Metrology-characterization and simulation of Line Width Roughness (LWR) Evangelos Gogolides,

1. Metrology-characterization and simulation of Line Width Roughness (LWR) Evangelos Gogolides, Vassilios Constantoudis, George Patsis Institute of Microelectronics NCSR "Demokritos" Attiki - Greece (in affiliation with lithographic materials team of P. Argitis) More Moore-Excite Joint meeting, Athens May 12, 2005

2. Outline • LWR metrology-characterization methodology • 1. Off line detection of line edges and line widths • from top down CD-SEM images • 2. Characterization of LWR :The importance of • sigma(L) curve • 3. LWR and CD variation - LWR descriptors • B. Simulation of lithography materialand process • effects on LWR

3. A.LWR metrology-characterization methodology • Off line software for the detection of line edges from top down • CD-SEM images middle inner outer threshold Normalized pixel intensity SEM image after noise smoothing Determine the pixel size in nm and the noise smoothing parameters Intensity profile for a pixel row Edge detection algorithm at each pixel row using a threshold value Obtain the line edges of the image (outer,inner or middle) A line edge LER : yi,R(L) of all the edges line width or gate length LWR : δyiof all the lines Line length or gate width For uncorrelated and parallel edges : Patsis GP, Constantoudis V, Tserepi A, et al. Quantification of line-edge roughness of photoresists. I. A comparison between off-line and on-line analysis of top-down scanning electron microscopy images J. VAC SCI TECHNOL B 21 (3): 1008-1018 MAY-JUN 2003

4. A.LWR metrology-characterization methodology 500 L 400 300 L y (pixels) 200 L 100 0 0 50 100 150 200 250 300 350 400 450 500 x (pixels) 2. Characterization of LWR: The importance of sigmaLWR(L) curve • Why sigmaLWR(L) curve : sigma not a value BUT a function, sigma(L) curve • Parameters for sigma(L) curve determination: • 1) sigma(inf): the sigma for the infinite line length • 2) LS: sigma-correlation length sigma(LS)=0.9*sigma(inf). • For L>Ls the line edges look flat (no correlations) andsigma(L)sigma(inf) • 3)α : roughness exponent giving the relative contribution ofhigh frequency roughness • to LWR. It is related to fractaldimension d=2-α Constantoudis V, Patsis GP, Tserepi A, et al. Quantification of line-edge roughness of photoresists. II. Scaling and fractal analysis and the best roughness descriptorsJ. VAC SCI TECHNOL B 21 (3): 1019-1026 (2003)

5. A.LWR metrology-characterization methodology The physical meaning of α, Ls • Influence of α, Ls on: a) sigmaLWR(L) curve b) edge morphology 1. Different α, the same sigma,Ls α=0.2 α=0.8 3. Different Ls, the same sigma,α LS=300 LS=600

6. A.LWR metrology-characterization methodology 3. LWR and CD variation : estimating sigmaLWR(inf) using finite line lengths The key relationship : sigmaLWR2(inf)= sigmaLWR2(L)+ CDvariation 2(L)+ rmssigma 2(L) variation of sigmaLWR values • sigmaLWR(inf): a line length independent parameter that can be estimated using any line length A new parameter for LWR definition ? Also, • A new meaning for α,Ls : control the partition of sigmaLWR(inf) in LWR and CD variation as line length L decreases (L<Ls) See paper 5752-141- V. Constantoudis et al. in Metrology Session of SPIE 2005

7. Exposure Top Top - - Down Down View View LER LER in 2D Mask Developer Side Deprotected Deprotected Front LER Molecular View (Accurate) Resist structure LER B. Simulation of material and process effects on LWR Schematic flowchart of simulator

8. SIMULATION OF ACID DIFFUSION AND MOLECULAR WEIGHT EFFECTS ON LER

9. Top Top - - Down Down View View LER LER in 2D Side Front LER View (Accurate) LER SIMULATION OF ACID DIFFUSION AND MOLECULAR WEIGHT EFFECTS ON LER