In semiconductor manufacturing, the Inductively Coupled Plasma (ICP) etching process is closely related to the design, production, and machining of the machined Showerhead (gas distribution showerhead). As a core component of ICP etching equipment, the Showerhead directly affects the uniformity, precision, and process stability of etching. The following analysis is conducted from three aspects: technical principles, functional associations, and process requirements.
I. Core Requirements of the ICP Etching Process
ICP etching generates high-density, low-energy active free radicals through inductively coupled plasma to perform isotropic or anisotropic etching on the wafer surface. Its key parameters include:
1.Plasma Uniformity: It is necessary to ensure that the etching rate is evenly distributed across the wafer surface.
2.Gas Distribution Precision: The uniformity of the injection of reactive gases (such as CF₄, Cl₂, etc.) directly affects plasma density and the etching rate.
3.Process Stability: It is essential to avoid etching deviations caused by gas supply fluctuations or impurity contamination.
II. Core Functions of the Showerhead in ICP Etching
1.Uniform Gas Distribution
The Showerhead evenly sprays process gases into the reaction chamber through an array of tens of thousands to hundreds of thousands of microholes on its surface.
Association: The consistency of the microhole diameters, distribution density, and flow channel design directly influence the uniformity of gas distribution. Insufficient machining precision of the Showerhead (e.g., a hole diameter deviation > ±1μm) can lead to local gas concentration differences, resulting in uneven etching rates (e.g., variations in etching depth between the edge and center of the wafer).
2.Plasma Generation Control
In ICP etching, gases enter the reaction chamber through the Showerhead and are ionized to form plasma under the influence of an electric field.
Association: The geometric structure of the Showerhead (e.g., microhole angle, surface flatness) affects gas ionization efficiency. For example, poorly perpendicular hole walls may cause deviations in gas injection direction, reducing the uniformity of plasma density.
3.Corrosion and High-Temperature Resistance
ICP etching often uses corrosive gases (such as Cl₂, SF₆) and operates at high temperatures (200-400°C).
Association: The Showerhead must be made of corrosion-resistant materials (such as nickel-based alloys, CVD-SiC) and undergo precision machining (e.g., femtosecond laser drilling) to ensure structural stability. If the materials or machining are substandard, it may lead to corrosion or deformation of the Showerhead, contaminating the chamber environment.
III. Technical Requirements for Machining the Showerhead
1.Microhole Machining Precision
ICP etching has extremely high requirements for gas distribution uniformity (e.g., for 5nm processes, hole diameter deviations must be ≤ ±0.5μm).
Machining Challenge: It is necessary to adopt femtosecond laser cold machining or electrical discharge machining (EDM) composite processes to avoid thermal stress-induced deformation of the hole walls.
2.Surface Treatment and Cleanliness
The surface of the Showerhead must be reduced in particle shedding through precision polishing or Atomic Layer Deposition (ALD) coating techniques to avoid contaminating the wafer.
Association: ICP etching is sensitive to chamber purity, and micron-sized particles can cause etching defects (such as etching stoppage or rough sidewalls).
3.Thermal Expansion Matching
The thermal expansion coefficients of the Showerhead and the reaction chamber must be similar to prevent deformation and leakage at high temperatures.
Case Study: Anhui Boxin Micro adopts CVD-SiC material for its Showerhead, which has a thermal expansion coefficient matching that of silicon wafers, ensuring high-temperature process stability.
IV. Collaborative Optimization in Actual Production
1.Process Parameter Linkage
The radio frequency power and gas flow rate in ICP etching must be matched with the design parameters of the Showerhead (e.g., hole diameter, hole spacing). For example, the demand for high-density plasma requires a Showerhead design with smaller hole diameters and higher injection speeds.
2.Promotion of Localization and Substitution
Domestic companies (such as Anhui Boxin Micro) have achieved mass production of 5nm process Showerheads by improving Showerhead machining technology (e.g., composite machining processes), promoting the localization of core components for ICP etching equipment.
Conclusion
The high-precision requirements of the ICP etching process directly drive the technological upgrading of Showerhead machining, including microhole machining, material selection, and surface treatment. The two are closely linked through key indicators such as gas distribution uniformity, corrosion resistance, and thermal stability. In the future, as semiconductor nodes evolve to 3nm and below, the machining precision and functional coating technologies of the Showerhead will become crucial supports for breakthroughs in ICP etching processes.
AMTD provides high-precision Showerhead (showerhead/gas distribution plate/gas分配盘) services for core components. Its products mainly include Showerheads, Face plates, Blocker Plates, Top Plates, Shields, Liners, pumping rings, Edge Rings, and other core semiconductor equipment components. These products are widely used in fields such as semiconductors and display panels, with excellent performance and high market recognition.
Content Sources:
1.Chapter on ICP etching principles in Semiconductor Manufacturing Technology (by Michael Quirk).
2.Technical white papers from semiconductor equipment companies (such as Applied Materials and Anhui Boxin Micro).
3.Industry report on Non-Destructive Testing and Semiconductor Processes (SEMI standard reference).
4.International conference papers (such as IEEE IIT and SEMICON China technical forums).
