Achieve low-cost introduction of source gases such as CBr4 and NH3 for MBE systems with Veeco’s Low Temperature Gas Source. This unit features a large conductance tube for fast gas switching and a diffuser end plate for good growth uniformity. It is ideal for source gases that do not require thermal pre-cracking before reaching the substrate. Enhance MBE process flexibility and yield by combining this source on one mounting flange with an Atomic Hydrogen Source or a conical Dopant Source.

• Introduces gas without thermal pre-cracking
• Ammonia source for nitride growth
• Ideal injector for organometallic materials
• More than 50 in the field

The 91��Ƭ��Low Temperature Gas Source for MBE systems provides a low-cost means to introduce a source gas without thermal pre-cracking. The source features a large conductance tube for fast gas switching and a diffuser end plate for good growth uniformity. With advanced flux modeling, the end plate hole pattern is customized to the specific MBE system for optimal performance. A band heater, external to vacuum, heats the source to a temperature range (< 200°C) sufficient to prevent condensation of the gas in the tube, yet not high enough to promote cracking.

To make efficient use of the source ports on an MBE system, this source may be combined on a single mounting flange with the Atomic Hydrogen Source, or a conical Dopant Source. For these combination sources, the gas injector does not include a separate band heater, but rather is heated by the source or hydrogen-cracking filament.

Performance and Benefits

This source is an ideal gas injector for these applications:

• NH3 for GaN growth
• CBr4 for C doping
• Any other desired source gases that do not require thermal pre-cracking before reaching the substrate
• Optimized beam flux for minimizing gas load to system with good uniformity

MBE growers use a variety of active nitrogen sources for deposition of GaN and other nitride-containing materials. While highly stable N2 source gas must be activated in a plasma, NH3 is sufficiently reactive for deposition even without thermal pre-cracking. The Low Temperature Gas Source is ideal for injection of NH3 into the growth chamber. The conductance tube is heated sufficiently (<200°C) to prevent condensation without providing any cracking of the source gas. Typical substrate temperatures, in the range of 700–900°C, are sufficient to cause dissociation of the NH3 directly at the substrate.

Get optimal conditions for GaN growth of electronic and optoelectronic materials, plus unrivaled plasma stability and reproducibility, with Veeco’s Uni-Bulb RF Plasma Source. One-piece PBN gas inlet tube and plasma bulb combines with dual coaxial RF coil for excellent power coupling and heat removal. Several design options, including customized aperture plates, are available to enhance performance further.

A gas plasma is an effective tool for conversion of highly stable source gases such as N2 or H2 to more active atomic and molecular species suitable for MBE growth. The 91��Ƭ��UNI-Bulb features a patented one-piece PBN gas inlet tube and plasma bulb to eliminate gas leakage around the bulb. The resulting plasma is highly stable and reproducible, allowing many hours of run time without source re-tuning.

Interchangeable aperture plates are available in configurations of varying gas conductance for growth of GaN, mixed As/N materials, nitrogen doping, hydrogen cleaning and hydrogen assisted growth. The exit hole design minimizes ion content in the beam, while the active neutral species (atomic and molecular) are directed toward the substrate. Customized high uniformity aperture plates are available for most commercial MBE systems enabling typical uniformity of ±1%.

• Patented design with more than 225 in the field
• All-PBN, oxide-free plasma bulb construction
• Optimized exit aperture minimizes ion content and provides excellent film uniformity
• Excellent plasma stability and reproducibility
• Configurations available for growth of GaN, mixed nitrides, N doping, hydrogen cleaning and hydrogen assisted growth
• Autotuner option ensures stable growth conditions and optimizes power efficiencies

Performance and Benefits

The 91��Ƭ��UNI-Bulb RF Plasma Source is the world’s most popular for nitride growth by MBE. It provides optimal conditions for nitride growth, as proven by its record-setting results for electronic and optoelectronic applications.

These include:

• Record low threshold currents for 1.32μm GaInNAs/GaAs quantum well lasers (Tampere University of Technology, 2001)
• Production of 1.26μm InGaAsN VCSELs compatible with telecom network requirements (Cielo Communications and Sandia National Laboratories, 2001)
• Growth of AlGaN/GaN two-dimensional electron gas structures with record high mobility’s of 160,000cm2/Vsec at 77K and 51,700cm2/Vsec at 13K (University of California, Santa Barbara, 1999)
• PI-HEMTs from AlGaN/GaN show small signal RF performance and DC breakdowns as a function of gate length that are as good as the best transistors made by MOVPE (Cornell University, 1999)
• Reported GaN growth rates as high as 2.6μm/hr. (University of Tokyo, 1999). Most commonly, the source is used for GaN growth rates in the range of 0.8-1.0μm/hr
• Mass spectroscopy studies indicate that the beam flux is rich in metastable nitrogen molecules with very low ion content. The metastable molecules exhibit a high incorporation rate in GaN growth and stabilize the growth rate at high substrate temperatures (approx. 700-750°C.) (West Virginia University, 1999)

For high-performance UHV delivery of gases requiring thermal cracking before arriving at the substrate in MBE applications, Veeco’s Gas Crackers offer unique features like a customized exit cone and endplate to optimize flux uniformity. These gas crackers feature a conventional single filament source heater for radiative heating of the tantalum or PBN cracking tube. Multiple design options to enhance process efficiency are also available.

