Chapter 4.10

ASML DUV Stepper Model 5500/90

(ASML)

1.0 Title

ASML DUV Stepper Model 5500/90

2.0 Purpose

This document outlines necessary information for the operation of the ASML 5500/90 DUV stepper in GL4.

3.0 Scope

ASML 5500/90 model is a fully automated step and repeat camera (stepper), capable of resolving sub-micron features sizes as small as 0.35 µm, in a production environment (vendor specification). The stepper can easily be pushed beyond these limits in a research facility.

4.0 Applicable Documents

4.1 SVG 8800 coat and developer tracks, Chapter 4.1 of the lab manual

4.2 GCA pattern generator, Chapter 3.3 – Appendix II of the lab manual

4.3 ASML application manuals available in the office

4.4 ASML mask generation, Chapter 3.1 – Appendix C of the lab manual

4.5 Cymer company’s (excimer laser type) manual

5.0 Definitions & Process Terminology

5.1 ASML reticle: 6” × 6” quartz plate (mask) at specific thickness (0.25 or 0.15 or 0.12 inches).

5.2 Flash field: Field size of an exposed area at each exposure step (often kept the same size).

5.3 Stepper job: Stepper job (recipe), which defines the flash field size and stepping pattern.

5.4 DUV resist: Photosensitive material designed to image small geometries, upon exposure to UV light [248 nm (ASML), 193 nm and 157 nm wavelengths] followed by proper develop step.

5.5 SMIF Pod: Environmentally enclosed box used to load and unload masks/reticles onto stepper.

5.6 Reticle table: delicate part of the stepper reticle loader compartment, which is used for placing the reticle on the stage aligning the reticle and consequently getting the wafer the mask to be used for exposing wafers.

5.7 Reticle Gripper: This is the fork that enables the machine to automatically load/unload reticles onto machine’s reticle table.

5.8 Advanced reticle management system (ARMS): Provides a means of automatically identifying, retrieving, and placing the desired reticles onto the reticle table.

5.9 Reticle Loader: This unit is in front of the machine. The SMIF pod containing the reticle/s can be placed on its stage for automatic transfer of reticle/s into the machine (reticle table).

5.10 E-chuck: Exposure chuck (E-chuck) is used for stepping the wafers under the exposure column to form the images in the resist layer.

5.11 PM marks: This is a diffraction grating (4 quadrant of parallel line and spaces) that is used to accurately align wafers to mask.

6.0 Safety

6.1 Illumination beam of the ASML 5500/90 stepper is projected through the lens into the wafer stage (exposure chuck). This is a very bright beam that includes intense UV/DUV, much of which is invisible to the eye. Avoid exposure to this beam at the laser source, beam guide or on the machine. Do not defeat any of the interlocks on the machine.

6.2 The stepper performs different tasks such as reticle and stage alignment with a number of low power laser beams. This includes wafer stage helium neon (HeNe) laser (visible, class 2 633 nm), alignment HeNe laser (visible class 3b 633 nm), and level sensor GaAlAs laser diode (not visible class 3b 820 nm). Radiation from these beams can cause eye and/or skin damage. Avoid direct exposure to these beams.

6.3 Many components in the electronic cabinets use 220 V AC, which constitutes a serious hazard. Do not open the electronics cabinets.

6.4 The stepper has moving parts that are well enclosed never the less make sure your hand are off the moving parts, specifically cassette elevator. Do not leave obstacles along the way of moving parts (i.e. broken wafer on the wafer stage).

6.5 Pay attention to “warning signs” posted on different parts of the ASML stepper, beam guide and Cymer laser. <<< DO NOT PLACE ANYTHING ON RETICLE LOADER UNIT! >>>

6.6 Absolutely, do not wipe the reticle stage, the exposure chuck or the reticle table with regular wipe. Particles can travel onto the critical parts of the exposure chuck and reticle loader assembly, hence greatly degrades the performance of the machine. Furthermore, these parts are very expensive and can easily be damaged by improper cleaning procedure. Authorized personnel (ASML representative and trained staff) are the only people allowed to perform exposure chuck clean up. Notify staff, if there are any problems.

6.7 Do not place anything other than reticle SMIF pod on stepper’s reticle loader compartment. This is the area to the right of the operator console (top of the compartment, flat area).

