EVG 520IS WAFER BONDER SYSTEM OPERATING … Wafer...DOCUMENT: EVG 520IS WAFER BONDING SYSTEM...

DOCUMENT: EVG 520IS WAFER BONDING SYSTEM OPERATING PROCEDURES Version: 1.0

EVG 520IS WAFER BONDER SYSTEM OPERATING MANUAL

Version: 1.0 Feb 2011

UNIVERSITY OF TEXAS AT ARLINGTON

Nanofabrication Research and Teaching

Facility


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TABLE OF CONTENTS

1. Introduction…………………………………………….…………..2

1.1 Scope of Work…………………………………….…......2 1.2 Description…………………………………….…….……3 1.3 Safety……………………………………………....……..3

2. Hardware..............................……………………………….….....5 3. Requirements……………………………………..….….…….…..5

3.1 Training…………………………………….……..…...….5 3.2 System Restrictions………………………...……..…....5

4 Operating Procedures.………………………..…..…………......6 4.1 System Checks………………………….…....…..…..…6 4.2 Preparing system for bonding….…...…….….…..…….8 4.3 Wafer mounting and loading…………..…….……......10 4.4 Wafer unloading………………………………………...14 4.5 System Shutdown……………………………….……...15

5 Recipes…….………………………..…..……………….…..….....16 5.1 Recipe Guidelines......................................................16 5.2 Creating a recipe..................…..................................17 5.3 Editing a recipe..........................................................19 5.4 Nanofab Standard Recipes........................................22 6 Appendix……………………………………………………………27

1.0 INTRODUCTION

1.1 Scope These procedures apply to the EVG 520IS Wafer bonding system. All maintenance should follow the procedures set forth in the manufacturer’s maintenance and operations manuals. This document is for reference only. Users must be trained by Nanofab staff before operating this equipment.


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1.2 Description The EVG 520IS wafer bonding system can create bonded 4” wafer pairs

using thermal, compressive, eutectic, or anodic bonding processes. A variety of substrate materials may be used, but the size of the bonded material is fixed. Only 4” diameter wafers may be processed on this system. The attempted bonding of any material other than 4” diameter wafers will result in damage to the EVG 520IS system. The wafer bonding processes can be performed under vacuum conditions or with N2 purge gas flowing. Highly accurate compressive pressures are attained by the use of a load cell integrated into the system. Accurate vacuum and N2 purge flows are attained through the use of an MFC and pressure control system. The EVG 520IS wafer bonding system can be used in combination with the EVG 620 wafer aligner to produce accurately bonded wafer pairs with wafer to wafer alignment accuracy of approximately 2 microns. The EVG 620 wafer aligner is a separate system and will require user training and authorization before it can be used.

1.3 Safety 1.3.1 This machine is connected to HIGH VOLTAGE. Be very careful and

remain aware of electrical hazards. If you encounter any electrical malfunctions, contact NanoFAB staff immediately

1.3.2 Always stay clear of the opening and closing process chamber lid and the latching mechanisms for the lid. Failure to do so may result in personal injury.

1.3.3 Be aware of the possibility of high temperatures when loading/unloading the bond chuck. This machine can heat bonded wafers to high temperatures (550C). Make sure the upper and lower heater temperatures are < 50 C before opening the process chamber to remove the bonded wafers.

1.3.4 This machine has an EMO (Emergency Off) switch/button mounted on the top panel to the right of the keyboard. The EMO switch should be pressed only in an emergency. An emergency would be fire, smoke, electrocution hazards, or an impending injury to anyone using this particular piece of equipment. If the EMO is pressed notify NanoFAB staff immediately.

1.3.5 Read any posted NanoFAB Engineering Change Notices (ECN) (Fig 1.3.1) for any hardware, process or safety changes before running the tool.


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Fig 1.3.1


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2.0 HARDWARE

2.1 Process Gases – Nitrogen

2.2 DC Anodic bonding voltage – up to 2000 VDC

2.3 Hydraulic system – up to 20 kN force (with Titanium plate)

2.4 Substrate heating – up to 550° C

3.0 REQUIREMENTS

3.1 Training All users must be trained and authorized on the EVG 520IS wafer bonder to use this system. Training is supplied by a Nanofab staff member please contact the tool owner to schedule training.

