MOCVD_minimumrequirments.pdf

Minimum Technical Requirements for Close-Coupled Showerhead Metal Organic

Chemical Vapor Deposition System specifialized in two dimensional materials heterostructure growth

The minimum technical requirements that follow are for Close-Coupled Showerhead Metal

Organic Chemical Vapor Deposition (CCS MOCVD) System for materials science applications.

The MOCVD system will be used for deposition of two dimensional (2D) materials such as graphene, boron nitride and transition metal dichalcogenide materials and their heterostructures onto semiconductor wafers such as sapphire and silicon. In addition, the MOCVD technology is used for deposition of III-V compound semiconductors such as GaN that may allow for future

2D/III-V compunds material integration. This will allow for development of new materials and may open new application opportunities.

(i) Minimal requirements for CCS MOCVD system

A Metal Organic Chemical Vapor Deposition System that has close-coupled showerhead (CCS) system.

Gas delivery into the reactor should be through a dual-plenum closed coupled showerhead so that different precursors are kept separate until injection into the growth chamber.

The precursors should enter the showerhead through two separate manifolds from the gas mixing system and maintain separation until injection into the growth chamber to prevent parasitic reactions.

The showerhead through which the gas is delivered should be maintained at a constant temperature using an external heat exchanger.

The system should accommodate three two inch wafers and allow for customized suceptors (sample holders) of any substrate size or shape fitting within the susceptor envelope.

The suceptors shoud rotate at up to 100 rpm and shoud be heated by a controllable three-zone heater.

In-situ full temperature mapping across the susceptor should be provided for real-time temperature mapping and reflectance data.

A multi-wavelength pyrometer should measure through the holes in the showerhead to provide real-time surface temperature over the susceptor.

The temperature profile across the susceptor should be controlled to provide optimum uniformity, or alternatively the user should have the capability to intentionally vary the temperature across the susceptor by tuning each of the three heater zones to enable growth at different temperatures (at different radii) within the same growth run.

The temperature data acquisition and analysis should be integrated with the process control software.

The distance between the showerhead precursor injection surface and susceptor should be dynamically adjusted from 5 mm to 25 mm during the deposition process to allow for limiting the pre-reaction time of the 2D precursors, adjusting the residence time of the growth precursors into the reaction chamber and lowering the interactions of gas phase species.

The system should have high temperature surface heater that allow growth up to

1400C which is critical for graphene growth.

The heater shoud be divided into three zones with each independently controlled to enable a highly uniform temperature across the susceptor.

For high temperature operation the susceptor should comprise of a plate susceptor

(graphite or SiC-coated graphite depending on application) together with a matching susceptor skirt. This protects the quartz susceptor support from the increased radiation during high temperature operation.

The developed process recipe using the tool should be scalable to other sized CCS systems allowing for DIRECT rercipe conversion to other reactors and to accommodate growth on larger substrates such as 300 mm tools.

(ii) Minimal requirements for gas handling and precursor delivery

The system should contain a flexible gas mixing cabinet with the capability for feeding a up to 12 metalorganic sources

The system should have up to 11 gas channels, as well as standard or double dilution channels.

The system should have gas purification capability for hydrogen, nitrogen and argon using hygrometer

The system should be capable of handling precursors with low vapor pressure.

The system should have a capability for the gas lines heating to >120oC.

(iii) Minimal requirements for system start up and performance qualification

Before the system is accepted by customer it should demonstrate (1) graphene films growth on sapphire (c-plane 0001) with demonstrated Raman G and 2D peaks and the peak intensity of the G peak is higher than the peak intensity of the D peak, which signifies defects; 2) boron nitride films growth on sapphire with Raman peak

(guaranteed) @1360-1370 cm-1; 3) tungsten disulfide growth on sapphire, The guarteed data are triangles of WS2 with lateral size from 100 nm to 1um.

(iv) Minimal requirements for computer control system

The growth process operating conditions - temperature, gas flow rates, duration, should be computer controlled.

The software should allow for monitoring and closed-loop control of the source concentration, where the gas flow through the metal organic precursor is modulated to compensate for changes in vapour pressure to ensure consistent precursor delivery to the reactor.

(v) Minimal requirements for customer support

The company should provide a training seminar at the factory before the MOCVD system is delivered to NRL (up to three participants)

The company should install the system and provide on-site training of NRL personell (up to three participants)