Advancing the Standard

Satoshi Shimizu
March 11th 2022

Laser Lithography
レーザーグレースケール露光及びバイナリ露光のため描画データ最適化のご紹介
GenISys株式会社 清水 諭

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Advancing the Standard

Agenda・三次元構造物の作製やバイナリマスク描画などを念頭においてレーザー描画が昨今活用されています。
・描画においては、ガウス分布するレーザー光の重なりとその光量の強弱によって、現像後のレジストパターンのサイズやコーナー出し、あるいは三次元の場合には高さも含めて制御を行う手法は、時に多くの技術的知見や経験を要します。

・本講演では、データ準備の観点から所望の設計構造物を念頭においた描画データ最適化の手法をご紹介します。

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HIMT – GenISys Cooperation

Advancing the Standard

Heidelberg Instruments and GenISys Announce
Cooperation on Maskless Laser Lithography
Heidelberg, GERMANY, October 21, 2014 – Heidelberg
Instruments, a leading supplier of equipment and processsolutions for laser lithography related markets and GenISys
GmbH, a provider of high-performance software solutions
for nanoscale fabrication, today announced a cooperationagreement to combine the Heidelberg Instruments laser
lithography tools with the GenISys data-preparation,
simulation and process correction software packages ofBEAMERTM and LABTM.
Within the cooperation GenISys BEAMERTM has been
adapted to support Heidelberg Instruments laser exposuresystems with advanced layout data preparation. The 3D
simulation software LABTM has been extended to model theexposure of HIMT laser systems in 3D, enabling a
subsequent simulation of the resist process. Both parties
have joined forces to market the Heidelberg systems with
the GenISys lithography software packages. The
combination of advanced lithography equipment andpowerful data preparation, simulation and process
correction software is a key success factor for cost effective
process and device development for the end user.
……

Gray Tone Correction

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AIST TIA Central OfficeGray Tone Correction

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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

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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

Our customers> 500 commercial licenses in World Wide
• > 230 BEAMER (83 EU, 80 APAC, 70 US/CA)• 140 TRACER• 65 LAB• 30 ProSEM

De facto standard EBL software for Gaussian tools
7Advancing the StandardAgenda• レーザー描画概要• バイナリ露光の為の「Model-OPC」及び「Rule-OPC」補正• グレイスケール露光の為のドーズ量最適化補正• まとめ2022.03.11 AIST Maskless Seminar

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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 (forpositive resist)

3 µm300 nm2022.03.11 AIST Maskless Seminar

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Advancing the Standard• Unfortunately nothing is binary in lithography• Beam has a „blur“ (shape) which spreads
the intensity 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 offocus is NA dependent (write head)• Resist is not fully transparent, mostly
bleaching, leading to depth dependent
intensity

Proximity & Process Effects• …larger than the pixel sizex-y may be different(not to scale!)• …Scan direction
dependency

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10Analysis using 3D Laser Simulation

Advancing the Standard

LayoutLaser
Exposure
3D
Bulk Intensity

3DConcentration

3D Resist

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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• Midium Beam Size (0.8 µm)

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Advancing the Standard

Optical Proximity Effects• Large Beam Size (1.2 µm)

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Advancing the Standard

Agenda• レーザー描画概要• バイナリ露光の為の「Model-OPC」及び「Rule-OPC」補正• Model OPC : 露光物理モデルによる全体形状補正• Rule OPC : 「線形補正」「コーナー補正」• グレイスケール露光の為のドーズ量最適化補正• まとめ2022.03.11 AIST Maskless Seminar

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Advancing the Standard

Self 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 equal2022.03.11 AIST Maskless Seminar17

Model Based Correction for L&S

Advancing the Standard

10um
5um

3um
2um
1um

iso gap

1:1

1:3

1:5

1:10

iso line

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Advancing the Standard➢➢Model Based Correction for L&S

Short and Mid-range effects are corrected by modifying thelayout (instead dose modulation)
Same supports OPC for laser writing

e-beam shape correction

Laser OPC
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Advancing the Standard

Model Based Correction for L&S
2.0um

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Advancing the Standard

Model Based Correction for L&S
2.0um

1.89um2022.03.11 AIST Maskless Seminar

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Advancing the Standard

ProSEM - Batch Mode Measurement

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Results

Difference (um)Target CD

Advancing the Standard

1um Model

1um noCorrection(Measured- TargetCD)

0.4

2um Model

2um no Correction

0.35

10um Model

10um no Correction

Line width:
1, 2 and 10um

0.3
0.25
0.2

Exposure : MLA 150
write head = 4mm,80mJ/cm20.15
0.10.05

Resist : AZ1500 positive,
500 nm thickness.
on Cr/SiO2 substrate

0-0.05-0.1-0.15

iso-line

1:10

1:5

1:3

1:1

Pad

Development : AZ 400K
(1:4 dilution) for 1 min.

