Barium silicon oxynitride (Ba3Si6N4O9) halogen-free redistribution-layer dielectric

The advanced semiconductor packaging industry is under structural pressure to eliminate halogens from every layer of the build-up stack — not just from laminates, but from the dielectric films that define redistribution layers (RDL). Regulatory momentum from IEC 61249-2-21 and evolving JEDEC green-package specifications, combined with customer-driven supply-chain sustainability mandates from hyperscalers and handset OEMs, is forcing OSAT houses and RF substrate makers to re-evaluate the polymer-dominated and SiCOH-based dielectric materials they have relied on for a decade. The problem is not simply halogen content: incumbent polymer RDL dielectrics carry dielectric loss tangents in the low-to-mid 10-3 range that degrade signal integrity at millimeter-wave frequencies, and SiCOH films, while CMOS-compatible, do not naturally lend themselves to halogen-free certification below the 100 ppm threshold demanded in the most stringent green-packaging specs. Barium silicon oxynitride in the composition Ba3Si6N4O9 represents a computationally identified candidate that addresses both constraints simultaneously. Its 4.48 eV bandgap — confirmed independently by three DFT calculation sources — places it well above the leakage threshold relevant to low-voltage RDL operation, and its predicted loss tangent, aggregated from the related alkaline-earth oxynitride family, sits near 1×10-3, competitive with the best-performing inorganic dielectrics in production today. Crucially, the material is intrinsically halogen-free: no fluorine, chlorine, or bromine is present in the stoichiometry, and the proposed PECVD deposition chemistry — cyclopentadienyl-barium precursor, silane co-reactant, and nitrogen anneal — introduces no halogenated species into the process ambient. This positions Ba3Si6N4O9 as a structurally differentiated answer to a forced-substitution problem, not a speculative material looking for an application. The asset sits within Lattice Graph's PFAS-free dielectric and process fluids portfolio as a lead composition filing, combining composition claims with device-use claims directed at the RDL dielectric stack configuration. At this stage it is a computationally validated early-stage composition with one critical bench measurement remaining before it can be presented as a fully de-risked material. That transparency is important: the dossier that follows presents the computational case honestly, identifies what has been proven, and names the single remaining experimental gate clearly.

Each candidate is validated by multiple independent machine-learning interatomic potentials. A material advances only when the engines agree on phonon (dynamic) stability — disagreement is surfaced, not hidden.

Ba3Si6N4O9 belongs to the alkaline-earth silicon oxynitride family — a class of materials in which barium coordinates with a mixed-anion framework of nitrogen and oxygen bound to silicon tetrahedra. The oxynitride framework is relevant precisely because nitrogen substitution for oxygen in silicate networks is well established to increase dielectric rigidity, reduce polarizability relaxation paths, and raise the bandgap relative to pure oxide analogs. The barium content provides the high atomic coordination environment that suppresses dangling-bond density at grain boundaries, which is a known source of dielectric loss in amorphous inorganic films. The stoichiometry Ba3Si6N4O9 — three barium per six silicon, with a 4:9 nitrogen-to-oxygen ratio — places the composition in a mixed-anion regime that has been associated with low phonon damping rates and high thermal stability in related alkaline-earth oxynitride compounds. The computational validation for this composition is unusually thorough for an early-stage candidate. Three independent machine-learning interatomic potentials — MACE, CHGNet, and ORB — each successfully relaxed the Ba3Si6N4O9 structure to a local energy minimum, and all three reached consensus that the structure is stable, meaning no single-potential artifact is being relied upon. This three-of-three MLIP agreement is a meaningful filter: the Lattice Graph workflow advances only candidates where independent potentials agree, and divergences trigger discard rather than averaging. Following relaxation, phonon stability was computed using the finite-displacement method implemented in Phonopy. An initial phonon calculation returned borderline results; a second, higher-convergence calculation confirmed dynamic stability — no imaginary phonon modes — indicating that the lattice does not sit at a saddle point and will not spontaneously distort at zero Kelvin. Separately, CHGNet ab initio molecular dynamics at 873 K (600°C) ran without structural decomposition, providing a thermal stability bound that comfortably exceeds the 350-450°C PECVD anneal temperatures typical in back-end-of-line processing. Equation-of-state fitting returned a bulk modulus near 86 GPa and a Debye temperature near 562 K; both values are consistent with a mechanically hard ceramic that will withstand CMP planarization and thermal cycling in a package. The 4.48 eV bandgap is the result of independent calculation by three DFT source methods, and all three are in agreement — this is not a single-functional result that might shift substantially with hybrid-functional correction. For context, a 4.48 eV gap implies a leakage floor well below detection at the sub-1 V field strengths present in RDL dielectric layers, which typically see less than 0.1 MV/cm. The loss-tangent value of approximately 1×10-3 is an aggregated estimate from the broader alkaline-earth silicon oxynitride family rather than a direct measurement of this specific composition; it is stated as a prediction, and its experimental confirmation is the single open validation gate. The PECVD integration scheme — cyclopentadienyl-barium (Cp2Ba) as the barium precursor, silane for silicon, with N2/NH3 anneal to establish the oxynitride stoichiometry — is adapted from precedents in barium-containing oxide PECVD and is process-compatible with 200 mm and 300 mm OSAT toolsets without introduction of any halogenated precursor gases. Mechanically, an 86 GPa bulk modulus places Ba3Si6N4O9 well above polymer RDL dielectrics (which are typically sub-10 GPa) and in the range of silicon nitride. This is significant for warpage management in thin fan-out packages, where CTE mismatch and film compliance determine bow budgets. A stiffer dielectric film can help offset the compliance of the organic build-up layers above and below the RDL stack, a benefit that polymer-based alternatives structurally cannot offer.

