Motivation
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Motivation. IC business requires a sub 100 nm Next Generation Lithography tool. (100 nm for 16GDRAM) Any of the following 4 major candidates are not prevailing. EUV(Extreme UV) SCALPEL(SCattering with Angular Limitation in Projection Electron beam Lithography) X-ray with Synchrotron

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Motivation

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Motivation

Motivation

  • IC business requires a sub 100 nm Next Generation Lithography tool.

    • (100 nm for 16GDRAM)

  • Any of the following 4 major candidates are not prevailing.

    • EUV(Extreme UV)

    • SCALPEL(SCattering with Angular Limitation in Projection Electron beam Lithography)

    • X-ray with Synchrotron

    • IPL(Ion Projection Lithography)

  • Generally, it is assumed that due to the large lateral straggling of ions in the membrane mask, it is not possible to get high resolution with ion beam - which is not necessarily so.

  • As a first step towards Ion beam lithography (IBL) using membrane mask, it is necessary to demonstrate the good spatial resolution


Advantage and disadvantage of ibl

Advantage and Disadvantage of IBL

Advantage

  • Good sensitivity for 0.1 um pattern

    • X-ray : 375 mJ/cm2

    • e-beam : 100 uC/cm2

    • IBL : 4.5 uC/cm2 (720mJ)

  • Good intrinsic resolution

    • 10 nm : limitation not from the wavelength but from PR

Disadvantage

  • vacuum treatment

  • 1:1 membrane mask

  • lateral straggling

  • non familiar method - no extensive study


Current status of ion beam lithography

Current Status of Ion Beam Lithography

IPL

  • IMS (Ionen Mikrofabikations System) and Vienna University since 1986

  • ALG consortium in USA

  • Siemens, ASM lithography, Leica and IMS-Stuttgart formulated $36M 3-year research program in 2000

  • 0.1 um pre-production type stepper in 1999

IBL with membrane mask

  • No dominant study after the proximity IBL by Hughes Research Laboratory


Experiment

Experiment


Kigam implantation system

KIGAM Implantation System


Simulation of dose distribution at pr

Simulation of Dose distribution at PR

  • Purpose : To see and understand the dose distribution at pattern edges which is directly responsible for the edge definition in the development process

  • Simulation tool : TRIM (SRIM2000)

  • Simulation Geometry : simple infinite slit


Factors affecting the line definition

Ion Beam quality

Parellelity and homogeniety

dose measurement

Mask Quality

mask production by e-beam writer

problem : approx. 1 mm thick PMMA should be used - Resolution worsening

distortion during irradiation

Factors affecting the line definition

Development

  • precise temperature control - find the temperature at which until the midde irradiated point is developed

  • not controllable by develop time because of the statistical character of melting process


Change of molecular weight by proton irradiation

Change of molecular weight by proton irradiation

  • Molecular weight of PMMA changes drastically by proton irradiation which enables the very well defined structure reproduction


Result of simulation 1m m slit

Result of simulation - 1mm slit


Result of simulation 1m m slit1

Result of simulation - 1mm slit

Small conclusion

  • Theoretically, the edge definition can be controlled within 20 nm if the development process can be performed very precisely

  • Even taking into account the 14 - 86 % dose width, edge definition can be controlled at least within 50nm with rather rough develop condition


Comparison of simulation and experiment for the case of large mask to pr distance

Comparison of Simulation and Experiment- for the case of large mask to PR distance

Depth profile of PMMA after development

Proton Energy : 500keV

Membrane : 2mm Si3N4

shadow width : 100mm

Mask to PR distance : 35mm


Extreme cases

Extreme Cases

Depth profile of PMMA after development

Proton Energy : 500keV

Membrane : 2mm Si3N4

shadow width : 100mm

Mask to PR distance = 0

Mask to PR distance = 530mm


Afm results

AFM results

Edge configuration

500keV proton

Au wire mask w/o membrane

Edge configuration

800 keV proton

Au wire mask with

10 mm mylar membrane


Sem observations

SEM observations

400keV with membrane

mask to sample : contact

tilt angle 50o

500keV w/o membrane

tilt angle 50o

450keV with membrane

mask to sample : 25mm

tilt angle 50o


Conclusion

Conclusion

  • Simulation results show the good possibility of employing IBL using membrane mask as the NGL tool.

  • Well below 100nm pattern definition can be obtained if develop condition can be found at which only until the middle dose position at the pattern edge is developed.

  • There are still, however, many basic works to be performed before real launch. They are :

    1. The relationship between proton dose, develop condition (Temperature, time) and pattern edge (the position until which PR is developed)

    2. Mask quality (e-beam writing)

    3. Understanding the deviation of simulation result and the real measurement


Motivation

수백 keV 양성자를 이용한

이온빔 리소그라피의 분해능 측정

김영석, 홍완, 우형주, 최한우

한국자원연구소 이온빔응용연구그룹


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