JPS60100449A - Semiconductor measuring device - Google Patents

Abstract

PURPOSE:To obtain a simple and inexpensive device for measuring the lifetime of minority carrier in a silicon wafer in noncontact by detecting the photovoltaic power produced upon emitting of a light by the variation in a potential by the capacitive coupling of a transparent electrode with the silicon wafer. CONSTITUTION:A light emitting diode 3 emits a light in the order of sequentially generating the light from the end of an optical fiber 4 opposed to a silicon wafer 1 in a direction parallel to the paper surface, thereby performing the primary scanning. The fiber 4 emits the wafer 1 as a spot light source to generate an electromotive force in an ultrafine region. The light is AC-modulated, and even if a transparent electrode 5 is separated from the wafer 1, the electromotive force is externally produced readily by the capacitive coupling. When the phase difference between the voltage of a power source 8 and a signal voltage is measured by a phase detector, the value of the lifetime of the minority carrier in the wafer can be measured in noncontact.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a semiconductor measuring device, and more particularly to a device for measuring the concentration of minority carriers in silicon.

[Background of the invention]

Conventionally, the lifetime of minority carriers in semiconductors has been determined by attaching electrodes with ohmic contact to a silicon wafer, irradiating them with impulses of xenon lamp light, and measuring the attenuation of the output signal (JIS Standard 1). -IO
604, 1978). This method is a contact method and is suitable only for sampling inspections. Also, measurements cannot be performed on-line.

On the other hand, as a non-contact measurement method, there is a method in which carriers are injected by irradiating light, microwaves are further applied, and the lifetime of minority carriers is determined from the temporal response of absorption. However, this method has the disadvantage that it requires expensive and complicated microwave transmitters, receivers, etc., making the entire device wasteful and expensive.

[Purpose of the invention]

It is therefore an object of the present invention to provide a simple and inexpensive semiconductor measuring device for measuring the lifetime of minority carriers in silicon wafers in a non-contact manner.

[Summary of the invention]

In order to achieve the above object, a semiconductor measuring device according to the present invention includes a method for placing a silicon wafer to be measured.
a pedestal serving as one electrode; a transparent electrode provided on the silicon wafer placed on the pedestal so as to be capacitively coupled thereto; and one end connected to the silicon wafer through the transparent electrode. a plurality of optical fibers provided to face each other, a light emitting diode provided at the other end of the plurality of optical fibers, and a control circuit for sequentially causing the light emitting diodes to emit light in a predetermined order;
and a detector for detecting the potential generated in the transparent electrode, and the gist is to detect the change in potential due to the capacitive coupling of the transparent electrode with the silicon wafer, and the photovoltaic force generated due to light irradiation. do.

According to the present invention, changes in potential are captured in a non-contact manner and spot irradiation is performed using an optical fiber, so that the lifetime of minority carriers can be measured as a distribution. Furthermore, since a light emitting diode is used as a light source, light can be easily modulated by an electronic circuit, and the optimum modulation frequency for the measurement system can be freely selected. Furthermore, since the light source made of light emitting diodes is small and has a fast response, an electronic switch can be used to sequentially switch a large number of light emitting diodes.
can be scanned, and the distribution of lifetimes can be shortened to li, ′l, I
It can be done easily and extremely easily.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in more detail using examples with reference to the accompanying drawings, but these are merely illustrative.
It goes without saying that various modifications and improvements can be made without going beyond the scope of the present invention.6 In Figure 1, the silicon wafer 1 is mechanically moved in the direction perpendicular to the plane of the paper, and the silicon wafer 1 is moved parallel to the plane of the paper. FIG. 2 is a block diagram showing the configuration of a semiconductor measuring device according to the present invention, which performs one scan by arranging an optical fiber in the same direction. The movable frame 2 is made of metal,
It also serves as a ground electrode, and the silicon wafer l is fixed onto this using a vacuum chuck. One end of the optical fiber 4 is provided to face the light emitting diode 3. The other end of the optical fiber 4 forms an array on which In, 03
A transparent electrode 5 made of a Nesa film such as the above is provided.

The light emitting diodes 3 are sequentially caused to emit light in a predetermined order via a control circuit 9 from a power source 8, and a change in photovoltaic force caused by the light irradiation is detected by a preamplifier 6 and a phase detector 7.

The operation of the semiconductor measuring device according to the present invention is performed as follows. The control circuit 9 causes the light emitting diode 3 to
Light is emitted from the end of the optical fiber 4 facing the silicon wafer 1 in an order in which the light is generated successively in a direction parallel to the plane of the paper, and in this way, -dimensional scanning is performed. The optical fiber 4 serves as a point light source that irradiates the silicon wafer 1 and generates an electromotive force in a minute area. The light is alternating current modulated, and even if the transparent electrode 5 is away from the silicon wafer 1, the electromotive force can be easily extracted to the outside by capacitive coupling. By measuring the phase difference between the voltage of the power source 8 and the signal voltage with a phase detector, the value of the minority carriers in the silicon wafer can be measured without contact.

The pedestal 2 is moved in the direction iTi,ll'l on the plane of the paper, and two-dimensional scanning is performed in addition to electrical one-dimensional scanning.

FIG. 2 shows an embodiment in which the ends of the optical fibers facing the silicon wafer are arranged in a mosaic pattern, eliminating mechanical scanning. In this example,
Since all scanning is done by electrox, the device is simple and inexpensive to construct.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain a simple and inexpensive semiconductor measuring device that non-contactly identifies the lifetime of minority carriers in a silicon wafer.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a semiconductor measuring device according to an embodiment of the present invention. FIG. 2 is a block diagram showing the structure of a semiconductor measuring device according to an embodiment of the present invention, and FIG. FIG. 1... Silicon wafer 2... Mount 3... Light emitting diode 4... Optical fiber 5... Transparent electrode 6... Preamplifier 7... Phase detector 8... Power supply 9. ... Control circuit agent patent attorney Junnosuke Nakamura? 1 Figure? '2 tol

Claims (1)

[Claims] A pedestal serving as one electrode on which a silicon wafer to be measured is placed, a transparent electrode provided on the silicon wafer placed on the pedestal so as to be capacitively coupled thereto, and one end. a plurality of optical fibers provided to face the silicon wafer through the transparent electrodes, a light emitting diode provided at the other end of the plurality of optical fibers, and the light emitting diodes in a predetermined order. A semiconductor measuring device for measuring the lifetime of minority carriers in a silicon wafer, comprising a control circuit for sequentially emitting light according to the following, and a detector for detecting the potential of the transparent electrode.