High purity Isostatic Graphite

High purity isostatic graphite is a kind of special graphite material prepared by cold isostatic molding (CIP) and ultra-high temperature graphidification process (above 2800℃). Its carbon content is ≥99.9995%, key metal impurities (Fe, Ni, Cr) ≤0.3ppm, boron/phosphorus content ≤0.05ppm, ash content ≤5ppm. Meet semiconductor grade clean standard (SEMI F63). The internal structure of the material is three-dimensional isotropic, the grain size is uniform (D50=10-15μm), the density is 1.85-1.90g/cm³, and it has ultra-high thermal conductivity (120-150W/m·K) and extremely low thermal expansion coefficient (CTE≤4.0×10-6/K, 20-1000℃). It can be used in 1600℃ inert atmosphere for a long time, and the number of thermal shock cycles is more than 500 times (1200℃↔ room temperature sharp change).

Advanced production process

Raw material purification

Using ultra-low sulfur petroleum coke as the substrate, 99.9999% metal impurities were removed by plasma chemical vapor purification technology, and the ash content was reduced from the initial 300ppm to less than 5ppm with hydrochloric acid-hydrofluoric acid gradient pickling process.

Isostatic pressing molding

In the liquid medium of 200MPa ultra-high pressure for 60 minutes, the comprehensive densification of the powder particles is realized, the material density deviation is less than 0.5%, and the density gradient defect of the traditional molding process is completely eliminated.

Ultra high temperature graphitization

Continuous graphitization was carried out for 120 hours under the protection of argon gas at 2800-3200℃. The graphitization degree was ≥98%, the lattice layer spacing (d002) was stable at 0.3354-0.3360nm, and the isotropic rate (CTE anisotropy) was ≤3%.

Precision machining and surface treatment

It is processed by five-axis CNC machine tool, the dimensional accuracy is ±0.01mm, and the surface roughness Ra≤0.4μm. SiC or TaC chemical vapor deposition coatings (thickness 2-5μm) are optional to reduce the release of high temperature volatils to < 1μg/cm²·h.

Core application in semiconductor field

Thermal field system for monocrystalline silicon growth

Crucible and heater: continuous operation at 1600℃ in argon environment for 6000 hours without deformation, supporting 300mm wafer growth axial temperature gradient ≤2℃/cm, lattice defect rate caused by carbon pollution < 0.05/cm².

Thermal insulation cylinder and flow guide cylinder: porous gradient structure design (porosity 5-20% adjustable), thermal radiation efficiency control accuracy ±1.5%, help to control oxygen content of single crystal silicon < 10¹⁴ atoms/cm³.

Ion implantation and etching equipment

Bearing tray and focusing ring: surface metal contamination ≤0.1ppb, tolerance to 10¹⁶ ions/cm² dose bombardment, and 3 times longer service life than traditional materials.

Plasma electrode: electron emission stability deviation < 0.5%, suitable for 5nm process etching uniformity requirements.

Epitaxial growth of compound semiconductors

MOCVD graphite base: GaN/SiC thickness inhomogeneity < ±1.5%, surface coating reduces the defect density caused by graphite volatils to < 0.01/cm².

Quick Detail:

1. Other names: Isostatically pressed graphite, isotropic graphite.

2. Application: Single crystal furnace thermal field, EDM electrode, photovoltaic silicon wafer graphite mold.

3. Core parameters: Purity ≥99.9995%, density 1.80-1.85g/cm³.

Monocrystalline silicon growth furnace thermal field assembly.

Electrodischarge machining (EDM) electrodes.

Graphite mold for photovoltaic silicon wafer casting.

Industry top purity (5N grade), reduce process pollution.

Isotropic structure, uniform mechanical properties.

Support precision machining up to ±0.01mm tolerance.