Used Furnace Equipment: Horizontal vs Vertical LPCVD Comparison

Thermal processing remains a cornerstone of semiconductor manufacturing, with LPCVD (Low Pressure Chemical Vapor Deposition) and diffusion furnaces handling critical steps like gate oxidation, polysilicon deposition, and dopant diffusion. When sourcing used furnace equipment, buyers face a fundamental choice: horizontal or vertical configuration. This comparison examines the technical and economic factors guiding that decision.

Furnace Fundamentals

Horizontal Furnaces

Horizontal furnaces load wafers vertically in quartz boats that slide into a horizontal process tube. This was the industry standard for decades and remains common in 200mm and smaller wafer production.

Configuration:

• Process tube oriented horizontally
• Wafers stand vertically in slotted quartz boats
• Heating elements surround the tube (3-zone or 5-zone typical)
• Loading via cantilever or soft-landing system

Vertical Furnaces

Vertical furnaces load wafers horizontally on quartz shelves or paddles that rise into a vertical process tube. This design became dominant for 300mm production and offers advantages for contamination control.

Configuration:

• Process tube oriented vertically
• Wafers lie horizontally in quartz cassettes or on shelves
• Heating elements surround the tube (typically 5-7 zones)
• Loading via elevator mechanism from below

Technical Comparison

Wafer Capacity (Batch Size)

Horizontal Furnaces:

| Model | Wafer Size | Batch Size | Load Configuration | |-------|------------|------------|-------------------| | Thermco 9000 | 150mm | 100-150 wafers | 4-6 boats | | Tystar 4000 | 200mm | 100-150 wafers | 4-6 boats | | Bruce BDF-41 | 200mm | 100-200 wafers | 4-8 boats | | Thermtek TTF-2000 | 200mm | 150-200 wafers | 4-8 boats |

Vertical Furnaces:

| Model | Wafer Size | Batch Size | Load Configuration | |-------|------------|------------|-------------------| | TEL VTR | 200mm | 100-150 wafers | Single cassette | | TEL VTR-300 | 300mm | 100-150 wafers | Single cassette | | SVG 9000 | 200mm | 100-150 wafers | Single cassette | | Kokusai HiSilicon | 200/300mm | 100-200 wafers | Single cassette |

Analysis: Comparable batch sizes per system, but vertical furnaces typically achieve better wafer-to-wafer uniformity within those batches.

Temperature Uniformity

Horizontal Furnaces:

• Typical uniformity: ±1.0°C to ±2.0°C across flat zone
• Challenges: End effects (temperature drops at tube ends), gas depletion along tube length
• Mitigation: Multi-zone temperature control, tapered profile adjustments

Vertical Furnaces:

• Typical uniformity: ±0.5°C to ±1.0°C across batch
• Advantages: Symmetrical heating, better gas distribution
• Advanced systems: ±0.25°C achievable with modern controls

Impact on process:

• Poly-Si deposition: ±1°C = ±3% thickness variation
• Gate oxidation: ±1°C = ±5% oxide thickness variation

For critical processes (gate oxide, thin poly), vertical furnaces offer measurable yield advantages.

Contamination Control

Horizontal Furnace Contamination Sources:

1. Particle generation: Boat sliding against tube during load/unload
2. Wall deposits: Process byproducts coat tube walls, flake off
3. Cross-contamination: Sequential processes in same tube
4. Backside deposition: Wafers touch boat slots

Mitigation in horizontal systems:

• Soft-landing load systems (reduce particle generation)
• Frequent tube cleaning (PM every 50-100 runs)
• Dedicated tubes for specific processes
• Fork boats (minimize backside contact)

Vertical Furnace Advantages:

1. Laminar flow: Gas flows downward, particles fall away from wafers
2. No wall contact: Wafers never touch tube walls
3. Better isolation: Cassettes seal during processing
4. Minimized backside deposition: Wafers rest on minimal contact points

Particle performance:

• Horizontal: 50-200 particles/cm² (addition) typical
• Vertical: 10-50 particles/cm² (addition) typical

For sub-micron devices, this difference directly impacts yield.