7.0 Statistical/Process Data

7.1 Process logbook at the station.

7.2 Problem and comment section under equipment section of the wand.

7.3 Enable message for ASML stepper.

8.0 General System Overview, Available Recipes, & Equipment Material

8.1 System Descriptions and General Information

The ASML 5500/90 is a 5X reduction camera, capable of step and exposing maximum field size of 21 mm × 21 mm on 6” wafer. ASML steppers utilizes special type of marks to align/expose all your layers. The initial layer, often called “zero layer” are printed and consequently etched into the initial substrate/layer, often at the first step of the fabrication process. This layer etches a specially designed diffraction-grading pattern called pre-alignment marks (PM marks) into the substrate, which should be etched about 1200 Å deep. There are different styles of such marks available for various applications, however for the most part; we only use one type of marks for our fabrication. The ASML machine is comprised of the following main units:

8.1.1 Operator Console. This is a unit that executes the operator commands.

8.1.2 Exposure unit. This is the unit that controls the exposure time for the desired dose energy.

8.1.3 Wafer Transport System. This is a unit that transfers wafers from wafer loader to pre-align and exposure chuck and finally out to wafer receiver station.

8.1.4 Electronic Cabinet. This cabinet controls the power and various functions.

8.1.5 Temperature control unit cabinet (TCU). This unit provides temperature controlled cooling water/air to the system.

8.1.6 AIR conditioning cabinet (AIRCO). This unit provides temperature conditioned clean air to stage and lamp compartments.

8.1.7 Excimer laser and beam expander. These unit manufactured by Cymer company generate and deliver laser beam to the system. This unit utilizes KrF medium that can generate laser light at 248 nm for wafer exposure (12 mj max. pulse energy), which is used to expose pattern on 6” wafers.

8.1.8 Beam delivery system. This unit directs excimer laser from Cymer unit to ASML exposure unit.

8.2 ASML Available Jobs (recipes)

The ASML is a very capable and robust machine, however a reasonable level of training is required to be able to manipulate the machine and/or perform special application task. Therefore, we have provided the users with three different predefined jobs (recipe) that can be used by users to expose their wafers.

8.2.1 Use one of the standard (predefined) jobs listed in the table below, to process your run. Make sure your mask layout can fit inside the area defined by the job. Center your design on your mask.

8.2.2 Make sure that your design is five times larger on your mask than your intended field size (die) on the wafer. ASML 5500/90 is a 5X reduction camera, which can accurately reduce/print mask image on the wafer. Hence, for a die size of 5 mm × 5 mm on the wafers you will need to lay out a 25 mm × 25 mm area on your mask.

Stepper Job	Field size (die size on wafers)	Number of Available Layers
Small_field_5 × 5	5 × 5 mm²	15
Mid_field_10 × 10	10 × 10 mm²	15
Max_field_21 × 21	21 × 21 mm²	15

Table 1 - Standard (Predefined) Stepper Jobs Available for General Use

8.3 Applicable Material, Mask Plates, etc.

8.3.1 Six–inch quartz at specific thickness (250 mil, 150 mil and 120 mil) can be loaded onto this stepper. The UV light transmission in other media other than quartz will render them useless for DUV application (ASML 5500/90). This includes soda lime glass masks, which is currently used on other exposure tools in the lab. Quartz plates at 250 mil (0.25-inch) thickness are highly recommended for high-end application.

8.3.2 Chapter 3.3 of the lab manual (GCA 3600F Pattern Generator) defines the specifics of ASML mask exposure and preparation.

8.3.3 ASML uses specific marks to accurately place the mask onto the reticle table, as well as a set of PM marks to perform wafer to mask alignment procedure. Therefore, mask designers will need to incorporate the ASML marks in their layout. Chapter 3.1 of the lab manual entitled “Mask Generation Using CAD Software”, defines the specifics of this procedure. The “ASML mark design” file is available for general use in a GDS or L-edit format, which is proprietary in nature.

8.3.4 ASML masks can only be automatically loaded onto the stepper by placing the SMIF pod onto the reticle loader unit. This unit has a stage with 3 pins that can accept the SMIF pod in one specific orientation.

8.3.5 There are few reticles at the ASML station that can only be used by the authorized staff and ASML field engineers. These are called “ASML qualification reticles”, which are kept in a separate SMIF pod. <<< DO NOT USE THESE RETICLES, UNLESS OTHERWISE YOU ARE AUTHORIZED/DIRECTED BY Sia Parsa >>>. These reticles must be kept in their designated SMIF pod at all the time, no exceptions.

