MOTIVATION Refine MBE into a truly production-ready tool to produce - PDF document

MBE, Production Ready? Sensor-Based MBE For PHEMT Growth Dr. Yung-Chung Kao IntelliEPI , President/CEO Intelligent Epitaxy Technology, Inc. Dallas, Texas OUTLINE • Motivation and Overview • Current “Near” Production MBE Status • How to Make Current MBE Production Ready? • Sensor-Based MBE and Impacts • Conclusion • IntelliEPI: A Merchant MBE Company 1 Intelligent Epitaxy Technology, Inc. YCKao.3/1/99.C/S Outlook ‘99 MOTIVATION Refine MBE into a truly production-ready tool to produce epi-based devices at low cost • Dimensional accuracy: thickness, composition, interface • Reproducibility: run-to-run drifts elimination • Optimization: higher strain; sharper interface • Development: selective-etch PHEMT, metamorphic HEMT, InP-based HEMT, InGaP/GaAs HBTs 2 Intelligent Epitaxy Technology, Inc. YCKao.3/1/99.C/S Outlook ‘99

OVERVIEW • A production system has to be based on commercially available MBE systems • Current system hard to retrofit • Add-on instruments requirements –Non-intrusive, robust, compatible with rotation –Real-time information of system and wafer states –Simple setup/maintenance, outside growth chamber installation, low cost –Fast processing of data 3 Intelligent Epitaxy Technology, Inc. YCKao.3/1/99.C/S Outlook ‘99 Current MBE Current commercial MBE can provide: • Scalability up to multi-6in with great uniformity • Low defect density epi for designated applications • Improved source cells with thermal stability • Fully automated growth after each batch loading • Long growth campaign with large capacity Cells Limitations of current MBE: • Require dedicated calibration time/runs • Growth process is time-based dead-reckoning –No information to pass down to next wafer or next batch • Lack of early-warning for out-of-spec epi-growth • No structural growth record along growth direction 4 Intelligent Epitaxy Technology, Inc. YCKao.3/1/99.C/S Outlook ‘99

How to Make MBE Production Ready? • Real-time non-intrusive, robust sensors to monitor growth parameters: –Thickness --> pyrometry, atomic absorption –Composition --> atomic absorption –Surface roughness --> laser light scattering (LLS) –Shutter actions --> atomic absorption, reflection mass spec (REMS) –Temperature --> pyrometry, band-edge detection • Integrate sensors to commercial MBE systems • Change growth control from time-base dead reckoning to real-time sensor-controlled 5 Intelligent Epitaxy Technology, Inc. YCKao.3/1/99.C/S Outlook ‘99 Sensor-Based MBE System Sensor systems should be installed outside of the chamber through access ports to wafers 6 Intelligent Epitaxy Technology, Inc. YCKao.3/1/99.C/S Outlook ‘99

Sensor-Based MBE Case Study: Selective-Etch PHEMT Source Drain Gate AlAs n+ GaAs n+ GaAs Critical Parameters nGaAs • AlGaAs thickness n AlGaAs – No trimming for selective etch PHEMT process Undoped InGaAs Channel • Si Pulse doping/spacer n AlGaAs – Control I-V characteristics • InGaAs thickness/comp. AlAs/GaAs Superlattice – Strained active channel GaAs Buffer • Superlattice buffer improvement GaAs S.I. Substrate – Surface smoothness – Critical layers uniformity 7 Intelligent Epitaxy Technology, Inc. YCKao.3/1/99.C/S Outlook ‘99 Sensor-Based MBE Case Study: PHEMT Pyrometric & Reflection Interferometry 100   80    λ = 950 nm 60  a. u.   40  reflectivity emissivity 20 GaAs substrate AlAs layer GaAs layer 0 650 3000 film thickness (Å) 600 2500 temp. (°C) 550 2000 500 1500 450 1000 400 500 350 0 0 500 1000 1500 2000 2500 3000 time (sec) • Simultaneously monitor substrate temperature & layer thickness in real-time 8 Intelligent Epitaxy Technology, Inc. YCKao.3/1/99.C/S Outlook ‘99

Sensor-Based MBE Case Study: PHEMT Optical-based Flux Monitor (atomic absorption) 6.0 60 5.0 50 Thickness (Å) 4.0 Absorption (%) 40 gallium 3.0 30 shutter 2.0 open 20 shutter open 1.0 10 0.0 0 0 10 20 30 40 50 60 70 time (sec) • Measure atomic absorption of molecular beam flux during shutter openings and closings • Layer thickness is proportional to the integrated atomic absorption 9 Intelligent Epitaxy Technology, Inc. YCKao.3/1/99.C/S Outlook ‘99 Sensor-Based MBE Case Study: PHEMT Multi-channel Optical-based Flux Monitor InGaAs multi-layers 1 1.29 0.5 indium OFM 0 1.28 actual PL InGaAs (x=0.2) -0.5 3 1.27 2.5 EPL (eV) flux rate (Å/sec) 2 gallium 1.26 1.5 1 1.25 0.5 error bar: 0 5% uncertainty in thickness 1.24 0 100 200 300 400 500 600 50 60 70 80 90 100 110 time (sec) layer thickness (Å) • Simultaneous monitoring of indium and gallium fluxes using atomic absorption • Real-time determination of InGaAs layer thickness and composition 10 Intelligent Epitaxy Technology, Inc. YCKao.3/1/99.C/S Outlook ‘99