3.2 System Restrictions 3.2.1 Users must be logged into the EVG computer under their own login

name/password and log out of the computer when finished with the system.

3.2.2 Only 4” diameter wafers may be bonded on this system. No samples or wafers of any other size are allowed to be processed in this system.

3.2.3 A user folder will be issued for each person during system training. Custom user recipes must be stored in the users own folder.

3.2.4 When editing a recipe the user may not increase the bonding pressure to > 5 kN without Nanofab staff approval.

3.2.5 When bonding wafers the proper bonding chuck, pressure plate, and related hardware must be used for the type of process taking place, if you are unsure of this then STOP and consult Nanofab staff.

3.2.6 When changing bonding types only Nanofab staff may change the pressure plate and subsequent hardware.

3.2.7 When using the Quartz pressure plate (Anodic bonding) the maximum pressure during a steady temperature state is 5 kN. During a cooling or heating sequence the maximum pressure is 2 kN for the quartz pressure plate.

3.2.8 When using the solid Titanium pressure plate (Thermo compression bonding) the maximum force that may be used during a steady temperature state is 20 kN. During a cooling or heating sequence the maximum force allowed is 4 kN.


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3.2.9 The bonding chuck must ALWAYS be in left the chamber when the lid is

closed. This is true both with and without wafers present on the chuck. This step is to protect the upper/lower heaters in case the piston is mistakenly lowered with the lid in the closed position.

3.2.10 If you are heating your bonded wafers the cooling step in the recipe must specify a temperature of < 50° C before ending the recipe and venting the chamber.

4 OPERATING PROCEDURES

4.1. System Checks 4.1.1. Ensure that the system computer is ON by viewing the main screen. If

the computer is powered OFF contact Nanofab staff.

4.1.2. Check the written System Logbook and verify no other users are currently running the system.

4.1.3. Check the light tower (Fig 4.1.1) located at the top right-hand side of the system. Ensure that only the GREEN light is illuminated and not flashing, this means the system is in standby. If both the GREEN & YELLOW lights are illuminated then another user may have a process running. If the RED light is illuminated then a fault is present, either correct the system fault or notify NanoFab staff.

Fig 4.1.1


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4.1.4. Log into the main computer by clicking the flashing “Login Here” button located at the lower left of the main EVG software welcome screen (Fig 4.1.2).

Fig 4.1.2

4.1.5. After logging into the computer seven buttons will show up at the bottom of the computer screen. Select the “Jobs” button located at the bottom of the screen and verify that the upper and lower heater temperatures are < 50° C (Fig 4.1.3) and that no process is currently running.

Chamber information

Fig 4.1.3

4.1.6. As long as the system checks are good you may proceed.


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4.2. Preparing System for Bonding

4.2.1. If you have not completed the System Checks in steps 4.1.1 – 4.1.6 then you must complete those before proceeding.

4.2.2. Select the button titled “Recipe” at the bottom portion of the screen. This will pull up the recipe selection screen (Fig 4.2.1). In the upper left corner of the screen select the “File” tab and then select “Open”. This will open a Windows Explorer tab (Fig 4.2.2), now locate your User Folder containing your bonding recipes.

Fig 4.2.1 Fig 4.2.2

4.2.3. Verify that the recipes listed in the left-hand column are your recipes. Select the recipe that you wish to run from the list and verify the parameters shown on the right-hand side of the screen are correct.

4.2.4. Select the “Jobs” button at the bottom of the screen. 4.2.5. Once you are in the Jobs screen select the “Start” button (Fig 4.2.3), a

small tab will open and allow you to enter a Lot ID, then use the drop-down menu to select the recipe that you wish to run (Fig 4.2.4). Once you have selected the recipe you wish to run click the “Ok” button and then STOP. Do not select “Ok” on the second pop-up window that opens. The main chamber is now venting for you to load your sample. Proceed to the next step to begin loading your sample ***Note*** If you mistakenly press “Ok” on the second pop-up window after selecting your recipe you will have to select the “Abort” button on the left-hand side of the screen to stop the recipe. Wait until the system finishes the abort sequence and then begin step 4.2.5 again.


