Heidelberg DWL66 Laser Writer SOP

Tool owner: Roman Akhmechet, romana@princeton.edu, x 8‐0468Backup: Eric Mills, enmills@princeton.edu, x 8‐4626,Heidelberg DWL66 Laser Writer Standard OperatingProcedureQUICK GUIDEPROCEDURE OVERVIEW1.2.3.4.5.6.7.Write headConvert user layout fileLoad sampleUsing Basic ModeHeidelberg Global alignmentTop‐side Beam offset calibrationOptical offset fixCRITICAL PRECAUTIONS AND COMMON MISTAKES Place your sample on stage before setting up exposureNever touch the interferometer’s mirrors with your bare handsNever open coverlid when an exposure job is running (you cannot resume it)Write head center to the edge of your substrate must be 5 mmOnly users with legitimate need can mount/use/unmount 2 mm write head after trainingand 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 withphotoresists (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 duringexposure.Page 1 of 17

TOOL OVERVIEWThe Heidelberg DWL 66 is a high resolution pattern generator for mask making and direct writing. Itscapabilities and flexibility make it an ideal lithographic tool for research. It uses acousto‐optic modulatorsto adjust the laser intensity, and acousto‐optic deflectors to scan the beam. During an exposure, only thestage moves. The substrate is held down on the stage by vacuum and moves in the x‐y plane. Its positionis 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 2Dand 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. Interm of resolution, the 2 mm write head can achieve a minimum feature size of 650 nm, the 10 mm headcan achieve a minimum feature size of 1.4 m.Page 2 of 17

FULL PROCEDUREA) Write headWrite headCritical dimensionWrite speed2 mm 0.8 um6 mm2/min10 mm 1.8 um145 mm2/minOnly users with legitimate need can mount/use/unmount 2 mm write head after training andauthorization by tool owner. The default write head is 10 mm.B) Convert user layout file1. Use USB memory stick to transferlayout file and upload file to itscorresponding folder shortcut ondesktop (gdsii, cif, dxf or gerber).Note: if using gdsii, make sure the .gdsis lower case in file name2. Double click conversion iconondesktop to open GUI HIMT Convertwindow, select “File/New job” to createa new job.Job Name Guidelines: The job nameshould have no hyphens or spaces.There is a limit of 12 characters in thename. Please use your NEMO accountname as first part of the job name.For an existing job, select “File/Loadjob” to load an existing job.3. Under Source File, click “Add”, selectthe file type to pick your file, a newwindow will pop up with optionsdepending on the file type. Select thecorrect structure/cell and layer number,and then click “Create Default”. TheMain Status window should state NoWarnings, No Errors if the CAD fileloaded successfullyPage 3 of 17

4. Select the correct structure/cell andlayer number. These come from yourCAD and depend on how many layersyou have, what their GDS numbers are,and what you named your cells. Whenfinished selecting cells and layers, click“Create Default”.5. The Main Status window should stateNo Warnings, No Errors if the CAD fileloaded successfully6. Click the checkbox “TCL view” to turn iton.7. Click “VIEWER” to inspect pattern withHIMT Viewer.8. You can click Fill button to fill in theareas that will be exposed. You cannavigate around and zoom in and out.When done with the views, use the Exitbutton to close the windowPage 4 of 17

9. Select the correct “Write Lens” (Mustbe the same as what is mounted ontool.)10. In the “Justification” tab, select“Automatic Centering” to center yourpattern design. For masks also select“Mirror” at y to flip the design.11. “Expose Options” tab has additionaloptions for inversion and XORfunctions, as well as CD biasing12. Click “Complete Tasks” at the bottom,then save the job. Click “ExposeOffline”.Note: if you receive an error, pleasecheck that the name of your jobcomplies with all of the guidelines fromstep 2.13. Once the file transfer is finished, click“Finish” to complete file transfer.Page 5 of 17

C) Load Substrate Open the sash and turn on the light. Open the filter panel and install thecorrect filter for your process. Place your sample on the center ofthe stage. The sample must cover thecenter holes because that is whereautomatic focus occurs.Pay attention to the coordinatesystem inside the tool. (Positive Y tothe left, positive X away from the sashand towards the back) Page 6 of 17

Adjust white screws to open vacuumholes appropriate to your sample.From Right to Left, opening morescrews will increase how far fromcenter the vacuum is pulled Follow the guide below to open theright screws for your sample size. Ex:for 5 mm chip, place it in the verycenter and only open the rightmostscrew Turn on the vacuum using BOTH blackknobs.Note: In this tool, vertical is off andhorizontal is on Close the sash and turn off the lightPage 7 of 17

