What is an Electrostatic Chuck (ESC)?

Ⅰ. ESC Product Definition

Electrostatic Chuck (ESC for short) is a device that uses electrostatic force to absorb and fix silicon wafers or other substrates. It is widely used in plasma etching (Plasma Etching), chemical vapor deposition (CVD), physical vapor deposition (PVD) and other process links in the vacuum environment of semiconductor manufacturing.

Compared with traditional mechanical fixtures, ESC can firmly fix wafers without mechanical stress and pollution, improve processing accuracy and consistency, and is one of the key equipment components of high-precision semiconductor processes.

Ⅱ. Product Types (Types of Electrostatic Chucks)

Electrostatic chucks can be divided into the following categories according to structural design, electrode materials and adsorption methods:

1. Monopolar ESC

Structure: one electrode layer + one ground plane

Features: Requires auxiliary helium (He) or nitrogen (N₂) as an insulating medium

Application: Suitable for processing high-impedance materials such as SiO₂ and Si₃N₄

2. Bipolar ESC

Structure: two electrodes, the positive and negative electrodes are embedded in the ceramic or polymer layer respectively

Features: It can work without additional media and is suitable for materials with good conductivity

Advantages: Stronger adsorption and faster response

3. Thermal Control (He Backside Cooling ESC)

Function: Combined with the backside cooling system (usually helium), the temperature is precisely controlled while fixing the wafer

Application: Widely used in plasma etching and processes where the etching depth needs to be precisely controlled

4. Ceramic ESC)Material: 

High insulation ceramic materials such as aluminum oxide (Al₂O₃), aluminum nitride (AlN), and silicon nitride (Si₃N₄) are usually used.

Features: corrosion resistance, excellent insulation performance, and high thermal conductivity.

III. Applications of ESC in semiconductor fabrication 

1. Plasma EtchingESC fixes the wafer in the reaction chamber and realizes back cooling, controlling the wafer temperature within ±1℃, thereby ensuring that the etching rate uniformity (CD Uniformity) is controlled within ±3%.

2. Chemical Vapor Deposition (CVD)ESC can achieve stable adsorption of wafers under high temperature conditions, effectively suppress thermal deformation, and improve the uniformity and adhesion of thin film deposition.

3. Physical Vapor Deposition (PVD)ESC provides contactless fixation to prevent wafer damage caused by mechanical stress, and is particularly suitable for the processing of ultra-thin wafers (<150μm).

4. Ion ImplantationThe temperature control and stable clamping capabilities of ESC prevent local damage to the wafer surface due to charge accumulation, ensuring the accuracy of implantation dose control.

5. Advanced PackagingIn chiplets and 3D IC packaging, ESC is also used in redistribution layers (RDL) and laser processing, supporting the processing of non-standard wafer sizes.

IV. Key Technical Challenges 

1. Holding Force DegradationProblem description: 

After long-term operation, due to electrode aging or ceramic surface contamination, the ESC holding force decreases, causing the wafer to shift or fall off.

Solution: Use plasma cleaning and regular surface treatment.

2. Electrostatic Discharge (ESD) Risk: 

High voltage bias may cause instantaneous discharge, damaging the wafer or equipment.

Countermeasures: Design a multi-layer electrode insulation structure and configure an ESD suppression circuit.

3. Temperature Non-Uniformity Reason: 

Uneven cooling of the back of the ESC or difference in thermal conductivity of ceramics.

Data: Once the temperature deviation exceeds ±2℃, it may cause an etching depth deviation of >±10%

Solution: High thermal conductivity ceramics (such as AlN) with high-precision He pressure control system (0–15 Torr)

4. Deposition ContaminationProblem: 

Process residues (such as CF₄, SiH₄ decomposition products) are deposited on the surface of the ESC, affecting adsorption capacity.

Countermeasure: Use plasma in-situ cleaning technology and perform routine cleaning after running 1,000 wafers.

V. Core needs and concerns of users