The characteristics of excimer lamps and high-purity quartz stone 1
1. Basic Properties of High-Purity Quartz
(1) Crystal Structure and Chemical Purity
High-purity quartz still belongs to the trigonal system and trigonal trapezohedral crystal class, with its [SiO4] tetrahedral structure being highly regular. Its chemical composition is high-purity SiO2, and the mass fraction of impurity elements (such as Al, Fe, K, Na, etc.) is strictly controlled at an extremely low level. This characteristic makes it less likely to deteriorate due to impurity ionization or chemical reactions in the high-frequency discharge and strong UV radiation environment of excimer light, ensuring the long-term stability of the lamp tube.
(2) Optical Property: High Transmittance in UV Band
The UV transmittance of quartz is a core requirement for excimer light applications. High-purity quartz has a transmittance of 85% to 90% in the 100–500 nm UV band (per centimeter thickness along the optical axis), especially for the commonly used bands of excimer light such as 172 nm (Xe₂ excimer) and 222 nm (KrCl excimer), the transmission loss is extremely low. This characteristic ensures that the UV light emitted by excimer light can be transmitted efficiently, improving the luminous efficiency and irradiation effect of the light source.
(3) Thermal and Mechanical Properties
The melting point of high-purity quartz is about 1713 ∘C, and the difference in thermal expansion coefficients between the direction perpendicular to and parallel to the c-axis is relatively small. It is not easy to crack due to thermal expansion and contraction under the periodic thermal stress during the operation of excimer light. Its compressive strength (about 24,500 MPa in the direction parallel to the c-axis) and conchoidal fracture characteristics also ensure the mechanical stability of the lamp tube during processing and use.
2. Performance Requirements of Excimer Light for High-Purity Quartz
(1) Extreme Uniformity of Optical Transmittance
Excimer light needs to achieve high-energy-density light output in specific UV bands. Therefore, it is required that the transmittance of quartz in the working band of the lamp tube is not only "high" but also "uniform". If there are impurity defects or structural inhomogeneities in quartz, it will lead to increased scattering and absorption of UV light, reducing the luminous efficiency of excimer light and even shortening the lamp life. For example, trace metal impurities (such as Fe, Ti) will form UV absorption centers, directly weakening the effective irradiation intensity of excimer light.
(2) Chemical Stability and Radiation Resistance
High-frequency gas discharge (such as ionization of Xe, Kr, Cl, etc.) occurs inside the excimer light lamp tube, and strong UV radiation is generated simultaneously. High-purity quartz needs to maintain chemical inertness in this environment, neither reacting with the discharge gas nor generating color centers (such as oxygen vacancies, impurity ion excitation) due to radiation. Only high-purity quartz with excellent chemical stability can ensure the performance consistency of excimer light during long-term operation.
(3) Thermal Stability and Dimensional Accuracy
During the operation of excimer light, the local temperature of the lamp tube fluctuates greatly. The low thermal expansion coefficient and high thermal conductivity of high-purity quartz can effectively alleviate the concentration of thermal stress. In addition, the dimensional accuracy of the lamp tube (such as the uniformity of tube diameter and wall thickness) directly affects the discharge stability and light output uniformity of excimer light, which requires high-purity quartz to maintain good formability and dimensional controllability during processing.
3. Application Value of High-Purity Quartz in Excimer Light
(1) Improve the Luminous Efficiency and Lifetime of Excimer Light
High-purity quartz with high UV transmittance can maximize the output of UV light emitted by excimer light, improving the energy utilization efficiency of the light source. At the same time, its excellent chemical stability and radiation resistance can delay the problems of transmittance degradation and gas leakage of the lamp tube due to material deterioration, significantly extending the service life of excimer light. Currently, the service life of excimer light lamp tubes based on high-purity quartz can reach thousands of hours, meeting the needs of industrial continuous production.
(2) Expand the Application Boundaries of Excimer Light
In the field of semiconductor lithography, excimer light (such as ArF excimer light, 193 nm) needs to transmit UV light through high-purity quartz lenses and lamp tubes to achieve lithographic patterns with nanoscale line widths. In the field of medical disinfection, the characteristic of 222 nm excimer light that is harmless to human skin relies on the high transmittance of high-purity quartz in this band, making it applicable to disinfection scenarios where humans and machines coexist. The performance breakthrough of high-purity quartz continuously expands the application boundaries of excimer light.
4. Conclusion
The basic properties of high-purity quartz are highly compatible with the technical requirements of excimer light, forming a coordinated development pattern of "materials supporting technology and technology pushing material upgrading". As excimer light is applied in more high-end fields (such as deep UV photocatalysis, advanced display manufacturing), the performance requirements for high-purity quartz will be further enhanced. Meanwhile, the progress of quartz purification technology will also bring broader development space for excimer light. In the future, technological innovation around "high-purity quartz - excimer light" will still be one of the research hotspots in the fields of UV light sources and advanced materials.
