Advancing the Standard
Advancing the Standard

Feb 24th, 2021
Satoshi Shimizu

Laser Lithography
レーザー露光装置による3Dグレイスケール及び2Dマスク露光用データ補正とシミュレーションの紹介
GenISys株式会社

清水 諭

Advancing the Standard

About GenISys

GenISys offers software solutions for
optimization of micro and nanofabrication processes
Company:•Founded in 2005
•Headquartered in Munich, Germany• Expert team for lithography software development•Subsidiaries in USA-California, Japan-Yokohama•Global Technical Support•Fast, Flexible, Responsive

2021.02.24 - Web Seminar

2Products

Advancing the Standard

Electron and Laser Beam Direct Write Software•Market leader for Gaussian beam direct write systems•Installed at most major nano-fabrication centers worldwide•Has become a MUST for advanced e-beam lithographyMonte Carlo simulation software•MC- Simulation of electron distribution for e-beam lithography modeling and correction•Process Calibration, PSF visualization, extraction and management

3D lithography simulation & OPC software•Proximity Lithography (mask aligner) & Projection Lithography (stepper / scanner)•Electron Beam Lithography•Laser Beam Lithography (Heidelberg Instruments laser systems)

SEM Image Analysis & Metrology•Metrology software for SEM

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Advancing the Standard> 500 commercial licenses in World WideInstalled Base• > 230 BEAMER (83 EU, 80 APAC, 70 US/CA)• 140 TRACER• 65 LAB• 30 ProSEM• Major nanofabrication center worldwide• Universities, Research Center• Industrial R&D and special production• Advanced FPD manufacturer
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4Advancing the StandardAgenda• バイナリ露光における近接効果と、現像による形状への影響• Rule OPC と Model OPC 補正のご紹介• グレイスケール露光における補正• LAB によるシミュレーション• まとめ5

Greyscale vs. Binary

Advancing the Standard• Standard binary laser lithography sounds
rather „simple“ (compared to greyscale)• Increase the intensity above dose toclear of the resist• Resist will be cleared in exposed area,remain on unexposed area (for positiveresist)

3 µm

300 nm2021.02.24 - Web SeminarProximity & Process Efects

Advancing the Standard• Unfortunately nothing is binary in lithography• Beam has a „blur“ (shape) which spreads theintensity radially, not necessaraly radialsymetric• Exposure is on a pixel grid, typicall muchsmaller than the beam• x/y dependency by scan / step
• Beam is focused to one plane, depth of focus isNA dependent (write head)• Resist is not fully transparent, mostly bleaching,leading to depth dependent intensity• …larger than the pixel size
x-y may be different(not to scale!)• …not constant along z-axis• …Scan direction
dependency

2021.02.24 - Web Seminar• Unfortunately nothing is binary in lithography• Resist is not „digital“, most laser resists
are quite low contrast• Dissolution rate depends on local
intensity (3D!)• Lateral development• Depth dependent development time
• Resist development loading effects• Macro-loading (very large area)• Micro-loading (very small area)

Proximity & Process Efects
DevelopeSample Contrast Curve
250,00

Ideal

ExperimentGamma=3.75

200,00Thickness [nm]Advancing the Standard

150,00Real

100,00

50,00

0,00
0

0,10,20,30,40,50,60,70,80,91

Dose Factor•

Developer front moving to all direction– lateral development

Exposure result:
Dimension (CD), feature fidelity (e.g. corner rounding), profile (sidewall angle)
depends on target layout and both tool and process parameters2021.02.24 - Web Seminar

Analysis using 3D Laser Simulation

Advancing the Standard

LayoutLaser
Exposure
3DBulk Intensity

3D Resist
3DConcentration
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Advancing the Standard

Optical Proximity Effects• Small Beam Size (0.4 µm)

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Advancing the Standard

Optical Proximity Effects• Medium Beam Size (0.8µm)

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Advancing the Standard

Optical Proximity Effects• Large Beam Size (1.2µm)

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AgendaAdvancing the Standard• バイナリ露光における近接効果と、現像による形状への影響• Rule OPC と Model OPC 補正のご紹介• Rule OPC : 「線形補正」「コーナー補正」• Model OPC : 露光物理モデルによる全体形状補正• グレイスケール露光における補正• LAB によるシミュレーション• まとめ

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Advancing the Standard

Laser Binary Exposure & Process Distorsion

CD variation• Size → CD linearity• Density → Iso-dense bias
• X-, Y- direction• Angle dependent

Resolution
limit

Iso-dense Bias

Source:IMS Chips Stuttgart
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Advancing the Standard

Rule Based OPC

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Advancing the Standard

Application of Shape - OPC

After correction• CD linearity is improved, esspecially for iso• Iso-dense bias is largely corrected• Resolution limit is improved to print 500nm

