JPH06112292A - Evaluation of silicon wafer - Google Patents

Abstract

PURPOSE:To provide an evaluation method of a silicon wafer able to simply estimate an initial oxide film withstand voltage good article ratio without changing a surface condition and a heat history of a silicon wafer. CONSTITUTION:The infrared scatterer density of a certain wafer is measured by an infrared ray scattering tomography method, further, an oxide film of a prescribed thickness and a large number of MOS capacitors having electrode of a prescribed area are manufactured on the wafer so as to measure an oxide film withstand voltage good article ratio, the interrelation between the infrared scatterer density and the initial oxide film withstand voltage good article ratio is clarified, the infrared scatterer density of a silicon wafer having an unknown initial oxide film withstand voltage good article ratio is measured and the interrelation is applied so as to estimate the initial oxide film withstand voltage good article ratio. Thereby, the infrared scatterer density can be measured by the complete non-destructive inspection thus allowing it to maintain an initial state relating to the surface state of an inspected silicon wafer and a heat history.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for estimating the rate of non-defective initial oxide film breakdown voltage of a silicon wafer in the quality evaluation of silicon wafers. The present invention relates to a method for evaluating a silicon wafer capable of realizing a nondestructive inspection by estimating the initial oxide film withstand rate of the silicon wafer from the above.

[0002]

2. Description of the Related Art The rate of good initial oxide film withstand voltage of silicon wafers is measured as follows. That is, when a large number of MOS capacitors having an oxide film of a predetermined thickness and electrodes of a predetermined area were produced on a silicon wafer and a voltage was applied to each MOS capacitor by a predetermined method, no dielectric breakdown occurred. The ratio of the number of MOS capacitors to the total number of MOS capacitors is defined as a good initial oxide film withstand voltage.

[0003]

Generally, a MOS capacitor generally has an LP-CV on an oxide film formed by thermal oxidation.
After the polycrystalline silicon film is formed by the D method, phosphorus is diffused and the polycrystalline silicon film is patterned by the photoetching method. As described above, manufacturing a MOS capacitor requires a lot of work. Further, the conventional method of manufacturing a MOS capacitor is a destructive inspection involving thermal oxidation and the like.

An object of the present invention is to provide a method for evaluating a silicon wafer which can easily estimate the initial oxide film breakdown voltage non-defective rate without changing the surface state and thermal history of the silicon wafer under the above circumstances. And

[0005]

Means for Solving the Problems The inventors have studied various methods for measuring defects in a silicon crystal. As a result, it was found that defects found in the as-grown state exist in the silicon crystal pulled by the CZ method. , High temperature stable defects observed by infrared scattering tomography as Secco pits for Secco etching, defects observed as flow patterns that disappear at high temperature, infrared scattering scattered in the ring OSF generation region After confirming that there are three types of defects, which are not observed by tomography but are observed as secopits, and further examined, defect density by infrared scattering tomography method (hereinafter referred to as infrared scatterer density) and MOS capacitor The distribution tendency of the defect density obtained from the initial oxide film breakdown voltage non-defective rate measured by manufacturing The inventors have completed the present invention by discovering that it is possible to estimate the initial oxide film withstand rate of silicon wafers from the infrared scatterer density of silicon wafers whose oxide film withstand rate is unknown did.

That is, according to the present invention, the infrared scatterer density of a silicon wafer whose initial oxide film breakdown voltage non-defective rate is unknown is used by using the correlation between the defect density and the initial oxide film breakdown voltage non-defective rate measured in advance by the infrared scattering tomography method. It is a method of evaluating a silicon wafer, characterized by estimating the initial oxide film breakdown voltage non-defective rate of the silicon wafer from the above.

Further, the present invention is a silicon wafer evaluation method characterized by using the Brewster's angle incidence method for the measurement of the infrared scattering tomography method in the above structure.

In the present invention, the infrared scattering tomography method is to observe infrared light from a vertical direction because when the infrared light is finely squeezed and made incident from the side surface of the sample, the light is scattered by defects contained in the crystal. The infrared scatterer density distribution can be obtained by synthesizing the slit-shaped scattered images and creating a cross-sectional image of the cross section scanned by the beam. Also,
In the above 90-degree scattering method, the wafer needs to be cleaved at the time of measurement, but if the measurement is performed at various rotation angles by the Brewster's angle incidence (illumination) method, the cleaving becomes unnecessary.

[0009]

The silicon wafer evaluation method according to the present invention is performed by first measuring the infrared scatterer density of the wafer by the infrared scattering tomography method using the same wafer or a wafer cut from the adjacent position of the single crystal ingot. In addition, a large number of MOS capacitors having an oxide film having a predetermined thickness and electrodes having a predetermined area are formed on a wafer, and the ratio of the number of MOS capacitors that did not cause dielectric breakdown to the total number of MOS capacitors is obtained to obtain an initial oxide film. By measuring the withstand voltage non-defective rate, the correlation between the infrared scatterer density and the initial oxide film withstand voltage non-defective rate is clarified. further,
The infrared scatterer density was measured using the infrared scatter tomography method for the wafer whose initial oxide film withstand rate was unknown.
The initial oxide film withstand voltage non-defective rate of the wafer is estimated using the above correlation.

