JPS5933266B2 - Method and device for determining P-type and N-type semiconductors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for determining whether a semiconductor is P-type or N-type.

As is well known, determining whether a semiconductor is P-type or N-type is the most fundamental step in evaluating the characteristics and quality of semiconductors in research or manufacturing.

2. Description of the Related Art Conventionally, a method is known in which the Hall effect of a semiconductor is used to determine whether a semiconductor is P-type or N-type. According to this method, a semiconductor to be determined is cut into the shape shown in FIG. 1 by ultrasonic processing, and a current Ix is applied between electrodes 1 and 2.
While applying a magnetic field H2 in a direction perpendicular to the direction in which the current Ix flows, a Hall voltage Vy is generated in a direction perpendicular to the direction in which the current Ix flows and the direction in which the magnetic field H2 is applied.
is measured by a potentiometer provided between the electrodes 3 and 4, and the P type or N type of the semiconductor 5 is determined from the polarity of this Hall voltage Vy. Although this method can measure the conductivity of a semiconductor at the same time, it is time-consuming because the semiconductor must be processed as shown in Figure 1, and is too inefficient to be used in the semiconductor manufacturing process, for example. . Therefore, a method as shown in FIG. 2 is known.

That is, two electrodes 7,
8 and heats one electrode T, and uses an ammeter 9 to read the direction in which current flows due to donor charges and acceptor charges generated inside the surface area of the semiconductor 6 that the electrode T contacts. Distinguish whether the semiconductor 6 is P type or N type. This method is convenient because it uses a simple device and can be carried out easily, and it does not require ultrasonic processing of the semiconductor as in the case shown in FIG. On the other hand, it takes time j to heat the electrode
This method is time consuming and inefficient, and it may be difficult to distinguish between P type and N type depending on the surface condition of the semiconductor, resulting in poor reliability. The present invention has been made in view of the above-mentioned circumstances, and its purpose is to improve the efficiency of discrimination work and to provide reliable P-type and N-type semiconductors.
The object of the present invention is to provide a type discrimination method and an apparatus for carrying out the method. That is, in the present invention, three needle-like electrodes are brought into contact with the semiconductor surface of a sample to be determined, and a current is passed between two of these needle-like electrodes, while the three needle-like electrodes are A light pulse is irradiated onto the contacting semiconductor surface,
One of two needle-shaped electrodes out of three that are passing current
A method characterized by determining whether a semiconductor is P-type or N-type based on the polarity of a pulse signal generated between a book and a needle-shaped electrode through which no other current is flowing, and the semiconductor surface of the object to be determined. three needle-like electrodes brought into contact with the needle-like electrodes; a constant current power source that supplies current between two of these needle-like electrodes;
A light pulse generator that irradiates a light pulse to a semiconductor surface area where three needle-like electrodes are in contact, one of two of the three needle-like electrodes through which current is flowing, and the other needle-like electrodes. The present invention relates to a device characterized in that it is equipped with a detector that detects the polarity of a pulse signal generated between the present invention and one needle-like electrode through which no current is flowing. The present invention will be explained below.

In FIG. 3, 10, 11, and 12 are needle-shaped electrodes, 13 is a semiconductor of a sample to be determined, 14 is a constant current power source, 15 is a light pulse generator, 16 is a detector, 17 is a selection switch, 18, 19, 2
0 is the lead wire of each electrode, 17a is a of the selection match 17
The contact 17b is the b contact of the selection switch 17.

Here, the needle electrodes 10, 11, and 12 have sharp tips, a diameter of about 0.5 mm, and are made of tungsten carbide, tungsten, etc., and are in contact with the surface of the semiconductor 13 of the sample to be determined. I'm starting to do that.

The three needle electrodes 10, 11, 12 may be arranged in any order, and the three needle electrodes do not necessarily have to be arranged in a straight line.

In explaining the present invention, FIG. 3 will be used as a representative example, and the following explanation will be made with reference to FIG.

In FIG. 3, the spacing between the needle electrodes 10, 11, and 12 is set to about 1 m11 to 100 mm, and they are arranged in a straight line.