8.3.6 Asyst reticle loader unit (ALU) is available at the station that can automatically load the reticles into SMIF pods.

Note: Warning! Careful when loading reticle with pellicle in the single smif pod, the 4 prongs in the single smif pod can easily puncture the pellicle. Make sure you approximately center the reticle in the smif pod before lowering it onto the bottom surface.

8.3.7 Specially made wipe not our regular tech-cloth can only be used on ASML stepper. General use wipes not suitable for ASML should never be used on wafer stage, reticle loader and other critical parts of the machine.

9.0 Operating Procedure

The ASML 5500/90 can be logged onto at three different security levels. These are operator, engineering and maintenance levels (modes). Qualified users are only allowed to operate the machine in the operator mode. This is sufficient enough to expose wafers or if absolutely necessary to perform soft shutdown. Do not operate the tool in maintenance or engineering modes, as you may inadvertently alter the machine’s set up or potentially damage this very expensive piece of machinery. Special provision may be made to allow superusers to use the machine in engineering mode and/or generate special application jobs.

There are three standard (predefined) jobs available on the tool. Members can expose various size exposure fields with these jobs. These jobs contain up to 15 layers that can be used to expose just about all the layers lab members will need to fabricate a device. One can use first layer (zero layer) to print the PM marks. These marks (2 or more) will need to get etched into the substrate at initial stage of the fabrication process, defined in Chapter 7.4 of lab the manual (Lam4, recipe 6000). All the following layers will be aligned to these marks. Make sure not to change jobs in the middle of the process as the location of PM marks may be changed on different jobs. You may not be able to align to your initial marks with such an alternative job. Process staff can help you with special application jobs, which may better suite your chip design. You are however encouraged to save your own job on a diskette, and run your job from such a diskette, if so you desired.

An image quality test routine is regularly done by staff to check the performance of the machine (Performance Test). Appendix 1 shows the specification limits for this test, as per ASML’s recommendations.

Note: Before exposing any wafer, make sure that the laser gas fill has been completed within the past 72 hours (check the log book next to the operator console). Also, if the laser light is switched off (light indicator on the operator console off and the message on the screen indicates that laser is in standby), then follow the recommendation in Section 9.3 to turn the laser light source on. Do not do a fast start-up unless you have to.

9.1 Reticle Load / unload Procedure

9.1.1 Log onto the machine (operator mode, see Section 9.2).

9.1.2 Load your reticle/s in the SMIF pod at the reticle loader station (ALU) at the entrance of GLA (table top area). Place the SMIF pod on the reticle loader (elevator), and simultaneously press two buttons on the operator control module. Wait for the elevator to open the box, and bring the reticle cassette down to its loading position. Load your reticle in the cassette and press the same buttons to latch the box.

9.1.3 Grab the SMIF pod by the handle on top and carry it to the stepper with your other hand held below the box (extra precaution to safeguard against accidental unlatching of the SMIF pod).

9.1.4 Place the SMIF pod on top of the reticle loader stage. Make sure the three holes located at the bottom of “SMIF pod” match the stud positions on top of stepper’s “reticle loader” stage.

9.1.5 Click on the material handle icon, top menu bar of the screen (main menu or other screens all have this option).

9.1.6 Select option #3, exchange reticle box on the “material handling” window (see Figure 1 of Appendix).

9.1.7 This will take you to the next material handling screen shown on Figure 2 of Appendix.

9.1.8 Click on “lock” icon. This will prompt the machine to automatically load and read the reticle ID/ID’s available in the pod. No ID’s will be displayed for the reticles that are not bar-coded.

9.1.9 You need to specify an ID for each unnamed slot by clicking on the “overwrite reticle ID’s” button and typing in the desired name. Once done, click on the apply button then accept the screen (top menu bar) (Figure 2 of Appendix).

9.1.10 You can unload the reticles by clicking on the unlock button on the same screen, later.

9.1.11 Do not leave reticles in the machine make sure you have them back in the SMIF pod stored away from the reticle loader area of the machine.

9.2 Logging onto the stepper, exposing PM marks and/or other layers.

9.2.1 Type in user name and password at the operator console. User name and password for the operator mode logging are “OPR” and “OPERATOR”, respectively.

