JEOL JBX-9300FS Electron Beam Lithography System Training 6/17/09, revision 11

Course Outline 6/17/09, revision 11 Explain hardware column, lenses, amplifiers field, chip, subfield shot pitch, beam diameter D = (I * t)/A Calibration AE & BE marks INITAE, INITBE, PDEFBE, SUBDEFBE, DISTBE HEIMAP Substrate various cassettes global & chip mark alignment virtual chip mark height detection Pattern Preparation CAD file preparation linkCAD conversion file transfer JBXFiler Job Deck & Schedule File Schd and Array check ALD & Exposure Resist Exposure & development positive & negative resists contrast liftoff, etching Proximity Effect Website 6/17/09, revision 11

Why E-beam Lithography? exceeds patterning capability of optical lithography easily pattern sub-micron features MiRC has demonstrated 6.5nm features patterns rapidly created from CAD file no mask necessary like optical lithography rapid turn around on design modifications, ideal for research You should not be using Ebeam Lithography to pattern primarily micron size features. 6/17/09, revision 11

JBX-9300FS key features 4nm diameter Gaussian spot electron beam 50kV/100kV accelerating voltage 50pA – 100nA current range 50MHz scan speed +/- 100um vertical range automatic focus +/- 2mm vertical range manual focus ZrO/W thermal field emission source vector scan for beam deflection max 300mm (12") wafers with 9" of writing area < 20nm line width writing at 100kV < 20nm field stitching accuracy at 100kV < 25nm overlay accuracy at 100kV 6/17/09, revision 11

Generic Block Diagram Electron Opics reference marks stage Gun Control Blanking Deflection Electron Optics Pattern Proc. and control Stage Computer x-interferometer y-interferometer stage motor Electron Opics reference marks 6/17/09, revision 11

Column 6/17/09, revision 11 ZrO/W emitter Suppressor Electron gun First anode Second anode Acceleration electrodes Ground anode First alignment coil Second alignment coil Blanking electrode Blanking aperture Second lens Third Zoom lenses Dynamic focus correction electrode Third alignment coil Dynamic astigmatism correction electrode Subsidiary deflector (SUBDEF) Electromagnetism astigmatism correction electrode Main deflector (PDEF) Backscattered electron detector Objective aperture Objective Workpiece surface 6/17/09, revision 11

Beam & Stage Position Stage position accuracy = λ / 1024 = 0.62nm 6/17/09, revision 11

PDEF & SUBDEF 50 6/17/09, revision 11

Top View of Stage 6/17/09, revision 11

Side View 6/17/09, revision 11

Stage w/o Cassette laser mirrors cassette goes here 6/17/09, revision 11

Wafer Cassette 6/17/09, revision 11

Field Stitching 500 µm (100kV) 500 µm (100kV) 6/17/09, revision 11

Within Field Writing Vector scan 6/17/09, revision 11

4” Wafer with Chips 2mm 2mm 6/17/09, revision 11

Example “Chip” Subfields 4um 4um 500um Field 500um Chip beam diameter Chip 6/17/09, revision 11 shot pitch

Objective Aperture larger aperture = larger beam diameter, more current smaller aperture = higher resolution aperture beam diameter min resolution current range 3,4,5 4 – 9nm < 20nm 50pA – 2nA 6 8 – 14nm 30nm 2nA – 7nA 7 30nm 60nm 10nA Most of the time, the 9300 will be set to aperture #3 and 2nA beam current. 6/17/09, revision 11

Beam diameter as a function of current & aperture 6/17/09, revision 11

Dose Equation where D = dose (µC/cm2) I = current (A) t = time (sec) A = exposure area (cm2) 6/17/09, revision 11

time calculator at http://nanolithography.gatech.edu/tcalc.php Job Time Estimate if D = 200 µC/cm2 A = 1 cm2 I = 2nA then t = 27 hours 46 min time calculator at http://nanolithography.gatech.edu/tcalc.php Ebeam lithography is very slow compared to optical lithography. Therefore you need to be careful about considering the amount of time it will take to expose your design. 6/17/09, revision 11

Shot Pitch Shot pitch is equivalent to pixel value – the smaller the shot pitch, the better the feature definition Shot pitch is limited by scanning frequency of the SUBDEF (max = 50MHz) 6/17/09, revision 11

Effect of Shot Pitch Energy deposited in resist Consider a line is exposed with 200uC/cm^2 dose. Depending on the number of pixels that the line-width is divided into, the line edge roughness (LER) and line-width will vary. x The graph at right shows the cross-section of energy deposition profile of a line with 1,2,4 and n pixels. 6/17/09, revision 11

Minimum Shot Pitch Calculation t = D.A/I A = area of pixel = a2 t = 1/fclk where fclk is the maximum scanning frequency of the amplifier  a = √I/(fclk.D) 6/17/09, revision 11

