NSF GOALI Interactions of Plasma/Energetic Beams with Organic Masking Materials

Gottlieb S. Oehrlein, University of Maryland College Park, DMR 0705953

University of Maryland: Plasma reactor experiments

Fig. 2: First in-situ real-time ellipsometry measurements with advanced PR materials during Ar plasma processing along with ion and optical filtering established dynamics and quantified depth, thickness and properties of PR damage due to ions and VUV radiation.

University of California Berkeley: Complementary ion , VUV, and electron beam experiments

Fig. 3 : Atomic force microscope images (1x1m2) and RMS surface roughness of PR under (a) simultaneous 150eV argon ion/VUV/1keV electron exposure and (b) simultaneous 150eV argon ion/VUV exposure for the beam system and the plasma reactor.

Substrate at 65oC, Ion flux: 2.9x1014/s cm2, VUV flux: 1.9x1014/s cm2 Argon plasma 20 s / 800W

(a) (b)Ion fluence= 1x1018 /cm2,VUV photon fluence: 6.8x1017/cm2

30 sec 10 min 30 min 60 min

Real time in-situ surface measurements and energetic beam studies clarify role of individual plasma species in advanced photoresist material/mask surface roughening

Fig. 1: Simultaneous interaction of ions, electrons, radiation … in plasma with photoresist (PR) nano patterns produces surface damage. Scientific understanding of individual & synergistic contributions of plasma species to this is required.

30 35 40 45 50 5564

65

66

67

68

69

70ion damage layer

32% H

1.4nm no bias2.6nm -100V bias

no bias-100V bias

30s

De

lta

[d

eg

.]

Psi [deg.]

2s

10s

20s

5s

5s10s

20s

60s

300sMgF2

30nm UV layer48% H

UV layer + ion damage layer

32% H

1.4nm no bias2.6nm -100V bias

The Problem

Electron fluence (mC/cm2) (from left): 1, 4, 8

Education and outreach:• Monthly meetings of academic and industrial partners - University of Maryland, University of California Berkeley, Lam Research and Dow Electronic Materials, to discuss latest results and increase collaboration among project members.• Involvement of undergraduate students Paul Lambert and Tunji Godo at University of Maryland and Zhi Chen at UC Berkeley.•Student presentations at AVS Boston 2008, along with invited presentations by PIs at international conferences.• Presentations at Dow Electronic Materials, October 2008• F. Weilnboeck, summer internship at Lam Research (2009).• Continued development of experimental techniques, simulations and data analysis methodologies to enable improved and unambiguous scientific insights.

Fig. 5: Graduate Student Ting-Ying Chung and undergraduate student Zhi Chen working on remote temperature control of water bath on the beam system at UC Berkeley.

Fig. 6: Graduate Student Florian Weilnboeck discussing with undergraduate student Tunji Godo at University of Maryland the chemical surface modifications of 193nm PR by VUV radiation as measured by XPS.

NSF GOALI Interactions of Plasma/Energetic Beams with Organic Masking Materials

Gottlieb S. Oehrlein, University of Maryland College Park, DMR 0705953

Fig. 7: Dr. Eric Hudson and Graduate Student Florian Weilnboeck during an internship at Lam Research in summer 2009.

Conclusions: For the first time real time in-situ ellipsometry was used to monitor surface and bulk material modifications of photoresist masking materials for nanoscale pattern transfer in plasma environments. This approach allowed to quantitatively measure the formation of distinguishable plasma-modified material layers with monolayer/sub-nanometer and microsecond resolution and extract thicknesses and properties of individual modified PR layers. Plasma species responsible for the observed changes in material properties have been identified by a) employing optical and ion/electron filters to selectively block out plasma species/change spectral window irradiating PR, b) employing individual beams of ions, plasma radiation and electrons. We find that key differences in mechanical properties of the plasma-modified layers, i.e. ion modified graphitic surface layer (~1 nm) and deeper (~30 nm) VUV modified layer (polymer scissioned) drive surface reorganization to reduce mechanical energy and produce plasma induced surface roughening of nanometer sized polymer masks. Significance: The understanding of plasma polymer interactions produced by these studies can be used by our industrial partners/others for rational design of next generation polymer materials (Li, Dow Electronic Materials) and plasma etching processes (Hudson, Lam Research) that minimize surface and line edge roughness of plasma transferred nanoscale patterns.