heidelberg dwl66 laser writer sop - princeton university

Tool owner: Roman Akhmechet, [email protected], x 8‐0468 Backup: Eric Mills, [email protected], x 8‐4626,

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Heidelberg DWL66 Laser Writer Standard Operating Procedure

QUICK GUIDE

PROCEDURE OVERVIEW 1. Write head 2. Convert user layout file 3. Load sample 4. Using Basic Mode 5. Heidelberg Global alignment 6. Top‐side Beam offset calibration 7. Optical offset fix

CRITICAL PRECAUTIONS AND COMMON MISTAKES

Place your sample on stage before setting up exposure

Never touch the interferometer’s mirrors with your bare hands

Never open coverlid when an exposure job is running (you cannot resume it)

Write head center to the edge of your substrate must be ≥ 5 mm

Only users with legitimate need can mount/use/unmount 2 mm write head after training

and authorization by tool owner. The default write head is 10 mm.

Before you start

To purchase any masks/holders from MNFL, remember to fill in on the LOG Book. Preparation:

Pattern Files: GDSII, CIF, DXF, GERBER, or BMP (grayscale)

Samples: Fresh photomasks (MNFL supplies standard Cr masks with soda lime glass plates, both 4 inch and 5 inch in size, manufactured by Nanofilm) or substrate coated with photoresists (substrate OD must be ≥ 10 mm).

Tool condition for the next user Stage free of sample.

Return to default condition: 10 mm lens and 25 % filter, if any change made during

exposure.

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TOOL OVERVIEW

The Heidelberg DWL 66+ is a high resolution pattern generator for mask making and direct writing. Its

capabilities and flexibility make it an ideal lithographic tool for research. It uses acousto‐optic modulators

to adjust the laser intensity, and acousto‐optic deflectors to scan the beam. During an exposure, only the

stage moves. The substrate is held down on the stage by vacuum and moves in the x‐y plane. Its position

is constantly monitored by an interferometer system with a resolution of 10 nm.

The optical setup utilizes a single‐mode diode laser ( = 405 nm) as its light source. It can expose both 2D

and 3D structures (e.g. gray scale lithography with thick photoresists). There are two write heads available:

2 mm & 10 mm. Both heads are equipped with pneumatic sensor and optical sensor for auto focus. In

term of resolution, the 2 mm write head can achieve a minimum feature size of ~650 nm, the 10 mm head

can achieve a minimum feature size of ~1.4 m.

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FULL PROCEDURE

A) Write head

Write head Critical dimension Write speed

2 mm ~0.8 um 6 mm2/min

10 mm ~1.8 um 145 mm2/min

Only users with legitimate need can mount/use/unmount 2 mm write head after training and

authorization by tool owner. The default write head is 10 mm.

B) Convert user layout file

1. Use USB memory stick to transfer layout file and upload file to its corresponding folder shortcut on desktop (gdsii, cif, dxf or gerber). Note: if using gdsii, make sure the .gds is lower case in file name

2. Double click conversion icon on desktop to open GUI HIMT Convert window, select “File/New job” to create a new job. Job Name Guidelines: The job name should have no hyphens or spaces. There is a limit of 12 characters in the name. Please use your NEMO account name as first part of the job name. For an existing job, select “File/Load job” to load an existing job.

3. Under Source File, click “Add”, select

the file type to pick your file, a new

window will pop up with options

depending on the file type. Select the

correct structure/cell and layer number,

and then click “Create Default”. The

Main Status window should state No

Warnings, No Errors if the CAD file

loaded successfully

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4. Select the correct structure/cell and

layer number. These come from your

CAD and depend on how many layers

you have, what their GDS numbers are,

and what you named your cells. When

finished selecting cells and layers, click

“Create Default”.

5. The Main Status window should state

No Warnings, No Errors if the CAD file

loaded successfully

6. Click the checkbox “TCL view” to turn it

on. 7. Click “VIEWER” to inspect pattern with

HIMT Viewer.

