Construction of Cleanroom in Zhuhai

The construction of clean rooms in Zhuhai is commonly referred to as dust-free workshops, purification workshops, clean rooms, and other names; It refers to a specially designed room that removes pollutants such as particles, harmful air, and bacteria from the air within a certain spatial range, and controls indoor temperature, cleanliness, indoor pressure, airflow velocity and distribution, noise and vibration, lighting, and static electricity within a certain required range.

Construction of Cleanroom in ZhuhaiCommonly known as dust-free workshop, purification workshop, clean room, etc; It refers to a specially designed room that removes pollutants such as particles, harmful air, and bacteria from the air within a certain spatial range, and controls indoor temperature, cleanliness, indoor pressure, airflow velocity and distribution, noise and vibration, lighting, and static electricity within a certain required range.

Construction of Cleanroom in ZhuhaiTemperature and humidity control in the middle

The temperature and humidity of clean spaces are mainly determined according to process requirements, but under the condition of meeting process requirements, human comfort should be considered. With the increasing demand for air cleanliness, there is a trend towards stricter requirements for temperature and humidity in processes. The specific temperature requirements for the process will be listed later, but as a general principle, due to the increasing precision of processing, the requirements for temperature fluctuation range are becoming smaller and smaller. For example, in the photolithography exposure process of large-scale integrated circuit production, the difference in thermal expansion coefficient between glass and silicon wafer, which are used as mask plate materials, is increasingly required to be smaller. A silicon wafer with a diameter of 100 μ m, when the temperature rises by 1 degree, causes a linear expansion of 0.24 μ m, so a constant temperature of ± 0.1 degrees is required. At the same time, the humidity value is generally low, because sweating can contaminate the product, especially in semiconductor workshops that are afraid of sodium. The temperature in such workshops should not exceed 25 degrees, as high humidity can cause more problems. When the relative humidity exceeds 55%, condensation will form on the wall of the cooling water pipe. If it occurs in precision devices or circuits, it can cause various accidents. Rust is prone to occur at a relative humidity of 50%. In addition, when the humidity is too high, the dust adhered to the surface of the silicon wafer will be chemically adsorbed on the surface through water molecules in the air, making it difficult to remove. The higher the relative humidity, the more difficult it is to remove the adhesion. However, when the relative humidity is below 30%, due to the electrostatic force, particles are also easily adsorbed on the surface, and a large number of semiconductor devices are prone to breakdown. The optimal humidity range for silicon wafer production is 3545%.

Pressure regulation

For most clean spaces, in order to prevent external pollution from entering, it is necessary to maintain an internal pressure (static pressure) higher than the external pressure (static pressure). The maintenance of pressure difference should generally comply with the following principles:

The pressure in a clean space should be higher than that in a non clean space.

2. The pressure in spaces with high cleanliness levels should be higher than the pressure in adjacent spaces with low cleanliness levels.

The maintenance of pressure difference relies on the amount of fresh air, which should be able to compensate for the air leakage from gaps under this pressure difference. So the physical meaning of pressure difference is the resistance of air leakage (or infiltration) through various gaps in the clean room.

Regulations on airflow velocity in clean rooms

The airflow velocity to be discussed here refers to the airflow velocity in the clean room, and the airflow velocity in other clean spaces will be explained when discussing specific equipment.

For turbulent flow cleanrooms, the concept of air exchange rate is mainly used to reduce indoor pollution through the dilution effect of air, rather than directly using the concept of velocity. However, there are also requirements for indoor airflow velocity;

(1) The airflow velocity at the outlet of the air supply outlet should not be too high. Compared with a simple air-conditioned room, it is required that the velocity decay be faster and the diffusion angle be larger.

(2) The airflow velocity passing through the horizontal plane (such as the backflow velocity during side feeding) should not be too high to avoid blowing surface particles back into the airflow and causing re pollution. This velocity should generally not be too high at 0.2m/s.

For parallel flow cleanrooms, they are commonly referred to as laminar flow cleanrooms. Due to the fact that they mainly rely on the piston squeezing effect of the airflow to eliminate contaminants, the velocity on the cross-section is a very important indicator. In the past, the American 20GB standard was referenced, using 0.45m/s. However, people also understand that such high velocities require a large amount of ventilation, and in order to save energy, the feasibility of reducing wind speed is also being explored.

