JPH06283584A - Measuring method of lifetime of semiconductor wafer and its measuring equipment - Google Patents

Abstract

PURPOSE:To measure the lifetime inside a bulk of a semiconductor wafer, in a nondestructive manner free from pollution, and obtain distribution in the wafer surface concerning the lifetime measurement. CONSTITUTION:A silicon wafer 12 after carrier injection by using laser light irradiation is hold in a measurement chamber 11A filled with ozone supplied from an ozone generator 24. The life time of the silicon wafer 12 is measured by using, e.g. a reflection microwave method in an ozone atmosphere. The lifetime distribution in the surface of the silicon wafer 12 is obtained by repeating the measurement while moving the silicon wafer 12 with a stage controller 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a minority carrier lifetime measuring method and a measuring apparatus used for crystal evaluation of a semiconductor wafer.

[0002]

2. Description of the Related Art The lifetime value of a silicon wafer is not limited to the recombination due to defects inside the silicon wafer, but also the surface condition of the silicon wafer, such as surface defects.
It also changes due to pollution. Some of the carriers injected by the light pulse disappear due to recombination with these defects and contamination on the wafer surface. The speed at which carriers recombine on the wafer surface is called surface recombination speed.

Therefore, when the quality such as the amount of internal defects of a silicon wafer is evaluated in the state of a raw wafer, a pretreatment for suppressing the surface recombination rate is performed in measuring the lifetime. And after this pre-treatment,
For example, the lifetime of the wafer is measured by the reflection microwave method. Conventionally, the pretreatment is N
Process for applying a positive charge film to the surface of a P-type semiconductor wafer (PCC method), or process for applying a negative charge film to the surface of a P-type semiconductor wafer (N
CC method) and then forming a potential barrier in the vicinity of the surface of the semiconductor wafer to reduce the surface recombination velocity S of the semiconductor wafer.
A method of immersing the semiconductor wafer in the F solution to remove the native oxide film on the surface has been adopted.

However, in the above method of applying the charge film, since the surface of the wafer is contaminated, it is necessary to clean the wafer after the lifetime measurement. Particularly, in the NCC method of the P type, the wafer is dichromated. Since it must be boiled with a 1% sodium solution, dichromate ions adhere to the surface. The use of a solution containing chromium is not desirable because it may cause contamination of other cleaned wafers if the treatment is mistaken. In addition, in the method of removing the natural oxide film using the dilute HF solution, the lifetime value at the same location decreases due to the effect of the natural oxide film that grows with time after the treatment. Therefore, it is difficult to measure the fine in-plane distribution on the wafer surface because of the influence of the change over time. Therefore, there has been considered a method of irradiating the surface of the wafer with ultraviolet rays to measure the lifetime by non-contamination, non-contact, and non-damage. Eg 9
Irradiation with a W mercury lamp for 10 minutes.

[0005]

However, such a conventional pretreatment for suppressing the surface recombination rate by irradiation with ultraviolet rays is to suppress the surface recombination rate within a short period of time, for example, several tens of seconds after the irradiation with ultraviolet rays. However, there is a problem that the in-plane distribution cannot be measured for measuring the lifetime of the wafer surface.

Therefore, the inventor found that the effect of suppressing the surface recombination does not occur in the nitrogen atmosphere even when the surface of the semiconductor wafer is irradiated with ultraviolet rays, and eventually the surface recombination rate is suppressed by the influence of ozone. I found out that there is.

[0007]

In a method for measuring a lifetime of a semiconductor wafer according to claim 1, the step of injecting a carrier into the semiconductor wafer and the lifetime of the semiconductor wafer after the carrier injection are measured in an ozone atmosphere. And a step of performing.

In a semiconductor wafer lifetime measuring apparatus according to a second aspect of the present invention, a chamber in which the semiconductor wafer is held, carrier injection means for injecting carriers into the semiconductor wafer, and ozone are supplied into the chamber. The ozone supply means and the measuring means for measuring the lifetime of the semiconductor wafer in this chamber are provided.

[0009]

In the method for measuring the lifetime of the semiconductor wafer according to the invention described in claim 1, in the ozone atmosphere,
After carrier injection, the lifetime of the semiconductor wafer is measured by, for example, the reflection microwave method. As a result, the recombination rate on the surface of the semiconductor wafer is reduced by ozone, and the bulk lifetime of the semiconductor wafer can be measured. Further, the lifetime can be measured at a plurality of positions on the surface of the semiconductor wafer, and the in-plane distribution of the lifetime of the semiconductor wafer can be measured. In addition to the reflection microwave method, the lifetime can also be measured by, for example, the capacitance probe method, the coaxial cable method, the strip line method, the additive eddy current method, or the like.

