The thin films that are used to fabricate microelectronic devices are all formed using some kind of deposition technology where the term refers to the formation of a deposit on a substrate.
Chemical vapor deposition processes can be defined as: any process in which a thin solid film is formed on a substrate by the surface-mediated reaction of adsorbed precursors from the gas phase. The reactive nature of CVD processes distinguishes them from physical processes such as evaporation and sputtering that are employed in PVD. The term “surface-mediated” refers to the fact that the solid film is formed by a heterogeneous reaction occurring at the substrate surface. The chemical compounds that react on the surface can be either the original reagent chemicals fed to the system or short-lived intermediate species created in the high temperature gas phase. As a general rule, most CVD processes and equipment are designed so as to avoid the formation of such gas phase intermediate species, since they can self-react to produce gas phase particulates. Historically, most CVD processes were carried out using batch reactor approaches in either horizontal, hot-wall tube reactors under vacuum or in continuous reactors at atmospheric pressure. As device sizes shrank, however, the need for tighter control over the chemical processes in CVD reactions became ever more critical, leading to a greater prevalence today of single wafer/cluster tool equipment configurations in which thin films can be grown.
Chemical vapor deposition processes can be broken down into a number of discrete steps: First the precursor chemicals must be fed into the CVD reactor. Once in the reactor, precursor molecules must be transported to the substrate surface, usually through a combination of fluid transport and diffusion. Once on the surface, the precursor molecule must remain there long enough to react. After reaction occurs, the product thin film atom must remain on the surface while the by-product molecules must desorb from the substrate surface to make room for more incoming precursor molecules.
LPCVD deposition systems typically operate at pressures that range from 0.1 to 10 Torr. Reactor configurations that have been used for LPCVD thin film processes include resistance heated tubular hot-wall reactors, vertical flow batch reactors and single-wafer reactors. Throughout the latter part of the 20th Century, much LPCVD processing was performed in horizontal hot-wall tube reactors.
These reactors could process 100 or more wafers simultaneously and were very successful in depositing LPCVD silicon dioxide, silicon nitride and polysilicon thin films. LPCVD reactions for these films require temperatures that range from 425°C (silicon dioxide, low temperature oxide, LTO) to 740°C (silicon nitride) with occasional processes running at greater than 800°C (silicon dioxide, high temperature oxide, HTO).
Plasma enhanced CVD systems, like LPCVD systems, began as batch processors for loads of up to 100 wafers at a time. The key advantages sought in the use of PECVD vs. LPCVD were the ability to reduce process temperatures while maintaining or increasing deposition rates.
As device geometries grew ever smaller, limiting time-at-temperature became more important in maintaining the material properties and electrical characteristics of the components already in place on partially fabricated devices.
Atomic layer deposition is similar to LPCVD except that the chemical process is broken down into steps that isolate different adsorption and reaction steps to have self-limiting reactions.
The process employs separate pulses of precursors and reactants that pass sequentially through the process chamber. With the substrate in the process chamber and under high vacuum, an initial precursor is introduced into the chamber. The molecular character of the precursor is such that it will form a chemically-bound monolayer on the substrate surface
Physical Vapor Deposition (PVD) processes deposit thin films by using physical processes such as evaporation or sputtering. These processes vaporize material from a solid source under high temperature / high vacuum or plasma and redeposit the material on the substrate surface. Thermal evaporation and sputtering are the primary methods of PVD. Thermal evaporation vaporizes the source material by heating it in vacuum while sputtering uses a plasma to produce ion bombardment (normally argon ions) that creates a vapor from the source material. Films that can be deposited by PVD include most metals and dielectric materials.
Plasma Generators for PECVD
Our RF Power Generators deliver reliable solid state power for today’s thin film deposition applications. MKS RF generators insure consistent, repeatable power delivery in the most critical applications. The SurePower 13.56 MHz product line offers the highest power density available, up to 13 kW in a 3U full rack package. SurePower uses patented intrinsic power amplifier protection and embedded V-I sensor to achieve superior reliability and power accuracy.
Our KEINOS™ line of plasma generators are designed for pulsed duty applications in environments that experience fast impedance changes such as PECVD. The KEINOS line of generators delivers up to 13 kW of power with pulsing to 20 KHz, multiple set point pulsing, pulse shaping, and frequency tuning. We also produce a line of pulsed DC power generators for use in PECVD applications.
Reactive Gas Generators
We offer a variety of plasma-based reactive gas generators designed for both general use and for specific processes. These generators provide reliable sources of active NF3 and other fluorine-based radical species as well as reactive species derived from O2, N2, H2 and H2O. These generators find application in deposition technologies in which remote sources of plasma species are needed and in maintenance functions such as the generation of reactive species for CVD chamber cleaning.
Plasma Sources for PVD Thin Film Deposition Reactors
We offer a line of RF power and DC power generators for applications that include PVD and direct plasma PECVD applications. Product frequencies range from DC to high RF frequencies with power levels up to 100 kW.
ALD System Solutions
Our high performance P-Series Mass Flow Controllers and meters for applications in ALD processing. These are metal sealed, pressure insensitive MFC/MFMs with full scales up to 250 slm. Key for precise gas pulse production in ALD applications, they exhibit less than 750 millisecond settling time and are multi-gas, multi-range units with both analog and digital I/O and embedded Modbus and Ethernet user interfaces.
Ozone gas generators are suitable for a variety of purposes including TEOS/O3 SACVD. They incorporate field proven, high concentration, ultra-clean ozone generation technology as well as integrated ozone concentration monitor, flow control, and power distribution. Safety monitors, status indicator, and ozone destruct are available on some models.
The Paragon H* and R*evolution remote plasma sources find use in ALD as an ultra-clean source of reactive gas for wafer pre-cleaning to promote film adhesion as well as for generating reactive precursors.
The T3Bi throttle valve, an intelligent, high speed exhaust valve, provides fast downstream vacuum / pressure control for ALD applications. This throttle valve is designed for fast recovery from flow and pressure variations, a pre-requisite for vacuum control in ALD systems.
Gas Composition and Process Monitors for CVD, ALD, PVD
Our gas composition monitors are based on Fourier-transform infrared spectroscopy (FTIR) and quadrupole mass spectrometer (QMS) technologies. The MultiGas™ 2030 is an operator-friendly FTIR-based analyzer capable of ppb to ppm sensitivity for multiple gas species process monitoring applications. It has permanently stored calibration spectra, simplifying installation and calibration needs. The Vision 2000-C™ gas analyzer is an application-specific RGA designed for continuous in situ monitoring of chemical vapor deposition (CVD) and etching processes during chamber clean, passivation and deposition. The Vision 2000-C is designed to detect subtle changes in low concentration species and high mass species decay with respect to time.
Our Process Sense™ non-dispersive infrared (NDIR) analyzer for use in monitoring CVD and etch chamber cleaning processes. The Process Sense™ endpoint sensor is a small, low cost partialpressure analyzer specifically designed to determine the completion of plasma chamber cleaning of deposition chambers. Process Sense is based on near infrared absorption.
Downstream effluents in some thin film manufacturing processes can lead to yield loss and excessive equipment downtime due to clogged forelines, damaged pumps and valves, and contaminated transducers. Clogged lines simultaneously reduce flow conductance and raise particle counts. Effluent problems can also create serious safety issues. MKS has developed a series of traps and effluent management solutions and vacuum line heaters to help maintain clear piping.
Our Baratron® Capacitance Manometers are widely used for pressure in thin film deposition.
For additional information on the semiconductor deposition process as well as other semiconductor applications please download our free Semiconductor Devices and Process Technology eBook.