1. Dimensional accuracy
Flatness: the flatness of the surface of the base should reach a very high standard, and the flatness error should not exceed ±0.5μm in any 100mm×100mm area; For the entire base plane, the flatness error is controlled within ±1μm. This ensures that the key components of semiconductor equipment, such as the exposure head of the lithography equipment and the probe table of the chip detection equipment, can be stably installed and operated on a high-precision plane, ensure the accuracy of the optical path and circuit connection of the equipment, and avoid the displacement deviation of the components caused by the uneven plane of the base, which affects the semiconductor chip manufacturing and detection accuracy.
Straightness: The straightness of each edge of the base is crucial. In the direction of length, the straightness error shall not exceed ±1μm per 1m; The diagonal straightness error is controlled within ±1.5μm. Taking high-precision lithography machine as an example, when the table moves along the guide rail of the base, the straightness of the edge of the base directly affects the trajectory accuracy of the table. If the straightness is not up to standard, the lithography pattern will be distorted and deformed, resulting in the reduction of the chip manufacturing yield.
Parallelism: The parallelism error of the upper and lower surfaces of the base should be controlled within ±1μm. Good parallelism can ensure the stability of the overall center of gravity after the installation of the equipment, and the force of each component is uniform. In semiconductor wafer manufacturing equipment, if the upper and lower surfaces of the base are not parallel, the wafer will tilt during processing, affecting the process uniformity such as etching and coating, and thus affecting the chip performance consistency.
Second, material characteristics
Hardness: The hardness of granite base material should reach the Shore hardness HS70 or above. The high hardness can effectively resist the wear caused by frequent movement and friction of components during the operation of the equipment, ensuring that the base can maintain a high precision size after long-term use. In the chip packaging equipment, the robot arm frequently grabs and places the chip on the base, and the high hardness of the base can ensure that the surface is not easy to produce scratches and maintain the accuracy of the robot arm movement.
Density: The material density should be between 2.6-3.1 g/cm³. The appropriate density makes the base have good quality stability, which can ensure sufficient rigidity to support the equipment, and will not bring difficulties to the installation and transportation of the equipment due to excessive weight. In large semiconductor inspection equipment, stable base density helps to reduce vibration transmission during equipment operation and improve detection accuracy.
Thermal stability: linear expansion coefficient is less than 5×10⁻⁶/℃. Semiconductor equipment is very sensitive to temperature changes, and the thermal stability of the base is directly related to the accuracy of the equipment. During the lithography process, temperature fluctuations can cause the expansion or contraction of the base, resulting in a deviation in the size of the exposure pattern. The granite base with low linear expansion coefficient can control the size change in a very small range when the operating temperature of the equipment changes (generally 20-30 ° C) to ensure the lithography accuracy.
Third, surface quality
Roughness: The surface roughness Ra value on the base does not exceed 0.05μm. The ultra-smooth surface can reduce the adsorption of dust and impurities and reduce the impact on the cleanliness of the semiconductor chip manufacturing environment. In the dust-free workshop of chip manufacturing, small particles may lead to defects such as short circuit of the chip, and the smooth surface of the base helps to maintain a clean environment of the workshop and improve the chip yield.
Microscopic defects: The surface of the base is not allowed to have any visible cracks, sand holes, pores and other defects. At the microscopic level, the number of defects with a diameter greater than 1μm per square centimeter shall not exceed 3 by electron microscopy. These defects will affect the structural strength and surface flatness of the base, and then affect the stability and accuracy of the equipment.
Fourth, stability and shock resistance
Dynamic stability: In the simulated vibration environment generated by the operation of semiconductor equipment (vibration frequency range 10-1000Hz, amplitude 0.01-0.1mm), the vibration displacement of key mounting points on the base should be controlled within ±0.05μm. Taking semiconductor test equipment as an example, if the device's own vibration and the surrounding environment vibration are transmitted to the base during operation, the accuracy of the test signal may be interfered with. Good dynamic stability can ensure reliable test results.
Seismic resistance: The base must have excellent seismic performance, and can rapidly attenuate the vibration energy when it is subjected to sudden external vibration (such as seismic wave simulation vibration), and ensure that the relative position of the key components of the equipment changes within ±0.1μm. In semiconductor factories in earthquake-prone areas, earthquake-resistant bases can effectively protect expensive semiconductor equipment, reducing the risk of equipment damage and production disruption due to vibration.
5. Chemical stability
Corrosion resistance: The granite base should withstand the corrosion of common chemical agents in the semiconductor manufacturing process, such as hydrofluoric acid, aqua regia, etc. After soaking in hydrofluoric acid solution with mass fraction of 40% for 24 hours, the surface quality loss rate shall not exceed 0.01%; Soak in aqua regia (volume ratio of hydrochloric acid to nitric acid 3:1) for 12 hours, and there are no obvious traces of corrosion on the surface. The semiconductor manufacturing process involves a variety of chemical etching and cleaning processes, and the good corrosion resistance of the base can ensure that the long-term use in the chemical environment is not eroded, and the accuracy and structural integrity are maintained.
Anti-pollution: The base material has extremely low absorption of common pollutants in the semiconductor manufacturing environment, such as organic gases, metal ions, etc. When placed in an environment containing 10 PPM of organic gases (e.g., benzene, toluene) and 1ppm of metal ions (e.g., copper ions, iron ions) for 72 hours, the performance change caused by adsorption of pollutants on the base surface is negligible. This prevents contaminants from migrating from the base surface to the chip manufacturing area and affecting the chip quality.
Post time: Mar-28-2025