• For UHV delivery of gases requiring thermal cracking
• Ta or PBN gas conductance tube
• Excellent uniformity with customized exit cone and endplate
• More than 40 in the field

Gas crackers are used with source gases that must be activated by thermal cracking before arriving at the substrate. Gas crackers feature a conventional single filament source heater for radiative heating of the tantalum or PBN cracking tube. An internal baffle may be used to enhance cracking efficiency. Sources are available with multiple gas inlets, as well as up to three separate conductance tubes.

Veeco’s retractable sources address fundamental limitations of MBE, including source capacity, source removal for maintenance and system uptime. The retractable source allows an individual source to be withdrawn and isolated from the growth environment with the source gate valve and then removed without venting the entire chamber. The source can then be easily refilled with the same material or a new material before being remounted at standard positions to the growth module, allowing growths to continue with minimal interruption. This saves the user from re-qualifying new source to substrate distances and multiple weeks of downtime by avoiding the process of an entire system vent and bake. In addition, the differential pumping option provides a marked improvement in base pressure around the source to reduce contamination of the source material and provide longer lifetimes for sources in corrosive and oxidizing environments. Veeco’s retractable source is the leading solution for material flexibility, system productivity and enhances our leadership with the patented SUMO source technology.

• Provides virtually uninterrupted system operation
• Reduces refill and maintenance times
• Improves reliability and bellows-free design
• Preserves purity of source material via differential pumping
• Available exclusively on 91��Ƭ��MBE systems

Get rapid, reliable high temperature thermal cracking of H2 into Atomic H for molecular beam epitaxy (MBE) from the 91��Ƭ��Atom-H Source. This all-refractory metal source is designed for operation at 1800-2200°C and is compatible with most preparation and growth chambers. Besides high-temperature MBE, Atomic H has been shown to be ideal for low temperature in-situ substrate cleaning and for structure overgrowth preparation.

• Specialized high-temperature thermal cracker for cracking H2 into atomic H—useful in substrate cleaning and during MBE growth
• Tungsten heater filament positioned inside the gas conductance tube for operation at 1800-2200°C
• Available on 2.75″/70mm water-cooled Cf mounting flange for compatibility with most preparation and growth chambers
• Well-suited for low temperature in-situ substrate cleaning and preparing structures for overgrowth
• Applications include promotion of two-dimensional GaAs growth, GaN growth rate enhancement and selective epitaxy

Cracking Efficiency of the 91��Ƭ��Atomic Hydrogen Source Atomic hydrogen has been used in solid source MBE for a variety of applications relating to epitaxy and substrate cleaning. Many of the reported results have been achieved using thermally cracked H2 generated by home-built cracker sources.

Get a cost-effective solution that’s ideal for your high-volume, high-value MBE process needs with reliable 91��Ƭ��Single Filament Sources. They feature dependable band thermocouples and single heater filaments for 750-1200°C operation. Three system configurations, and many crucible sizes, are available. All offer stable and consistent fluxes of high vapor pressure materials.

• Patented design with more than 1125 in the field
• Single filament “cold-lip” and “hot-lip” designs
• Compatible with virtually all power supplies
• Wide range of sizes available
• Excellent performance and value

91��Ƭ��MBE Single Filament Sources are available in three versions:

• Standard Filament Source. The Standard Filament Source is a general purpose source featuring a single uniformly distributed heater filament. All designs include a band thermocouple with a large crucible contact area. Although source heating is uniform, the source is slightly cooler at the tip due to radiative heat loss at the crucible orifice, especially for the larger capacity sources. For evaporation of aluminum, it may be desirable to enhance this “cold-lip” effect as discussed below.
• Modified Filament Source. This source features a patented “modified” single filament design. “Hot-lip” heating is achieved with one filament which uniformly heats the bottom portion of the crucible but includes extra filament density at the top to compensate for radiative heat loss at the orifice. This design is particularly effective with smaller capacity crucibles.
• Cold-Lip Source for Aluminum. Molten aluminum wets PBN, often resulting in charge creep and overflow in conventional sources. Factors contributing to aluminum overflow include source installation angle, amount of aluminum loaded, and source ramp rates. Users observing persistent creep and overflow problems with standard sources may require a special single filament source with a shorter filament that produces an exaggerated “cold lip.” The Cold-Lip Source for Aluminum promotes freezing of aluminum at the crucible lip before it can creep out and damage the source.