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Fig 4.2.3 Fig 4.2.4

4.2.6. Wait one minute for the main chamber to completely vent. Then press and hold the two green front panel lid open/close buttons (Fig 4.2.5) which are located on the front panel of the system directly below the chamber. You MUST hold these buttons until the lid has fully opened and completely stopped its rearward movement. Failure to hold the buttons until the lid stops moving may result in a system error.

Fig 4.2.5


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4.2.7. Using the bond chuck carrier (Fig 4.2.6) clamp and then move the bonding chuck from the process chamber to the cooling station. Verify the chuck is sitting flat on the cooling platform (Fig 4.2.7), then pull the black release knob on the bond chuck carrier and remove the carrier. If the bond chuck temperature is > 30C you will see the Green LED turn Off and the Red LED turn On while watching the temperature indicator at the rear of the cooling platform. The Red LED will remain On until the bond chuck is < 30C.

Fig 4.2.6 Fig 4.2.7

4.2.8. Ensure that the Cooling station control bar switch labeled “Unload” is up and in the “Unload” position. Press and hold the two buttons labeled “Tool clamp/unload” (Fig 4.2.8) and wait a few seconds for the bond chuck to be fully clamped in the cool station.

Fig 4.2.8

4.3. Wafer Mounting and Loading

4.3.1. The wafer mounting and loading can also be performed on the EVG 620 Wafer aligner and offers a much higher degree of alignment accuracy. Please refer to the EVG 620 Wafer aligner SOP for instructions on mounting and loading wafers with that system. The section that follows only explains how to perform the mounting and loading procedure on the EVG 520IS Wafer bonding system.


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4.3.2. Sit the 4” samples that are to be bonded on the chuck with the flat facing to the rear of the system and the bond surfaces facing each other. If the wafers need to remain separated until the Wafer Bow Pin comes down during processing then the Wafer Flags can be set between the wafers at this point. The wafer Retaining glass and graphite Pressure disk should be installed on top of the two wafer stack (Fig 4.3.1a).

Fig 4.3.1a

4.3.3. Once the bonding stack is set-up properly rotate the Retaining glass

Retention tabs 90 deg. to where they are positioned over the glass. Retention tab rotation is accomplished by rotating the two gray dials located underneath and to the sides of the cooling station (Fig 4.3.1b).

Fig 4.3.1b


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4.3.4. Now press the “Reset” button located on the cooling station control bar (Fig 4.3.2).

Fig 4.3.2

4.3.5. Once the bonding stack is set up properly the total stack height will have to be measured if the Wafer Bow Pin is to be used during process (Anodic Bonding). Contact NanoFab staff to properly set the Stack Height on the system if you are unsure of how this is done. Warning - Failure to properly set the stack height when the Wafer Bow Pin is being used WILL result in catastrophic damage to the system and destroy your sample.

4.3.6. You are now ready to transfer the bonding chuck with your clamped wafers back to the lower bonding platform in the processing chamber. When the bond chuck is cold < 30C you may forego the use of the chuck carrier mechanism and use your gloved hands to perform this task. Verify that the bonding chuck sits completely flat when in the process chamber (Fig 4.3.3). If the chuck is able to rock side-to-side then it is not sitting flat. DO NOT PROCEED until you have verified that the chuck is sitting flat on the lower bonding platform. Warning - Failure to properly seat the bonding chuck WILL result in catastrophic damage to the system and destroy your sample.

Fig 4.3.3

4.3.7. You can now close the chamber lid. Press and hold the two Green Lid Open/Close buttons (Fig 4.2.4) located on the front panel below the process chamber. Make sure that you hold the buttons until the lid has completely closed and all four of the chamber latching mechanisms have


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fully latched. If you release the buttons before the lid has fully closed and latched then it may generate and error when you attempt to start your process.

4.3.8. Now enter your Name in the Lot ID box and enter a Wafer ID to record the process run, when you are done select “Ok” (Fig 4.3.3). The recipe you selected previously from the drop-down menu in step 4.2.5 will now begin.