Source:IMS Chips Stuttgart
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Advancing the Standard

Agenda• バイナリ露光における近接効果と、現像による形状への影響• Rule OPC と Model OPC 補正のご紹介• Rule OPC : 「線形補正」「コーナー補正」• Model OPC : 露光物理モデルによる全体形状補正• グレイスケール露光における補正• LAB によるシミュレーション• まとめ

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Rule-OPC process

Advancing the Standard

LayoutSegmentation

1st section of parameters used to split
layout to segments

Applying rules

2nd section of parameters – table of rules
determines changes for each segment2021.02.24 - Web Seminar

Correction

Advancing the Standard

Vertical lines iso
Vertical lines with smaller distance to neighbor
Serifs added for outer corners

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Corner Enhancement Example

Advancing the Standard

No OPC

Rule OPC

0.9 µm Squares

1μm

1 µm Squares

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MASKER Introduction

Advancing the Standard

Agenda• バイナリ露光における近接効果と、現像による形状への影響• Rule OPC と Model OPC 補正のご紹介• Rule OPC : 「線形補正」「コーナー補正」• Model OPC : 露光物理モデルによる全体形状補正• グレイスケール露光における補正• LAB によるシミュレーション• まとめ

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Advancing the StandardSelf consistent edge equalization method

Each bias adds or subtracts exposed area :energy at the evaluation point is changed until
a self consistent solution has been found.
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Advancing the Standard

Shape PEC / Model OPC principle+++++++ +++ +++ ++ ++ +++ + +++ ++ + ++ + ++++ + ++ ++++ + + +++ + + ++ ++ ++ ++ + ++ ++
+ ++
+ +++
+To solve:
Intensity at layout edges are not equal➢ resist edge does not match layout edge
➢ Move edges locally to get equal intensity

In a DRC step all edge segments
are analyzed for the CD anddistance to adjacent shapes.
A set of representative evaluation
points (+) is defined.

All segments with eval points
are moved iteratively to adjust
intensity at target layout edge
to get equal
2021.02.24 - Web SeminarModel-based correction

Advancing the Standard•

convolution kernel already corrects for major effects– CD-Linearity loss is an indicator for laser spot size
– Flare is added as a constant background– Overdose accounts for out-of-isofocal process points(contrast enhancement)• Other terms that could be easily added– Longer-range blur to account for process contributions– Elliptical spots to account for X-Y (scan/stepping) differences

1um

2um

Exposure on DWL system at
MPG in Munich - Germany

1um

2um

24

AgendaAdvancing the Standard• バイナリ露光における近接効果と、現像による形状への影響• Rule OPC と Model OPC 補正のご紹介• グレイスケール露光における補正• LAB によるシミュレーション• まとめ

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Laser Gray Scale Application

Advancing the Standard• Large variaty of application need 3DDOE

MEMS, MOEMS
Diffusers

Courtesy of IGI
Courtesy of Kuraray

Fresnel lenses, Blazed gratings

Microlenses, Microlens arrays

Courtesy of IMS

Advancing the Standard

Proximity & Process Efefcts• The beam intensity isDevelope• …larger than the pixel size• …not constant along z-axis• Developer front moving to all(not to scale)direction – lateraldevelopment

Output topography strongly depends on target
geometry and both tool and process parameters

Advancing the Standard• Light absorption in photoresist is a non-linear process• Modify how energy is distributed into gray levels

Gray Scale ExposureAdvancing the Standard

Laser Grey-Tone Correction

Experimental / iterative approach

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Advancing the Standard

Laser Grey-Tone Correction

Experimental / iterative approach

W ORKS QUITE WELL, BUT…
• … can be very time consuming

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Advancing the Standard

BEAMER offers a streamlined
workflow to prepare exposure data forgenerating 3D resist profiles:-Import PNG or GDS with target resist
heights-Import resist contrast curve-Output: Corrected data in native
Heidelberg Instruments machinereadable format. No further datapreparation required for exposure

Model Based Approach

Laser Grey-Tone Correction

Advancing the Standard

Laser Example Process• Wafer stack• Substrate: 4" glass plate (soda lime)• Resist: 2.2µm of AZ1512HS• Exposure• DWL66+ Write Mode II and optical autofocus.
• 1% (filter) of 230mW (405nm diode laser)• Development• Developed with AZ726MIF 3min. @21°C• Measurement• confocal microscope (Nanofocus)

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Advancing the Standard

Correction is including
the proximity area

Exposure data after correction

Fresnel Lens

Advancing the Standard

FRESNEL LENS PROFILE00-1-2-3-4-5-6-7-8-9-1020

4060

80100120

140160180200DOE – 3.2 µm Squares/Pixels

Advancing the Standard

Standard
HIMT
conventional

T5with BEAMER

BEAMER is significantly better for the DOE.

