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Source: SEMICONDUCTOR MANUFACTURING HANDBOOK

CHAPTER 14

CHEMICAL VAPOR DEPOSITION

Edward J. McInerney
Novellus Systems, Inc.
San Jose, California

14.1 INTRODUCTION

Chemical vapor deposition (CVD) is widely used in microelectronics fabrication to deposit thin
films. It is a versatile technique used for producing both conductors and dielectrics. CVD films typ-
ically have excellent feature-filling capabilities, enabling them to fill high aspect ratio vias and
trenches found in modern integrated circuits.

14.1.1 CVD Fundamentals
In CVD, reactive gases pass over the silicon wafer. These gases adsorb onto the wafer surface and
react there, forming a film. By-products of the reaction leave the surface, as gases, and are pumped
away. The reactions are activated either by thermal energy through heating the wafer or radio fre-
quency (RF) energy through plasma (less commonly, other means such as laser light are used). In the
latter case, RF energy is used to strike plasma in the reaction chamber, creating energetic electrons
that propel the reaction forward.
A typical CVD reactor is shown schematically in Fig. 14.1. The gases enter the chamber through
an inlet. They pass over the heated wafer, then flow out of the chamber to the pumps.
14.1.2 Some History
Few CVD processes operate at atmospheric pressure due to the formation of gas-phase particles. As
a result, chemical vapor deposition wasn’t developed until the advent of reliable vacuum equipment
in the late nineteenth century. Pyroltyic carbon was deposited by Sawyer and Man in 1880 and var-
1
ious metals were deposited by hydrogen reduction of their chlorides in 1896 by Aylesworth. Modern
CVD reactors were developed in the mid-twentieth century.
It was the invention of planar processing in 1959 by Noyce and Hourni that made integrated cir-
cuit fabrication possible. This process relies on thin film deposition, followed by patterning and etch-
ing to define the metal and insulating layers that wire together the transistors. The first CVD film
used in semiconductor fabrication was Vapox, an SiO film deposited from silane and oxygen at
2
atmospheric pressure. It was used as an intermetal dielectric and passivation.
14.1.3 CVD Versus Other Methods
There are many methods of depositing thin films, several of which are used in integrated circuit fab-
rication. When aluminum was the primary conductor used in interconnects, a nice division of labor

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