May 29, 2023 Semiconductors Compound Semiconductor Week (CSW) 2023- a plenary talk
Hybrid Epitaxy – A New Epi-model to Support III-V Semiconductors
This presentation described the evolution of epi-foundries from early day traditional merchant single source epitaxy services to nowadays hybrid epitaxy model with not only epi-tools integration but also the addition of regrowth and post-growth metallization steps to the epi-device structures. Since III-V semiconductors in particular have the highest level in epi-layers maturity and complexity, we focus our discussion using III-V epi-devices.


Molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MOCVD) are two most important modern epitaxy techniques that used extensively to prepare epi-wafers for III-V semiconductor electronic/optoelectronic devices. Most of the foundries were formed about 25 to 35 years ago, during the early part of the mobile phone era. The merchant epi-foundries bought either MBE or MOCVD equipment, now up to 8x6in multiwafer production configuration, from a handful of equipment manufacturers and to supply custom designed, tightly specified, epitaxial films on either GaAs or InP substrates for a variety of customers. In this type of service, epitaxial design come from the customer and the epi-foundry then converts the customer’s design into overlaying epitaxial films on one or multiple substrates using either MBE or MOCVD apparatus. As-grown epi-wafers characterization is done to ensure successful completion of the job. And wafers are delivered to customers or IC foundries for processing and fabrication. Up to date, almost all the advanced and mature III-V compound semiconductors devices are prepared on II-V epitaxial wafers.


Since every epi-technique has its limitations and no single growth machine can be configured with all the species. There are also apparent risks of cross contamination if certain species are used in the same chamber. In other words, each epitaxial tool’s configuration, various epi-layers attributes (control of thickness, composition, and doping range), and interface quality between layers, determine the epitaxial devices performance upper limits. As all the dataintensive applications in communication networks demand ever higher bandwidth and capacity, the performance requirements on all optoelectronics and RF devices are almost pushed beyond what current epi-tools can provide. In order to reach higher power, efficiency, and speed, epitaxial industry needs to expand it capabilities and relax the restrictions to support the 5G, and beyond. We discussed the following epitaxial combination possibilities, or called hybrid epitaxy, that are either established at our facilities or under proposition to be included:
• MOCVD & MBE growth combination: Dilute-nitride QW VCSEL, quantum dot QW Laser
• Epitaxy processing & re-growth: VCSEL with tunnel junction, MBE n+GaN on MOCVD GaN HEMT
• Inter-systems linkage: UHV inter-connection of As/P MBE system with As/Sb/N MBE system; MBE and MOCVD
• MBE systems with in situ sensors installed for monitoring and control
• MBE UHV linkage to processing chamber: post InP HBT epi-growth in situ metallization, pre epitaxial growth hydrogen cleaning
• Cluster tool connection to many single wafer MBE/MOCVD chambers: for 200mm & 300mm GaN/Si
In this talk, we used various device structures prepared under hybrid epitaxy to illustrate the feasibility to push device performance to higher limits without substantially increase in cost. The fundamental tools used are still MBE and MOCVD. The hardware linkage tools and various techniques used to protect and/or to clean the interface, respectively, was be discussed in the presentation.