Faraday Cup 6/17/09, revision 11

6/17/09, revision 11 Explain hardware column, lenses, amplifiers field, chip, subfield shot pitch, beam diameter D = (I * t)/A Calibration AE & BE marks INITAE, INITBE, PDEFBE, SUBDEFBE, DISTBE HEIMAP Substrate various cassettes global & chip mark alignment virtual chip mark height detection Pattern Preparation CAD file preparation linkCAD conversion file transfer JBXFiler Job Deck & Schedule File Schd and Array check ALD & Exposure Resist Exposure & development positive & negative resists contrast liftoff, etching Proximity Effect Website 6/17/09, revision 11

Stage faraday cup AE, BE mark SEM sample 6/17/09, revision 11

Absorbed Electron Detection 6/17/09, revision 11

INITAE metal grid y - scan x - scan ds/dx ds/dy pn junction mark center position 6/17/09, revision 11

Backscattered Electron Detection 6/17/09, revision 11

INITBE Au cross on Si substrate y - scan x - scan ds/dx ds/dy mark center position 6/17/09, revision 11

PDEFBE, SUBDEFBE, DISTBE mark detection 6/17/09, revision 11

PDEFBE & SUBDEFBE gain 4 um 500 um 4 um 500 um rotation PDEFBE 1 2 3 top 482um 4 um 500 um 482um 4 6 rotation 5 left right 7 8 9 bottom PDEFBE 4 points measured x & y gain correction x & y rotation correction SUBDEFBE 9 points measured x & y gain correction x & y rotation correction shift 6/17/09, revision 11

DISTBE Field Distortion Correction 6/17/09, revision 11

Height Detection 6/17/09, revision 11

HEIMAP measures height across wafer on defined array positions (adjustable by user) takes average height and uses that for focus value for writing everywhere appropriate for 100pA & 1nA current not appropriate for 10nA – use virtual chip mark height detection 6/17/09, revision 11

6/17/09, revision 11 Explain hardware column, lenses, amplifiers field, chip, subfield shot pitch, beam diameter D = (I * t)/A Calibration AE & BE marks INITAE, INITBE, PDEFBE, SUBDEFBE, DISTBE HEIMAP Substrate various cassettes global & chip mark alignment virtual chip mark height detection Pattern Preparation CAD file preparation linkCAD conversion file transfer JBXFiler Job Deck & Schedule File Schd and Array check ALD & Exposure Resist Exposure & development positive & negative resists contrast liftoff, etching Proximity Effect Website 6/17/09, revision 11

Available Cassettes Wafer Masks Pieces 75mm, 100mm, 150mm, 200mm diameter 300mm can be purchased for up to 9” square writing area Masks 5” mask, 6” mask Pieces minimum 3 x 5mm piece 6/17/09, revision 11

4” Wafer Cassette 6/17/09, revision 11

Backside of Wafer Cassette 6/17/09, revision 11

Global & Chip Mark Detection 6/17/09, revision 11

6/17/09, revision 11 Explain hardware column, lenses, amplifiers field, chip, subfield shot pitch, beam diameter D = (I * t)/A Calibration AE & BE marks INITAE, INITBE, PDEFBE, SUBDEFBE, DISTBE HEIMAP Substrate various cassettes global & chip mark alignment virtual chip mark height detection Pattern Preparation CAD file preparation linkCAD conversion file transfer JBXFiler Job Deck & Schedule File Schd and Array check Resist Exposure & development positive & negative resists contrast liftoff, etching Proximity Effect Website 6/17/09, revision 11

CAD file conversion AutoCAD .DXF file linkCAD or GDSII file CADENCE JEOL01 file JBXFILER JEOL52 v3.0 file 6/17/09, revision 11

SCHD execution specifies specifies 1. wafer cassette window 1. JEOL52 v3.0 pattern file 2. how to arrange on wafer 3. shot modulation 4. type of calibration 5. beam current specifies 1. wafer cassette window 2. calibration file 3. base dose 4. job deck file(s) to use 5. shot pitch 6/17/09, revision 11

Pattern Preparation 6/17/09, revision 11

JBXFILER Pattern Preparation 6/17/09, revision 11

6/17/09, revision 11 Explain hardware column, lenses, amplifiers field, chip, subfield shot pitch, beam diameter D = (I * t)/A Calibration AE & BE marks INITAE, INITBE, PDEFBE, SUBDEFBE, DISTBE HEIMAP Substrate various cassettes global & chip mark alignment virtual chip mark height detection Pattern Preparation CAD file preparation linkCAD conversion file transfer JBXFiler Job Deck & Schedule File Schd and Array check Resist Exposure & development positive & negative resists contrast liftoff, etching Proximity Effect Website 6/17/09, revision 11

Negative/Positive Resist exposing e-beam exposing e-beam substrate NEGATIVE POSITIVE select appropriate resist for process and to minimize writing time 6/17/09, revision 11

resist vs. dose curves resist thickness resist thickness dose dose negative more sensitive positive resist thickness resist thickness less sensitive dose dose more contrast resist thickness less contrast dose 6/17/09, revision 11

