Our Approaches to EUV Resist Materials. N. Ohshima ELECTRONIC MATERIALS RESEARCH LABORATORIES RESEARCH & DEVELOPMENT MANAGEMENT HEADQUARTERS

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1 Our Approaches to EUV Resist Materials N. Ohshima ELECTRONIC MATERIALS RESEARCH LABORATORIES RESEARCH & DEVELOPMENT MANAGEMENT HEADQUARTERS Page 1 June 2008

2 Outline 1. Challenges to EUV Resist Materials 2. Technologies to Improve the Issues 3. Lithographic Performance 4. Summary Page 2 June 2008

3 1. Challenges to EUV Resist Materials Critical Issues of EUV Resist Eopt Sufficient Reduction of Outgassing LER Simultaneous Reduction of Eopt, Resolution and LER Resolution Page 3 June 2008

4 1. Challenges to EUV Resist Materials Critical Issues of EUV Resist Sufficient Reduction of Outgassing We have already achieved outgassing level below the regulation value PAG cation structure Protection group design of polymer Simultaneous Reduction of Eopt, Resolution and LER We are focusing on development of novel technologies to overcome those trade-offs Enhancement of acid image contrast Minimization of dissolution unit size Page 4 June 2008

5 1. Challenges to EUV Resist Materials Factors influencing outgassing level O O R Bulky acetal group Electron withdrawing - R-SO 3 S + group + + R R R Amine So vent OH R-SO 3 H + R O R Irradiation R-SO 3 H R + S R + R Volatile segment The most of the outgassing segment was from PAG. => Molecular design of cation unit to suppress outgassing Bulky acetal protected polymer gave little amount of outgassing during EUV exposure. Page 5 June 2008

6 1. Challenges to EUV Resist Materials Standard sample for ADT at IMEC Page 6 June 2008

7 2. Technologies to Improve the Issues Two important results leading to our design policy The first : Dependence of LWR and sensitivity on quencher amount L30P60 [nm] Ecd=30nm vs L30P EUV_Ecd=30nm Sensitivity [mj/cm2] MET@ALS EUV exposure Increasing loading amount of quencher (SPIE 2007) LWR is improved by increasing the loading amount of quencher with losing sensitivity. How would LWR be improved without losing sensitivity? Enhancement of Acid Image Contrast Page 7 June 2008

8 2. Technologies to Improve the Issues Two important results leading to our design policy The second : Dependence of resolution on polymer MW 80 nm 70 nm 60 nm 50 nm 45 nm 40 nm High Mw EUV exposure Mid. Mw Low Mw Process Condition: FT=125 nm, PB = 120 oc/ 90 sec, MS-13 Microstepper (NA=0.3), PEB = 110 oc/90sec, Deve.= TMAH 2.38% 60 sec, Resolution is improved by lowering the Mw of polymer. Minimization of Dissolution Unit Size Page 8 June 2008

9 2. Technologies to Improve the Issues An example of enhancement of acid image contrast Photo decomposable base Acid Image [H + ](x,z) exposed unexposed Initial Acid image (1) Photo decomposable base could improve the relationship between LWR and sensitivity. Base [B](x,z) Acid Image [H + ](x,z) Photo Decomposable base [B](x,z) exposed unexposed Initial Acid image (2) Page 9 June 2008

10 2. Technologies to Improve the Issues Pattern Formation Mechanism of EUVL EUV absorption / R. &2 nd e - generation EUV + e OH OH Ionization by 2 nd e - / R. &2 nd e - amplification + e + 2 e OH OH e - trap / anion generation e + Ph 3 S X Ph 3 S + X Combination of R. & anion / acid generation + X + H + X OH O Recombination of R. & e - / loss channel + e OH OH Based on the model proposed by Kozawa and Tagawa Page 10 June 2008

11 2. Technologies to Improve the Issues Diffusion Control of Electron and Acid Resist EUV e - Trap Acid Acid acceptor e - e - e - Trap Acid Acid acceptor e - e - Trap Acid Acid acceptor Electron diffusion High concentration and uniform distribution of e- traps Increase of e - trapping ability Acid diffusion High concentration and uniform distribution of acid acceptors Short e - diffusion Decrease of e - loss Increase of acid generation Short acid diffusion Page 11 June 2008

12 2. Technologies to Improve the Issues Electrons trapping ability of PAGs S Y Z X Amount of generated acid, that is electron trapping ability of PAGs, could be increased by lowering the LUMO level of PAGs. Page 12 June 2008

13 2. Technologies to Improve the Issues Results of Acid Diffusion Control (KrF Exposure) Target CD: L200P400 nm FT: 800 A Type New Sample Epot =18 mj/cm2 LWR =18.4 nm Epot =15 mj/cm2 LWR =11.2 nm Page 13 June 2008

14 2. Technologies to Improve the Issues Results of Acid Diffusion Control (KrF Exposure) Sens. vs L200P400 (KrF Exposure) L200P400 (nm) Sens. (mj/cm2) Type New Samples Sensitivity LWR relation has been improved in new samples based on acid diffusion control. Page 14 June 2008

15 3. Lithographic Performances Results of Two Diffusion Control (Exposed by LBNL) Illumination Conditions : Rot-Dipole Type FEVS mJ/cm2 New Sample-1 FEVS mJ/cm2 Resolution and LWR has been improved in new sample-1 based on electron and acid diffusion control. Page 15 June 2008

16 3. Lithographic Performances Results of Two Diffusion Control (Exposed by LBNL) Page 16 June 2008

17 4. Summary Critical issue of EUV resist materials is to improve sensitivity, resolution and LWR simultaneously. Our design policy to improve them consists of enhancement of acid image contrast and minimization of dissolution unit size. The enhancement of acid image contrast could be achieved by increasing density and ability of 2 nd electron traps and density of acid quenchers. It has been also shown that the ability of electron traps could be increased by increasing the reduction potential of PAGs. The new resist material, designed on the concept of enhancement of acid image contrast described above, has demonstrated nearly 22 nm resolution with 4.0 nm LWR in EUV exposure. Effect of molecular coagulation is under investigation to minimize the dissolution unit size. Page 17 June 2008

18 Acknowledgement Lawrence Berkeley National Laboratory Dr. Kim Dean at SEMATECH Dr. Mieke Goethals at IMEC Page 18 June 2008