RLS Trade-Off: Questions about Molecular Size and Quantum Yield

Transcription

1 RLS Trade-Off: Questions about Molecular Size and Quantum Yield Robert Brainard and Craig Higgins Supported by SEMATECH and Rohm and Haas 10/2/08 1

2 Outline I. Introduction II. III. IV. Effect of Molecular Weight Quantum Yield Ultra High PAG Resists V. Conclusions and Questions 10/2/08 2

3 RLS Trade-Off 1 New materials/approaches are needed to break-through to new performance surfaces: Reduction in Polymer Molecular Weight Resolution Increasing Quantum Yield Sensitivity LER Surfaces defined by Z-Parameter or K LUP LER (nm) EUV-2D Base Study EUV LER 100nm EUV LER nm [Base] E size (mj/cm 2 ) (1) Brainard, DARPA Review /2/08 3

4 II. Effect of Molecular Weight Can we reduce LER by decreasing the size of the polymer? In this conference: 61% of the papers about new resist materials are about Molecular Glasses Polymer Radius of Gyration R g = 3-4 nm Diameter = 6-8 nm 10/2/08 4

5 II. Effect of Polymer M w on LER: EUV-2D using NA in New Polymers M w = 3-33 Kg/mol Changes in M w will alter dissolution properties: Vary [PAG] and [base] Radius (nm) Radius of Gyration In THF Smallest Sphere Density = 1 g/ml 100 nm Line 8 nm 3-σ LER M K g/mol w 8 nm R g = 2-6 nm Diameter = 4-12 nm 23 nm R = nm Diameter = nm 10/2/08 (2) Cutler & Brainard, SPIE

6 [PAG] and [Base] Variations over Wide Polymer M w Range Round 1 Round 2 Round 3 6 Mws Changing UFTLs 6 Mws, 6 [PAG] Constant UFTL Changing Eo 6 Mws 6 [PAG], 6 [Base] Constant UFTL, Eo Eo (mj/cm2) DUV Eo UFTL UFTL (nm) Eo (mj/cm2) DUV Eo UFTL UFTL (nm) Eo (mj/cm2) DUV Eo UFTL UFTL (nm) Polymer Mw Kg/mole Polymer Mw Kg/mole Polymer Mw Kg/mole UFTL = Unexposed Film Thickness Loss or Dark Loss 10/2/08 6

7 M W has no effect on LER Round 1 Round 2 Round 3 6 Mws Changing UFTLs 6 Mws, 6 [PAG] Constant UFTL Changing Eo 6 Mws 6 [PAG], 6 [Base] Constant UFTL, Eo EUV LER (3σ), nm EUV LER (3σ), nm EUV LER (3σ), nm Polymer Mw Kg/mole Polymer Mw Kg/mole Polymer Mw Kg/mole LER is UNAFFECTED by an order of magnitude change in polymer M w when UFTL is held constant. 10/2/08 7

8 II. Molecular Glasses (MG) Start Small BG hν CO 2 H Stay Small PAG HO 3 S 1) (My observation) Positive Molecular Glasses DO NOT show improved LER, unless they are fairly slow. 2) Negative resists look good Because of polymer formation? 3) Champion resists appear to result from polymeric resists. 10/2/08 8

9 Questions about the role of Molecular Size: (1) Our polymer Mw work was performed in 2003 at NA. Should it be repeated at 0.3 NA and/or IL? (2) Should Molecular Glass Resists be included in a systematic study against polymeric resists? 3) Why do negative MG resists appear to give good LER/Sensitivity? Must polymers be involved for top performance? 10/2/08 9

10 III. Can we Beat RLS by Increasing Film Quantum Yield? We propose that higher quantum yield will allow us to go from Here Here to Increased quantum yield can break the RLS tradeoff LER Gregg Gallatin: 3 1 α Q E R 3 with no penalty to sensitivity. Film Quantum Yield = Number of Acids Generated in the Film Number of Photons Absorbed in the Film 10/2/08 (3) Gallatin, EUV Symposium

11 Quantum Yield Increases with PAG Concentration Eo (mj/cm2) C-Parameter Eo [PAG] (wt%) C-Parameter Film Quantum Yield [PAG] (wt%) Used Szmanda Base-Titration Method # Acids Generated = [PAG](1 e (-CE) )(6.02 x ) 10/2/08 11

