TimeResolved Thermoreflectance Imaging for Thermal Testing and Analysis

Time-Resolved Thermoreflectance Imaging for Thermal Testing and Analysis Dr. Mo Shakouri Chairman Microsanj, LLC. , Silicon Valley USA info@microsanj. com

Applications SEMICON JAPAN 2013 - MICROSANJ

Outline 1. 2. 3. 4. 5. 6. Motivation Instrumentation Lock-in mechanism Imaging through silicon (near IR) Diffusion length Examples Small hotspot / Logic circuitry / Emission / Depth in metal layers 7. Summary SEMICON JAPAN 2013 - MICROSANJ

Challenges on thermal characterization General challenges for electronics devices • Small features: 10 s nm – 100 s microns – difficult to contact • High speed response due to the small thermal mass • Highly non-uniform Additional challenges for photonics and power devices • Light emission (photonics) • High heat density • Heat sinks requirement (power devices) SEMICON JAPAN 2013 - MICROSANJ

Thermoreflectance imaging setup Console box Microscope setup CCD Sig. gen. Temp. contl. LED Control box. Objective lens DUT SEMICON JAPAN 2013 - MICROSANJ

How it works - thermoreflectance LED driver Power LED GP-IB PC Detector CCD, In. Ga. As Light Microscope Objective Device Pulse generator & power amp Thermal bed System diagram Thermoreflectance coefficient SEMICON JAPAN 2013 - MICROSANJ

Lock-in signals Timing chart 4 ms @ 25% Duty Cycle Device Excitation 1 ms CCD exposure 33 ms @ 30 Hz LED pulse t 0 100 ms t 0 delay t 1 Temperature Acquisition timing (shifting by cycle) Temperature data point along the bias cycle SEMICON JAPAN 2013 - MICROSANJ

Through silicon and emission In. Ga. As CCD Top view 1300 nm LED Objective Substrate Flip Chip DUT % Transmittance vs Wavelength, Si (Image from http: //www. janis. com) Bottom view resolution 1. 0 10. 0 Wavelength, mm SEMICON JAPAN 2013 - MICROSANJ

Defects and signature of potential failure Emission – sign of high density of electron collisions Thermal hotspot – location of potential long-term reliability Thermal foot print irregular local energy spot Arrhenius's law Transient irregular timing - potential of logic/operation failure Near Infrared (NIR) wavelength provide a capability of both thermal signal and emission simultaneously. LED options: 1050, 1200, 1300, and 1500 nm SEMICON JAPAN 2013 - MICROSANJ

Resolution and sensitivity Temperature n : number of averaging due to the weak signal (Cth ~ 10 -4 order) Spatial resolution Visible wavelengths, d ≈ 250 -300 nm NIR d ≈ 500 nm d ≈ l/2 Time resolution As scaling smaller, time resolution must be smaller due to thermal diffusion. Dt : 100 ns for our setup. (for 1% error in temperature) Emission In. Ga. As uncooled camera effective sensitivity of one pixel for emission ~ 30 m. W/mm 2 SEMICON JAPAN 2013 - MICROSANJ

Examples - Small hotspot a) 1. 4 mm mm gate on MOSFET b) Temperature (a. u. ) 60 50 40 40 30 20 10 0 0 2 4 6 Distance (mm) SEMICON JAPAN 2013 - MICROSANJ 8 10 12

Transient Behavior of IC Latch-Up Movie 1 - Potential timing failure 0. 5 ms 0. 7 ms 0. 9 ms 1. 0 ms 3. 0 ms The latch-up location is circled in yellow SEMICON JAPAN 2013 - MICROSANJ

Thermal and emission overlay images 5 x Thermal signals Through silicon substrate, 450 mm thick. LED l = 1300 nm and In. Ga. As camera (640 x 512) 50 x Emission signals 44 m. W SEMICON JAPAN 2013 - MICROSANJ

Diffusion time/depth estimations m: depth of heat source a: thermal diffusivity [m 2/s] t: time to reach observing surface SEMICON JAPAN 2013 - MICROSANJ

Examples - Through silicon, deep under the 6 th metal layer 2. 0 msec 0. 97 V, ~12 m. A, ~12 m. W 20% duty cycle 10 minutes of averaging (repeating) SEMICON JAPAN 2013 - MICROSANJ Movie 2

Time delay to reach to the surface Precise time resolution is a key to find the response. SEMICON JAPAN 2013 - MICROSANJ

Microsanj, a technology leader in thermal imaging field q Founded by a team of Ph. Ds from Cal. Tech, Stanford, and UCSC in 2007 q More than 30 papers published to date q. Major Customers ü ü ü ü ü q. Collaborative Research Activities Chip Test Solutions Design Engineering Inc. (DEI) Infinera Instituto de Microelectronica de Barcelona (CSIC) Intel Corporation Nanyang Technological University Purdue University Raytheon Silicon Image University of California Santa Barbara ü ü ü A*Star Singapore Altera Corporation Birck Nanotechnology Center at Purdue University Nvidia Philips Electronics Qualcomm Silicon Frontline Si-Ware Systems ST Microelectronics Texas Instruments (National Semiconductor) University of California at Santa Cruz SEMICON JAPAN 2013 - MICROSANJ

Summary High speed time-resolved thermoreflectance imaging is introduced. NIR illumination provides a through Si and electron emission Lock-in thermography and EMMI are compared. Examples demonstrated: Hotspots ~ 1 mm, emission and thermal overlay, and a hotspot underneath 6 metal layers SEMICON JAPAN 2013 - MICROSANJ

Transient thermal/emission imaging Resolution x(mm) T (K) Imagt (sec) ing? m Thermocouple 50 0. 01 0. 1 -10 No Contact method IR Thermography 3 -10 0. 02 -1 1 m Yes Emissivity dependent Lock-in Thermog. 3 -10 1 m NA Yes Need cycling Method Notes Liquid Crystal Thermography 2 -5 0. 5 100 Yes Only near phase transition (aging issues) Thermoreflectance 0. 3 - 0. 5 0. 08 800 p- 0. 1 m Yes Need cycling Optical scanning Interferometry 0. 5 100 m 6 n- 0. 1 m Scan Indirect measurement (expansion) Micro Raman 0. 5 1 10 n Scan 3 D T-distribution Scanning thermal microscopy (STh. M) 0. 05 0. 1 10100 m Scan Contact method surface morphology Emission Microscopy (EMMI) 0. 25 - Op lock-in Yes Emitted Photon density s. im. lens SEMICON JAPAN 2013 - MICROSANJ