Semiconductor Quartz Glass for the Wafer Fab

Six material properties make fused silica the default choice for front-end semiconductor process hardware. Each one protects either device performance or wafer yield.

Extreme Thermal Stability

Quartz operates continuously at 1200°C and softens only at 1680°C. Its geometry holds steady through thousands of furnace cycles, far beyond the range of borosilicate or most ceramics.

Chemical Inertness

Fused silica resists H₂SO₄, HNO₃, HCl and H₂O₂, and does not react with standard process gases. This keeps your process chemistry clean and controlled.

Contamination Control

High-purity fused silica introduces no metallic ions into the silicon lattice. This is the core reason fabs depend on semiconductor-grade quartz — purity protects yield.

Dimensional Precision

Quartz has near-zero thermal expansion. Wafer-boat slots stay consistent across thousands of furnace cycles, so geometry stays stable under extreme heat.

Optical Transparency

Clear-grade quartz transmits UV through infrared light. This enables in-situ pyrometry inside the furnace and supports UV-based processes directly.

Thermal Shock Resistance

Near-zero expansion stops cracks during fast temperature changes. Quartz survives rapid heat ramps that break other glass types, so it outlasts alternatives in high-cycle production.

FGQuartz makes the complete range of front-end quartzware for thermal, CVD and wet-cleaning process modules. Standard sizes ship from stock. Custom components are made to drawing from the same Lianyungang facility. For the full engineering background, see our semiconductor quartz products guide.

The quartz process tube is the heart of every thermal furnace stack. FGQuartz makes tubes for horizontal and vertical furnaces, used in oxidation, diffusion, annealing and CVD. Clear grade suits pyrometry-enabled furnaces; opaque grade suits insulating liner duty. Tube ends come plain, flanged or ground to sealing surfaces.

Horizontal & vertical · Clear & opaque · 150 / 200 / 300 mm

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A quartz wafer boat holds dozens of wafers in the furnace and must keep precise slot positions across thousands of cycles — no warping, no particle generation, no slot-edge chipping. FGQuartz boats are CNC-machined from solid quartz blocks for better rigidity than rod-assembled designs, with no weld joints to cause contamination.

Flat-slot / V-groove / U-groove · 100–300 mm · CNC from solid

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Gas uniformity across the furnace load controls film-thickness uniformity. FGQuartz injector tubes and rings are drilled with diamond tooling, with hole patterns matched to your specification for precise local gas-flow control. Compatible with nitrogen, oxygen, HCl, TCA, SiH₄ and other standard process gases.

Diamond-drilled · Custom hole pattern · CFD-matched

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Wet cleaning is the most chemically aggressive step in the fab. Quartz tanks survive hot piranha, SC1, SC2 and HF-based sequences. FGQuartz tanks are fusion-welded — no adhesives, no gaskets, no metal fittings that could leach contamination. Overflow weirs, drain spigots and heater housings are built directly into the quartz body.

Fusion-welded · Piranha / SC1 / SC2 / HF · Built-in weirs

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Furnace hardware matters as much as the process tube itself. FGQuartz makes flanges and endcap assemblies with polished sealing faces for O-ring or knife-edge vacuum interfaces, plus opaque quartz liners for thermal insulation. All hardware is dimensionally matched to its process tube for compatible thermal expansion during cycling.

Polished sealing faces · O-ring / knife-edge · Opaque liners

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New tool generations often need quartzware no catalogue supplies. FGQuartz runs a dedicated CNC machining centre with diamond and CBN tooling to turn, mill, drill and grind fused silica into complex 3D parts. Send drawings in DXF, STEP or IGES, or a sample part for reverse engineering. Prototype quantities down to a single piece are welcome.

DXF / STEP / IGES · Reverse engineering · Single-piece OK

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Each front-end process module relies on specific quartz components. Here is which parts are involved and why fused silica is the right material for each step.

Thermal diffusion drives boron, phosphorus, arsenic and antimony into the silicon crystal at high temperature, creating the doped regions that define transistor behaviour. The quartz process tube holds this chemistry, so its purity is non-negotiable — any metal that leaches from the wall ruins the device. Gate-oxide growth by thermal oxidation demands even higher tube cleanliness. FGQuartz diffusion tubes cover 150, 200 and 300 mm batches, with matching endcaps and flanges in the same grade.

CVD deposits thin films — polysilicon, silicon nitride, silicon dioxide, tungsten — when reactive gas breaks down at high temperature. Low-pressure CVD improves uniformity across the batch. The gas injector is the most geometry-sensitive part: reactive gas is consumed as it flows, so a simple end-feed gives thick films at the inlet and thin films at the exhaust. Injector tubes with precisely positioned holes correct this. FGQuartz makes injectors to your hole pattern, typically derived from CFD modelling of the tool.