12 Higher [PAG]: Higher FQY Lower Z 3,4 LER 2 (nm 2 ) (B) 10% PAG 5% PAG 7.5 % PAG 10% PAG (3) Gallatin, EUV 2007 Symposium (4) Wallow, Higgins and Brainard, SPIE CD 3 E size (1E-9 mj nm) How far can we push [PAG]? 10/2/08 12

13 IV. Ultra High PAG Resists Question #1: Question #2: Question #3: How high can we make FQY? Do we improve RLS? Can we determine how many photoelectrons are made? PAG + e - H + EUV hν e - + h + PAG H + e - + h + + PAG H + e - + h ev e - + h + + PAG H + e - + h + + PAG H + Organic Polymer Film: Primarily C, H, O Film Quantum Yield [PAG] 10/2/08 13

14 IV. High PAG Resist Platforms for FQY and Imaging RLS Study Resist Formulations Polymer O O Base TBAH OH- OH 65/20/15 Photoacid Generator (PAG) Iodonium PAG (I+) DTBI-PFBS Sulfonium PAG (S+) TPS-PFBS (5) Hassanein, Higgins, Thackeray, Brainard et al SPIE (2008) 10/2/08 14

15 Film Quantum Yields vs. [PAG] I+ AMET I+ BMET S+ BMET 12.5 Film Quantum Yield I + S + I + FQY = ~10 H + / EUV hν S + FQY = ~4 H + / EUV hν [PAG] (mol/l) (6) Brainard, Higgins et al., Journal of Photopolymer Science and Tech. (2008) 10/2/08 15

16 Resolution of Ultra-High PAG Resists 120 nm 100 nm 80 nm 60 nm 50 nm 45 nm 40 nm 5 wt% (0.083 mm) 7.5 wt% (0.123 mm) 15 wt% (0.247 mm) 20 wt% (0.330 mm) 30 wt% (0.532 mm) 40 wt% (0.697 mm) Iodonium PAG 80 nm Film Thickness 1:1 Line/Space through PAG Loading 10/2/08 16

17 Resolution of Ultra-High PAG Resists Resolution ( p (nm) ) I+ 125 nm FT I+ 80 nm FT S+ 125 nm FT Patterning Issues at Very High PAG Loadings: I+ 125 nm FT: - Adhesion Failure I+ 80 nm FT: - Pattern Collapse [PAG] (wt%) S+ 125 nm FT: - Top Loss Resolution is consistent, then degrades at > 20% PAG 10/2/08 17

18 Sensitivity of Ultra-High PAG Resists Esize (100 nm L/S) Data: Dose (mj/cm 2 ) I+ 125 nm FT I+ 80 nm FT S+ 125 nm FT - Saturated at 15-20% PAG Eo Data: 2 - Saturated at 15-20% PAG [PAG] (wt%) All data obtained from BMET 10/2/08 18

19 LER of Ultra-High PAG Resists nm Half-Pitch 10 I+ 80 nm 8 LER (nm) 6 4 S+ 125 nm I+ 125 nm [PAG] (wt%) LER is consistent, then degrades > wt% PAG 10/2/08 19

20 Exposure Latitude, Acid Diffusion and K LUP Exposure Latitude decreases with [PAG] Iodonium PAG Sulfonium PAG Exposure Latitude Curves: half pitch 120 nm 100 nm 80 nm 60 nm 50 nm 45 nm Exposure Latitude Curves: half pitch 120 nm 100 nm 80 nm 60 nm 50 nm 45 nm [PAG] (wt%) [PAG] (wt%) All Data at 125 nm Film Thickness 10/2/08 20

21 Acid Diffusion Increases with [PAG] Acid Diffusion Length (nm) I+ 125 nm FT I+ 80 nm FT S+ 125 nm FT Acid diffusion was determined from exposure latitude using the following method: 7 MTF DIFF EL NILS [PAG] (wt%) Why does L D increase for increasing PAG? 10/2/08 21 (7) Van Steenwinckel, Lammers, Koehler, Brainard, and Trefonas JVST (2005)

