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N₂ Gas Supply / LN₂ Dewar System
Airgas / Chart Industries MVE 160 HIGH ● 4+ process tools require continuous N₂ supply; cannot fabricate without itRole in QLT Fabrication
Gas Requirements by Tool
| Tool | N₂ Purpose | Flow Rate | Pressure | Purity |
|---|---|---|---|---|
| ICP-RIE (#01) | Chamber purge, leak check | 5–10 L/min (intermittent) | 20 PSI | 99.999% (UHP) |
| ALD (#23) | Carrier gas, purge | 5 L/min (continuous during deposition) | 20 PSI | 99.999% |
| PECVD (#24) | Carrier gas | 5 L/min (continuous) | 20 PSI | 99.999% |
| Sputterer (#25) | Chamber backfill | 2 L/min (intermittent) | 20 PSI | 99.999% |
| Glove Box (#35) | Inert atmosphere, antechamber purge | 5–50 L/min (antechamber cycles) | 55 PSI | 99.99% |
| Fume hood / general | Atmosphere control | Variable | Low | 99.99% |
| General bench use | Blow-dry samples | < 1 L/min | 20 PSI | Industrial OK |
| Wire bonder (#31) | Bond head purge | < 1 L/min | 5 PSI | 99.99% |
Total Consumption Estimate
| Category | Daily Use (L/min avg × hours) | Daily Volume |
|---|---|---|
| Process tools (ALD + PECVD + RIE) | ~15 L/min × 4 hr active | 3,600 L |
| Glove box (antechamber cycles) | ~10 L/min × 2 hr | 1,200 L |
| General purge, sample dry | ~2 L/min × 8 hr | 960 L |
| Total daily | ~5,800 L/day (~5.8 m³/day) | |
| Monthly | ~120 m³ |
At 120 m³/month, K-cylinders (6.5 m³ each) would require ~18 cylinders/month ● impractical and expensive.
→ Bulk LN₂ dewar is the cost-effective solution for sustained operations.
Technical Specifications
| Tool | N₂ Purpose | Flow Rate | Pressure | Purity |
|---|---|---|---|---|
| ICP-RIE (#01) | Chamber purge, leak check | 5–10 L/min (intermittent) | 20 PSI | 99.999% (UHP) |
| ALD (#23) | Carrier gas, purge | 5 L/min (continuous during deposition) | 20 PSI | 99.999% |
| PECVD (#24) | Carrier gas | 5 L/min (continuous) | 20 PSI | 99.999% |
| Sputterer (#25) | Chamber backfill | 2 L/min (intermittent) | 20 PSI | 99.999% |
| Glove Box (#35) | Inert atmosphere, antechamber purge | 5–50 L/min (antechamber cycles) | 55 PSI | 99.99% |
| Fume hood / general | Atmosphere control | Variable | Low | 99.99% |
| General bench use | Blow-dry samples | < 1 L/min | 20 PSI | Industrial OK |
| Wire bonder (#31) | Bond head purge | < 1 L/min | 5 PSI | 99.99% |
| Category | Daily Use (L/min avg × hours) | Daily Volume |
|---|---|---|
| Process tools (ALD + PECVD + RIE) | ~15 L/min × 4 hr active | 3,600 L |
| Glove box (antechamber cycles) | ~10 L/min × 2 hr | 1,200 L |
| General purge, sample dry | ~2 L/min × 8 hr | 960 L |
| Total daily | ~5,800 L/day (~5.8 m³/day) | |
| Monthly | ~120 m³ |
| Parameter | Specification |
|---|---|
| Cylinder size | T (standard, 6,500 L at STP) or K (5,700 L) |
| Purity | 99.999% (Grade 5, UHP) |
| Pressure | 2,200 PSI (full) |
| Price per cylinder | $50–$100 (gas) + $10–$20/month rental |
| Cylinders per month (at 120 m³/month) | ~18 ● impractical for sustained use |
| Cylinders per month (initial R&D at 30 m³/month) | ~5 ● manageable |
| Monthly cost (initial R&D) | $400–$700 (gas + rental) |
| Delivery | Same-day (Airgas local) or next-day ⚡ |
| Space | Cylinder rack (4–8 cylinders, manifolded) |
| Parameter | Specification |
|---|---|
| Dewar | Chart MVE 160/195 or Airgas Microbulk |
| Capacity | 160 L LN₂ → ~130 m³ N₂ gas (at STP) |
| Refill cycle | Every 3–4 weeks at QLT R&D consumption |
| Gas output | 1–15 L/min from dewar head; regulated to 20 PSI |
| Purity | 99.999% (inherently from LN₂ vaporization) |
| Price per fill | $100–$200 |
| Monthly cost | $200–$400 |
| Annual cost | $2,500–$5,000 |