In China, both the "Technical Measures for Clean Air" and the "Design Specification for Cleanrooms" are stipulated in this way

Vertical parallel flow (laminar flow) clean room ≥ 0.25m/s

Horizontal parallel flow (laminar flow) clean room ≥ 0.35 m/s

noise control

The noise standards for clean rooms are generally stricter than those for protecting health, with the aim of ensuring normal operations, meeting necessary communication needs, and creating a safe and comfortable working environment. Therefore, the main indicators for measuring the noise in a clean room are:

1. The Effect of Worries

Due to noise, people feel uneasy and experience distressing emotions, which are generally divided into seven levels of annoyance: extremely quiet, very quiet, relatively quiet, slightly noisy, relatively noisy, and extremely noisy. Those who have a very noisy or extremely noisy response level are considered to have high levels of annoyance, and the percentage of people with high levels of annoyance in the total number of people is called the high annoyance rate.

2. Impact on work efficiency

This mainly depends on three aspects of reaction level, which are: concentration, accuracy of movements, and work speed

3. Interference with comprehensive communication

This is mainly divided into: clear or satisfied, slightly difficult, difficult, impossible

Use A-weighted sound level to evaluate the above three indicators. In the 1950s, it was proposed to use a spectral curve as an evaluation criterion, which means that the sound pressure level at the center frequency of each frequency band should not exceed this curve. Later, it was learned that using A-level to measure the level of noise and speech interference and annoyance is more suitable and can replace octave band sound pressure level as an evaluation criterion.

Has high demands. It is necessary to first explain the lighting method of windowless cleanrooms:

(1) General lighting

It refers to lighting that is set up to illuminate the entire illuminated area without considering special local needs.

(2) Local lighting

This refers to the lighting set up to increase the illumination of a certain location (such as a work site). But in indoor lighting, local lighting is generally not used separately.

(3) Mixed lighting

This refers to the illumination on the working surface that is composed of general illumination and local illumination. The illumination of general illumination should account for 10% and 15% of the total illumination according to the "Code for Design of Cleanrooms", but not less than 150LX. The luminous flux accepted per unit illuminated area is the lighting unit lux (LX).

The strength requirements for clean rooms in foreign countries are high, such as the requirements of several standards for clean rooms in the United States,Artificial light at 300lx has a good effect, and when the precision of the workpiece is higher, 500x is also allowed. For places that require red light illumination, such as photolithography workshops in the electronics industry, the illuminance is generally (25501x),When using natural light, higher illumination can be allowed, which is beneficial for work. Therefore, in the future, it may be promising to use both artificial and natural light for clean room lighting, which is also a trend emerging for energy conservation.

anti-static

Accidents caused by static electricity in clean rooms have occurred frequently, so the anti-static ability of clean rooms has become an indispensable aspect in evaluating their quality.

The so-called static electricity is caused by friction and other reasons that destroy the uniform neutral state of positive (+) and negative (-) charges in an object, resulting in an excess of charges and the object becoming charged. Since these charges do not flow normally, they are called static electricity.

Accidents caused by static electricity in clean rooms include the following aspects

1. Electrostatic shock caused by static electricity can lead to insecurity and fear in people, and can cause secondary injury (such as falling due to electric shock, which can then cause injury);

2. The discharge current caused by electrostatic discharge can lead to damage and misoperation of semiconductor components. For example, after shaking 50 P-MOS circuits in a plastic bag several times, 39 NAND gates were severely penetrated, with a failure rate of up to 78%. This is because semiconductor devices are very sensitive to electrostatic discharge;

3. Electromagnetic waves generated by electrostatic discharge can cause noise and misoperation in electronic instruments and devices;

4. The emission of light from electrostatic discharge can cause photosensitive damage to photographic limbs and other components;

5. The mechanical phenomenon of static electricity can cause the sieve holes to be blocked by dust, the spinning threads to become tangled, the printing depth to be uneven, and the products to be contaminated.

The main cause of static electricity accidents lies in the generation and accumulation of static electricity. The flow of airflow, friction between airflow and pipelines, air vents, filters, friction between the human body and clothing, friction between clothing, and processes such as grinding, spraying, jetting, washing, stirring, bonding, and peeling can all generate static electricity. In general, non-conductive materials (insulators) with lower electrical conductivity are less likely to flow after the charge is generated, making them more prone to electrification.

The reason why static electricity is particularly serious in clean rooms is not only because there are various process factors that generate static electricity in the clean room, but also because many materials in the clean room, such as plastic floors, walls, nylon, Dacron and other work clothes, have high electrical resistivity and are prone to static electricity and accumulation. Before the static electricity disaster in the clean room was taken seriously, these materials were widely used.