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

1 Intelligent Epitaxy Technology, Inc.

YCKao.3/1/99.C/S Outlook ‘99

MBE, Production Ready?

Sensor-Based MBE For PHEMT Growth 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
• Dr. Yung-Chung Kao

IntelliEPI, President/CEO Intelligent Epitaxy Technology, Inc. Dallas, Texas

2 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

3 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

4 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

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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

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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

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YCKao.3/1/99.C/S Outlook ‘99

Sensor-Based MBE Case Study: Selective-Etch PHEMT

Critical Parameters

• AlGaAs thickness

– No trimming for selective etch PHEMT process

• Si Pulse doping/spacer

– Control I-V characteristics

• InGaAs thickness/comp.

– Strained active channel

• Superlattice buffer

improvement

– Surface smoothness – Critical layers uniformity n+ GaAs GaAs Buffer AlAs/GaAs Superlattice Undoped InGaAs Channel Source n AlGaAs Gate Drain GaAs S.I. Substrate n AlGaAs n+ GaAs

AlAs

nGaAs

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YCKao.3/1/99.C/S Outlook ‘99

Sensor-Based MBE Case Study: PHEMT

Pyrometric & Reflection Interferometry

• Simultaneously monitor substrate temperature &

layer thickness in real-time

350 400 450 500 550 600 650 500 1000 1500 2000 2500 3000 500 1000 1500 2000 2500 3000 20 40 60 80 100

reflectivity emissivity

        

GaAs substrate AlAs layer GaAs layer

λ = 950 nm

time (sec)

• temp. (°C)
• a. u.

film thickness (Å)

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YCKao.3/1/99.C/S Outlook ‘99

Sensor-Based MBE Case Study: PHEMT

Optical-based Flux Monitor (atomic absorption)

• Measure atomic absorption of molecular beam flux

during shutter openings and closings

• Layer thickness is proportional to the integrated

atomic absorption

gallium

0.0 1.0 2.0 3.0 4.0 5.0 6.0 10 20 30 40 50 60 10 20 30 40 50 60 70 Absorption (%) Thickness (Å) time (sec) shutter

• pen

shutter

• pen

10 Intelligent Epitaxy Technology, Inc.

YCKao.3/1/99.C/S Outlook ‘99

Sensor-Based MBE Case Study: PHEMT

Multi-channel Optical-based Flux Monitor

• Simultaneous monitoring of indium and gallium

fluxes using atomic absorption

• Real-time determination of InGaAs layer thickness

and composition

• 0.5

0.5 1 indium 0.5 1 1.5 2 2.5 3 100 200 300 400 500 600 flux rate (Å/sec) time (sec) gallium

InGaAs multi-layers

1.24 1.25 1.26 1.27 1.28 1.29 50 60 70 80 90 100 110 OFM actual PL InGaAs (x=0.2) EPL (eV) layer thickness (Å) error bar: 5% uncertainty in thickness

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YCKao.3/1/99.C/S Outlook ‘99

• LLS record roughness information along growth direction
• Real-time roughness monitoring critical for PHEMT buffer
• ptimization by superlattice and growth conditions

Sensor-Based MBE: PHEMT

Surface roughness monitored by laser light scattering

5000 10000 15000 20000 25000 30000 35000 40000 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Time (sec) LLS Signal (a.u.)

0.00E+00 5.00E-12 1.00E-11 1.50E-11 2.00E-11 2.50E-11 3.00E-11 3.50E-11 4.00E-11

Ga and As REMS Sig. (a.u.) As Rough PHEMT

*surface smoothens after V/III ratio increased

Smooth PHEMT

12 Intelligent Epitaxy Technology, Inc.

YCKao.3/1/99.C/S Outlook ‘99

Sensor-Based MBE Case Study: PHEMT

• REMS data indicating incorporation of surface Indium into

subsequent AlGaAs layer during PHEMT growth. A graded heterojunction is unfavorable in PHEMT growth Interface abruptness by Reflection Mass Spectrometry (REMS):

A lG a A s T h ic k n e s s (m o n o la y e r) Residual In in AlGaAs (%)

0 . 5 1 2 4 6 8 Conventional Growth New Method AlGaAs/InGaAs Interface

AlGaAs InGaAs GaAs Graded (In) AlGaAs PHEMT x

13 Intelligent Epitaxy Technology, Inc.

YCKao.3/1/99.C/S Outlook ‘99

Sensor-Based MBE Case Study: PHEMT

• All shutter actions recorded so each grown layer confirmed

by REMS or other composition sensors

• Detection of critical layer problems:makeup, modify, abort

Ga (V926)

0.00E+00 2.00E-12 4.00E-12 6.00E-12 8.00E-12 1.00E-11 1.20E-11

Ga REMS Sig. (a.u.) Ga signal of 20x GaAs/AlAs superlattice Ga (V927)

0.00E+00 2.00E-12 4.00E-12 6.00E-12 8.00E-12 1.00E-11 1.20E-11 2500 2600 2700 2800 2900 3000 3100 3200 3300 3400

Time (sec) Ga REMS Sig. (a.u.) Ga shutter failure recorded by REMS

Shutter Actions by Reflection Mass Spectrometry (REMS):

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YCKao.3/1/99.C/S Outlook ‘99

n+ GaAs GaAs Buffer AlAs/GaAs Superlattice Undoped InGaAs Channel Source n AlGaAs Gate Drain GaAs S.I. Substrate n AlGaAs n+ GaAs

AlAs

nGaAs

Sensor-Based MBE Case Study: Selective-Etch PHEMT

Critical Parameters

AlGaAs thickness

– OFM, pyrometry

Si Pulse doping/spacer

– control spacer thickness & composition

InGaAs thickness/comp.

– OFM

Superlattice buffer

improvement

– LLS, REMS

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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 (VTH and IDSS). 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

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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

17 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