Automation and Integration

Horizontal Furnaces:

• Loading: Semi-automated (operator places boats on loader)
• Integration: Limited SMIF/FOUP compatibility
• Operation: Batch recipes, manual tube cleaning
• Footprint: Long tube + loader = 6-8 meters length

Vertical Furnaces:

• Loading: Fully automated (FOUP-to-cassette)
• Integration: Native SMIF/FOUP compatibility
• Operation: Automated recipe management, self-cleaning options
• Footprint: Compact vertical design, 2-3 meters square

Vertical furnaces align with modern fab automation requirements; horizontal systems suit lower-volume or legacy operations.

Process Applications

LPCVD Polysilicon

Horizontal:

• Good for thick poly (>500 nm)
• Cost-effective for non-critical applications
• Well-established process recipes

Vertical:

• Superior thickness uniformity for thin poly (<200 nm)
• Better for doped poly (in-situ doping)
• Preferred for gate applications

LPCVD Nitride (Si₃N₄)

Horizontal:

• Standard for passivation layers
• Acceptable uniformity for >100 nm films

Vertical:

• Better for thin nitride (<50 nm) tunnel barriers
• Improved stoichiometry control
• Lower particle counts

Thermal Oxidation

Horizontal:

• Traditional gate oxidation platform
• Dry O₂, wet O₂ (pyrogenic or bubbler), N₂O processes

Vertical:

• Dominant for 300mm gate oxidation
• Better thickness control for thin oxides (<10 nm)
• In-situ measurement options

Diffusion and Annealing

Horizontal:

• POCl₃ doping, BBr₃ doping
• High-temperature anneals (up to 1200°C)

Vertical:

• RTA alternative for some anneals
• Better atmosphere control (N₂, Ar, forming gas)

Specific Models and Specifications

Horizontal Furnace Models

Thermco 9000 Series

• Wafer sizes: 100mm, 150mm, 200mm
• Temperature: Up to 1200°C
• Zones: 3-zone or 5-zone
• Features: Cantilever loader, soft-landing option
• Used price (2026): $40,000 - $100,000

Tystar 4000 Series

• Wafer sizes: 150mm, 200mm
• Temperature: Up to 1200°C
• Zones: 3-zone standard
• Features: Compact design, good for R&D
• Used price (2026): $35,000 - $80,000

Bruce BDF Series

• Wafer sizes: 150mm, 200mm
• Temperature: Up to 1250°C
• Zones: 5-zone
• Features: High-temperature capability
• Used price (2026): $50,000 - $120,000

Thermtek TTF Series

• Wafer sizes: 200mm
• Temperature: Up to 1200°C
• Zones: 5-zone
• Features: Production-proven design
• Used price (2026): $45,000 - $110,000

Vertical Furnace Models

TEL Vertical Thermal Reactor (VTR)

• Wafer sizes: 200mm, 300mm
• Temperature: Up to 1200°C
• Zones: 5-zone or 7-zone
• Features: Full automation, SMIF/FOUP
• Used price (2026): $200,000 - $500,000

SVG 9000 Series

• Wafer sizes: 200mm
• Temperature: Up to 1200°C
• Zones: 5-zone
• Features: Good mid-range option
• Used price (2026): $150,000 - $350,000

Kokusai HiSilicon

• Wafer sizes: 200mm, 300mm
• Temperature: Up to 1200°C
• Zones: 5-zone or 7-zone
• Features: Batch size up to 200 wafers
• Used price (2026): $250,000 - $600,000

Cost Analysis

Capital Cost Comparison

| Category | Horizontal | Vertical | Ratio | |----------|------------|----------|-------| | Entry-level (used) | $35,000 | $150,000 | 4.3x | | Mid-range (used) | $75,000 | $300,000 | 4.0x | | High-end (used) | $120,000 | $600,000 | 5.0x |

Operating Costs (Annual, Estimated)

Horizontal Furnace:

• Quartzware replacement: $15,000 - $30,000
• Heating elements: $5,000 - $10,000
• PM labor: $20,000 - $40,000
• Utilities: $15,000 - $25,000
• Total: $55,000 - $105,000/year

Vertical Furnace:

• Quartzware replacement: $20,000 - $40,000
• Heating elements: $8,000 - $15,000
• PM labor: $15,000 - $30,000 (less frequent)
• Utilities: $20,000 - $35,000
• Total: $63,000 - $120,000/year

Total Cost of Ownership (5-year)

Horizontal (mid-range):

• Acquisition: $75,000
• Operating: $400,000
• Total: $475,000

Vertical (mid-range):

• Acquisition: $300,000
• Operating: $450,000
• Total: $750,000

Break-even analysis: For processes where vertical furnace yield advantage exceeds 5%, the vertical system pays for itself in high-volume production.

