This document discusses techniques for measuring junction depth and sheet resistance of diffused layers. It describes two common junction depth measurement methods: the groove-and-stain method which uses etching and staining to measure junction depth, and the angle-lap method which mounts and laps the wafer edge to create an interference pattern for measurement. The document also outlines two sheet resistance measurement techniques: the four-point probe method for infinite sheets, and Van der Pauw's method which applies a correction factor to resistance measurements taken from multiple contacts.

1. MESSUREMENT METHODS
OF JUNCTION-DEPTH & SHEET
RESITANCE OF DIFFUSED LAYER
Hoang Tuan Linh
Nguyen Van Long
Nguyen Minh
Hanoi, Dec 2nd 2016

2. CONTENT
• Overview of diffused layer
• Junction-depth measurement techniques
• Sheet-resitance measurement techniques
2

3. I. Junction-depth measurement techniques
1. Groove-and-Stain Method
2. Angle-lap Method
3

4. 1. Groove-and-Stain Method
44
Step 1. Cut a cylindrical groove
Step 2. Etching with solution: 100 cm3 HF (49%) and HNO3
Step 3. Exposure to high-intensity light
Result: The p-type region will be stained darker than the n-type region
𝑥𝑗 = 𝑅2 − 𝑏2 − 𝑅2 − 𝑎2
𝑥𝑗 =
𝑎2 − 𝑏2
2𝑅
• R >> a, b:

5. 2. Angle-lap Method
5
1
• Wafer is mounted on special fixture
2
• Lap the edge at 1o -5o
3
• Using a chemical etchant that stains
the p-n junction.

6. 2. Angle-lap Method
6
𝑥𝑗 = 𝑑tan𝜃 = 𝑁 𝜆 2
Test structure
• A optically flat piece of glass on
lapped region
• Collimated monochromatic beam
(𝜆), typically from sodium vapor
lamp
The resulting interference
pattern has fringe lines:
• Counted by microscope
• Notatinon: N
Source: “Technology of Quantum Devices” – Manijeh Razeghi

7. II. Sheet-resitance measurement techniques
7
Sheet-resitance = Ω/□ (ohm per square) (*)
𝑹 𝑺 = [𝒒 𝝁 𝑪 𝑪 𝒆 𝒙 𝒅𝒙]−𝟏
[𝜴 /□]
𝐶𝑒 𝑥 : dopant concentration; 𝜇 𝐶 : mobility depend on concentration
𝑅 𝑆: square-resistance
When it expresses the electrical
resistance of a sheet (such as a thin
film or a film-like substance), this
sheet-resitance is used. R ＝ ρ × L/A ＝ L/W ×ρs
ρ 𝑺 = ρ/t (t: thickness)
For semiconductors:
(*) Source: http://en.napson.co.jp/technique/

8. II. Sheet-resitance measurement techniques
8
2 ways to meassure sheet-resistance:
- 4-point probes method
(4-terminal sensing/ 4-wire sensing)
- Van der Pauw method

9. II. Sheet-resitance measurement techniques
9
a) 4-point probes method
Source: http://en.napson.co.jp/technique/
Diffusion from 1 side!
Infinite sheet (d>>S)!

10. II. Sheet-resitance measurement techniques
10
b) Van der Pauw method
Source: www.researchgate.net
(a) Schematic of the Van der Pauw method for measuring the sheet resistance.
(b) The measured sheet resistance of the silver film with different thickness, the
inserted Figure shows the SEM picture of a silver film with a size of 130 μ m
× 130 μ m.

11. II. Sheet-resitance measurement techniques
11
b) Van der Pauw method
𝑹 =
𝟏
𝟒
[
𝑽 𝟏𝟐
𝑰 𝟑𝟒
+
𝑽 𝟐𝟑
𝑰 𝟒𝟏
+
𝑽 𝟑𝟒
𝑰 𝟏𝟐
+
𝑽 𝟒𝟏
𝑰 𝟐𝟑
]
𝑹 𝑺 =
𝝅
𝒍𝒏𝟐
𝑭 𝑸 . 𝑹
F(Q): correction factor (depend
on the shape of the sample)
Square => F(Q) = 1; 𝑅 𝑆 = 4.53𝑅
Source: “Công nghệ chế tạo mạch vi điện tử”
– GS.Nguyễn Đức Chiến

12. 12
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