1.8 Increase the speed to 35 rpm. Condition the plate for 3 to 5 minutes. Spread DI water constantly to keep the surface of the plate wet.

7.2.1.9 When done, press “STOP”. Take the test block off. Clean the test block by DI wafer and wipers. Dry it by wipers or nitrogen blow dry.

7.2.2 Rough PolishingUse colloidal silica for polishing silicon; while cerium oxide forpolishing glass.

7.2.2.1 Select the proper polishing solution. Follow the procedure inSection 7.1.

8.0 Planarization:

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Oxide, nitride, or metals can be planarized by the following procedure:

8.1 Use the stainless steel lapping plate with PANMA 12” DP-PAN polishing cloth.

8.2 Following the procedure in Section 7.1. Use colloidal silica for planarization.

9.0 SAMPLE REMOVAL

Samples may be removed either by melting or dissolving method.

9.1 Melting method When SILICON samples are thicker than 200 µm, the samplemay be taken off the glass plate by melting the wax on a hotplate.

9.1.1 Place glass substrate on the hotplate with sample facing up. Turn the temperature to 110 set point for white wax ( 160 for black wax).

9.1.2 Wait for about 10 minutes. Use tweezers to push the edge of the sample to slide it off the glass substrate.

9.1.3 Clean the sample and the substrate by immersing them into the Opticlear solution stored in the fume hood next to the machine, followed by alcohol and DI water rinse.

9.2 Dissolving method For brittle materials, such as thinner Si samples, GaAs, orInP, it is recommended to use the Opticlear solution to dissolve the wax laterally.

9.2.1 Use the beaker labeled “Opticlear” in the fume hood next to the machine. Place the glass substrate on the teflon ring in the beaker with sample facing down. Make sure that the sample does not touch the teflon ring.

9.2.2 Make sure that there is enough Opticlear solution, so that the solutioncovers the sample. Cover the beaker with a petri-dish lid.

9.2.3 The sample will drop into the solution when done. It will take few to tensof hours, depending on the sample size.

9.2.4 Clean the sample and glass substrate by alcohol and DI water.

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Fig. 1 The cylinder

ValveCap

Max

Fig. 2 Cylinder cleaning

Groove

Fig. 3 Install a lapping plate on the machine. Fig. 4 System setup.

Slurry feeder

Jig holder

RubberCleaningpad

Lappingplate

Cylinder

Condititonplate

Weight

Fig. 5 Conditioning lapping plate.

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Fig. 6 Holding the jig by press the 2nd

and 3rd rings together.Fig. 7 Placing the jig on the lapping plate

2nd ring

3rd ring

Fig. 8

Fig. 8 The proper position of the jig on the lapping plate

Fig. 9 Adjusting the weight on sample

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APPENDIX I

a. Operation Procedure for Measuring Sample Thickness Using a Dial

a.1 Lift the tip up carefully by pulling the knob on the dial. Place the glasssubstrate with sample on it below the tip, so that when the tip is released, itlands on glass substrate, not on sample.

a.2 Rotate the outer ring of the dial. Zero the height by matching the outerindicator to zero.

a.3 Pull the tip up again and move the glass substrate, so that the sample isbelow the tip. Release the tip very slowly and carefully. Read the outerscale for thickness of the sample. The smallest unit in the outer scalerepresents ten microns.

b. Operation Procedure for Measuring Surface Flatness of a Conditioned LappingPlate.

b.1 Move the flatness dial slightly around the flat standard to seat the tip. Zerothe dial if needed.

b.2 Place the test block up side down on the weight.

b.3 Use one finger to raise the tip by lightly pressing the handle above thedial before taking the dial off the standard. Take it off from the standard.Place it on the conditioned plate. Release the handle very carefully untilthe probe touches the plate. Move it around and read the flatness. Thesmallest scale on the dial is two microns. The smallest scale on the outerdial is two microns.