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SEMI MF1392-1103 © SEMI 2003 1 SEMI MF1392-1103 TEST METHOD FOR DETERMIN ING NET CARRIER DENSITY PROFILES IN SILICON WAFE RS BY CAPACITANCE-VOLTAGE MEASUREMENTS WITH A MERCURY PROBE This standard was technically approved…

Figure 2

Round Robin Results

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SEMI MF1392-1103 © SEMI 2003 1

SEMI MF1392-1103

TEST METHOD FOR DETERMINING NET CARRIER DENSITY

PROFILES IN SILICON WAFERS BY CAPACITANCE-VOLTAGE

MEASUREMENTS WITH A MERCURY PROBE

This standard was technically approved by the Global Silicon Wafer Committee and is the direct

responsibility of the North American Silicon Wafer Committee. Current edition approved for publication by

the North American Regional Standards Committee on July 12, 2003. Initially available at www.semi.org

October 2003; to be published November 2003. Originally published by ASTM International as ASTM

F 1392-92. Last previous edition ASTM F 1392-02.

1 Purpose

1.1 Net carrier density is a critical parameter in growth

of epitaxial layers of silicon. This test method provides

a means for determining net carrier density without

formation of a special diode structure on the layer. It

may also be used in characterizing net carrier density in

polished silicon wafers.

1.2 This test method can be used for research and

development, process control, and materials specifi-

cation, evaluation, and acceptance purposes.

1.3 In the absence of interlaboratory test data to

establish its reproducibility (see Section 14.2), this test

method should be used for materials specification and

acceptance only after the parties to the test have

established reproducibility and correlation.

2 Scope

2.1 This test method

covers the measurement of net

carrier density and net carrier density profiles in

epitaxial and polished bulk silicon wafers in the range

from about 4 × 10

to about 8 × 10

carriers/cm

−3

(resistivity range from about 0.1 to about 100 Ω·cm in

n-type wafers and from about 0.24 to about 330 Ω·cm

in p-type wafers).

2.2 This test method requires the formation of a

Schottky barrier diode with a mercury probe contact to

an epitaxial or polished wafer surface. Chemical

treatment of the silicon surface may be required to

produce a reliable Schottky barrier diode.

The surface

treatment chemistries are different for n- and p-type

wafers. This test method is sometimes considered

destructive due to the possibility of contamination from

1 DIN 50439, Determination of the Dopant Concentration Profile of

a Single Crystal Semiconductor Material by Means of the

Capacitance-Voltage Method and Mercury Contact, is technically

equivalent to this test method. DIN 50439 is the responsibility of

DIN Committee NMP 221, with which SEMI maintains close liaison.

DIN 50439 is available in German and English from Beuth Verlag

GmbH, Burggrafenstraße 4-10, D-10772, Berlin, Germany.

2 Severin, P. J., and Poodt, G. J.,“Capacitance-Voltage

Measurements with a Mercury-Silicon Diode,” J. Electrochem. Soc,

119, 1384–1388 (1972).

the Schottky contact formed on the wafer surface;

however, repetitive measurements may be made on the

same test specimen.

2.3 This test method may be applied to epitaxial layers

on the same or opposite conductivity type substrate.

This test method includes descriptions of fixtures for

measuring substrates with or without an insulating

backseal layer.

2.4 The depth of the region that can be profiled

depends on the doping level in the test specimen.

Based on data reported by Severin

and Grove,

Figure

1 shows the relationships between depletion depth,

dopant density, and applied voltage together with the

breakdown voltage of a mercury silicon contact. The

test specimen can be profiled from approximately the

depletion depth corresponding to an applied voltage of

1 V to the depletion depth corresponding to the

maximum applied voltage (200 V or about 80% of the

breakdown voltage, whichever is lower). To be

measured by this test method, a layer must be thicker

than the depletion depth corresponding to an applied

voltage of 2 V.

2.5 This test method is intended for rapid carrier

density determination when extended sample

preparation time or high temperature processing of the

wafer is not practical.

2.6 This test method provides for determining the

effective area of the mercury probe contact using

polished bulk reference wafers that have been measured

for resistivity at 23° C in accordance with SEMI MF84

(see Note 1). This test method also includes procedures

for calibration of the apparatus for measuring both

capacitance and voltage.

NOTE 1: An alternative method of determining the effective

area of the mercury probe contact that involves the use of

reference wafers whose net carrier density has been measured

using fabricated mesa or planar p-n junction diodes or

evaporated Schottky diodes is not included in this test method

but may be used if agreed upon by the parties to the test.

3 Grove, A. S., Physics and Technology of Semiconductor Devices

(John Wiley and Sons, New York, 1967) Sections 6.2 and 6.7c.

(a) Depletion Depth as a Function of Dopant Density with Applied Reverse Bias Voltage as a Parameter.

(b) Applied Reverse Bias Voltage as a Function of Dopant Density with Depletion as a Parameter.

Note: The light dashed line represents the applied reverse bias voltage at which breakdown occurs in a

mercury-silicon contact; the heavy dashed line represents 80 % of this voltage, it is recommended that the

applied reverse bias voltage not exceed this value. The light chain-dot line represents the maximum

reverse bias voltage specified in this test method.

Figure 1

Relationship Between Depletion Depth, Applied Reverse Bias Voltage, and Dopant Density