MOCVD Synthesis and Doping of FRONT-END-OF-LINE (FEOL) and BACK-END-OF-LINE (BEOL) Compatible Two-Dimensional WSe2
Restricted (Penn State Only)
- Author:
- Kozhakhmetov, Azimkhan
- Graduate Program:
- Materials Science and Engineering (PHD)
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- September 01, 2021
- Committee Members:
- Mauricio Terrones, Outside Unit & Field Member
Saptarshi Das, Outside Field Member
Joan Redwing, Major Field Member
Joshua Robinson, Chair & Dissertation Advisor
John Mauro, Program Head/Chair - Keywords:
- two-dimensional materials
2D materials
Transition Metal Dichalcogenides
TMDCs
Chemical Vapor Deposition
CVD
Metal Organic Chemical Vapor Deposition
MOCVD
Doping
WSe2
Rhenium doping
Vanadium doping
Front-end-of-line compatible
Back-end-of-line compatible
Re-WSe2
V-WSe2 - Abstract:
- Two-dimensional (2D) materials including transition metal dichalcogenides (TMDCs) have demonstrated great practical applications across all industry sectors. Several years of non-stop research has elevated the subject to another level and have promised a next technological revolution, but to date, all the efforts are still limited to small academic laboratories. If corresponding scalable approaches that are fully compatible with the current existing industrial process lines are not addressed, commercialization might end up taking many more years or even just become a pipe dream. The work presented in this dissertation focuses on the scalable synthesis of intrinsic and extrinsic 2D WSe2 via a fully industry-compatible approach-metal-organic chemical vapor deposition (MOCVD). Chapter 1 presents the motivation of the dissertation where the emphasis is put on the potential integration of 2D TMDCs with the current existing silicon (Si) complementary metal-oxide-semiconductor (CMOS). Necessary technical aspects ranging from the experimental setup of the MOCVD reactor to various structural, morphological, compositional, and electrical characterization techniques are discussed in detail in Chapter 2. Furthermore, Chapter 3 of this dissertation focuses on low-temperature, catalyst-free MOCVD synthesis of BEOL compatible intrinsic WSe2 directly on dielectric, amorphous substrates. Scalable low-temperature synthesis has a great potential to integrate 2D materials with flexible substrates, in-situ construction of vertical and lateral van der Waals heterostructures with minimized defect densities, and deposit on substrates with high-aspect-ratio topography. Moreover, Chapters 4 and 5 provide an in-depth discussion of scalable n- and p-type doping of 2D WSe2 with rhenium and vanadium atoms, respectively at FEOL and BEOL compatible temperatures with the highest accuracy of the impurity concentrations. Strong thickness dependence of the activation energy of the dopants is observed where the dopants are not-fully ionized at monolayer films simply due to the quantum confinement effect. Chapter 6 introduces an alternative approach for successful integration where wafer-scale transfer methods that are fully automated and compatible with the 300 mm production lines are discussed. The presented transfer studies were part of my internship at imec, Leuven, Belgium where some of the information is purposely omitted due to confidentiality reasons. Lastly, a summary of the dissertation along with my outlook is shown in Chapter 7 where I cover future works and challenges that need to be addressed to close the gap between academic labs and industry.