22 Ultra-High PAG Resist Performance: K LUP K LUP I+ 80 nm FT S+ 125 nm FT I+ (125 nm) FT [PAG] (wt%) Normalized Value nm Line/Space Resolution Esize Resolution LER EL Sensitivity 0.2 LER Exposure Latitude [PAG] (wt%) Best performance is at ~20% PAG: Sensitivity Gains are Cancelled by Acid Diffusion Increases 10/2/08 22

23 V. Conclusions and Additional Questions LER and Resolution Appear to be Flat with [PAG], but then degrades at > 30% PAG. Sensitivity improves, but then flattens out. EL decreases/ diffusion increases with [PAG] The KLUP analysis shows that the sensitivity gains are cancelled by the increased diffusion. 10/2/08 23

24 Why do the improvements in sensitivity stop? 10/2/08 24 Style borrowed from Chris Anderson

25 Why do the improvements in sensitivity stop? Dose (mj/cm 2 ) I+ 125 nm FT 8 6 I+ 80 nm FT S+ 125 nm FT 4 E size 2 Eo [PAG] (wt%) a) Base is being overwhelmed b) Used all available electrons (but why the high FQY for I+?) c) Not enough deblocking groups 10/2/08 25

26 Why does diffusion increase with [PAG]? 10/2/08 26

27 Why does diffusion increase with [PAG]? a) Film T g may change b) Acid solubility parameter may change c) More free volume for acid to diffuse d) Base is being overwhelmed 0.5 Exposure Latitude 140 Acid Diffusion Exposure Latitude nm 100 nm 80 nm 60 nm 50 nm 45 nm Acid Diffusion Length (nm) [PAG] (wt%) [PAG] (wt%) 10/2/08 27

28 V. Planned and Possible Future Work 1) Verify Film Quantum Yield Results (SEMATECH Funded In Collaboration with G. Denbeaux) a) Use direct method for determining optical density b) Use acid sensitive dye to directly measure acid generation 2) Test Low Diffusion Material and Processes a) Lower PEB temperature Increased generated acids no longer need to diffuse as far b) Increase TBA deblocking group in polymer [TBA] may be limiting deblocking rate in high [PAG] Optimize surface for better adhesion 10/2/08 28

29 Will Smaller Molecules give better LER? 10/2/08 29

30 V. Possible Future Work 3) Side-by-side comparison of polymeric and MG resists using: 10 X range in Polymer Mw Best MG available High Resolution tools (BMET 0.3 NA, PSI IL) Apples-to-Apples comparison (K LUP or Z Parameter) 10/2/08 30

31 Break-Through Strategies: An Editorial Higher Absorption Molecular Glass (Pos) Molecular Glass (Neg) Resolution LER Higher Quantum Yield High E RED PAGs Sensitivity Ultra-High PAG Surfaces defined by Z-Parameter or K LUP Anisotropic Diffusion 10/2/08 31

32 Acknowledgements CNSE: Craig Higgins Srividya Revuru Alin Antohe Greg Denbeaux Richard Matyi Rohm and Haas: Jay Machevich Charlotte Cutler Jim Thackeray Peter Trefonas Kathleen Spear SEMATECH: Jacque Georger Kim Dean Andrea Wüest Berkeley: Patrick Naulleau Applied Math Solutions: Gregg Gallatin Chris Anderson 10/2/08 32

33 Future Work We propose that higher quantum yield will allow us to improve resolution, LER with no penalty to sensitivity. This Work - Increased the # of Acids - Saturated Sensitivity Improvement - Used Constant Process Future Work: Increased generated acids no longer need to diffuse as far 10/2/08 33

34 What is Film Quantum Yield? Traditional Quantum Yield vs. Film Quantum Yield EUV hν 92 ev e - + h + PAG H + e - + h + + PAG H + e - + h ev e - + h + + PAG H + e - + h + + PAG H + Organic Polymer Film: Primarily C, H, O Experiments are done in transparent solvents Light is primarily absorbed by single molecules Light is absorbed by everything in the film. Multiple electrons are made. FQY of Acid > 1 QY < 1 Quantum Yield Moles of Product Moles of Photons Absorbed Film Quantum Yield Moles of Acids Generated in the Film Moles of Photons Absorbed by the Film 10/2/08 34