For demanding applications, or when large source capacities are required, Dual Filament or SUMO Sources are recommended.

Performance and Benefits

Single Filament Sources offer good performance and value for general purpose applications. The Standard Filament Source provides better accuracy and stability due to the band-style thermocouple leading to increased thermal stability. The hot-lip heating in a Modified Filament Source reduces gallium- and indium-related oval defects. It also improves the stability and reproducibility of evaporation of other materials by preventing condensation in the crucible.

Attain large capacity, excellent flux uniformity, negligible shutter flux transients, and minimal depletion effects with Veeco’s Downward-Looking SUMO® Source for MBE. It combines a dual filament source with an asymmetric SUMO crucible featuring a narrow offset orifice and tapered exit cone with hot-lip heating. Result: excellent material quality, low defect counts, and good thickness uniformity. NOTE: This source is not for use with aluminum.

• Patented design with more than 75 in the field
• Accommodates molten charge materials in downward-looking ports
• Excellent flux stability and uniformity
• PBN crucible construction optimizes material quality

The 91��Ƭ��Downward-Looking SUMO Source is a dual filament source with an asymmetric SUMO crucible, uniquely designed to accommodate a molten charge in a downward-facing source port. The narrow orifice is offset to contain the melt, while a tapered exit cone provides excellent flux uniformity. This novel crucible shape is available only with Veeco’s patented SUMO technology.

Hot-lip heating in the exit cone region prevents charge recondensation and minimizes Group III-related oval defects. This design and position of the base heater filament is tailored to the non-uniform distribution of charge material in the crucible for optimal flux stability. This source is not for use with aluminum.

Performance and Benefits

Downward-looking source ports enable users to expand the total number of Group III sources available on an MBE system with downward looking source ports. Redundant sources increase the total charge capacity for the most commonly used materials, and allow for rapid switching between different flux settings by using separate sources for each desired flux. The Downward-Looking SUMO Source also offers increased charge capacity for molten source materials in shallow upward-facing ports. For example, a 175g Downward-Looking SUMO Source in the shallow upward-looking port on a GEN III System has a capacity of 425g of gallium while a standard 400g SUMO would have a capacity of 49g in the same port.

The exit cone design assures flux uniformities comparable to those achieved with a system’s original Group III sources. Standard 1% uniformity has been demonstrated across a 2” wafer in a MOD GEN II System.

Get the optimal thermal profile for different materials and situations with the 91��Ƭ��Dual Filament Source. This source is designed for growing high-quality Ga- and In-containing materials, while preventing charge material recondensation and significantly reducing defects. Dual Filament Sources are available for use with both SUMO and conventional crucibles (including Group III production crucibles).

• Patented design with more than 725 in the field
• Proven effective method of reducing morphological defects
• Produces a more hydrodynamically stable flux
• Responsive temperature ramping

The Dual Filament Source uses two independent heaters to control the temperature variation along the length of the crucible. The bottom filament is required for thorough source and crucible outgassing, and to achieve higher growth rates.

The Dual Filament Source is used in “cold-lip” mode with aluminum only. The lip region is deliberately kept cooler than the rest of the crucible to prevent aluminum creep. Aluminum flux uniformity may be optimized by adjusting the crucible temperature gradient.

The Dual Filament Source for MBE is available in a range of crucible sizes, including direct replacements for most commercial MBE systems. A standard Dual Filament Source with conical crucible may be preferable in cases where a smaller charge capacity is acceptable and fast ramping of source temperature is critical.

Performance and Benefits

Data from dozens of facilities have shown that the Dual Filament Source significantly lowers oval defect densities. Defect densities are reduced by a factor of 5-10 when a “cold-lip” Single Filament Source is replaced with a “hot-lip” Dual Filament Source.

When used for gallium and indium evaporation, hot-lip sources reduce the formation of oval defects at the growth surface, leading to improved device performance. The most widely accepted theory about these source-related morphological defects is that they are caused by “spitting” from the melt, which occurs when droplets of condensation form at the crucible orifice and then roll back into the hot melt.1

The figure provided illustrates how hot-lip heating prevents condensation and thereby eliminates spitting. Impurities in the melt, such as gallium oxide, may also cause oval defects. In this case, eliminating condensation is also beneficial since the droplets may otherwise gather impurities from the surrounding environment. When used for aluminum, the Dual Filament Source allows sufficient heating at the orifice to provide good flux uniformity while providing a “cold lip” to prevent aluminum creep that can damage the source heat shielding and heater filaments. The Dual Filament Source, operated in “cold-lip” mode, provides enhanced aluminum source reliability, together with great performance.

