Micro Bolometer Dr. Lynn Fuller, Jackson Anderson

Transcription

1 ROCHESTER INSTITUTE OF TECHNOLOGY MICROELECTRONIC ENGINEERING Micro Bolometer Dr. Lynn Fuller, Jackson Anderson Webpage: Electrical and 82 Lomb Memorial Drive Rochester, NY Tel (585) Department webpage: MicroBolometer.ppt Page 1

2 ADOBE PRESENTER This PowerPoint module has been published using Adobe Presenter. Please click on the Notes tab in the left panel to read the instructors comments for each slide. Manually advance the slide by clicking on the play arrow or pressing the page down key. Page 2

3 OUTLINE Introduction Manufactures & Applications Theory Black Body Radiation Adsorption vs Wavelength Resistors Readout Amplifier Pixel Array Fabrication Process Test Results Packaging Commercial Devices Applications References Homework Page 3

4 INTRODUCTION A Bolometer is an infrared detector that works on a change in resistance resulting from the absorption of radiant infrared energy with wavelengths between 5 and 15µm. These sensors operate at room temperature and do not require cooling. At these wavelengths electron-hole pair generation is not the mechanism for resistance change since the photon energy is not higher than the material band gap. The infrared photons can be absorbed by the free carriers (electrons or holes) increasing their energy which upon relaxation increases the temperature of the material slightly. The sensor should be low mass, able to absorb infrared energy and be thermally isolated from surrounding materials. Materials such as amorphous silicon and vanadium oxide have been used for the sensor material. The resistors themselves should have a large temperature coefficient of resistance (TCR) and low sheet resistance (for low noise). Page 4

5 INTRODUCTION Page 5

6 CAMERA BUSINESS From Yole Development Page 6

7 MANUFACTURERS Agilent Fluke Corporation BAE Systems Raytheon L-3 Communications Infrared Products DRS Technologies GUIDR FLIR Systems Opgal Optronics Ltd Vumii Imaging InfraredVision Technology Corp. NEC Institut National d Optique Honeywell ULIS-IR Page 7

8 APPLICATIONS Page 8

9 DIGIKEY Page 9

10 IR CAMERA FOR THE SMARTPHONE From Yole Development Page 10

11 AGILENT U5855A TRUE IR THERMAL IMAGER Features Power adapter and cord Li-ion rechargeable battery SD memory card USB Standard-A to mini type-b interface cable Laser pointer and LED illuminator Both IR and visual images captured Zoom and fine focus Page 11

12 HOT PLATES IN SMFL Page 12

13 THEORY IR wavelength Resistance Change (Responsivity, TCR) Materials Noise Active vs Passive Page 13

14 BLACK BODY RADIATION From: Micromachined Transducers, Gregory T.A. Kovacs From: Solar Cells, Martin A. Green, Prentice Hall lpeak = 2898 µm / T Wien s Displacement Law lpeak = 2898/T (µm) h = E-34 J s = E-15 ev s l= c/n k=1.38e-23 J/K W l = radiant flux e(l) = emissivity (dimensionless, e=1 for black body) Page 14

15 PLANCK S LAW Planck s Law: (Spectral Radiance) Power per unit time radiated per unit area of emitting surface in the normal direction per unit solid angle per unit frequency. This equation is used to approximate emissions from black body sources. I is spectral radiance (w/m2/.) W l is radiant flux (w/m2) h = E-34 J s = E-15 ev s l= wavelength = c/n n = frequency c = 2.998E8 m/s k =1.38e-23 J/K e(l) = emissivity (dimensionless, e=1 for black body) Page 15

16 Adsorption Coefficient, a (1/cm) ABSORPTION VERSUS DISTANCE V I 1.00E+06 Absorption Coefficient vs Wavelength For Silicon n p I 1.00E E E E E E E-01 + V - I No Light More Light Most Light V 1.00E E E E E Wavelength (nm) f(x) = f(0) exp -a x Find % absorbed for Green light at x=5 µm and Red light at 5 µm Page 16

