k SA Bandi T Bandedge Thermometry kSpace Associates

k. SA Bandi. T: Band-edge Thermometry k-Space Associates, Inc.

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. k-Space Associates, Inc.

Band-edge Thermometry vs. Pyrometers § Pyrometers: • Typically inaccurate or no measurement below 400 -450 o. C • 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 k-Space Associates, Inc.

k. SA Bandi. T vs. Competitor Instruments • State-of-the-art solid state spectrometer - 1000 x 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 k-Space Associates, Inc.

k. SA Bandi. T Product Specifications Bandi. T System Schematic k-Space Associates, Inc.

k. SA Bandi. T Product Specs. Cont’d Bandi. T Light Source • • • 150 W halogen lamp with gold coated parabolic reflector. Light source collimating optics. Real-time output power control via Bandi. T software. Internal feedback control for stable intensity and spectral output. NOTE: above ~300 o. C can use heater as light source k-Space Associates, Inc.

k. SA Bandi. T Product Specs. Cont’d Bandi. T 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. k-Space Associates, Inc.

k. SA Bandi. T Product Specs. Cont’d § Spectrometer Visible Model (B-VIS): • 512 x 64 element Peltier-cooled CCD array detector • Wavelength Range: 380 nm – 1100 nm or custom • Si. C, Zn. Te, Zn. Se substrates NIR Model (B-NIR): • • • 128 element In. Ga. As temperature stabilized photodiode array with onboard interpolation yields 1024 elements Wavelength Range: 875 nm – 1400 nm Ga. As, Si, In. P substrates k-Space Associates, Inc.

k. SA Bandi. T 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 k-Space Associates, Inc.

k. SA Bandi. T Performance Specifications Wavelength Ranges: 380 -1100 nm 1 875 -1400 nm 2 Temperature Update Rate: 20 Hz typical, 1 Hz minimum Typical Temperature Ranges: Zn. Se: RT – 700 °C 1 Zn. Te: RT – 700 °C 1 Si. C: RT – 700 °C 1 Ga. As: RT - Temperature Resolution: 0. 1 °C 2 690 °C Stability: In. P: 650 °C 2 +/- 0. 2 °C (4 hours) Si: 600 °C 2 Accuracy: +/- 2 °C Outputs: Real-time display Thermocouple (selectable) 10 V analog (configurable) Inputs: Thermocouple, Analog RT RT – k-Space Associates, Inc.

Bandi. T Stability Data – Ga. As @ 300 C k-Space Associates, Inc.

k. SA Bandi. T Performance Specs (cont’d) • Noise from rotation ~1 -2 o. C for all size wafers • Pyrometer noise typically much worse for ¼ X 3” pieces • No interference from: • hot sources • highly doped epi (2 um of Ga. As: C, p = 6. 5 e 19/cm 3) • high-on-low Eg growth (Al. Ga. As/Ga. As) • Low-on-high Eg growth: In. Ga. As/In. P • In. Ga. As strong IR absorber • Clean measurement thru ~ 1. 2 um of epi (using heater only) k-Space Associates, Inc.

k. SA Bandi. T Calibration File Generation Calibration depends on: • material • thickness • dopant level k-Space Associates, Inc.

Bandi. T, TC, and Pyro Measurement Ga. As Oxide Desorption Pyro reads high at low temps because substrate is transparent k-Space Associates, Inc.

Interference Oscillations in temperature k-Space Associates, Inc.

Low Temp Ga. As Growth TC does not see temp rise due to As Absorption Temp increase due to As absorption k-Space Associates, Inc.

Bandi. T 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 k-Space Associates, Inc.