2. 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

3. 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

4. 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

5. Experiment

6. KIGAM Implantation System

7. 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

8. Factors affecting the line definition Ion Beam quality Parellelity and homogeniety dose measurement Mask Quality mask production by e-beam writer problem : approx. 1  m thick PMMA should be used - Resolution worsening distortion during irradiation 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

9. Change of molecular weight by proton irradiation Molecular weight of PMMA changes drastically by proton irradiation which enables the very well defined structure reproduction

10. Result of simulation -  m slit

11. 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

12. Comparison of Simulation and Experiment - for the case of large mask to PR distance Depth profile of PMMA after development Proton Energy : 500keV Membrane :  m Si 3 N 4 shadow width :  m Mask to PR distance : 35  m

13. Extreme Cases Depth profile of PMMA after development Proton Energy : 500keV Membrane :  m Si 3 N 4 shadow width :  m Mask to PR distance = 0 Mask to PR distance = 530  m

14. AFM results Edge configuration 500keV proton Au wire mask w/o membrane Edge configuration 800 keV proton Au wire mask with 10  m mylar membrane

15. SEM observations 500keV w/o membrane tilt angle 50 o 400keV with membrane mask to sample : contact tilt angle 50 o 450keV with membrane mask to sample :  m tilt angle 50 o

16. 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

17. 김영석, 홍완, 우형주, 최한우 한국자원연구소 이온빔응용연구그룹 김영석, 홍완, 우형주, 최한우 한국자원연구소 이온빔응용연구그룹 수백 keV 양성자를 이용한 이온빔 리소그라피의 분해능 측정 수백 keV 양성자를 이용한 이온빔 리소그라피의 분해능 측정