Fig 4.3.3

4.3.9. You may keep track of your recipe’s progress by monitoring the

chamber display (Fig 4.3.4) in the “Jobs” window. The comments bar at the top of the chamber display shows what recipe is running. The comments box at the bottom of the chamber display shows which step or task is currently running.

Recipe

Fig 4.3.4 Current task

4.3.10. The Yellow and Green lights on the system display tower (Fig 4.1.1)

will remain solidly lit while the recipe is running. When the recipe has completed the Green light will begin flashing.


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4.4. Wafer Unloading

4.4.1. Once the system has completed processing the Green light will begin flashing on the system light tower located at the top of the system. At the same time a “Substrate finished” box (Fig 4.4.1) will also open on the computer screen. The system is now ready to unload.

Fig 4.4.1

4.4.2. Press and hold the two green front panel lid open/close buttons (Fig

4.2.4) which are located on the front panel of the system directly below the chamber. You MUST hold these buttons until the lid has fully opened and completely stopped its rearward movement. Failure to hold the buttons until the lid quits moving may result in a system error.

4.4.3. Using the bond chuck carrier, clamp and move the bonding chuck to

the cooling station (Fig 4.2.6 & 4.2.7). 4.4.4. Monitor the cooling station temperature indicators located to the rear of

the cooling platform. Allow the bond chuck to cool until the Red LED turns Off and the Green LED turns On. The wafers are now < 30C and cool enough to unload.

4.4.5. Ensure that the Cooling station control bar switch labeled “Unload” is

up and in the “Unload” position. Press and hold the two buttons labeled “Tool clamp/unload” (Fig 4.2.7) and wait a few seconds for the bond chuck to be fully clamped in the cool station.

4.4.6. Now rotate the Retaining glass Retention tabs 90 deg. to where they

are not positioned over the glass. Retention tab rotation is accomplished by rotating the two gray dials located underneath and to the sides of the cooling station (Fig 4.3.1).

4.4.7. Remove the wafer retaining glass and graphite pressure disk and

move them to safe storage. Remove your bonded wafers and store them. 4.4.8. Press the “Reset” button on the Cool station control bar (Fig 4.3.2).


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4.4.9. Move the Bond chuck back to the processing chamber. Ensure that the bond chuck is sitting flat on the bonding platform before proceeding. Warning - Failure to properly seat the bonding chuck WILL result in catastrophic damage to the system & bonding chuck.

4.4.10. Press and hold the Green chamber lid Open/Close buttons (Fig 4.2.4)

located on the front of the system below the process chamber. You must hold the buttons until the chamber lid has fully closed and the four latching mechanisms have completed their movement. Failure to hold the open/close buttons until these movements have finished can result in an error.

4.5. System Shutdown

4.5.1. On the system computer select the button titled “Vacuum” at the bottom of the screen. A screen with the system Vacuum map will now open up (Fig 4.5.1).

Fig 4.5.1


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4.5.2. Select the button titled “Pump” directly below the Vacuum map. An option

box will open, select the button labeled “Evacuate High” (Fig 4.5.2) and select “Ok”.

Fig 4.5.2

4.5.3. Monitor the Chamber Pressure reading in the green box in the middle of the vacuum map displayed on the screen. When the pressure < 5.0 e - 3 mBar proceed to the next step.

4.5.4. Once again select the button labeled “Pump” directly beneath the

Vacuum map (Fig 4.5.1). An option box will open, select the button “Evacuate Off” (Fig 4.5.2) and then press “Ok”.

4.5.5. The chamber is now under vacuum and secured. 4.5.6. Select the button labeled “current user:” in the lower left hand corner of

the computer screen, this will take you to the main EVG welcome screen. You are now logged out of the EVG system software.

5 RECIPES

5.1 Recipe Guidelines

5.1.1 Users must store all of their recipes in a personal recipe folder which will be issued during training. Users are NOT allowed to create any additional folders on the system. Any recipes found outside of a user’s personal folder will be deleted by Nanofab staff during file maintenance.

