[JeremyYao1999]

PR: Add BGBM (Backside Grinding + Metallization) ontology modules

Summary

Adds two new semantic modules under ontology/ontology/06-osat-packaging-test/00-assembly-processes/:

• 03-backside-grinding/ontology.ttl — wafer backside grinding (thinning) semantics
• 04-backside-metallization/ontology.ttl — wafer backside metallization (BM) semantics

These fill a gap in the assembly-processes layer, which currently covers die-attach, encapsulation, and molding but is missing the wafer-preparation front-end steps (backside thinning and metallization) that precede dicing and bonding.

What's included

Backside grinding (03-backside-grinding)

Class	Description
BacksideGrindingProcess	In-feed wafer backside thinning process
RoughGrindingStep / FineGrindingStep	Coarse vs fine grinding stages
TaikoGrindingProcess	Edge-retained thinning variant for ultra-thin wafers
BacksideGrindingDefect	Scratch, crack, silicon dust, surface damage, residual stress

Properties: hasTargetThickness, hasTotalThicknessVariation (TTV).

Backside metallization (04-backside-metallization)

Class	Description
BacksideMetallizationProcess	Metal deposition on the thinned backside
ElectronBeamEvaporationProcess	E-beam evaporation deposition method
BacksideMetalStack	Metal / multi-layer stack (Au, Ag, Al, Ti/Ni/Ag)
BacksideMetallizationDefect	Metal peeling, poor adhesion

Properties: hasMetalStack.

Conventions followed

• Turtle (.ttl) under the correct layer/subcategory, per ontology/ontology/README.md.
• owl:versionInfo "0.1.0", prov:wasGeneratedBy curation activity, dc:source / dc:rights, and prov:generatedAtTime provenance on every term.
• Classes subclass assembly_processes:AssemblyProcess (consistent with existing 00-die-attach) and reuse semicont-core:Defect / semicont-core:Material from 00-shared.
• Industry-general knowledge only; no company-specific recipes or vendor differentiation.

Note for maintainers

The parent module 00-assembly-processes/ontology.ttl is still a placeholder (PlaceholderClass), while its child 00-die-attach already references assembly_processes:AssemblyProcess. Suggest promoting a real AssemblyProcess class into the parent module in a follow-up so all child modules share a consistent superclass.