9.2.2 Printing pre-alignment marks (PM), also called “Zero Layer”. Skip to 9.2.3 if the marks have already been processed, then skip to Section 9.2.3.

9.2.2.1 Place the SMIF pod containing “combi” reticle on the stepper.

9.2.2.2 Select the batch control option by clicking the mouse pointer on it (item #2 on the screen).

9.2.2.3 Define the batch by entering the proper job name (need to stick with this job set up for the rest of your layers), and selecting the PM marks as the layer ID. Nominal exposure for the DUV 210 resist is around 30 mJ.

9.2.2.4 Once you have define the parameters, click on “apply bottom” of the screen and accept on top bar menu.

9.2.2.5 This will take you to the next screen (run batch screen). Load your wafers on the input cassette stage (far right stage looking at the back of machine). Make sure to close the cover the cover and the cassette is properly seated on the stage. Initiate the exposure process by clicking on “start batch” button.

9.2.2.6 Once the run is exposed, develop it as in Chapter 4.1 of the lab manual (SVG8800 Developer Track); inspect the marks; if all OK proceed with the etch process. Chapter 7.4 of the lab manual defines the etch process for the PM marks.

9.2.3 Process your device layers following the PM mark (zero layer) process, as follows.

9.2.4 Click on batch control button (option #2) from the main menu. See Figure 3 of Appendix.

9.2.5 Click on “define batch” button (option #1) on the batch control window.

9.2.6 Enter proper values in the parameter fields as per follows (see Figure 5 of Appendix).

9.2.6.1 First enter the batch ID (any entry will do). This is merely used for batch report.

9.2.6.2 Click on the “job name” field and choose your job/recipe from the pull-down list (user-data/job directory) followed by accepting the screen (i.e. “Max_field_21 × 21 Nominal expo sure” job, then click on the accept button, top menu bar. This will take you back to the previous window (define batch screen).

9.2.6.3 Click on “layer ID”, and select process layer from the pull down list.

9.2.6.4 Enter “C” in the “control mode” field. This will put the stepper in the cassette mode. You can select wafer mode “W” for single wafer processing.

9.2.6.5 Batch size is predefined at “1”, unless you are going to mix different types of wafers in the same cassette, then you can change it.

9.2.6.6 Click on batch type button and enter “p” for production. You can change this to F (focus meander) or E (energy test) or M (for matrix), whereby varying exposure, focus or both on your wafers.

9.2.6.7 Image ID is also fixed for all the pre-defined jobs. This means single chip will be exposed on all fields.

9.2.6.8 Place an “asterisk” in reticle ID field for reticles that do not have ID printed on them (masks made on pattern generator in the lab), and then press select. This will take you to the screen shown in Figure 2 of Appendix. Follow the instruction in Sections 9.1.8 and 9.1.9. to load/name your reticle/s, if needed. Click on the slot that contains your reticle, apply and accept the screen. This will put you back on the previous window with your selected reticle.

9.2.6.9 Next enter the exposure values appropriate for your layer (you may need to run and exposure matrix first). Focus and offset is normally zero.

9.2.6.10 Click on apply button, which acts as “return” key followed by accept to move on to the “batch control” screen.

9.2.7 You are ready now ready to start your run (batch). Load your wafers on the input cassette holder (far right stage, looking at the back of the machine). Make sure that the cover is closed and cassette is properly seated on the stage. Initiate the exposure process by clicking on “start batch” button.

9.2.8 Unload your wafer after you are done (computer prompt). Do not leave the reticle in the machine.

9.3 Laser Idle Mode (need to turn on the laser for exposure)

The latest version of the software automatically places the laser in standby, after a short period of stepper idle time (light source indicator will be off on the operator console). This will not allow for you to readily start the next exposure. In such events, you will need to start your run (desired stepper job), and wait for the stepper to go through its initialization procedure, which could take up to 15 minutes. At the end of this period, the stepper should automatically start your batch followed by exposure. The laser light indicator should also be on, at this point. In the event that the light source is still off (light indicator off), as the last option available to turn on the light, you can try turning it on manually by invoking the Fast Startup procedure, as follows:

9.3.1 From Main Menu, click on Startup/Shutdown.

9.3.2 Click on Fast Startup on the next screen.

9.3.3 Wait for the stepper to complete the task before exiting back to Main Menu.

10.0 Troubleshooting Guidelines

11.0 Appendix