8. You can click Fill button to fill in the areas that will be exposed. You can navigate around and zoom in and out. When done with the views, use the Exit button to close the window

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9. Select the correct “Write Lens” (Must

be the same as what is mounted on

tool.)

10. In the “Justification” tab, select “Automatic Centering” to center your pattern design. For masks also select “Mirror” at y to flip the design.

11. “Expose Options” tab has additional options for inversion and XOR functions, as well as CD biasing

12. Click “Complete Tasks” at the bottom,

then save the job. Click “Expose Offline”. Note: if you receive an error, please check that the name of your job complies with all of the guidelines from step 2.

13. Once the file transfer is finished, click “Finish” to complete file transfer.

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C) Load Substrate

Open the sash and turn on the light.

Open the filter panel and install the

correct filter for your process.

Place your sample on the center of

the stage. The sample must cover the

center holes because that is where

automatic focus occurs.

Pay attention to the coordinate

system inside the tool. (Positive Y to

the left, positive X away from the sash

and towards the back)

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Adjust white screws to open vacuum

holes appropriate to your sample.

From Right to Left, opening more

screws will increase how far from

center the vacuum is pulled

Follow the guide below to open the

right screws for your sample size. Ex:

for 5 mm chip, place it in the very

center and only open the rightmost

screw

Turn on the vacuum using BOTH black

knobs.

Note: In this tool, vertical is off and

horizontal is on

Close the sash and turn off the light

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D) Set up an exposure job and expose pattern using exposure wizard in basic user mode

Basic mode

1. Double click on Lithography icon on

desktop to prompt Lithography login

window. If the login window is ready skip

prior step. Login by choosing username:

DWL66+ Basic and password: basic66.

(If the exposure wizard does not appear,

click Wizardry ‐> expose wizard)

2. Switch to the correct “convertPC” tab on the top

3. Click on “Update” at the bottom left to refresh files.

4. Click on “+” to populate “General” folder and double click your job file to prompt Exposure Parameter window.

5. Find your design and double click it. This will take you to the parameter start step.

6. Select your parameters: ◦ Laser power should stay at 120 ◦ Choose intensity for your process ◦ Choose focusing mode: pneumatic

or optical ◦ Choose Focus offset setting

specific to your process ◦ Under “Automatic Centering”,

choose whether to center the job on your sample (PlateCenter for rectangular substrates, WaferCenter for wafers)

◦ Make sure “Laser Mode after Exposure” is Default

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7. Make sure your substrate is on the stage,

then click “Start Exposure” button at

bottom.

8. When the pop‐up shows up asking to load

the substrate, click “Ok”

9. NOTE: if there is another pop‐up asking to

mount the correct device, make sure the

correct write head is mounted on the tool,

and acknowledge by pressing “OK”

10. The tool will automatically focus, center

the sample, and perform the exposure.

11. When the exposure is complete, click “Ok”

in the pop‐up and unload your substrate.

12. When finished do not close the software. Instead, press File in the upper left corner, and “Change user” to logoff.

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APPENDIX A: GLOBAL ALIGNMENT

You must be trained by staff to use advanced features. This section describes procedure to perform

global alignment for rotation and translation of whole array to sample. You may need to perform beam

offset calibration if the results of alignment are poor. Contact staff with questions.

Note: if camera window is not present, open it by going to Devices ‐> Vision ‐> Camera and click green

“Live” button

1. Log in as User instead of Basic

2. Set up desired filter and write head. Place your sample on chuck with appropriate vacuum

3. On left in Job tab, select your job array or create a new one. Drag your design, modify array properties. You can use a single cell, or create a whole matrix of designs

4. Under SystemControl, select appropriate autofocus mode (pneumatic or optical)

5. Press “Center”

6. Press blue down arrow to autofocus

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7. Optional: find sample center with either wafer or plate auto‐centering

