A simulation analysis on defect annihilation in directed self-assembly lithography

Transcription

1 A simulation analysis on defect annihilation in directed self-assembly lithography Katsuyoshi Kodera, Hideki Kanai, Yuriko Seino, Hironobu Sato, Yusuke Kasahara, Katsutoshi Kobayashi, Hiroshi Kubota, Naoko Kihara, Yoshiaki Kawamonzen, Shinya Minegishi, Ken Miyagi, Toshikatsu Tobana, Masayuki Shiraishi, Satoshi Nomura and Tsukasa Azuma EUVL Infrastructure Development Center A part of this work was funded by the New Energy and Industrial Technology Development Organization (NEDO) of Japan under the EIDEC project. 1

2 Original simple HP 15nm L/S patterning process using PS-b-PMMA PS short defect 8 chips (9%) 85 chips / wafer average (3σ ) CD (nm) 16.9 (4.6) LWR (nm) 4.8 (1.3) LER (nm) 3.7 (1.5) OK chip 71 chips (84%) Dislocation defect 6 chips (7%) 500 nm Y. Seino et al., MNE 2014 PS short and dislocation defects are observed at the wafer center and edge after SOG etch. 2

3 Outline Grid defects Experimental behavior Simulation results acquired using self-consistent field theory(scft) Simulation results acquired using dissipative particle dynamics (DPD) Dislocation defects Summary 3

4 Outline Grid defects Experimental behavior Simulation results acquired using self-consistent field theory(scft) Simulation results acquired using dissipative particle dynamics (DPD) Dislocation defects Summary 4

5 Characteristic DSA Defect (Grid defect) Guide: Width=0.5L 0 Pitch=3L 0 PMMA PS resist SOG SOC PS Seino, MNE2014 Sato, MRS2014 Kasahara, SPIE2015. * SOG: Spin On Glass,SOC: Spin On Carbon Grid defect microphase separation dry development (PMMA removed) SOG etched shallowly SOG full etch Small Dry development or SOG RIE Large grid defects short defects short defects L/S with roughness fine L/S L/S with roughness open defects Although most of these grid defects disappeared after SOG full etching, they could result in the degradation of etching process margin, and therefore, in line edge roughness and open/short defects 5

6 Process condition dependence Annealing condition dependence * contact angle: min min min Y. Seino, MNE n m Neutral layer: contact angle dependence PMMA affinity Contact angle: 80.5 Contact angle: 81.9 PS affinity Contact angle: nm Grid defects can be decreased with optimum neutral layer and sufficient phase separation annealing. The subtle adjustment of the neutral layer toward a more neutral condition results in the decrease of the grid defects. 6

7 Simulation model film thickness=1.5l 0 top(air) periodic condition pinning height=0.68l 0 pinning width=0.5l 0 pinning period=3l 0 Pinning bottom 1.7L 0 SCF simulation, masking method BCP : χn = 20, L 0 = 30 nm (PS-b-PMMA) top: neutral (χ PMMA top = 2, χ PS top = 2) pinning: PMMA attractive (χ PMMA PIN = 1, χ PS PIN = 2) bottom: PMMA attractive (χ PMMA BTM = 1.3, χ PS BTM = 2) 7

8 Grid defect as metastable morphology Vertical Lamellar(V L) Grid Defect (GD) Mixed lamellar (ML) Side view Top-down pinning pinning pinning most stable 3 stable/metastable morphologies including grid defect were acquired using SCFT. quasi-hexagonal buried structures 8

9 Free energy ΔF Stability of grid defects Mixed lamellar state is the most stable Vertical lamellar state is the most stable mixed lamellar GD ML VL grid defect vertical lamellar PMMA attractive χ PMMA BTM neutral These simulation results agree with the experimental behavior. 9

10 Conformation of BCP chains (a)pmma chain is parallel to the bottom. n 0 ~n 5 PMMA n 9 n 5 n 0 (b) PMMA chain is vertical to the bottom junction center terminal Neutral layer(pmma-attractive bottom) n 0 > n 5, n 9 We can acquire the information of the polymer chain conformation by evaluating n0, n5 and n9 immediately above the bottom. 10

11 Conformation of BCP chain (GD-state) Density 1 n0 n 0 n5 n n9 n 9 n MMA npmma n 9 n 5 MMA Position (L 0 ) n 0 > n 5, n 9 immediately above the bottom n 0 11

12 Conformation of BCP chain (GD-state) 中性化膜に対して垂直 Vertical PMMA blocks Parallel BCP chains Top-down Vertical PMMA blocks Parallel PMMA blocks PMMA blocks are nearly vertical to the bottom in the region where the vertical PMMA lamellar patterns are connected toward the bottom. This characteristic conformation of BCP chains is considered to be related with the origin of the grid defects. 12

13 Node density biased MC method Field model terminal segment particle model GD-state junction segment Computer Physics Communications The segment density distribution acquired using SCFT was transformed into the atomic representation using the node density biased MC method. Using this atomic representation as initial chain conformations, we executed DPD simulations and investigated the defect annihilation dynamics. 13

14 DPD simulation results Firstly, grid defects were observed. And finally, the grid defects disappeared and the simulation converged into the equilibrium lamellar state. 14

15 Defect annihilation dynamics (a)initial state (GD state) (b)1000 steps (Transient state) (c)10000 steps (Equilibrium lamellar) Vertically oriented horizontally oriented Polymer chains are partially vertical. Both vertically and horizontally oriented polymer chains appeared randomly. The polymer chains flipped down and flopped up Polymer chains are parallel randomly The defect annihilation dynamics of the grid defects could be understood as the change of the orientation of the BCP chains. 15

16 Outline Grid defects Experimental behavior Simulation results acquired using self-consistent field theory(scft) Simulation results acquired using dissipative particle dynamics (DPD) Dislocation defects Summary 16

17 Polymer conformation in dislocation defects Terminal node Center node Self-consistent field theory Perfect state n center =Segment density distribution of the center node n terminal =Segment density distribution of the terminal node n center n terminal Single dislocation Double dislocation 17

18 Polymer conformation in dislocation defects Terminal segment density is larger than the center segment density. Terminal segment density is larger than the center segment density. Terminal segment is localized in a specific region. The delocalization of the terminal segments is effective for defect mitigation. 18

19 Summary We have investigated the conformations of the polymer chains in grid defects and dislocation defects. In both defective states, polymer chain conformations were found to play an important role in formation of the defective states. For practical application, it is important to understand the origin of the defective states more. We need the corporation of the simulation people more and more! 19