CVD Products

APPLICATIONS    MATERIALS    SYSTEMS

Overview
Genus' core business has been providing semiconductor manufacturers with systems for depositing thin films using the method of chemical vapor deposition (CVD). This process involves the introduction of materials in gaseous vapor form into an air-tight deposition chamber. The gas vapors chemically react with an underlying substrate (silicon wafer) and form or deposit a solid thin film onto the substrate. The film will have a specific composition, thickness and other material properties. These films can be either conducting (metals) or insulating (dielectrics). After being deposited, the films are patterned using masking and lithography techniques. Metal films can be deposited for circuit wiring and dielectric films serve as insulation in the circuitry of memory and logic chips. Genus' primary CVD customers have been major chip manufacturers in the memory (DRAM) segment of the semiconductor industry.

A full understanding of how thin films are used in the manufacturing process requires some basic knowledge of electric circuits and a familiarity with semiconductors in general and the terminology used for structural components. Our short primer on making semiconductors and our glossary may assist those who are new to the field.

CVD reactions consist of a vacuum chamber that is initially evacuated to a pre-defined pressure level so that the environment to which the gases are introduced is very tightly controlled, i.e., the atmospheric composition is precisely controlled. The substrate upon which the deposit is to occur is heated to a specific and very uniform temperature. Several factors -- gas composition, pressure and substrate temperature -- are the main keys for controlling the CVD reaction.
Thicknesses of today's CVD thin films cover a wide range: from a few tens of angstroms for gate dielectrics, to a few hundred angstroms for gate and local interconnects or interconnect barriers, and further on to a few thousand angstroms for dielectric isolation for interconnects. Click here for a short reference guide on micro-measurements.

The most mature film product of Genus is the tungsten silicide (WSi_x) film which is used for gates and local interconnect in DRAM devices. Other CVD processes exist for metals, e.g., tungsten (W), and for metal nitrides, e.g., tungsten nitride (WN). Source materials used for CVD depositions are called chemical precursors and are normally gases or liquids at room temperature. Typical sources for forming silicides include tungsten hexafluoride and either monosilane or dichlorolsilane. For pure metals, gases can be more unique: tungsten hexafluoride with hydrogen, or for titanium nitrides there can be metallo-organics and a nitrogen bearing compound, usually ammonia, and other exotic gases are utilized for other materials.
For common depositions of silicon based dielectric materials such as silicon dioxide or silicon nitride, silane is used as the silicon-containing gas reactant. Oxygen, nitrous oxide or ammonia is used as the oxygen- or nitrogen-containing reactant.

CVD has been used widely throughout the integrated circuit (IC) industry and other industries for decades. Early versions of CVD outside of the chip industry include depositions in the metals and ceramics fields. For example, CVD has been used for producing coatings to improve wear and abrasion resistance on tool bits, also for coatings on glass for mirrors and other applications. Within the IC industry, CVD was initially used to deposit insulating materials such as silicon dioxide and silicon nitride.

Looking forward, it is expected that CVD will continue to play a role in the fabrication of integrated circuits. The technology will be used for the foreseeable future. For WSi_x, the industry roadmap calls for migration to W and a barrier (WN) for the interface stability with silicon. Genus continues to refine and develop its CVD products for use today and in the future.