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CMP System SOP

1. Scope

1.1 This document provides the operating procedures for the Strasbaugh 6EC Chemical Mechanical Planarization System.

2. Table of Contents1. Scope...........................................................................................................................................................12. Table of Contents........................................................................................................................................13. Reference Documents.................................................................................................................................1

3.1 Referenced within this Document.........................................................................................................14. Equipment and/or Materials.......................................................................................................................15. Safety...........................................................................................................................................................26. System Overview.........................................................................................................................................27. Process Model.............................................................................................................................................38. Recipe Procedure.........................................................................................................................................39. Setup Procedure..........................................................................................................................................410. Polishing Procedure.....................................................................................................................................611. System Clean Up and Idle Procedure...........................................................................................................712. Troubleshooting..........................................................................................................................................713. Shutdown Procedure...................................................................................................................................814. Revision History...........................................................................................................................................8

Figure 1, CMP Overview...........................................................................................................................................2Figure 2, Valve Locations..........................................................................................................................................4Figure 3, Set Up Page................................................................................................................................................5Figure 4, Auto Page (Conditioning)...........................................................................................................................5Figure 5, Manual Page..............................................................................................................................................6Figure 6, Auto Page (Polishing).................................................................................................................................7

Table 1, Default Recipe Parameters.........................................................................................................................3

3. Reference Documents

3.1 Referenced within this Document

3.1.1 None

3.2 External Documents

3.2.1 None

4. Equipment and/or Materials

4.1 Wafer/Sample

4.2 Pad Conditioner

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4.3 Slurry

4.4 DI Water

4.5 Compressed Air

5. Safety

5.1 Follow all Nanofab safety procedures.

5.2 You must have recipe approval by Nanofab staff and be trained to use the system.

5.3 Visually inspect the wafer to be polished. Any fragile or chipped wafer should not be polished.

5.4 Opening the front doors or side panels during a process will interrupt and halt the process.

6. System Overview

6.1 Chemical Mechanical Polishing (CMP) is a technique that is used to planarize a film or structure by chemically softening the surface followed by removal of the softened material using mechanical abrasive action.

Figure 1, CMP Overview

6.2 Components

6.2.1 Carrier: applies down force to the backside of the wafer during polishing. It rotates at a set RPM during the polishing.

6.2.2 Backing Film: applies pressure through the holes on the film during the polishing that allows to manipulate the polishing profile. It also applies vacuum to lift up the wafer when the polishing is completed.

6.2.3 Retainer Ring: Restrains the wafer within the carrier during polishing.

6.2.4 Pad Conditioner: constantly refreshes the surface of the pad and prevents the pad from glazing.

6.2.5 Pad: stack of IC1000 (rigid micro-porous cast polyurethane) and Suba IV (urethane impregnated polyester felt).

6.2.6 Slurry: consists of small, abrasive particles (general inorganic oxides) of specific shape and size (typically 10-100nm) suspended in aqueous solution.

6.2.7 Platen: made of SiC or Aluminum, it rotates at a set RPM during polishing and maintains constant temperature through circulating cooling water.

CAUTION

You must have your recipe approved by Nanofab staff before you use it. An incorrect recipe could cause wafer breakage and system damage.

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7. Process Model

7.1 The Preston equation is the model for CMP: Removal rate = Kp*P*V

7.1.1 Kp = Preston’s coefficient

7.1.2 P = Pressure

7.1.3 V = Linear velocity of the wafer relative to the polishing pad

In order to increase the polishing rate, a conventional way is to increase down force (pressure) or table RPM.

8. Recipe Procedure

8.1 Use the recipe template below and only change the following four parameters, as needed:

8.1.1 Down force

8.1.2 Table rotation

8.1.3 Chuck (carrier) rotation

8.1.4 Slurry type

8.2 Make sure ring force is set at 2 psi or the wafer will slip out.

NOTE: It is not recommended to polish a single wafer too long. Keep polishing time under 2 minutes. You can increase the polishing rate by increasing the table and carrier RPM.

DI H2O Valve

CDA Valve

Pump Valve

Figure , Valve Locations

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Table 1, Default Recipe Parameters

9. Setup Procedure

9.1 Press the green MACHINE ON button to power up the tool.

9.2 Turn on the DI water valve. See Error: Reference source not found.

9.3 Turn on the CDA valves. See Error: Reference source not found.

9.4 Open the Pump valve for your desired slurry. See Error: Reference source not found.

NOTE: Slurry 1 = Ultrasol. Slurry 2 = Fujimi. Ultrasol will polish oxide and polySi at approximately the same rate. The Fujimi will polish oxide approximately twice as fast as polySi.

