Resist modeling, Simulation and Line-End Shortening effects

1
Resist modeling, Simulation and Line-End
Shortening effects

• SFR Workshop
• November 8, 1999
• Mosong Cheng and Prof. Andrew Neureuther,
• Berkeley, CA

We use experiment and simulation to investigate
photoresist performance and provide mechanism
based models, characterization methodology,
accurate profile simulation and support
models/fast algorithms for including resist in
OPC. Current investigations include chemically
amplified resist modeling - LES and SFR K2G,
electric-field-enhanced post-exposure bake, fast
imaging algorithm for 2-dimensional OPC
2
Resist-model-based line-end shortening simulation

• APEX-E , UVIIHS, K2G parameter-extraction
  methodology
• Simulation flow

Problem Top to Top underestimates
diffusion Problem Microstepper at Berkeley has
insufficient image quality
3
K2G resist DRM curves and reaction/diffusion/outg
asing model

• DRM curves, dissolution rate is lower at the top
  if no TARC.

Collaboration with Jacek Tyminski Nikon

• Reaction/diffusion/outgasing model

4
K2G resist modeling and simulation

• Modeling methodology

Extracting dissolution parameters
Large-area exposure
Extracting reaction rate
Resist profile simulation
Fitting with DRM data
Extracting diffusivity

• Fitting DRM curves

• Resist profile simulation

5
Electric-field-enhanced post-exposure bake

• Goal shorten PEB time, improve vertical resist
  profile uniformity, reduce lateral acid
  diffusion.
• Principle vertical electric field enhance the
  vertical movement of photoacid, hence enhance the
  reaction cross-section. PEB time as well as
  lateral acid diffusion can be reduced.
• Experimental Setup

Al foil
wafer
Al foil
Hotplate
Resist
E
photoacid
6
Electric-field-enhanced post-exposure bake status

• Experiment done in summer 1999, on UVII resist
  using JEOL.

RESIST
RESIST

• UVII resist, 0.5µm L/S, dose 20µC/cm2, PEB with
  100kHz, 3.3V AC, 140oC, 60sec.

• UVII resist, 0.5µm L/S, dose 20µC/cm2, nominal
  PEB,140oC, 90sec.

7
Fast resist imaging algorithm for 2-dimensional
OPC(submitted to SPIE99)

• Assume 2-D reaction/diffusion. Let
  f(x,y,t)Cas(x,y,t), g(x,y,t)Ca(x,y,t).

Contains Spatial Laplacian and Uses 3rd Order
Splines

• Time-advancing scheme

Based on NT Aliasing and NL Relaxation

Very Fast as only requires repeated
multiplication with fixed coefficients

• Iterative solve c2,d2, to minimize the error E.

8
Fast resist imaging algorithm simulating flow
and tuning parameters

• Simulating and tuning flow

resist profile
Mask pattern
aerial image
Resist imaging
SPLAT
Resist parameter tuner
Differential
Method of Feasible Direction
SEM picture

• Extract resist parameters by tuning the image to
  fit with SEM picture.

9
Targeted Opportunities in Resists and Tools 2000
- 2002

• Complete comparison of Simulation and SEM's of
  printed features in K2G resist, quantify the
  accuracy of the resist model.
• Complete coding of the fast but approximate image
  processing like algorithm and assess speed and
  accuracy against rigorous simulation in STORM.
• Initiate tool-process-dependent line-end
  shortening investigation by identifying key
  factors contributing to line-end shortening and
  suggesting approaches for control and
  compensation tuning.