Quartz Glass at the Foundation of Every Solar Cell

Est. 2005
Lianyungang, Jiangsu, China

Solar OEM Supply
CZ · DS · Cell process

High-Purity SiO₂
Crucibles to diffusion tubes

Custom Dimensions
Any furnace, any ingot size

Global PV Supply
China · SE Asia · Europe

The Czochralski quartz crucible is the most important consumable in monocrystalline silicon production. It holds a charge of polysilicon feedstock at temperatures above 1414°C for the entire duration of the crystal pull — a process that can last twelve to forty hours depending on crystal size. During this time, the inner surface dissolves slowly into the silicon melt, releasing controlled amounts of oxygen that become an intentional dopant in CZ silicon, providing precipitation-strengthening of the crystal. The crucible must survive this process without catastrophic failure while releasing oxygen at a rate that keeps the dissolved oxygen concentration within the specification window for the silicon grade being grown. FGQuartz produces CZ crucibles in standard diameters from 12-inch to 32-inch formats compatible with both single-pull and continuous-feed Czochralski pullers, with inner surface treatment options appropriate for standard, low-oxygen, and high-oxygen CZ silicon grades.

Directional solidification produces multicrystalline silicon ingots by melting polysilicon in a large square or rectangular quartz crucible and allowing the melt to solidify from the bottom upward under controlled thermal conditions. Unlike CZ crucibles, DS crucibles bond to the solidified ingot during casting and must be broken away after cooling — making them single-use items. The quartz body provides the structural containment of the melt and must not crack or collapse during the high-temperature casting cycle. FGQuartz produces DS crucibles in G5 (800×800 mm), G6 (1000×1000 mm), G7 (1170×1170 mm), and G8 (1300×1300 mm) standard ingot sizes, as well as custom dimensions for non-standard furnace platforms and cast-mono seed holder configurations.

The phosphorus emitter diffusion step is the most critical thermal process in conventional silicon solar cell manufacturing. Silicon wafers are loaded into quartz boats inside horizontal quartz diffusion tubes, and phosphorus oxychloride (POCl₃) or phosphine (PH₃) vapour flows through the tube at elevated temperature, doping the wafer surface to create the n-type emitter layer of the p-n junction. Any metallic contamination that the tube deposits on the wafer surface during diffusion will create recombination centres that reduce minority carrier lifetime and lower the open-circuit voltage of every cell made from those wafers. FGQuartz diffusion tubes are produced in standard diameters compatible with Centrotherm, Amtech, Tempress, and Kokusai tube furnace platforms in clear fused silica grade.

Quartz wafer boats carry silicon solar wafers through thermal diffusion, oxidation, and annealing furnaces, holding them vertically in precisely spaced slots to allow gas access to both wafer surfaces. Solar wafers — currently the standard 182 mm M10 and 210 mm G12 formats — are mechanically fragile and must be supported without contact stress that could cause cracking during the thermal cycle. FGQuartz produces solar wafer boats in straight-slot and V-groove configurations for M2, M4, M6, M10, G12, and other wafer formats. High-volume cell manufacturers require boats with consistent slot pitch and controlled bow to prevent wafer-to-wafer spacing variations that create non-uniformity in the diffusion profile.

Silicon nitride anti-reflection and passivation layers deposited by PECVD are standard in PERC, TOPCon, and HJT solar cells. Tunnel oxide and polysilicon layers for TOPCon require LPCVD deposition in tube furnaces. In both cases, quartz glass provides the process chamber walls, tube liners, bell covers, and substrate holders that define the deposition environment. For direct plasma PECVD systems, the quartz bell jar or process tube must survive both reactive plasma chemistry and thermal cycling of repeated deposition runs. FGQuartz manufactures PECVD bell jars, LPCVD process tubes, and tube furnace liners in clear and opaque fused silica for solar cell deposition applications, matched to major inline and batch PECVD platform geometries.

Tube furnace liners protect ceramic heating elements from chemical attack by process gases used in solar cell manufacturing — including chlorinated compounds such as TCA and HCl used for in-situ tube cleaning. Opaque quartz liners provide secondary containment and thermal insulation between the process tube and the furnace heating elements, reducing temperature gradients along the tube length and improving diffusion uniformity across the wafer load. FGQuartz supplies single-zone and multi-zone liners in both clear and opaque grades, in diameters matched to the major solar tube furnace platforms, with custom lengths for non-standard furnace configurations.

Wafer boats are loaded into and extracted from tube furnaces using quartz paddles and push rods — long quartz rods and flat blades that engage the boat at the furnace opening and slide it to the process position inside the hot tube. These tools must be made from high-purity fused silica because they enter the furnace environment and can deposit contamination onto the inner tube walls and wafer boat. FGQuartz produces paddles and push rods in solid and hollow tube configurations, in the lengths required for the furnace tube length plus the external paddle clearance, with end designs that engage standard lug and groove patterns of major wafer boat styles.

