How to Clean a Chip Cleanroom

Semiconductor chips are extremely sensitive to dust and pollutants during the production process. Any tiny particle or contaminant in the chip cleanroom can potentially cause production issues. Therefore, the cleanroom needs to be maintained at a high level of cleanliness and requires the use of specialized cleaning methods and tools. The cleaning process for the chip cleanroom is quite different from regular daily cleaning methods. Let's discuss it today.

Principle of cleanroom cleaning

Understanding the bonding (electrical, physical, or chemical) between particles and surfaces is the first step in achieving optimal cleaning efficiency. Particles or contaminants can deposit on the surfaces inside the cleanroom through three ways: electrostatic attraction, gravity settling, and airflow guidance. Many substances become charged after friction, generating static forces that attract dust particles in the air. The mass of dust particles causes them to be affected by gravity and settle on surfaces. Cleanroom airflow can also guide dust particles onto certain surfaces.

Wet cleaning:

Using cleaning solutions to remove contaminants. In some cases, wiping may move particles but not remove them. Therefore, wet cleaning is typically used when wiping is not sufficient to overcome particle adhesion. The cleaning solution includes various chemical liquid options, and the type of chemicals required will depend on the surface material and whether the goal is disinfection or sterilization.

Dry cleaning:

Using porous or absorbent materials to polish or wipe surfaces, reducing the possibility of recontamination. Cloths and wipes should be made of durable materials that do not redeposit particles, shed fibers, or easily tear. Knitted polyester or more absorbent cotton twill wipes may be required based on the ISO class of the cleanroom.

Methods of cleanroom cleaning

1. Avoid introducing cleaning agents not specified for cleanroom use.

    It is recommended to use deionized water (DI water) to wipe all surfaces, floors, walls, and benches.

    Do not use abrasive pastes, rags, or powders in the cleanroom. Cleanroom mops are made of materials like woven polyester that limit shedding or tearing during the cleaning process.

    Use a multi-bucket mopping system that can be high-pressure sterilized, equipped with non-marking wheels, deep-drawn seamless buckets, designated cleaning water, and wastewater control devices.

    Wipe the floor with DI water and vacuum before each regular shift.

    Wet mop the floor with cleanroom cleaning agents, distilled water, and HEPA vacuum filters weekly.

    Wipe the walls with a damp cleanroom sponge and DI water, and vacuum dry once a week.

    Windows and cleanroom passageways should be cleaned daily and wiped dry with lint-free 70% IPA wipes.

2. Vacuum the ceiling daily.

    Wipe the ceiling with a wet sponge and DI water weekly, and vacuum dry afterward.

    Clean the ceiling with cleaning agents and DI water to remove deposits as needed, depending on the application.

    All daily cleaning, except for the floor, can be done during regular shift periods.

    Wipe the lampshades and light fixtures above with a wet sponge and ultrapure water weekly, and vacuum afterward.

    Replace cleanroom sticky mats as needed.

Cleanroom cleaning tools

1. Cleanroom vacuum cleaners:

    The foundation of cleanroom cleaning. They capture and remove particles from controlled environments using HEPA or ULPA filters. They enable personnel to clean flat surfaces and     hard-to-reach areas such as corners and crevices. Many products are designed for cleaning hazardous dry or wet materials and are equipped with grounding wires and spark-free         motors to prevent dust or flammable liquid explosions.

2. High-precision dry ice guns:

    In the chip cleanroom, high-precision dry ice guns are highly effective cleaning tools. If surfaces or equipment are sensitive to humidity, non-abrasive dry ice "blasting" can be performed in a nitrogen-rich environment to remove contaminants. High-precision dry ice guns use high-pressure carbon dioxide (CO2) flow to dislodge particles. Solid CO2 sublimates, leaving no chemical residues, while the contaminants are carried away by the flowing air stream.

3. Lint-free mops:

    Lint-free mops are made of materials that do not shed dust, including washed polyester fibers, microfibers, and foam sponges. These mops are available in both dry and wet forms. The main characteristic of cleanroom mops is that they do not leave any lint or residues when mopping. The mop heads, buckets, and wringers must meet the requirements of being lint-free.

Tags：Cleanroom   Chip   Clean Methods