17 SILICON IS TRANSPARENT TO INFRARED Visible Picture Infrared Picture Note: eyeglass temperature is 25.6 C, face is ~30 C, and neck is ~35 C Page 17

18 ABSORPTION FOR POLYSILICON pg 210 Figure 7 by Timans et al. "Rapid Thermal Processing," in "Handbook of Semiconductor Manufacturing Technology," Nishi and Doering ed. Copyright Indicates free carrier absorption, higher doping gives higher absorption. At 1E19 cm-3 doping the absorption coefficient is ~5E3/cm much higher than single crystal silicon absorption shown above. (still looking for better absorption data) Page 18

19 EXAMPLE CALCULATIONS Calculate the response for a micro bolometer pixel (single resistor) to IR radiation from a black body emitter. Assumptions: IR Source Temperature = 300 C =573 K IR Source Physical Dimensions 8 x8 square plate, Emissivity = 1 Distance to the detector 10cm = 0.1m Detector Physical Dimensions and Properties N+ Polysilicon, Thickness 1.7um Doping 1E16cm-3, rhos=50 ohms/sq 100um x 100um pixel area Suspension in air, gap of 2um Suspension poly silicon 1.7um x 400um x 40um with aluminum 0.7um x 400um x 20um Page 19

20 EXAMPLE CALCULATIONS Assumptions: Assume Detector Absorption Coefficient is 5e3/cm constant for all wavelengths (1.3um to 10um) Si Window over detector (to block visible light) 55% transmission in IR from 1.3um to 10um Constants: Plank s Constant h=6.63e-34 J/s Boltzmann's Constant k=1.38e-23 J/K Speed of light c=2.998e8 m/s Thermal Conductivity (w/cmk) Si = um Al = 2.36 Air = SiO2 = Si3N4 = Layout Page 20

21 CALCULATION OF THERMAL RESISTANCE Calculation of thermal resistance between detector and ambient. Three parallel paths, through air, through poly suspension, through aluminum on suspension. Rth = (1/Cth) L/Area Air: Poly: Al: Cth= w/cmk, L=2um, Area=100um x 100um Rth air = 7692 K/w Cth=1.5 w/cmk, L=400um, Area=1.7um x 40um Rth poly = K/w Cth=2.36 w/cmk, L=400um, Area=0.7um x 20um Rth al = K/w Rth total = ~7000 K/w mostly the air gap Page 21

22 CALCULATION OF POWER FROM THE SOURCE Calculation of the power emitted from the source. The Power radiated from the source is equal to the Integral (sum) of the Spectral Radiance over the IR spectrum (1.3um to 10um) at the given source temperature. Planck s Law: (Spectral Radiance) Power per unit time radiated per unit area of emitting surface in the normal direction per unit solid angle per unit frequency. This is for a hemispherical emission source. Page 22

23 Spectral Radiance (W/(m^2*Hz*steradian)) CALCULATION OF POWER REACHING THE DETECTOR The power reaching the detector is the integral (sum) of the emission versus wavelength, the area under the curve. If a silicon filter is used to block visible light we also multiply by the % transmission versus wavelength. The distance between the source and the detector and the area of the detector determine the solid angle in steradians. 4.00E E E E E E-11 Emission of a Blackbody at Given Temperature At Bolometer At Bolometer, with Si lens Any area on a sphere which is equal in area to the square of its radius, when observed from its center, subtends precisely one steradian. 1.00E E E l= wavelength = c/n n = frequency c = 2.998E8 m/s Wavelength (um) Page 23

24 CALCULATION OF POWER ABSORBED BY DETECTOR Solid angle = area of detector/distance 2 = 100um x 100um / 0.01m 2 = 1e-8 /.01 = 1E-6 Transmission through crystalline silicon filter = 55% Frequency = speed of light/wavelength After Filter Power = ~ 2E-11 x 1E-6 x 3E8/5um = watt/m2 Using the absorption coefficient of a =5E3/cm and thickness x=1.7um % absorption = 1- exp ( a x) = 57% Total Power absorbed by the detector Power total = x 57% = 6.84E-4 watts Page 24