D) Set up an exposure job and expose pattern using exposure wizard in basic user modeBasic mode1. Double click on Lithography iconondesktop to prompt Lithography loginwindow. If the login window is ready skipprior 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 onthe top3. Click on “Update” at the bottom left torefresh files.4. Click on “ ” to populate “General” folderand double click your job file to promptExposure Parameter window.5. Find your design and double click it. Thiswill 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: pneumaticor optical Choose Focus offset settingspecific to your process Under “Automatic Centering”,choose whether to center the jobon your sample (PlateCenter forrectangular substrates,WaferCenter for wafers) Make sure “Laser Mode afterExposure” is DefaultPage 8 of 17

7. Make sure your substrate is on the stage,then click “Start Exposure” button atbottom.8. When the pop‐up shows up asking to loadthe substrate, click “Ok”9. NOTE: if there is another pop‐up asking tomount the correct device, make sure thecorrect write head is mounted on the tool,and acknowledge by pressing “OK”10. The tool will automatically focus, centerthe 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.Page 9 of 17

APPENDIX A: GLOBAL ALIGNMENTYou must be trained by staff to use advanced features. This section describes procedure to performglobal alignment for rotation and translation of whole array to sample. You may need to perform beamoffset 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” button1. Log in as User instead of Basic2. Set up desired filter and write head.Place your sample on chuck withappropriate vacuum3. On left in Job tab, select your job arrayor create a new one. Drag your design,modify array properties. You can use asingle cell, or create a whole matrix ofdesigns4. Under SystemControl, select appropriateautofocus mode (pneumatic or optical)5. Press “Center”6. Press blue down arrow to autofocusPage 10 of 17

7. Optional: find sample center with eitherwafer or plate auto‐centering8. Open global alignment wizard: Wizardry‐ Execute global alignment9. 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 screenb. Click “Next Step” on the bottomc. On camera screen, click on markP1d. Center on right alignment markP2 in camera screene. Click “Next Step” on the bottomf. On camera screen, click on markP2g. Click “Save and go to 0,0” OR on“Save and start next iteration”to repeat step 910. Execute translation alignmenta. On camera screen, center on afeature with known X,Y globalcoordinateb. Click “Set Zero” in middle ofStageControlc. Move back to center of CAD bytranslating stage by –X and –Yfrom the selected featured. Click “Set Zero” againe. Your origin is now aligned withthe origin of your CAD11. At this point you can either create die‐by‐die script for alignment, or exposethe job12. To expose, hit green “Execute” button inJob tabNote: you want two marks total that are on thesame horizontal in CAD. It can be a cross, or acorner, or any two arbitrary points that have thesame global Y‐coordinate13. In the pop‐up box, click OK to turn onlaserPage 11 of 17

14. After exposure has completed, click OKin pop‐up box to move write head tostandby position15. Click OK in process finished pop‐up box16. The stage should unload automatically.But if it does not, click “Load” inSystemControl to unload the sample17. Unload your sample, return default filterand write head, log out by clicking File ‐ Change userPage 12 of 17

APPENDIX B: TOP‐SIDE BEAM OFFSET CALLIBRATIONThe cameras and the laser beam are not targeting the same spot on the stage. There is an offset builtinto the software for the stage to move in order for the beam to be aligned with where the cameracenter is. Every time the write head is moved, it is not placed perfectly into the same exact position, andit is possible for this offset to drift over time. If your top‐side alignment is off by more than a couple ofmicros, you can attempt to recalibrate the offset using procedure below. You will need to have a samplewith two layers and the second layer was exposed on the DWL66 using global alignment.1. Load your exposed and developedsample into the tool. Focus the writehead down and navigate the stage tolocate your alignment marks. It is bestto find features with a corner thatshould have the same position betweentwo layers if the alignment is perfect. Inthis example, the points of two arrowsshould be touching2. Open the correction menu by going toWizardry ‐ Writehead ‐ Calibratebeam offset3. If you are already looking at the markon the first layer, then click “Next Step”at the bottomPage 13 of 17

4. Under camera, select “Micro”.Under measurement, select “PositionManual”Make sure Iterations is set to 1, andclick “Execute Measurement”5. On the camera screen, you will see agreen cross. Click on the vertex of thefirst layer that should overlap with thesecond layer.6. Click “Next Step” if you are alreadylooking at the layer 2 point on camera7. Select same parameters for layer 2, click“Execute Measurement” and on camerascreen click on point on layer 2 thatshould be on the same position as inlayer 1.Page 14 of 17Layer 1 vertexLayer 2 vertex

8. Review the results. Make sure themeasured offset and the new offsetmake sense.Click “Save and close”After this calibration, expose your real sample. In general, this calibration is not necessary to perform foreach alignment unless you find gross misalignment. If your alignment still does not work aftercalibration, contact Staff for help.Page 15 of 17