1. DIRECT ELECTRON-BEAM WRITING WITH HIGH ASPECT RATIO FOR FABRICATING ION-BEAM LITHOGRAPHY MASK DIRECT ELECTRON-BEAM WRITING WITH HIGH ASPECT RATIO FOR FABRICATING ION-BEAM LITHOGRAPHY MASK 2002. 04. 20. Byeonug-Nam Lee, Yong-Hoon Cho Department of Physics, Chungbuk National University, Cheongju 361-763, Korea. Young-Seok Kim, and Wan Hong, Hyung-joo Woo Particle Beam Application Team, Korea Institute of Geoscience and Mineral Resources, Daejeon, 305- 350, Korea.

2. Introduction Introduction  Lithography, it is that technology is able to transcribe narrow linewidth, exercises an effect on improvements in accumulation of DRAM and operation capacity of CPU. So, the main issue confronting the semiconductory industry is what the next generation lithography (NGL) should be.  Problems of optical lithography o The optical lithography can’t embody proven resolution below 0.1 ㎛. (e.g., embodiment 0.13 ㎛ by ArF laser [193nm]) o Optical lithography has aspect ratio about with 1:1,so that it don ’ t suit MEMS's purpose.(MEMS needs high aspect ratio.) o aspect ratio: h / s  Masked Ion Beam Lithography (MIBL) is one of the most promising candidates. MIBL is a technology to produce advanced, very large scale integrated (VSLI) and nanometer-scale circuits. The strengths of MIBL include proven resolution below 0.04 ㎛, wide exposure latitude, large depth of field, high throughput, and the possibility of avoiding substrate damage. h s

3. E-beam writing system E DA (digital-to-analog) converter DA (digital-to-analog) converter E DA (digital-to-analog) converter DA (digital-to-analog) converter (5MHz) COMPUTER Writing tool Home made writing program SEM (Scanning Electron Microscopy) SEM (Scanning Electron Microscopy) SEM (Scanning Electron Microscopy) SEM (Scanning Electron Microscopy) COMPUTER Drawing tool AutoCAD-polyline COMPUTER dxf.file Output voltage control Control signal=output voltage(V) 32768 10 (= Max V) * Analog out put: 2 * Analog range: -10~ +10v Output voltage: divide into 65536 (16 bit)

4. Structure of blank & Final Ion-beam Mask PMMA 0.4 ㎛ Au 0.03 ㎛ Ti 0.003 ㎛ Si 3 N 4 4 ㎛ Si Blank Mask f Final Ion-beam Mask Ion beam Si Si(B),Si 3 N 4 Ti Au

5. Summary of sample stage & e-beam lith. Faraday cup Standard sample mask o Acc. voltage: 40 KeV o Writing 시 Beam current :10 ~ 20 Pa o Writing 시 magnification : × 1000 o Focusing magnification on Standard sample : × 300,000 65536 o A screen of SEM is divided into a lattice of 65536 × 65536. o The position of electron beam spot is lineally changed by run voltage o Every lattice has voltage rectangular coordinates ; (Vx,Vy)

6. Designed pattern Pattern designs  The Pattern designs is using AutoCAD. oA space between two points is 1 ㎛ on Auto CAD coordinates. 16nm50nm a)b)

7. Primary factor of aspect ratio & linewidth Aspect Ratio & Line width  Develop - Developer - Temperature - Time  Blank Mask - Resist thickness - Resist uniformity  E-Beam Writing - Focusing - dosage - Beam energy

8. 0.08 ㎛ 디자인 선 폭의 현상조건 실험 mask ( ㎛ ) 가장 작은 선 폭 디자인 ( ㎛ ) writing Dose (c/ ㎛ 2) PMMA 0.35/ Au 0.05/Ti 0.001/Si 0.1 100 ~ 450 100 develop time (sec) temp. ( ℃ ) developerrinse 60 ~120 60 35,40 35 Morpholine 20% Ethanolamine 5% diethylenglykol- monobutylether 60% Agua Regia 15% diethylenglykol- monobutylether 80% DI 20% * 빨간 글씨 : 최적 조건

9. 0.08 ㎛ 디자인 선 폭 최적화 조건 mask ( ㎛ ) 디자인 선 폭 ( ㎛ ) writing Dose (c/ ㎛ 2) PMMA 0.4/ Au 0.05/Ti 0.001/Si 0.1 250 ~ 550 350 develop time (sec) temp. ( ℃ ) developerrinse 60 Room temp. Etoxyethanol 30% Methanol 70% Methanol 현상된 선 폭 ( ㎛ ) 종횡 비 0.167 1:2.4 * 빨간 글씨 : 최적 조건

10. 0.08 ㎛ 디자인 선 폭 최적화 조건 mask ( ㎛ ) 디자인 선 폭 ( ㎛ ) writing Dose (c/ ㎛ 2) PMMA 0.4/ Au 0.05/Ti 0.001/Si 0.08 200 ~ 550 350 develop time (sec) temp. ( ℃ ) developerrinse 60 Room temp. Etoxyethanol 30% Methanol 70% Methanol 현상된 선 폭 ( ㎛ ) 종횡 비 0.135 1 : 3 * 빨간 글씨 : 최적 조건 0.08 ㎛디자인 350μc/ ㎛ 2 KIGAM 20KV ×35,000 8mm 0.08 ㎛디자인 350μc/ ㎛ 2 KIGAM 20KV ×35,000 8mm 0.08 ㎛디자인 350μc/ ㎛ 2 KIGAM 20KV ×35,000 8mm 0.08 ㎛ 디자인 350μc/ ㎛ 2 KIGAM 20KV ×35,000 8mm 0.08 ㎛디자인 350μc/ ㎛ 2 KIGAM 20KV ×35,000 8mm 0.08 ㎛ 디자인 350μc/ ㎛ 2 KIGAM 20KV ×35,000 8mm 0.135 ( ㎛ )

11. 0.05 ㎛ 디자인 선 폭 최적화 조건 mask ( ㎛ ) 디자인 선 폭 ( ㎛ ) writing Dose (c/ ㎛ 2 ) PMMA 0.4/ Au 0.05/Ti 0.001/Si shasha7 200 ~1700 1400 develop time (sec) temp. ( ℃ ) developerrinse 60 Room temp. Etoxyethanol 30% Methanol 70% Methanol 현상된 선 폭 ( ㎛ ) 종횡 비 0.14 1 : 2.5 * 빨간 글씨 : 최적 조건

12. Result of proximity Control 조건 변화 0.08 ㎛ 디자인 선 폭 내 전자빔 조사량 차별화 현상된 선 폭 0.086 ~ 0.092 ( ㎛ )

13. Summary Summary  Masked Ion Beam Lithography (MIBL) is one of the most promising candidates 차세대 노광 기술인 이온 빔 노광 기술 용 0.1  m 이하의 선 폭에 종횡비가 1:7 인 마스크 개발 목표로 실험을 수행하였다.  A multiple-pass writing method has been implemented, which has significantly improved image placement of final ion beam masks. This method was optimized for image-size and defect performance on the e-beam lithography system. Image placement of 60nm was achieved. we could obtain an e-beam writing pattern with a line-width of ~ 80 nm and an aspect ratio of 1:5~.  실험결과는 Proximity Control 한 결과와 하지 않은 결과로 나누 어 볼 수 있는데, Proximity Control 한 결과 디자인 선 폭과 유사하 게 현상되었다. 실험은 0.086 선 폭에 종횡 비 1:4.65 인 패턴을 형성 하였다.  패턴 형성은 Proximity Control 한 결과가 계선 되었다.