Mironova Labs · technical resource
ALD Deposition Protocols
Step-by-step process guidelines for Zr(TMHD)₄, Cu(TMHD)₂, and Gd(TMHD)₃
- Category
- Process Guide
- Zr / Cu / Gd Systems
Zr(TMHD)₄ / O₃ → ZrO₂ Films
ZrO₂ is a critical high-k dielectric for DRAM capacitors and CMOS gate stacks. Zr(TMHD)₄ is a crystalline solid requiring elevated deposition temperatures and ozone as the mandatory co-reactant — molecular H₂O fails to yield saturative, self-limiting growth because the activation energy to cleave the tightly bound TMHD ligands is insufficient without concurrent pyrolysis. The strict ALD window exists between 375 °C and 400 °C with a stable GPC of 0.24 Å/cycle. Below 375 °C, ozone combustion of the ligand is incomplete, increasing residual carbon. Above 400 °C, thermal auto-decomposition introduces a parasitic CVD contribution.
| Parameter Category | Specific Parameter | Recommended Value / Range |
|---|---|---|
| Delivery | Source temperature (bubbler) | 180–200 °C |
| Delivery | Carrier gas flow | 100–200 sccm (N₂ or Ar) |
| Delivery | Delivery line temperature | 215–230 °C (must exceed source temp) |
| Delivery | Precursor pulse duration | 2.0–4.0 s |
| Delivery | Precursor purge duration | 5.0–10.0 s |
| Co-Reactant | Oxidant species | Ozone (O₃) — mandatory |
| Co-Reactant | O₃ concentration | 150–200 g/m³ in O₂ |
| Co-Reactant | O₃ pulse duration | 3.0–5.0 s |
| Co-Reactant | O₃ purge duration | 10.0 s |
| Reactor | Substrate temperature (ALD window) | 375–400 °C |
| Reactor | Reactor pressure | 1.0–2.0 Torr |
| Growth | GPC | 0.24 Å/cycle |
| Growth | Film density | ~5.6 g/cm³ (crystalline phase) |
Notes & applicability
- Target thickness cycles: 5 nm ≈ 208 cycles, 10 nm ≈ 416 cycles, 50 nm ≈ 2080 cycles.
- Films within the ALD window are predominantly crystalline as-deposited (monoclinic + orthorhombic/tetragonal). Post-deposition RTA at 500–600 °C in N₂ for 60 s stabilizes the high-k tetragonal phase. Avoid annealing above 600 °C on bare Si to prevent parasitic interfacial SiO₂ growth.
- Substrates: p-type Si(100) or PVD TiN bottom electrodes. Si substrates require RCA clean + 1% HF dip (60 s) for H-terminated surfaces. Caution: HF is acutely toxic — institutional HF safety training, calcium gluconate gel, and HF-specific PPE are mandatory. Consult your site EHS program.
- Verify saturation curves (GPC vs pulse time) in your specific reactor before production use.
- Safety: Ozone at 150–200 g/m³ is a strong oxidizer and acute inhalation hazard (OSHA PEL 0.1 ppm). Ensure proper exhaust, ozone destruct systems, and area monitoring are in place before operating.
Cu(TMHD)₂ → Cu Metal Films
Metallic copper ALD using Cu(TMHD)₂ presents significant nucleation challenges. On dielectric surfaces, reduced Cu atoms exhibit extreme adatom mobility promoting 3D island growth rather than continuous film formation. A metallic seed layer (Ru, Pt, Pd, or Co, typically 2–5 nm via PVD or secondary ALD) is mandatory for immediate, robust nucleation. Molecular H₂ is inefficient at removing the TMHD ligand below 400 °C; hydrogen plasma or tertiary butyl hydrazine (TBH) are the recommended reducing agents. Safety note: TBH is a hydrazine-class compound with acute toxicity and flammability hazards — review SDS and institutional handling protocols before use. H₂ plasma requires appropriate electrical lockout and gas handling safety measures.
