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Hitachi High-Technologies GLOBAL

Semiconductor Room

An etch system shapes the thin film into a desired patterns using liquid chemicals, reaction gases or ion chemical reaction. An etch system is used in manufacturing lines for semiconductors and other electronic devices.
Fig. 7-1 shows the flow of the etching process.

process flow
Fig.7-1. Flow of the etching process

There are two kinds of etch system: “wet etch system” and “dry etch system”.
An explanation of each systems are provided below.

(1) Etch System - Wet

The exposed portion is removed by using acid or alkali.

Wet Etch System Characteristics

  • Inexpensive chemical liquids (etchant)
  • Collectively process multiple wafers at the same time
  • Isotropic etching

Wet etching
Fig.7-2. Wet etching

(2) Etch System - Dry

Using high vacuum plasma

Plasma is generated from the gas and the etched material is removed by chemical reaction and accelerated ions.

Dry Etch System Characteristics

  • Excellent in microfabrication and anisotropic
  • Plasma is used in the Etch System
  • More expensive than wet etching

Dry etching

What is plasma?

Plasma is a group of charged particles that is kept almost electrically neutral as a whole. The ions with a positive charge and electrons with a negative charge are distributed equally in an ionized state. Various plasma methods of the dry etch system are shown below.

Microwave ECR etch
Fig.7-4. Microwave ECR plasma method
ECR:Electron Cyclotron Resonance

CCP etch
Fig.7-5. Capacitively Coupled Plasma (CCP) method
CCP:Capacitively Coupled Plasma

ICP etch
Fig.7-6. Inductively Coupled Plasma (ICP) method
ICP:Inductively Coupled Plasma

What is ECR?

ECR stands for Electron Cyclotron Resonance. Applying a magnetic field to a vacuum system starts a rotational motion of electrons called cyclotron motion centered at the magnetic field lines in the magnetic field. When a microwave with frequency ω matching the rotation speed is made incident, energy resonance occurs between the cyclotron motion and electric field, and the electric field energy is absorbed by the electrons. This is called electron cyclotron resonance. It effectively accelerates electrons and can apply a large amount of energy. The plasma that is generated with the energy applied in this way is called ECR plasma. The microwave is 2.45GHz, and the corresponding resonance magnetic field is 875 Gauss.

Products

Introducing the product lineup of dry etch systems