Sensor-Based MBE: PHEMT Surface roughness monitored by laser light scattering 40000 4.00E-11 As Ga and As REMS Sig. (a.u.) 35000 3.50E-11 30000 3.00E-11 *surface smoothens after LLS Signal (a.u.) V/III ratio increased Rough PHEMT 25000 2.50E-11 20000 2.00E-11 15000 1.50E-11 10000 1.00E-11 Smooth PHEMT 5000 5.00E-12 0 0.00E+00 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 Time (sec) • LLS record roughness information along growth direction • Real-time roughness monitoring critical for PHEMT buffer optimization by superlattice and growth conditions 11 Intelligent Epitaxy Technology, Inc. YCKao.3/1/99.C/S Outlook ‘99 Sensor-Based MBE Case Study: PHEMT Interface abruptness by Reflection Mass Spectrometry (REMS): PHEMT 1 AlGaAs Graded Residual In in AlGaAs (%) (In) AlGaAs InGaAs x New Method GaAs 0 . 5 Conventional Growth AlGaAs/InGaAs Interface 0 0 2 4 6 8 A lG a A s T h ic k n e s s (m o n o la y e r) • REMS data indicating incorporation of surface Indium into subsequent AlGaAs layer during PHEMT growth. A graded heterojunction is unfavorable in PHEMT growth 12 Intelligent Epitaxy Technology, Inc. YCKao.3/1/99.C/S Outlook ‘99

Sensor-Based MBE Case Study: PHEMT Shutter Actions by Reflection Mass Spectrometry (REMS): 1.20E-11 Ga REMS Sig. (a.u.) Ga (V926) 1.00E-11 Ga signal of 20x GaAs/AlAs superlattice 8.00E-12 6.00E-12 4.00E-12 2.00E-12 0.00E+00 1.20E-11 Ga (V927) Ga REMS Sig. 1.00E-11 Ga shutter failure recorded by REMS 8.00E-12 (a.u.) 6.00E-12 4.00E-12 2.00E-12 0.00E+00 2500 2600 2700 2800 2900 3000 3100 3200 3300 3400 Time (sec) • All shutter actions recorded so each grown layer confirmed by REMS or other composition sensors • Detection of critical layer problems:makeup, modify, abort 13 Intelligent Epitaxy Technology, Inc. YCKao.3/1/99.C/S Outlook ‘99 Sensor-Based MBE Case Study: Selective-Etch PHEMT Drain Source Gate AlAs n+ GaAs Critical Parameters n+ GaAs nGaAs � AlGaAs thickness n AlGaAs – OFM, pyrometry � Si Pulse doping/spacer Undoped InGaAs Channel – control spacer thickness & n AlGaAs composition � InGaAs thickness/comp. AlAs/GaAs Superlattice – OFM GaAs Buffer � Superlattice buffer improvement GaAs S.I. Substrate – LLS, REMS 14 Intelligent Epitaxy Technology, Inc. YCKao.3/1/99.C/S Outlook ‘99

Impact to Devices & Processing For advanced epi-devices such as selective-etch PHEMTs: • Device performance pre-determined by material growth: – Doping density, layer thickness/composition uniformity – Defect density and surface roughness – Run-to-run reproducibility • Material growth controls processing steps (recess depth and uniformity), which affects device characteristics (V TH and I DSS ). Improved growth reproducibility can: – Improve wafer-to-wafer processing repeatability – Reduce cycle time by eliminating error-prone process – Improve PHEMT uniformity will increase circuit yield – Reduce circuit tweaking so lower cost For device optimization and new device development: • Sensors provide critical growth record or “pedigree” along growth direction for analysis and evaluation 15 Intelligent Epitaxy Technology, Inc. YCKao.3/1/99.C/S Outlook ‘99 CONCLUSION • Sensor-Based MBE (SBMBE) is a commercial MBE loaded with non intrusive and robust sensors to monitor and control multi-layer epi growth. SBMBE –Increases run-to-run reproducibility, –allow growth modification or elimination of bad run early, –Provide “growth pedigree” of epi-wafers for customers process correlation and feedback • SBMBE will increase yield and decrease cost • SBMBE is a truly production MBE 16 Intelligent Epitaxy Technology, Inc. YCKao.3/1/99.C/S Outlook ‘99

IntelliEPI : A Merchant MBE Company IntelliEPI: Established in Sept. 1998 in Dallas, TX • Focus on MBE for PHEMTs, HBTs on GaAs and InP • First 4x4” commercial system to be delivered in May, 2nd 4x4” in 4Q, 99 • All systems equip with various sensor ports • Intelligent sensors facilitate low cost epi-wafers growth with high yield and minimum dedicated calibration runs • Qualification wafers available in 3Q/99; production in 4Q/99 • Production ramp up to 4 systems in three years • For more information: www.intelliepi.com • Contact: Yung-Chung Kao; kao@intelliepi.com; Tel: 972.234.0068x101; Fax: 972.234.0069 17 Intelligent Epitaxy Technology, Inc. YCKao.3/1/99.C/S Outlook ‘99