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半導體量測技術 Semiconductor Materials and Device Characterization

半導體量測技術 Semiconductor Materials and Device Characterization Topic 1: resistivity and Four point Probe Instructor: Dr. Yi-Mu Lee Department of Electronic Engineering National United University. Resistivity: Four point probe. Features: two probes: carry current

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半導體量測技術 Semiconductor Materials and Device Characterization

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  1. 半導體量測技術 Semiconductor Materials and Device Characterization Topic 1: resistivity and Four point Probe Instructor: Dr. Yi-Mu Lee Department of Electronic Engineering National United University

  2. Resistivity: Four point probe Features: two probes: carry current two probes: sense the voltage First proposed by Wenner in 1916 Target: from resistivity to S.C. doping profile

  3. Four point probe Voltage probes are very high impedence (~1012 ohms) Negligible: why? (due to a very small current) Rc (contact resistance) Rp (probe resistance) Rsp (spreading resistance) Rsp: occurs when current flows from the probe to S.C and from S.C to probe Special Features: ρ= 2Πs (V/I) 1. S = 1.588mm, 2Πs = 1 2. Smaller probe spacings allow measurements closer to wafer edges

  4. Four point probe Special Features: ρ= 2Πs (V/I) 1. S = 1.588mm, 2Πs = 1 2. Smaller probe spacings allow measurements closer to wafer edges

  5. Figure Scaling

  6. Linear and Log Scaling

  7. Four Point Probe: principle and equation

  8. Resistivity and Conductivity Non-uniform doped sample: D. K. Schroder, p. 10

  9. Doping Profile and depth: --How to determine Na-depth(x)? D. K. Schroder, p. 29

  10. How to determine Na-depth(x)? Using eq. (1.38) ρs = ρ/t ? D. K. Schroder, p. 30

  11. Identifying flats on silicon wafers: D. K. Schroder, p. 42

  12. Current flow through a metal-S.C junction (1) Rectification contact:

  13. n-type substrate: Rectifying contact

  14. Current flow through a metal-S.C junction (2) Ohmic contact:

  15. Ohmic contact with n-type S.C

  16. Ohmic contact with p-type S.C

  17. Determine conductivity type: using 4-point probe Rectification method Current meter n-type silicon: --When ac voltage at probe 2 is “+” Then voltage drop V42 is small (because metal-S.C. is forward biased) --When ac voltage at probe 2 is “-” Then voltage drop V42 is large (because metal-S.C. is reversed biased) Fig. from D. K. Schroder, p. 43

  18. Obtain doping density from resistivity D. K. Schroder, p. 47

  19. Thinking: D. K. Schroder, p. 48

  20. Homework 1: 1.14 1.16 1.19 (D. K. Schroder, ISBN: 0-471-24139-3) Review suggested: ~p. 44 Preview suggested: a. gate capacitance b. C-V curve

  21. Self-study and review Review: p. 43 Section 2.4.2, exercise 2.2 Preview: p. 93~98 Hall effect (principle, measurement configuration)

  22. Homework: • To measure the sheet resistance of a resistor layer, taking into account the parastic series contact resistance, a test structure consisting of resistors with the same width and different length is provided. Measuring the resistances of the resistors with lengths L1 = 10 μm and L2 = 30 μm, the following values are obtained: R1 = 365 ohm and R2 = 1085 ohm, respectively. If the width of the resistors is 5 μm, determine the sheet resistance and the contact resistance values. • Chapter 2 • 2.1 • 2.8

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