The immediate serviceable market is the redistribution-layer dielectric segment of advanced packaging. RDL dielectrics are consumed by fan-out panel-level packaging (FOPLP), fan-out wafer-level packaging (FOWLP), silicon interposer build-up layers, and high-density substrate RDL used in RF front-end modules and automotive radar chipsets. The overall advanced packaging market exceeds $50B annually, and the dielectric materials and process chemicals sub-segment that this composition addresses is estimated in the $1-5B range — recognizing that this estimate reflects the accessible portion of the market where a halogen-free inorganic dielectric can realistically displace incumbents, not the entire packaging spend. The displacement is not wholesale adoption: it is targeted at the green-packaging and high-frequency tiers where polymer dielectrics are under the most pressure. The purchasing decision for a new RDL dielectric sits primarily with OSATs (outsourced semiconductor assembly and test houses) and RF substrate manufacturers. OSATs such as ASE Group, Amkor, and JCET are already operating PECVD-capable back-end lines and are under contractual green-package obligations from their hyperscaler and handset customers. RF substrate makers serving 5G mmWave, Wi-Fi 7, and automotive radar are simultaneously under pressure to reduce loss tangent across the full interconnect stack, not just in the core laminate. Both customer profiles have near-term procurement cycles aligned with new product introduction for mmWave 5G and automotive radar programs, where signal integrity margins at 28 GHz and 77 GHz are tight enough that a 2-3× improvement in dielectric loss tangent translates directly to link-budget margin that system architects can monetize. Licensing logic for this asset is royalty-per-wafer or royalty-per-panel on the PECVD dielectric deposition step, or alternatively a materials supply agreement covering the Cp2Ba precursor chemistry. Either model is compatible with the asset's position as a composition-plus-device-use filing: the claims read on the deposited film in the RDL stack, which means any OSAT or substrate maker depositing the material in volume infringes the composition-of-matter claim regardless of whether they source the precursor from the patent holder.

halogen-free low-loss RDL dielectric with >4 eV gap

halogen-free (<100 ppm) package-integrated RDL form

The most strategically aligned acquirers are advanced-packaging OSATs with active green-packaging qualification programs and in-house PECVD capability. ASE Group, Amkor Technology, and JCET each operate PECVD lines and have publicly disclosed halogen-free packaging roadmaps tied to customer commitments from Apple, Qualcomm, and automotive OEMs. For these buyers, acquiring the composition and device-use rights to Ba3Si6N4O9 would provide a proprietary inorganic RDL dielectric option that their polymer-dielectric-dependent competitors cannot access. RF substrate manufacturers — particularly those serving 5G mmWave and 77 GHz automotive radar applications where dielectric loss is a first-order design constraint — represent a second natural buyer class. Companies such as Ibiden, Shinko Electric, and AT&S are continuously qualifying new dielectric materials for their high-frequency substrate roadmaps, and a phonon-confirmed, DFT-validated inorganic dielectric with a clean FTO position is a defensible addition to a substrate portfolio. Electronic-materials specialty chemical companies could also be strategic acquirers, particularly those that already supply Cp2Ba or silane precursors to the semiconductor industry. For such a buyer, the composition patent combined with the precursor supply position creates a bundled offering — material specification plus qualified chemistry — that is difficult for an OSAT to source elsewhere. Licensing is the most realistic near-term monetization path given the early experimental stage; outright acquisition of the patent family makes sense for a buyer that can complete the split-post resonator measurement internally and move to process qualification within an existing PECVD infrastructure.

The central technical risk is that the measured film-level loss tangent, once obtained, does not match the family-aggregate prediction of approximately 1×10-3. Amorphous PECVD-deposited films frequently exhibit higher dielectric loss than crystalline analogs due to defect-state contributions, and the Ba3Si6N4O9 stoichiometry has not yet been deposited and characterized. If the measured loss tangent falls in the 5-10×10-3 range, the differentiation versus polymer RDL dielectrics narrows substantially and the commercial case weakens. The mitigation is that the phonon calculation already establishes a low phonon-damping framework, and the mixed-anion oxynitride chemistry is structurally expected to suppress dangling-bond defect density relative to a pure nitride or oxide — but this is a prediction, not a proof. A second risk is PECVD process maturity: Cp2Ba is a thermally sensitive precursor with a relatively narrow deposition window, and achieving stoichiometric Ba3Si6N4O9 at the 4:9 nitrogen-to-oxygen ratio in a production-representative tool requires process chemistry development that has not been demonstrated. The roadmap to de-risk both issues is straightforward — deposit a representative film by PECVD, measure the loss tangent by split-post resonator, characterize the stoichiometry by XPS, and refine the anneal conditions — but it requires a buyer or licensee with PECVD capability and a millimeter-wave materials characterization lab, which limits the addressable acquirer set to well-resourced industry players rather than startup licensees.