AgendaAdvancing the Standard• バイナリ露光における近接効果と、現像による形状への影響• Rule OPC と Model OPC 補正のご紹介• グレイスケール露光における補正• LAB によるシミュレーション• 3Dシミュレーション• 2D OPCシミュレーション• まとめ

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Advancing the Standard

3D-PEC : Design Example
resistsubstrate

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3D-PEC : Design Example

Advancing the Standard

resistsubstrateCAD layer
or Bitmap

1 2 3 4 5 1 2…
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Advancing the Standard

LAB Simulation

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Advancing the Standard

LAB Simulation

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Advancing the Standard

LAB Simulation

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Advancing the Standard

LAB Simulation
レジスト現像シミュレーション

レーザー露光シミュレーション

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AgendaAdvancing the Standard• バイナリ露光における近接効果と、現像による形状への影響• Rule OPC と Model OPC 補正のご紹介• グレイスケール露光における補正• LAB によるシミュレーション• 3Dシミュレーション• 2D OPCシミュレーション• まとめ

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Advancing the Standard

2um Square Dots

without correction

Corner Rounding = 0.65 um (av.)
2021.02.24 - Web Seminar2um Square Dots

Advancing the Standard

without correction

200nm Serif with 70% overlap
200nm

2um

Corner Rounding = 0.65 um (av.)
2021.02.24 - Web Seminar2um Square Dots

Advancing the Standard

without correction

200nm Serif with 70% overlap
200nm

2um
Overlap
200nm x 70%

Corner Rounding = 0.65 um (av.)
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Advancing the Standard

without correction

2um Square Dots
200nm Serif with 70% overlap

Corner Rounding = 0.65 um (av.)
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Advancing the Standard

without correction

Corner Rounding = 0.65 um (av.)

2um Square Dots
200nm Serif with 70% overlap

Corner Rounding = 0.56 um (av.)
2021.02.24 - Web Seminar2um Square Dots

Advancing the Standard

without correction

200nm

2um

2021.02.24 - Web Seminar2um Square Dots

Advancing the Standard

without correction

350nm

2um

2021.02.24 - Web Seminar2um Square Dots

Advancing the Standard

without correction

Aim is to see serif size & overlap
influences by experiment
350nm

2um

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Advancing the Standard

without correction

2um Square Dots
350nm Serif with 60% overlap

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Advancing the Standard

without correction

2um Square Dots
350nm Serif with 60% overlap

Overshooting correction
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Advancing the Standard

Pattern with Corner Serifs

LAB Simulation : 2um Square Dots
350nm Serif with 60% overlap

Overshooting correction
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Advancing the Standard

Absorbed Energy (405nm)

LAB Simulation : 2um Square Dots
350nm Serif with 60% overlap

Overshooting correction
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Advancing the Standard

3D Resist View

LAB Simulation : 2um Square Dots
350nm Serif with 60% overlap

Overshooting correction
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Advancing the Standard

Resist Contour

LAB Simulation : 2um Square Dots
350nm Serif with 60% overlap

Overshooting correction
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Advancing the Standard

350nm Serif with 60% overlap

LAB Simulation : 2um Square Dots
200nm Serif with 70% overlap

2021.02.24 - Web Seminar

Advancing the Standard

350nm Serif with 60% overlap

LAB Simulation : 2um Square Dots
200nm Serif with 70% overlap

2021.02.24 - Web Seminar

Advancing the Standard

350nm Serif with 60% overlap

LAB Simulation : 2um Square Dots
200nm Serif with 70% overlap

Simulation is able to predict proper serif size in advance2021.02.24 - Web Seminar

AgendaAdvancing the Standard• バイナリ露光における近接効果と、現像による形状への影響• Rule OPC と Model OPC 補正のご紹介• グレイスケール露光における補正• LAB によるシミュレーション• まとめ

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Advancing the StandardSummary• レーザー描画において、レーザー光による近接効果や現像の影響（横方向現像等）は仕上がり形状に影響を与えるため、補正が必要となる。
• サイズ形状補正を行うRule-OPCや、物理露光モデルをベースとした Model-OPCといった自動補正ツールを用いて、形状の線形性やコーナー補正が可能。
• グレイスケール露光では、CADを読み込み後、BEAMERによる自動計算アルゴリ
ズムにより設計値に対する適切な露光量が簡便に求められる。応用例：マイクロレンズ、フレネルレンズ、DOE• LAB によるレジスト計算を用いて、２Dや３D形状の事前予測が可能。結果を見ながら露光パラメータの選択範囲を実験前に絞り込むことが出来る。

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Advancing the Standard

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