The working principle of a furnace tube cleaning machine

Wet furnace tube cleaning machines are mainly used for cleaning the inner walls of high-temperature furnace tubes (such as diffusion furnaces and oxidation furnaces) in the semiconductor and photovoltaic industries, removing residual silicon wafer debris, oxides, carbides, and other contaminants.

I. Equipment System Composition

Wet furnace tube cleaning machines mainly include the following subsystems:

Cleaning chamber: A sealed tank made of corrosion-resistant materials (such as PP, PTFE) used to hold the furnace tube and cleaning solution.

Chemical dispensing system: A liquid storage tank, precision pumps and valves, pipelines, and concentration/temperature sensors, enabling automatic mixing, delivery, and circulation of the cleaning solution.

Heating and temperature control system: A heater and PID controller maintain the cleaning solution at a set temperature (usually 50°C–80°C).

Mechanical transmission system: A motor-driven device that enables precise transfer and rotation of the furnace tube between the cleaning tank, rinsing tank, and drying position.

Rinsing and drying system: DI water spray unit, overflow tank, and nitrogen (N₂) purge system to remove residual chemicals and dry.

Waste liquid treatment system: Neutralization and collection device to meet environmental emission requirements.

Control system: PLC or computer integration to achieve process automation and parameter monitoring.

II. Core Working Principle

The equipment removes contaminants through the synergistic effects of chemical dissolution, etching, complexation, and physical scrubbing:

1. Chemical Cleaning Mechanism

HF/HNO₃ mixture: Used to remove silicon oxides (such as SiO₂) and metal contamination.

Phosphoric acid (H₃PO₄): For corrosion of high-temperature carbides (such as SiC).

Alkaline solution (such as KOH): Dissolves silicon wafer residue or organic matter.

Acidic/alkaline corrosive liquid:

Chemical reaction principle: Through the oxidation-reduction reaction between the acid and the contaminant, soluble salts are generated and washed away with the cleaning solution.

Pyrolysis and oxidation assistance

High-temperature treatment: Some equipment heats the furnace tube to above 800°C before cleaning, causing organic contaminants to pyrolyze and volatilize, while oxidizing metal impurities (such as residual aluminum or copper).

Oxygen atmosphere: Introducing O₂ or N₂O gas enhances the oxidation effect and reduces carbon residue.

2. Physical Cleaning Mechanism

High-pressure water jet/sandblasting: Through high-pressure water flow or inert particles (such as glass microspheres) spraying, peeling off loose particles and crust layers from the inner wall of the furnace tube.

Mechanical scraping: Some equipment uses rotating brush heads or spiral conveying devices to directly rub and remove stubborn attachments (such as silicon carbide deposits).

Ultrasonic cavitation: Using high-frequency vibration to generate cavitation effects, breaking down small particles and preventing them from reaggregating.

III. Key Process Parameters and Control

Chemical solution concentration: Directly affects the etching/dissolution rate and uniformity (online sensor monitoring, automatic replenishment).

Temperature: Significantly affects reaction kinetics (±1°C precision control).

Processing time: Optimized setting based on the degree of contamination and chemical liquid activity.

Fluid dynamics: Circulation/spray flow rate, pressure, and mode affect mass transfer and scrubbing efficiency.

Rinse water quality and quantity: Ensure that chemical residue is below the ppb level.

Drying gas purity and flow rate: Prevent secondary pollution and ensure drying efficiency.

IV. Application and Development

Widely used in diffusion/LPCVD furnace tube maintenance in semiconductor front-end (FEOL) manufacturing and photovoltaic cell production.

Development trends include:

Higher degree of automation and intelligence (IoT, AI optimized formula).

Development of more environmentally friendly and efficient cleaning chemicals (such as low-concentration HF, organic acids).

Combination with dry cleaning methods (such as laser, plasma) to form a hybrid process.

Strengthened online monitoring (particle counting, chemical concentration, endpoint detection).

Kexin Micro Company - Leading the Innovation of Semiconductor Cleaning Technology

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