Plasma Implantation and High-Voltage Accelerators

I.Ion implantation: the semiconductor's "precision doping engineer"

Ion implantation uses a high-energy ion beam to implant dopant atoms such as boron, phosphorus, and arsenic into the semiconductor lattice, precisely controlling conductivity type, concentration, and junction depth; it is a MOSFET core technology for source/drain, well-region, and threshold-voltage adjustment.

1. Working principle and process

1. Ion generation:The ion source ionizes dopant gases (borane, phosphine) to generate B⁺、P⁺、As⁺and other ions.

   2. Mass analysis:A magnetic field selects pure ions, with purity reaching 99.99% or higher, removing impurity ions.

3. Acceleration and focusing:A high-voltage accelerator (1keV-1MeV) imparts kinetic energy to the ions, and electromagnetic lenses focus the beam.

4. Scanning implantation:The beam uniformly scans the wafer, precisely controlling dose (1E11-1E16 atoms/cm²) and depth.

5. Annealing activation:High-temperature (900–1100 °C) treatment or rapid thermal annealing (RTP) repairs lattice damage and activates dopant atoms.

2. Technical advantages and advanced applications

l Precise and controllable: Energy determines implantation depth, dose controls doping concentration, and uniformity error is

l Low-temperature process: Room-temperature operation avoids impurity redistribution by thermal diffusion and is compatible with FinFET, GAA, and other 3D structures.

l Advanced-node applications：Below 7 nm, low-energy high-dose ultra-shallow junctions (

II.High-voltage accelerator system: ion implantation's "power core"

The high-voltage accelerator provides a high-energy electric field for ion implantation and is the core subsystem that determines ion energy, beam quality, and equipment stability, with very high technical barriers.

1. Core principles and structure

l High-voltage generation: adopts electrostatic generator, voltage-multiplier rectification, high-frequency resonance, and other technologies to output 1kV-1MV DC high voltage.

l Accelerator tube: vacuum-insulated electrode array (stainless steel / molybdenum electrodes + insulating ceramic), with graded voltage division to form a uniform accelerating electric field and prevent high-voltage breakdown.

l Tandem acceleration: negative ions → high-voltage electrode → electron stripping → secondary acceleration of positive ions, energy multiplication (e.g., 1MV tandem outputs 2-3MeV).

2. Key technical specifications

l Voltage stability: fluctuation

l Insulation withstand voltage: using SF₆ insulation and composite dielectric (epoxy + ceramic), withstanding local field strength >100kV/cm, without flashover or breakdown.

l Dynamic response: millisecond-level voltage regulation, adapts to beam intensity and ion species switching, meeting mass-production stability.

3. Technical challenges and development

l High-voltage insulation: Above 1 MV, electric-field concentration on the electrode surface and dielectric aging can readily cause breakdown; electric-field simulation optimization and nanodielectric material modification are required.

l Miniaturization and localization: High-end high-voltage power supplies rely on imports; breakthroughs are being made in high-frequency high-voltage resonance, digital closed-loop control, and compact accelerating-tube technologies to advance domestic substitution.