25 CALCULATION OF RESISTANCE Total Power absorbed by the detector Power total = x 57% = 6.84E-4 watts Change in temperature = Power total x Thermal Resistance = 6.8e-4 w x 7000 K/w = K Resistance at 25 C, R = Rhos L/W + modifications for poly See Dr. Fullers Resistance Calculator R@300 K = ohms Resistance at elevated temperature C R@ K = ohms Page 25

26 CALCULATION OF RESISTANCE See Dr. Fullers Resistance Calculator K = ohms R@ K = ohms TCR Microelectronic = Engineering DR/DT =0.04 ohm/4.79 K = 0.835% Page 26

27 CIRCUIT CALCULATIONS V -V R This output voltage can be easily amplified Vout = 3 x -1.5 = mv R2 I = 3 / = 13.7 ma Power = I 2 R = (13.7mA) = mw Compared to signal power of mw This power is too large. A different circuit approach is needed. Page 27

28 CIRCUIT LTSPICE SIMULATION Page 28

29 CIRCUIT LTSPICE SIMULATION Vout 4.236mV Difference giving sensitivity = 14.1 uv/ K Power in Rsensor mw Compared to signal power of mw Page 29

30 Substrate set at 298 K SOLID WORKS SIMULATION Page 30

31 SUSPENDED POLYSILICON RESISTOR Page 31

32 SUSPENDED POLYSILICON RESISTOR Resistor No Heat Heat (No Light) Heat (Uncovered) Resistance Ω Ω Ω Page 32

33 SUSPENDED POLYSILICON RESISTOR Sensitivity = 10mohms/267ohms/100/ C = 0.004%/ C Compared to industry TCR s of 2.0%/ C Page 33

34 PIXEL LAYOUT Row Select V+ Column Vout Page 34

35 Column Out SINGLE PIXEL AND READOUT AMPLIFIER V+ Row Select Rs Pixel Readout Amp Vref - + Rref R1 + - R2 Analog Vout Page 35

36 Row Address Row Decoder Micro Bolometer 4x4 PIXEL ARRAY Column Address Column Amps & Analog Mux Serial Output Page 36

37 RESISTOR - BOLOMETER Page 37

38 RESISTOR 2 - BOLOMETER Page 38

39 RESISTOR 1 - BOLOMETER Page 39

40 RESISTOR 3 - BOLOMETER Page 40

41 Layout 12/23/2016 Jackson Anderson - Page 41 41

42 RESISTOR 2 641Ω Page 42

43 PICTURE OF PHOTOMASKS Page 43

44 DARK FIELD RETICLE FOR ASML Anchor, Non-Chrome Side Page 44

45 ASML 5500/200 NA = 0.48 to 0.60 variable = 0.35 to 0.85 variable With Variable Kohler, or Variable Annular illumination Resolution = K1 l/na = ~ 0.35µm for NA=0.6, =0.85 Depth of Focus = k 2 l/(na) 2 = > 1.0 µm for NA = 0.6 i-line Stepper l = 365 nm 22 x 27 mm Field Size Page 45

46 STEPPER JOB Mask Barcode: Stepper Jobname: MCEE770-MEMS Level 0 (combi reticle) Level Clearout (combi reticle) Level SacOx Level Poly 1 Level Anchor Level Poly 2 Level CC Level Metal Level No Implant Level Release Page 46