Resists on hand at MiRC Positive resists Negative resist ZEP520A good etch resistance fast good resolution (~ 10nm) expensive ($3/mL) PMMA cheap ($1/mL) good for liftoff high resolution (< 10nm) poor etch resistance slow Negative resist XR-1541 (HSQ) good etch resistance (HSQ is basically SiO2) excellent resolution (6.5nm) slow expensive ($4/mL) ma-N 2403 (Novolak) good etch resistance optical DUV exposable faster than HSQ moderately priced ($2/mL) poor adhesion to quartz 6/17/09, revision 11

Resist Comparison 6/17/09, revision 11

Metal Liftoff evaporate metal onto strip resist patterned resist 6/17/09, revision 11

6/17/09, revision 11 Explain hardware column, lenses, amplifiers field, chip, subfield shot pitch, beam diameter D = (I * t)/A Calibration AE & BE marks INITAE, INITBE, PDEFBE, SUBDEFBE, DISTBE HEIMAP Substrate various cassettes global & chip mark alignment virtual chip mark height detection Pattern Preparation CAD file preparation linkCAD conversion file transfer JBXFiler Job Deck & Schedule File Schd and Array check Resist Exposure & development positive & negative resists contrast liftoff, etching Proximity Effect Website 6/17/09, revision 11

Electron Solid Interactions electrons forward scatter in resist (alpha) electrons backscatter off substrate (beta) Causes dose to spread away from where you want it to go, and expose areas you don’t want to be exposed 6/17/09, revision 11

Forward Scattering (α) as electrons enter resist, they experience small angle scattering, effectively broadening the initial beam diameter forward scattering is minimized by using the thinnest possible resist and highest accelerating voltage df = effective beam diameter (nm) Rt = resist thickness (nm) Vb = acceleration voltage (kV) 6/17/09, revision 11

Backscattering (β) as electrons pass thru resist and enter substrate, many will undergo large angle scattering events these electrons may return back into the resist at a significant distance from the incident beam, causing additional resist exposure → this is called the proximity effect 6/17/09, revision 11

Electron Solid Interaction Source: SPIE Handbook of Microlithography, Section 2.3 Electron-Solid Interactions 6/17/09, revision 11

Simulated Electron Energy Profile Source: SPIE Handbook of Microlithography, Section 2.3 Electron-Solid Interactions 6/17/09, revision 11

Alpha & Beta (for 0.5um resist on Si substrate) Beam energy (keV) α (um) β (um) η 5 1.33 [0.18] [0.74] 10 0.39 [0.60] 20 0.12 2.0 0.74 50 0.024 9.5 100 0.007 31.2 backscattered electrons have large range at 100kV!!! 6/17/09, revision 11

Influence of Proximity Effect on Pattern Generation 6/17/09, revision 11

Line Edge Deviations due to Proximity Effect 6/17/09, revision 11

Proximity Effect Correction by Dose Modulation 6/17/09, revision 11

Proximity Effect Correction by Shape Modulation original CAD pattern simulated dose profile calculated shape modification to achieve desired line 6/17/09, revision 11

Dose Dependencies required dose pattern size required dose pattern density required dose resist thickness acceleration voltage required dose substrate AMU required dose 6/17/09, revision 11

Example of Proximity Effect large exposed area next to small lines causes overexposure 6/17/09, revision 11

How to correct in my CAD file? separate small features from large features by placing on different layers in AutoCAD then assign a different datatype to each layer in linkCAD then assign different doses (shot modulation) to each datatype try a wide range of doses on your first exposure use SEM image to make careful dimension measurements adjust dose as necessary and repeat exposure 6/17/09, revision 11

(exception: 2nm line group has same spacing as 10nm line group) Test Pattern line width 50 x 50um 2nm 10nm 20nm 50nm 100nm 200nm 500nm 1000nm 1 x line 2 x line 3 x line 4 x line 5 x line 10 x line 10um 20um 30um 40um 50um space width (exception: 2nm line group has same spacing as 10nm line group) 6/17/09, revision 11

1um lines in ZEP at various pitch 6/17/09, revision 11

Required dose for 1um line in ZEP as a function of grating 6/17/09, revision 11

6/17/09, revision 11 Explain hardware column, lenses, amplifiers field, chip, subfield shot pitch, beam diameter D = (I * t)/A Calibration AE & BE marks INITAE, INITBE, PDEFBE, SUBDEFBE, DISTBE HEIMAP Substrate various cassettes global & chip mark alignment virtual chip mark height detection Pattern Preparation CAD file preparation linkCAD conversion file transfer JBXFiler Job Deck & Schedule File Schd and Array check Resist Exposure & development positive & negative resists contrast liftoff, etching Proximity Effect Website 6/17/09, revision 11

Website http://nanolithography.gatech.edu 6/17/09, revision 11