1. D.G. Schlom, et al, J.Vac. Sci. Technol. B 7, 296 (1989).

Achieve excellent flux uniformity, negligible shutter flux transients, and minimized long-term depletion effects for MBE processes from Veeco’s Hot Lip SUMO® Source with large-capacity crucible. The source is designed for enhanced efficiency and reduced thermal load and provides enhanced material quality, low defect counts, and good thickness uniformity across the substrate.

• Patented design with more than 1150 in the field
• Increased capacity
• Extremely stable operation
• Low background impurities
• Excellent flux uniformity
• PBN crucible construction optimizes material quality

The SUMO Source for MBE is the optimal source technology for Group III evaporation. The SUMO design features a dual filament heater tailored to a uniquely shaped crucible. With gallium and indium, the source is operated in hot-lipped mode to eliminate material recondensation at the crucible orifice, and thereby reduces oval defects. A heat-shielding cap enhances the source’s efficiency and minimizes the thermal load on the system. The SUMO Source offers excellent flux stability and uniformity along with a significantly increased charge capacity.

The unique patented crucible features:

• A cylindrical reservoir for large charge capacity and minimized long-term depletion effects
• A small tapered orifice for optimal flux distribution and negligible shutter flux transients
• An exit cone for excellent flux uniformity with minimal wasted material
• PBN construction for optimal material quality

SUMO Sources are available optimized for any MBE system. For some systems, the SUMO crucible features an asymmetric orifice and offset exit cone to redirect the beam flux for enhanced thickness uniformity across the rotated substrate. Due to the wider exit cone, the asymmetric SUMO does not use a separate heat-shielding cap at the crucible lip.

Performance and Benefits

SUMO Sources provide the largest available Group III charge capacity without sacrificing material quality or source performance. Facilities worldwide have demonstrated excellent material quality with good thickness uniformity across the substrate.

Benefits include:

• Large charge capacity. Compared to the original Group III sources from other vendors, the Ga or In charge capacity may be doubled. The SUMO Source size refers to the actual amount of source material that can be loaded is dependent on system geometry and source port location. For example, a 4500g SUMO Source may be loaded with either 4500g of gallium or 5500g of indium.
• Good uniformity. SUMO Sources are designed to meet or exceed the thickness uniformity (±1%) achieved in most MBE systems with the originally recommended sources.
• Long-term flux stability. With its unique shape, the SUMO crucible minimizes the long-term depletion effects commonly seen with conical crucibles. The SUMO Source presents a constant melt surface for more consistent and reproducible day-to-day operation. A constant beam flux is maintained with smaller and less frequent temperature changes.
• Low defect densities. Hot-lip heating with a dual filament source ensures that the crucible orifice is sufficiently warmer than the melt temperature to prevent gallium and indium droplet formation. Measured defect densities for material grown with a SUMO-Reduced shutter-related flux transients. The melt surface, recessed behind the small orifice of the SUMO crucible, is shielded from most reflected radiation. Heat reflected back from closed shutters is diffused by the PBN crucible without causing the shutter flux transients commonly seen with conventional open crucibles.
• Excellent material quality. PBN crucible construction and small crucible orifice, coupled with efficient dual filament heating, reduces the thermal load on the surrounding system and leads to lower background impurities in the grown layers.

Achieve precise MBE operation at medium temperatures and partial pressures, plus increased campaign time and lower repair costs, with 91��Ƭ��oxygen-resistant, extended life sources. Options include substrate heaters for high oxygen partial pressures and the SUMO crucible for optimal flux distribution and minimized depletion effects.

• Extended life for oxygen environments
• SUMO crucible available with optimal flux distribution and minimized depletion effects
• Oxygen partial pressures up to 5milliTorr
• Temperatures up to 1150°C
• More than 20 in the field

Oxide material research has increased considerably over the years because of its importance in the IC industry and because of the wide variety of electronic and optical properties made possible using these materials.

Due to the corrosive nature of oxygen, performing thin-film research in an oxygen environment often presents equipment challenges. For example, it is common to thermally evaporate materials in an oxygen environment of 10-5 Torr or higher while maintaining the substrate temperature at 800°C. The high oxygen partial pressure and temperature greatly reduces the lifetime of the heating elements in sources and substrate heaters. As a result, the equipment uptime is compromised, leading to shorter campaign lengths and high repair costs.

Using special oxygen-resistant materials as opposed to traditional materials such as molybdenum and tantalum, it is now possible to operate Veeco’s innovative and proven sources and substrate heaters in high oxygen partial pressure environments. Oxygen-resistant sources are currently available from 91��Ƭ��for temperatures up to 1150°C with oxygen partial pressures as high as 5milliTorr. Substrate heaters are also available for temperatures up to 800°C and oxygen partial pressures of 5milliTorr.