5.1.2 All personal recipe folders should contain two separate personal recipe

folder types inside, one folder for Low pressure < 5kN force (Anodic type) recipes and a second recipe folder for High pressure > 5kN force (Compression type) recipes. This will help to prevent the accidental


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loading of a high pressure recipe when the low pressure quartz pressure plate is installed in the system. Once again this will be setup for the user during training.

5.1.3 The editing a recipe to have a piston force of > 5 kN must be approved by

Nanofab Staff before proceeding.

5.2 Creating a recipe 5.2.1 You must be logged into the EVG system software in order to create or

edit a recipe. Select the “Login Here” button located in the lower left hand corner of the main EVG software welcome screen (Fig 5.1.1), then Login at the prompt.

Fig 5.1.1

5.2.2 Once you are logged into the EVG software select the button titled “Recipes” at the bottom of the screen. This will pull up the recipe selection and editing screen.


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5.2.3 In the upper left corner of the recipes screen select the “File” tab and then select “Open”. This will open a Windows Explorer tab (Fig 5.1.2), now locate your personal recipe folder and double-click the folder to open the recipes. Verify that the recipes listed in the left hand column of the “Recipes” screen are in fact your recipes that were stored on your personal folder. Do not edit any Nanofab recipes.

Fig 5.2.2 5.2.4 To create a new recipe right click on the main recipe folder at the top of

the left-hand column, select the “New Chamber Recipe” option (Fig 5.2.3). Then you will be able to give the new recipe a name.

Fig 5.2.3


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5.2.5 The system will issue a generic name for the new recipe you have created. To rename the new recipe move the cursor over the new recipes name and right-click on the new recipe. Then select the "Rename chamber recipe" option (Fig 5.2.4). Type in a new name for the recipe and then press the "enter" key.

Fig 5.2.4

5.2.6 The new recipe you created will have no entries (or steps) present in the

right hand column it will have to be edited. You may edit the new recipe by following the procedure in section 5.3.

5.3 Editing a recipe

5.3.1 You must login into the EVG system software, select the "Recipes" button, and then locate your recipes located on your USB drive. If unsure of this process follow steps 5.2.1 - 5.2.3 in the previous section then proceed to the next step.


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5.3.2 Once you have located your recipes on your USB drive to begin editing a recipe move the cursor to the left hand column, highlight the recipe you wish to edit by clicking it one time. The parameters associated with the recipe selected will show up in the right hand column (Fig 5.3.1). If there are no parameters then the recipe is a new one that was never set up.

User Recipes Tasks Parameters

Fig 5.3.1

5.3.3 Recipes parameters are edited by left-clicking the task icon desired (Fig 5.3.2) in the center of the "Recipes" screen then dragging that task to the numbered step in the right-hand column where you wish for the step to reside and dropping the task. To identify what task an icon represents position the cursor over the task and a small prompt will identify the task.

Fig 5.3.2


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5.3.4 Once a task has been dropped in the right-hand column a small window will then open (Fig 5.3.3). All of the parameters associated with the task that was selected can then be entered. As an example, if the "Evacuate" task was selected then the selection box that opens will allow you to enter the vacuum pressure setpoint that you wish the system to attain before proceeding to the next step.

Fig 5.3.3

5.3.5 If a task is dropped in the wrong location or if it is necessary to remove an existing task it can be deleted by right-clicking on it and then selecting "Delete Recipecommand" (Fig 5.3.4).

Fig 5.3.4

5.3.6 When the editing of a recipe is complete select the "Save" option at the top of the left hand column of the recipes window, this will store the recipe changes to your personal recipe folder.


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5.4 Nanofab standard recipes 5.4.1 CuSn Eutectic recipe


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5.4.2 AuAu Eutectic


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5.4.3 AuSn Eutectic Bond


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5.4.4 Standard Direct Bond

5.4.5 Standard Direct Bond (w/Pre-vacuum)


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5.4.6 Standard Anodic Bond


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6.0 Appendix I 6.1.1 Wafer Bonding Applications


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6.2.1 Bonding Process Features Chart


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6.1.3 Bonding Process Performance Chart

EVG 520IS WAFER BONDER SYSTEM OPERATING … Wafer...DOCUMENT: EVG 520IS WAFER BONDING SYSTEM...

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