9.5 Log in.

9.5.1 Enter username 6EC with no password.

9.6 Select Set Up from the drop down menu. See Figure 2, Set Up Page.

9.7 Check “Pad Conditioner Enabled” box. See Figure 2.

9.8 Click “Home Pad Conditioner”. See Figure 2.

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9.8.1 Wait for the pad conditioner to home.

Figure 2, Set Up Page

9.9 Rinse the large white CMP pad with the hand sprayer.

9.10 Go to “Recipe” submenu on the drop down menu.

9.11 Go to the NAME drop down menu.

9.11.1 Select recipe “break-in”.

Figure 3, Auto Page (Conditioning)

9.12 Go to “Auto” submenu.

9.12.1 You will be asked if it is ok to download the recipe, click yes.

9.13 Under “Auto” submenu, click “Start Conditioning”. See Figure 3, Auto Page (Conditioning).

Drop Down Menu

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NOTE: The conditioning process takes about 10 minutes. (You are only required to do this when the tool has been idle over 2 hours. You do not need to do this if the pad is wet or you are continuously running the tool.)

9.14 Go to “Manual” submenu.

9.15 Set the flow rate of the slurry at 150 ml/min. See Figure 4, Manual Page.

9.16 Purge the slurry by turning on the slurry pump by clicking the pump image (the two circles underneath Slurry 1 or Slurry 2).

NOTE: The circle will turn blue indicating the slurry is flowing.

9.17 Wait 15 seconds, then click on the circles again to turn off the slurry.

9.18 After flushing the slurry, rinse the pad with the DI water hand sprayer.

Figure 4, Manual Page

10. Polishing Procedure

10.1 Open the door and place the wafer FACEDOWN on the load chuck.

10.2 Close the door.

10.3 Go to “Recipe” submenu.

10.4 Select the polishing recipe.

10.5 Click on the “Auto” submenu.

10.5.1 You will be asked if it is okay to download the recipe, click yes.

10.6 Check the wafer chuck vacuum pressure. It should read at least 450. If not, contact Nanofab staff.

10.7 Under “Auto” submenu, click “Start Polishing”. See Figure 5, Auto Page (Polishing).

10.8 During the polishing, watch the polishing head carefully. Keep your hand on the re emergency off button during polishing. Press the red EMO button on the front of the tool right away if the wafer slips out.

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10.9 If the head fails to pick up your wafer, click on Stop and contact Nanofab staff.

10.10 DO NOT open the doors until the carrier unloads the wafer at the load chuck AND goes back to the platen.

10.11 Open the door and pick up the wafer. Quickly rinse the wafer with the hand sprayer. Close the doors.

10.12 The conditioner will automatically start the ex-situ conditioning. When the ex-situ conditioning is complete, start the next run if needed.

Figure 5, Auto Page (Polishing)

11. System Clean Up and Idle Procedure

11.1 THOUROGHLY rinse and wipe down the carrier outer ring, load chuck, and polishing pad.

11.2 Gently wipe down touch screen with clean wipe and DI water.

11.3 Purge the slurry tubing by switching the valve near the pump above the slurry tank to DI input.

11.4 Run DI water through slurry tube for 5 minutes using the “Manual” menu screen.

11.5 When you complete all the runs, select “Wet Idle” from the drop down menu.

11.6 Make sure that only the “Table Rinse” box is checked.

11.7 Press the “Start Wet Rinse” button on the upper left side of the screen.

11.8 Leave the system in this mode so that the polishing pad will remain wet. Do not turn off the system.

12. Troubleshooting

12.1 Vacuum problems (Head won’t pick up wafer):

12.1.1 Check the orange pressure regulator on the back of the system.

12.1.2 Flush the head.

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12.1.2.1 Stop vac

12.1.2.2 Lift up head under manual menu

12.1.2.3 Back flush

12.1.2.4 Blow off

12.1.3 Check black rubber sealing ring around white part of wafer chuck.

12.1.4 Center wafer.

12.2 Wafer slipping out during polishing:

12.2.1 Check to make sure there are no particles on the polishing pad.

12.2.2 Turn down backpressure.

13. Shutdown Procedure

13.1 When you complete all the runs, select “Exit” to quit the program.

13.2 Press Start > Shut Down to exit Windows.

13.3 Press the red EMERG STOP button to power off the tool.

13.4 Turn off the DI water valve.

13.5 Turn off the CDA valves.

13.6 Turn off the Pump valve for the slurry.

13.7 Leave the slurry agitator/stirrer running at 1000 RPM.

14. Revision History

Rev Date Originator Description of Changes

1 16 Apr 2010 Sam Bell2 19 Nov 2010 Sam Bell Added 8.2, Table 1 Ring Force changed to 2