Further, it is designed to come into contact with the surface of the semiconductor 13 with a contact pressure of about 65 tons. Further, the constant current power supply 14 has a short circuit current value of about 1 mA to 100 mA, and the needle electrode 10,
The needle-like electrodes 10 and 12 located at both ends of the needle-like electrodes 11 and 12 are in contact with each other, and a direct current of about 10 mA is passed between the needle-like electrodes 10 and 12. Note that the constant current power supply 14 does not need to be a constant current power supply in the strict sense as long as it has a high output impedance. Also,
The optical pulse generator 15 uses a xenon lamp, a laser diode, etc. as a light emitting source, and has needle electrodes 10,
A light pulse is irradiated onto the surface of the semiconductor 13 where the semiconductor devices 11 and 12 are in contact.

Further, the detector 16 is composed of an oscilloscope with a maximum vertical sensitivity of 5 mv/Div or more and a frequency characteristic of 10 MHz or more.
are connected, and the lead wires 19 and 20 provided respectively to the needle electrodes 10 and 12VC are connected via the selection switch 17, and a light pulse is irradiated from the light pulse generator 15 to the surface of the semiconductor 13. A pulse signal output from between needle-like electrodes 10 and 11 or between needle-like electrodes 12 and 11 is measured.

Further, the selection switch 17 is constituted by an ordinary snap switch, and the switch contacts 17a and 17b are connected to the ends of the lead wires 19 and 20.

Next, a method for determining whether a semiconductor is P-type or N-type using the above-mentioned apparatus will be described.

First, an N-type (or P-type) semiconductor sample, which has been determined in advance as a semiconductor 13, is placed on the needle electrodes 10, 11, 12.
with a constant contact pressure.

Next, the needle electrodes 10 located at both ends are connected to the constant current power source 14.
, 12, and a light pulse is irradiated from the light pulse generator 15 to the surface portion of the semiconductor 13 that is in contact with the needle electrodes 10, 11, 12. At this time, the switch contact of the selection switch 17 is 17a (or 1
7b), and the pulse signal generated between electrodes 10 and 11 (or between electrodes 11 and 12) is detected by detector 16.
Make a trigram by observing it. Then, the fourth
Either a positive pulse as shown in Figure 2 or a negative pulse as shown in Figure 4C is observed. Then, check whether the output pulse is positive or negative in the N type (or P type). Temporary VC. Let's assume that the output pulse is a positive pulse in the N type, then it will be observed as a negative pulse in the P type. Therefore, by observing the positive and negative pulse signals with the detector 16, it is possible to determine whether the semiconductor 13 is P type or N type. Here, the semiconductor 13 of the sample to be determined is one whose surface condition is as it was cut with a diamond cutter (sliced surface), and one whose surface condition is as it is (sliced surface), and one whose surface condition is as it is (sliced surface), and one whose surface condition is as it is (slice surface) There are some types (mirror surface), those that have been chemically polished with an etching solution (etched surface), and those that have been mechanically polished with an abrasive such as alumina (lap surface).

The present invention has the advantage that these surface conditions (slice surface, mirror surface, etched surface, lap surface, etc.) can be measured at any time.

Next, the principle of measuring P type and N type in the present invention will be briefly explained.

When the light pulse is not irradiated, the needle electrode 1
The waveform of the DC current flowing between 0 and 12 is linear as shown in FIG. 4A.

Therefore, a light pulse with a waveform as shown in the opening of the same figure is applied to the needle electrode 1.
When irradiating the area where 0, 11, and 12 are in contact, the surface layer near the needle electrode 11 is exposed to the light pulse for the duration of the irradiation.
If it is a P type, charges due to acceptors are excited, and if it is an N type, charges due to electrons are excited. Here, since the charge of the P-type acceptor is a positive charge, an electromotive force that tends to flow from the semiconductor 13 toward the needle electrode 11 is generated. Since the charge of electrons in the case of N type is negative, the needle-like electrode 11
An electromotive force is generated that tends to flow from the semiconductor 13 toward the semiconductor 13. Therefore, the polarities of the P-type output pulse and the N-type output pulse are reversed, and it is possible to distinguish between the P-type and the N-type. As explained above, according to the method of the present invention, three needle-like electrodes are used, and while a current is passed between the two needle-like electrodes, the points on the semiconductor surface that are in contact with the needle-like electrodes 10, 11, and 12 are Conventional method It is not necessary to wait until the electrodes are heated as in the case of the present invention, and the efficiency of the discrimination work is greatly improved, and highly reliable discrimination can be performed without being influenced by the semiconductor surface condition of the sample to be discriminated.