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Results

Difference (um)Target CD

Advancing the Standard

1um Model

1um noCorrection(Measured- TargetCD)

0.4

2um Model

2um no Correction

0.35

10um Model

10um no Correction

Line width:
1, 2 and 10um

0.3
0.25

No correction

0.2
0.15
0.10.05

Model based
correction

0-0.05-0.1-0.15

iso-line

1:101:5

1:3

1:1

Pad

Model correction results in improved CD linearity in thevarious CD and pattern density range.
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Advancing the Standard

Agenda• レーザー描画概要• バイナリ露光の為の「Model-OPC」及び「Rule-OPC」補正• Model OPC : 露光物理モデルによる全体形状補正• Rule OPC : 「線形補正」「コーナー補正」• グレイスケール露光の為のドーズ量最適化補正• まとめ2022.03.11 AIST Maskless Seminar

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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 dependentResolutionlimit

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• レーザー描画概要• バイナリ露光の為の「Model-OPC」及び「Rule-OPC」補正• Model OPC : 露光物理モデルによる全体形状補正• Rule OPC : 「線形補正」「コーナー補正」• グレイスケール露光の為のドーズ量最適化補正• まとめ2022.03.11 AIST Maskless Seminar

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Advancing the Standard

Corner Corrections

Corners are rounded
One common solution is to add Serifs at each corner

CAD

Modified Design2022.03.11 AIST Maskless Seminar30

Advancing the Standard

Corner Corrections

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2um Square Dots

without correction

2um Squares
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Advancing the Standard

2um Square Dots

without correction

Corner Rounding = 0.65 um (av.)
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2um Square Dots

Advancing the Standard

without correction

200nm Serif with 70% overlap

2um

Corner Rounding = 0.65 um (av.)
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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

Corner Rounding = 0.65 um (av.)

2um Square Dots
200nm Serif with 70% overlap

Corner Rounding = 0.56 um (av.)
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2um Square Dots

Advancing the Standard

without correction

350nm

2um

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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

LAB Simulation : 2um Square Dots

Pattern with Corner Serifs

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

LAB Simulation : 2um Square Dots

350nm Serif with 60% overlap

200nm Serif with 70% overlap

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Advancing the Standard

LAB Simulation : 2um Square Dots

350nm Serif with 60% overlap

200nm Serif with 70% overlap

Simulation is able to predict proper serif size in advance2022.03.11 AIST Maskless Seminar441um Square Dots

Advancing the Standard

without correction Resist = 500nm

200nm Serif with 70% overlap
200nm

1um
Overlap
200nm x 70%

Corner Rounding = 0.55 um
BEAMeeting, Sep. 15th, 202045

Advancing the Standard

without correction Resist = 500nm

Corner Rounding = 0.55 um

1um Square Dots
200nm Serif with 70% overlap

Corner Rounding = 0.44 um
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Corner Rounding

Advancing the Standard

Corner Rounding

Corner Rounding (um)

0.8
0.7
0.6

0.5
0.4
0.30.20.100100200300with Serif

400500600without

CD (um)Overall 100nm improvement oveserved especially at small corner size range
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Advancing the Standard

Agenda• レーザー描画概要• バイナリ露光の為の「Model-OPC」及び「Rule-OPC」補正• グレイスケール露光の為のドーズ量最適化補正• 概要• 入力ファイル準備と3Dドーズ量補正の実行• まとめ

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Laser Gray Scale Application

Advancing the Standard• Large variaty of application need 3D
DOE

MEMS, MOEMS

Diffusers

Courtesy of IGI
Courtesy of Kuraray

Microlenses, Microlens arrays

Fresnel lenses, Blazed gratings

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Advancing the Standard

Gray Scale Exposure2022.03.11 AIST Maskless Seminar

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Laser Grey-Tone Correction

Experimental / iterative approach

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

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Advancing the Standard

Laser Grey-Tone Correction

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

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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

