semiconductor cluster tools selection guideSemiconductor cluster tools process semiconductor wafers for the fabrication of microelectronic components. They typically consist of multiple wafer processing stations placed around a central, automated handling unit.

 

Applications

 

Cluster tools are becoming increasingly common in semiconductor manufacturing and represent key components of fab automation operations. As chips become more complex, greater levels of automation are necessary in order to lower costs, increase productivity, and improve process reliability and product quality.

 semiconductor cluster tools selection guide

By arranging diverse processes around a single automated handler, cluster tools impart a number of specific benefits to chip manufacturing:

 

  • Short cycle times
  • Fast process development
  • Higher yield efficiency
  • Less risk of contamination

Design

 

All semiconductor cluster tools consist of three components or groups of components: a number of process/cleaning/cooling chambers, two chambers for loading and unloading, and a central robot for transferring wafers between chambers.

 

These three component groups are general and may vary. For example, the loading and unloading chambers are typically load locks, environmentally isolated wafer handlers similar to airlocks. Depending on the system's intended application, there may be as few as two or as many as eight or more process chambers, along with one or several robots.

 

A basic cluster tool design can be seen in the image of a vapor deposition system at right. This particular image classifies each component as related to handling, deposition, and processing.

 

semiconductor cluster tools selection guide   semiconductor cluster tools selection guide   semiconductor cluster tools selection guide

Component examples: a pressurized load lock, process chamber, and wafer-handling robot.

Image credits: Lesker | CVD | Brooks

 

Example System

 

As discussed below, cluster tools are designed to accomplish a specific fabrication process. Physical vapor deposition (PVD), which involves the formation of thin films on a chip by evaporation or sputtering, is a common manufacturing process which may be automated using a cluster tool.

 

An example PVD system frequently consists of two clusters attached to a single mainframe. Each cluster—the transfer cluster and buffer cluster—has its own robot and separate processing chambers.

 

The typical path of a wafer through such a system is illustrated by the diagram below. Square blocks represent chambers serviced by the buffer robot, while diamond-shaped ones indicate chambers within the transfer unit.

 

 

semiconductor cluster tools selection guide

Process Types

 

Process

Description

Image

Chemical vapor deposition

A precursor gas is heated to form thin film coatings on wafer; typically used to deposit dielectric films.

 semiconductor cluster tools selection guide

Physical vapor deposition

Uses evaporation or sputtering of atoms to form condensed film layer on a substrate.

 semiconductor cluster tools selection guide

Ion implantation

Involves a highly energized stream of ions directed at a substrate; some ions are captured by the surface; often used for doping silicon with boron, phosphorus, arsenic, or antimony.

 semiconductor cluster tools selection guide

Electrochemical deposition

Uses a liquid electrolyte and a cathode substrate to deposit film layers.

 semiconductor cluster tools selection guide

Plasma etching

Process which uses plasma to remove substrate layers for cleaning purposes; often performed before film deposition or wet processing.

 semiconductor cluster tools selection guide

Rapid thermal processing

Involves the rapid oxidation of wafers and a brief high-temperature exposure to form a silicon dioxide film.

 semiconductor cluster tools selection guide

 Table image credits: Ultramet | Aesculap | Nanotechnology Glossary | TMS | RPI | NIST

 

Standards

 

Semiconductor cluster tools may be designed with the aid of published standards and specifications. Example standards include:

 

  • SEMI E21 Mechanical interface and wafer transport standard for cluster tool module interfaces
  • SEMI E22 Transport module end effector exclusion volume standard for cluster tool module interfaces

References

 

INTECH - Automation and Integration in Semiconductor Manufacturing (pdf)

 

Image credits:

 

Oerlikon/Leybold | National Renewable Energy Laboratory