| Parameter Category | Specific Parameter | Recommended Value / Range |
|---|---|---|
| Delivery | Source temperature (bubbler) | 120 °C (liquid above 77 °C MP) |
| Delivery | Carrier gas flow | 100 sccm (Ar) |
| Delivery | Delivery line temperature | 135–140 °C |
| Delivery | Precursor pulse duration | 3.0–5.0 s |
| Delivery | Precursor purge duration | 5.0 s |
| Co-Reactant | Primary reductant | H₂ plasma (300 W RF, H₂/Ar mix) or TBH |
| Co-Reactant | Reductant pulse duration | 10.0 s |
| Co-Reactant | Reductant purge duration | 10.0 s |
| Reactor | Substrate temperature | 100–180 °C (PE-ALD); 150–350 °C (thermal) |
| Reactor | Reactor pressure | ~1.0 Torr |
| Growth | GPC on Ru/Pt seed | 0.36–0.70 Å/cycle |
| Growth | Best resistivity | 8 µΩ·cm (60 nm); 15 µΩ·cm (25 nm) |
Notes & applicability
- Without plasma or catalytic seed, no copper growth is observed below ~400 °C.
- A CVD component may appear around ~250 °C with plasma — verify thickness vs cycles linearity and saturation vs pulse time.
- Target thickness cycles (at 0.36 Å/cycle): 5 nm ≈ 139 cycles, 10 nm ≈ 278 cycles.
- Attempting ALD Cu directly on bare dielectrics will result in agglomerated, highly resistive nanoparticles.
Gd(TMHD)₃ / O₃ → Gd₂O₃ Films
Gd₂O₃ is a high-k dielectric with excellent performance as a passivation layer on III-V compound semiconductors. Gd(TMHD)₃ avoids the extreme moisture sensitivity and handling difficulties of alternative Gd precursors like Gd(CpCH₃)₃. The self-limiting ALD window is centered at 250–300 °C with a GPC of 0.3 Å/cycle. The Gd(TMHD)₃/O₃ process exhibits a beneficial self-cleaning effect on III-V substrates, displacing residual arsenic oxides during initial ALD cycles.
| Parameter Category | Specific Parameter | Recommended Value / Range |
|---|---|---|
| Delivery | Source temperature (evaporation) | 140–170 °C |
| Delivery | Carrier gas flow | 150 sccm (N₂) |
| Delivery | Delivery line temperature | 185 °C |
| Delivery | Precursor pulse duration | 0.8–3.0 s |
| Delivery | Precursor purge duration | 1.0–5.0 s |
| Co-Reactant | Oxidant species | Ozone (O₃) — mandatory |
| Co-Reactant | O₃ concentration | ≥150 g/m³ |
| Co-Reactant | O₃ pulse duration | 2.0–3.0 s |
| Co-Reactant | O₃ purge duration | 2.0–8.0 s |
| Reactor | Substrate temperature (ALD window) | 250–300 °C |
| Reactor | Reactor pressure | 1.0–2.0 Torr (~2–3 mbar) |
| Growth | GPC | 0.3 Å/cycle |
| Growth | Film crystallinity | Cubic C-type (bixbyite) above 250 °C |
Notes & applicability
- Target thickness cycles: 5 nm ≈ 167 cycles, 10 nm ≈ 333 cycles, 50 nm ≈ 1667 cycles.
- Films below 250 °C are amorphous and oxygen-rich. At 300 °C, carbon drops to ~2.3 at.% and hydrogen to ~1.7 at.%.
- At 350 °C, hydrogen incorporation increases to ~12.5 at.%, indicating precursor decomposition — stay within the 250–300 °C window.
- Thickness uniformity at window temperatures: ~1–2% over 10 cm flow direction.
- III-V substrates (GaAs, InGaAs): strip native oxides with 10% NH₄OH or BOE immediately before loading. Note: BOE (buffered oxide etch) contains HF — follow HF safety protocols.
