BandiT Presentation with AVI FEB 3 04

kSA BandiT: Band-edge Thermometry: 

kSA BandiT: Band-edge Thermometry

Band-edge Thermometry Principles: 

Band-edge Thermometry Principles Semiconductors: transparent for hν < Eg, opaque for hν >= Eg Semiconductors: as substrate temperature increases, Eg ↓ and λg ↑ Look at diffusely scattered light component– not the specular component. Specularly reflected (front surface) light does not interact with the wafer.

Band-edge Thermometry vs. Pyrometers: 

Pyrometers: Typically inaccurate or no measurement below 400-450oC Potential interference from stray IR (esp. at low Ts), internal reflections (heterojunctions), coated view ports Absolute temperature calibration from machine to machine is difficult Eg thermometers: Need good light collection & detection system Need good normalization & fitting software Absorbing over layers limit thickness for temperature measurement Band-edge Thermometry vs. Pyrometers

kSA BandiT vs. Competitor Instruments: 

State-of-the-art solid state spectrometer - 1000x more sensitivity and no moving parts (longer lifetime, no need for constant recalibration) Excellent S/N without a chopper Efficient collection optics Powerful software and full software development team Operates in either transmission or reflection mode Single USB connection to laptop computer Full technical service and support kSA BandiT vs. Competitor Instruments

kSA BandiT Product Specifications: 

kSA BandiT Product Specifications BandiT System Schematic

BandiT Light Source: 

BandiT Light Source 150W halogen lamp with gold coated parabolic reflector. Light source collimating optics. Real-time output power control via BandiT software. Internal feedback control for stable intensity and spectral output. NOTE: above ~300 oC can use heater as light source kSA BandiT Product Specs. Cont’d

BandiT Detector: 

BandiT Detector 2-inch collection optics focusing to 400 um fiber. Single-axis gimble mount for radial scanning between inner/outer platen rings Dual fiber with visible laser for easy alignment. kSA BandiT Product Specs. Cont’d

kSA BandiT Product Specs. Cont’d: 

kSA BandiT Product Specs. Cont’d

kSA BandiT Software: 

kSA BandiT Software Full hardware control and real-time feedback of lamp and spectrometer Powerful, flexible fitting algorithms Ability to store full, partial, or no spectra and temperature data Full analog and digital I/O capability USB interface, runs from a laptop

kSA BandiT Performance Specifications: 

kSA BandiT Performance Specifications [1] B-VIS model [2] B-NIR model

BandiT Stability Data – GaAs @ 300C: 

BandiT Stability Data – GaAs @ 300C

kSA BandiT Performance Specs (cont’d): 

kSA BandiT Performance Specs (cont’d) Noise from rotation ~1-2oC for all size wafers Pyrometer noise typically much worse for ¼ X 3” pieces No interference from: hot sources highly doped epi (2um of GaAs:C, p = 6.5e19/cm3) high-on-low Eg growth (AlGaAs/GaAs) Low-on-high Eg growth: InGaAs/InP InGaAs strong IR absorber Clean measurement thru ~ 1.2 um of epi (using heater only)

kSA BandiT Calibration File Generation: 

kSA BandiT Calibration File Generation material thickness dopant level Calibration depends on:

BandiT, TC, and Pyro Measurement: 

BandiT, TC, and Pyro Measurement Pyro reads high at low temps because substrate is transparent GaAs Oxide Desorption

Interference Oscillations: 

Interference Oscillations Oscillations in temperature

Low Temp GaAs Growth: 

Low Temp GaAs Growth Temp increase due to As absorption TC does not see temp rise due to As Absorption

BandiT Measurement During Substrate RotationSpatially Resolved Wafer Temperature: 

BandiT Measurement During Substrate Rotation Spatially Resolved Wafer Temperature Speed of solid state spectrometer provides spatially resolved temperature across all wafers Wafer temperature can vary widely depending on thermal contact with holder Temperature uniformity across each wafer depends on holder mechanism