FerroTec wafer heating plate: helping the semiconductor industry achieve high-precision temperature control
In the semiconductor manufacturing process, the coating and development process has a decisive influence on chip performance. The coating thickness and uniformity of the photoresist directly affect the performance of the final chip, and one of the key factors affecting the uniformity of the photoresist is the temperature control accuracy of the wafer surface. Therefore, in actual processes, wafer heating plates are generally used to perform high-precision temperature control on wafers to ensure process stability and yield.
1. Classification standards of wafer heating plates
To meet market demands, FerroTec Thermoelectrics has developed different types of wafer heating plates. First, we classify wafer heating plates into three categories according to size: 6 inches, 8 inches, and 12 inches. Secondly, according to the different internal heating methods, it can be divided into the following three types:
1. Heating film type
Adopt thin film heating technology, which has the advantages of fast response and high uniformity. Suitable for applications that require rapid heating and precise temperature control.
2. Mica heating components
Mica material is used as the insulating base, and the built-in resistance wire is used for heating. The heat source is stable and reliable, and it is suitable for occasions that require long-term stable work.
3. Armored heating wire type
Armored heating wire has excellent mechanical strength and durability and is suitable for high temperature environments.
Among the various wafer heating plates provided by FerroTec, mica type is widely used due to its excellent performance. Next, we will take the 8-inch mica heating plate as an example to give you a deeper understanding of its structural composition and performance characteristics.
2. Structure and principle of FerroTec hot plate
▲ FerroTec mica wafer heating plate (8 inches)
FerroTec mica wafer heating plate consists of several key components: heat conduction plate, mica heating plate and lower pressure plate. These components perform their respective functions and work together to ensure that the wafer is heated evenly and stably to the required temperature. Below are the functional features of each component.
1. Heat conduction plate
The heat conducting plate is in direct contact with the wafer and is responsible for transferring the heat generated by the heating plate to the wafer. Its main function is to efficiently transfer the heat generated by the mica heating plate to the wafer. In order to meet most application requirements and control costs, aluminum alloy with higher thermal conductivity is usually selected as the material of the heat conducting plate, and the surface of the heat conducting plate is hard anodized. The thickness of the oxide layer is generally above 20μm, which can not only protect the surface of the heat conducting plate to prevent scratches and bumps, but also effectively block the metal ions in the heat conducting plate to prevent the wafer from being contaminated.
2. Mica heating plate
The mica heating plate is the core heating element of the wafer heating plate, with resistance wire inside. When current passes through the resistance wire, the resistance wire generates heat, providing a stable and reliable heat source for the heating plate.
3. Lower pressure plate
The main function of the lower pressure plate is to fix the mica heating plate and prevent the heat from diffusing outward, thus playing a role of heat insulation. Since stainless steel is not easy to deform and has poor thermal conductivity, it can effectively isolate heat and ensure the temperature stability inside the heating plate. Therefore, we usually choose stainless steel as the material for the lower pressure plate.
3. Performance parameters of FerroTec hot plate
FerroTec mica wafer heating plate (8 inches) has excellent performance parameters and can fully meet the precision temperature control needs of the semiconductor wafer manufacturing industry. The maximum heating rate is 20℃/minute, which can quickly reach the required temperature in a short time. The maximum operating temperature can reach 200℃ and the extreme temperature is up to 250℃. In actual applications, the main temperatures selected by customers are 90℃, 120℃, 150℃, 180℃ and 200℃.
4. FerroTec hot plate temperature uniformity test
Temperature uniformity is a key parameter to measure the performance of wafer heating plate, which directly determines the temperature consistency of the wafer surface. In order to verify the temperature uniformity of our wafer heating plate, we selected a TC Wafer (thermocouple wafer) with 21-point temperature measurement capability and measured the temperature of 21 points simultaneously.
The test results are shown in the figure above: the temperature uniformity in these five temperature ranges meets the requirements.
The range is 0.337℃ at 90℃ and 0.394℃ at 120℃: it meets the standard of temperature uniformity of ±0.2℃ at 50～120℃
Range is 0.669°C at 150°C: Meets the standard of temperature uniformity of ±0.4°C at 120.1~150°C
The range is 0.791℃ at 180℃ and 1.009℃ at 200℃: it meets the standard of temperature uniformity of ±0.6℃ at 150.1~200℃
In summary, FerroTec's self-developed and produced mica wafer heating plate has significant advantages in temperature control accuracy and temperature uniformity, and has been successfully applied to multiple customer projects. In the future, with the rapid development of the semiconductor industry, FerroTec's thermoelectric business will further increase its investment in the research and development of temperature control equipment and launch more high-performance temperature control products and integrated solutions.