As described above, the infrared scatterer density of a silicon wafer whose initial oxide film withstand rate is unknown is measured by using the infrared scattering tomography method, and the infrared scatterer density and the initial oxide film withstand rate are obtained in advance. The initial oxide film withstand voltage non-defective rate can be estimated by applying the correlation of Since the infrared scatterer density can be measured only by cleaving the wafer or without cleaving according to the Brewster's angle incidence method, according to the silicon wafer evaluation method of the present invention, a MOS capacitor can be manufactured. Without this, the initial oxide film withstand voltage non-defective rate can be easily estimated, and the wafer after the estimation can maintain the initial state regarding the surface state and the thermal history.

[0011]

[Example] Fifteen CZ-silicon wafers, which are expected to have different initial oxide film withstand rate, were prepared, and the oxide film thickness was 2
A MOS capacitor having an electrode area of 8 mm ² was fabricated on the wafer surface. SV to this MOS capacitor
Voltage was applied by the method, and a MOS capacitor that had a dielectric breakdown (12.5 μA / cm ² or more) under an electric field of 8 MV / cm or less was defective.
The ratio of the number of OS capacitors to the initial oxide film withstand voltage non-defective rate.

Next, the infrared scatterer density of the cleaved wafer after removing the MOS capacitor by etching was measured by the infrared scatter tomography method. FIG. 1 shows the relationship between the infrared scatterer density and the initial oxide film withstand voltage non-defective rate measured as described above. From FIG. 1, it is clear that the initial oxide film withstand voltage non-defective rate can be estimated by measuring the infrared scatterer density.

[0013]

According to the method for evaluating a silicon wafer according to the present invention, if a correlation diagram between the infrared scatterer density and the initial oxide film withstand rate is prepared in advance, the other wafers can be evaluated for the infrared scatterer density. The initial oxide film withstand voltage non-defective rate can be easily estimated simply by measuring.

The infrared scatterer density can be measured only by cleaving a silicon wafer by the infrared scatter tomography method, or by using the Brewster's angle incidence method, the cleaving is unnecessary and can be measured by a complete nondestructive inspection. The silicon wafer whose initial oxide film withstand rate has been estimated by the evaluation method has the advantage of being able to maintain the initial state regarding its surface state and thermal history.

[Brief description of drawings]

FIG. 1 is a graph showing the correlation between the infrared scatterer density of a CZ-silicon wafer and the initial oxide film withstand voltage non-defective rate.

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[Procedure amendment]

[Submission date] November 29, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

[0005]

Means for Solving the Problems The inventors have studied various methods for measuring defects in a silicon crystal. As a result, it was found that defects found in the as-grown state exist in the silicon crystal pulled by the CZ method. , defects disappear at a high temperature stability of the defect, the high temperature is observed as a flow pattern observed as peak Tsu bets infrared observed in scattered tomography seco (Secco) etching, distributed in a ring shape on the outer peripheral portion of the ring OSF occurrence region not observed in the infrared scattering tomography, to ensure that there are three kinds of defects of defects observed as pins Tsu DOO, further it was added examined, defect density (hereinafter infrared laser scattering tomography, infrared scatterer density It is known that the distribution tendency of the defect density obtained from the initial oxide film breakdown voltage non-defective rate measured after manufacturing the MOS capacitor is the same. And it can estimate the initial dielectric breakdown yield rate of the silicon wafers from the infrared scatterer density of gate oxide integrity yield rate unknown silicon wafer, and found that it is possible to be destructive inspection was completed this invention.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

In the present invention, the infrared scattering tomography method is to observe infrared light from a vertical direction because when the infrared light is finely squeezed and made incident from the side surface of the sample, the light is scattered by defects contained in the crystal. combines the scattering image to create cross-sectional images of the cross section scanned by the beam, it is possible to obtain an infrared scatterer density distribution. Also, the 90 ° scattering method described above it is necessary to cleave the wafer upon measurement, but cleavage is also unnecessary if Rihaka constant by the Brewster angle of incidence (illumination) method.

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Fujikawa 2201 Kamioda, Kohoku-cho, Kishima-gun, Saga Within Kyushu Denshi Metal Co., Ltd. Electronic Metals Co., Ltd. (72) Shinsuke Sadamitsu 2201, Kamioda, Kamikita-cho, Kijima-gun, Saga Prefecture Kyushu Electronic Metals Co., Ltd.

Claims (2)

[Claims] 1. A silicon wafer from an infrared scatterer density of a silicon wafer whose initial oxide film breakdown voltage non-defective rate is unknown by using a correlation between a defect density and an initial oxide film breakdown voltage non-defective rate measured by an infrared scattering tomography method which has been measured in advance. A method for evaluating a silicon wafer, which comprises estimating the initial oxide film withstand rate of non-defective products. 2. The method for evaluating a silicon wafer according to claim 1, wherein the Brewster's angle incidence method is used for the measurement of the infrared scattering tomography method.