47 SURFACE MEMS 2016 PROCESS 1. Starting wafer 2. PH03 level 0, Marks 3. ET29 Zero Etch 4. ID01-Scribe Wafer ID, D1 5. ET07 Resist Strip, Recipe FF 6. CL01 RCA clean 7. OX Å Oxide Tube 1 8. CV01 LPCVD Poly 5000Å 9. IM01 Implant P31, 2E16, 60KeV 10. PH03 level 1 Poly ET08 Poly Etch 12. ET07 Resist Strip, Recipe FF 13. CL01- RCA Clean 14. OX05 700Å Dry Oxide 15. CV02- LPCVD Nitride 4000Å 16. PH03 level 2 Anchor 17. ET29 Etch Nitride 18. ET07 - Resist Strip, Recipe FF 19. CL01 RCA Clean 20. CV03-TEOS SacOx Dep 1.75um 21. PH03 level 3 SacOx Define 22. ET06 - wet etch SacOx Define Etch 23. ET07- Resist Strip, Recipe FF 24. CL01 RCA Clean 25. CV01-LPCVD Poly 2um, 140 min 26. PH03 - level 4 No Implant 27. IM01-P31 2E16 100KeV 28. ET07 Resist Strip, Recipe FF 29. CL01 RCA Clean 30. OX05-500Å pad oxide 31. CV Å nitride 32. PH03 - level 5 Poly2 33. ET29 Plasma Etch Nitride 34. ET06 Wet Etch pad oxide 35. ET68 - STS Etch Poly2 36. ET07 - Resist Strip, Recipe FF 37. PH03 level 6 Contact Cut 38. ET29 Etch Nitride Contact Cut 39. ET06 Etch Oxide Contact Cut 40. ET07 Resist Strip, Recipe FF 41. CL01 RCA Clean two HF 42. ME01 Metal Deposition - Al 43. PH03 level 7 Metal 44. ET55 Metal Etch - wet 45. ET07 Resist Strip 46. PH03 level 8 Release 47. SA01 Saw wafers ½ Thru 48. Special Soap Clean 49. ET66 Final SacOx Etch 50. ET07 - Resist Strip with Acetone 51. Rinse and Dry w Isopropyl Pull 52. TE01 wafer level testing 53. SEM1 Pictures 54. Packaging and Testing Page 47

48 SURFACE MEMS 2015 PROCESS 1. Starting wafer 2. PH03 level 0, Marks 3. ET29 Zero Etch 4. ID01-Scribe Wafer ID, D1 5. ET07 Resist Strip, Recipe FF 6. CL01 RCA clean 7. OX Å Oxide Tube 1 8. CV01 LPCVD Poly 5000Å 9. IM01 Implant P31, 2E16, 60KeV 10. PH03 level 1 Poly ET08 Poly Etch 12. ET07 Resist Strip, Recipe FF 13. CL01- RCA Clean 14. OX05 700Å Dry Oxide 15. CV02- LPCVD Nitride 4000Å 16. PH03 level 2 Anchor 17. ET29 Etch Nitride 18. ET07 - Resist Strip, Recipe FF 19. CL01 RCA Clean 20. CV03-TEOS SacOx Dep 1.75um 21. PH03 level 3 SacOx Define 22. ET06 - wet etch SacOx Define Etch 23. ET07- Resist Strip, Recipe FF 24. CL01 RCA Clean 25. CV01-LPCVD Poly 2um, 140 min 26. PH03 - level 4 No Implant 27. IM01-P31 2E16 100KeV 28. ET07 Resist Strip, Recipe FF 29. CL01 RCA Clean 30. OX05-500Å pad oxide 31. CV Å nitride 32. PH03 - level 5 Poly2 33. ET29 Plasma Etch Nitride 34. ET06 Wet Etch pad oxide 35. ET68 - STS Etch Poly2 36. ET07 - Resist Strip, Recipe FF 37. PH03 level 6 Contact Cut 38. ET29 Etch Nitride Contact Cut 39. ET06 Etch Oxide Contact Cut 40. ET07 Resist Strip, Recipe FF CL01 RCA Clean two HF 42. ME01 Metal Deposition - Al 43. PH03 level 7 Metal 44. ET55 Metal Etch - wet 45. ET07 Resist Strip 46. PH03 level 8 Release 47. SA01 Saw wafers ½ Thru 48. ET66 Final SacOx Etch 49. ET07 - Resist Strip, Recipe FF 50. SEM1 Pictures 51. TE01 - Testing Page 48

