Among numerous carbon materials, pyrolytic graphite stands out for its highly controllable layered structure and extreme anisotropy. Unlike natural graphite, pyrolytic graphite is not directly derived from minerals. Instead, it is produced through high-temperature chemical vapor deposition (CVD), where hydrocarbon gases are decomposed and deposited into layers of carbon atoms at temperatures above 2000°C, resulting in a highly oriented and extremely pure artificial graphite structure. This precisely controllable preparation method allows it to exhibit orientation-dependent characteristics in key properties such as thermal conductivity, electrical conductivity, and magnetic response, characteristics unmatched by natural graphite.

I. What is Pyrolytic Graphite?

Pyrolytic graphite is a highly oriented carbon material prepared through a high-temperature pyrolytic vapor deposition (CVD) process. It typically uses hydrocarbon gases (such as methane) to decompose and deposit carbon atoms under high-temperature (usually >2000℃) and low-pressure conditions. These atoms are then subjected to high-temperature annealing to ensure a highly ordered arrangement of the carbon layers, resulting in a graphite structure with extremely high orientation.

II. Advantages of Pyrolytic Graphite (PG) in Semiconductor Processes

1. Ion Implantation:

In the ion implantation process, PG is primarily used to manufacture high-precision gates (grids) and electrodes.

●Ion Implantation Resistance: Ion beams have extremely high energy. Traditional molybdenum (Mo) or tungsten (W) gates will undergo physical sputtering under prolonged ion bombardment. This not only causes the gate itself to thin and deform, but the sputtered metal atoms also become a serious source of metal contamination. PG exhibits extremely strong resistance to sputtering corrosion (extremely low etch rate), and its lifespan is typically several times that of metal components.

●Improved Beam Current Accuracy: Because PG is wear-resistant, the aperture size of the gate can remain stable over a long period. This ensures that the ion beam focus and angle remain stable over a long period, which is crucial for advanced processes (such as 7nm and 5nm) where the implantation angle requirements are extremely high.

●Excellent Thermal Management: Utilizing PG's extremely high in-plane thermal conductivity (approximately 4-5 times that of copper), it can rapidly dissipate the heat generated by ion bombardment along the plane, preventing localized overheating and deformation.

2. MOCVD and Epitaxy: Primarily Used for Substrate Coating

In LED manufacturing (GaN process) or silicon epitaxial processes, the most commonly used graphite substrate (Susceptor) is not the original graphite on its surface, but is usually covered with a dense layer of PG or SiC.

●Sealer: Although isostatically pressed graphite is dense, it is still microscopically porous, easily adsorbing gases and releasing particles or impurities at high temperatures. The PG coating, deposited through CVD, achieves a density close to the theoretical density, completely sealing the graphite matrix, preventing graphite particles from falling and contaminating the wafer, and also blocking the release of impurity gases from within the graphite.

●Chemical Corrosion Resistance: The MOCVD process uses large amounts of ammonia (NH3) and metal-organic sources, which are extremely corrosive. The PG layer is chemically extremely inert, effectively protecting the internal graphite substrate from corrosion.

●Blackbody Radiation and Temperature Uniformity: PG possesses excellent blackbody radiation characteristics, contributing to the accuracy of infrared thermometry. Its superior thermal conductivity also helps ensure a more uniform surface temperature of the substrate, directly determining the thickness and compositional uniformity of the epitaxial layer.

3. High-Temperature Heaters:

PBN/PG composite heaters are frequently found in PVD or CVD chambers with extremely high cleanliness requirements. These heaters do not use traditional metal wires but instead utilize PG as the heating resistor layer.

●Ultra-Clean Heating Element: Metal heating elements are prone to volatilizing metal impurities at high temperatures. Pyrolytic Graphite itself is carbon, with a purity exceeding 99.999%. Even with trace amounts of volatilization, carbon is a relatively "friendly" element in semiconductor processes (compared to gold, copper, iron, etc.), significantly reducing the risk of metal contamination.

●Ultra-Fast Response: PG heaters have a very small heat capacity, resulting in extremely fast heating and cooling rates (thermal response). This is highly advantageous for processes requiring rapid thermal cycling (RTP), significantly improving throughput.

●Customized Temperature Field: By designing the circuit path (serpentine wiring) of the PG layer, the temperature field distribution can be precisely designed to compensate for heat loss at the cavity edges, achieving extremely high wafer temperature uniformity.

4. Plasma Etch: "Low-loss" Electrodes

In dry etching, especially in highly corrosive environments involving fluorine- or chlorine-based gases.

●Replacement for Consumables: While single-crystal silicon or SiC are also used as electrodes, in certain customized processes, focus rings or electrode plates made of PG, due to their density and chemical resistance, can reduce replacement frequency and lower the Cost of Ownership (CoO).

III. Applications of Pyrolytic Graphite in Semiconductor Processes

Due to its high purity, high-temperature stability, extremely low gas permeability, excellent thermal conductivity, and controllable anisotropy, pyrolytic graphite (PG) has become an indispensable carbon-based material in semiconductor equipment. In many critical process environments (high temperature, vacuum, plasma, corrosive gases), compared to metals or ceramics, PG offers higher stability and lower contamination risk, and is therefore widely used in semiconductor wafer processing equipment and consumable components.

1. Applications in CVD/PECVD/MOCVD Equipment

①Heater Substrate and Thermal Homogenization Components

Pyrolytic Graphite(PG) can be used as a high-temperature heating plate or backplate material.

●Susceptor in MOCVD epitaxial growth reaction chamber

●Heating element support structure in high-temperature CVD furnaces

②Susceptor Coating Substrate

Many MOCVD processes use SiC-coated Pyrolytic Graphite.

Advantages of Pyrolytic Graphite:

●Low gas permeability, ensuring SiC coating stability

●No deformation at high temperatures, maintaining stable wafer temperature distribution

●Lightweight, reducing the inertia of rotating systems

Pyrolytic Graphite Coated Crucible

2. Applications in Etching Equipment

Cavity lining and reaction zone structural components

Pyrolytic Graphite exhibits excellent corrosion resistance and high-temperature stability in plasma environments, making it suitable as a reaction chamber lining material or consumable:

●RIE, ICP reaction chamber components

●Plasma baffles, reflectors

●Electrode backplates or insulating components (depending on design)

3. Applications in High-Temperature Annealing and Heat Treatment

Pyrolytic graphite is a key component material in many high-temperature heat treatment furnaces (>1000°C), including:

●Rapid Thermal Processing (RTP)

●Silicon Carbide (SiC) Epitaxial Furnaces

●High-Temperature Annealing Furnaces

●Graphite Boats and Fixtures

4. Applications in Wafer Loading/Transfer and Fixtures

PG, due to its high purity and low particulate contamination, is widely used in the following components:

●Wafer Susceptor

●Wafer Carrier/Boat

●Edge Ring

●Gas Flow Baffle

PG is particularly suitable for wafer supports in high-temperature epitaxy or chemical reaction environments.

5. Applications in Ion Implantation

Pyrolytic Graphite is used as:

●Beam stop

●Collimator

●High-energy ion absorption components

6. Potential Applications in Lithography Systems

Although less commonly used directly as optical components,Pyrolytic Graphite is also used in:

●High-absorption stray-light traps

●Thermal control structures for optical systems

Due to its excellent blackbody absorption characteristics, it can effectively suppress stray light.