| Delivery | Airgas scheduled refills; dewar loaner/rental program |
| Space | Floor footprint ~0.5 m × 0.5 m |
| Safety | LN₂ cryogenic hazard; O₂ monitor required |
Process Integration
Initial Setup (K-Cylinder Configuration)
- Install cylinder rack in ventilated area (outdoor wall or inside lab with ventilation)
- Secure 4 cylinders to wall with chains or rack restraints
- Install 4-cylinder automatic switchover manifold
- Connect 2-stage UHP regulator at manifold outlet; set delivery to 60 PSI
- Run 1/4" stainless tubing from manifold to each tool location
- Install point-of-use regulators at each tool (set to 20 PSI typical)
- Pressure test all connections; check with snoop (leak detection soap)
- Install O₂ monitor in lab room ● MANDATORY safety equipment
- Open cylinder valves ● verify pressure at each POU regulator
- System operational ● begin process tool commissioning
Transition to Bulk LN₂ Dewar
- Contact Airgas local office for microbulk LN₂ program
- Install dewar in lab or adjacent utility area (floor load: ~200 kg full)
- Connect dewar head to existing gas manifold (dewar replaces cylinders as source)
- Verify delivery pressure and flow rate
- Schedule automatic refills with Airgas (every 3–4 weeks)
Vendor Options & Pricing
| Supply Option | Vendor | Monthly Cost | Annual Cost | Setup Cost |
|---|---|---|---|---|
| K-cylinders (initial R&D) | Airgas, Linde, Matheson | $400–$700 | $5,000–$8,500 | $1,500 (manifold, regulators) |
| Bulk LN₂ dewar (160L) | Airgas microbulk | $200–$400 | $2,500–$5,000 | $500 (dewar rental) |
| Nitrogen generator (PSA) | Parker, Atlas Copco | $40 (electricity) | $500 | $8,000–$15,000 (generator) |
Facility Requirements
| Parameter | Specification |
|---|---|
| Cylinder storage | Outdoor or ventilated area; chained to wall; away from heat sources |
| Dewar location | Indoors (lab) or adjacent utility area; adequate ventilation |
| Gas lines | 1/4" stainless or copper tubing; pressure-tested at 1.5× working pressure |
| Regulators | 2-stage, UHP-rated, CGA 580 ($200–$500 each); need 1 per manifold + 1 per tool |
| O₂ monitor | MANDATORY ● wall-mounted with audible + visual alarm at 19.5% O₂ |
| Manifold | 4-cylinder automatic switchover manifold ($500–$1,500) |
| Ventilation | Adequate room ventilation (ACH ≥ 6 recommended for labs with gas systems) |
| Signage | N₂ gas hazard sign at each cylinder/dewar location |
| Emergency shutoff | Quarter-turn ball valve at manifold outlet for emergency gas shutoff |
Safety & Handling
| Hazard | Risk | Mitigation |
|---|---|---|
| Asphyxiation (N₂ displaces O₂) | HIGH in small rooms | O₂ monitor MANDATORY; alarm at < 19.5% O₂; never work alone with large N₂ release |
| LN₂ cryogenic burns | MEDIUM (when handling dewar) | Cryo-rated gloves; face shield; training |
| High-pressure cylinder rupture | VERY LOW | Secure to wall with chains; never drop; use proper regulator; inspect annually |
| Cylinder falls | MEDIUM | Chain/strap all cylinders; use approved cylinder carts for transport |
| Gas line leak | LOW | Pressure test on installation; periodic leak check with snoop |
Emergency Procedures
| Scenario | Action |
|---|---|
| O₂ monitor alarm sounds | Evacuate room immediately; open doors/windows; do NOT re-enter until O₂ > 19.5% |
| LN₂ spill from dewar | Evacuate area; ventilate; LN₂ will evaporate ● O₂ displacement is the hazard |
| Cylinder leak (hissing sound) | Close cylinder valve if safe; evacuate if large release; ventilate room |
| Person collapses near N₂ source | Drag to fresh air; call 911; begin CPR if not breathing; do NOT enter O₂-depleted area |