Solar wafer cleaning uses wet chemical baths — KOH or NaOH for monocrystalline silicon texturing and RCA-type cleaning sequences to remove metal contamination before thermal diffusion. High-purity rinse baths and some acid cleaning baths are performed in quartz vessels specifically to avoid recontaminating the wafer with boron or alkali metals that borosilicate tanks would leach. FGQuartz supplies fusion-welded quartz tanks for solar wafer wet process lines, including overflow weir configurations, single-tank and cascade rinse designs, and integrated drain and heating fittings for inline process equipment.

Next-generation solar cell architectures — TOPCon, HJT, IBC, and tandem perovskite-silicon cells — introduce process steps and reactor geometries that do not map to the standard tube furnace and wafer boat combinations of conventional cell manufacturing. Novel deposition chambers and custom thermal management hardware for these advanced architectures frequently require custom quartz glass components that do not exist in any catalogue. FGQuartz accepts customer drawings in DXF, STEP, or IGES format and produces custom quartz components for next-generation cell process equipment through CNC machining, oxy-hydrogen flame welding, and precision grinding. Research-scale prototype quantities are accommodated alongside production volume orders.

Passivated Emitter and Rear Cell technology remains the dominant architecture in global solar manufacturing, accounting for the majority of all cell production capacity. PERC cells require quartz glass components across every thermal step — CZ crucibles for ingot growth, diffusion tubes and wafer boats for emitter formation, PECVD process components for SiNₓ anti-reflection and rear passivation, and tube furnace hardware for oxide passivation layers. FGQuartz has built its solar product range around the PERC manufacturing sequence and maintains stock of the most commonly consumed items for rapid supply to high-volume PERC cell lines.

Tunnel oxide passivated contact technology achieves higher efficiency than PERC by eliminating the majority of recombination at the rear metal contact through a passivating polysilicon contact structure. TOPCon manufacturing adds tunnel oxide growth and LPCVD polysilicon deposition steps to the cell process flow, both performed in quartz tube furnaces. These additional high-temperature steps with ultra-thin functional oxide layers demand the highest level of quartz glass purity, since the tunnel oxide is in direct contact with the silicon and any metallic contamination creates recombination centres at maximum efficiency impact. FGQuartz supplies the quartz tube and wafer carrier hardware for TOPCon tunnel oxide and polysilicon deposition stages.

Silicon heterojunction cells combine the high open-circuit voltage of amorphous silicon passivation with the high current collection of crystalline silicon, achieving efficiencies above 24% in production. The entire cell process occurs below 250°C. HJT PECVD chambers and carrier hardware must be made from high-purity materials that do not contaminate the ultra-sensitive amorphous silicon layers, even at low temperatures where thermally driven diffusion is minimal. FGQuartz supplies quartz carrier plates and tray components for HJT deposition systems, along with quartz structural components used in the low-temperature wet cleaning steps preceding PECVD deposition.

Multi-junction solar cells based on III-V semiconductor materials achieve efficiencies above 40% under concentrated illumination and are the technology of choice for space satellite power and CPV systems. The MOCVD reactors used to grow these complex epitaxial structures require high-purity quartz reaction chamber components and substrate holder hardware that survive the organometallic precursor chemistry and high-temperature growth conditions. FGQuartz supplies MOCVD-compatible quartz chamber components and susceptor support hardware for III-V solar cell production, alongside optical components used in concentrator systems directing high-intensity sunlight onto small cells.

Perovskite-silicon tandem cells have demonstrated efficiencies above 33% in research settings by stacking a wide-bandgap perovskite top cell with a high-efficiency silicon bottom cell. Commercialisation requires the silicon bottom cell to achieve the same high passivation quality as the best standalone high-efficiency silicon cells, placing the same demands on quartz glass purity throughout the silicon cell manufacturing sequence. New perovskite deposition steps introduce process hardware requirements where quartz glass serves as deposition chamber structural components, substrate carriers, and optical elements for illumination uniformity testing.

While the market share of multicrystalline silicon has declined as PERC monocrystalline silicon has become cost-competitive, multicrystalline and cast-mono silicon cells remain in production at many facilities. DS crucibles are consumed in large quantities — each casting cycle consumes one set regardless of ingot quality. Cast-mono technology uses monocrystalline seeds in the DS furnace to produce predominantly single-crystal ingots at DS production economics. FGQuartz supplies DS crucibles in G5 through G8 sizes for both conventional multicrystalline and cast-mono production with consistent dimensional quality across high-volume supply.

Transition metals — iron, chromium, nickel, copper, and titanium — are among the most damaging impurities in solar silicon because they form deep-level traps in the silicon bandgap with large carrier capture cross-sections. When a photo-generated minority carrier encounters one of these trap states, it recombines and releases its energy as heat rather than contributing to photocurrent. The result is a reduction in minority carrier lifetime that directly lowers the cell’s short-circuit current and open-circuit voltage. Iron is particularly damaging because it diffuses rapidly through silicon at diffusion temperatures and can segregate to grain boundaries and surfaces where minority carriers are most abundant. A contamination level of iron at parts per billion in the silicon near-surface region causes measurable efficiency loss in high-efficiency PERC and TOPCon cells.

