How Is The Ultrasonic Spray Nozzle Coating The Photoresist?

Ultrasonic spray coating technology is a new technology currently playing a significant role in various industries. Larger numbers of customer now choose ultrasonic nozzle for coating.  Compared to traditional two-fluid spraying, ultrasonic spraying offers significant advantages in coating quality, material utilization, and process compatibility.

 

Our company offers free sample testing services, and an increasing number of customers are sending us samples for testing. Our equipment has received positive reviews and recognition from our customers.

 

Today, we will discuss ultrasonic photoresist spraying, a relatively common type of material spraying.

 

Photoresist is a thin film material that is sensitive to light or radiation and is primarily used for fine patterning in fields such as integrated circuits and display panels. It serves as an etch-resistant coating in the photolithography process. Its solubility changes upon exposure to light, forming the desired circuit pattern. Photoresists are categorized into positive-tone (exposed areas dissolve) and negative-tone (unexposed areas dissolve). Depending on the exposure light source, they are classified into UV, deep UV, extreme UV, and electron beam resists.

The core of ultrasonic photoresist atomization spraying technology is the use of ultrasonic vibration energy to achieve efficient and uniform atomization of the photoresist. Precise airflow control then delivers the atomized droplets to the substrate surface, forming a high-quality coating. The process can be divided into three key stages:

 

 

1. Photoresist atomization: High-frequency vibration breaks down the surface tension of the liquid.

The core component of ultrasonic spraying technology is the ultrasonic atomizing nozzle, which houses a piezoelectric ceramic vibrator. When a high-frequency electrical signal is applied to the vibrator, it generates mechanical vibrations at the same frequency, transmitting the vibrational energy to the nozzle's atomizing surface. After the photoresist is delivered to the atomizing surface through the liquid supply system, the high-frequency vibrations rapidly break down the liquid's surface tension, forming micron-sized droplets with a uniform diameter (typically 5μm-50μm).

Compared to traditional pressure atomization (which relies on high-pressure airflow to break up the liquid), ultrasonic atomization eliminates the need for high-pressure airflow interference, resulting in a more uniform droplet size distribution (within ±10%). It also avoids splashing droplets or disturbing the substrate surface due to airflow impact.

 

2. Precise Control of the Transfer Path

Our company has professional programming engineers who can independently program the atomization spray path. We can also customize different spray paths according to customer requirements. We have mature experience in manufacturing complete machines. For each device, we program it for the customer. On the screen, the customer sees the real-time spray path. In addition to path selection,we also need to adjusting the airflow velocity (to control the transfer distance, typically 5-50mm) and the relative position of the nozzle and substrate (using a robotic arm or translation stage for three-dimensional positioning), we ensure that the atomized particles reach the substrate surface vertically and evenly, avoiding uneven coating thickness caused by airflow turbulence.

3. Coating Film Formation: Low-Temperature Curing Ensures Structural Integrity

After the atomized droplets are deposited on the substrate surface, they undergo a low-temperature curing process (typically 60°C-120°C, far lower than the high-temperature curing temperatures of traditional spin coating) to form a film. Low-temperature curing not only prevents substrate deformation or material degradation caused by high temperatures, but also reduces stress accumulation within the photoresist, improving the coating's adhesion and structural integrity, laying a good foundation for subsequent photolithography processes.