Further, in the semiconductor wafer lifetime measuring apparatus according to the second aspect of the present invention, the inside of the chamber can be kept in an ozone atmosphere, and the surface of the wafer is measured during the lifetime measurement of the semiconductor wafer. The recombination rate can continue to be suppressed.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing a schematic configuration of a semiconductor wafer lifetime measuring apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing a semiconductor wafer lifetime measuring apparatus according to an embodiment of the present invention.

In these figures, reference numeral 11 denotes a chamber in which a silicon wafer 12 is loaded and held, and the internal sealed space of this chamber 11 is partitioned by a shutter 13 into a measurement chamber 11A and a loading chamber 11B. ing. The silicon wafer 12 is placed and held on the holding table 14 in the loading chamber 11B by, for example, a chuck mechanism or the like. The holding table 14 is configured to be movable to the measurement chamber 11A by the transport mechanism 15.

The holding table 1 is provided in the measuring chamber 11A.
4 is provided with a stage controller 16. Further, a laser beam irradiation means 17 for injecting carriers into the silicon wafer 12 placed on the holding table 14 is provided. At the same time, microwaves are radiated to the silicon wafer 12 from the Gunn diode 19 via the waveguide 18. 20 is a circulator for microwaves, 2
Reference numeral 1 is a microwave detector. Furthermore, this detector 2
The detection signal from 1 is sent to the data analysis and display unit 22, and after the data analysis and display, this data is input to the host computer 23. The host computer 23 controls the stage controller 16 and the like to perform the next measurement.

Further, in the measuring apparatus having such a structure, an ozone generator 24 for supplying ozone to the measuring chamber 11A is attached. The ozone generator 24 constitutes ozone supply means for supplying ozone into the chamber 11.

In the lifetime measuring apparatus having the above structure, first, the silicon wafer 12 to be measured is measured.
Is placed on the holding table 14 in the charging chamber 11B. Then, the holding table 14 is moved to the measurement chamber 1 by the transport mechanism 15.
Transferred to 1A. At this time, the shutter 13 is opened and closed while the chamber 11 is sealed. With respect to the silicon wafer 12 on the holding table 14 positioned at a predetermined position by the stage controller 16,
The laser beam irradiation means 17 irradiates a laser beam having a predetermined wavelength, for example, 904 nm to inject carriers. At this time, ozone O ₃ is supplied from the ozone generator 24 into the measurement chamber 11A. Therefore, the silicon wafer 12 being measured
The surface is exposed to the ozone atmosphere. Then, by driving the Gunn diode 19, for example, 9.6 GHz
Of microwaves is applied to the surface of the silicon wafer 12. Then, the reflected wave is measured by the detector 21.
In this way, the lifetime of the silicon wafer 12 is measured in the ozone atmosphere.

When the measurement at one location is completed in this way, the measured data is sent to the host computer 24.
Is held, the silicon wafer 12 is moved in the horizontal direction via the stage controller 16, and the same procedure as described above is repeated to measure the lifetime at that position. By repeating the measurement in the ozone atmosphere while changing the measurement point in this way, the in-plane distribution of the lifetime of the silicon wafer 12 can be measured. The in-plane distribution may be displayed on the display unit 23.

[0017]

According to the present invention, the lifetime inside the bulk of a semiconductor wafer can be measured nondestructively and without contamination. In addition, it is possible to obtain the in-plane distribution regarding the measurement of the lifetime of the semiconductor wafer.

[Brief description of drawings]

FIG. 1 is a plan view showing a schematic configuration of a semiconductor wafer lifetime measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a semiconductor wafer lifetime measuring apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 11 Chamber 11A Measuring Room 12 Silicon Wafer 17 Laser Light Irradiating Means 19 Gunn Diode 21 Detector 24 Ozone Generator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Etsuro Morita 1-297, Kitabukuro-cho, Omiya-shi, Saitama Mitsubishi Materials Corporation Central Research Laboratory (72) Inventor Takayuki Shingouchi 297-chome, Kitabukuro-cho, Omiya-shi, Saitama Mitsubishi Central Research Laboratory, Materials Co., Ltd.

Claims (2)

[Claims] 1. A method for measuring a lifetime of a semiconductor wafer, comprising: a step of injecting a carrier into the semiconductor wafer; and a step of measuring a lifetime of the semiconductor wafer after the carrier injection in an ozone atmosphere. 2. A chamber for holding a semiconductor wafer, carrier injection means for injecting carriers into the semiconductor wafer, ozone supply means for supplying ozone into the chamber, and lifetime of the semiconductor wafer in the chamber. A semiconductor wafer lifetime measuring apparatus comprising: a measuring unit for measuring.