Ion implantation damages the silicon crystal and leaves dopant atoms in the wrong positions. Annealing heals the damage and activates the dopant. Rapid thermal annealing does this in seconds; furnace annealing is slower but processes larger batches. In furnace annealing, opaque quartz liners improve temperature uniformity along the tube. In RTP, a quartz window between the lamp array and the wafer transmits intense near-infrared radiation, and its optical quality directly affects temperature uniformity across the wafer.

Wet cleaning happens at many points in the wafer flow, removing particles, metals and surface films. The RCA sequence uses hydrogen peroxide with ammonia or HCl; piranha strips organics; HF removes native oxide. Quartz tanks are the standard vessel because fused silica resists every chemistry here except HF — and for HF work we use grades with minimal surface micro-defects. All FGQuartz tanks are fusion-welded from flat plate, with no adhesive joints or metal fittings in the chemical zone.

Epitaxial silicon grows a single-crystal layer with a precisely controlled dopant profile, which demands an extremely clean thermal environment. In barrel-type reactors, a large quartz bell jar encloses the susceptor and wafer stack. The jar must be transparent to near-infrared so the lamp array heats the susceptor through it while the jar stays cooler. In-situ HCl etching periodically cleans the walls, and the bell jar must survive this without generating particles. FGQuartz supplies bell jars, liner tubes and auxiliary hardware for atmospheric and reduced-pressure reactors.

Gate-oxide growth is one of the most demanding fab processes. A thin silicon-dioxide layer forms the gate dielectric in every transistor, and its quality sets switching speed and leakage current. The quartz tube furnace is the standard tool, and tube purity is critical here — trace sodium or iron from the wall degrades oxide quality directly, cutting performance and yield. FGQuartz supplies high-purity tubes for gate-dielectric growth, matching existing specs or developing new dimensions, with endcaps and gas hardware in the same grade.

Choosing the right quartz component goes beyond dimensions. Grade selection, surface preparation and handling all affect cleanroom results. For a deeper treatment, read our semiconductor quartz products guide.

Clear and opaque quartz are both silicon dioxide, but they behave very differently. Opaque quartz contains microscopic voids that scatter and absorb light instead of transmitting it. Use clear quartz when light transmission matters — process tubes observed by pyrometry, UV lamp envelopes and RTP windows. Use opaque quartz when thermal insulation matters — furnace liners, baffles and spacers. Mixing the grades incorrectly causes heat leakage and temperature non-uniformity across the batch.

Hydroxyl (OH) groups in the glass network affect optical behaviour, and they matter most in two wavelength regions. High-OH (wet) quartz transmits UV more effectively — choose it for deep-UV lithography, excimer laser optics and UV sterilisation. Low-OH (dry) quartz is better for LPCVD and high-temperature furnace work, because residual moisture from high-OH quartz can shift film chemistry and add unwanted oxygen to the process ambient. The wrong grade leads to subtle but measurable film-property shifts across the batch.

Quartz process tubes do not last forever. Repeated thermal cycling builds stress, and exposure to HCl, dopant vapours and deposition gases slowly changes the inner-surface chemistry. Devitrification is the key failure mode to watch — a crystallisation process that produces a milky, opaque layer on clear quartz when tubes are held hot for long periods, made much worse by alkali contamination. Devitrified quartz is weaker and generates particles. Inspect tubes for surface milkiness, flange-joint cracking and slot-edge chipping, and replace proactively rather than waiting for failure.

New quartz components must be cleaned and thermally pre-conditioned before entering a production furnace. The standard protocol has three steps: clean with acid; rinse with DI water and dry completely; pre-bake in a dedicated qualification furnace. This removes manufacturing and machining residues and lets the quartz outgas adsorbed water before it contacts product wafers. FGQuartz can supply components pre-cleaned to incoming-inspection standards, reducing the lab work required at your site.

Fused silica is made by two routes. Natural fused silica melts high-purity natural quartz crystal; careful raw-material selection reaches very low metallic-impurity levels. Synthetic fused silica is made by flame hydrolysis or CVD of precursors such as SiCl₄, reaching the highest purity available but at a significant price premium. For most semiconductor furnace quartzware, natural high-purity fused silica is the right choice — it delivers the required contamination performance at a far more competitive price. FGQuartz advises on grade selection by process node and contamination budget.

Quartz components are fragile, and bare-hand contact transfers sodium and potassium from skin oils that can persist through cleaning and recontaminate at high temperature. Handle all quartz with clean nitrile or latex gloves in a cleanroom or clean-bench. Store it in sealed polyethylene bags, away from HF vapour, humidity and vibration. Store tubes horizontally on padded supports to prevent long-term sag under their own weight. FGQuartz packages all outgoing components in cleanroom-grade materials and includes handling guidance with each shipment.

Send us your drawings or sample parts. The FGQuartz engineering team will review your requirements and respond with a detailed quotation within 24 hours. Explore related solar photovoltaic quartz or the full application library.