Selection Guidelines

Choose Horizontal When:

• Budget constrained: 60-80% lower capital cost
• 200mm or smaller: Limited vertical options for smaller wafers
• Thick films: Poly >500 nm, oxide >100 nm
• Non-critical layers: Passivation, pad oxide, field oxide
• R&D or low volume: Simplicity and flexibility valued
• Legacy fab: Existing horizontal infrastructure

Choose Vertical When:

• 300mm production: Horizontal systems rarely support 300mm
• Critical layers: Gate oxide, thin poly, tunnel nitride
• High volume: Yield improvements justify premium
• Modern fab: FOUP/SMIF integration required
• Particle-sensitive devices: Sub-micron or memory devices
• Automation priority: Lights-out operation desired

Used Market Availability (2026)

Horizontal Furnaces

Availability: Excellent

• Many fabs retiring 200mm horizontal systems
• Strong supply from IDM consolidation
• Good spare parts availability (quartz, elements, controllers)

Typical sources:

• Memory fab upgrades (transitioning to vertical)
• IDM fab closures
• Research university surplus

Vertical Furnaces

Availability: Good

• Some 200mm vertical systems available as fabs upgrade
• 300mm vertical furnaces rarely available (still in production)
• Premium pricing reflects limited supply

Typical sources:

• 200mm fab closures
• Technology upgrades (older TEL VTR models)
• Equipment leasing returns

FAQ

Q: Can I upgrade a horizontal furnace to vertical?

A: No—horizontal and vertical furnaces have fundamentally different architectures. The only "upgrade" path is replacement. However, you can improve horizontal furnace performance with: soft-landing loaders (reduce particles), advanced temperature controllers (improve uniformity), and dedicated tubes for specific processes (reduce cross-contamination).

Q: What is the typical lifespan of a used furnace?

A: With proper maintenance, 15-25 years is common. Key wear components: quartzware (2-5 years), heating elements (5-10 years), insulation (10-15 years), and controllers (10-20 years). The furnace frame and pressure vessel typically outlast all other components. When buying used, budget $20,000-50,000 for immediate refurbishment.

Q: How do I evaluate a used furnace before purchase?

A: Critical checks: (1) Temperature uniformity test—run profile with thermocouples; (2) Leak check—verify base pressure and leak rate; (3) Quartzware inspection—check for cracks, devitrification, deposits; (4) Controller functionality—verify all zones control properly; (5) Loader mechanism—smooth operation, no binding; (6) Exhaust and scrubber integration—adequate capacity for your processes.

Q: Can horizontal furnaces handle 300mm wafers?

A: Very rarely. A few specialized horizontal systems were built for 300mm, but the industry standardized on vertical for 300mm production. If you need 300mm capability, vertical furnaces are essentially the only option. For 200mm and below, both configurations remain viable.

Conclusion

Horizontal and vertical furnaces each serve important roles in semiconductor manufacturing. Horizontal systems offer compelling economics for less critical processes and smaller wafer sizes, while vertical furnaces deliver the uniformity and cleanliness required for advanced device production. The used market provides excellent value for both—horizontal systems at 60-80% discount from vertical, and vertical systems at 50-70% discount from new.

For most buyers, the decision hinges on wafer size (300mm demands vertical), process criticality (critical layers favor vertical), and budget constraints (horizontal offers significant savings). Both can deliver excellent results when matched to appropriate applications.

Looking for LPCVD or diffusion furnaces? Contact Caladan Semi for horizontal and vertical furnace systems. We provide tested equipment with temperature uniformity verification, quartzware inspection, and installation support.