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Topics: Electron, Semiconductor, Scanning electron microscope Pages: 7 (701 words) Published: February 23, 2014
Observation of Semiconductor Elements Using Scanning

Electron Microscope

Hirokazu KIMURA, Hisayuki HIGUCHI. Michiyoshi MAKI
and Hifumi TAMURA
Central Research Laboratory, HITACHI Ltd. Kokubunji. Tokyo. Japan

[Reprinted from Journal of Electron Microscopy Vol. 15, No. I, 1966]

21

( 21 )

Vol. 15, No.1, 21-25, 1966

JOURNAL OF ELECTRON MICROSCOPY

Observation of Semiconductor Elements Using Scanning

Electron Microscope

Hirokazu KIMURA, Hisayuki HIGUCHI, Michiyoshi MAKI
and Hifumi TAMURA
Central Research Laboratory, HITACHI Ltd. Kolcubunji, Tokyo, Japan (Received March 2, 1966)
The physical topography of semiconductor elements has been
observed by using of the scanning electron microscope newly developed in Hitachi Central Research Laboratory .
The voltage topography shows the location of PN junction, the base width of planer type transistor and the voltage drop in in· tegrated circuits. Furthermore, diffusion depth of PN junction becomes visible by the electron voltaic effects.

§ 1. Introduction

MANY

papers have been already reported
on the resolving power and the image
contrast of the scanning electron microscope,
and the semiconductor elements \\ere hitherto
observed by many researchers uSing scanning
microscope.
With the scanning electron microscope, it
is possible to observe the surface topography
as well as material topography utilizing the
difference of the secondary electron coe·
fficient . It is also possible to get "voltage
contrast" \\ hich shows the location of PN
junction in a semiconductor and voltage drop
in a resistor. The primary electrons generate
hole·electron pairs in the semiconductor and
this enables to obtain specimen images on
account of electron voltaic effects.

§ 2.

New Scanning Electron
Microscope

Fig. 1 shows the newly designed scanning
electron microscope. The diameter of its
electron beam spot is about 0.1.u which is
focused sharply by the two-stage demagnifi­
cation electron lens system. The scanning
speed of one frame can be changed four step
wise from 1 sec. to 50 sec. and the scanning

Fig. 1.

General

view

of

new

scanning

electron

microscope .

lines from 200 to 2,500 . At the normal
operating conditions, 20 KV accelerating volt­
age, 10 sec. scanning speed and 1,000 lines
are adopted.
The secondary electrons emitted from the
specimen by the imIJinging primary electrons
are collected by the scintillator whose light
output is detected by a photomultiplier and
led to an amplifier. The secondary electron
beam of 10- 11 Amp. is detectable with SN
ratio as large as 10 and the frequency band­
width of the amplifier is about 30 kC. The

22

H . KIMURA, H . HIGUCHI, M. MAKI

and

(22)

H. TAMURA

energy of secondary electron is analysed by
a simple static electron lens and potential
difference as small as 0.5 e V can be detected .

§ 3.

Observation of PN Junction

by Absorbed Current

Fig. 2 shows the absorbed current image
of a silicon diode of the grown junction type ,
in which both terminals are short·circuited.
The size of the crystal is about 0.3 mm x
0.5 mm x 5 mm. The central darkline shows
a PN junction , the upper part is N type
silicon with donor density of 2 x 10 17 cm- 3 and
lower part P type silicon with 10 20 cm- 3 ac­
cepter density. The stair at PN junction
caused by the difference of etching speed is
Fig. 3.

Absorbed current image of

the same diode.

(The terminol of N type is opened and the signal
from the terminal of P type is detected. )

§ 4.

Observation of Electron Voltaic
Effect in PN Junction

The image of the same area as in Fig. 3
is shown in Fig. 4, in which the circuit for
measuring diode current as shown in Fig. 5
is used . In Fig. 4 the dark parr of the image

Fig. 2 .

Absorbed current

image

of

a

grown type

silicon diode ( Both terminals are short -circuited ) .

clearly...
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