Exposure Data after Correction

Correction is including
the proximity area

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Advancing the Standard

Agenda• レーザー描画概要• バイナリ露光の為の「Model-OPC」及び「Rule-OPC」補正• グレイスケール露光の為のドーズ量最適化補正• 概要• 入力ファイル準備と3Dドーズ量補正の実行• まとめ

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Advancing the Standard

Bitmap File Import2022.03.11 AIST Maskless Seminar

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STL File Import

Advancing the Standard

STLファイルの入力
設計値の最大高さ
BEAMERでは、STLファイルの高さに応じてLayer分けを行い、2次元平面図として読み込みます。
設計値の最低高さ

レンズの例

Layer 1
Layer 2
Layer 3Layer 4Layer 52022.03.11 AIST Maskless Seminar

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3D-PEC : Design Example

Advancing the Standardlayer

1 2 3 4 5 1 2…

各高さに相当する部分をそれぞれのレイヤーとして設計します。
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Advancing the Standard

BEAMER - 3D-PEC

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Advancing the Standard

3D-PEC : Height Setting

レイヤー番号はプルダウンから選択できます。
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Advancing the Standard

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Advancing the Standard

3D-PEC : Contrast Curve

実際に使う現像条件で取得した感度曲線を入力します（Dose vs. 残膜厚）2022.03.11 AIST Maskless Seminar62

Advancing the Standard

3D-PEC : Result

Dose Table

処理結果：
近接効果を含めたドーズ量補正が行われます。

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Fresnel Lens

Advancing the Standard

FRESNEL LENS PROFILE
0-10

20

40

60

80

100120140160180200-2-3-4-5-6-7-8-9-10

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Advancing the Standard

Convex Lens

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DOE – 3.2 µm Squares/Pixels

Advancing the Standard

Standard
HIMT
conventional

T5with BEAMER

BEAMER is significantly better for the DOE.
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Advancing the Standard

Measurement Feedback

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Advancing the Standard

Laser Image Formation

3D imaging kernels calculate the aerial image➢ Source Modelling• Any laser source, h-line, i-line, DUV• Arbitrary machine• Exposure strategy• beam step size (pixel)• machine specific (e.g. VPG, DMD)
• Optics• NA• Defocus• Flare➢ Fast and accurate calculation of aerial image

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Simulation of Laser Exposure Process
Absorbed intensities in resist

DWL

x-yviewExposureparametersx-zview

Grey tone exposure pattern
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LAB Simulation

Advancing the Standard

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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Advancing the StandardAgenda• レーザー描画概要• バイナリ露光の為の「Model-OPC」及び「Rule-OPC」補正• グレイスケール露光の為のドーズ量最適化補正• まとめ2022.03.11 AIST Maskless Seminar

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Advancing the Standard

Summary• 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で（横方向現像等）仕上がり形状が影響を受ける。そのため感度曲線からの「ドーズ vs. 高さ」の１:１補正では、期待した補正結果とならないことが多い。

• 物理露光モデルをベースとした Model-OPCでは、ガウス分布のレーザー光の重なりを考慮して線幅や形状の自動補正を行う。また「設計線幅 vs. 現像後仕上がりサイズサイズ」の検量線があれば、Rule-OPCツールを用いて線形なフィードバックを掛けられる。このRule-OPCではコーナー形状補正も可能。
• グレイスケール露光では、レジスト光学パラメータやガウス分布を含む露光条件、及び感度曲線情報から、BEAMERの自動計算により設計値に対する適切な露光量を求めることが出来る。応用例：マイクロレンズ、フレネルレンズ、DOEなど。

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Advancing the Standard

Global Headquarters
GenISys GmbH
Eschenstr. 66
D-82024 Taufkirchen, Germany
Phone: +49-89-3309197-60
Fax: +49-89-3309197-61
sales@genisys-gmbh.com

Asia Pacific & JapanGenISys K.K.
Yokohama Japan
Phone: +81 45 530 3306
ap@genisys-gmbh.com

North America
GenISys Inc.
Santa Clara, California, USA
Phone: +1-408-353-3951
usa@genisys-gmbh.com

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