8. Open global alignment wizard: Wizardry

‐> Execute global alignment

9. Execute rotation alingment:

a. Using arrows for stage control (or type in coordinates directly), go to left alignment mark P1, center it on the camera screen

b. Click “Next Step” on the bottom c. On camera screen, click on mark

P1 d. Center on right alignment mark

P2 in camera screen e. Click “Next Step” on the bottom f. On camera screen, click on mark

P2 g. Click “Save and go to 0,0” OR on

“Save and start next iteration” to repeat step 9

Note: you want two marks total that are on the same horizontal in CAD. It can be a cross, or a corner, or any two arbitrary points that have the same global Y‐coordinate

10. Execute translation alignment a. On camera screen, center on a

feature with known X,Y global coordinate

b. Click “Set Zero” in middle of StageControl

c. Move back to center of CAD by translating stage by –X and –Y from the selected feature

d. Click “Set Zero” again e. Your origin is now aligned with

the origin of your CAD

11. At this point you can either create die‐by‐die script for alignment, or expose the job

12. To expose, hit green “Execute” button in Job tab

13. In the pop‐up box, click OK to turn on

laser

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14. After exposure has completed, click OK in pop‐up box to move write head to standby position

15. Click OK in process finished pop‐up box

16. The stage should unload automatically. But if it does not, click “Load” in SystemControl to unload the sample

17. Unload your sample, return default filter

and write head, log out by clicking File ‐> Change user

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APPENDIX B: TOP‐SIDE BEAM OFFSET CALLIBRATION

The cameras and the laser beam are not targeting the same spot on the stage. There is an offset built

into the software for the stage to move in order for the beam to be aligned with where the camera

center is. Every time the write head is moved, it is not placed perfectly into the same exact position, and

it is possible for this offset to drift over time. If your top‐side alignment is off by more than a couple of

micros, you can attempt to recalibrate the offset using procedure below. You will need to have a sample

with two layers and the second layer was exposed on the DWL66+ using global alignment.

1. Load your exposed and developed sample into the tool. Focus the write head down and navigate the stage to locate your alignment marks. It is best to find features with a corner that should have the same position between two layers if the alignment is perfect. In this example, the points of two arrows should be touching

2. Open the correction menu by going to

Wizardry ‐> Writehead ‐> Calibrate beam offset

3. If you are already looking at the mark

on the first layer, then click “Next Step” at the bottom

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4. Under camera, select “Micro”. Under measurement, select “Position Manual” Make sure Iterations is set to 1, and click “Execute Measurement”

5. On the camera screen, you will see a

green cross. Click on the vertex of the first layer that should overlap with the second layer.

6. Click “Next Step” if you are already

looking at the layer 2 point on camera

7. Select same parameters for layer 2, click “Execute Measurement” and on camera screen click on point on layer 2 that should be on the same position as in layer 1.

Layer 1 vertex

Layer 2 vertex

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8. Review the results. Make sure the measured offset and the new offset make sense. Click “Save and close”

After this calibration, expose your real sample. In general, this calibration is not necessary to perform for

each alignment unless you find gross misalignment. If your alignment still does not work after

calibration, contact Staff for help.

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APPENDIX C: OPTICAL FOCUS FIX

Occasionally the optical autofocus can skip past the optimal focus plane. If that happens repeatedly, try

using the procedure below to help the tool find proper focus.

1. Raise the write head by pressing the up button

2. Click on the “Fix” button on top and

input 65000 as the value, then click “Fix to”

3. Try focusing again. If you continue to

have issues, contact staff regarding your process.

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Version history

Draft Date Author Notes on changes

v.0.1 November 29, 2016

v.0.2 April 6, 2017 Sen Liu Whole procedure

v.0.3 11/1/17 Roman Added global alignment

V0.4 Nov 2018 Roman Update to C menu 1.8

V0.5 Jan 2019 Roman New chuck, screws schematic added

V0.6 Nov 2019 Roman Edits to conversion to clarify where buttons are.

V1.0 Jan 2020 Roman Added “device prompt”

heidelberg dwl66 laser writer sop - princeton university

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