Further, according to the apparatus of the present invention, three needle-shaped electrodes are brought into contact with the semiconductor surface of the sample to be discriminated, and two of these needle-shaped electrodes are
A constant current power supply that supplies current between the needle-like electrodes, a light pulse generator that irradiates light pulses to the semiconductor surface area where the three needle-like electrodes are in contact, and two needle-like electrodes that carry current. Since it is equipped with a detector that detects the polarity of the pulse signal generated between one of the needle-like electrodes and the other needle-like electrode, it is possible to quickly distinguish between P-type and N-type semiconductors. Moreover, it can be carried out accurately, and by adding one needle electrode and providing other devices, it is possible to perform specific resistance measurement, lifetime measurement, etc.

Furthermore, by reducing the movement interval during measurement of the needle-shaped electrode, it is possible to investigate the P-type and N-type in minute portions of the semiconductor.

EXAMPLES The present invention will be explained in more detail below with reference to Examples and Comparative Examples.

A case will be described in which a silicon single crystal is used as the semiconductor of the sample to be determined.

First, the surface of a silicon single crystal was mechanically and chemically polished with an abrasive containing (alumina) to create a mirror surface (
Black 1), a sample (black 2) whose etched surface was chemically polished with an etching solution with a ratio of nitric acid: acetic acid: hydrofluoric acid = 6:3:1, and an abrasive material made of mesh 1200 alumina. A sample (black 3) that was polished to a lap surface,
Sample C flea 4) was prepared by cutting with a diamond cutter into a sliced surface.

) Also, tungsten carbide was used as the needle electrode.

The diameter of the needle is 0.5 mm, and the distance between each needle electrode is 1 m.
The m1 contact pressure was 200t. In addition, a constant current power source with a short circuit current value of (5 to 10 mA) was used. In addition, a light pulse generator using a xenon lamp as a light source was used. Further, as a detector, an oscilloscope with a maximum vertical sensitivity of 5 mv/Div and a frequency characteristic of 20 MHz was used.

Then, a current of 10 mA is passed from a constant current power supply between nine needle electrodes at both ends. A light pulse is irradiated onto the surface of the sample where the single needle electrodes 10, 11, and 12 are in contact, and the generated pulse signal is observed using an oscilloscope. The P-type and N-type were determined for each sample, and the results shown in the table below were obtained. P-type and N-type were also determined for each of the above samples using the conventional method (method using two needle electrodes and heating one of the electrodes) (comparative example), and the results are shown below. It is also listed in the table.

As is clear from the table, the method according to the present invention is not affected by the surface condition of the semiconductor and can always perform accurate discrimination.

Although the above example shows the case where silicon single crystals were used, similar results were obtained with germanium single crystals.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic diagrams for explaining the conventional method, and Figure 3 is a schematic diagram for explaining the conventional method.
The figure is a schematic diagram showing an embodiment of the present invention. Figures A to 2 in Figure 4 are diagrams showing waveforms, and Figure 4A is a waveform diagram of radio waves flowing between the needle electrodes 10 and 12. 1 is a waveform diagram of one optical pulse, C is a waveform diagram of a pulse signal in case of P type, and Figure 2 is a waveform diagram of a pulse signal in case of N type. 10, 11, 12...acicular electrode, 13...
...Semiconductor, 14... Constant current power supply, 15...
...Light pulse generator, 16...Detector, 1
7...Selection switch, 17a...17
A contact, 17b...B contact of 17, 18,1
9,20...Lead wire.

Claims (1)

[Claims] 1. In a method for distinguishing between P-type and N-type semiconductors, three needle-shaped electrodes are brought into contact with the semiconductor surface of a sample to be discriminated, and a current is applied between two of these needle-shaped electrodes. While the flow is flowing, a light pulse is irradiated to the part of the semiconductor surface that is in contact with the three needle-like electrodes, so that one of the two needle-like electrodes,
A method for determining whether a semiconductor is P-type or N-type, the method comprising determining whether the semiconductor is P-type or N-type based on the polarity of a pulse signal generated between it and one needle-like electrode through which no current is flowing. 2. Three needle-like electrodes that are brought into contact with the semiconductor surface of the sample to be determined, a constant current power source that supplies current between two of these needle-like electrodes, and a point on the semiconductor surface that the three needle-like electrodes have contacted. A light pulse generator that irradiates light pulses, one of the two needle-like electrodes that conducts current among the three needle-like electrodes,
1. A device for discriminating P-type and N-type semiconductors, comprising a detector for detecting the polarity of a pulse signal generated between one needle-like electrode through which no current flows.