Czochralski silicon contains interstitial oxygen at concentrations determined by the crucible dissolution rate, melt convection patterns, and crystal pull rate. This oxygen is a functional component of CZ silicon whose concentration is deliberately controlled. During solar cell processing, dissolved oxygen precipitates in the silicon bulk during high-temperature thermal steps, and these oxygen precipitates getter transition metal impurities away from the electrically active surface region, improving minority carrier lifetime. This phenomenon — bulk micro-defect engineering — is most effective when the initial dissolved oxygen concentration falls within a specific target window. Crucible design and inner surface treatment are the primary variables that control dissolution rate and therefore oxygen concentration in the grown crystal.

Gettering is the redistribution of metallic impurities in silicon from regions that damage cell performance to regions where they are harmless. Phosphorus diffusion gettering — occurring automatically during the emitter diffusion step — creates a region with a large segregation coefficient for transition metals, drawing iron and other contaminants out of the silicon bulk into the heavily doped emitter layer, which is subsequently etched away. The effectiveness of this gettering depends on the initial metal concentration in the silicon. If the diffusion tube introduces additional iron onto the wafer surface during the diffusion step, it adds new contamination and partially counteracts the gettering mechanism being used to clean the silicon. High-purity quartz diffusion tubes are therefore not a quality preference — they are functionally required for effective gettering.

Devitrification — the crystallisation of amorphous fused silica into cristobalite — is accelerated in solar manufacturing environments by the frequent presence of alkali metals on wafer surfaces and in process gases. Sodium and potassium compounds from alkaline texturing baths can transfer onto wafers and subsequently onto tube walls during furnace loading. Alkali contamination on the hot quartz tube surface catalyses cristobalite formation, causing white milky deposits that generate particles and indicate structural weakening. High-throughput solar manufacturing with high tube utilisation rates accelerates devitrification. Preventive measures include strict wafer cleanliness requirements before tube loading, dedicated tube sets for different process steps to prevent cross-contamination, and visual tube inspection before each wafer load to catch early devitrification before it generates particle contamination.

Solar cell manufacturing processes thousands of wafers per hour through each diffusion tube, and the wafer boat is the direct interface between the process tube and the wafer surface. The slot geometry determines how process gas reaches the wafer surface. Straight slots allow more uniform gas access to both wafer surfaces; V-groove slots provide more positive wafer retention. The number of slots per unit length determines loading density and diffusion profile uniformity across the boat. Longer boats allow more wafers per tube load, improving throughput, but introduce more bow that must be controlled to prevent wafer contact at the slot walls. FGQuartz solar wafer boats are available in both configurations and in standard and extended lengths matched to the full range of current industrial tube furnace platforms.

The solar industry has undergone a rapid transition in wafer size, driven by cost-per-watt benefits of larger silicon area per wafer. The industry moved from M2 (156 mm) and M6 (166 mm) formats through M10 (182 mm) to G12 (210 mm) in rapid succession. Each wafer size change requires corresponding changes in quartz wafer boats, diffusion tubes, and other process hardware. A boat designed for 182 mm M10 wafers will not safely contain 210 mm G12 wafers. For cell manufacturers running multiple wafer sizes simultaneously during a format transition, managing quartz consumable inventory across multiple formats is a significant supply chain challenge. FGQuartz produces boats and tubes for all current commercial wafer formats and can produce transition-format tooling for multi-format lines.

CZ quartz crucibles for silicon crystal growth are produced by arc fusion — electrically fused from high-purity quartz sand in a rotating mould. The fused silica body has a dense, bubble-free inner layer and a more porous outer layer. The inner surface condition — which determines both the mechanical survival of the crucible in contact with the silicon melt and the oxygen dissolution rate — is controlled during both the fusion process and a subsequent surface treatment step. FGQuartz produces CZ crucibles in the standard diameter range for solar ingot pullers, with inner surface treatment options appropriate for different silicon oxygen concentration targets.

Process tubes for solar cell manufacturing are produced by CNC precision grinding from high-purity fused silica stock. The outer diameter, inner diameter, and wall thickness uniformity are monitored and documented for each production run. Tube ends are ground flat and square for proper flange mating. Inner bore surface quality is controlled through the grinding and polishing sequence to achieve the surface cleanliness required for the specific solar cell process — diffusion tubes, LPCVD tubes, and oxide passivation tubes each have different inner surface requirements reflecting the contamination sensitivity of each step.

Solar wafer boats are machined from fused silica blocks by CNC multi-axis machining. Slot cutting uses diamond-coated end mills in programmed tool paths that hold slot pitch uniformity across the full boat length. Boat bow is controlled through both raw material selection and machining strategy. Finished boats are inspected for slot dimensions, bow, and surface defect level before packaging. FGQuartz produces boats for the full range of current commercial wafer formats with both standard and custom slot counts per boat.