AIT-1: LER and Chemically Amplified Resists. AIT-4: Aberrations AIT-5: Maskless, High-NA, Immersion, EUV, Imprint

Transcription

1 Advanced Issues and Technology (AIT) Modules Purpose: xplain the top advanced issues and concepts in optical projection printing and electron-beam lithography. h AIT-1: R and Chemically Amplified Resists AIT-: Resolution nhancement and PSM * AIT-3: Small Features and Defects AIT-4: Aberrations AIT-5: Maskless, High-NA, Immersion, UV, Imprint ach module is a 0-5 min presentation of about a dozen slides. Suggested reading: Griffin: Plummer, Deal and Chapter 5 Sheats and Smith: 14-3, 3, Wong: 34-37, 71-90, Fig 4.1, Fig. 4.10,

2 Perturbation Model of Image Contributions ( 1+ x ) = 1+ x + x ( ) = Consider a composite electric field made up of a large electric field and a small electric field that are time- harmonic, possibly out of phase and θ S θ oriented in a co-linear direction. S C = + S = e jθ + The intensity it is proportional to the electric field times its conjugate I = C C = + S e jθ S C Phasor Diagram in complex plane [ ( )] j θ S Re e S θ + S [ ( ) ] j θ = S θ I I + I I S Re e + I S Small Very Small

3 Basic Types of Small Features Square ine Transparent I I PAK-TS x I x I PAK-T Pin Hole Scratch Opaque - Pin Spot I I DIP-OS x Chrome Stringer I x I DI P-O ARN

4 Intensity Models for Small Features S = Square, = ine T = Transparent, O = Opaque I PAK-TS = 8.5 [d/(λ/na)] 4 I PAK-T = sqrt(i PAK-TS ) I DIP-OS = 1 sqrt(i PAK-TS ) I DIP-O = 1- sqrt[sqrt(i PAK-TS )] Small mask openings produce a point itspread shaped ddistribution ib ti with an intensity proportional to the square of the area.

5 Peak and Minimum i Intensity for Small Features ARN SST 000

6 Phase-Defects 1ee j0 Me jφ Stops Reradiates Severity Factor for interaction is [1-Mcos(φ)] Worst case is a factor of f when φ = 180 o

7 Phase Defects May Print Worse Out of Focus Severity Factor [1-Mcos(φ)] becomes [] when phase of defocus is included. Wantanabe, et al. M = field transmission amplitude

8 Defect Feature Interaction A 0.5 λ/na square defect produces only a 3% clear field intensity but a 17% intensity increase which in turn causes a 1% linewidth change. The linewidth change is independent of the pin-hole shape and proportional to the area of the pin-hole. The size of the region affected is the diameter of the point spread function. ΔI ΔI Δ = = Image _ Slope I X Neureuther, Shen JVST

9 Defect and Feature Interaction

10 Defect and Feature Interaction Defects near features are much more likely to print and cause a linewidth variation proportional to the defect area.

11 Defects: Model - Small Features A phase defect has an impact ~ (1- Mcos φ) compared to a binary defect due to the combination of diffraction and subtraction of the out of phase signal. (Here M is the electric field transmission of the defect) A phase defect may have an increased tendency to print when out of focus due to the relative path length change of large angle rays with defocus combining with the phase of the defect to total 180 o. Isolated defects should be less than about 0.35 λ/na or half the minimum feature size. Defects adjacent to an isolated feature of nearly similar phase should be less than 0.5 λ/na or one third the feature size. Defects adjacent to and isolated feature of nearly opposite phase should be less than 0.18 λ/na or one fifth the features size. In arrays or contacts t where marginal image quality occurs, defects may need to be an additional factor of 1.4 smaller.