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DI Water System
Manufacturer: HIGH ● Contaminated rinse water deposits particles on chip → scattering loss → failed deviceRole in QLT Fabrication
DI (deionized) water is used at every wet processing step to rinse chemical residues from chip surfaces:
| Process Step | Chemical Removed | Water Quality Needed | Rinse Duration |
|---|---|---|---|
| Post-develop rinse | Photoresist developer (TMAH) | 18.2 MΩ·cm; < 1 ppb TOC | 2–5 min cascade |
| Post-etch BOE rinse | Buffered HF (BOE) | 18.2 MΩ·cm | 5–10 min cascade |
| Post-piranha rinse | H₂SO₄/H₂O₂ piranha | 18.2 MΩ·cm | 5–10 min cascade |
| Post-RCA clean | SC-1 and SC-2 solutions | 18.2 MΩ·cm | 3–5 min each |
| General sample rinse | Any contaminant | 15+ MΩ·cm | 1–3 min |
| Wet bench (#06) continuous flow | All above | 18.2 MΩ·cm | Continuous |
| Final rinse before deposition | All contaminants | 18.2 MΩ·cm | 5 min, final QDR |
Water Quality Requirements
| Parameter | Target | Why | Standard |
|---|---|---|---|
| Resistivity | 18.2 MΩ·cm (theoretical maximum) | Ionic contaminants → surface deposits → scattering | ASTM D1193 Type I |
| TOC (total organic carbon) | < 5 ppb | Organics leave residue film on waveguide surfaces | ASTM D5997 |
| Particles (> 0.22 μm) | < 1 per mL | Particles cause waveguide scattering (> 0.1 dB/cm loss) | ASTM F1094 |
| Bacteria | < 1 CFU/mL | Biofilm on chip surfaces | USP <1231> |
| Silica | < 1 ppb | SiO₂ particles clog fine features | ASTM D4517 |
| Metals (Na, K, Fe, Cu) | < 0.01 ppb each | Metal contamination → carrier recombination in semiconductors | SEMI F63 |
Why DI Water Quality Matters for Photonics
Unlike electronics where contamination affects electrical properties, in photonics, contamination directly affects optical transmission:
- A single 0.5 μm particle on a waveguide core = 0.5+ dB scattering loss at 1550 nm
- Ionic film (even nm-thick) changes effective refractive index → mode mismatch
- Organic residue absorbs at telecom wavelengths → insertion loss increase
- Our waveguide loss budget is < 2 dB/cm ● contamination from poor rinsing can consume this entirely
Technical Specifications
| Process Step | Chemical Removed | Water Quality Needed | Rinse Duration |
|---|---|---|---|
| Post-develop rinse | Photoresist developer (TMAH) | 18.2 MΩ·cm; < 1 ppb TOC | 2–5 min cascade |
| Post-etch BOE rinse | Buffered HF (BOE) | 18.2 MΩ·cm | 5–10 min cascade |
| Post-piranha rinse | H₂SO₄/H₂O₂ piranha | 18.2 MΩ·cm | 5–10 min cascade |
| Post-RCA clean | SC-1 and SC-2 solutions | 18.2 MΩ·cm | 3–5 min each |
| General sample rinse | Any contaminant | 15+ MΩ·cm | 1–3 min |
| Wet bench (#06) continuous flow | All above | 18.2 MΩ·cm | Continuous |
| Final rinse before deposition | All contaminants | 18.2 MΩ·cm | 5 min, final QDR |
| Parameter | Target | Why | Standard |
|---|---|---|---|
| Resistivity | 18.2 MΩ·cm (theoretical maximum) | Ionic contaminants → surface deposits → scattering | ASTM D1193 Type I |
| TOC (total organic carbon) | < 5 ppb | Organics leave residue film on waveguide surfaces | ASTM D5997 |
| Particles (> 0.22 μm) | < 1 per mL | Particles cause waveguide scattering (> 0.1 dB/cm loss) | ASTM F1094 |
| Bacteria | < 1 CFU/mL | Biofilm on chip surfaces | USP <1231> |
| Silica | < 1 ppb | SiO₂ particles clog fine features | ASTM D4517 |
| Metals (Na, K, Fe, Cu) | < 0.01 ppb each | Metal contamination → carrier recombination in semiconductors | SEMI F63 |
| Parameter | Specification |
|---|---|
| Manufacturer | Thermo Fisher Scientific |
| Model | Smart2Pure 12 UV/UF |
| Input | Municipal tap water (any potable water, 1–40°C) |
| Purification stages | Pre-filter → RO membrane → UV (185/254 nm) → DI polish → UF membrane → 0.22 μm final |
| Output quality | Type I: 18.2 MΩ·cm; < 5 ppb TOC |
| Flow rate | Up to 12 L/hr (polishing cartridge); 2 L/min dispense |
| Storage tank | 6–12 L internal reservoir with UV recirculation |
| UV oxidation | Built-in 185/254 nm UV lamp (destroys organics + bacteria) |
| Ultrafiltration | 0.05 μm UF membrane (removes endotoxins + particles) |