49 SURFACE MEMS 2015 PROCESS 1. Starting wafer 2. PH03 level 0, Marks 3. ET29 Zero Etch 4. ID01-Scribe Wafer ID, D1 5. ET07 Resist Strip, Recipe FF 6. CL01 RCA clean 7. OX Å Oxide Tube 1 8. CV01 LPCVD Poly 5000Å 9. IM01 Implant P31, 2E16, 60KeV 10. PH03 level 1 Poly ET08 Poly Etch 12. ET07 Resist Strip, Recipe FF 13. CL01- RCA Clean 14. OX05 700Å Dry Oxide 15. CV02- LPCVD Nitride 4000Å 16. PH03 level 2 Anchor 17. ET29 Etch Nitride 18. ET07 - Resist Strip, Recipe FF 19. CL01 RCA Clean 20. CV03-TEOS SacOx Dep 1.75um 21. PH03 level 3 SacOx Define 22. ET06 - wet etch SacOx Define Etch 23. ET07- Resist Strip, Recipe FF 24. CL01 RCA Clean 25. CV01-LPCVD Poly 2um, 140 min 26. PH03 - level 4 No Implant 27. IM01-P31 2E16 100KeV 28. ET07 Resist Strip, Recipe FF 29. CL01 RCA Clean 30. OX05-500Å pad oxide 31. CV Å nitride 32. PH03 - level 5 Poly2 33. ET29 Plasma Etch Nitride 34. ET06 Wet Etch pad oxide 35. ET68 - STS Etch Poly2 36. ET07 - Resist Strip, Recipe FF 37. PH03 level 6 Contact Cut 38. ET29 Etch Nitride Contact Cut 39. ET06 Etch Oxide Contact Cut 40. ET07 Resist Strip, Recipe FF CL01 RCA Clean two HF 42. ME01 Metal Deposition - Al 43. PH03 level 7 Metal 44. ET55 Metal Etch - wet 45. ET07 Resist Strip 46. PH03 level 8 Release 47. SA01 Saw wafers ½ Thru 48. ET66 Final SacOx Etch 49. ET07 - Resist Strip, Recipe FF 50. SEM1 Pictures 51. TE01 - Testing Page 49

50 FABRICATION PROCESS Starting Wafer with Electronics Poly One Photo Etched Poly Bottom Electrode 6500Å Field Oxide LPCVD Nitride Etch Stop Å Poly n-type Oxide from TEOS 1.7µm Page 50

51 FABRICATION PROCESS Photo for SacOx Define Wet Etch TEOS Sacrificial Oxide 1.7µm Mechanical No Implant Masking, then implant n+ Poly Photo Anchor Holes Etch Anchor Holes Etch Poly STS Etcher Page 51

52 FABRICATION PROCESS LPCVD Nitride Deposit Metal Photo and Etch Metal 12. CC Photo Etch Contact Cuts 14. Photo Release Etch SacOx Page 52

53 FABRICATION PROCESS Final Cross Section Page 53

54 PICTURE OF FINAL DEVICE Page 54

55 PACKING AND TESTING Rosewell Infrared Thermometer Hot Plate RIT Sensor Page 55

56 SUMMARY Much more work is needed to finish this study. TCR of resistors needs to be increased by 1000 over what we measured in the proof of concept study. New materials such as Ni Oxide has been proposed for the sensor resistors. Page 56

57 REFERENCES 1. Micro Bolometer. Wikipedia: The Free Encyclopedia. Wikimedia Foundation, Inc., 3 May Web. 2. Device Electronics for Integrated Circuits, Richard S. Muller, Theodore I. Kamins, Mansun Chan, John Wiley & Sons.,3 rd Ed., Micromachined Transducers, Gregory T. A. Kovacs, McGraw Hill, Page 57

58 HOMEWORK MICRO BOLOMETER 1. A coffee cup at ~100 C emitts Black Body radiation. Calculate the wavelength at which the peak emission occurs. 2. more Page 58