Mironova Labs · Technical Resource

Film Characterization Checklist

Metrology workflow for verifying ALD regime and film quality

AnalyticalAll TMHD Films

Thickness, Uniformity & Density

Primary tools for rapid, non-destructive thickness mapping and density determination of TMHD-derived thin films.

Spectroscopic Ellipsometry (SE): Use a Cauchy optical dispersion model for transparent dielectrics (ZrO₂, Gd₂O₃). Expected refractive index n at 633 nm for high-quality ALD ZrO₂: 2.10–2.20. A significantly lower n (<2.0) indicates substantial carbon contamination, porosity, or low film density.
For metallic Cu from Cu(TMHD)₂: SE modeling requires a multi-oscillator Drude-Lorentz model. A 4-point probe sheet resistance measurement is more practical.
X-Ray Reflectivity (XRR): Essential for ultra-thin films (<10 nm) to determine absolute physical thickness, interfacial layer thickness, and electron density independent of optical models. Target density for ALD ZrO₂ at 375–400 °C: 5.6–5.8 g/cm³.
Gd₂O₃ from Gd(TMHD)₃/O₃: Thickness uniformity at window temperatures (250–300 °C) is ~1–2% over 10 cm flow direction. Surface roughness ~1.2 nm rms (95 nm film at 250 °C).

Composition & Impurities (XPS Analysis)

XPS is the gold standard for detecting the most critical issue with TMHD precursors: carbon contamination from incomplete ligand combustion. Monitor specific core-level binding energies to confirm correct oxidation states and detect residual carbon.

Element / Level	Target Compound	Binding Energy (eV)	Interpretation
Zr 3d₅/₂	ZrO₂	182.3–183.6	Fully oxidized Zr⁴⁺ state
Cu 2p₃/₂	Cu metal	932.4	Cu⁰ metallic state
Cu 2p satellites	CuO (unwanted)	940–945	Incomplete reduction → residual Cu²⁺
Gd 4d	Gd₂O₃	142.0–147.4	Oxidized Gd³⁺ state
C 1s (carbonate)	Residual carbon	~289	Uncombusted carboxylate/carbonate groups

Optimized Zr(TMHD)₄/O₃ at 375 °C: carbon drops below XPS detection limit (~0.2 at.% by TOF-ERDA). Below 300 °C, residual carbon can exceed 5–10 at.%, degrading dielectric breakdown strength.
Gd(TMHD)₃/O₃ carbon trend: 9–15 at.% at 225 °C → 7 at.% at 250 °C → 2.3 at.% at 300 °C. Temperature is the primary lever for carbon reduction.
FTIR can supplement XPS to detect carbonate impurities in Gd₂O₃ films.

Crystallinity & Phase

The crystallographic phase directly dictates dielectric constant and electrical performance.

Grazing Incidence XRD (GIXRD): For ZrO₂, as-deposited films are typically a polycrystalline mix of monoclinic and orthorhombic/tetragonal phases. Post-deposition annealing drives transformation to the high-k tetragonal phase (k ≈ 30–40 vs ~20 for monoclinic).
For Gd₂O₃: Films below 250 °C are amorphous. Above 250 °C, crystalline cubic C-type (bixbyite) structure with dominant (400) reflection. Effective k ≈ 9–13 depending on process conditions.
Cu from Cu(TMHD)₂: Resistivity is the practical quality metric rather than phase analysis. Best reported: ~8 µΩ·cm at 60 nm thickness on Ru/Pt seed.

Interface Quality

For advanced device integration, interface quality is as important as bulk film properties.

Cross-sectional HRTEM: Evaluate and quantify parasitic interfacial oxide layers on Si substrates. For Gd₂O₃ on GaAs/InGaAs, validate complete absence of parasitic As₂O₃ at the semiconductor boundary to confirm clean ALD nucleation.
For MOS structures: native SiO₂ presence affects measured effective permittivity. Published Gd₂O₃ MOS data includes native oxide interface — account for this when comparing to direct-on-Si targets.
Leakage current density benchmarks: Gd(TMHD)₃/O₃ at 300 °C, ~50 nm film: <2×10⁻⁸ A/cm² at 1 V.

References

[R1] Putkonen M, Niinistö J, Kukli K, et al.. Zirconia Thin Films by Atomic Layer Epitaxy: A Comparative Study on the Use of Novel Precursors with Ozone, J. Mater. Chem. (2001). doi:10.1039/B105272C
[R2] Niinistö J, et al.. Atomic Layer Deposition of ZrO₂ Thin Films Using Zr(thd)₄ and Ozone, Thin Solid Films (2005). doi:10.1016/j.tsf.2005.08.360
[R9] Niinistö J, Petrova N, et al.. Gadolinium Oxide Thin Films by Atomic Layer Deposition, J. Crystal Growth (2005). doi:10.1016/j.jcrysgro.2005.08.002
[R11] Park PK, Kang S-W, et al.. Chlorine Contamination in HfO₂ Films Deposited by ALD Using HfCl₄, J. Phys. Chem. C (2016). doi:10.1021/acs.jpcc.5b05286