Precision silicon carbide ceramic components on photolithography equipment.

The characteristics and requirements of precision ceramic structural components for semiconductor equipment

The key equipment for integrated circuit manufacturing requires that component materials possess characteristics such as high purity, high density, high strength, high elastic modulus, high thermal conductivity, and low thermal expansion coefficient. Furthermore, the structural components must have extremely high dimensional accuracy and structural complexity to ensure that the equipment can achieve ultra-precision motion and control.

Taking the work stage in a lithography machine as an example, the main function of the work stage is to support the silicon wafer and the mask and complete the exposure process, and its performance directly affects the yield and resolution. The work stage is required to achieve high-speed, smooth long strokes and six degrees of freedom for nanometer-level ultra-precision motion. For a lithography machine with a resolution of 100 nm, overlay accuracy of 33 nm, and line width of 10 nm, the positioning accuracy of the work stage must reach 10 nm, while the simultaneous stepping and scanning speeds of the mask to the silicon wafer should reach 150 nm/s and 120 nm/s, respectively, with the mask scanning speed approaching 500 nm/s. Additionally, the work stage must possess very high motion precision and stability.

Therefore, the precision structural components of the workpiece platform must meet the following requirements:

(1) Lightweight design: To reduce the moment of inertia, lessen the load on the motor, and improve motion efficiency, positioning accuracy, and stability, structural components generally adopt a lightweight design, achieving a weight reduction rate of 60% to 80%, with a maximum of up to 90%;

(2) High geometric precision: To achieve high precision in motion and positioning, structural components are required to possess extremely high geometric precision, with flatness, parallelism, and perpendicularity demands of less than 1 μm, and overall geometric precision requirements of less than 5 μm;

(3) High dimensional stability: To ensure high precision in motion and positioning, structural components must exhibit outstanding dimensional stability, resisting strain, with a high thermal conductivity and low thermal expansion coefficient to minimize significant dimensional deformation;

(4) Clean and contamination-free: Structural components are required to have an extremely low coefficient of friction, resulting in minimal kinetic energy loss during motion, and should be free from the contamination of grinding particles.

The application of silicon Carbide Ceramics in lithography machines

Silicon carbide is a type of structurally superior ceramic material, characterized by high strength, high hardness, high elastic modulus, high specific stiffness, high thermal conductivity, low thermal expansion coefficient, and excellent chemical stability. It is widely applied in fields such as petrochemicals, machinery manufacturing, nuclear industry, and microelectronics. Silicon carbide exhibits a very high elastic modulus, thermal conductivity, and moderate thermal expansion coefficient, along with exceptional polishability that allows it to be machined into high-quality mirror surfaces, while being resistant to deformation and thermal strain. Through specialized lightweight structural design, a high degree of weight reduction for structural components can be achieved, making it widely used in the field of integrated circuit manufacturing equipment.

Silicon carbide ceramics exhibit excellent mechanical properties at room temperature, outstanding high-temperature stability, as well as good specific stiffness and optical processing capabilities. They are particularly suitable for the preparation of precision ceramic structural components for integrated circuit equipment, such as SiC ceramic worktables, guide rails, mirrors, ceramic suction cups, arms, cooling plates, and suction devices used in lithography machines.

Technical challenges of silicon carbide structural components for semiconductor equipment

Core equipment for integrated circuits with precision ceramic structural parts typically exhibit characteristics of being "large, thick, hollow, thin, light, and precise." However, due to silicon carbide being a covalent compound with strong Si-C bonds, it possesses extremely high hardness and significant brittleness, making precision processing challenging. Additionally, silicon carbide has a high melting point, complicating the achievement of dense, near-net-shape sintering. During the fabrication of silicon carbide structural parts, there are several technical difficulties and challenges:

(1) How to achieve hollow closed-pore structures to meet high lightweight goals. For metal structural parts with hollow closed-pore structures, brazing and diffusion welding processes are usually employed; but for those with complex and immature characteristics, noticeable connection interfaces can form, leading to significant differences in composition and performance between the connection layer and substrate.

(2) How to achieve high geometric accuracy for silicon carbide structural parts to enable precise motion and positioning. The hardness of silicon carbide is second only to diamond, resulting in low processing efficiency and high costs for silicon carbide structural parts, making the realization of high geometric accuracy a technical challenge, especially when preparing samples with large sizes, ultra-thin features, and complex structures, particularly those with hollow closed-pore structures.

(3) How to reduce or avoid residual stress in the shaping, drying, sintering, and subsequent precision processing of silicon carbide products to improve product quality and yield. During drying and sintering of silicon carbide green bodies, uneven shrinkage can easily occur due to moisture removal and organic material loss, leading to defects such as cracking and deformation, and introducing residual stress within the body. Moreover, in the subsequent precision processing after sintering, this may trigger crack propagation within the products, resulting in defects such as cracks, thereby lowering the product yield. The fabrication of large-sized, complex, and irregular hollow structure precision silicon carbide structural parts is highly challenging.

Currently, the market for silicon carbide ceramics for integrated circuit manufacturing equipment is mainly dominated by foreign companies such as Japan's Kyocera and America's CoorsTek, while domestic companies include China Building Material Academy and Ningbo Vulcan. China's research and development in the fabrication technology and application promotion of precision silicon carbide structural parts for integrated circuit equipment started relatively late and still lags behind internationally leading companies.