Digital guide
You are here:
AMAT 0150-76757
Product Name: Dielectric Focus Ring for Plasma Etch
Product Introduction:
This component is a consumable ring placed around the perimeter of the wafer on the electrostatic chuck in plasma etch chambers. It is typically made of a dielectric material like Silicon, Silicon Carbide, or Quartz. Its primary function is to shape the plasma sheath and electric field lines at the wafer edge, ensuring that the etch rate and profile at the edge match the center of the wafer. It protects the chuck edge from sputtering and helps control the “edge roll-off” effect.
Technical Specifications:
- Material: Single-crystal Silicon, Polycrystalline Silicon, Silicon Carbide (SiC), or Fused Quartz (SiO2).
Detailed content
- Dimensions: Matches specific wafer size (200mm/300mm) with a specific inner diameter gap (typically 1-3mm) from the wafer edge.
- Thickness: 5mm to 15mm to control the sheath height.
- Dielectric Constant: Varies by material (Si ~11.7, Quartz ~3.9, SiC ~10), which affects plasma density coupling.
- Surface Finish: Ground and polished to precise tolerances.
Functional Features:
- Plasma Confinement: Acts as a physical barrier that modifies the electric field, preventing the plasma from bulging over the edge and causing non-uniform etching.
- Edge Passivation: In some processes, the ring is coated with a passivation layer to prevent etching of the ring itself, which would generate particles.
- Gettering: Silicon rings can getter oxygen and moisture, improving process stability.
- Replaceable: Designed as a consumable part with a finite lifetime based on erosion or coating buildup.
- RF Biasing: In some advanced designs, the ring can be RF-biased to actively control the ion energy at the wafer edge.
Application Scenarios:
- High-Density Plasma (HDP) Etch: Critical for etching shallow trench isolation (STI) and interlayer dielectrics.
- Deep Silicon Etch (DRIE/Bosch Process): Used to control the “footing” or “notching” at the bottom of deep trenches.
- Metal Etch: Used during aluminum or copper etching to prevent notching and maintain critical dimension (CD) uniformity.
- MEMS Fabrication: Essential for releasing structures where edge effects can cause stiction.