- Safety: Ozone processes require proper exhaust and ozone destruct systems. See Zr(TMHD)₄ section above for ozone handling details.
References
Zirconia Thin Films by Atomic Layer Epitaxy: A Comparative Study on the Use of Novel Precursors with Ozone
Putkonen M, Niinistö J, Kukli K, et al.
Zr(thd)₄/O₃ ALD window at 375–400 °C, GPC 0.24 Å/cycle, monoclinic ZrO₂ with <0.5 at.% C and H impurities by TOF-ERDA.
DOI 10.1039/B105272CAtomic Layer Deposition of ZrO₂ Thin Films Using Zr(thd)₄ and Ozone
Niinistö J, et al.
Confirms self-limiting growth plateau at 375–400 °C with 0.24 Å/cycle GPC. ZrO₂ films exhibit k = 24–32 and leakage of 3.3 × 10⁻⁶ A/cm² at 1 MV/cm.
Vapour Pressure and Heat Capacities of Metal Organic Precursors: Y(thd)₃ and Zr(thd)₄
Fulem M, Růžička K, et al.
Peer-reviewed vapor pressure measurements for Zr(thd)₄. Sublimation enthalpy 85.36 ± 3.60 kJ/mol. Sublimes effectively at 180–220 °C under vacuum (~0.1–1.0 Torr).
DOI 10.1016/j.jcrysgro.2003.12.016Trends in Copper Precursor Development for CVD and ALD Applications
Gordon PG, Kurek A, Barry ST
Comprehensive review of Cu precursors. Cu(thd)₂ is fluorine-free (vs Cu(hfac)₂ HF corrosion), but industry trending toward Cu(I) amidinates for low-T metallic Cu ALD.
Growth of (111)-Textured Copper Thin Films by Atomic Layer Deposition
Mane AU, Shivashankar SA
Cu(thd)₂ ALD using H₂ reduction yields highly textured Cu films. Vaporization at ~120–140 °C. Process is substrate/catalyst-dependent.
DOI 10.1016/j.jcrysgro.2004.11.143Atomic Layer Chemical Vapour Deposition of Copper
Mane AU, Shivashankar SA
Cu resistivities from ~4.25 µΩ·cm (20 nm) to ~1.78 µΩ·cm (120 nm) with excellent adhesion on TiN/TaN at 300 °C.
DOI 10.1016/j.mssp.2004.09.094Gadolinium Oxide Thin Films by Atomic Layer Deposition
Niinistö J, Petrova N, et al.
Gd(thd)₃/O₃ ALD: self-limiting at ~300 °C, GPC ~0.3 Å/cycle. Film impurities: ~2.3 at.% C, ~1.7 at.% H. Cubic C-type Gd₂O₃ above 250 °C.
DOI 10.1016/j.jcrysgro.2005.08.002Plasma-Enhanced Atomic Layer Deposition and Etching of High-k Gadolinium Oxide
Vitale SA, et al.
PE-ALD using Gd(iPrCp)₃ + O₂ plasma: higher GPC (~1.4 Å/cycle at 250 °C) but narrower window and moisture sensitivity compared to Gd(thd)₃.
DOI 10.1116/1.3664756
Evaluate our precursors
Mironova Labs manufactures electronic-grade TMHD precursors in Fairfield, NJ. Request evaluation quantities for qualification against your process recipes.
Safety & regulatory notice
- For research use only. Process parameters must be verified and optimized for your specific reactor, substrate, and integration requirements.
- Consult the Safety Data Sheet (SDS) for each precursor and co-reactant before use. Some processes involve hazardous materials (ozone, hydrogen plasma, HF-containing etchants, hydrazine-class reductants) that require specialized training, engineering controls, and institutional safety review.
- Performance benchmarks cited are drawn from published literature under specific conditions. Actual results depend on equipment, process integration, and substrate preparation.
- Mironova Labs supplies precursor materials only. Film properties and device performance are the responsibility of the process integrator.