small angle x-ray scattering (saxs)
**Small Angle X-ray Scattering (SAXS)** is a non-destructive analytical technique that characterizes nanoscale structures (1-100 nm) by measuring the elastic scattering of X-rays at very low angles (0.1-5°), where the scattering pattern encodes information about particle size, shape, size distribution, and spatial correlations within thin films, porous materials, and nanocomposites. SAXS probes electron density fluctuations at length scales much larger than atomic spacing, complementing wide-angle XRD which characterizes crystal structures.
**Why SAXS Matters in Semiconductor Manufacturing:**
SAXS provides **non-destructive characterization of porosity, nanostructure, and phase separation** in advanced materials, essential for developing and monitoring porous low-k dielectrics, self-assembled structures, and nanoparticle-containing films.
• **Porous low-k characterization** — SAXS measures pore size distribution, porosity fraction, pore interconnectivity, and pore wall density in ultra-low-k dielectrics (k < 2.5), critical parameters that determine mechanical strength and reliability during integration
• **Grazing-incidence SAXS (GISAXS)** — Performing SAXS at grazing incidence to thin films provides 2D scattering patterns that reveal in-plane and out-of-plane nanostructure ordering, essential for characterizing directed self-assembly (DSA) block copolymer patterns
• **Critical dimension SAXS (CD-SAXS)** — X-ray scattering from periodic structures (line/space gratings, contact arrays) measures average pitch, CD, sidewall angle, and line edge roughness across macroscopic areas, providing statistically robust measurements complementary to CD-SEM
• **Nanoparticle sizing** — SAXS determines particle size distributions in CMP slurries, photoresist formulations, and colloidal suspensions with nm resolution, ensuring specification compliance for process-critical materials
• **Self-assembly monitoring** — SAXS tracks microphase separation, domain ordering, and long-range periodicity in block copolymer films during thermal or solvent annealing for DSA-based patterning
| Application | Scattering Geometry | Measured Parameter | Resolution |
|------------|--------------------|--------------------|------------|
| Porous Low-k | Transmission or GISAXS | Pore size, porosity | 1-50 nm |
| DSA Patterns | GISAXS | Domain spacing, order | 5-100 nm |
| CD Metrology | Transmission SAXS | Pitch, CD, SWA, LER | ±0.1 nm |
| CMP Slurry | Transmission | Particle size distribution | 1-100 nm |
| Thin Film Morphology | GISAXS | Correlation length, ordering | 2-200 nm |
**Small angle X-ray scattering is an increasingly critical metrology technique for semiconductor manufacturing, providing non-destructive, statistically representative characterization of nanoscale porosity, self-assembled patterns, and critical dimensions that enables development and process control of porous dielectrics, DSA lithography, and advanced patterning at sub-10nm technology nodes.**