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
4/15/2019

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
4/15/2019

3. K2G resist: DRM curves and reaction/diffusion/outgasing model
DRM curves, dissolution rate is lower at the top if no TARC.
Collaboration
with Jacek
Tyminski
Nikon
Reaction/diffusion/outgasing model
4/15/2019

4. K2G resist: modeling and simulation
Modeling methodology
Extracting dissolution parameters
Large-area exposure
Extracting reaction rate
Resist profile simulation
Extracting diffusivity
Fitting with DRM data
Fitting DRM curves
Resist profile simulation
4/15/2019

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
4/15/2019

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.
4/15/2019

7. Fast resist imaging algorithm for 2-dimensional OPC(submitted to SPIE’99)
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.
4/15/2019

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
Method of Feasible
Direction
Differential
SEM picture
Extract resist parameters by tuning the image to fit with SEM picture.
4/15/2019

9. Targeted Opportunities in Resists and Tools
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.
4/15/2019