| Final filter | 0.22 μm point-of-use filter |
| Pre-treatment | RO (reverse osmosis) module included |
| Resistivity meter | Digital display; continuous monitoring with alarm |
| Alarm | Low-quality alarm if resistivity drops below set threshold |
| Dispense | Hand dispenser with flow control |
| Power | 120 VAC, ~200 W |
| Dimensions | ~50 × 50 × 60 cm (benchtop or floor-standing) |
| Weight | ~30 kg (without water) |
| Price | $5,000–$10,000 |
| Delivery | 2–4 weeks |
| Parameter | Specification |
|---|---|
| Model | Milli-Q IQ 7000 (PN: ZIQ7000T0) |
| Output quality | 18.2 MΩ·cm; < 2 ppb TOC (best in class) |
| Flow rate | Up to 15 L/hr; 2.5 L/min dispense |
| Monitoring | IoT-enabled; real-time resistivity, TOC, temperature monitoring via Q-POD |
| Smart features | Predictive cartridge life; mobile app alerts; data logging |
| UV oxidation | Dual-wavelength UV (185 + 254 nm) |
| Ultrafiltration | BioPak UF module (0.05 μm) optional |
| Price | $12,000–$18,000 |
| Delivery | 2–4 weeks |
| Notes | Gold standard in semiconductor/pharma; higher ongoing cartridge costs |
Process Integration
Initial Installation
- Position system near wet bench (#06) ● minimize DI water travel distance (prevents recontamination in long tubing)
- Connect tap water via 3/8" or 1/2" fitting to system inlet
- Connect drain for RO reject water to sink drain
- Plug in power (120 V outlet)
- Initial purge ● run system for 1 hour to flush all stages
- Verify output ● resistivity should read > 18.0 MΩ·cm on system display
- System operational ● dispense into clean PFA or quartz beakers
Daily Use
- Check resistivity on display before use (should be > 18.0 MΩ·cm)
- Dispense DI water into clean vessel using hand dispenser
- For wet bench: Connect DI output to wet bench rinse tank via PTFE or PFA tubing
- For post-etch rinse: Use cascade rinse (overflow from clean to dirty tank) for best rinsing
- After use: System remains in recirculation mode to maintain quality
Post-Chemical Rinse Protocol (Example: BOE Etch)
- Remove chip from BOE solution; hold in air briefly to drain
- Rinse 1: Quick rinse in DI water beaker (sacrificial ● absorbs bulk HF)
- Rinse 2: 5-minute cascade rinse in clean DI water tank
- Rinse 3: Final rinse under flowing DI water dispenser (30 seconds)
- Dry: N₂ blow-dry (from N₂ supply #33)
- Verify: Measure resistivity of final rinse water ● should return to > 17 MΩ·cm
Vendor Options & Pricing
| Model | Manufacturer | Output Quality | Flow | Price (New) | Delivery |
|---|---|---|---|---|---|
| Barnstead Smart2Pure 12 UV/UF | Thermo Fisher | 18.2 MΩ·cm; < 5 ppb TOC | 12 L/hr | $5,000–$10,000 | 2–4 weeks |
| Milli-Q IQ 7000 | MilliporeSigma | 18.2 MΩ·cm; < 2 ppb TOC | 15 L/hr | $12,000–$18,000 | 2–4 weeks |
| ELGA PURELAB Flex | Veolia | 18.2 MΩ·cm; < 5 ppb TOC | 10 L/hr | $6,000–$10,000 | 2–4 weeks |
| Labconco WaterPro PS | Labconco | 18.2 MΩ·cm | 6 L/hr | $4,000–$7,000 | 2–4 weeks |
Facility Requirements
| Parameter | Specification |
|---|---|
| Water input | Standard tap water connection (3/8" or 1/2" fitting) |
| Drain | Standard sink drain for RO reject water (~3:1 reject:product ratio) |
| Power | Standard 120V outlet |
| Floor space | 0.5 × 0.5 m (benchtop) |
| Location | Near wet bench (#06) ● minimize DI water travel distance |
| Temperature | Standard lab (15–30°C); feed water 1–40°C |
| Tubing to wet bench | PTFE or PFA tubing (not PVC ● leaches plasticizers) |
| Dispense vessel | PFA, PTFE, or quartz beakers (not glass ● leaches boron/silica) |
Safety & Handling
| Hazard | Risk | Mitigation |
|---|---|---|
| Electrical (water + power) | LOW | GFCI outlet; keep power connections dry |
| Slip hazard (water on floor) | LOW | Clean spills immediately; anti-slip mat near system |
| UV exposure (from UV lamp) | VERY LOW | UV lamp is enclosed inside system housing |
| RO reject water waste | NEGLIGIBLE | Non-hazardous; goes to standard drain |
| Legionella (stagnant water) | VERY LOW (with UV recirculation) | System UV recirculates continuously; weekly flush if unused |